Orthodontic treatment of impacted teeth [3. ed] 9781444336757, 1444336754

Table of contents :
General principles related to the diagnosis and treatment of impacted teeth --
Radiographic methods related to the diagnosis of impacted teeth --
Surgical exposure of impacted teeth --
Treatment components and strategy --
Maxillary central incisors --
Palatally impacted canines --
Impacted teeth and resorption of the roots of adjacent teeth --
Other single teeth --
Impacted teeth in the adult patient --
Lingual appliances, implants, and impacted teeth --
Rescuing teeth impacted in dentigerous cysts --
The anatomy of failure --
Traumatic impaction --
Cleidocranial dysplasia --
Extreme impactions, unusual phenomena, and difficult decisions.

Citation preview

Orthodontic Treatment of Impacted Teeth

To my wife Sheila, to our children and grandchildren, and to the memories of our parents and my sister.

Orthodontic Treatment of Impacted Teeth Third Edition

Adrian Becker BDS, LDS RCS, DDO RCPS Clinical Associate Professor Emeritus Department of Orthodontics Hebrew University–Hadassah School of Dental Medicine Jerusalem Israel

A John Wiley & Sons, Ltd., Publication

This edition first published 2012 © 2012 by Adrian Becker First published in 1998 by Martin Dunitz and in 2007 by Informa UK Ltd Wiley-Blackwell is an imprint of John Wiley & Sons, formed by the merger of Wiley’s global Scientific, Technical and Medical business with Blackwell Publishing. Registered office: John Wiley & Sons, Ltd, The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK Editorial offices: 9600 Garsington Road, Oxford, OX4 2DQ, UK The Atrium, Southern Gate, Chichester, West Sussex, PO19 8SQ, UK 2121 State Avenue, Ames, Iowa 50014-8300, USA For details of our global editorial offices, for customer services and for information about how to apply for permission to reuse the copyright material in this book please see our website at www.wiley.com/wiley-blackwell. The right of the author to be identified as the author of this work has been asserted in accordance with the UK Copyright, Designs and Patents Act 1988. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Library of Congress Cataloging-in-Publication Data Becker, Adrian.   Orthodontic treatment of impacted teeth / Adrian Becker. – 3rd ed.     p. ; cm.   Includes bibliographical references and index.   ISBN-13: 978-1-4443-3675-7 (hard cover : alk. paper)   ISBN-10: 1-4443-3675-4 (hard cover : alk. paper)   I.  Title.   [DNLM:  1.  Tooth, Impacted–surgery.  2.  Orthodontics, Corrective–methods. WU 101.5]   LC classification not assigned   617.6'43–dc23 2011034239 A catalogue record for this book is available from the British Library. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. Set in 10/12 pt Minion by Toppan Best-set Premedia Limited, Hong Kong

1  2012

Contents Preface to the First Edition Preface to the Second Edition Preface to the Third Edition

  1   2   3   4   5   6   7   8   9 10 11 12 13 14 15 Index

General Principles Related to the Diagnosis and Treatment of Impacted Teeth Radiographic Methods Related to the Diagnosis of Impacted Teeth Surgical Exposure of Impacted Teeth Treatment Components and Strategy Maxillary Central Incisors Palatally Impacted Canines Impacted Teeth and Resorption of the Roots of Adjacent Teeth Other Single Teeth Impacted Teeth in the Adult Patient Lingual Appliances, Implants and Impacted Teeth Rescuing Teeth Impacted in Dentigerous Cysts The Anatomy of Failure Traumatic Impaction Cleidocranial Dysplasia Extreme Impactions, Unusual Phenomena and Difficult Decisions

vi viii x

1 10 29 55 70 110 173 211 262 283 293 319 357 370 406 437

Preface to the First Edition There can be little question that the treatment of impacted teeth has caught the imagination of many in the dental profession. The challenge has, over the years, been taken up by the general practitioner and by a number of dental specialists, including the paedodontist, the periodontist, the orthodontist and, most of all, the oral and maxillofacial surgeon. Each of these professionals has much ‘input’ to offer in the resolution of the immediate problem and each is able to show some fine results. However, no single individual on this specialist list can completely and successfully treat more than a few of these cases without the assistance of one or more of others of his/her colleagues on that list. Thus, the type of treatment prescribed may depend upon which of these dental specialists sees the patient first and the level of his/her experience with the problem in his/ her field. Such treatment may involve surgical exposure and packing, orthodontic space opening, perhaps autotransplantation, or a surgical dento-alveolar set-down procedure, or even just an abnormally angulated prosthetic crown reconstruction. Experience has come to show that the orthodontic/surgical modality has the potential to achieve the most satisfactory results in the long term. Despite this, many orthodontists have ignored or abrogated their responsibility towards the subject of impacted teeth to others, accounting for the popularity of other modalities of treatment. The subject has become something of a Cinderella of dentistry. Within the orthodontic/surgical modality, much room exists for debate as to what should be done first and to what lengths each of the two specialties represented should go in the zealous pursuit of its allotted portion of the procedure. The literature offers scant information and guidance to resolve these issues, leaving the practitioner to fend for him/ herself, with a problem that has ramifications in several different specialist realms. This book discusses the many aspects of impacted teeth, including their prevalence, aetiology, diagnosis, treatment timing, treatment and prognosis. Since these aspects differ between incisors and canines, and between these and the other teeth, a separate chapter is devoted to each. The material presented is based on the findings of clinical research that has been carried out in Jerusalem by a small group of clinicians over the past 15 years or so, at the Hebrew University – Hadassah School of Dental Medicine, founded by the Alpha Omega Fraternity and from the gleanings of clinical experience in the treatment of many hundreds of my patients, young and old. An overall and recommended approach to the treatment of impacted teeth is presented and emphasis is placed on

the periodontal prognosis of the results. Among the many other aspects of this book, the intention has been to propose ideas and principles that may be used to resolve even the most difficult impaction, employing orthodontic auxiliaries of many different types and designs. None of these is specific to any particular orthodontic appliance system or treatment ‘philosophy’, notwithstanding the author’s own personal preferences, which will become obvious from many of the illustrations. These auxiliaries may be used with equal facility in virtually any appliance system with which the reader may be fluent. The only limitation in the use of these ideas and principles are those imposed on the reader by his/her own imagination and willingness to adapt. The orthodontic manufacturers’ catalogues are replete with the more commonly and routinely used attachments, archwires and auxiliaries, which are offered to the profession with the aim of streamlining the busy practice. These items have not been tailored to the demands of the clinical issues that are raised in this book. These issues, by their very nature, are exceptional, problematic and often unique, while occurring alongside and in addition to the routine. Among the more common limitations self-imposed by many orthodontists has been the disturbing trend to rely so completely upon the use of preformed and pre-welded attachments that they have forgotten the arts of welding and soldering and no longer carry the necessary modest equipment. This then restricts one’s practice to using only what is available and sufficiently commonly used to make it commercially worthwhile for the manufacturer to produce. By consenting to this unhealthy situation, the orthodontist is agreeing to work with ‘one hand tied behind his/her back’ and treatment results with inevitably suffer. I acknowledge and am grateful for the help given me by several colleagues in the preparation of this book. An excellent professional relationship has been established, and has withstood the test of time, with two senior members of the Department of Oral and Maxillofacial Surgery at Hadassah, with whom a modus operandi has been developed, in the treatment of our patients. Professor Arye Shteyer, Head of the Department, and, subsequently, Professor Joshua Lustmann have educated me in the finer points of surgical procedure and care while, at the same time, have demonstrated a respect and understanding of the needs of the orthodontist at the time of surgery. I am grateful to them for their collaboration in the writing of Chapter 3. Dr Ilana Brin read the original manuscript and made some useful suggestions, which have been included in the text. I am grateful to Dr Alexander Vardimon for his comments regarding the use of magnets and to Dr Tom

Preface to the First Edition  vii  Weinberger for the discussions that we have had regarding several issues realised in the book. My wife, Sheila, read the earlier drafts and made many important recommendations and corrections. More than anyone else, she encouraged me to keep writing during the many months when other and more pressing responsibilities could have been used as justifiable excuses for putting the project aside. My colleagues Dr Monica Barzel, Dr Yocheved ben Bassat, Dr Gabi Engel, Dr Doron Harary, Dr Tom Weinberger and Professor Yerucham Zilberman, and my former graduate students Dr Yossi Abed, Dr Dror Eisenbud, Dr Sylvia Geron, Dr Immanuel Gillis, Dr Raffi Romano and Dr Nir Shpack, have provided me with several of the illustrations included here and I am indebted to them. I am grateful, too, to Ms Alison Campbell, Commissioning Editor at Martin Dunitz Publishers and to Dr Joanna Battagel, Technical Editor, for their constructive and professional critique of the manuscript, which contributed so much to its ultimate format. I also thank Naomi and Dudley Rogg, of the British Hernia Centre, for the computer and office facilities that they placed at my disposal during my short sabbatical in London in the latter stages of the preparation of the work for publication. Permission to use illustrations from my own articles that were published in various learned journals was granted by the publishers of those journals or by the owners of the copyright, as follows:

Figure 5.13 was reprinted from Pertz B, Becker A, Chosak A, The repositioning of a traumatically-intruded mature rooted permanent incisor with a removable appliance. J. Pedodont 1982; 6: 343−354, with kind permission of the Journal of Pedodontics Inc. Figure 5.4 and 5.12 were reprinted from Becker A, Stern N, Zelcer Z, Utilization of a dilacerated incisor tooth as its own space maintainer. J Dent 1976; 4: 263–264, with kind permission from Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington OX5 1GB, UK. Figures 9.8−9.14 were reprinted from Becker A, Shteyer, A, Bimstein, E, Lustmann, J, Cleidocranial dysplasia: part 2 − a Treatment Protocol for the Orthodontic and Surgical Modality, Am J Orthod Dentofac Orthop 1997; 111: 173−183, with kind permission of Mosby-Year Book Inc., St Louis, MO, USA. Figure 6.35 was reprinted from Kornhauser, S, Abed, Y, Harary, D, Becker, A, The resolution of palatally-impacted canines using palatalocclusal force from a buccal auxiliary, Am J Orthod Dentofac Orthop 1996; 110: 528−534, with kind permission of Mosby-Year Book Inc., St Louis, MO, USA. I am very thankful for their cooperation and for their agreement. Adrian Becker Jerusalem

Preface to the Second Edition In the nine years that have elapsed since the publication of the first edition of this book, much has changed in the field of orthodontics in general and, perhaps even more so, as it relates to the treatment of impacted teeth. The advances in imaging, particularly cone beam computerized tomography, have made accurate positional diagnosis of an impacted tooth virtually foolproof, enabling the application of appropriately directed traction to resolve even the most difficult cases. Temporary orthodontic implants have provided the opportunity to resolve the impaction, in many cases without the need for an orthodontic appliance and before orthopaedic treatment per se is begun. They have opened up a whole new area to exploit for mechanotherapeutic solutions to many of the problems we face. The first edition was based on the findings of clinical research that was carried out over a long period of time in Jerusalem during the 1980s and 1990s. In much the same way, this second edition documents the findings of ongoing and evidence-based studies carried out by largely the same small group of clinical investigators, since then. Most of these published articles were the product of an excellent working collaboration with Dr Stella Chaushu, a former student of mine and now Senior Lecturer in the Department of Orthodontics. Her industrious and intellectual qualities have contributed to the output of a large number of valuable published studies in just a few short years. Under the leadership of Professor Refael Zeltser, chairperson of the Department of Oral and Maxillo-facial Surgery at the Hebrew University – Hadassah School of Dental Medicine in Jerusalem, a whole generation of young surgeons has grown up who exhibit the ability to appreciate and value the finer points of cooperation with the orthodontist. Dr Eran Regev and Dr Nardi Casap in Jerusalem, Dr Gavriel Chaushu, the chairperson at the parallel department of the Sourasky Hospital in Tel Aviv, and Dr Harvey Samen in private practice, have worked closely with me in the treatment of our patients. Many of these cases are illustrated in the pages of this book. I derive considerable satisfaction from seeing the surgical expertise learned from and handed down by Professors Arye Shteyer and Joshua Lustmann being practised by these highly professional colleagues, on a day-by-day basis. Their awareness and perception of the significance of their work in determining the long-term outcome have helped me to aim for the highest quality results and the well-being of the patient. They deserve my gratitude. In the preparation of this book, I have called upon and am grateful for the expertise of a small number of people, who have provided me with authoritative and essential

information that has permitted me to make the text more comprehensive and more complete. In particular, I mention Dr James Mah and Dr David Hatcher in California, with regard to cone beam CT imaging and Dr Joe Noar in London, with regard to the use of magnets. I have given and continue to give courses and lectures on the subject of impacted teeth in many places all over the world which, in the past few years, have been presented in collaboration with Dr Stella Chaushu. It is at these meetings that I come across some of the most interesting and rare material. I am indebted to several individual members of these audiences who frequently approach us during a coffee break, radiograph in hand, with some truly remarkable conditions, several of which have been included in this book, together with appropriate recognition. My colleagues in the Orthodontic Department in Jerusalem have often become the sounding board for many of the ideas that are presented herein and I am thankful to them for the discussions that we have had. I appreciate their taking the stand of devil’s advocate in these situations, forcing me to justify or to discard. Nevertheless, none of this would ever have been published had I not spent so many years teaching the students on our postgraduate orthodontics specialty course. These future orthodontic standard bearers are privileged to learn from the various individual teaching preferences of mentors who rely on years of experience in practice, particularly when it comes to this bracket or that, this treatment philosophy or that and this orthodontic guru or that. Additionally, they have learned to look for and even demand clinical ideas and treatment policies that have a proven evidence-based, track record to commend them and to justify their use. I know of no other postgraduate orthodontic course, worldwide, in which the subject of impacted teeth is explicitly taught in a comprehensive and integrative manner, including a designated weekly clinical session. It was this more than any other factor which encouraged me to embark on this mammoth task. The future of our profession and the long-term superior care of the even younger generation of our patients is in the hands of these aspiring orthodontists. I am grateful to them for having, perhaps unwittingly, cajoled me into writing this text. I hope that it will be a source of information for them as they undertake the challenge of some of the more difficult, unconventional and unusual cases that they will inevitably come across in practice and for which they will be expected to find appropriate therapeutic answers. I wish to thank the following publishers of two articles, as follows:

Preface to the Second Edition  ix  Several of the illustrations comprising Figure 7.8 were reprinted from the World Journal of Orthodontics. Vol. 5. The Role of Digital Volume Tomography in the Imaging of Impacted Teeth, by Adrian Becker and Stella Chaushu. 2004. with permission from Quintessence Publishing Co, Inc. Several of the illustrations comprising Figure 11.9 were reprinted from Healthy periodontium with bone and soft tissue regeneration following orthodontic-surgical retrieval of teeth impacted within cysts, by Adrian Becker & Stella

Chaushu, in Biological Mechanisms of Tooth Movement and Craniofacial Adaptation. Proceedings of the Fourth International Conference, 2004, pp. 155−162. Z Davidovitch and J Mah, editors. Sponsored by the Harvard Society for the Advancement of Orthodontics. Reproduced with permission. Adrian Becker Jerusalem, Israel

Preface to the Third Edition Only 14 years have passed since the publication of the first edition of this book and much has changed in orthodontics, in general and in the context of the treatment of impacted teeth, in particular. The subject material that appeared in that small monograph has developed several fold, in the light of research and the advent of new technology. These two factors have encouraged the orthodontic specialist to be more discerning in the diagnosis of pathology and more innovative and resourceful in the application of directional traction. Mistaken positional diagnosis and surgical blunders have become less common and consequent failure to resolve the impaction less frequent. At the same time, they have permitted the orthodontist to become more adventurous and to successfully apply his/her knowledge and experience to the treatment of cases where previously the tooth would have been scheduled for extraction. If this third edition may yet contribute to the furtherance of this favorable trend in any way, I will consider that my mission will have been accomplished. It was the aim in each of the earlier editions of this book to present reasoned principles of treatment for tooth impaction, illustrated by examples from real life. Following these principles to their logical conclusion, Chapter 15 has been added in the present edition to illustrate how some extreme examples or cases with concurrent complicating factors may be resolved, several of which involve the expertise of colleagues in our sister specialties. Oddities, such as the “banana” third molar, with its impacting influence on its immediate neighbor, are also new to this edition. Failure has intrigued me for a long time and, while Chapter 12 was new to the second edition, it has been enlarged now in the third. The recognition and importance of invasive cervical root resorption (ICRR) as a cause of failure to resolve an affected impacted tooth seems to be hardly known within the profession. There is a section added herein which discusses the etiology of this pathological entity, its disease process, its potency as a factor for failure and speculates on accepted standard procedures that may predispose to its occurrence.

To write a textbook or to update an edition may take several years. Once it is finished, it has to go through the many months of the publishing process, with questions and corrections, proofreading and amendments. In the meantime, what was written becomes progressively obsolete – new ideas are put forward in the journals, some are disciplined studies and others just innovative clinical methods learned in the very singular one-on-one situation in the orthodontic operatory between orthodontist and patient. In order to provide at least a partial answer to this, I have set up an internet website at www.dr-adrianbecker. com, in which regular updates on clinical research and technique, vignettes describing individual conditions or just a customized approach to the treatment of a specific case, are published with the aim of complementing the book. The site also features a “troubleshooting impacted teeth” page for individual clinical consultations – open to anyone, whether orthodontist, patient or concerned parent. Details of the patient and his/her condition will need to be filled in and existing radiographs, CBCT and other relevant information uploaded. A report is returned to the sender within a few days with suggestions and recommendations for treatment. The clinical research on which this text is largely based has been the product of long-term cooperation with Professor Stella Chaushu, PhD, DMD, MSc, Chairperson of the Orthodontic Department in Jerusalem, to whom are due my special thanks. I am grateful to my co-authors who have advised me in my writing of several of the chapters herein and to a number of my colleagues who have sent me illustrative material which I have included, with their permission. I would also like to recognize Mr. Israel Vider, director of the Dent-Or Imaging Center in Jerusalem, for his CT imaging expertise, his assistance in granting me access to his technical laboratory and for his work on several of the illustrations that are published in this edition. Adrian Becker Jerusalem, October 2011

1 General Principles Related to the Diagnosis and Treatment of Impacted Teeth

Dental age

2

Assessing dental age

3

When is a tooth considered to be impacted?

5

Impacted teeth and local space loss

6

Whose problem?

6

The timing of the surgical intervention

8

Patient motivation and the orthodontic option

8

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

2  Orthodontic Treatment of Impacted Teeth In order for us to understand what an impacted tooth is and whether and when it should be treated, it is necessary first to define our perception of normal development of the dentition as a whole and the time-frame within which it operates.

Dental age A patient’s growth and development may be faster or slower than average and we may assess his age in line with this development [1]. Thus, a child may be tall for his age, so that his morphological age may be considered to be advanced. By studying radiographs of the progress of ossification of the epiphyseal cartilages of the bones in the hands of a young patient (the carpal index) and comparing this with average data values for children of his age, we are in a position to assess the child’s skeletal age. Similarly, there is a sexual age assessment related to the appearance of primary and secondary sexual features, a mental age assessment (intelligence quotient, or IQ, tests), an assessment for behaviour and another to measure the child’s self-concept. These indices are used to complement the chronological age, which is calculated directly from the child’s birth date, to give further information regarding a particular child’s growth and development. Dental age is another of these parameters, and it is a particularly relevant and important assessment, used in advising proper orthodontic treatment timing. Schour and Massler [2], Moorrees et al. [3, 4], Nolla [5], Demerjian et al. [6] and Koyoumdjisky-Kaye et al. [7] have drawn up tables and diagrammatic charts of stages of development of the teeth, from initiation of the calcification process through to the completion of the root apex of each of the teeth, together with the average chronological ages at which each stage occurs. Eruption of each of the various groups of teeth is expected at a particular time, but this may be influenced by local factors, which may cause premature or delayed eruption with a wide time-span discrepancy. For this reason, eruption time is an unreliable method of assessing dental age. With few exceptions, mainly related to frank pathology, root development proceeds in a fairly constant manner usually regardless of tooth eruption or the fate of the deciduous predecessor. It therefore follows that the use of tooth development as the basis for dental age assessment, as determined by an examination of periapical or panoramic X-rays, is a far more accurate tool. Thus, we may find that a child of 11–12 years of age has four erupted first permanent molars and all the permanent incisors only, with deciduous canines and molars completing the erupted dentition. If the practitioner were merely to run to the eruption chart, he would note that at this age all the permanent canines and premolars should have erupted, and he would conclude that the 12 deciduous teeth have been retained beyond their due time. The treatment

that would then appear to be the logical follow-up of this observation requires the extraction of these 12 deciduous teeth! However, there are two possibilities in this situation and, in order to prevent unnecessary harm being inflicted on the child and his parents, the radiographs must be carefully studied to distinguish one context from the other. In the event that the radiographs show the unerupted permanent canines and premolars having completed most of their expected root length, then the child’s dental age corresponds with his chronological age (Figure 1.1). The deciduous teeth have not shed naturally, due to insufficient resorption of their roots. As such, we have to presume that they are the impediment to the normal eruption of the permanent teeth. Their permanent successors may then strictly be defined as having delayed eruption. Under these circumstances it would be logical to extract the deciduous teeth on the grounds that their continued presence defines them as over-retained. The second possibility is that the radiographs reveal relatively little root development, more closely corresponding, perhaps, to the picture of the 9-year-old child on the tooth development chart (Figure 1.2). The child’s birth certificate

Fig. 1.1  Advanced root development of the canines and premolars in a 10-year-old child defines these teeth as exhibiting delayed eruption. The overall dental age is 12–13 years, with very late developing second permanent molars, particularly on the mandibular right side.

Fig. 1.2  A 12-year-old patient with root development defining dental age as 9 years. Extraction of deciduous teeth is contraindicated.

General Principles Related to the Diagnosis and Treatment of Impacted Teeth  3  may indicate that he is 12 years of age, and this may well be supported by his body size and development, and by his intelligence. Nevertheless, his dentition is that of a child three years younger, determining his dental age as 9 years and diagnosing a late-developing dentition. Extraction in these circumstances would be the wrong line of treatment, since it is to be expected that these teeth will shed normally at the appropriate dental age and early extraction may lead to the undesired sequelae characteristic of early extraction, performed for any other reason. From this discussion, we are now in a position to define the terms that we shall use throughout this text. The first refers to a retained deciduous tooth, which has a positive connotation and which may be defined as a tooth that remains in place beyond its normal, chronological shedding time due to the absence or retarded development of the permanent successor. By contrast and with a negative connotation, an over-retained deciduous tooth is one whose unerupted permanent successor exhibits a root development in excess of three-quarters of its expected final length (Figure 1.3). Thus, a radiograph of the permanent successor is needed to determine the status of the deciduous tooth and, by implication, its treatment. A permanent tooth with delayed eruption is an unerupted tooth whose root is developed in excess of this length and whose spontaneous eruption may be expected in time. A tooth which is not expected to erupt in a reasonable time in these circumstances is termed an impacted tooth. Dental age is not assessed with reference to a single tooth only, since some variation is found within the different groups of teeth. An all-round assessment must be made and, only then, can a definitive determination be offered. However, in doing this one should be wary of including the maxillary lateral incisors, the mandibular second premolars and the third molars, the timing of whose development is

Fig. 1.3  The mandibular left second deciduous molar is retained (extraction contraindicated), since the root development of its successor is inadequate for normal eruption. The right maxillary deciduous canine, in contrast, is overretained (extraction advised), since the long root of its successor illustrates delayed eruption.

not always in line with that of the remaining teeth [8, 9]. These are the same teeth that are most frequently congenitally missing in cases of partial anodontia (oligodontia). Indeed, reduced size, poorly contoured crown form and late development of these teeth are all considered microforms of missing teeth [9–11]. It is important to note that this variation in the timing of their development is only ever expressed in lateness, and they are not to be found in a more advanced state of development than the other teeth. If the individual dental ages of any of these variable groups of teeth is advanced, then so too is the entire dentition in which they occur.

Assessing dental age When studying full-mouth periapical radiographs or a panoramic film several criteria can be used in the esti­ mation of tooth development. The first radiographic signs of the presence of a tooth are seen shortly after the initiation of calcification of the cusp tips. Thereafter, one may attempt to delineate the completed crown formation and various degrees of root formation (usually expressed in fractions), through to the fully closed root apex. By and large, orthodontic treatment is performed on a relatively older section of the child population and, as such, the stages of root formation are usually the only factors which remain relevant. The stage of tooth development that is easiest to define is that relating to the closure of the root apex. For as long as the dental papilla is discernible at the root end, the apex is open and still developing. Once fully closed, the papilla disappears and a continuous lamina dura is seen to intimately follow the root outline. The accuracy with which one may assess fractions of an unmeasurable and merely ‘expected’ final root length is far less reliable and much more subject to individual observer variation. Root development of the permanent teeth is completed approximately 2.5–3 years after normal eruption [5]. This allows us to conclude that, at the age of 9 years, the mandibular incisors (which erupt at age 6) will be the first teeth to exhibit closed apices and that these will usually be closely followed by the four first permanent molars. At 9.5 years, the mandibular lateral incisors will complete, while at 10 years and 11 years, respectively, the roots of the maxillary central and normally developing lateral incisors will be fully formed. This being so, when presented with a set of radiographs, we may proceed to assess dental age by following a simple line of investigation, which uses the dental age of 9 years as its starting point and then progresses forward or traces its steps back, depending on its findings. If the mandibular central incisor roots are complete, we may presume the patient is at least 9 years old (dental age) and we may then advance, checking for closed apices of first molars (9–9.5 years), mandibular lateral incisors (9.5 years), maxillary central incisors (10 years), normally developing

4  Orthodontic Treatment of Impacted Teeth maxillary lateral incisors (11 years), mandibular canines and first premolars (12–13 years), maxillary first premolars (13–14 years), normally developing second premolars and maxillary canines (14–15 years) and second molars (15 years). By this method, we may arrive at a tentative determination for dental age on the basis of the last tooth in this sequence which has a closed apex (Figure 1.4). It is now important to relate the actual development of the remaining teeth in the sequence to their expected development that may be derived from the wall chart or from tables that have been presented in the literature. This may then provide corroborative evidence in support of an overall and definitive dental age determination. When the dental age is less than 9 years, none of the permanent teeth will have completed their root development and the clinician will have no choice but to rely on an estimation of the degree of root development, degree of crown completion and, in the very young, initiation of crown calcification (Figure 1.5). This is most conveniently done by working backwards from the expected development at age 9 years and comparing the dental development

status of the patient to this, beginning with the mandibular central incisors and the first permanent molars. Thus, at dental age 6 years, one would find one-half to two-thirds root length of these teeth and this could be confirmed by studying the development of the other teeth. At the same time, one should expect unerupted maxillary central incisors with half root length, mandibular canines with onethird root length, first premolars with one-quarter root length, and so on. As pointed out earlier, variation occurs, and this may lead to certain apparent contradictions. In such cases, excluding the affected maxillary lateral incisors, mandibular second premolars or third molars from the calculation will usually simplify the procedure and contribute to its accuracy. As we have noted, early development of these teeth in relation to the development of the remainder of the dentition does not appear to occur. Individual variability is expressed only in terms of degrees of lateness. This means that the developmental status of these teeth may be used as corroborative evidence for the determination of dental age, provided that their own timing is first confirmed as being in line with the remainder of the dentition. Unusually small teeth, coniform premolars and mandibular incisors, and peg-shaped lateral incisors are most often seen developing very much later than normally shaped and sized teeth of the same series, sometimes as much as three or four years later, and should not be included in the overall estimation. Thus, in diagnosing dental age for a patient with an abnormality of this nature, one may present a determination for the dentition as a whole, with the added notation that this individual tooth may have a much lower dental age. Typically, we may occasionally examine a 14-year-old patient who has a complete permanent dentition, including the second molars, with the exception that a mandibular second deciduous molar is present. The radiographs (Figure 1.6) show the apices of

Fig. 1.4  Root apices are closed in all first molars, all mandibular and three of the maxillary incisors, excluding the left lateral incisor.

Fig. 1.5  No closed apices. Dental age assessment 7.5 years.

Fig. 1.6  Late-developing second mandibular premolars with retained (not over-retained) deciduous second molars in a child with dental age 11–12 years. The contrast and brightness of the picture have been adjusted in the relevant areas to clearly show the stage of development of these tooth buds.

General Principles Related to the Diagnosis and Treatment of Impacted Teeth  5  the first molars, central and lateral incisors, mandibular canines and premolars to be closed, while the maxillary canines and the second molars are almost closed. However, the unerupted mandibular second premolar has an open root apex and development equivalent to about a quarter of its expected eventual length, or less. On the basis of this information, we may assess the dental age of the dentition as a whole to be 14 years. At the same time, we would have to note that the dental age of the unerupted second premolar is approximately 7 years. Having made this determination, we may now confidently say that the second premolar, individually, does not exhibit delayed eruption and the deciduous second molar is not over-retained in the context of the terminology used here. Accordingly, it would not be appropriate to extract the deciduous tooth at this time, but to wait at least a further few years, at which time the tooth may be expected to shed normally. To summarize this discussion, it is essential to differentiate between four different conditions that may exist when we encounter a dentition which includes certain deciduous teeth inconsistent with the patient’s chronological age. Because the ensuing classification of these conditions is treatment oriented, the labelling of a patient within one of these groupings indicates the treatment that is required: 1 A late-developing dentition.  The dental age of the patient lags behind the chronological age, as witnessed radiographically by less root formation than is to be expected at a given age, in the entire dentition. Typically, this will be evident clinically by the continued and symmetrical presence of all the deciduous molars and canines on each side of each jaw. The extraction of deciduous teeth is contraindicated, since the teeth are expected to exfoliate normally when the appropriate dental age is reached. 2 Over-retained deciduous teeth.  The dental age of the patient may be positively correlated with the chronological age, but the radiograph shows an individual permanent tooth or teeth with well-developed roots, which remain unerupted. This tends to be localized in a single area and may be due to an ectopic siting of the permanent tooth bud, which has stimulated the resorption of only a portion of the root of its deciduous predecessor, but shedding has not occurred due to the persistence of the remaining part of the root or of a second and unresorbed root. Nevertheless, the condition may occasionally be found symmetrically in a single dental arch or in both arches. Extraction of the over-retained tooth or teeth is indicated. 3 A normal dental age, with single or multiple late-developing permanent teeth.  This condition is commonly found in relation to the maxillary lateral incisor and the mandibular second premolar teeth, and extraction of the deciduous predecessor is to be avoided. Normal shedding of the tooth is to be expected when the root of the

permanent tooth reaches two-thirds to three-quarters of its expected length. 4 A combination of the above.  Sometimes one may see features of each of the above three alternatives in a single dentition. The importance of interpreting the differential diag­ nosis for a given patient cannot be over-emphasized, since it has far-reaching effects on all the aspects of diagnosis, treatment planning and treatment timing for cases with impacted teeth.

When is a tooth considered to be impacted? From the work of Grøn [12] we learn that, under normal circumstances, a tooth erupts with a developing root and with approximately three-quarters of its final root length. The mandibular central incisors and first molars have marginally less root development and the mandibular canines and second molars marginally more when they erupt. We may therefore take this as a diagnostic baseline from which to assess the eruption of teeth in general. Thus, should an erupted tooth have less root development (Figure 1.7), it would be appropriate to label this tooth as prematurely erupted. This will usually be the consequence of the early loss of a deciduous tooth, particularly one whose extra­ ction was dictated by deep caries with resultant periapical pathology. At the opposite end of the scale, we find the unerupted tooth which exhibits a more completely developed root. The normal eruption process of this tooth must be presumed to have been impeded by one of several aetiolo­ gical possibilities. These include such factors as a failure of resorption of the roots of a deciduous tooth, an abnormal eruptive path, a supernumerary tooth, dental crowding, a much enlarged dental follicle/dentigerous cyst, other forms of soft tissue pathology or a disturbance in the eruption mechanism of the tooth. However, a thickened

Fig. 1.7  The left mandibular premolars are prematurely erupted, with insufficient root development.

6  Orthodontic Treatment of Impacted Teeth

(a)

(b) Fig. 1.8  (a) The right mandibular second premolar was extracted at age 8.5 years. (b) Seen at age 11, the root of the unerupted first premolar is almost completed.

post-extraction or post-trauma repair of the mucosa (Figure 1.8) should not be overlooked as a potent cause of non-eruption. Not infrequently, and particularly in the mandibular premolar region, there may be a history of very early extraction of one or both deciduous molars. Delayed or noneruption of the premolars will occur due to a thickened mucosa overlying the teeth. It is usually possible to palpate these teeth, their distinct outline clearly seen bulging the gum for a period of a year or more, although eruption may not occur.

Impacted teeth and local space loss A time lapse exists between the performance of a surgical procedure to remove the cause of an impaction and the full

eruption of the impacted tooth into its place in the dental arch. The extent of this timespan is dependent on several factors, such as the initial distance between the tooth and the occlusal plane, the stage of development of the particular tooth, the age of the patient and the manner in which hard and soft tissue may be laid down in the healing wound. During this period, therefore, local changes in the erupted dentition may occur as the result of the break in integrity of the dental arch caused by the surgical procedure, such as space loss and tipping of the adjacent erupted teeth. This intervention is no less susceptible to the drifting of neighbouring teeth than is any other factor that may produce interproximal loss of dental tissue. With an odontome or supernumerary tooth in the path of an unerupted permanent tooth, vertical (and sometimes mesial, distal, buccal or lingual) displacement of the permanent tooth is likely to be considerable. It would be convenient if removal of the space-occupying body could be performed leaving the deciduous teeth intact, since the deciduous tooth would maintain arch integrity during the extended period needed for the permanent tooth to erupt normally. Unfortunately, in order to gain access to perform the desired surgery, one or more deciduous teeth often need to be extracted. This being so, and having regard for the long distance that a displaced permanent tooth may have to travel before it erupts into the mouth, space maintenance should be regarded as essential in most cases, particularly in the posterior area. It should be the first orthodontic procedure to be considered, preferably in advance of the surgical procedure, and it should be retained until full eruption of the permanent tooth has occurred. Impacted teeth are often associated with a lack of space in the immediate area. This is frequently due to the drifting of adjacent teeth, although crowding of the dentition in general may be the prime cause. In such cases, the spontaneous eruption of an impacted tooth is unlikely to occur unless adequate or, preferably, excessive space is provided. It would be convenient if excision of the associated pathological entity could be comfortably delayed until this time to bring about the desired eruption and permit this corrective treatment to be attempted when the root development of the unerupted tooth is adequate. However, the surgeon will insist on removing most forms of pathology as soon as a tentative diagnosis is reached, in order to obtain examinable biopsy material for the establishment of a definitive diagnosis. Odontomes and supernumerary teeth are generally considered to be exceptions to this rule and the timing of their removal may be considered more leisurely.

Whose problem? Patients do not go to their dentist complaining of an impacted tooth. They are frequently unaware that this abnormality exists, since there is no pain, discomfort or swelling. Nor is it obvious to the layman that there is a

General Principles Related to the Diagnosis and Treatment of Impacted Teeth  7 

Fig. 1.9  Unerupted right maxillary central incisor with space loss.

missing tooth, since the deciduous predecessor may not shed naturally in these circumstances. The vast majority of impacted teeth come to light by chance, in routine dental examination, and are not the result of a patient’s direct complaint. As a general rule, it is the paedodontist or general dental practitioner who, during a routine dental examination, discovers and records the existence of an over-retained deciduous tooth. A periapical radiograph will then confirm the diagnosis. There are two principal exceptions whereby an abnormal appearance may motivate the patient to seek professional advice. The first of these usually brings the patient to the office at the age of 8–10 years, when a single maxillary central incisor will have erupted a year or so earlier and the parent points out that the erupting lateral incisor of the opposite side has not left enough space for the expected eruption of the second central incisor (Figure 1.9). Often, the deciduous central incisor is over-retained. In this situation, the parent has recognized the abnormality, but will not generally have the technical understanding to suggest the possibility of impaction of the unerupted central incisor. The second exception occurs with a 14–15-year-old patient who requests the restoration of an unsightly carious lesion on an over-retained maxillary deciduous canine. Generally speaking, the patient will be unaware that this is not a permanent tooth and it will require suitable professional advice to point out that restoration is probably not the appropriate line of treatment, but rather extraction and resolution of the impaction of the permanent canine. A very small percentage of cases may initially be seen by their general dental practitioner because of symptoms related to relatively rare complications of impacted teeth. Among these symptoms are mobility or migration of adjacent teeth (due to extensive root resorption), painless bony expansion (dentigerous or radicular cyst) or perhaps pain and/or discharge (non-vital over-retained deciduous tooth or infected cyst, with communication to the oral cavity) [13].

Initially, the practitioner should ascertain whether there is a good chance that resolution will be spontaneous once the aetiological factor has been removed or whether active appliance therapy will be needed. To be able to do this, the exact position, long-axis angulation and rotational status of the tooth have to be accurately visualized and an assessment of space in the arch needs to be made. Following this initial assessment, the paedodontist or general dental practitioner now has to decide who should treat the problem. Many dentists will prefer not to accept responsibility for the case and will refer the patient to an oral and maxillofacial surgeon on the premise that surgery will be needed. Many surgeons will agree that the problem is essentially surgical in nature and will proceed to remove over-retained deciduous teeth, clear away other possible aetiological factors, such as supernumerary teeth, odontomes, cysts and tumours, and will also expose the impacted permanent tooth. If the impacted tooth is buccally located, the surgical flap may be apically repositioned to prevent primary closure and to maintain subsequent visual contact with the impacted tooth after healing has occurred. This will have the effect of encouraging eruption in many cases. Until healing (by ‘secondary intention’) has occurred, the wound will usually be packed with a proprietary zinc oxide/ eugenol-based periodontal pack (e.g. CoePack®) or a gauze strip impregnated with Whitehead’s varnish, over a period of a few weeks. Careful placement and wedging of the pack between an impacted tooth and its neighbour is used by surgeons to help free the tooth to erupt naturally when the pack is later removed. Often, in the more difficult impactions, wider surgical exposure is undertaken, which includes fairly radical bone resection, both around the crown and down to the cemento-enamel junction, with complete removal of the dental follicle. The principal aims of this procedure are to clear away all possible impediments to eruption and to ensure that subsequent healing of the soft tissues does not cover the tooth again. Following a period of many months and (for some of the more awkwardly positioned teeth) sometimes extending into years, the surgeon, family dentist or paedodontist will usually then follow up the spontaneous eruption of the impacted tooth until it reaches the occlusal level. If, at that time, alignment is poor or the tooth still has not erupted, the patient will be referred to the orthodontist. They may alternatively and preferably refer the patient directly to an orthodontist in the first place. Certainly, the orthodontist cannot directly influence the position of the impacted tooth until appropriate access has been provided surgically and an attachment has been placed on the tooth. Nevertheless, with proper planning and management, including referral for surgical exposure at the appropriate stage in the treatment, a much higher level of quality care may be provided and in a very much shorter timeframe. This will be discussed in the ensuing chapters of this book.

8  Orthodontic Treatment of Impacted Teeth

The timing of the surgical intervention From the above discussion, we see that the timing and nature of the surgical procedure are determined by the degree of development of the teeth concerned, at the time of the initial diagnosis. At an early stage, a radiographic survey of a very young child may reveal pathology, such as a supernumerary tooth, an odontome, a cyst or benign tumour, which appears likely to prevent the normal and spontaneous eruption of a neighbouring tooth. At this stage, it would be inappropriate to expose the crown of an immature tooth from every point of view. In the first place, one would not want to encourage the tooth to erupt before an adequate (half to two-thirds) root length has been produced. Second, at that early stage of its development, the tooth cannot be considered as impacted and, given time and freedom to manoeuvre, will probably erupt by itself. Early exposure risks the possibility of damage to the crown and to the subsequent root development of the tooth. Nevertheless, with the discovery of the pathological condition (Figure 1.10), the potential for impaction exists and leaving the condition untreated will worsen the prognosis. Accordingly, removal of the pathological entity, without disturbing the adjacent permanent teeth or their follicular crypts, should be the aim of any treatment at that time. It may then reasonably be expected that normal development and eruption will eventually occur. Whilst this is an obviously desirable course of action, access to the targeted area may be thwarted by the presence and closeness of adjacent developing structures and delay may still be advised. The second scenario occurs when the condition is only discovered much later. In this case (Figure 1.11), it may be seen that the superiorly displaced central incisors have fully developed, if angulated, roots and the adjacent lateral incisors have erupted with almost the full length of their roots completed. The central incisors may justifiably be defined as impacted, and the aims of surgical treatment become

Fig. 1.10  A midline supernumerary tooth (mesiodens) discovered in routine periapical radiographic view of the maxillary incisor area in a 4-year-old child.

two-fold: first, to eliminate the pathology, and then to create optimal conditions for the eruption of the permanent tooth, which is already late. This will usually involve exposure of the crown of the tooth. For many teeth, given adequate space in the dental arch and little or no displacement of the impacted tooth, spontaneous eruption may be expected [14, 15]. As we shall see in subsequent chapters, there are several situations and tooth types where this may not occur, or may not occur in a reasonable time-frame, often due to severe displacement of the affected tooth. For these cases, the natural eruptive potential of the tooth is supplemented and, if necessary, diverted mechanically, with the use of an orthodontic appliance.

Patient motivation and the orthodontic option Angle’s class 2 malocclusion is present in between one-fifth and one-quarter of the child population in most countries of the western world [16, 17]. However, even a cursory analysis of the patient load of any given orthodontic practice will reveal that around three-quarters of the patients are being treated for this malocclusion. The reason for this has to do with the fact that a patient’s appearance is adversely affected to a greater extent by this condition than by most others. In other words, appearance plays an extremely large part in the initiative and motivation on the part of the parent of this young patient to seek treatment. A significant section of the remaining quarter of the patients in this hypothetical orthodontic practice are being treated for various less unsightly conditions (crowding, single ectopic teeth, open bites or class 3 relationships). This leaves only a few patients in this practice sample who have been referred for strictly health reasons, which may not be obvious to the patient. Appearance is not a problem for this small group of patients, who will have agreed to orthodontic treatment only after they have been motivated by the careful and

Fig. 1.11  The panoramic view shows erupted maxillary permanent lateral incisors and over-retained deciduous central incisors. The unerupted permanent central incisors can be seen superior to the two unerupted supernumerary teeth. (Courtesy of Dr I. Gillis.)

General Principles Related to the Diagnosis and Treatment of Impacted Teeth  9  persuasive explanations of a dentist, orthodontist, periodontist, prosthodontist or oral surgeon, regarding the ills that are otherwise likely to befall them and their dentition. Most impactions are symptomless and, aside from maxillary central incisors, do not usually present an obviously abnormal appearance. Accordingly, motivation for treatment in these cases is minimal, and much time has to be spent with the patient before he/she agrees to treatment. The story does not end there, since these patients may often require periodic ‘pep talks’ to maintain their cooperation and the resolve to complete the treatment. Many of them will not maintain the required standard of oral hygiene, and, while it is difficult to justify continuing treatment in these circumstances, it is just as difficult to remove appliances from a patient in the middle of treatment, when impacted teeth have partially erupted and large spaces are present in the dental arch. For these reasons, while ambitious and innovative treatment plans may be suggested, it is essential to take motivation into account before advising lengthy and complicated treatment, since the risk of noncompletion may be high.

References   1.  Krogman WM. Biological timing and the dentofacial complex. J Dent Child 1968; 35: 175–185.

  2.  Schour I, Massler M. The development of the human dentition. J Am Dent Assoc 1941; 28: 1153–1160.   3.  Moorrees CFA, Fanning EA, Grøn A-M, Lebret L. The timing of orthodontic treatment in relation to tooth formation. Trans Eur Orthod Soc 1962; 38: 1–14.   4.  Moorrees CFA, Fanning EA, Hunt EE Jr. Age variation of formation stages for ten permanent teeth. J Dent Res 1963; 42: 1490–1502.   5.  Nolla CM. The development of permanent teeth. J Dent Child 1960; 27: 254–266.   6.  Demerjian A, Goldstein H, Tanner JM. A new system of dental age assessment. Hum Biol 1973; 45: 211–227.   7.  Koyoumdjisky-Kaye E, Baras M, Grover NB. Stages in the emergence of the dentition: an improved classification and its application to Israeli children. Growth 1977; 41: 285–296.   8.  Garn SM, Lewis AB, Vicinus JH. Third molar polymorphism and its significance to dental genetics. J Dent Res 1963; 42: 1344–1363.   9.  Sofaer JA. Dental morphologic variation and the Hardy-Weinberg law. J Dent Res 1970; 49 (Suppl): 1505. 10.  Gràhnen H. Hypodontia in the permanent dentition. A clinical and genetic investigation. Odontol Revy 1956; 79 (Suppl 3): 1–100. 11.  Alvesalo L, Portin P. The inheritance pattern of missing, peg-shaped and strongly mesio-distally reduced upper lateral incisors. Acta Odontol Scand 1969; 27: 563–575. 12.  Grøn A-M. Prediction of tooth emergence. J Dent Res 1962; 41: 573–585. 13.  Shafer WG, Hine MK, Levy BM. A Textbook of Oral Pathology, 4th edn. Philadelphia: WB Saunders, 1983. 14.  DiBiase DD. The effects of variations in tooth morphology and position on eruption. Dent Pract Dent Rec 1971; 22: 95–108. 15.  Mitchell L, Bennett TG. Supernumerary teeth causing delayed eruption – a retrospective study. Br J Orthod 1992; 19: 41–46. 16.  Brin I, Becker A, Shalhav M. Position of the maxillary permanent canine in relation to anomalous or missing lateral incisors: a population study. Eur J Orthod 1986; 8: 12–16. 17.  Massler M, Frankel JM. Prevalence of malocclusion in children aged 14–18 yrs. Am J Orthod 1951; 37: 751–760.

2 Radiographic Methods Related to the Diagnosis of Impacted Teeth (In Collaboration with Stella Chaushu) Qualitative radiography

11

Three-dimensional diagnosis of tooth position

14

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

Radiographic Methods Related to the Diagnosis of Impacted Teeth 11 It is not the purpose of this chapter to present a complete manual on dental radiography, but rather to highlight concisely those techniques and methods that are useful in the clinical setting, as it pertains to impacted teeth. The methods offered have two main aims [1, 2]. The first relates to the furnishing of qualitative information regarding normal and abnormal conditions that may be associated with unerupted teeth. Thus, the different ways of radiologically displaying and recognizing pathological entities, such as supernumerary teeth, enlarged eruption follicles, odontomes, root resorption and other pathological entities, are discussed and compared. The second aim is to describe the various radiological techniques that the clinician may find helpful in accurately pinpointing the position of a clinically invisible, unerupted tooth in the three planes of space. The relative merits of these techniques are discussed and indications for their use are suggested in relation to the different groups of teeth concerned.

Qualitative radiography Periapical radiographs The first, simplest and most informative X-ray film is the periapical view. This view is oriented to pass through the minimum of surrounding tissue, in order to give accuracy and quality of resolution. It is generally aimed to be perpendicular to an imaginary plane which bisects the angle between the long axis of an erupted tooth and the plane of the film, to produce the minimum of distortion. The periapical film is designed to view the tooth itself from the angle of best advantage, unrelated to its position in space. From this view, it will be immediately obvious if there is an impacted tooth and if its stage of development is similar to that of its erupted antimere, with at least two-thirds of its root length. The presence and size of a follicle will be obvious, and crown or root resorption, root pattern and integrity will be possible to ascertain. The presence and description of hard tissue obstruction will be evident, allowing the observer to distinguish connate, incisiform and barrel-shaped supernumeraries, and odontomes of the complex or compound composite type. Similarly, it will show soft tissue lesions, such as cysts. The great clarity that the view offers is superior to other views and should always be used as the initial film of a suspected impacted tooth in a radiographic examination. As with any radiographic film, however, the periapical view is two-dimensional, and thus can give no information in the bucco-lingual plane. Overlapping structures cannot be differentiated on a single film as to which is lingual and which buccal. For this film to give the most advantageous view of the teeth in the maxillary arch and in the mandibular anterior segment, the central ray of the periapical view is oblique, and will vary between 20° and 55° to the occlusal plane [3] depending on the region to be X-rayed. Given this oblique direction, any attempt to estimate the height of an impacted

tooth or its bucco-lingual location, without additional information, must fail. When performing periapical radiography on the posterior teeth in the mandibular arch, however, the most advantageous direction has the central ray very close to the horizontal and as such also offers a true lateral view of these teeth. Thus, not only will the observer see the most precise detail of the tooth and its surrounding tissues, it will also be possible to accurately assess its height in the jaw. Occlusal radiographs Mandibular arch

In the mandibular arch, this view is properly executed by tipping the patient’s head backwards and pointing the X-ray tube at right-angles to a film, held between the teeth, in the occlusal plane (Figure 2.1). The head will need to be tipped back to permit the positioning of the X-ray tube under the chin. In the lower canine/premolar region, the occlusal view is a ‘true’ occlusal view and should depict all the posterior standing teeth in cross-section, and as such should also provide bucco-lingual positional information on the tooth and any associated structures in a plane at right-angles to that seen on the periapical film. Due to the thickness of bone traversed, detail is much poorer, unless there is expansion owing to a large cyst or a bucco-lingually displaced tooth. In order to produce a true occlusal view in the anterior region of the mandibular arch (Figure 2.1), the head will need to be tipped back further and the tube pointed at the symphysis menti, at an angle of 110° to the horizontal, in line with the long axes of the incisor teeth. To achieve the same for the molar teeth, the 90° angle to the horizontal will need to be augmented by a 15° medial tilt of the tube, to compensate for the characteristic slight lingual tipping of these teeth [3]. This means that, ideally, the film should

Image not available in the electronic edition

Fig. 2.1 The angle of the central ray in a true occlusal view of the lower jaw depends on the area of interest. Reproduced from previous edition with the kind permission of Informa Healthcare – Books.

12 Orthodontic Treatment of Impacted Teeth

Image not available in the electronic edition

Fig. 2.3 A true vertex occlusal film using Ong’s projection, showing two palatal canines. The right canine is close to the arch and almost vertical. The crown of the left canine reaches the midline suture, while its root apex is close to the line of the arch. Fig. 2.2 A diagram showing incisor inclination, film position and central X-ray beam, differentiating the periapical view, the anterior (oblique) occlusal view and the true vertex occlusal view. Reproduced from previous edition with the kind permission of Informa Healthcare – Books.

be performed individually for each side, in order to capture each molar in its long axis and its true occlusal view. Maxillary arch Maxillary anterior occlusal

In the maxillary arch, the nose and forehead interfere with the positioning of the X-ray tube, close to the area to be viewed. The best that can be achieved by positioning the tube close to the face is an oblique, anterior, maxillary occlusal view of the teeth, which is perhaps better described as a high or steeply angled periapical view (Figure 2.2). The view will ‘shorten’ the apparent length of the roots, but it will be a far cry from the cross-sectional view that is so easy to achieve in the mandibular arch. Since the central ray passes through cancellous rather than the compact bone that is found in the mandible, detail is usually good, although not as clear as with the periapical view. True (vertex) occlusal

A true occlusal view of the anterior maxilla is a view in which the central ray of the X-ray beam runs parallel to the long axis of the central incisors (Figure 2.3). This is only possible when the cone is placed over the vertex of the skull, to produce the vertex occlusal film. Since the beam has to travel a great distance through the cranium and its contents, the base of the skull and the maxilla, there is a considerable loss in clarity. An excellent alternative method of producing this view, with the film positioned extra-orally, has been described [4]. Notwithstanding, a very long exposure is required, and a fast film should be used in a cassette with

intensifying screens. For all these reasons, the method has never been popular. It is, therefore, almost with a collective sigh of relief among professionals that the method has been totally superseded by the introduction of volumetric cone beam computerized tomography (CBCT) scanning. This imaging modality, which can give the same and much more information with little or no increase in radiation dosage, has developed considerable sophistication within a very short space of time and is discussed at the end of this chapter. Nevertheless, in this view (Figure 2.3), all the anterior teeth will be seen in their cross-sectional aspect as small circles with a tiny concentric circle in the centre, denoting the pulp chamber and root canal. No information is available regarding the relative height of the object in the alveolus and it certainly cannot be used for fine detail. A single tooth which is palatal to the line of the arch will appear within this arc of small circles. If the tooth is at an angle, not parallel with its neighbours, it will show up in its elliptical, oblique cross-section, representing a tilted long axis. In the event that the tooth is horizontal across the palate, its full length will be obvious on this view, together with the exact mesio-distal and bucco-lingual orientation of both the root and the crown, in the horizontal plane. The difference may not seem to be very great between the two types of occlusal film, but it should be appreciated that from the vantage point of an anterior occlusal film, the anterior teeth will be foreshortened, but they will still have appreciable length. In this situation, a high and mesially placed labial canine could give virtually the same picture as

Radiographic Methods Related to the Diagnosis of Impacted Teeth  13 

(a)

(b)

(c)

(d)

(e)

Fig. 2.4  (a) The periapical view shows an impacted left maxillary central incisor, due to an inverted, unerupted, supernumerary tooth. The deciduous tooth is over-retained. Accurate diagnosis of the height of the impacted tooth in the alveolus is not possible from this view. (b) The anterior maxilla seen on a lateral cephalometric radiograph shows the high impacted central incisor, facing the labial sulcus. (c) and (d) The same views as (a) and (b) after removal of the supernumerary tooth and bracket bonding on the exposed incisor. (e) A parallel intra-oral photographic view. The film has been laterally inverted to simplify comparison (Courtesy of Dr D. Harary.)

a low and mesially placed palatal canine. This could not happen in a vertex occlusal projection. Extra-oral radiographs The panoramic view, while not showing detail to the same degree as a periapical film, has the advantage of simply and quickly offering a good scan of teeth and jaws, from the temporo-mandibular (TM) joint on one side to the TM joint on the other. It is probably true to say that, today, orthodontists are in general agreement that this film gives

the most qualitative information to act as a starting point from which to proceed to other forms of radiography, in line with the demands of the particular situation in any given case. True and oblique extra-oral views (Figure 2.4a–e) and the variously angulated oblique occlusal films all provide information that may be used to complement the peria­ pical film, particularly when tooth displacement is severe. However, the use of any oblique film for the accurate locali­ zation of a buried tooth may frequently be misleading, be

14 Orthodontic Treatment of Impacted Teeth it a single periapical, an occlusal or a lateral jaw film. This being so, two incipient dangers exist. First, a surgical procedure may be misdirected and a flap opened on the wrong side of the alveolar process. Second, misinterpretation of the tooth’s position may lead the operator to consider there to be a very favourable prognosis for biomechanical resolution when, in fact, the tooth may be in a completely intractable position. Thus, the choice of treatment will be inappropriate.

Three-dimensional diagnosis of tooth position As dentists, we are used to seeing periapical films of individual teeth and, provided that the teeth concerned are erupted and in the line of the arch, these films have many advantages. However, in this view, the X-ray tube is not directed in either the true horizontal, true vertical or true lateral plane. Aside from radiography of the mandibular posterior teeth, the tube is always tipped at an angle to one or more of these planes. For an erupted tooth, this is unimportant, since the third dimension is supplied by direct vision within the mouth. Thus, while it gives a good two-dimensional representation of the tooth, this view has limited value when visualization of an unerupted tooth is required in the three planes of space.

to a tangent to the line of the arch at this point, as for any periapical view, and at the appropriate angle to the horizontal plane for the tooth in question (50° for the central incisor, etc.) 2. A second film is placed in the mouth in the identical position but, on this occasion, the X-ray tube is shifted (rotated) mesially or distally round the arch, but held at the same angle to the horizontal plane and directed at the mesially or distally adjacent tooth. To achieve this, the tube should describe an arc of between 30° and 45° of a circle whose centre is somewhere in the middle of the palate. There should be no problem identifying which of the two films is the ortho-radial view and which was taken from the distally deviated aspect by studying the relative distortion of the erupted teeth on the two films. However, by radiographically ‘labelling’ the deviated film with the placement of a paper clip in one corner or by using a different film size for the deviated view, such as an occlusal-sized film, this distinction will be simplified. Let us assume that a right unerupted canine is palatally placed (Figure 2.6), and then this tooth will be close to the

Parallax method [5] By following the principles involved in binocular vision, two periapical views of the same object and taken from slightly different angles can provide depth to the flat, twodimensional picture depicted by each of the films individually (Figure 2.5). This is of considerable help with distinguishing the buccal or lingual displacement of the canine which is low down and fairly close to the line of the arch, and is performed in the following manner (Figure 2.6): 1. A periapical-sized film is placed in the mouth, with the patient’s finger holding it against the palatal aspect of the area where the tooth would normally be situated. The X-ray tube is directed at right angles (ortho-radial)

Fig. 2.5 The left periapical view, oriented for the central incisors, shows the crown of the canine superimposed on the distal half of the central incisor root. The middle film, rotated 30° to the left, shows the canine overlapping only the lateral incisor root. By rotating the central beam a further 30°, superimposition of the canine over the lateral incisor root has been eliminated. The canine is palatally displaced.

Image not available in the electronic edition

Fig. 2.6 A diagrammatic representation of the parallax method. If the observer ’s eye peers along the axis of the X-ray beam in each case, the image on the film will be easy to reconstruct. Reproduced from previous edition with the kind permission of Informa Healthcare – Books.

Radiographic Methods Related to the Diagnosis of Impacted Teeth  15  middle of the picture obtained in both films. However, in the first picture (direction B), where the tube is directed over the designated canine area of the ridge, the lateral incisor root will be on the right of the picture. If the canine is also mesially displaced, there will be some overlap of the canine crown and the lateral incisor root. On the second picture, taken from the front (direction A), the right lateral incisor root and the crown of the palatal canine will be in the middle of the picture, superimposed on one another, to a much greater degree. Jacobs [7, 8] enjoins the observer to use the right eye in place of the X-ray tube and suggests the useful exercise of holding up two fingers vertically, at eye level, with one finger obscuring the other. If the observer now closes this eye and opens the other, his/her new vantage point for inspection will have resulted in a visual separation of the two fingers. Through the left eye, the obscured finger will have ‘moved’ to the left of the forward finger, to become partially visible. Transferring this to the radiographic context, in the second picture, the tooth furthest from the tube (i.e. the palatal tooth) will ‘move’ in the same direction that the X-ray tube has travelled from the first exposure. This method has its limitation, although it is very useful in cases where there is a minimal height discrepancy between the erupted and unerupted adjacent teeth. However, when the canine is high and the periapical view shows no superimposition of the canine with the roots of the erupted teeth, or where the superimposition is only in the apical area, then the overall picture may be very mis­ leading and a different method of localization should be used. The periapical view is directed from above the occlu­ sal plane and in an oblique downward and medial direction, which distances the palatal canine from the roots of the other teeth and makes it appear higher than the anatomy of the maxilla would allow. While it may prove useful in locating the position of the crown of the impacted tooth, it is not adequate to the task of accurately placing the root apex and, thereby, defining the orientation of its long axis. These are important parameters when assessing treatment difficulty and prognosis during the treatment planning stage and critical for the successful resolution of an impacted tooth, as we shall see in the following chapters. Vertical parallax may sometimes be a useful variant of the same technique, in which two films are taken of the area, with the central ray of one periapical film being more steeply angled in the vertical plane than the other. In this manner, the separation of the images in the more steeply angled (above the occlusal plane) film will result in a palatal tooth being more superiorly related vis-à-vis the target tooth than in the regular film. Unfortunately, the parallax method in general offers a relatively low degree of reliability. In a study to evaluate the usefulness of its two variants [6], six experienced orthodon­ tists were given the case records of 39 patients with ectopic canines. The cases were evaluated twice, once using films

that showed vertical parallax and once with films that fea­ tured horizontal parallax, although the parallax pairs were not revealed to the examiners as being of the same indi­ vidual. In 83% of cases the correct positional diagnosis was made with the horizontal method, while only 68% of cases were correctly diagnosed with the vertical method. These results expose the method as being too crude, or the experts insufficiently discerning, for it to be relied on with any degree of confidence. Thus, while often useful to obtain an initial overall impression, the method should certainly be backed up by more reliable diagnostic radiographic methods before a final treatment plan is presented to the patient. In the incisor region, an unerupted permanent incisor may be associated with one or two supernumerary teeth (mesiodentes). The parallax method is insufficiently clear in these cases, due to the presence of two or three hard tissue entities in the bone, superimposed on the outline of the roots of the deciduous teeth and at varying heights in the alveolus. The question arises whether the parallax principles may be applied to other types of film combinations, possibly with a greater degree of reliability. A vertical imaging dis­ crepancy between teeth in the line of the arch and those that are buccally or palatally displaced can be created between the panoramic view and the periapical/anterior occlusal views (Figure 2.7). The panoramic view is a rota­ tional tomograph, with the cone of the machine pointing upwards with a very small 7° tilt from below the occlusal plane, as it circles around the head of the patient. Because this view is recorded when the film is on the buccal side of the teeth and the cone directed from the palatal aspect, this is equivalent to a 7° tilt of the X-ray cone, when translated into a buccal-to-palatal direction. By contrast, the direction of the central ray in an anterior occlusal (6°–65°) or periapical view (5°–55°) is angulated much more steeply to the film. These will both show super­ imposition of an ectopic tooth over the tooth in the line of the arch, but a degree of vertical discrepancy between these films and the panoramic view will reveal the position of the displaced tooth. The same panoramic view will project the anterior midline area in its postero-anterior aspect, with the X-ray beam hitting this area when the cone is at the back of the patient’s head. The canine and premolar regions will be projected from an increasingly angulated viewpoint, as the X-ray cone moves from the back to the side of the head. The molar and retromolar areas will be projected from the side on the same revolving film as the consequence of the further rotation of the X-ray beam. If all the teeth are in the same approximate semicircular line of the arch, then their mesio-distal relationships will be fairly accurately represented on the film. However, a palatally displaced canine or premolar tooth is imaged when the X-ray cone is at a point in its arc of circle just

16  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 2.7  The vertical tube shift method using a panoramic film and periapical views. (a) The panoramic film shows the left canine very high and above the root apices of the incisors (arrow). The right canine superimposes on the apical third of the adjacent incisor. (b) The periapical views show the left and right canines overlapping one-third and two-thirds of the incisor roots, respectively. Both canines are labial.

(a)

(b)

Fig. 2.8  The lateral tube shift method using a panoramic film and a lateral cephalogram. (a) In the panoramic view, the X-ray cone projects this image in the premolar area when it is behind the ear of the opposite side and therefore provides an oblique lateral view. This gives the misleading impression that the unerupted right second premolar is rotated. (b) The lateral cephalometric view of the same patient shows only a very mild mesial displacement of the second premolar, with a minimal rotation of its palatal cusp in a mesial direction. Since this film is a true lateral view, this is the true mesio-distal position of the tooth.

behind the ear on the opposite side. Viewed from this posi­ tion, the palatally placed tooth will be ‘thrown’ mesial to its true mesio-distal position and will be shown superimposed more mesially on other structures than would be evident from its appearance on a lateral cephalogram [9]. Accord­ ingly, a panoramic film (an oblique lateral view) and a lateral cephalogram (a true lateral view) may be used together to determine the bucco-lingual location in the canine or premolar regions, in a similar manner to the use of two periapical views in Clark’s parallax method [5]. Obviously, this is dependent on the individual teeth being clearly discernible on the cephalogram, in which unavoid­ able superimposition in the anterior region may sometimes invalidate the method (Figure 2.8). One further clue to the position of an ectopic canine is governed by the physical principle that objects projected

optically on a screen become markedly larger as the dis­ tance between the object and the screen increases, or the distance between the object and the source decreases, with the degree of enlargement being directly proportional to the square of the object–screen distance. The panoramic X-ray machine is normally adjusted so that its circling of the jaws maintains a fixed distance of the cone to the dental arch, whose perimeter falls within the focal trough of the machine. Teeth which are palatal to the line of the dental arch become enlarged, because they are further from the film and closer to the cone. The mesio-distal width of a maxillary permanent canine is approximately 90% of the width of the maxillary central incisors. With a normally located canine, the distance between it and the film may be slightly larger than that of the central incisor, due to the form of the arch in that area.

Radiographic Methods Related to the Diagnosis of Impacted Teeth  17 

Fig. 2.9  A panoramic film showing two unerupted maxillary canines. Note the contrast in image size of the two canines. By direct measurement of the crown of the right canine, the mesio-distal width of its crown is considerably more than 15% larger than that of the right central incisor and the left is approximately the same width as the left central incisor. Since each shows superimposition on the middle portion of the root of its immediate neighbour, the right canine is palatal and the left buccal.

Thus, in these cases, it is common to see similar mesiodistal widths of these two teeth on the panoramic film. A buccally displaced canine, on the other hand, will generally reflect the true width difference between the two teeth, because its distance from the film is similar to that of the central incisor (Figure 2.9). This principle was used in an investigation of this phe­ nomenon, which revealed that when the mesio-distal width of the crown of an unerupted canine (as it appears and is measured directly on the panoramic film) was 1.15 times larger (i.e. 15% greater) than that of the adjacent central incisor (the canine-to-incisor index), then the canine was palatally displaced [10, 11]. This was found to be reliable in 100% of cases in which the canine was seen on the film to be superimposed on the coronal or middle portions of the root of the adjacent incisor. Earlier studies that attempted to diagnose canine posi­ tion on the panoramic film using the principle of diffe­ rential enlargement revealed only an 80–89% degree of reliability of diagnosis [12, 13]. This was due to the inclu­ sion of cases where the image of the canine was superim­ posed on the apical portion of the root of the incisor. The anatomy of the anterior portion of the maxilla is responsi­ ble for this aberration. Erupted permanent incisor teeth do not stand vertically upright, but their roots tip palatally at a significant angle to the vertical (Figure 2.10). This means that the root apices are considerably more distant from the film drum of the panoramic machine than are the crowns. If a canine is located high up on the labial side of the root apices, in the labial alveolar depression in the incisor region inferior to the nose, the tooth may still be considerably more distant from the film than the crowns of the incisors. Thus, the image of the canine crown will be enlarged to a greater extent than those of the incisor crowns and will appear disproportionately large on the film.

Fig. 2.10  On the dry skull, the roots of the maxillary incisor teeth can be seen to tip palatally at a significant angle to the vertical, creating a depression in the bone at the level of their apices. A canine impacted labially in this depression will be more distant from the panoramic film than the incisor crowns and will therefore cast a much enlarged image on the film. The use of the panoramic view for positional diagnosis at this relative height would therefore be incorrect.

Accordingly, the 1.15 canine-to-incisor index formula excludes all canines whose superimposition on the incisor root is high in the apical area. If the method is restricted to those cases in which the canine traverses the root of the incisor inferior to its apical third, then its use in determin­ ing the bucco-lingual positioning of the crown of an impacted tooth is valid, without the need to resort to other views. Radiographic views at right angles Radiographic views may be taken at right-angles to one another in various ways but, for the method to be of value, it must be possible to determine the exact orientation in space of both the film and the central ray [1, 2]. The observer must be in a position to deduce these from obser­ vation of other structures on the film, whose locations are known. Thus, if one begins with a periapical view, it becomes necessary to provide another view which is at 90° to it, in order to satisfy the minimum geometric conditions. However, having done this, it must be possible to recon­ struct mentally the exact orientation of this second view at a later date, by looking at the film alone and without neces­ sarily having prior knowledge of exactly how the tube and film were placed. This is obviously very confusing and com­ pletely impractical. Standardization Standardization of views within the confines of a strict adherence to the planes of space is required. Performed in

18  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

Fig. 2.11  (a) The true lateral cephalometric radiograph shows both canines superimposed at a higher level than the other teeth. Their axial inclination on the antero-posterior plane is favourable, with the crowns and apices apparently normally located. (b) The postero-anterior cephalometric radiograph shows the two canines similarly angulated, with their apices in the line of the arch and their crowns close to the midline. From these two films, we may conclude that the apices are ideally placed and that the long axes of the teeth have a downward, mesial and palatal inclination. (c) The panoramic view of the same patient. The appearance of canines close to the midline is very similar to that seen on the posterior-anterior cephalometric radiograph.

this manner, each two-dimensional view obtained becomes simple for the observer to appreciate and, when informa­ tion from the other views at right-angles is merged with it, the composite three-dimensional picture is easy to mentally reconstruct. A true lateral view (Figure 2.11a) will give exact information regarding both the antero-posterior and verti­ cal location of an object, relative to other structures that may be seen both on that radiograph and clinically. It will not give any clue to the bucco-lingual (transverse plane) picture. A true occlusal view will provide positional infor­ mation in both the antero-posterior and the transverse planes, but not in the vertical plane. The third possibility is the true antero-posterior view (Figure 2.11b, c), which defines the height (vertical plane) and the bucco-lingual relationship only. By combining the information provided by any two of these three films, three-dimensional localiza­ tion may be accurately determined. Translating these principles into radiographic practice presents some difficulties. However, these are not insur­ mountable and, insofar as they provide the clinician with accurate positional visualization of the unerupted tooth, they may be entirely worthwhile. For most orthodontic cases, a lateral cephalometric radi­ ograph (a cephalogram) is a prerequisite whose primary purpose is the routine measurement of angles and planes. However, this film potentially contains much useful posi­ tional information regarding the location and angulation of unerupted teeth. The film represents a true lateral view

of the skull and, for present purposes, of the jaws and the anterior maxilla in particular (Figure 2.11a). Although there are many superimposed structures in this area, the outline of a canine may be clearly seen. The direction of the long axis of the tooth in the anterior–posterior and vertical planes may be defined, together with the mesio-distal posi­ tion of both crown and apex. In the mandibular posterior area, we have pointed out that the routine periapical radiograph is also a true lateral view, with the X-ray tube pointing at right-angles across the body of the mandible and in the horizontal plane. The height and mesio-distal position of a buried tooth may then be accurately defined. The occlusal radiograph of this area is directed perpendicular to the occlusal plane and adds the bucco-lingual dimension to complete the three-dimensional picture. Accordingly, these two views will provide accurate localization of the position of unerupted teeth in this area (Figure 2.12). If a cephalometric radiograph is not available, the same view of the anterior maxilla may be obtained on a small, occlusal-sized film. This film is held vertically against the cheek and parallel to the sagittal plane of the skull. The X-ray tube is directed horizontally above and parallel to the occlusal plane from the opposite side of the face and at right-angles to the film. The result is called the tangential view and has the advantage of simplicity. This view is par­ ticularly useful in monitoring progress in the resolution of impacted incisors, during active treatment.

Radiographic Methods Related to the Diagnosis of Impacted Teeth  19 

(a)

(b)

Fig. 2.12  The true lateral and true occlusal views, taken together, provide all the information needed for an accurate positional assessment of crown and root in the three planes of space. (a) The periapical view (a true lateral in this case) of an impacted mandibular right second premolar shows the tooth to be tipped 60° distally from the vertical, with its incomplete apex at the correct height and mesio-distal location. (b) The true occlusal view shows the crown of the tooth to be lingual to the molar and the apex to be in the bucco-lingual line of the arch. The long axis of the tooth, proceeding from its ideally sited apex, can be described as rising at a 30° angle in a distal and lingual direction, to overlap the molar roots on the lingual side.

At the age that most patients first present with an impacted central incisor, around 8–10 years, the permanent canine teeth are unerupted and are located both well forward and high in the anterior maxilla. Thus, on the lateral cephalometric or tangential view, right and left canines will be impossible to distinguish from one another. The roots of the incisors, at the same height as the canines, as well as the superimposed images of the more inferiorly placed crowns of the erupted incisors and deciduous canines, will all be impossible to differentiate from one another and from any supernumerary teeth that may also be present. For this reason, the lateral view may be of limited value in cases where there is obstructive impaction, with minimal displacement. When gross displacement is present, however, the outline of the altered axial inclination and height of the tooth are usually possible to delineate, despite the considerable superimposition of other teeth. Nowhere is this view a greater asset than when a dilacer­ ate central incisor is present, since it separates out this malformed tooth superiorly from the root apices of the other teeth and from the permanent canines, because of its relative height (Figure 2.13). Furthermore, its morphology may be seen to best advantage from this aspect, which allows definitive and accurate diagnosis of the condition to be made, together with its precise relations vis-à-vis sur­ rounding structures. The lateral cephalogram/tangential view should be considered an essential requirement in radiographically recording the dilacerated central incisor. For maxillary canines, the lateral view is extremely useful. It should be remembered that most impacted maxillary canines are diagnosed in the full permanent dentition when all the other teeth have erupted. This permits clear radio­

Fig. 2.13  A dilacerated central incisor seen in a lateral cephalometric film.

graphic imaging of the canine, when it is sited at a higher level than the other teeth. A postero-anterior cephalometric film is used less rou­ tinely in orthodontics, but it offers the clinician the oppor­ tunity to view the maxilla in a different plane, the true postero-anterior view (Figure 2.11b), which is at rightangles to the lateral cephalogram. The overlap of structures of the base of the skull and the maxilla renders detail of individual teeth less clear, but a good postero-anterior radi­ ograph will show the height of both the crown and the root of a markedly displaced tooth, as with the lateral film. This view also shows whether the root apex of an ectopic poste­ rior tooth is in the line of the arch and how far the crown is deflected in the palatal direction. The bucco-lingual tilt of the long axis of the tooth will be plainly visible (Figure 2.11b). However, the view is less practical in the mandible,

20  Orthodontic Treatment of Impacted Teeth where the left and right sides of its V-shaped body converge as they proceed forward towards the anterior midline and are thus oblique to the central ray. There is usually excessive overlap, more radio-opaque bone and difficulty in discern­ ing even markedly bucco-lingually displaced teeth. For structures close to the midline, the panoramic view offers a very similar representation (Figure 2.11b, c) and a much clearer picture. Since this view is a rotational tomograph, it eliminates all structures that are either lingually or buccally outside the narrow focal trough at which it is aimed. An occlusal projection of the anterior maxilla (Figure 2.3) offers the possibility of viewing in the third plane of space, at right-angles to each of the two earlier radiographs, and recording the position of the displaced incisor or canine without overlap. However, for it to be of greatest value, it is important to project the X-ray beam through the long axis of the maxillary teeth, as we have just described. Any two of these three views (the lateral cephalogram or tangential view, the postero-anterior cephalogram and the true occlusal) will provide complete information regarding every aspect of the height, bucco-lingual and mesio-distal location of the crown and the root, and the degree of tilt of the long axis of the impacted tooth and its relation with neighbouring teeth. The postero-anterior cephalogram and the occlusal views, however, are not always as clear as is desirable, and they may need to be repeated or discarded. The lateral cephalometric or the tangential view in a case of bilateral canine impaction may create confusion, since one canine will be superimposed on the other and distin­ guishing them may be a problem, although other views will usually facilitate differentiation. Two identically oriented and superimposed canines (Figure 2.11) will obviously not need to be differentiated. It is emphasized that many of the radiographs that we take for other reasons should always be scrutinized for useful information regarding positions of unerupted teeth but, particularly regarding cephalo­ grams, whose principal aim is to measure and compare angles and distances on tracings of specific landmarks on the film; often these potentially valuable views are filed away without sufficient thought. From these projections, it is very easy to build up a threedimensional picture of the exact position and angulation of the impacted tooth and to define the type of movement that will be necessary to bring the tooth into alignment. When a composite mental reconstruction of the position of the unerupted tooth in space is built, the design of the appliance needed to resolve the impaction is simplified and fewer surprises are likely to be encountered. It is, however, a sine qua non in all these cases to examine a periapical view of the tooth to eliminate the possibility of local pathology, which could be missed on the extra-oral views. The foregoing description has covered the various methods available for envisioning the anatomical form and the three-dimensional location of unerupted teeth using plain film radiography. We have seen that, in order to

achieve an adequate picture of the relationships between the crowns of these teeth and the surrounding anatomic structures, including adjacent teeth, information gleaned from several different types of view needs to be put together to make up the complex picture. Nevertheless, even when enough information is available, mistakes and misdiag­ noses are sometimes made by experienced orthodontists [6], occasionally with serious repercussions for the patient. Is the same degree of precision in root apex location and three-dimensional root orientation essential for both the orthodontist and the surgeon? From the point of view of the oral surgeon, diagnosis of the position of the crown, buccal or palatal to the line of the arch, is generally all that is needed, regardless of whether the tooth is to be exposed for orthodontic alignment or extracted. The position of the root apex and the orientation of the long axis of the tooth are irrelevant for surgical exposure. If the tooth is to be extracted in one piece, careful dissection of the tissue sur­ rounding the crown and dislodging it with an elevator or extraction forceps will deliver the tooth, together with its root. Even if the root portion is sectioned and scheduled for extraction after removal of the crown portion, its general orientation and apex position can be determined by the anatomy and general orientation of the crown. For these reasons, many surgeons will rely solely on the tube shift parallax method of positional diagnosis for exposure or extraction of impacted teeth, and will do so with consider­ able confidence. From the point of view of the orthodontist, however, while the position of the crown is important, the position of the apex and the orientation of the long axis of the tooth are crucial. When the root apex of the impacted tooth is displaced, re-siting it in its correct position is fraught with difficulty technically and can only be done once the crown has been brought into its place in the arch and ligated into the main archwire. As we shall discuss in Chapter 6, root movement is the most damaging movement to the support­ ing tissues and has been shown to be one of the principal factors that most undermine the periodontal prognosis of the treated result [14–16]. An orthodontist cannot be expected to be confident in his/her ability to bring a tooth into full alignment if an accurate three-dimensional diag­ nosis of its position is not available. In the event, a surgical exposure may be attempted from the wrong side of the alveolus and unnecessary damage will ensue. Alternatively, the impacted tooth may be drawn in the wrong direction and will be brought into contact with the root of an adja­ cent tooth, which may lead to resorption of that root or to the blocking of further progress. The reader is referred to Chapter 12 for an illustrated description of failures and how most of these were due to positional misdiagnosis. Unfortunately, the above-mentioned plane film methods exhibit many shortcomings. This is particularly true in rela­ tion to the bucco-lingual plane. Undoubtedly, the most difficult aspect to define is the relative proximity of the

Radiographic Methods Related to the Diagnosis of Impacted Teeth  21  impacted tooth to the root of an adjacent tooth on which its image is superimposed in the bucco-lingual plane, as seen on a periapical, anterior occlusal, panoramic or cepha­ lometric film. Whether there is a small distance between them or whether the crown of the impacted tooth lies in a resorbed crater on the palatal or labial aspect of the root of an incisor may be impossible to determine using plane film radiography. As a result, an undiagnosed and severely resorbed tooth, with a poor long-term prognosis, may be mistakenly included as an integral but ‘weak link’ in the final scheme of the dentition in a projected treatment plan [17]. The relative accuracy of positional diagnosis using plain film radiography is, therefore, inadequate in many instances. While this is so, there can be no question that a good number of cases continue to be successfully treated, despite a lack of adequate imaging documentation that would be needed to make even an approximate positional diagnosis. In some cases, no serious attempt at definitive diagnosis of the position of the impacted tooth is made until the unsus­ pecting and potentially unfortunate patient is on the oper­ ating table. Computerized tomography The use of CT scanning was first proposed in the present context in the late 1980s [18, 19] to identify the exact posi­ tion of the palatally impacted canine, particularly when root resorption of the lateral incisor is suspected [20]. At that time, while its excellent potential for diagnosis of the position of impacted and supernumerary teeth was recog­ nized, the large dosage of radiation that routine CT imaging required was difficult to justify for all but the most complex and exceptional cases. Nevertheless, because of the relative inadequacy of plain film radiography, many of these cases escape the discovery that they are difficult and exceptional, a revelation that can only be ascertained when a CT scan has been performed. It has become quite clear, since writing the first edition of this text, that CT has found and established an important place in the planning of treatment of impacted teeth. Accurate three-dimensional (3-D) localization of the impacted tooth is immediately available from the 3-D views or by following the outlines of the individual teeth in suc­ cessive ‘cuts’ on the films. In this way, the exact relationships between the impacted teeth and their adjacent teeth can be seen along the entire lengths of the crowns and roots of each. Using this modality, it has become possible to improve the overall assessment of cases in which the impaction may best be resolved with orthodontic treatment and to suffi­ ciently separate them from those where the tooth is in an intractable position. Trial-and-error is slowly becoming a practice of the past [21, 22] since it is now possible to present a 3-D radiographic image of what the surgical field will look like when an impacted tooth is uncovered by the

oral surgeon. This helps to eliminate positional misdiagno­ sis and the undertaking of treatment for those relatively few cases in which the position and proximity of other teeth make it impossible to arrive at a successful conclusion to the treatment. Similarly, the axial (horizontal) and transaxial (vertical) ‘slices’ made at predetermined intervals provide informa­ tion in the bucco-lingual plane, which is largely impossible to discern with routine plane radiography. These views con­ tribute materially to the evaluation of the prognosis of the intended treatment outcome. Thus, the bucco-lingual prox­ imity of teeth and the existence and extent of oblique root resorption all become assessable, and these are important factors in deciding whether to undertake treatment and in determining choice of teeth for extraction. The prevalence of resorption of the roots of incisor teeth in association with an impacted canine was investigated by plain film radiography in a study performed in 1988 [19] and found to affect 12% of the individuals in the sample. When the same investigators repeated their study 12 years later, using spiral CT scanning [23], the number of affected individuals increased to 48%! There can be little doubt that this was due to this vastly improved diagnostic tool and to the fact that resorption of the buccal or palatal aspects of the roots of the incisor teeth cannot be seen on regular film. It is only when the buccal or palatal resorption has become sufficiently extensive to cause a change in the shape of the mesio-distal profile of the root that it may be suspected. Until then, this type of resorption may go undiagnosed on plain radiography films. CT offers advantages in assessing the proximity of the impacted tooth to an adjacent pathological entity and in evaluating aberration in the shape and appearance of the crowns and roots of teeth that are suspected of having become damaged or have suffered from abnormal develop­ ment due to past trauma [24]. Conventional spiral CT machines, as used in routine hospital practice for imaging various parts of the body, expose the body to an X-ray beam in the form of a progres­ sive spiral, encircling the body over a specific, defined area. This submits the patient to a high dose of ionizing radiation and is a subject for concern when considering its use in the present context. Just how large this dose is was evaluated by Dula et al. [25, 26] using what is referred to as a hypotheti­ cal mortality risk. In this assessment, the mortality risk associated with routine dental radiographs ranged between 0.05 and 0.3 × 10−6 units, depending on the type and number of films performed, while a CT scan of the dental area alone was assessed at 28.2 × 10−6 for the maxilla and 18.2 × 10−6 for the mandible. Cone beam computerized tomography More recently, digital volume tomographic (DVT) machines (Table 2.1), which use the cone beam principle (NewTom 9000TM and NewTom 3GTM, Italy; i-CATTM, Imaging

22  Orthodontic Treatment of Impacted Teeth Table 2.1  A comparison matrix of the important features of different cone beam computerized tomography machines. (Courtesy of Dr D Hatcher.) NewTom 9000®

New Tom 3G®

CB MercuRay®

Sensor type

Image intensifier

Image intensifier

Image intensifier

Gray levels (bits) Voxel size (mm3) Collimation Scan time(s) Dose type Frames/revolution Effective dose (µSv) Field of view Reconstruction shape

8 0.29 Limited 70 Pulsed 360 50 6 in diameter Sphere

12 0.2–0.4 Limited 40 Pulsed 360 44.7 4, 6, or 9 in diameter Sphere

12 0.2–0.4 Limited 10 Continuous 300 487 or 869 4, 6, or 9 in diameter Sphere

Iluma DentalCAT™

i-CAT™

Amorphous silicone flat panel 14 0.1–0.4 No 20 or 40 Continuous ? ? 17 cm Cylinder

Amorphous silicone flat panel 14 0.1–0.4 Yes 10, 20, or 40 Pulsed 150, 300, or 600 68.7 6–22 cm Cylinder

Sensor type. Image intensifiers are bulky, require a large space and structurally robust support. Image intensifiers have a lower signal/noise ratio than flat panel sensors. Signal is good and noise is bad. Gray levels. The number of gray levels is directly proportional to the image quality. 8 bits = 28 = 256 shades of gray, 12 bits = 212 = 4096 shades of gray and 14 bits = 214 = 16 384 shades of gray. The increase in the number of gray levels will give greater access to soft tissue detail. Voxel size. The reconstructed data are presented as voxel data. A voxel is the smallest element of a three-dimensional image. Each voxel possesses the following attributes: size, location, and gray level. Cone beam CT voxels are nearly isotopic, i.e. they have equal x, y, and z dimensions. Collimation. Collimation allows the operator to reduce the field of view (FOV) to the area of interest. A small FOV has the advantages of reducing the effective dose and reducing scatter (noise). Scan time. The main advantage for a short scan time is the potential for the reduction of motion artifact. Motion is a significant contributor to noise. Dose: pulsed or continuous. A pulsed dose results in a lower effective dose. Effective dose is a method for assessing radiation burden to the patient and allows a direct comparison between different radiation sources. It considers the absorbed dose in key tissue in and around the field of view. The absorbed dose is weighted by percent of body being imaged and by the sensitivity of the tissues being measured. In the case of the CB MercuRay, two different mA settings (10 and 15 mA) were used in the studies. For comparison, in maxillo-mandibular study by fan beam CT, the dose was reported to be 2100 µSv, and in a maxillary study was reported to the 1400 µSv. Frames/revolution. The frames are the number of acquired images, known as the raw data. The frame number is directly proportional to the signal generation. Field of view (FOV). FOV refers to the dimensions of the anatomic region being imaged. Using the image intensifier the FOV is linked to the voxel size. A larger FOV requires a larger voxel and therefore a lower resolution. The selected voxel size is independent of the FOV when using a flat panel sensor; therefore, a large FOV with a small voxel size can be used. Reconstruction shape. A cylindrical reconstruction fits the human head better than a spherical shape. Image quality. Image quality is related to several factors including: signal, noise, voxel size, and gray levels. The best-quality image has high signal, low noise, small voxel size, and a large number of gray levels.

Sciences International, USA; CB MercuRayTM, Hitachi Medical Corporation, Japan; 3D AccuitomoTM, J. Morita Mfg Corporation, Japan; Iluma DentalCATTM, IMTEC Imaging, USA; Promax 3D, Planmeca, Finland), have become available, in which an X-ray source and an image intensifier perform a single 360° rotation around the patient’s head during which raw data are acquired and, on every 10 steps of the rotation, a different projection of the skull is taken, starting from the anterior midline position. The projection is captured by an image intensifier and stored on a hard drive unit, and the raw data are transferred into axial (horizontal or parallel to the occlusal plane) views, which form their primary reconstruction. Subse­ quently, these are secondarily reconstructed into views in other directions, which include panoramic views at various depths and diverse (coronal, radial, sagittal) transaxial views. Furthermore, because of a 1:1 size relationship of the images to reality, valid measurement may be made directly on the films themselves [27]. As with the conventional spiral CT machines, 3-D views from any aspect may also be

reconstructed, although the resolution and definition of soft tissues are not quite as clear. With the more recent advances in the development of these machines, companies now offer the possibility of seri­ ally moving through the consecutive horizontal or vertical ‘slices’, on a personal computer screen and under the control of the mouse. In this way the intimate details of the crown and root relationships of the impacted tooth and adjacent structures may be followed and resorbed areas clearly rec­ ognized. Similarly, the 3-D views of the impacted tooth within the erupted dental arch may be shown as a continu­ ous animated movie, showing the teeth (stripped of all soft tissue and bone) from all angles. As a result of these sophis­ ticated features and improvements with the cone beam method, a renewed investigation of cases of maxillary canine impaction in relation to detectable root resorption recorded 66.7% resorption in lateral incisors and 11.1% in central incisors [27] (Figures 2.14 and 2.15). One of the highlights of this machine is that the operator may use the program to trace the course of the inferior

Radiographic Methods Related to the Diagnosis of Impacted Teeth  23 

(a)

(b)

(c)

(d)

Fig. 2.14  A comparison of information available from plain film radiographs with that from cone beam computerized tomography. (a–c) The panoramic, periapical and lateral cephalometric radiographs show in impacted maxillary canine, in close relation to the roots of the lateral incisor and the first premolar. There is evidence of root resorption of the lateral incisor. The canine has been diagnosed as buccal, but its relation with the premolar is undiagnosed. Its apex appears superior to that of the premolar. (d) A horizontal (axial) cut shows the tip of the crown of the canine at the level of the middle of the incisor roots and in the line of the arch. (e) A higher parallel axial cut shows the horizontal cut obliquely imaging the canine, indicating its crown to be buccal and its root oriented across the ridge to the palatal of the premolar roots and at the same level. (f, g) Vertical (transaxial) views show the labio-lingual and height relation between the canine and it immediate neighbours and the site adds severity of the resorption of the incisor root. (h, i) The three-dimensional view of the area shows an accurate visualization of what the surgical field will look like, when the exposure is undertaken.

alveolar canal on the imaged panoramic view with a red marker and then generate vertical or horizontal cuts which will depict the inferior dental canal as a red dot or line. This is normally used in planning the placement of dental implants. It may also be used in the present context to define the relationship between the inferior dental nerve and a severely and deeply infra-occluded/impacted molar or premolar, whose roots are in close proximity to it. In addition, accurate 1:1 measurement may be made on the films to assist in overall orientation [28]. The Israeli group published the first clinical article that describes CBCT and its use in the accurate positional diag­

nosis of impacted teeth [29]. In that article, the enormous advantages to be gained with this method are highlighted, together with examples whereby seemingly impossible positions of teeth may be clearly identified and appropriate biomechanical solutions devised to successfully overcome them. The information obtainable with plane film radiog­ raphy is very poor by comparison and is the reason for failure in many of the more unusual cases [30–32]. The greatest advantage that the cone beam volumetric machine has over conventional CT machines is that its radiation dosage is only a fraction of that emitted by the conventional machine. According to one published source,

(e)

(f)

(g)

(i) Fig. 2.14  (Continued )

(h)

Radiographic Methods Related to the Diagnosis of Impacted Teeth  25 

(a)

(b)

(c) (d)

(f)

(e)

#13 #12 #52 (g)

#12

#11

#12

#52 (h)

(i)

Fig. 2.15  A case in which maxillary canines and the right lateral incisor were impacted, but the bucco-lingual relations and axial inclinations between these teeth need to be evaluated. (Courtesy of Dr M. Yitschaky.) (a) A periapical view of the maxillary midline area showing the impacted lateral incisor. (b) A more steeply angled periapical view confirms the right lateral incisor to be palatal to the root of the central incisor, using the principles of vertical parallax. (c) Using Chaushu’s method for this anterior portion of a panoramic film of the same patient, the canines are also palatally displaced. However, these views are inadequate to determine the complicated bucco-lingual relations and axial inclinations of the six anterior teeth. (d–f) Consecutive transaxial cuts show the vertical and bucco-lingual relationship between the right permanent canine (#13) and the adjacent lateral incisor (#12), deciduous canine (#53) and central incisor (#11). (g–i) show 3-D views from the right side, the front and the palatal aspect, to determine the root of the lateral incisor to be protruding labially and its crown palatal to the central incisor. The canine is palatal to the root but labial to the crown of the lateral incisor. The left permanent canine is also palatally displaced.

26  Orthodontic Treatment of Impacted Teeth the DVT machine irradiates the patient at approximately 20% of the regular CT machine [33], while another source [34] has quoted the radiation dose for the mandible as 8580 mR for the conventional machine, as against 140 mR for the DVT machine. An issue of the Journal of the Californian Dental Association reported on the 2002 Inaugural Conference of the (California) Coast Conference on Orthodontic Advances in Science and Technology, and the articles in that volume were devoted to the various aspects of cone beam volume tomography. In these reports, the level of the patient’s radi­ ation dose is variously described as ‘similar to standard dental radiology’ [35], ‘an absorbed dose that is comparable to other dental surveys’ [36] and ‘is 50.3 µSv (NewTom 9000), while that of a dental panoramic film ranges from 2.9–9.6 µSv and a complete mouth series ranges from approximately 33–84 µSv and 14–100 µSv’ [37]. What do these figures mean to the lay public? With our responsibility as dentists to convey information in a manner understandable to those requesting our treatment and in order to obtain informed consent, it is imperative to present the issue in its context, without blinding the patient with scientific data. Thus, it may be more pertinent to use the comparison that (a) the average man-in-the-street receives a daily dose of about 8 µSv per day or 2700 µSv per year from the environment [38] and (b) flying from New York to Tokyo by the transpolar route exposes the passenger to ionizing (cosmic) X-rays of approximately 150 µSv and from New York to Seattle of approximately 60 µSv [39]. This may be put more explicitly for the benefit of the clini­ cian in practice in Table 2.2, which presents helpful com­ parisons of dosages for commonly used dental and medical radiographs with CBCT and spiral CT, as compared to the natural background radiation to which we are passively subjected in our daily lives and, at the same time, couched in terms readily comprehensible to the lay public. In the past and with the availability of only the very high radiation dosage, traditional spiral CT machines, there was Table 2.2  Effective radiation doses (after ref. [40], reproduced with permission) Examination Dental   Panoramic   Cephalogram   Occlusal film   Bitewing   Full-mouth series   TMJ series   CBCT exam Medical   Chest X-ray   Mammogram   Medical CT

Exposure (µSv)

3–11 5–7 5 1–4 30–170 20–30 40–135 100 700 8,000

Equivalent natural background radiation 1/2–1 day 1/2–1 day 1/2 day 1/2 day 4–21 days 3–4 days 4–17 days 10–12 days 88 days 1,000 days (3 years)

little justification for the routine use of this method in the diagnosis of impacted teeth in any but the clinically most difficult cases. Nevertheless, given the amount of informa­ tion that may be provided by CT methodology and the reduction in radiation that is now possible with these newer machines, the significant reduction in the risk/benefit ratio has brought the method to within much more acceptable limits. For plain film radiography to provide a comparable level of positional information, a number of different views would need to be taken and, together, the accumulated level of radiation that these would generate is of the same order as that emitted by the new CT machines. Panoramic radio­ graphs are already produced by the CBCT machines, among the full range of views available. The CT is generally focused on a rotating narrow band of tissue, the focal trough, at a fixed distance from the beam source, at the same time elim­ inating all structures that are in front of or behind this trough. Thus, while a traditional panoramic film, which is generally focused on a broader band of tissue, will reveal a labially or palatally placed ectopic supernumerary tooth, it will be understood that if this body were to lie outside this trough, either in a CBCT or in a panoramic view, it will not appear on the image. The more recent versions of CBCT machines have the capacity to produce standardized cephalometric views gen­ erated from the same scan that will have produced the panoramic view and the 3-D views. This has led to a broad­ ening of the services and to a streamlining of the radio­ graphic records available to the orthodontist, which has in turn led serendipitously to the discovery of incidental find­ ings that had not shown in the patient’s plane film records in up to 30% of the orthodontic cases seen in one study [41]. More pertinently, in another study of patients with impacted maxillary canines, 43.7% of the initially proposed treatment plans, based initially on plain film radiographs, were amended in the light of subsequent findings seen on the CBCT images [42]. The main reason for the revised treatment plans was linked to the demonstrable superiority of CBCT over plane film radiography in relation to the bucco-lingual dimension in general and to the many cases where existing incisor root resorption was diagnosed on the CBCT but missed on the plane films. CBCT represents state-of-the-art technology with direct relevance to the determination of macroscopic anatomy and accurate positional diagnosis of impacted teeth. The machinery is not beyond the financial means of most radi­ ology institutes, small diagnostic centres and dental school radiology departments, its usefulness to the orthodontist and surgeon is manifest, its level of emitted ionizing radia­ tion is low and the cost to the patient affordable. Accordingly, it must now be considered a recommended procedure for many of the cases that are discussed within the context of this book. But there is also an inherent danger with this type of comprehensive imaging. The means of presentation of the

Radiographic Methods Related to the Diagnosis of Impacted Teeth  27  results of the CBCT scan are very attractive to the layman and several of the films may be undertaken to impress the orthodontic patient, who may request a copy of the beforeand-after portfolio as a souvenir of his/her orthodontic treatment and outcome. In today’s world, this can easily become part of the ‘hard sell’ and a means of attracting new patients. So the danger is that the stage may be set for the production of a whole gamut of films for the sake of ‘com­ pleteness’, many of which may be superfluous to the clinical needs of the patient, and to achieve this the patient will be subjected to a large overdose of ionizing radiation. What is ALARA? The risks attached to any form of radiation are only seen many years later in its stochastic effects, which include a higher susceptibility of the individual to various forms of cancer. It is known that these effects are amplified with increased exposure and that children are more susceptible than adults. Yet it is the children and young adults who are the main targets of the population for the provision of orthodontic treatment. It is therefore incumbent on the practitioner to reduce this exposure to the minimum, while deriving a maximum of information, adequate to the problem in hand. This is ALARA – as low as reasonably achievable. As we have already noted, there is ample documentation that cone beam computerized tomography will irradiate the patient less – possibly far less – than a conventional CT machine and that the many different CBCT machines avail­ able on the market today have widely differing outputs of radiation [43–45] for similar results. It stands to reason, therefore, that when a CT scan is justified, it is because plane film radiography cannot maximize the information needed for that patient. It should also be performed using the CBCT machine with the lowest radiation specifications, and the irradiated area should be limited as much as possible.

References   1.  Seward GR. Radiology in general practice IX. Unerupted maxillary canines, central incisors and supernumeraries. Br Dent J 1968; 115: 85–91.   2.  Hunter SB. The radiographic assessment of the unerupted maxillary canine. Br Dent J 1981; 150: 151–155.   3.  Mason RA. A Guide to Dental Radiography, 2nd ed. Bristol: Wright PSG, 1982.   4.  Ong A. An alternative technique to the vertex/true occlusal view. Am J Orthod Dentofac Orthop 1994; 106: 621–626.   5.  Clark CA. A method of ascertaining the relative position of unerupted teeth by means of film radiographs. Proc Roy Soc Med (Sec. Odont) 1910; 3: 87–90.   6.  Armstrong C, Johnston C, Burden D, Stevenson M. Localizing ectopic maxillary canines – horizontal or vertical parallax? Eur J Orthod 2003; 25: 585–589.   7.  Jacobs SG. Localisation of the unerupted maxillary canine. Aust Orthod J 1986; 9: 313–316.   8.  Jacobs SG. Exercises in the localisation of unerupted teeth. Aust Orthod J 1987; 10: 33–35, 58–60.

  9.  Nohadani N, Pohl Y, Ruf S. Displaced premolars in panoramic radiography—fact or fallacy? Angle Orthod 2008, 78: 309–316. 10.  Chaushu S, Chaushu G, Becker A. The use of panoramic radiographs to localize maxillary palatal canines. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999; 88: 511–516. 11.  Chaushu S, Chaushu G, Becker A. Reliability of a method for the localization of displaced maxillary canines using a single panoramic radiograph. Clin Orthod Res 1999; 2: 194–199. 12.  Wolf JE, Mattila K. Localization of impacted maxillary canines by panoramic tomography. Dentomaxillofac Radiol 1979; 8: 85–91. 13.  Fox NA, Fletcher GA, Horner K. Localising maxillary canines using dental panoramic tomography. Br Dent J 1995; 179: 416–420. 14.  Kohavi D, Zilberman Y, Becker A. Periodontal status following the alignment of buccally ectopic maxillary canine teeth. Am J Orthod 1984; 85: 78–82. 15.  Becker A, Kohavi D, Zilberman Y. Periodontal status following the alignment of palatally impacted canine teeth. Am J Orthod 1983; 84: 332–336. 16.  Kohavi D, Becker A, Zilberman Y. Surgical exposure, orthodontic movement and final tooth position as factors in periodontal break­ down of treated palatally impacted canines. Am J Orthod 1984; 85: 72–77. 17.  Becker A, Chaushu S. Long-term follow-up of severely resorbed max­ illary incisors following resolution of etiologically-associated canine impaction. Am J Orthod Dentofacial Orthop 2005; 127: 650–654. 18.  Ericson S, Kurol J. CT diagnosis of ectopically erupting maxillary canines – a case report. Eur J Orthod 1988; 10: 115–120. 19.  Ericson S, Kurol J. Resorption of maxillary lateral incisors caused by ectopic eruption of canines. Am J Orthod Dentofacial Orthop 1988; 94: 503–513. 20.  Ericson S, Kurol J. Radiographic examination of ectopically erupting maxillary canines. Am J Orthod Dentofacial Orthop 1987; 91: 483–492. 21.  Odegaard J. The treatment of a Class I malocclusion with two hori­ zontally impacted maxillary canines. Am J Orthod Dentofacial Orthop 1997; 111: 357–365. 22.  Becker A. Comment about making outcome of treatment more pre­ dictable. Am J Orthod Dentofacial Orthop 1997; 112: 17A–19A. 23.  Ericson S, Kurol PJ. Resorption of incisors after ectopic eruption of maxillary canines: a CT study. Angle Orthod 2000; 70: 415–423. 24.  Bodner L, Bar Ziv J, Becker A. Image accuracy of plain film radiogra­ phy and computerized tomography in assessing morphological abnor­ mality of impacted teeth. Am J Orthod Dentofacial Orthop 2001; 120: 623–628. 25.  Dula K, Mini R, van der Stelt PF et al. Hypothetical mortality risk associated with spiral computed tomography of the maxilla and man­ dible. Eur J Oral Sci 1996; 104: 503–510. 26.  Dula K, Mini R, van der Stelt PF, Buser D. The radiographic assess­ ment of implant patients: decision-making criteria. Int J Oral Maxillofac Implants 2001; 16: 80–89. 27.  Walker L, Enciso R, Hatcher DC, Mah J. Three-dimensional analysis of impacted canines using volumetric imaging. Am J Orthod Dentofacial Orthop 2005; 125: 418–423. 28.  Mah J, Hatcher D. Three-dimensional craniofacial imaging. Am J Orthod Dentofacial Orthop 2004; 126: 308–309. 29.  Chaushu S, Chaushu G, Becker A. The role of digital volume tomog­ raphy in the imaging of impacted teeth. World J Orthod 2004; 5: 120–132. 30.  Mah JK, Alexandroni S. Cone-beam computed tomography in the management of impacted canines. Semin Orthod 2010; 16: 199–204. 31.  Becker A, Chaushu S, Casap-Caspi N. CBCT and the orthosurgical management of impacted teeth. J Am Dent Assoc 2010;141(10 suppl): 14S-18S. 32.  Becker A, Chaushu G, Chaushu A. An analysis of failure in the treat­ ment of impacted maxillary canines. American Journal of Orthodontics & Dentofacial Orthopedics 2010; 137: 743–754. 33.  Mozzo P, Procacci C, Tacconi A, Martini PT, Andreis IA. A new volu­ metric CT machine for dental imaging based on the cone-beam tech­ nique: preliminary results. Eur J Radiol 1998; 8: 1558–1564. 34.  Mah JK, Danforth RA, Bumann A, Hatcher D. Radiation absorbed in maxillofacial imaging with a new dental computed tomography device. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003; 96: 508–513.

28  Orthodontic Treatment of Impacted Teeth 35.  Danforth RA, Dus I, Mah J. 3-D volume imaging for dentistry: a new dimension. J Calif Dent Assoc 2003; 31: 817–823. 36.  Hatcher DC, Dial C, Mayorga C. Cone beam CT for presurgical assessment of implant sites. J Calif Dent Assoc 2003; 31: 825–833. 37.  Mah J, Enciso R, Jorgensen M. Management of impacted cuspids using 3-D volumetric imaging. J Calif Dent Assoc 2003; 31: 835–841. 38.  Health Protection Agency. Ionising Radiation Exposure of the UK Population: Review, Ref: HPA-RPD-001. Radiation Protection Division, Chilton, Oxon, UK: 2005. 39.  Barish RJ. In-flight radiation exposure during pregnancy. Obstet Gynecol 2004; 103: 1326–1330. 40.  Mah J. Cone Beam CT Radiography: A Certification Program for Dentists. Appendix I as part of a CE Course Manual entitled “ Copyright 2010. eDental Academy, Las Vegas, NV.

41.  Cha J-Y, Mah J, Sinclair P. Incidental findings in the maxillofacial area with 3-dimensional cone-beam imaging. Am. J Orthod Dentofac Orthop, 2007; 132: 7–14. 42.  Bjerklin K, Ericson S. How a computerized tomography examination changed the treatment plans of 80 children with retained and ectopi­ cally positioned maxillary canines. Angle Orthod, 2006; 76: 43–51. 43.  Tsiklakis K, Dontaa C, Gavala S, Karayianni K, Kamenopoulou V, Hourdakis CJ. Dose reduction in maxillofacial imaging using low dose Cone Beam CT. Eur J Radiol 2005, 56: 413–417. 44.  Brooks SL. CBCT Dosimetry: orthodontic considerations. Semin Orthod 2009, 15: 14–18. 45.  Silva MAG, Wolf U, Heinicke F, Bumann A, Visser H, Hirsch E. Conebeam computed tomography for routine orthodontic treatment plan­ ning: a radiation dose evaluation. Am J Orthod Dentofac Orthop 2008; 133: 640.

3 Surgical Exposure of Impacted Teeth (In Collaboration with Arye Shteyer and Joshua Lustmann)

Aims of surgery for impacted teeth

30

Surgical intervention without orthodontic treatment

30

The surgical elimination of pathology

32

The principles of the surgical exposure of impacted teeth

33

Partial and full-flap closure on the palatal side

40

Buccally accessible impacted teeth

40

A conservative attitude to the dental follicle

42

Quality-of-life issues following surgical exposure

45

Cooperation between surgeon and orthodontist

48

The team approach to attachment bonding

49

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

30  Orthodontic Treatment of Impacted Teeth

Aims of surgery for impacted teeth In the past, the decision on how a particular impacted tooth should be treated was usually made by the oral surgeon and, by and large, the alternatives were decided and stagemanaged by him. This situation has changed in recent years. Prior to the 1950s, few orthodontists were prepared to adapt their skills and their ingenuity to the task of resolving the impaction of maxillary canines and incisors. Accordingly, the orthodontists themselves referred patients to the oral surgeon, who would decide if the impacted tooth could be brought into the dental arch. Where the circumstances were potentially favourable, the tooth would be surgically exposed and, when the surgical field was displayed fully, the surgeon would make his assessment of the prognosis of the case, and decide and act solely in accordance with his own judgement. In this way, many potentially retrievable impacted teeth were scheduled for extraction. There are no surgical methods, other than transplantation, by which positive and active alignment of an impacted tooth may be carried out. The best a surgeon can do is to provide the optimal environment for normal and unhindered eruption and then hope that the tooth will oblige. In the past and with this in mind, therefore, those teeth that were considered worth trying to recover were widely exposed and packed with some form of surgical or periodontal pack to protect the wound during the healing phase and to prevent re-healing of the tissues over the tooth. For a variety of reasons, several other steps were taken, depending on the preferences and beliefs of the operator, with the aim of providing that ‘extra something’ that would improve the chances of spontaneous eruption still further. These measures were often very empirical in nature and included one or more of the following: clearing the follicular sac completely, down to the • cemento-enamel junction (CEJ) area; clearing the bone the tooth, down to the CEJ • area, to dissect outaround and free the entire crown and the coronal portion of the root of the impacted tooth; ‘loosening’ the tooth by subluxating it with an elevator; bone channelling in the desired direction of movement of the tooth; packing gauze or hot gutta percha into the area of the CEJ, under pressure, in order to apply force to deflect the eruption path of the tooth in a particular direction.

• • •

In those years, few patients were referred to the orthodontist until full eruption had been achieved, and the tooth then needed only to be moved horizontally into line with its neighbours. Up to that point, the problem was consi­ dered to be within the realm of the oral surgeon. In many cases, ‘success’ in achieving the eruption of the tooth was pyrrhic and often subordinated to failure of a different kind, namely the periodontal condition of the newly

erupted tooth and its survival potential – its prognosis. This was the inevitable result of the aggressive and overenthusiastic surgical techniques that had been used, specifically those listed above, which typically left the tooth with an elongated clinical crown, a lack of attached gingiva and a reduced alveolar crest height [1–6].

Surgical intervention without orthodontic treatment We come across cases in which the only clinical problem relates to the impacted tooth, the occlusion and alignment being otherwise acceptable. For these patients, the following question needs to be addressed: what surgical methods are available that may be expected to provide a more or less complete solution without orthodontic assistance? To be in a position to answer this question, it is necessary to provide a description of the position of the teeth that will respond to this kind of treatment. Exposure only A superficially placed tooth, palpable beneath the bulging gum, is an obvious candidate. This type of tooth may be seen in the maxillary canine area (Figure 3.1a), but also in the mandibular premolar area (see Figure 1.8) and the maxillary central incisor area, usually where very early extraction of the deciduous predecessor was performed while the immature permanent tooth bud was still deep in the bone and unready for eruption. Healing occurred, the gum closed over and the permanent teeth were unable to penetrate the thickened mucosa [7, 8]. Removing the fibrous mucosal covering or incising and resuturing it to leave the incisal edges exposed (Figure 3.2) will generally lead to a fairly rapid eruption of the soft tissue impacted tooth, particularly in the maxillary incisor area. The more the tooth bulges the soft tissue, the less likely is a reburial of the tooth in healing soft tissue and the faster is the eruption. Exposure with pack Taking this one step further, we will understand that a less superficial tooth requires a more radical exposure procedure and may need a pack to prevent the tissues from re-healing over the tooth. While the surgeon may be rewarded with spontaneous eruption, this will take longer and a compromised periodontal result should be expected (Figure 3.3). We have defined over-retained deciduous teeth as teeth still present in the mouth when their permanent successors have reached a stage of root development that is compatible with their full eruption. These deciduous teeth may then be considered as obstructing the normal development which would be expected to proceed in their absence. The deciduous teeth should be extracted, but provision should be made to encourage the permanent teeth to erupt quickly.

Surgical Exposure of Impacted Teeth  31 

(a) (a)

(b)

(b)

Fig. 3.2  (a) Soft tissue impaction of maxillary central incisors. (b) Apical repositioning of both labial and palatal flaps to leave the incisor edges exposed.

(c) Fig. 3.1  (a) A 16-year-old female exhibits an unerupted maxillary left canine, which has been present in this position for two years and has not progressed. (b) The tooth was exposed and the flap, which consisted of attached gingiva, was apically repositioned. (c) At nine months post-surgery, the tooth has erupted normally. (Courtesy of Professor L. Shapira.)

Fig. 3.3  Following exposure and packing the tooth has erupted spontaneously, but the bone level is compromised.

32  Orthodontic Treatment of Impacted Teeth Many of these permanent teeth with delayed eruption are abnormally low in the alveolus and are in danger of becoming reburied by the healing tissue of the evacuated socket of the deciduous tooth. Accordingly, the crowns of the teeth should be exposed to their widest diameter and a surgical or periodontal pack placed over them and sutured in place for 2–3 weeks. This will encourage epithelialization down the sides of the socket and, generally, prevent the reformation of bone over the unerupted tooth. Most surgeons and periodontists today will use a proprietary pack, such as CoePak™, to maintain the opening which, at the same time, acts as a dressing for the wound. A careful assessment of the space requirement should be made in these cases and consideration given to the need for space maintenance. It should be remembered that space loss in the mixed dentition may often be very rapid, and the erupting tooth may be arrested in its progress by its proximal contact with the adjacent teeth. Alternatively, particularly with regard to maxillary canines, placement of a removable acrylic plate, which is prepared before surgery, can be used to hold in a small pack over the exposed tooth [9]. Exposing and packing has recently been reintroduced and recommended for the treatment of severely palatally displaced maxillary canines [10]. When this is done, spontaneous resolution of even quite severe displacements has been claimed to occur in most cases, in the months that follow. This takes the form of at least partial eruption through the surgically created and pack-maintained opening and permits relatively easy access for attachment bonding and subsequent alignment of the tooth when appliance therapy is later initiated. Exposure with pressure pack Mesial impaction of a mandibular second permanent molar beneath the distal bulbosity of the first permanent molar is analogous to the more common mesial impaction of a third molar beneath the distal of the second. In either case, and in its mildest form, it is a condition that may sometimes respond to surgical intervention and packing only. This involves exposure of the occlusal surface of the tooth and the deliberate wedging of the pack in the area between the two teeth and leaving it there for 2–3 weeks. During this time, the pressure will often succeed in eliciting a distal movement of the impacted molar, which may then erupt more freely when the pack is removed. The degree of control available to the operator in judging the amount of pressure applied and the extent to which the pack interferes periodontally is minimal, although damage to the periodontium of the two adjacent teeth is possible. Success in bringing about an improved position of the tooth may thus not be matched by the health of its supporting structures. Others have used brass wire [11] or elastic separators to apply a similar disimpacting force.

The surgical elimination of pathology Soft tissue lesions In Chapters 8 and 11 we shall refer more specifically to benign tumours and cysts. Surgery is the only treatment that is indicated for these conditions, in the first instance. This should be performed without delay, if only for reasons of obtaining biopsy material to confirm the innocence of a tentative diagnosis. Orthodontic treatment should be suggested then, but begun only after a filling-in of bone has occurred. At that point, there will be an improvement of the positions of the grossly displaced teeth, together with an improvement of the bony defect that will be evident in the anatomy of the alveolar bone in the area. However, this may take many months to occur. In the interim, the preparation of the patient for the proposed orthodontic treatment may be undertaken, which must begin with seeing positive results from a preventive dental health programme aimed at eliminating marginal gingival inflammation and reducing the caries incidence for that patient. Hard tissue obstruction Obstructive impaction invites the logical step of removing the offending body causing the non-eruption. This is performed by the surgeon and, on many occasions, it is without recourse to orthodontic assistance and enjoys varying degrees of success. In Chapter 5 we shall refer to the reliability of spontaneous eruption, following the various surgical procedures involved in the treatment of impacted incisors. For the present discussion, we must recognize that there is a significant number of cases in which eruption does not occur in a reasonable time-frame. Following the removal of the obstruction, be it a supernumerary tooth, an odontome, residual deciduous roots or an infra-occluded primary tooth, the position of most unerupted teeth improves with time. However, many of these teeth do not erupt without assistance due to their severe displacement, which is a result of the existence of the erstwhile obstruction and the healing tissues. A hard tissue body is generally made up of the dental tissues and, with its accompanying dental follicle, occupies much space. This causes a gross displacement of the developing tooth bud of the normal tooth, which is true in terms of both overall distance from its normal location and the usually marked deflection of the orientation of its long axis. Thus, the root or the crown of the tooth may be deflected mesially, distally, lingually or buccally, or displaced superiorly (in the upper jaw) or inferiorly (in the lower), compromising its chances for spontaneous eruption. Abnormally shaped roots may develop in the cramped circumstances in which they find themselves between the displacing influence of the pathological entity and the adjacent teeth, on the one hand, and the floor of the nose or lower border of the mandible [12], on the other. Teeth with abnormally

Surgical Exposure of Impacted Teeth  33  shaped roots may have deviated eruption paths and do not always erupt spontaneously, although they may be successfully erupted with orthodontic appliances, provided their periodontal ligament (PDL) is normal. Non-eruption of an impacted tooth disturbs the eruption pattern of the adjacent teeth, which then assume abnormal relationships to one another, usually characterized by space reduction and tipping. This then provides a secondary physical impediment to the eruption of the impacted tooth.

next. The risk is that a poor biomechanical auxiliary, insufficient force levels or missed appointments may cause the exercise to founder, due to the re-establishment of the ankylosis bridge.

Infra-occlusion As we shall discuss in Chapter 8, infra-occluded permanent teeth are usually ankylosed to the surrounding bone and as such cannot respond to orthodontic traction. In many cases, the ankylosed area of root is minute and may be easily broken by a deliberate, but gentle luxation of the tooth. This is usually performed with an elevator or extraction forceps and is done in such a way as to loosen the rigid connection of the bony union, which is unbending. The tooth is not removed from its socket, nor is the principal aim even to tear the periodontal fibres. The purpose is to bring the tooth to a higher degree of mobility, beyond that characteristic of a normal tooth. Unfortunately, the fate of the tooth that has undergone this procedure is usually a rehealing and reattachment of the ankylotic connection, leading to a return to the original situation. Accordingly, this approach can only be successful if a continuously active traction force is applied to the tooth from the time of its luxation. This force may then act to modify the rehealing of bone due to a localized microcosm of distraction osteogenesis [13, 14] that it causes. If the range of force is small and loses its potency between visits for adjustment, re-ankylosis will result and the tooth will not move. Thus, to be effective, it must be of sufficient magnitude to cause distraction and of sufficient range to remain active between one visit for adjustment and the

The open eruption technique Historically, the first method used to uncover impacted teeth left the tooth exposed to the oral environment, while surrounded by freshly trimmed soft tissue of the palate or labial oral mucosa, following the removal of the mucosa and bone actually covering the tooth. This is known as the open eruption technique and it may be performed in two ways. The window technique involves the surgical removal of a circular section of the overlying mucosa and the thin bony covering. For most labially displaced teeth, due to their height, this entire surgical procedure would most likely only be possible above the level of attached gingiva (Figure 3.4), in the mobile area of the oral mucosa. Notwithstanding, it is clear that this is the simplest, most conservative and most direct manner to expose a tooth which is palpable immediately under the oral mucosa and it may often be accomplished with surface anaesthetic spray only. An attachment may then be bonded to the tooth and orthodontically encouraged eruption may proceed without delay, to complete its alignment within a very short time. While this obviously represents a significant advantage in the treatment of a young patient, the long-term outcome of the procedure will be characterized by a muco-gingival attachment on the labial side of the tooth which is not of attached gustatory epithelium, but

(a)

The principles of the surgical exposure of impacted teeth In general there are two basic approaches to surgically exposing impacted teeth, described below.

(b)

Fig. 3.4  (a) A high buccal canine exposed by circular incision of the sulcus mucosa. (b) Following alignment, the oral mucosa is attached directly to the gingiva. (Courtesy of Dr G. Engel.)

34  Orthodontic Treatment of Impacted Teeth rather a mobile, thin, oral mucosa that does not function well as a marginal tissue, as has been widely documented in the periodontal literature. The only situation in which this exposure procedure is clinically advantageous is when there is a very wide band of attached gingiva and where a labially impacted tooth is situated well down in this band, such that a simple removal of the tissue overlying the crown will still leave 1–2 mm of bound epithelial attachment inferior to the free, movable, oral mucosal lining of the sulcus. By contrast, the palatal mucosa is very thick and tightly bound down to the underlying bone. Thus, no parallel precautions need to be made to ensure a good attachment for the final periodontal status of a palatally impacted tooth, following its eruption into the palate. When the window technique is used on the palatal side, the cut edges of the wound need to be substantially trimmed back and the dental follicle removed to prevent re-closure of the very considerable width of palatal soft tissue over the exposed tooth (see Figure 6.29). For a deeply buried palatal canine, the exposure will additionally need to be maintained using a surgical pack. The apically repositioned flap is an alternative way of performing an open exposure technique on the buccal side. It is aimed at improving the periodontal outcome by ensuring that attached gingiva covers the labial aspect of the erupted tooth in the final instance. This is done by raising a labial flap, taken from the crest of the ridge, and relocating it higher up on the crown of the newly exposed tooth. This method, a recognized and accepted procedure in periodontics, was first described in the context of surgical and orthodontic treatment of unerupted labially displaced teeth by Vanarsdall and Corn [15]. In their method, and in the absence of the deciduous canine, a muco-gingival flap, which incorporates attached gingiva, is raised from the crest of the ridge (Figure 3.1). If a deciduous canine is present, the flap is designed to include the entire area of buccal gingiva that invests it, and the deciduous tooth itself is extracted. In either case, the flap is detached from the underlying hard tissue some way up into the sulcus, to expose the canine. The flap is then sutured to the labial side of the exposed crown of the permanent canine, to cover the denuded periosteum and overlie its cervical area, while the remainder of the crown remains exposed. Subsequent eruption of the tooth is accompanied by the healing gingival tissue and, when the tooth takes up its final position in the arch, it will be found to be invested with a good width of attached gingiva. This particular method of exposure is best suited to buccally/labially impacted teeth which are situated above the band of attached gingiva, but which are not displaced mesially or distally from their place in the dental arch. If the case presents with more than a minor degree of horizontal displacement in the sagittal plane, a raised and full thickness soft tissue flap will denude the alveolar bone cov-

ering the adjacent tooth to an unacceptable degree, contraindicating the use of this surgical modality. In order to overcome this, a partial thickness surgical flap may be raised, which leaves the donor area invested with a connective tissue cover [16], which will heal over by epithelial proliferation. With any form of open exposure surgery, the tooth acquires a new gingival margin which comprises the cut edge of gingival tissue, which will heal in this position and will move with the tooth as it is drawn down into its place in the arch. While the periodontal parameters may be very satisfactory, the appearance of the tissues surrounding the aligned tooth at the end of treatment by this method lacks a completely natural look and it is usually possible to distinguish the previously affected tooth with ease, even several years later (Figure 3.8). The closed eruption technique The alternative approach to surgical exposure, the closed eruption technique, has an attachment placed at the time of the exposure and the tissues fully replaced and sutured to their former place, to re-cover the impacted tooth. This was described by Hunt [17] and McBride [18], although it seems to have been in use earlier [19, 20], and it is a procedure that may be used regardless of the height or mesiodistal displacement of the tooth. For a buccally impacted tooth, a surgical flap is raised from the attached gingiva at the crest of the ridge, with suitable vertical releasing cuts, and elevated as high as is necessary to expose the unerupted tooth. An attachment is then bonded and the flap fully sutured back to its former place. The twisted stainless steel ligature wire or gold chain, which is preferred by some clinicians, which has been tied or linked to the attachment, is then drawn inferiorly and through the sutured edges of the fully replaced flap. The surgical wound is, therefore, completely closed and the exposed tooth and its new attachment are sealed off from the oral environment. Spontaneous eruption is less likely to occur than when the tooth remains exposed following apical repositioning, and active orthodontic force will probably need to be applied to the tooth to bring about its eruption. Traction is then applied to the twisted stainless steel ligature or gold chain to bring about the full eruption of the tooth [18, 21, 22]. In this method, the tooth progresses towards and through the area of the attached gingiva several weeks or months after complete healing of the repositioned surgical flap has occurred and it creates its own portal through which it exits the tissues and erupts into the mouth. As such, it very closely simulates normal eruption and the clinical outcome will usually be difficult to distinguish from any normally and spontaneously erupting tooth, in terms of its clinical appearance and objective periodontal parameters. A modification of the closed eruption technique has been described by Crescini et al. specifically in respect of maxillary permanent canines [23]. In this procedure, a full

Surgical Exposure of Impacted Teeth  35 

(a)

(b)

(c) Fig. 3.5  Crescini’s tunnel variation of the closed eruption technique. (Courtesy of Dr E Ketzhandler.) (a) A very high labial canine has been exposed with a full flap exposure, which included the gingival margin of the extracted deciduous canine. The bridge of buccal bone is left intact. (b) An attachment is bonded to the palatal aspect of the permanent canine and its pigtail ligature is directed through the socket vacated by the extracted deciduous tooth. (c) The flap is sutured to its former place and vertical traction will draw the tooth down, maintaining alveolar bone on its labial side.

buccal flap is raised from the attached gingival at the neck of the deciduous canine and adjacent teeth, to expose the surface of alveolar bone up to and including that covering the labially impacted buccal canine. The buccal crown surface of the canine is exposed and the deciduous canine extracted. The twisted steel ligature or gold chain linked to the eyelet, which is now bonded to the tooth, is threaded into the apical area of the recently vacated socket of the deciduous canine and drawn downwards to exit through its coronal end. No buccal bone is removed beyond that immediately overlying the crown of the exposed canine.

The flap is now sutured back to its former position, leaving only the end of the ligature/gold chain visible through the socket of the deciduous canine. The aim of this aptly named ‘tunnel’ technique is to mimic even further the natural eruption process by applying extrusive force to move the impacted canine directly through the socket of the recently extracted deciduous canine (Figure 3.5). Further­ more, by retaining the buccal bridge of bone during surgery, the final outcome will show the aligned tooth to have an excellent bony support, in terms of both its width and level.

36  Orthodontic Treatment of Impacted Teeth Each method has its advantages and its drawbacks from the points of view of efficacy of treatment, postsurgical recover and the overall treatment outcome in relation to aesthetics, periodontal prognosis and stability of the final result. Efficacy of treatment Should the orthodontist be present at the time of surgery?

The greatest inconvenience of the closed eruption technique is that it is preferable that the orthodontist be present in the operating room for bonding of the attachment before the flap is sutured back to its former place. It is true that many oral surgeons bond the attachments themselves. However, since the surgeon bonds orthodontic attachments far less frequently than does the orthodontist, the chances of bond failure are relatively increased – the more so since the surgeon, when working with only chair-side nursing assistance, will need to undertake both the task of maintaining a dry and uncontaminated tooth surface in a very haemorrhagic field and, at the same time, that of performing the bonding procedure. It should be emphasized that in the case of the closed eruption technique, bond failure will dictate the need for a second surgical intervention. If the attachment is to be bonded at a later visit, the orthodontist does not need to be present at the surgeon’s side for an open exposure case. However, this means that the surgeon must expose the tooth much more widely, place surgical packs and aim for healing by ‘secondary intention’ only, with attendant negative periodontal implications. Of far greater importance and directly related to ensuring successful resolution of the impaction, the orthodontist is able to see the exact position of the crown, the direction of the long axis and the deduced location of the root apex, by being present. The height of the tooth and its relation to adjacent roots may all be noted, and the orthodontist may confirm or change the original plan for the strategy of its resolution, by direct vision, in the light of what he/she now sees ‘in the flesh’. The orthodontist will be in a position to decide exactly where the attachment should be placed from a mechano-therapeutic point of view and will bond it there. The orthodontist is also the best person to fabricate and place a suitable and efficient auxiliary to apply a directional force of optimal magnitude and a wide range of movement, and to do so at the time of or, preferably, immediately prior to surgery. It is not fair to expect the oral surgeon to be aware of how different attachment positions may affect the orthodontic or periodontic prognosis; nor should it be expected that he/she will be sufficiently experienced with the bonding technique to do this. Indeed, without the presence of the orthodontist, the surgeon may carry out the exposure of the tooth and place a bracket in the most convenient location that may seem to him/her to be entirely appropriate. At a subsequent visit, the application of traction by the orthodontist may need to be made in a par­

ticular direction which, because of an incorrectly placed attachment, is impossible to attain, and the tooth may cause damage to adjacent structures by being drawn in an unfavourable direction. It becomes evident that the inconvenience caused to the orthodontist by his/her being present at the exposure is handsomely rewarded in the long run by far greater control of the destiny of the impacted tooth, including efficacy and predictability of treatment and the quality of outcome. The reliability of bonding

For the patient who has had an open exposure procedure, the reliability of bonding at a subsequent visit is, paradoxically, much poorer than when the attachment bonding is performed at the time of surgery [24] for the following reasons. During a closed surgery procedure, a wide tissue flap is usually raised, which provides good visibility and access, especially to a deeply buried tooth (Figure 3.6). The margins of the wide flap are distant from the tooth, enabling better control of moisture and bleeding in the immediate area. The orthodontist can bond the attachment efficiently, while the surgeon and the nurse maintain haemostasis and the necessary dry field. In contrast, an open exposure involves raising a small flap in the area immediately surrounding the tooth and maintaining the patency of the opening (usually with the help of a periodontal pack) until an attachment is bonded at a later date. At that visit, secondary healing will have occurred, and the newly epithelialized cut surface will be very sensitive to any form of manipulation. Accordingly, the patient will have avoided brushing the area and a degree of inflammation will be present, due to the accumulation of plaque and the freshness of the healing wound. Prophying the tooth under these conditions of restricted access and fragile haemorrhagic tissue is not conducive to successful bonding. In addition, the presence of eugenol from the periodontal pack may inhibit composite polymerization and thereby weaken the bond strength. When orthodontic brackets are bonded in day-to-day practice, the teeth are first cleaned, using a rubber cup and pumice. The aim of this procedure is to remove extraneous materials, which include soft plaque, dried saliva, organic and chemical staining, and deposits which adhere or adsorb to the enamel prisms and which may prevent penetration of the etchant. Once these are removed, the enamel surface becomes vulnerable to the orthophosphoric acid liquid or gel, which is the key to a successful adhesion of the attachment. In contrast, newly exposed impacted teeth are completely free of these extraneous materials. Their only covering is Nasmyth’s membrane, which is made up of the enamel cuticle and the reduced enamel epithelium and is about 1 micron thick. This appears to present no barrier whatsoever to the etching effect that is achieved by the application of orthophosphoric acid [24]. Accordingly, there is no advantage to be gained by pumicing these teeth

Surgical Exposure of Impacted Teeth  37 

(a)

(b)

(c)

(d)

Fig. 3.6  (a) The crown of an impacted canine is exposed using a wide flap, but with removal of minimal bone. The unexposed crown lies between the roots of the central incisors, having traversed the midline suture. (b) An attachment is bonded, while haemostasis is maintained by the surgeon. (c) The flap has been divided to accommodate the ligature pigtail in its desired position, before being fully replaced and sutured. (d) The labial spring auxiliary loop, seen in its passive position in (c), has been turned inwards towards the palate and secured to the stainless steel ligature pigtail.

as part of the bonding procedure. Rather, the reverse is the case. To permit the introduction of a hand piece and rubber cup or a small electric toothbrush or hand brush, exposure has to be considerably broader for prophylaxis to be effective. It is difficult to control these implements during the brushing exercise and, as a direct consequence, the brush or cup traumatizes the exposed bone and soft tissues. This generates renewed bleeding, while giving rise to a dispersal of the pumice over the immediate surgical field. Prophylaxis is therefore completely superfluous. A significant problem with the closed eruption technique is sometimes caused by a poor choice of orthodontic attachment. Since the mid-buccal position of this tooth is easy to expose and to bond to, the orthodontist may be tempted to use a conventional orthodontic bracket in this instance [25] and there is no contradiction in doing this with an open eruption technique. However, due to the buccal prominence of the tooth, the lack of buccal bone, and the relative tightness of the replaced flap, damage may be caused to this muco-gingival tissue by

the bulk of wide and high profile conventional brackets (see Figure 4.3), with the closed eruption technique. This may lead to a breakdown of the overlying tissue, to cause a dehiscence or even ‘buttonholing’ (Figure 3.7) of the mucosa. In such circumstances, any attachment placed on the tooth should be as small as is practical and with a minimum height profile, in order that it will cause as little adverse effect on the gingival tissues as possible, on its way through. This will be dealt with more fully in the next chapter. Duration of the surgical procedure When the surgical field is opened, there is considerable bleeding at the cut edges of the surgical flap and of the whole area that has been exposed by its reflection. The exposed area needs to be wide enough to afford the surgeon good visibility to perform the needed episode accurately and efficiently and, in order to fulfil any task, whether this be to remove a supernumerary tooth, dissect away bone, free an impacted tooth from its surrounding tissues or

38  Orthodontic Treatment of Impacted Teeth

Fig. 3.7  Buttonholing.

bond an attachment, good haemostasis must be achieved. This is usually done using high-power suction, packs of various sorts and the application of pressure. If the duration of the surgically inflicted wound is excessive, the surface of exposed bone will become desiccated, leading to cell death and it may take several weeks or months of healing before the necrotic section of bone is resorbed and replaced with healthy new bone. More importantly, desiccation of exposed roots of teeth, periodontal ligament and cementum may occur, which will damage these tissues – a factor that may sometimes be compounded by the overgenerous use of acid etchant. Adverse changes may then occur in these tissues which could result in impairment of the eruption mechanism of the tooth. This may be irreversible and result in failure to elicit eruption of the impacted tooth, even when traction is applied. The reader is referred to the sections on ankylosis and invasive cervical root resorption in Chapter 7 for a description of these phenomena. It is therefore important to select a surgical procedure or technique that may be completed in as short a time as possible. On the face of it, it would seem that an open exposure should take less time than a closed procedure. However, the results of a study performed by our group have indicated quite the opposite [26, 27]. It seems that the wide tissue flap raised in the closed procedure improves visibility, permitting easier and quicker exposure of the impacted tooth, thus shortening its overall duration. Suturing the full flap back to its former place is also considerably quicker and neater than suturing an apically repositioned flap into its new position with accompanying pack placement. Initiation of traction During a closed surgical technique procedure, the orthodontist may or may not be present but it is imperative that an attachment be bonded at the time. Absence places the onus on the surgeon to do this. It is obviously propitious to apply the eruptive force to the impacted tooth immediately, taking full advantage of the prevailing anaesthesia.

In contrast, when open surgery is performed, the presence of the orthodontist is unnecessary, the intention being to prepare the stage for the placement of an attachment at a future date by the orthodontist in his/her office. This means that the surgeon must complete the exposure in such a manner as to be sure that the tissues will not heal over and make the tooth inaccessible in the few post-surgical weeks until an attachment is bonded in the orthodontist’s office and traction may begin. Since orthodontic procedures in general do not require local anaesthesia, the orthodontist is unlikely to offer this to the patient at this orthodontic appointment, and additional delay in the application of force is inevitable due to the general sensitivity of the area to even gentle manipulation. It is therefore beneficial that an attachment be placed at surgery to maintain the treatment momentum. Speed of eruption When traction is applied to a palatally impacted canine in the closed eruption technique, the tooth may move rapidly and create a very palpable bulge beneath the thick mucosa of the palate, but will often experience difficulty in erupting through it. In these circumstances, it is recommended that a small circular incision be made around the crown tip of the impacted tooth and the tissue removed, to re-expose the tooth to a level not exceeding the greatest circumference of its crown. Further traction will then erupt the tooth very rapidly. Delay in performing this simple procedure will simply cause the anchor teeth to intrude and the overall arch form to become disrupted. The final treatment outcome Over the years, several groups of researchers in a number of countries have studied the post-treatment pulpal and periodontal status following the orthodontic resolution of impacted teeth, particularly in relation to maxillary canines and the open exposure technique. A Norwegian group [28] found an increased depth of periodontal pockets on the distal of the impacted teeth and bone loss on the mesial. In a group of patients with impacted canines, treated by undefined ‘conservative’ surgical procedures, a Seattle group [29] found attachment loss, reduced alveolar bone height and frequent instances of pulp obliteration, discoloration and misalignment, with the previously impacted canine being identifiable in 75% of the treated cases, presumably because of marred appearance. In relation to the outcome of the treatment of palatal canines with the closed eruption technique, a Jerusalem group of researchers found an excellent appearance, with slightly deeper pockets and a 4% loss of alveolar bone support [1]. In relation to buccally ectopic maxillary canines. They also found a minor reduction in the width of the attached gingiva, but otherwise a good periodontal outcome [3]. Further corroboration of the good clinical periodontal results to be seen when the closed eruption technique is used, in both buccal and

Surgical Exposure of Impacted Teeth  39 

(a)

(b)

Fig. 3.8  Treatment for the right buccally impacted maxillary canine was performed using an open exposure technique and an apically repositioned flap. (a) The post-treatment outcome shows a thick band of attached gingiva, but a long clinical crown with an unaesthetic lumpy appearance of the gingival margin. (b) The normally erupted canine of the left side is shown for comparison.

palatal canine cases, comes from a study carried out in the UK [21]. Comparison of open (specifically the apically repositioned flap exposure) and closed procedures was undertaken by the Seattle group, who used a mixed sample of incisors and canines in their study [30]. With regard to those treated with the open surgical approach, they found poorer results in both periodontic measurement and aesthetic assessment. For buccal canines, clinical crown length was increased and the gingival margins were often uneven and of poor appearance (Figure 3.8). Loss of attachment and alveolar bone were noted, together with frequent vertical relapse of the erupted tooth, after the completion of treatment. They reasoned that during the tissue healing that occurs after the surgical repositioning, horizontal mucosal lines are formed which undergo stretching and distortion during the incisal movement of the tooth. Once orthodontic control is released, vertical relapse occurs due to a contraction of these extended mucosal lines. By contrast, they found that clinical crown length and gingival appearance in the closed eruption group were similar to those of the control side in the closed eruption cases, with a completely normal periodontal attachment. No post-treatment relapse in incisor position was seen. Impacted incisors are seen far less frequently in the orthodontic office than are canines, accounting for a relative absence of reports regarding their treatment outcomes. However, given differences in their varied aetiologies, there was reason to believe that there could be differences in the end result of their treatment. The first clear-cut, ‘maxillary incisors only’ investigations were conducted by the Jerusalem group [26, 27], who found poor periodontal and aesthetic results in the open eruption group, with increased pocket depth and a 10% loss of alveolar bone height. The clinical crowns were elongated and the band of attached

gingiva reduced. Those treated by the closed surgical procedure showed only minimal changes, with greater bone support, a lesser increase in clinical crown length and better appearance than in the open surgery group. Crown length and attached gingiva were closely similar to those of the unaffected side, while the bone support level was reduced by between 5% and 6%. In a subsequent open vs. closed exposure study, using similar impacted incisor cases matched for age, aetiology and location of tooth, the results strongly favoured the closed surgical exposure method, with the open exposure cases showing statistically poorer outcomes, characterized by increased crown length and more significant loss of bone support [30]. The evidence presented here indicates that a closed surgical exposure approach produces good, predictable, longterm periodontal and aesthetic results, and has advantages over the apically repositioned flap method [2, 32]. These have been attributed to the close similarity of the conditions brought about by full flap closure to those associated with normal tooth eruption [10, 23]. The Cochrane Data Base Collaboration offers systematic reviews of primary research in human health care and health policy and the clinical researchers investigate the effects of interventions for prevention, treatment and rehabilitation in various fields. All the existing primary research that meets certain criteria on a topic is searched for and collated, and then assessed using stringent guidelines, to establish whether or not there is conclusive evidence about a specific treatment. The reviews are updated regularly, ensuring that treatment decisions can be based on the most current and reliable evidence. This is obviously the ideal framework through which to objectively adjudicate the rival claims of the open exposure advocates and those favouring closed exposure, which may be tainted with

40  Orthodontic Treatment of Impacted Teeth personal subjective preference or bias. A Cochrane Coll­ aboration Systematic Review was recently undertaken in the UK [33] in which only those factors directly related to the surgical aspect were examined and no regard was paid to the age of the patient, the presenting malocclusion or the type of active orthodontic treatment undertaken. It is clear from what has been described above and what will be discussed in later chapters that the quality of the outcome is only partly due to the surgical procedure and that these other factors are intimately involved in the outcome. Indeed, some may be just as potent in dictating the result. Without doubt, a number of these factors may be neutralized in a very large sample because randomization may have distributed them equally between the two groups. Nevertheless, there are several which cannot be discounted [1–3]. Among these one must look at three distinct sources, namely factors related to the patient, those related to the oral surgeon and those related to the orthodontist. Patients present with a wide variation in positional diagnosis of the tooth and its proximity to adjacent teeth, some of which are not amenable to open surgery procedures. There is great variation in the level of oral hygiene among our patients and poor oral hygiene has a direct and negative relationship on the quality of outcome, even in the best treatment plan. No two oral surgeons work in the same manner, and often exhibit differing preferences in relation to flap design, amount of bone and soft tissue removal, whether or not to remove the follicle in its entirety, pack size and the amount of pressure applied by the pack. Some surgeons are known to ‘assist’ in the eruption by radical exposure and by pushing an elevator down the PDL of the tooth, to be sure that it is mobilized, particularly when the orthodontist is not watching! When the surgeon is called on to place the attachment, his/her bonding skill and knowledge of the most advantageous bonding location cannot match those of the orthodontist, raising the spectre of detachment, repeat surgery and inappropriate traction direction. Any one of these factors may alter periodontal health and gingival architecture. Orthodontists also work in different ways, with widely differing appliance methods and customized traction device designs. There will be a periodontal price to pay for inappropriate directional traction, excessive traction forces and treatment inefficiency, not to mention varying quality standards of case completion. In short, the number of factors involved is so great and so diverse that it is not possible to arrive at a ‘squeaky clean’ sample that will permit the comparisons necessary to achieve a neat and authoritative answer to the question of surgical exposure preference – Cochrane Collaboration notwithstanding. This leaves the reader to rely on what is available, which is a large body of published studies based on retrospective samples, from which to draw some appropriate, if empirical, conclusions.

Partial and full flap closure on the palatal side Often, impacted teeth that are located on the palatal side are palpable immediately beneath the palatal mucosa, which is firmly bound down to the underlying bone. The surgical removal of a circular section of the overlying mucosa (see Figure 6.29) and the thin bony covering, and leaving the tooth exposed, is tempting and has obvious advantages. In particular, the newly exposed tooth will be favourably invested with attached gingiva when it finally erupts. However, the palatal mucosal covering is very thick and will leave a broad cut surface, which will tend to close over unless its edges are substantially trimmed back and the dental follicle removed. Thus, for a deeply placed tooth, the exposure will additionally need to be maintained using a surgical pack. This type of surgical approach will, therefore, leave the palatal side of the tooth with a soft tissue deficiency and a long clinical crown, at the completion of the orthodontic alignment and in the long term, even though the character of its surrounding tissue will be desirable attached gingiva (Figure 3.9). This method has been favoured and promoted in relation to palatally impacted canines, since it has been suggested that the canines will improve their position in many instances and erupt autonomously in the palate in time [34]. This study retrospectively investigated the post-treatment periodontal status of a group of patients who had been successfully treated by this method. However, there is no published controlled study that looks into the reliability and predictability of this treatment option protocol. As we have described for the buccal side, full flap closure on the palatal side allows the tooth to be exposed with the minimum of tissue removal and consequent surgical trauma and it also requires the bonding of an attachment on the exposed tooth prior to suturing. When this is done and given appropriate orthodontic mechanics, the final result will show that the bone support for the tooth, as well as the health and appearance of the muco-gingival tissues, is at its best, as will be demonstrated in the following chapters. The accumulated evidence that has been presented in the various clinical comparisons of surgical methods of exposure [1, 2, 4–6, 23, 26–28, 30, 31, 35] provides the evidence base to recommend the full flap closure approach over any other, in most situations, in relation to a palatally impacted tooth. This refers to both qualitative clinical appearance assessment of the crown length and gingival architecture and quantitatively to objective parameters evaluated in a periodontal examination.

Buccally accessible impacted teeth Indications for apically repositioned flap exposure On the basis of their results for exposure on the buccal side of the ridge, the Seattle group questioned the justification

Surgical Exposure of Impacted Teeth  41 

(a) (a)

(b) Fig. 3.10  A case treated by the author in the mid-1970s, before the era of the acid-etch technique. (a) A left impacted maxillary central incisor has been exposed and the entire follicular sac removed, prior to cementing a band. (b) At two years post-treatment, the gingival contour is poor, the clinical crown is long and there has been positional deterioration of the previously aligned tooth.

(b) Fig. 3.9  Treatment for the right palatally impacted canine was performed with an open-exposure technique. (a) The post-treatment result shows attached gingiva of the palatal tissues covering most of the root, although the clinical crown length extends well down on the palatal side of the tooth, leaving several millimetres of root exposed on that side. The bone level is expected to be 8–10% defective compared to the untreated side. (b) The normally erupted left canine is shown for comparison.

for the continued use of the apically repositioned flap method [30]. From the above discussion, it is clear that there are grounds for their scepticism in relation to teeth that are more severely displaced. Nevertheless, it should be realized that for the more trivial cases, where the tooth is mesio-distally fairly close to its final position and bulging the oral mucosa at its junction with the attached gingiva, the application of the apically repositioned flap method may eliminate the need for subsequent orthodontic treatment, as we have noted earlier in this chapter and in Figure 3.1, while producing a good periodontal result. Experience

shows that many of these teeth never come down fully to the occlusal level, and those that do erupt well may take many months, sometimes stretching to a year or more, to do so. This appears to be due to the relapse tendency engendered by the distorted mucosal lines in the muco-gingival area produced as a result of the surgery [10]. In the final outcome of this form of surgical exposure, an unaesthetic gingival contour may sometimes result (Figure 3.10). Grafting may be needed to improve this [15–16, 36–38]. When left untreated, buccally palpable unerupted teeth may take many months to break through the mucosa and reach their final positions. After an apically repositioned flap is performed, eruption is speeded up. Additionally, with the sutured soft tissue applying some pressure on the buccal side of the tooth, and assuming there to be space in the immediate vicinity, buccal displacement may be spontaneously reduced. If the unerupted tooth is very high, the surgical flap, which must include attached gingiva on the crest of the ridge or at the free gingiva of the deciduous tooth up to the

42  Orthodontic Treatment of Impacted Teeth depth of the sulcus, will be excessively large. Under these circumstances, the procedure is not recommended, since the apically repositioned flap would leave a wide area of periosteum of the labial bony plate unnecessarily exposed to the oral environment. In order to cover this area, grafts would need to be taken from elsewhere in the oral cavity. A useful alternative for these very high teeth is to use a combination of two distinct techniques [39], particularly for conditions like the labial dilacerate central incisor. Initially, a closed eruption procedure would be used and the tooth brought down until it bulges the labial mucosa, well above the attached gingiva and is in danger of erupting through this loose and thin oral epithelium. At this point, a second procedure is undertaken in which an apically repositioned flap, taken from the crest of the ridge and incorporating attached gingiva, is raised and re-exposes the impacted tooth from below. The flap is then taken over the incisal edge/occlusal tip of the tooth and sutured on the labial side. The tooth may now continue to be drawn occlusally, completely encompassed by firm gingival tissue. At the same time, it should be recognized that the well-sutured flap will additionally apply pressure on the labial side of the buccally/labially displaced tooth that it is partially covering and will be a positive influence in moving it lingually towards the general line of the dental arch (see Chapter 15). While the closed eruption exposure method is to be preferred in most situations, an important advantage of the apically repositioned flap method is that the buccally impacted canine is exposed to the oral environment and remains accessible for attachment bonding. In some cases, where orthodontic treatment is not needed for other problems, the progress of the tooth may be followed for many months, until full eruption has occurred without the use of appliances (Figure 3.1). In others, an attachment may be bonded by the orthodontist at any appropriate later date and active extrusion subsequently undertaken. Indications for circular incision (window) exposure Perhaps the only situation in which the circular incision is appropriate for a buccally sited tooth is when the tooth is correctly mesio-distally located, the band of attached gingiva is very broad and the tooth can be palpated occlusal to the muco-gingival junction. In this case, and provided that at least 2 mm of attached gingiva remain intact apical to the crown after removal of the cut tissue over the tooth, this procedure provides the simplest appropriate approach [10]. The relief of crowding to reduce canine displacement If the displacement of the canine has been due to crowd­ ing, then it follows that spontaneous improvement of the position of the canine may well occur if the crowding is eliminated.

Time may not be on the side of the clinician opting for this approach, since the tooth may erupt through the oral mucosa if delay is incurred. Nevertheless, for the case in which this approach is to be used, a full case analysis is required, leading to a diagnosis and treatment plan for the overall malocclusion. If the crowding is to be dispersed by distal movement of the molars, it will take longer before space is available in the canine region. Considerable delay must be expected while the treatment is proceeding before spontaneous improvement of the canine position may be seen. On the other hand, a premolar extraction will provide immediate relief of the crowding and an excellent opportunity for a self-correction of the buccal displacement and, with it, the disappearance of the potential periodontal hazard. A buccal approach may sometimes be preferred in the treatment of a palatally impacted maxillary canine, provided that its palatal displacement from the line of the arch is fairly minimal. By using the buccal approach with an impacted tooth that is vertically fairly close to the CEJs of the adjacent teeth, there is a danger that interproximal bone will be destroyed in the process. The greater the palatal displacement of the tooth, the greater will be the bony defect. Nevertheless, the approach may be advised for those teeth that are marginally palatally displaced and situated higher in the maxilla, since it offers the prospect of a more direct route for traction of the tooth to the labial archwire. Impaction of the maxillary canine which is close to the line of the dental arch may occur when the canine has a mesial tip and when its mesial crown incline comes into direct contact with the distal side of the root of the lateral incisor. This is a fairly easy impaction to treat, and may be self-correcting, when the crown of the lateral incisor is tipped mesially to close anterior spacing and to provide room for the canine in the arch. By doing this, the root apex of the incisor moves distally and favourably alters the orientation of its long axis with that of the canine. If the tooth still shows no sign of erupting, a labial surgical approach to the very mildly palatally displaced canine will often be the most suitable and, in terms of the traction, the most direct.

A conservative attitude to the dental follicle The dental sac or follicle develops from a mesodermal condensation of cells on the outer surface of the external enamel epithelium of the enamel organ of a forming tooth, into a fibrovascular capsule. The follicle has an inner vascular plexus through which the enamel organ is supplied with nutrients during growth, and an outer vascular plexus which is concerned with enlarging the bony crypt in which the tooth germ lies. It achieves this by its inherent capability to resorb the alveolar bone. The follicle encompasses the entire tooth germ and, as Hertwig’s root sheath proliferates as an apically directed extension of the follicle, the root

Surgical Exposure of Impacted Teeth  43  portion of the tooth is formed. Later, the outer surface of this sheath eventually becomes the periodontal membrane, connecting the cementum covering of the developing root to the developing alveolar bone. The enamel cuticle covering the crown is made up of a keratinous deposit from the ameloblasts and the reduced enamel epithelium, and is continuous with Hertwig’s epithelial root sheath. This separates the crown of the tooth from the follicle, from which the root develops and cementum forms. It is because there is this separation between follicle and enamel that cementum is not formed on the crown of the tooth. Eruptive movements that accompany the resorption of the bony crypt bring the tooth follicle into close proximity to the oral mucosa. Their epithelia fuse and the tooth thus breaks through an epithelium-lined opening. As eruption proceeds, the remainder of the follicle everts and comes to be turned ‘inside out’, with the reduced enamel epithelium becoming the gingival cuff and most superficial point of attachment. When the tooth erupts in this normal manner, it is accompanied by a relatively generous band of gingival tissue, which is rounded and appears a little swollen initially. The most coronal portion of this gingival tissue is the free gingiva, and, at its base, the attachment is direct to the cervical area of the enamel of the crown of the tooth, several millimetres coronal to the CEJ. This represents a very special type of attachment, in that the gingival band immediately adjacent to the crown adheres directly to the enamel through the agency of hemidesmosomes (cells that originate in the reduced enamel epithelium). Over the subsequent period of 3–4 years, this transforms into the junctional epithelium which constitutes the initial form of attachment of the gingiva to the tooth, on the cervical enamel area [40]. It is in the patient’s interest for us, when treating an impacted tooth, to try to create conditions that will replicate this natural eruption process as closely as possible, and this obliges us to treat the follicle conservatively. If the follicular tissue is totally removed down to the CEJ, then we can no longer expect there to be a gingival attachment direct to the enamel of the crown of the tooth. The attachment that will result will be on cementum, at or somewhere down the root surface, beyond the CEJ. This will result in an elongated clinical crown and a compromised periodontal result (Figure 3.10). Point to remember When an impacted wisdom tooth is removed surgically, the dental follicle is always carefully dissected out to prevent the possible later occurrence of cysts that may arise from residual follicle epithelium. Without the tooth, therefore, the residual follicle has no function, merely a potential nuisance value. However, when a tooth is exposed only, its surrounding follicle has an important function to fulfil – a function which is identical with that of a tooth which

erupts normally and which is integral to the establishment of a normal biological support system. This difference in attitude to the follicle of a tooth committed for extraction compared with that of a tooth that is to be exposed and subsequently to be erupted into the mouth is basic and important to understand. From studies of the causation of external crown resorption of long-standing buried teeth, it has been found that pathological changes occur in the follicle surrounding its crown (see Figure 6.12) over a period of many years, changes which have brought the enamel surface into direct contact with the surrounding tissues [41]. It is easy to draw a parallel between this condition and the artificially produced environment of an impacted tooth that has been surgically exposed and, without extrusive force being applied, has subsequently become reburied in the tissues. If, for whatever reason, the tooth does not erupt spontaneously, there will be long-term direct contact between the tissues and the enamel of the tooth. In clearing the tissues surrounding an impacted tooth for the purpose of creating an opening adequate in size which will not eventually close over, the surgeon will, generally, deliberately and completely remove the follicle surrounding the tooth (Figure 3.10). The oral epithelium grows down the sides of the opening, into the area that has been surgically cleared of follicular tissue. It will grow down as far as the deepest point where instrumentation has occurred which, in this case, will be at least to the CEJ or possibly a little way down the root surface, depending on how carefully the surgery was performed. This is considerably further apically than one would expect to find in a tooth whose recent eruption has occurred spontaneously, and a compromised gingival attachment will result. The subsequently erupted tooth will have a longer clinical crown and reduced alveolar crest height, in sharp contrast to a tooth that has erupted recently and autonomously. The application of orthodontic traction only requires an opening in the follicle which is large enough for the attachment to be placed, while the rest of the follicle may be left intact. The surgical flap may then be fully sutured back and the wound completely closed. Orthodontic traction brings the tooth towards the oral cavity and the intact remains of the follicle fuse with the oral mucosa, to mimic normal eruption. This leads to the establishment of a normal gingival attachment [23]. It is clear, then, that a new look must be taken at the surgical plan for the exposure of unerupted teeth. If bonding will not take place at surgery, then a wider exposure must be performed and a surgical pack may need to be placed. The principal reason for this is to prevent the reclosing of the wound. Thus, even though one must stress the importance of avoiding overzealous surgical removal of the follicle and of damaging the CEJ area, by the forceful placement of the pack, a poorer periodontal result should be expected. Attachment bonding must subsequently be performed at a

44  Orthodontic Treatment of Impacted Teeth convenient time after pack removal. However, at this time, the healing and swollen gingival tissue surrounding the exposed tooth will be tender, will be covered with plaque and will bleed with minimum provocation, since effective toothbrushing in this delicate and sensitive area is unlikely to have been possible. These are not conditions that are conducive to reliable attachment bonding, despite the ease of access. A wide flap design has the advantage of displaying the form of the area of bone covering the tooth, which is helpful in identification of the exact site of the tooth. A canine tooth buried in a bony crypt in the palate will alter the shape of the palate inferiorly by creating a distinct bulge of thinned bone, and this will be all the more obvious if much of the surrounding bone is also visible. This is just as true in the labial plate of the maxilla and in the buccal or lingual plate of the mandible, where the tooth in question may be a maxillary central incisor, a second premolar or any other tooth. The distancing of the edges and underside of the flap from the field of operation is important, if contamination with blood is to be avoided during bonding. This is most easily performed when the flap design is generous. Once the bony surface has been exposed and the location of the buried tooth identified, the thin overlying bone may be lifted off very easily. The surgeon will generally use a sharp chisel with light hand pressure to cut open the bony crypt and remove the superficial part of its wall. The bone is often paper-thin and can be cut with a sharp scalpel. Immediately beneath the bone, the dental follicle will be seen to glisten in the beam of the operating lamp. A window should be cut in the follicle to fully match the extent of the very minimal bony opening that has already been achieved, in order to see the orientation of the tooth, as it lies in its crypt. As we shall describe in later chapters, it is important to place the orthodontic attachment as close as possible to the mid-buccal position of the crown of the tooth, so that traction will tend to reduce any existing rotation, thereby reducing the amount of mechano-therapy to which the tooth will need to be subjected. For this reason, where a rotated tooth is exposed, the bony opening should be extended around the crown of the tooth, towards the midbuccal area of the crown, provided that this can be done with ease and with the infliction of little or no further surgical damage. In this instance, flap replacement may be completed and the pigtail ligature, tied into the newly placed attachment, drawn in the direction of the proposed target site in the dental arch. During exposure of the crown of a tooth, instrumentation of the enamel surface is not detrimental to the eruption process or to the quality of the treated result. However, exposure and instrumentation of the root surface is potentially damaging. Exposing root surface presupposes that the natural attachment of the tooth at the CEJ will have been ruptured, and renewed attachment will probably only be

established more apically. Additionally, periodontal fibres are severed and cementum exposed, subjected to drying (suction and air syringe) and contact with foreign substances (etchant, bonding materials). This can lead to the later initiation of a resorption process on the root surface, to ankylosis and to failure of eruption in extreme instances. More common sequelae include seriously reduced bone support, long clinical crowns and poor gingival attachment and quality. The raison d’être of the closed eruption technique has been called into question by Kokich, who prefers an open surgical approach for the exposure of canines that are deeply impacted in the palate. The method he describes demands the excision of enough bone until the cavity created is larger than the crown of the tooth, at its greatest mesio-distal diameter, and extending from crown tip to CEJ and, at the same time, the follicle is removed in its entirety. The rationale for this procedure is that while contact of the follicle of an advancing unerupted tooth with alveolar bone causes resorption of the bone, as seen in the normal, unaided eruption of teeth, the proximity of bare enamel to alveolar bone does not physiologically initiate resorption ‘since there are no cells in the enamel to resorb the bone’. The contention is that ‘resorption will eventually occur through pressure necrosis, but it will occur slowly’. Hence, when an impacted tooth is located in mid-palate, the advice has been to perform an open exposure and maintain its patency pending natural, spontaneous eruption, which may or may not occur. The confident claim is that ‘these palatally displaced canines will erupt on their own . . . in about 6 to 8 months’ [10]. This hypothesis has not been tested on a random sample of impacted canine cases and, more importantly, neither has the periodontal outcome of the orthodontically successful outcome of such a sample been evaluated. Reparatory bone deposition begins in the organizing blood clot within a few weeks following surgery. This being so, it follows that, unless the widest part of the crown of the impacted tooth has been drawn fully outside the bony plate in this very short time period, bone must be expected to re-form over parts of the crown of the tooth and that, according to the hypothesis, this will cause the tooth to stop moving. This would obviously not augur well for patients with teeth which are deeply impacted in bone, or others for whom several weeks or months may have elapsed after the surgical exposure and before orthodontic traction is applied. Chapter 12 describes many of the more common reasons why failure to resolve the impactions may occur and how these may be avoided. Cases illustrated there show resolution of the impaction being successful as much as a year or more after the surgical exposure had been performed and, sometimes, after an initially failed treatment by another practitioner. Before treatment was started in these failed transfer cases, much mature bone would have been laid down as a potential stumbling block in the path

Surgical Exposure of Impacted Teeth  45  of the impacted tooth, yet the second attempt at treatment was successful, rapid and did not need re-exposure of the tooth. Three decades ago, it was shown that the presence of an intact follicle is a prerequisite for the process of normal and spontaneous eruption [42]. Nevertheless, experience has taught us that light orthodontic traction is capable of encouraging the resorption of bone needed for the eruption of an exposed tooth, even in the absence of a follicle. Anecdotal clinical evidence contradicting Kokich’s view is provided in the section dealing with impacted maxillary canines that are associated with root resorption of their immediate neighbours (Chapter 7). In the more extreme examples of this anomaly, the canine crown and the resorbed incisor root are intimately related and situated in the middle of the ridge, surrounded by bone on all sides [39]. The exposure has to be carefully planned to avoid surgical trauma to the incisor root area. Wide clearance of bone and dental follicle to the full width and length of the crown of the canine, down to the CEJ, is obviously out of the question. Nevertheless, these teeth can be routinely drawn through the surrounding bone and the impaction resolved with light forces which are suitably directed, as with any other impacted tooth, and with considerable speed in most cases. Similarly, in Chapter 14, which describes the treatment of patients with cleidocranial dysplasia (CCD), surgical exposure has to be performed on multiple impacted teeth deeply displaced low down in the basal bone. For reasons outlined in that chapter, exposure of the canine and premolar teeth is typically aimed at the buccal aspect of the teeth, without the deliberate wide removal of bone surrounding the remainder of the crown of the tooth and without exposing the occlusal surface of the crown of the tooth superiorly. This seems to have no noticeable retarding effect on the eruptive response of the tooth to occlusally directed light forces, which is rapid and generates eruption within a short time. This is despite the fact that it may often have to resorb a thick layer of bone on its way, and despite the fact that alveolar bone in CCD patients is considered to be particularly dense and the largely acellular cementum on the roots of their teeth is associated with slower resorption [43]. Individual clinical case reports illustrating the eruption of teeth through bone grafts appear in the literature from time to time. In one of these, a palatally impacted maxillary canine was diagnosed in a unilateral cleft palate patient, located superiorly to the reparative autogenous alveolar bone graft that had been placed some years earlier. The patient underwent a closed eruption procedure and the tooth was erupted through the bone graft [44]. In another case report [45], an impacted canine was exposed and then successfully drawn through a synthetic bone substitute, which had earlier been grafted to fill an area where a significant volume of buccal cortical bone had been lost, due to the surgical removal of multiple odontomes.

In each of these difficult and extreme scenarios, a successful outcome of the treatment will almost always show good clinical and radiographic features, notwithstanding the need to erupt the teeth through surrounding alveolar bone. In terms of clinical appearance, the periodontal condition and an absence of any signs of pathology, it is also difficult to distinguish the treated teeth from other unaffected teeth in the mouth. The tunnel method [23] mentioned above deliberately aims to bring a large canine down through the much narrower socket recently vacated by the extraction of its deciduous predecessor. This cannot be done without the resorption of bone lining the socket. Furthermore, given the time involved in bringing a severely displaced canine into its place in the arch and however rapidly this may be achieved, the lower part of the socket will surely have undergone healing. Therefore, the eruptive progress of this tooth cannot go far along this vacated socket before healing of the extraction will have brought about the deposition of new bone directly in its path. In the closed eruption approach described in the present chapter, we have recommended reflecting a wide soft tissue flap, but only opening the dental follicle itself to a very minimal degree – enough only to permit the maintenance of haemostasis while the bonding of a small attachment is performed. The remainder of the follicle survives intact, which means that all other parts of the crown of the tooth are invested in follicular tissue, which will initiate bone resorption when traction is applied. The break in the integrity of the follicle exists solely at the site of the attachment, where only a minimum of bone has been removed. It is open to speculation whether repair of the follicular tissue may occur over a low-profile attachment and its integrity fully restored around the steel ligature to which traction is applied. This ideal scenario would appear to be most unlikely, although if it were indeed true, then the ideal eruption environment will have been re-established and light directional traction should bring about successful eruption of the tooth, with the reward of an excellent gingival appearance and periodontal health. Regardless of the reasons why a conservative attitude to the dental follicle works so well, the fact remains that post-orthodontic corrective periodontal flap and graft procedures are largely superfluous in these cases. For the most part, the previously impacted teeth are impossible to distinguish from their unaffected neighbours and antimeres, clinically, radiographically and aesthetically (Figures 3.11 and 3.12).

Quality-of-life issues following surgical exposure When a patient undergoes traditional surgery for an inguinal hernia, he must be informed that, following his stay in hospital, his previously active lifestyle will need to be curtailed. He will suffer pain and swelling at the

46  Orthodontic Treatment of Impacted Teeth

(b)

(a)

(c)

(f)

(d)

(e)

(g)

Fig. 3.11  A case of bilateral palatal impaction of maxillary canine treatment with the closed eruption surgical technique. (a) Panoramic view to show canines almost contacting in the midline. (b–d) Panoramic and periapical views of the post-treatment result. (e–g) Centre, right and left clinical views of the treated result, 14 years post-treatment, show the treated teeth to be indistinguishable from their neighbouring teeth in terms of their crown length, gingival contour and excellent appearance. (h–k) Clinical views of the buccal and palatal sides of the two canines, 14 years post-treatment, to show normal gingival contour, normal crown length and no recession. No reparative periodontal procedures were performed after the original closed surgical exposure.

(h)

(i)

(j)

(k)

Fig. 3.11  (Continued )

(a)

(b)

(c)

Fig. 3.12  (a) an impacted right maxillary canine treated with full flap closure on the buccal side, using the closed eruption technique. (b, c) The right and left sides are indistinguishable at the completion of treatment.

48  Orthodontic Treatment of Impacted Teeth operation site. He will be unable to undertake heavy work, his posture may be initially affected, driving a car will be difficult and he will have pain when passing urine in the early postoperative period. Under such circumstances, the character of his entire lifestyle will need to be much subdued and his quality of life will suffer. In the present context, the (usually young) patient who is about to undergo surgical exposure of an impacted tooth needs to be informed how the procedure will affect his daily life, in terms of pain, function, speech and the several other aspects that surround the oral cavity, including the risks and benefits of the intended treatment. The patient is often apprehensive at the thought of surgery, particularly if he is a young and healthy individual with little or no previous experience of surgical procedures. The incidence and magnitude of these possible sequelae are all part of the postsurgical follow-up, which the patient and his parent must be aware of, and constitute information that they must legally have in order for them to sign a statement of informed consent. While this is true of all types of orthodontic treatment, it is particularly so when surgery is involved. Oddly, while a number of articles have recently appeared in oral surgery journals regarding these parameters in relation to the extraction of third molars, there is a significant paucity of published work that relates to quality-of-life issues related to the surgical exposure of impacted teeth. The result has been that the information available to both clinicians and patients often comes from one-time anecdotal episodes and hearsay from individuals who have themselves experienced some form of oral surgery. These reports are notoriously unreliable and rarely offer appropriate comparisons with the surgical exposure at hand. It was for this reason that prospective clinical studies were undertaken in Israel to quantitatively assess the various aspects of quality of life following the performance of both open and closed surgery [46–48]. Two groups of patients were assembled for study. One group included young patients who were scheduled for open surgery and the second group for closed surgery of an impacted tooth. Each patient was presented with seven identical questionnaires on the day the exposure was performed and was instructed to complete one of the questionnaires on each post-treatment day, for seven days. From the answers, information was collected regarding pain, oral function, general disability, limitation in eating, absence from school and related parameters. The results for the group of patients who had had open exposure were then analysed and compared with those for the patients who had undergone a closed exposure technique. In general, it was found that recovery from an open eruption exposure required five days vs. three days for a closed procedure. The prolonged recovery was particularly observed in relation to a higher level of pain, difficulty in eating and swallowing, and to the use of analgesics. There

was much greater discomfort with the open exposure in association with a palatally impacted canine, especially if bone removal had been performed. However, it is noteworthy that exposure of impacted teeth with a buccal approach resulted in a high level of discomfort, regardless of the surgical method employed. It may be speculated that this is due to the fact that paranasal and oral musculature is severed during buccal procedures, and the healing surgical flap is sited in highly mobile oral mucosa. We may summarize the advantages and disadvantages of complete flap closure (healing by primary intention) compared with the alternative open exposure techniques, in which the opening in the tissue over the impacted tooth is maintained by reducing the size of the flap and packing the wound or by repositioning the flap more apically (healing by secondary intention), in the following manner. Primary full flap closure

Advantages healing • rapid less discomfort • good postoperative haemostasis • less impediment to function • conservative bone removal • immediate traction possible • high degree of reliability of bonding • possible in close proximity to resorbing root area • Disadvantages of orthodontist advised • presence bond failure dictates re-exposure • Open exposure

Advantages presence unnecessary • orthodontist’s bond failure – needs no surgery • Disadvantages risk of infection • greater greater discomfort • interference with function • wider bone exposure • bad taste and smell in mouth • possibility of reclosure of exposure • bonding reliability poorer • delayed initiation of traction • poorer periodontal condition • extra visits to change packs •

Cooperation between surgeon and orthodontist From the discussion in this chapter, it is hoped that the reader will have come to realize the narrow limitations of

Surgical Exposure of Impacted Teeth  49  the surgeon’s ability to materially assist these cases and to appreciate that the inclusion of orthodontic procedures offers most cases a better chance of success. Today, orthodontists have come to play a more important role in the initial stages of the treatment of impacted teeth, by providing the traction that is necessary to encourage this eruption and, in many cases, to do so successfully in teeth that were previously felt to have a poor prognosis for eruption. The status of an impacted tooth today is largely dependent on the ability and the ingenuity of the orthodontist to apply light traction in an appropriate direction and with efficient means, once the tooth has been made accessible by the oral surgeon. If orthodontic treatment is available to the patient, there is little merit in the surgeon offering any of the other procedures listed at the beginning of this chapter, since there is no evidence that suggests that these procedures may improve the opportunity for orthodontic resolution, without causing concurrent harm. We may therefore conclude that, with respect to the treatment of impacted teeth, the aims of the oral surgeon should be limited to: provision of access to the buried tooth; • the the of any obstruction in the tooth’s eruptive • path,clearing such as supernumerary teeth, odontomes or thickened overlying mucosa; taking an active part with the orthodontist in bonding an attachment to the exposed teeth at surgery by maintaining haemostasis, which is so critical in ensuring success.

•

The single most important aim of the surgical episode is to provide access to a tooth which is otherwise buried. This enables the orthodontist to provide the means by which force may be applied to the tooth in question, through several subsequent visits over a longish time span, and in as simple a manner as possible. For this to happen, an attachment has to be securely bonded and a firm ligature or other form of intermediary drawn to the exterior, to which steel wires, super-elastic nickel–titanium wires, elastic ligatures or an auxiliary spring may be tied. A sharing of the responsibility for the successful execution of this procedure should be undertaken by the oral surgeon and the orthodontist, with one specialist complementing the other in applying their very special skills to the resolution of the immediate task. Together, they possess all the tools that are needed to complete the job for which, separately, each is perhaps ill-equipped. Their combined efforts should be geared to achieving this. Bonding an attachment to the tooth a few weeks after the surgery has been performed has the advantage of not requiring the presence of the orthodontist at the surgeon’s side. By doing this, the surgeon must expose the tooth much more widely, place surgical packs and aim for healing ‘by secondary intention’, as has been pointed out above and as will be explained in greater detail in later chapters.

Additionally, the reliability of the bonding at this later date is much poorer than when performed at the time of surgery [24].

The team approach to attachment bonding This episode primarily represents an adjunctive surgical procedure, whose aim is to provide a site for the application of an orthodontic force-delivery system. As such, it should be carried out on the surgeon’s territory and not in the orthodontic clinic. The orthodontic treatment will have been initiated and orthodontic appliances will, most often, be in place before the surgical exposure is attempted. Orthodontic procedures that need to be carried out during the surgical episode are few and relatively simple and can all be performed in the oral surgeon’s operatory. However, the orthodontist should prepare a small tray of instruments and materials which are not normally available in the operating room, together with a customized auxiliary spring, which may have been fabricated at a previous visit for the purpose of applying a directional force to the impacted tooth, such as a ballista [49], a flexible palatal arch [50–51] or a labial auxiliary arch [52] (see Chapter 6). The instrument tray should contain the following items: Instruments wire bending plier (e.g. Begg plier) • aa fine fine wire-cutter • reverse-action tweezers which are closed • when not heldbracket-holding and release when the handles are lightly squeezed a ligature director a mosquito or Matthieu forceps a fine scaler

• • •

Materials gel • etching composite bonding material, preferably a light-curing • material, which is probably the most manageable type of bonding method that can be used in these special circumstances, although a no-mix paste and catalyst may serve very well applicators (wood sticks, fine brushes, etc.)

•

Attachments eyelets welded to thin band material, backed with stain• less steel mesh; these should be cut and trimmed into patches of various sizes, but not larger than the base of a small bracket cut lengths of dead soft stainless steel ligature wire of gauge 0.011 in or 0.012 in elastic thread and elastic chain

• •

It has been the author’s practice to tie the labial auxiliary arch into the orthodontic brackets immediately prior to the surgical exposure since, in its relaxed position, the active

50  Orthodontic Treatment of Impacted Teeth loop stands well away from the immediate surgical field and does not interfere with the work of the surgeon. Other customized auxiliaries may be similarly tied in or placed on the instrument tray, in readiness for placement at the end of the procedure. The surgeon reflects a muco-periosteal flap over the impacted tooth and removes the intervening bone, which is usually very thin and easy to peel with a scalpel blade. If a supernumerary tooth or odontome is present, this is removed first. The dental follicle is removed from the target area immediately overlying the crown and the resultant exposure is not widened more than is necessary to satisfy two basic requirements (Figure 3.6a). These are: (a) to provide enough enamel surface to accept a small attachment, and (b) to do so in an area wide enough for adequate haemostasis to allow the bonding procedure to take place without fear of contamination. The surgeon then moves to the other side of the operating couch in order to take over the entire responsibility for maintaining the enamel surface free of blood and saliva throughout the critical bonding phase – which is, after all, the point of the entire exercise! Under the conditions of exposed and oozing soft tissue and bone surfaces, the surgeon will generally need to use a regular suction tip and a second and very fine tip in the form of a cannula no. 14 or 16, in order to maintain a bloodless field of operation for the bonding procedure. Occasionally, a persistent bleeding point from the bone surface may require the surgeon to use either pressure from a blunt instrument or the application of bone wax to occlude the tiny vessel. Soft tissue bleeding may be controlled with electro-cautery, a hot burnisher or, occasionally, ligation of the vessel. Bleeding does not occur in the follicular space, but seepage from adjacent areas may be present and is best arrested with the use of light pressure from a strip of gauze, which may be left in place until suturing is ready to begin – but it must not be forgotten! Then, armed with a retractor in one hand and alternating the suction tips as necessary with the other, the surgeon will maintain the access and haemostasis to the immediate area of the newly exposed and impacted tooth. The orthodontist proceeds directly to rinsing the tooth surface with atomized water spray from a standard triple syringe or, if preferred, with sterile saline from a large syringe, through a wide bore needle, to disperse any blood from the tooth surface. The saline is evacuated through the broad suction tip, operated by the surgeon. The fine suction tip is then substituted and is made to hover over the entire exposed crown, close to the tooth surface, with the aim of drawing air over the clean enamel. This achieves effective drying, and the use of sterile saline as a rinsing agent does not appear to undermine the reliability of the bonded union. Liquid etchants should not be used in the exposed surgical field [22] since it is difficult to limit their spread to the exposed soft tissues and bone surfaces and, perhaps

more important, to the area of the CEJ, the PDL and cementum. It should be applied by the orthodontist as a gel on the end of a fine wooden toothpick applicator (nonmedicated), left in place for 30 seconds and then drawn off by the surgeon through the fine suction tip, before the surface is rinsed again with saline to remove the last traces of acid. Continuation of use of the fine tip will draw air over the surface of the crown of the tooth until drying is achieved, when the typical white matte appearance of the etched surface will quickly appear. The surface is now ready for bonding. Many practitioners may feel concern about the adequacy of the desiccation and may also prefer to be sure that no salt crystals remain from the dried saline. Experience shows the concern to be groundless. Nevertheless, to allay these fears, a final rinse with atomized water from the triple syringe may be followed by a fine compressed airstream to achieve the appropriate degree of dryness of the enamel surface. For this to be successful, the compressed airstream must be very gentle to avoid splashing up blood from the surgical area, which will contaminate the enamel and cause bond failure. The use of a hair dryer has the advantage of providing a gentle stream of warm air, which may be more effective in drying the etched enamel surface and is a method favoured by some clinicians. The prepared eyelet attachment has a pliable base. An attachment of appropriate size should be selected and adapted between the plier and the gloved hand of the orthodontist, to conform to the target bonding site. A cut length of 0.011 in (0.275 mm) or 0.012 in (0.3 mm) dead soft stainless steel ligature wire is threaded through the eyelet and, with the use of the mosquito or Matthieu forceps, is twisted into a medium-tight and firm pigtail, which should swing freely in the eyelet. Strictly, any type of bonding agent may be used, including light-activated and chemically-activated systems. Attachments will be discussed in more detail in the next chapter. Nevertheless, one or two points regarding bonding under conditions of surgical exposure are pertinent in the present context. In the first edition of this book, we expressed a preference for a chemically activated ‘no-mix’ system. In this system, the attachment is seized in the reverse-action bonding tweezers and its mesh base painted with the catalyst. A small quantity of bonding paste is placed on the attachment, which is delivered to the operating area. The etched enamel is checked for dryness once again and then painted with the liquid catalyst. The attachment is pressed firmly into place on the crown of the tooth until paste oozes from underneath the mesh base. Even without waiting for initial setting, the viscosity of the paste will hold the attachment in place without the need for any support, and careful finetip suction in the surrounding area is probably all that is needed to guarantee bonding success.

Surgical Exposure of Impacted Teeth  51  The mid-buccal aspect of the tooth possesses a smooth curved surface, to which the base of a standard bracket, button or eyelet may be easily and reliably bonded. The contour of the base closely conforms to the tooth surface at this site, which offers virtually ideal conditions, provided that good haemostasis is obtained. However, following placement of the attachment, several minutes of continued isolation of the area are needed to permit uncontaminated setting, which often requires the deft use of retractors and fine suction to prevent incipient haemorrhage. When the available bonding site is elsewhere on the tooth, the base of the attachment is unsuited and the undulating palatal surface of a maxillary canine, in particular, makes adequate adaptation quite impossible. The attachment base then has a two- or three-point contact with the tooth only. Under these circumstances, chemical bonding has strong disadvantages, since the thickness of the ‘no-mix’ bonding paste will be excessive in large areas and the liquid catalyst will not penetrate sufficiently to harden all the composite material. The bond will be undermined and failure is possible [24]. Using a light-cured adhesive, the full thickness of the material will be hardened more satisfactorily and the bond will be more reliable. Given the high-intensity LED curing lights now available, full hardening of the adhesive takes place within seconds, which is a boon in this delicate procedure. Furthermore, the units are wire-less and do not entail dragging a cable from an electric socket across the sterile operating field, which makes light curing the method of choice for bonding attachments to impacted teeth, at the time of surgery. Many operators prefer to use mosquito or Matthieu forceps to carry the attachment to its place and to hold it there until setting has occurred. Unfortunately, the freeing of the attachment from the forceps is achieved by changing the hand grip and unlocking the ratchet that holds the handles closed. These manoeuvres produce considerable jolting and jarring of the attachment, which may easily lead to loss of control in its accurate placement. Accordingly, it is better to use the reverse-action bonding tweezers, which may be much more gently disengaged once the attachment has been placed and left unsupported during the curing process. The viscosity of the bonding paste should be adequate to prevent any movement. If continuous pressure is desired during the setting period, a ligature director may be substituted for the tweezers and placed with its notch engaged astride the eyelet loop and pressing against it, while the light is used. To free the ligature director once setting is complete, it is merely withdrawn in the direction of its long axis, without generating any undue lateral jarring. The newly bonded attachment should always be tested for strength by firmly pulling at the pigtail ligature before the flap is sutured. As part of the original orthodontic treatment plan, an accurate radiographic assessment of the position of the

impacted tooth will have been made and an approach to its orthodontic resolution formulated. With the impacted tooth now in full view, the orthodontist must re-evaluate the earlier decision and confirm or revise the traction direction accordingly. If this is to be performed in a direct line to the prepared place in the dental arch, then the pigtail ligature will be swivelled on the eyelet until it points in that direction. The surgeon will then suture the flap back over the wire, leaving its end freely protruding through the cut and sutured edges. As we shall discuss with regard to a palatally impacted maxillary canine (Chapter 6), sometimes the direction of the traction cannot be pointed straight to the labial archwire because of the proximity of the roots of adjacent teeth. In this case, the wire may initially need to be drawn vertically downwards, towards the tongue or in a posterior direction. To achieve this, the pigtail cannot be drawn through the sutured edges of the flap, but rather taken through the middle of the palatal area. This means the reflected flap must be divided into two, one on either side of the pigtail, to accommodate this (Figure 3.6c). A better alternative is to pass the pigtail through a small pinhole in the palatal mucosa, prior to the replacement and suturing of the flap. When suturing is completed and the palatal area completely closed off, the orthodontist should shorten the pigtail and turn it up into a hook or circle, to be attached to an active palatal arch, ballista or auxiliary archwire. The replacement of the flap will hide the impacted tooth from sight once again and it will become evident in later stages that it is prudent to photograph the tooth and its attachment before closure is performed (Figure 3.6b). By recording its position in this way, subsequent decisions related to the direction of orthodontic traction may be made more reliably when the patient returns for routine orthodontic adjustment and further activation of the traction mechanism at future orthodontic visits. The application of traction should be immediate, regardless of which method is used. It will be appreciated that later manipulation of the ligature pigtail, as it passes through the soft tissues, is very unpleasant and even painful for the patient. While subsequent manipulation may only be necessary for two or three additional adjustment visits before the tooth is erupted and the pigtail free of the soft tissue, there is much to be said for the first of these being fully exploited with the application of appropriate traction while a local anaesthetic is operational, i.e. at the time of surgical exposure. If an auxiliary labial archwire or a ‘ballista’ spring has been tied into the arch in their passive mode prior to the surgery, as recommended above, then lightly pushing the loop from its vertical, inactive position towards the mid-palate and turning the pigtail ligature around it will provide appropriate extrusive force which will be active over a wide range of movement, and will remain active for several weeks. Similarly, an auxiliary palatal arch may be slotted into the palatal horizontal molar tubes, and then

52  Orthodontic Treatment of Impacted Teeth raised into the pigtail ligature and held there by similar means (see Figure 6.34). Whichever of these devices is used, this orthodontic manoeuvre should take no more than a minute or two and can be done while the surgical instruments are being cleared away. The reliability of the bonding procedure under the circumstances described here has been shown to be extremely high [24]. Nevertheless, in the past, bonding in the presence of an open and bleeding wound, involving both soft and hard tissues, has been strongly contraindicated, since it was thought to be inconsistent with the attainment of a dry and uncontaminated field. This attitude, on the part of the orthodontist, was probably nurtured more out of a reticence to be present at the surgical episode than out of any experience of a high incidence of failure in attachment bonding at that time. It is important to emphasize the need to properly adapt the base of the attachment to the shape of the recipient surface of the crown of the tooth. Thus, the use of standard brackets with ‘anatomic’ bases, as supplied by the manufacturer, was shown in that study [24] to fare considerably better in the mid-buccal position of the impacted tooth (80.6%) than on any other surface, particularly the palatal surface, where the chances of its survival were 58.3% – a failure rate of almost 1 in 2! Better still, and at a 96.7% level of reliability, a small attachment (such as an eyelet) on a pliable base, properly and individually adapted to the form of the recipient site, will allow the orthodontist to work with the greatest degree of confidence. In Chapter 12, we shall refer to a wide range of reasons why failure to resolve an impaction occurs and among these, ankylosis is arguably the most commonly claimed by the often embarrassed orthodontist [53]. Why ankylosis should occur is largely unknown, but there may be one or two well-intentioned approaches that the surgeon may use with the best of intentions and to facilitate different aspects of the exposure procedure, but which could contribute to this unfortunate pathological sequela. Thus, overzealous and wide exposure of the tooth, down to the CEJ and beyond, will cause tearing of the fibres of the periodontal ligament and exposure of the surface of the cementum. It most often heals without further complications. Notwithstanding, an aggressive resorption process may be initiated in the exposed cervical area of the root due to chronic inflammation in the granulation tissue which is in contact with the dentine, which may prevent the marginal gingival epithelium from forming a protective cervical cell layer in an angular defect. Pushing elevators down the side of the tooth aimed at ensuring a good degree of mobility causes damage to the cementum which may then heal with an ankylotic union. During the bonding process, the necessary drying of the enamel surface will also cause desiccation of these sensitive tissues. Should liquid etchant reach the area, then chemical

damage will also occur, which will cause cell death. Many dental practitioners will use liquid etchant to control bleeding from the gingiva into a prepared carious cavity to facilitate placement of a dental restoration. If this method is used for haemostasis in the present context, the damage that occurs will not be revealed for some time. However, there is reason to believe that this may be a potent cause of ankylosis or of aggressive cervical root resorption, both of which will effectively prevent further movement of the affected tooth (see Chapter 7). From the above account, it will be appreciated that the presence of the orthodontist at the surgical intervention has much to commend it. In the first place, the orthodontist is able to see the exact position of the crown, the direction of the long axis and the deduced location of the root apex. The height of the tooth and its relation to adjacent roots may all be noted and the orthodontist may plan the strategy of its resolution by direct visualization. The orthodontist will be in a position to decide exactly where he/she would like to see the attachment placed from the mechano-therapeutic point of view and will bond it there. The orthodontist is also the best person to fabricate and place a suitable and efficient auxiliary to apply a directional force of optimal magnitude and a wide range of movement and to place it at the time of surgery. It is not fair to expect the oral surgeon to be aware of how different attachment positions may affect the orthodontic or periodontic prognosis; nor should it be expected of him/her to be sufficiently experienced with the bonding technique to do this. For most oral surgeons, bonding is not a procedure that they routinely carry out. The presence of the orthodontist allows for bonding to be performed efficiently, with the surgeon and the nurse maintaining haemostasis and the necessary dry field. So, if a surgeon were to take exception to the present recommendation that the orthodontist be present at the exposure, with the words ‘even the lowliest oral surgeon can place a bracket’ or that it is ‘a waste of time’ [54], that oral surgeon would be sorely missing the point and the wider context of ensuring quality care and overall treatment success. The ultimate responsibility for the success of the case, from the initiation of orthodontic treatment up to the point where the impacted tooth is brought into full alignment, rests firmly on the shoulders of the orthodontist. It would seem irresponsible to abrogate this crucial stage of the treatment, where a force is to be applied to the newly exposed impacted tooth and where so much is at stake that affects the future of the case, to another party. Absenting himself from the procedure, as has been advocated by many orthodontists and surgeons alike, leaves the surgeon to make orthodontic decisions for which he is not equipped, thereby endangering the outcome and inviting legal proceedings, from which the orthodontist will not be immune [55].

Surgical Exposure of Impacted Teeth  53 

References   1.  Becker A, Kohavi D, Zilberman Y. Periodontal status following the alignment of palatally impacted canine teeth. Am J Orthod 1983; 84: 332–336.   2.  Kohavi D, Becker A, Zilberman Y. Surgical exposure, orthodontic movement and final tooth position as factors in periodontal breakdown of treated palatally impacted canines. Am J Orthod 1984; 85: 72–77.   3.  Kohavi D, Zilberman Y, Becker A. Periodontal status following the alignment of buccally ectopic maxillary canine teeth. Am J Orthod 1984; 85: 78–82.   4.  Boyd R. Clinical assessment of injuries in orthodontic movement of impacted teeth. I. Methods of attachment. Am J Orthod 1982; 82: 478–486.   5.  Boyd R. Clinical assessment of injuries in orthodontic movement of impacted teeth. II. Surgical recommendations. Am J Orthod 1984; 86: 407–418.   6.  Odenrick L, Modeer T. Periodontal status following surgicalorthodontic alignment of impacted teeth. Acta Odontol Scand 1978; 36: 233–236.   7.  Di Biase DD. The effects of variations in tooth morphology and position on eruption. Dent Pract Dent Rec 1971; 22: 95–108.   8.  Andreasen JO, Andreasen FM. Textbook and Color Atlas of Traumatic Injuries to the Teeth. Copenhagen: Munksgaard, 1994.   9.  Korbendau J-M, Guyomard F. Chirurgie parodontale orthodontique. Velizy-Villacoublay Cedex, France: Editions CdP, 1998. 10.  Kokich VG. Surgical and orthodontic management of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2004; 126: 278–283. 11.  Moro N, Murakami T, Tanaka T, Ohto C. Uprighting of impacted lower third molars using brass ligature wire. Aust Orthod J 2002; 18: 35–38. 12.  Becker A, Shochat S. Submergence of a deciduous tooth, its ramifications on the dentition and treatment of the resulting malocclusion. Am J Orthod 1982; 81: 240–244. 13.  Ilizarov G, Devyatov A, Kamerin V. Plastic reconstruction of longitudinal bone defects by means of compression and subsequent distraction. Acta Chir Plast 1980; 22: 32–46. 14.  Altuna G, Walker DA, Freeman E. Rapid orthopedic lengthening of the mandible in primates by sagittal split osteotomy and distraction osteogenesis: a pilot study. Int J Adult Orthod Orthognath Surg 1995; 10: 59–64. 15.  Vanarsdall RL, Corn H. Soft-tissue management of labially positioned unerupted teeth. Am J Orthod 1977; 72: 53–64. 16.  Vanarsdall RL. Efficient management of unerupted teeth: a timetested treatment modality. Semin Orthod. 2010, 16: 212–221. 17.  Hunt NP. Direct traction applied to unerupted teeth using the acidetch technique. Br J Orthod 1977; 4: 211–212. 18.  McBride LJ. Traction – a surgical/orthodontic procedure. Am J Orthod 1979; 76: 287–299. 19.  Gensior AM, Strauss RE. The direct bonding technique applied to the management of the maxillary impacted canine. J Am Dent Assoc 1974; 89: 1332–1337. 20.  Nielsen LI, Prydso U, Winkler T. Direct bonding on impacted teeth. Am J Orthod 1975; 68: 666–670. 21.  McDonald F, Yap WL. The surgical exposure and application of direct traction of unerupted teeth. Am J Orthod 1986; 89: 331–340. 22.  Kokich VG, Mathews DP. Surgical and orthodontic management of impacted teeth. Dent Clin North Am 1993; 37: 181–204. 23.  Crescini A, Clauser C, Giorgetti R, Cortellini P, Pini Prato GP. Tunnel traction of intraosseous impacted maxillary canines: a threeyear periodontal follow-up. Am J Orthod Dentofac Orthop 1994; 105: 61–72. 24.  Becker A, Shpack N, Shteyer A. Attachment bonding to impacted teeth at the time of surgical exposure. Eur J Orthod 1996; 18: 457–463. 25.  Wong-Lee TK, Wong FCK. Maintaining an ideal tooth–gingiva relationship when exposing and aligning an impacted tooth. Br J Orthod 1985; 12: 189–192. 26.  Becker A, Brin I, Ben-Bassat Y, Zilberman Y, Chaushu S. Closederuption surgical technique for impacted maxillary incisors: a postorthodontic periodontal evaluation. Am J Orthod Dentofac Orthop, 2002; 122: 9–14.

27.  Chaushu S, Brin I, Ben-Bassat Y, Zilberman Y, Becker A. Periodontal status following surgical-orthodontic alignment of impacted central incisors by an open-eruption technique. Eur J Orthod 2003; 25: 579–584. 28.  Wisth PJ, Nordervall K, Boe OE. Periodontal status of orthodontically treated impacted maxillary canines. Angle Orthod 1976; 46: 69–76. 29.  Woloshyn H, Artun J, Kennedy DB, Joondeph DR. Pulpal and periodontal reactions to orthodontic alignment of palatally impacted canines. Angle Orthod 1994; 64: 257–264. 30.  Vermette ME, Kokich VG, Kennedy DB. Uncovering labially impacted teeth: apically positioned flap and closed-eruption technique. Angle Orthod 1995; 65: 23–32. 31.  Chaushu S, Dykstein N, Ben-Bassat Y, Becker A. Periodontal status of impacted maxillary incisors uncovered by two different surgical techniques. J Oral Maxillofac Surg, 2009; 67: 120–124. 32.  Becker A. An interview with Adrian Becker. World J Orthod 2004; 5: 277–282. 33.  Parkin N, Benson PE, Thind B, Shah A. Open versus closed surgical exposure of canine teeth that are displaced in the roof of the mouth. Cochrane Database of Systematic Reviews 2008, 4. CD006966. DOI: 10.1002/14651858.CD006966.pub2. 34.  Schmidt AD, Kokich VG. Periodontal response to early uncovering, autonomous eruption, and orthodontic alignment of palatally impacted maxillary canines. Am J Orthod Dentofac Orthop 2007, 131: 449–455. 35.  Heaney TG, Atherton JD. Periodontal problems associated with the surgical exposure of unerupted teeth. Br J Orthod 1976; 3: 79–85. 36.  Vanarsdall RL, Corn H. Soft tissue management of labially positioned unerupted teeth. Am J Orthod Dentofac Orthop 2004; 125: 284–293. 37.  Vanarsdall RL Jr. An interview with Robert L. Vanarsdall, Jr. World J Orthod 2004; 5: 74–76. 38.  Vanarsdall RJ. Periodontal/orthodontic interrelationships. In Graber TM, Vanarsdall RL, eds. Orthodontics. Current Principles and Techniques, 4th edn. St Louis, MO: Mosby, 2000: 822–836. 39.  Becker A. Extreme tooth impaction and its resolution. Semin. Orthod, 2010, 16: 222–233. 40.  Ten Cate AR. Oral Histology: Development, Structure and Function, 4th edn. St Louis, MO: Mosby, 1994: 270. 41.  Blackwood HJJ. Resorption of enamel and dentine in the unerupted tooth. Oral Surg Oral Med Oral Pathol 1958; 11: 79–85. 42.  Cahill DR, Marks SC Jr. Tooth eruption: evidence for the central role of the dental follicle. J Oral Pathol. 1980; 9: 189–200. 43.  Hu JC-C, Nurko C, Sun X et al. Characteristics of cementum in cleidocranial dysplasia. J Hard Tissue Biol 2002; 11: 9–15. 44.  Becker A, Caspi N, Chaushu S. Conventional wisdom and the sur­ gical exposure of impacted teeth. Orthod Craniofac Res, 2009; 12: 82–93. 45.  Danan M, Zenou A, Bouaziz-Attal A-S, Dridi S-M. Orthodontic traction of an impacted canine through a synthetic bone substitute. J Clin Orthod 2004; 38: 39–44. 46.  Chaushu G, Becker A, Zeltser R, Branski S, Chaushu S. Patients’ perceptions of recovery after exposure of impacted teeth with a closederuption technique. Am J Orthod Dentofac Orthop 2004; 125: 690–696. 47.  Chaushu S, Becker A, Zeltser R, Vasker N, Chaushu G. Patients’ perception of recovery after surgical exposure of impacted maxillary teeth treated with an open-eruption surgical-orthodontic technique. Eur J Orthod 2004; 26: 591–596. 48.  Chaushu G, Becker A, Chaushu S. Patients’ perception of recovery after exposure of impacted teeth: a comparison of closed versus openeruption techniques. J Oral Maxillofac Surg 2005; 63: 323–329. 49.  Jacoby H. The ballista spring system for impacted teeth. Am J Orthod 1979; 75: 143–151. 50.  Becker A, Zilberman Y. A combined fixed-removable approach to the treatment of impacted maxillary canines. J Clin Orthod 1975; 9: 162–169. 51.  Becker A, Zilberman Y. The palatally impacted canine: a new approach to its treatment. Am J Orthod 1978; 74: 422–429. 52.  Kornhauser S, Abed Y, Harari D, Becker A. The resolution of palatallyimpacted canines using palatal-occlusal force from a buccal auxilliary. Am J Orthod Dentofacial Orthop 1996; 110: 528–534.

54  Orthodontic Treatment of Impacted Teeth 53.  Becker A, Chaushu G, Chaushu S. An analysis of failure in the treatment of impacted maxillary canines. Am J Orthod Dentofac Orthop 2010; 137: 743–754. 54.  Haskell R. Book review. Br J Oral Maxillofac Surg 1999; 37: 157–158.

55.  Haney E, Gansky SA, Lee JS, Johnson E, Maki K, Miller AJ, Huang JC. Comparative analysis of traditional radiographs and cone-beam computed tomography volumetric images in the diagnosis and treatment planning of maxillary impacted canines. Am J Orthod Dentofac Orthop 2010: 137(5): 590–597.

4 Treatment Components and Strategy

Orthodontic treatment duration

56

The anchor unit

56

Attachments

57

Intermediaries

59

Elastic ties and modules versus auxiliary springs

59

Temporary anchorage devices (TADs)

62

Infra-occluded deciduous teeth

64

Magnets

64

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

56  Orthodontic Treatment of Impacted Teeth

Orthodontic treatment duration The opening of adequate space in the arch may initiate movement in an unimpeded impacted tooth, which may start moving in the appropriate direction, sometimes quite quickly [1]. By the time the space is of a suitable size and arrangements for the surgery have been made, a new periapical radiograph may show much positive change in its position and lead the clinician to believe that spontaneous eruption will render the surgery unnecessary. If the eruption is likely to occur imminently, or at least within a reasonable period, there is merit in waiting for this to occur. If, on the other hand, eruption will take many months, then the orthodontist must weigh the benefits of avoiding surgery against the drawbacks involved in leaving orthodontic appliances in place for all this time or removing them before all the teeth are in their appropriate places. Orthodontic appliances raise the level of vulnerability of the teeth to caries and of the periodontium to inflammation – the longer they are in place, the greater is the risk. Removing the appliances before time runs the different risk of having to replace them later to correct a malposition of the newly erupted and erstwhile impacted tooth or to accept a compromised, inadequate, outcome. In order to solve this dilemma, the clinician may elect to advise surgical exposure and orthodontic traction to expedite the eruption of the tooth and complete the treatment in a very much shorter time. When orthodontic treatment has provided space and surgery is undertaken to remove a physical obstacle, a similar dilemma may arise. In the absence of the obstacle, the impaction is potentially resolvable, without further treatment. However, the surgical intervention involved in removing the obstacle offers the opportunity of access to the unerupted tooth. Subsequent healing of the wound will deny that access and, in the event that eruption does not take place, a second surgical intervention in the same area will be necessary and much time will have been wasted confirming that spontaneous eruption will not occur. Clearly, then, the time factor must not be ignored. Ortho­ dontic appliances are in place and, perhaps, the space in the arch is unsightly. Without question, orthodontically aided eruption will speed up the resolution enormously and, this being so, the patient’s best interests are to be served by including this option among the factors to be considered at the planning stage. When the existence of an impaction is only a small part of an overall complex malocclusion, the time factor becomes more critical. It is quite conceivable and reasonable to estimate that a given overall problem alone may require two years of treatment. The complete alignment of an awkwardly placed impacted tooth may add a further year or more to this [2–4]. To permit the luxury of a wait-and-see period is to add this to an already extended three-year period, during which appliances are worn. While the ortho-

dontist may well be rewarded by a much improved position of the impacted tooth, a deteriorating state of oral health, due to poor oral hygiene, may deprive the achievement of all meaningful content. It becomes relevant to refer to our original definitions in Chapter 1, in which we noted that ‘A permanent tooth with delayed eruption is an unerupted tooth whose root is developed in excess of this length and whose spontaneous eruption may be expected, in time. A tooth which is not expected to erupt in a reasonable time, in these circumstances, is termed an impacted tooth.’ Thus, in the present context and while the tooth may be expected to erupt spontaneously ‘in time’, this period may not be considered ‘reasonable’ in relation to the prospect of detrimental iatrogenic effects on the remainder of the dentition engendered by this extra and often considerable waiting period. This then redefines the tooth as impacted, and a proactive surgical exposure should be considered preferable.

The anchor unit At this juncture, it is not the intention to go into the details of appliance therapy. This will come later, as the different groups of impacted teeth that are seen in practice are dealt with. However, some general principles are in order. For most malocclusions, quality treatment is best provided by the use of one or other of the recognized fixed appliance treatment techniques. If the dental arches are correctly related and adequate space is present, then the teeth are initially ‘levelled’ to a labial archwire of standardized archform and a given coefficient of elasticity. Later, heavier round or rectangular archwires are substituted to perform root movements which will pave the way to achieving an optimal result. Incorrectly related dental arches will benefit from the use of other appliances, such as headgears, functional appliances or intermaxillary elastics, prior to or in addition to the fixed appliances, while space may be provided by the extraction of teeth or by lengthening the arches mesio-distally or expanding them laterally. When dealing with a malocclusion that incorporates an impacted tooth, modifications must be made in this procedure. Unlike other teeth in the mouth, the impacted tooth may be severely displaced from its normal position in all three planes, and much anchorage will be expended in bringing it into alignment. Accordingly, a rigid anchor base must be developed against which to pit the forces required to reduce the impaction. At the age at which an impacted maxillary canine is treated, the full permanent dentition (with the exception of third molars) is usually present. Accordingly, a fully multibracketed appliance should normally be placed and the entire dentition treated with the use of light archwires through the stages of levelling and the opening of adequate space in the arch for the impacted tooth. A heavy and more

Treatment Components and Strategy  57  rigid archwire is then placed into the brackets on all the teeth of the fully aligned and complete dental arch. The aim of this is to provide a solid anchorage base [5] which will not allow distortion of the archwire to occur as the result of the forces that will eventually be applied to the impacted tooth after its exposure. The effect on the anchor unit of forces that are designed to resolve a grossly displaced canine should not be underestimated, particularly if they are applied for an extended duration. By contrast, at the time an impacted upper central incisor needs to be treated, only first permanent molars and three permanent incisor teeth are present in the maxillary arch. Accordingly, alternative means of making the appliance system rigid must be employed before light forces may be applied to the impacted tooth, in order not to compromise the remainder of the dentition.

Attachments To be in the position of being able to influence the future development of an impacted tooth, it is necessary to place some form of attachment on the tooth. These attachments have changed over the years, reflecting the advances made in the field of dental materials. Lasso wires In the years prior to the mid-1960s, a lasso wire (Figure 4.1) twisted tightly around the neck of the canine was employed widely and was used in our earlier cases, in the initial stages. It will be readily appreciated that the shape of the crown of a tooth is such that its narrowest diameter is at the cementoenamel junction (CEJ), which is where the lasso wire will inevitably settle. This will result in irritation of the gingiva and prevent reattachment of the healing tissues in this vital

Fig. 4.1  Lasso wire encircling the neck of an impacted canine.

area. It has also been reported that external resorption and ankylosis have been produced in the area of the CEJ following employment of this method [6]. Given the excellent alternatives that are available today, the lasso wire is obsolete. Threaded pins Several systems of threaded pins (Figure 4.2) have been available for many years. Their specific purpose is to provide retention for an amalgam or composite core, to allow the provision of a cast crown in a severely broken down tooth. These threaded pins may also be used to provide the attachment for an impacted tooth. This is a method which was used in the past [7, 8] and has been totally superseded. Its disadvantages include the fact that it is dentally invasive, necessitating a subsequent restoration. Given the difficulties of access to many impacted teeth and the desirability of limiting surgical exposure as much as possible, the orientation of the long axis of the tooth may be difficult to determine and the drilled hole may inadvertently enter the pulp – unerupted teeth often have large pulp chambers! Even in the most favourable of circumstances, it seems that this unnecessarily aggressive method produces avoidable damage to a virgin tooth, when there are eminently suitable, non-invasive methods and efficacious alternatives, as we shall discuss below. Nevertheless, the method was still in use and apparently recommended until quite recently [5, 9]. Orthodontic bands Preformed orthodontic bands largely replaced the lasso wire, and clinical experience with them showed them to be considerably more compatible with ensuring the health of the periodontal tissues. As with the lasso wire, however, the

Fig. 4.2  Threaded pins set into prepared holes, drilled and tapped into the enamel and dentine of the surgically exposed canines.

58  Orthodontic Treatment of Impacted Teeth use of a band dictated the very wide surgical clearance of tissue on all sides of the tooth (see Figure 6.35c), in order to permit the introduction of the band, to adequately control haemorrhage around the crown and to avoid contamination from oozing blood inside the cement-filled band, at the time of placement. Bonded attachments Since the introduction of enamel bonding, all the abovementioned methods have become obsolete. The employment of the acid-etch composite bonding technique to the crown of a tooth has much merit [10–12], notably in terms of simplicity and reliability of the bond. Its greatest advantage is that it requires relatively little exposed surface of enamel to be successful, a fact which may contribute much to the subsequent periodontal health of the treated result. It is, presently, without doubt the method of choice from almost every point of view, and should replace other methods in virtually all circumstances. Standard orthodontic brackets As far as the actual choice of type of attachment to be placed on impacted teeth is concerned, there are several salient points to consider regarding the impacted tooth when compared with an erupted tooth that needs to be brought into its position in the dental arch. The wide array of orthodontic brackets, advertised in the catalogues of the various orthodontic manufacturing companies, represent sophisticated designs of attachment that enable the orthodontist to perform any type of movement on a tooth in all three planes. Since many or perhaps most impacted teeth are in need of a wide variety of movements, it may seem logical to place a sophisticated orthodontic bracket on the affected tooth, from the outset. That part of the movement of the impacted tooth, from its initial ectopic position until it reaches the main archwire, represents resolution of the impaction. During this entire period, which is the most difficult part of the treatment of this displaced tooth, it is not possible to achieve more than tipping, extrusion and some rotation until the bracket arrives at and fully engages the main archwire. In other words, the value of the bracket up to that point is no greater than that of a simple eyelet [13]. Indeed, on several counts, the potential of the eyelet outweighs that of the conventional bracket during the resolution stage. The base of a conventional bracket is wide, rigid and difficult to adapt to the shape of another part of the tooth’s surface other than the mid-buccal, for which it has been designed. Thus, composite bonding elsewhere on a tooth is very likely to lead to failure [13]. Orthodontic brackets are highly specialized, each having a slot milled to a very precise blueprint, specific to the particular tooth for which it is intended. The mesio-distal angulation differs between one tooth and another, the ‘in–out’ bucco-lingual depth of the slot will vary, the torque angulation will not be the same

for the individual teeth, and the height at which the bracket should be placed on an incisor will not be the same as that on the canine. These are the principles on which the socalled ‘straight wire’ appliances are built. However, it should be immediately obvious that all this highly sophisticated programmed engineering is only meaningful if the bracket is bonded in its appropriate, predetermined position on the crown of the tooth. We shall see in later chapters that it is very frequently impossible or unwise, at the time of the surgical exposure of an impacted tooth, to bond an attachment in this position on the crown. This site on the crown of the tooth may not be accessible due to its relationship to the root of an adjacent tooth, or an excessive amount of soft and hard tissue might need to be surgically removed, thereby producing unnecessary damage in order to provide this access. The standard orthodontic bracket in any technique is relatively large, possesses a wide, high and sharp profile, and, even when placed in alternative positions on the tooth, by force of circumstance at the time of surgery, it may find itself deeply sited in the surgical wound. The bracket’s shear bulk creates irritation as the tooth is later drawn through the soft tissues, particularly the mucosa (Figure 4.3). A ligature wire or elastic thread tied to it must also originate deep in the wound and will be stretched across the replaced flap tissue towards the labial archwire. This increases the possibility of impingement with the investing tissues and leads to inflammation and to probable permanent periodontal damage. As the displaced tooth moves towards its place in the arch, exuberant gingival tissue bunches up in front of it, which will also lead to impingement by a conventional orthodontic bracket. The existence of the exuberant gingival tissue in advance of the tooth can often cause ‘pinching’ between it and the teeth in the arch immediately adjacent

Fig. 4.3  As the impacted tooth is about to erupt, the high-profile Siamese edgewise bracket has fenestrated the swollen gingival tissue.

Treatment Components and Strategy  59 

Fig. 4.4  Eyelets welded to a pliable band material base, backed by steel mesh.

to it. This is less likely to occur if a deliberately generous space is provided in the arch for the tooth. This precaution may avoid unnecessary periodontal damage. A simple eyelet An eyelet, welded to orthodontic band material with a mesh backing (Figure 4.4), is soft and easy to contour, permitting its adaptation to the bonding surface to be more intimate, which makes for superior retentive properties. Its relatively small size and low profile makes the mid-buccal position of several of the more awkwardly placed teeth considerably more accessible when compared to the placing of a conventional bracket. Its modest, low-profile dimensions are also less irritant to the surrounding tissues, particularly during the critical phase as it breaks through epithelial tissues in the final stages of its eruption into the oral cavity. For these reasons, a small eyelet is recommended as the initial attachment, placed at the time of surgery and removed only when the tooth has progressed to the point where it is in close proximity to the archwire. At that time, it should be substituted for the same type of sophisticated bracket which is being used on the other teeth, thereby heralding the initiation of the more intricate root manipulations of the tooth (rotating, uprighting and torqueing).

Intermediaries We have seen in Chapter 3 that there are important periodontal advantages to be gained by full closure of the surgical flap at the end of the visit during which the surgical exposure is performed. Thus, the impacted tooth is recovered by the surgical flap and is lost from sight, unless the impacted tooth is fairly superficially placed. The only manner in which contact may be maintained with it is through the some form of ligature wire, gold chain or elastic thread, which is attached to the eyelet, before it is bonded to the tooth. This may be termed an intermediary or connector.

Since elastic thread can only be tied once, it is not recommended for an attachment that is not clearly visible and accessible in the mouth. Gold chain has found a surprising degree of acclaim and acceptance worldwide in view of the fact that it appears to be unnecessarily sophisticated, expensive and not widely available, although it is undoubtedly suitable and sufficiently strong for the purpose. There is perhaps only one practical drawback to its use, which relates to its physical properties. If a closed surgical approach is used, following bonding of its attachment base to a tooth, the end of the chain needs to be held in a locking tweezers or artery forceps until it is ligated to its active traction element, be it a spring or elastic thread. If this is not done, then the fine-linked chain may collapse down and slip between the recently sutured edges of the flaps and be lost from sight. This may also happen when an open surgical approach is performed, with the collapsed chain falling between the wound edges and into the cervical area of the newly exposed tooth. It may also occur during later visits for re-ligation of the still only partially erupted tooth. Subsequent search for the lost chain is very uncomfortable for the patient and may even require a reopening of the healing soft tissue cover. The use of a stainless steel ligature is far easier from every point of view, and is readily at hand in both the orthodontic and the surgical operatory. Such a ligature is passed through the eyelet and twisted into a long braid with an artery forceps before bonding is undertaken. The braided wire or pigtail hangs loosely in the eyelet until bonding and suturing have been completed, and it should be of sufficient substance for it to be rolled up into a loop, which will not easily be unravelled by application of the extrusive force. On the other hand, it must not be so thick that the effort needed to form the loop will seriously test the bond strength of the newly placed attachment. In practice, the use of a dead soft stainless steel ligature wire of 0.011 in or 0.012 in gauge is generally the most suitable. It has been recommended that the pigtail be braided in such a way that each two or three turns of the braid are followed by a small loop, then two or three more turns, another loop, and so on. In this way, the braid comprises a convenient chain of loops, which may be shortened as necessary by cutting off the excess, while exploiting the loop closest to the gingival tissue [14]. However, ‘rolling up’ the terminal loop of a simply twisted stainless steel ligature (Figure 4.5) as the tooth progresses is simpler and ‘userfriendly’.

Elastic ties and modules versus auxiliary springs At first glance, elastic ties of one sort or another present the orthodontist with the most convenient means of applying light forces to a tooth, with a good range of action. However,

60  Orthodontic Treatment of Impacted Teeth their use is more disappointing than one may initially realize. The manufacturer’s spool of elastic thread usually comes in the form of fine hollow tubing, which is easier to tie than a solid thread. Most orthodontists tie the thread with a simple knot which, when tying string, will not unravel. This is done very empirically and there can be no control on the amount of force applied. Furthermore, when tying elastomeric thread, the knot tends to loosen and much of the original force of the tie will then be lost. When under tension, all materials used to make this elastic thread suffer a high degree of force decay, which is very rapid and very significant. The force levels of chains of various lengths are known to decay to below that required for tooth movement, in a period of between one and three weeks, depending upon the amount of tension initially applied [15, 16]. A shorter piece of stretched elastic (Figure 4.5) will have a very short range, and runs the risk of applying an initial

Fig. 4.5  A direct tie using a very short length of elastic thread.

(a)

excessive amount of pressure if the tie is good – or no effective pressure if the tie loosens. The immature periodontal membrane of the recently exposed tooth and the strength of its bonded attachment could be severely tested. In the case of an unerupted tooth close to the line of the arch, traction applied directly from its attachment to the archwire will generally be very inefficient, requiring frequent changes and producing only a very slow response. It is impossible to measure or control such a force, for all practical purposes. It is prudent to use more distant sites from which to apply traction to the unerupted tooth in order to include a greater length of stretched elastic thread to increase the range of the traction force and, thereby, its effectiveness in moving the tooth over a longer period of time. To do this, the elastic thread needs to be drawn to the target area on the archwire, through the agency of a loop bent into the archwire at that point. The thread may then be tied back to the hook on the molar tube of the same side, with care being taken to insert a stop in the archwire, mesial to the tube, in order to prevent mesial movement of the molar. The ‘slingshot’ elastic is an excellent alternative for the situation in which space for an unerupted or partially erupted and buccally, palatally or superiorly displaced tooth has been opened. A cut piece of steel tubing may be placed on the archwire between the brackets in order to maintain the space, and an elastic chain or E-link is stretched across the gap between the brackets on the two adjacent teeth. The middle of the chain is then seized with an artery forceps or Howe plier and stretched over the attachment on the ectopic tooth or on the twisted steel ligature coming through the sutured edge of the replaced surgical flap (Figure 4.6a, b). As a general rule, elastic thread should only be used as a go-between, connecting the non-elastic steel pigtail to a

(b)

Fig. 4.6  (a) The slingshot elastic. A palatally impacted canine has erupted into the palate (see Chapter 6). The elastic module, placed between the bracket of lateral incisor and first premolar, is stretched towards the canine and tied into the buccal eyelet. The steel tube on the archwire maintains the space. (b) The slingshot used on a buccal canine.

Treatment Components and Strategy  61  similarly non-elastic and heavy archwire. If a lighter archwire is used, then the tie should be made with a steel ligature – the archwire providing the elastic displacement. Nickel–titanium alloy wires may be used with great effect in this context, but the distortion of the archwire will bring about alteration in both the horizontal and vertical planes, to produce unwanted change in the form of the dental arch and an uneven occlusal plane. So, if a single super-elastic archwire is tied into the brackets on each of the teeth in the levelled and aligned arch and then into an attachment bonded to a severely displaced impacted tooth, control of overall archform will be lost. This will be evident in the three planes of space, causing tipping movements of individual teeth, alterations in the occlusal plane, asymmetric skewing of the shape of the arch and loss of occlusal contacts. The adjacent teeth will be relatively intruded and will be displaced buccally or palatally and tipped towards the space reserved for the impacted tooth. Super-elastic wires should not be used in circumstances of severe displacement without a heavy base arch in place to resist these unwanted movements of the anchor teeth. However, it should be clearly understood that for a nickel–titanium archwire to develop adequate vertically directed eruptive force, it must be free to slide in the bracket slots of the other teeth to which it is ligatured (Figure 4.7a, b). The presence of a heavy base arch tied in with elastomeric ligatures will considerably increase the friction and binding of the superelastic archwire in the brackets. This may not be evident when the last elastomeric is placed and it is difficult to check. Accordingly, the pressure from the deflection that was applied to fully engage the super-elastic wire in the slots may be nullified by the inability of the wire to slide freely through the brackets. The combined use of both a flexible archwire and an elastic thread tie [6] is counterproductive, since the elasticity of the one that exerts the stronger force will be effectively neutralized and offer no physical advantage over a steel

(a)

ligature, while the displacement of the weaker element will be the only factor which is active in moving the teeth. In general, orthodontists use elastic ligatures and chains to move teeth by first elongating the material and drawing the dental elements towards one another. The range of elasticity in this direction is limited and, as pointed out above, decays rapidly. However, the lateral displacement of an elongated elastic thread produces a potentially greater range of movement, within suitable orthodontic force levels, than does a longitudinal displacement. This principle may be applied to moving teeth which lie at a distance from the main arch more efficiently and with controlled and measurable forces (Figure 4.7a, b). Given a little thought in the planning of their use, elastic ties, nickel–titanium auxiliary archwires, chains and modules are extremely helpful in many situations incurred by the presence of impacted teeth. However, properly designed springs, always auxiliary to a heavy base arch, are usually more efficient, since their ability to deliver a measured and controlled force is good, the force decay is lower, the variety of metallic alloys that is available for spring fabrication is broad, their range of action may be very wide and their direction is accurate. These will be illustrated in the discussion of cases as they pertain to the individual groups of teeth, in the succeeding chapters. Thus far, the discussion has centred on maintenance of a steady force through as wide a range as possible, but what force values are appropriate for application to an impacted tooth? If we are to apply traction to a tooth through its long axis, pure extrusion is produced and it implies that there is no resistance from the bone of the coronally divergent socket. The force is applied to the tooth, transferred directly to the supporting fibres of the PDL and as such it requires to be minimal – of the order of 10–15 g – because resistance is small. If greater force is applied, the tooth will become excessively loose and the extrusion achieved will bring with it relatively little supporting alveolar bone.

(b)

Fig. 4.7  (a, b) The use of nickel–titanium auxiliary wire as the active element in applying eruptive force to the unerupted canines, by being thread through the ‘rolled-up’ stainless steel pigtails which are ligated to the eyelets. There is a heavy 0.020 in gauge base arch. The low-profile eyelets, which were bonded at exposure in the closed surgery procedure, can be seen through the translucency of the healthy and uninflamed gingiva.

62  Orthodontic Treatment of Impacted Teeth If there is a modicum of tip introduced into this movement, then the tooth will be brought into close proximity with the bony socket walls, interjecting resistance. Com­ pression of the fibres on the pressure side and stretching on the tension side will generate hyalinization and undermining resorption of the alveolar bone. The force required to elicit eruption will be in the range of 20–40 g/cm2 of root surface. Soft tissue resistance also has to be accounted for. With a simple window technique exposure, the crown of the tooth is freed to erupt directly to its place, with little or no interference from the soft tissues, which means that the full traction force is transmitted to the PDL at the cementum/ alveolar bone interface. By contrast, a closed eruption technique will leave the tooth covered by a soft tissue flap, which will have been firmly sutured into its former place. Some of the applied traction will be dissipated in over­ coming the tension of this soft tissue flap and thus must be increased to reach the threshold needed for tooth movement. When traction is applied to a tooth following an apically repositioned flap procedure, tension is created in the tissues by their being sutured superiorly to the labial side of the tooth. This tension is eruptively directed and may then magnify the applied force, with the effect being cumulative. For this reason, it is sometimes advisable to rely only on pressure from the sutured flap in the first instance, leaving the application of biomechanical traction to a subsequent visit. This is particularly relevant in cases where the tooth is high and labially or buccally displaced.

Temporary anchorage devices (TADs) As a means of obtaining skeletal anchorage, a simple titanium screw temporary implant is often used in routine orthodontics to act as a ‘stake in the ground’, against which to tie elastic modules and chains for the horizontal movement of teeth in various directions [17]. Treating impacted teeth has largely to do with the facility to develop vertical eruptive forces and to bring them to bear on ‘vertically challenged’ teeth. At best, there is very little bone in the same jaw coronal to an impacted tooth at the outset, and certainly less or none after the tooth has been surgically exposed. This leaves precious little opportunity to place a screw device as the base from which traction may be applied to it and only the smallest distance from which to seek to obtain any appreciable range of action. In this limited sense, therefore, using a TAD in the same jaw as the impacted tooth is largely inappropriate. Some of these screws are designed with two slots at right-angles to one another, which serve as the means for driving the screw into the bone but which may also be used as an orthodontic bracket slot, into which a rectangular archwire may be ligated, in the usual manner. Other designs include a slot for an ortho-

dontic archwire in the neck of the screw, beneath the screw head. A short length of rectangular 0.019 × 0.025 in wire may be fabricated into a custom-made, self-supported spring and rigidly tied into the slot on this screw which may be placed at some distance and in a more convenient mesial, distal or apical location position in relation to the impacted tooth. It may then be used to apply traction to the tooth and to erupt it vertically to a considerable degree (see Chapter 10). Using a TAD in the opposite jaw as a direct anchor, in the absence of an orthodontic appliance, has the obvious advantage that there can be no adverse, particularly intrusive, movement of teeth adjacent to the impacted tooth, since these are not included as anchor units. Nevertheless, this demands a patient compliant in the placement of intermaxillary elastics from the device to the pigtail ligature hook which extends from the bonded orthodontic bracket/ button/eyelet on the impacted tooth. These two points of elastic ensnarement are not always easily accessible for the patient or for a dedicated parent and may prove to be impractical. To circumvent this problem, it becomes necessary to place a full orthodontic appliance in the opposing dental arch, which is secured by ligation to a TAD on the affected side. This provides an implant-supported anchor arch configuration. Intermaxillary traction may then be applied from any conveniently located hook or bracket on that appliance directly to the attachment on the impacted tooth, without fear that the teeth in the anchor arch will overerupt. This assumes that the attachment hook on the impacted tooth is accessible for the patient and not painful to manipulate. Impacted teeth such as second molars, which are largely inaccessible for the patient, require a more circuitous approach. This dictates setting up the same implantsupported configuration in the opposing anchor arch but, in this case, a full appliance also needs to be placed in the affected arch. An accessory archwire, custom-designed eruption spring or elastic chain is actively ligated by the orthodontist, between a convenient location on the main arch to the attachment on the impacted tooth, to erupt the tooth. To overcome the tendency of the reactive force to intrude the teeth on that side of the dental arch, vertical elastics are prescribed to be placed by the patient between convenient and easily accessible hooks or buttons between upper and lower appliances. An indirect anchorage system is thus created in which active extrusive forces are applied and controlled by the orthodontist. Loss of anchorage in the same jaw (intrusion of the teeth) is combatted by the patient placing intermaxillary vertical elastics and loss of anchorage in the opposite jaw (extrusion of the teeth) is obviated by ligation to a TAD in that jaw (Figure 4.8a–c). Titanium screws have been reported as having a success rate in excess of 80% [18], although this author is unable

Treatment Components and Strategy  63 

(a)

(b)

(c) Fig. 4.8  An indirect anchorage system. (a) Extra-oral view to show tipped occlusal plane due to anchorage loss during the attempted active eruption of the left maxillary canine. (b) Intra-oral view of the same case shows the exposed canine ligated with elastic ligature to the first premolar. The space is held open by a steel tube tied between the incisor and premolar brackets. The extrusive force has resulted in the lateral open bite and cant in the occlusal plane. (c) Vertical inter-maxillary bite-closing elastics (blue) are used to support the anchorage of the maxillary arch. A titanium screw TAD is tied to the mandibular canine bracket with an elastic chain to prevent unwanted reactive eruption of the lower teeth.

to reach that level of success. Thus, while they are very easily and rapidly replaced in the event of failure, their failure creates a nuisance in the smooth running of the treatment. In cases where considerable movement is needed on a fairly long-term basis, a good alternative is the use of a malleable titanium plate onlay which may be adapted to the shape of an area of bone surface, such as in the palate or the inferior surface of the zygomatic process of the maxilla [19]. Titanium screws are then used to secure the plate to the strategically selected area, and the flap sutured to leave only the extremity of the plate exposed at one end, for use as an elastic attachment device (Figure 4.9a–d). The zygomatic plate TAD appears to be much more successful in terms of its fairly long-term usefulness and experience shows that is has a much lower failure rate, although scientific data are at present unavailable.

The phenomenon of non-eruption of a tooth in one jaw is often accompanied by over-eruption of its antago­ nist in the opposing jaw, particularly in the molar region. The ostensibly successful resolution of an impacted mandibular second molar may thus be prejudiced by the tooth being prevented from reaching the occlusal plane, because of its elongated opposite number. To treat the overerupted tooth, a simple titanium screw implant may be inserted on the palatal side of the alveolus adjacent to the second molar and an elastic chain stretched from this TAD to the zygomatic plate, across the occlusal surface of the tooth. In this manner, intrusive force is applied by the chain and a rapid reduction in the height of the tooth may be achieved. This then permits the vertical elastic from the plate to the mandibular second molar to erupt the tooth to its ideal height in relation to the occlusal plane

64  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

Fig. 4.9  The zygomatic plate. (a) Panoramic view of bilateral infra-occluded first permanent mandibular molars. These teeth are almost certainly ankylosed and require to be subluxated if they may be made to erupt. (b) Initial mandibular aligning appliance. (c) The zygomatic plate affixed firmly with titanium screws to the inferior surface of the zygomatic process of the maxilla. The free end of the plate is drawn through a separate cut in the attached gingiva, while the larger flap will be fully replaced and sutured. (d) The mandibular dentition has been realigned, anterior spaces closed and space created in the molar region. The patient places the latex elastic between an attachment on the molar band and the hooked end of the zygomatic plate.

(Figure 4.10a–k), without the need to involve conventional multi-bracketed orthodontics in the eruption process.

provide the necessary light extrusive force for an impacted tooth.

Infra-occluded deciduous teeth

Magnets

Infra-occluded deciduous teeth (Figure 4.11) may be exploited in a variety of situations and may be used alone or incorporated into an appliance system, to enhance anchorage. These teeth cannot be moved orthodontically due to an ankylotic union with the alveolar bone, thus providing the opportunity for skeletal anchorage for the movement of other teeth. In much the same way as with temporary anchorage devices, a rectangular cross-section tube or bracket bonded to the buccal surface may serve as the origin for a self-supported rectangular wire spring to

Rare earth magnets were developed more than 40 years ago, but only recently has this reached the point where their reduction in size, with the introduction of the lanthanide alloys, has provided the possibility of applying suitable forces that may be exploited in the present context. Various authors have presented successful clinical results of the treatment of impacted teeth in humans [20–23] using magnetic forces. Using rare earth magnets, the forces are generated along the line of the magnetic plane and, therefore, it is possible to prescribe tooth movement in all three planes

Treatment Components and Strategy  65 

(a)

(b)

(c)

(d)

Fig. 4.10  (a) Section of panoramic view (lower part adjusted for brightness) showing second molar with enlarged follicle/dentigerous cyst impacted deeply in the mandible, despite almost complete root closure and in close relation to inferior alveolar canal. (b) Surgical exposure of crown of the second molar, following enucleation of the third molar. (c) Two bonded eyelet attachments with steel ligature pigtails. (d) Full flap closure, leaving only the twisted steel pigtails turned into hooks and easily accessible to the patient. (e) Post-surgical periapical radiograph. (f) The maxillary second molar is over-erupted (note the prominent mesial marginal ridge). An elastic chain is drawn across its occlusal surface from a palatal screw TAD to the intra-oral extremity of the zygomatic plate implant. The occlusally bonded button is to prevent slippage of the elastic chain off the occlusal surface. (g) The vertical intermaxillary elastic is placed by the patient from zygomatic plate to one of the two available steel hooks emanating through the sutured exposure site in the mandible. (h) The lower second molar has erupted and the upper has become markedly intruded (reverse mesial marginal ridge). (i) At completion, the maxillary second molar has been markedly intruded and the mandibular second molar erupted to the height of its mesial neighbour. Orthodontic treatment per se was not performed and no other orthodontic appliances were used. (j) The periapical view of the day treatment was completed, showing normal bony picture. (k) The panoramic view on the same day.

(e)

(f)

(g)

(h)

(i)

(j)

(k) Fig. 4.10  (Continued )

Treatment Components and Strategy  67 

(a)

(b)

(c)

(d)

Fig. 4.11  (a) The patient is a 12-year-old male, congenitally missing 10 of his 12 permanent molars, maxillary second premolars and mandibular central incisors. The maxillary second deciduous molars are severely infra-occluded and the right mandibular deciduous second molar is mildly infra-occluded, with clear signs of ankylosis. The bilaterally solitary permanent molars were unerupted and buried in the anterior ramus at the height of the occlusal plane. (b–d) Intra-oral views show a distinct class 3 relation and a large posterior open bite on both sides. (e) Occlusal view to show artificial acrylic teeth on a lingual arch soldered to first premolar bands, replacing the extracted deciduous lower incisors. The anchorage for the resolution of the right impacted molar was based on the infra-occluded deciduous second molar and for the left impacted molar on the temporary anchorage screw device. In the upper jaw treatment, a protraction face mask was used with elastic traction direct to attachments placed on the severely infraoccluded deciduous molars, followed by space closing mechanics using an upper multi-bracketed appliance. (f) A short piece of wire has been bonded into place between the temporary anchorage screw device and the second premolar tooth to provide anchorage for the mesial bodily traction of the unerupted molar. (g) The most recent panoramic view shows the previously unerupted molars have been drawn bodily about 8 mm on each side in a mesial direction along the occlusal plane, with an accompanying and considerable regeneration of alveolar bone. There has been marked vertical growth of the jaws during the treatment period, as witnessed by the further infra-occlusion of the deciduous second molars.

68  Orthodontic Treatment of Impacted Teeth

Infraoccluded deciduous molar Temporary anchorage screw device

Artificial teeth on soldered lingual arch (e)

(f)

(g) Fig. 4.11  (Continued )

[24–25]. In addition, these magnets corrode significantly in the intra-oral environment, and have to be carefully coated in order to render them safe. A parylene coating has been shown to seal them successfully and, when embedded in acrylic appliances, these magnets can be isolated from the intra-oral environment and protected from heavy forces [25]. There are, however, a number of significant problems with their use. Attracting forces that exist between the two magnets are in inverse proportion to the square of the distance between them. This means that when used to move displaced or ectopically positioned teeth, the magnet that is sited on the appliance must be placed close to the magnet which has been bonded to the displaced tooth, otherwise the force between them will be too low. In addition, if the magnets are not sited ideally on top of each other, there is a dramatic drop in force level [26]. The notion that traction may be applied without the need to trail a wire through the soft tissues of the palate appeals to authors. They speculate that this may improve the final periodontal condition of the teeth, since ‘eruption simulates a normal eruption process’. However, it should be remembered that: the tooth • surgically;

must nevertheless initially be exposed

Fig. 4.12  The bonded magnet ‘backpack’. (Courtesy of Professor A. Vardimon.)

magnet must be bonded to it; • the the must be partially or fully replaced and healing • mustflapoccur; the tooth must then pass through the tissues with this • relatively large magnetic ‘backpack’ (Figure 4.12);

Treatment Components and Strategy  69  each of which presents obstacles that signify a departure from any similarity with normal eruption. Even if the idea is ‘attractive’ [27], the use of magnets for impacted teeth is still in its early developmental stages and the methods that have been described show a number of technological disadvantages. The size of the magnets and the inverse square rule of their force of attraction are the most pertinent. Presently, it remains a method that cannot unequivocally replace the more traditional and conventional methods described above [28–31].

References   1.  Olive RJ. Factors influencing the non-surgical eruption of palatally impacted canines. Aust Orthod J 2005; 21: 95–101.   2.  Iramaneerat S, Cunningham SJ, Horrocks EN. The effect of two alternative methods of canine exposure upon subsequent duration of orthodontic treatment. Int J Paediatr Dent 1998; 8: 123–129.   3.  Becker A. Alternative methods of canine exposure and subsequent duration of treatment. Int J Paediatr Dent 1998; 8: 298–299 [letter to the editor].   4.  Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003; 124: 509–514.   5.  Kokich VG, Mathews DP. Surgical and orthodontic management of impacted teeth. Dent Clin North Am 1993; 37: 181–214.   6.  Shapira Y, Kuftinec MM. Treatment of impacted cuspids: the hazard lasso. Angle Orthod 1981; 51: 203–207.   7.  Kettle MA. Treatment of the unerupted maxillary canine. Dent Pract Dent Rec 1958; 8: 245–255.   8.  Becker A, Zilberman Y. The palatally impacted canine: a new approach to its treatment. Am J Orthod 1978; 74: 422–429.   9.  Kokich VG. Surgical and orthodontic management of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2004; 126: 278–283. 10.  Gensior AM, Strauss RE. The direct bonding technique applied to the management of the maxillary impacted canine. J Am Dent Assoc 1974; 89: 1332–1337. 11.  Nielsen LI, Prydso U, Winkler T. Direct bonding on impacted teeth. Am J Orthod 1975; 68: 666–670. 12.  Hunt NP. Direct traction applied to unerupted teeth using the acidetch technique. Br J Orthod 1977; 4: 211–212. 13.  Becker A, Shpack N, Shteyer A. Attachment bonding to impacted teeth at the time of surgical exposure. Eur J Orthod 1996; 18: 457–463.

14.  Ziegler TF. A modified technique for ligating impacted canines. Am J Orthod Dentofacial Orthop 1977; 72: 665–670. 15.  Lu TC, Wang WN, Tarng TH, Chen JW. Force decay of elastomeric chains – a serial study. Part 2. Am J Orthod Dentofacial Orthop 1993; 104: 373–377. 16.  Storie DJ, Regennitter F, von Fraunhofer JA. Characteristics of a fluoride-releasing elastomeric chain. Angle Orthod 1994; 64: 199–210. 17.  Vachiramon A, Urata M, Kyung HM, Yamashita DD, Yen SL. Clinical applications of orthodontic microimplant anchorage in craniofacial patients. Cleft Palate Craniofac J. 2009; 46: 136–146. 18.  Kuroda S, Sugawara Y, Kuroda S, Sugawara Y, Kyung H-M, TakanoYamamoto T. Clinical use of miniscrew implants as orthodontic anchorage: success rates and postoperative discomfort. American Journal of Orthodontics and Dentofacial Orthopaedics 2007; 131: 9–15. 19.  Erverdi N, Usumez S, Solak A. New generation open-bite treatment with zygomatic anchorage. Angle Orthod. 2006 May; 76(3): 519–526. 20.  Vardimon AD, Graber TM, Voss LR. Hygienic magnetic technique to align impacted teeth. Presented at the 87th annual session of the American Association of Orthodontists, Montreal, Canada, 1987. 21.  Sandler PJ, Meghji S, Murray AM et al. Magnets and orthodontics. Br J Orthod 1989; 16: 243–249. 22.  Darendeliler MA, Friedli JM. Treatment of an impacted canine with magnets. J Clin Orthod 1994; 28: 639–643. 23.  Vardimon AD, Graber TM, Drescher D, Bourauel C. Rare earth magnets and impaction. Am J Orthod Dentofacial Orthop 1991; 100: 494–512. 24.  Mancini GP, Noar JH, Evans RD. Neodymium iron boron magnets for tooth extrusion. Eur J Orthod 1999; 21: 541–550. 25.  Noar JH, Wahab A, Evans RD, Wojcik AG. The durability of parylene coatings on neodymium iron boron magnets. Eur J Orthod 1999; 21: 685–693. 26.  Noar JH, Shell N, Hunt NP. The performance of bonded magnets used in the treatment of anterior open bite. Am J Orthod Dentofacial Orthop 1996; 109: 549–557. 27.  Sandler JP. An attractive solution to unerupted teeth. Am J Orthod Dentofacial Orthop 1991; 100: 489–493. 28.  Ingervall B. The use of magnets in orthodontic therapy: panel discussion. Eur J Orthod 1993; 15: 421–424. 29.  Gianelly A. The use of magnets in orthodontic therapy: panel discussion. Eur J Orthod 1993; 15: 421–424. 30.  Rygh P. The use of magnets in orthodontic therapy: panel discussion. Eur J Orthod 1993; 15: 421–4. 31.  Vardimon AD. The use of magnets in orthodontic therapy: panel discussion. Eur J Orthod 1993; 15: 421–424.

5 Maxillary Central Incisors

Aetiology

71

Diagnosis

80

Treatment timing

83

Attitudes to treatment

86

Treatment of impacted central incisors

86

Prognosis

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

102

Maxillary Central Incisors  71 

Aetiology At the age of about 6 years, in most children, a sudden and dramatic change occurs in the anterior part of the dentition, with the shedding of the deciduous incisor teeth and the appearance of the permanent incisor teeth. As has been described in Chapter 1, the first to erupt in the young child are usually the mandibular central incisors, although the first permanent molars may sometimes precede them. The mandibular lateral and the maxillary central incisors then erupt shortly after, at 6.5–7 years. Under normal circumstances, the maxillary lateral incisors are the last of the incisors to erupt, completing the anterior dentition with their appearance about a year after the eruption of the adjacent central incisors. Further changes in the dentition, in terms of shedding of deciduous teeth and eruption of their permanent successors, do not occur until approximately the age of 9.5–10 years. This means that there is a two-year period of relative stability, which is known as the mixed dentition stage.

(a)

The spectacle of erupted lateral incisors associated with the non-appearance of one or both of the central incisors should always be deemed abnormal, whether or not a deciduous central incisor is still present, and further investigation should be undertaken to ascertain the reason for the aberration. Congenital absence of a maxillary permanent central incisor, given the presence of permanent lateral incisors, is exceptionally rare, although it has been reported. In this situation, the shape of the single central incisor makes it impossible to distinguish whether it belongs to the right or left side. The patient’s appearance is abnormal (Figure 5.1a–c) and rather reminiscent of a ‘dental cyclops’! How­ ever, the abnormality in the appearance is also due to other clinical features and malformation of other elements of the craniofacial complex. The patients have other midline anomalies, including an indistinct philtrum of the upper lip, with an absence of the typical Cupid’s bow and no midline frenulum, a mid-palatal ridge, and nasal obstruction or septum deviation. They exhibit a short anterior

(b)

(c) Fig. 5.1  (a) Abnormal lip morphology, absence of philtrum and midline position of single central incisor, in a case of holoprosencephaly. (b) Intra-oral view of same patient to show ‘square’ anatomy of incisor and indeterminate right/left designation. The lateral incisors are laterally flared as part of an otherwise normal ‘ugly duckling’ stage of development. (c) A view of the palate to show bilateral submucous clefting. (Courtesy of Dr S. Geron.)

72  Orthodontic Treatment of Impacted Teeth cranial base and maxilla, together with retrognathic and posteriorly inclined maxilla and mandible. The sella turcica also has an abnormal shape. Accordingly, the condition should not be treated as a simple, local and isolated congenital absence, as would be the case in relation to a missing maxillary lateral incisor or mandibular second premolar. This patient exhibits a mild form of holoprosencephaly (Figure 5.1). At 5–6 weeks of human embryonic development, the forebrain is formed and the face begins to take shape. In holoprosencephaly, the forebrain fails to develop into two cerebral hemispheres and the structures that are normally paired into identical right and left units are allowed to merge. This causes defects in the development of the face and in brain structure and function which, in less severe cases, may result in normal or near-normal brain development and facial deformities that may affect the eyes, nose and upper lip. However, in most cases of holoprosencephaly, the malformations are so severe that the foetus dies in utero [1]. Trauma to the anterior maxilla in a young patient is probably an almost daily occurrence in many schools, playgrounds and sports activities. Trauma at home should not be forgotten and may occasionally be the first clue of child abuse. By and large, the incidents are trivial and charac­ terized by much bleeding from lacerations of the lip and gingivae which may occasionally divert attention from underlying damage to the incisor teeth. These may have been traumatically intruded and lost from sight or even completely avulsed. A careful history should be elicited to eliminate the remote possibility of avulsion of the permanent central incisor which may have been completely overlooked. This may happen if the tooth had been in the very earliest stages of its eruption and, therefore, its absence went unnoticed at the time. A newly erupting central incisor is invested with a rudimentary, underdeveloped periodontal ligament (PDL) such that a relatively light and unfortunately welldirected blow may easily bring about its loss.

patients suffer from impacted central incisor teeth from this cause. For the most part, supernumerary teeth develop on the palatal side of the permanent incisors and as such occupy space within the narrow alveolar ridge. This results in a labial and superior displacement of the permanent incisors, which includes their roots. Odontome

Among the other and rarer causes of obstruction, which may equally prevent the eruption of a normal central incisor, are odontomes. These are very variable in size and type, but, whether they are of the complex or the composite type, they usually have a broader and wider cross-section and their presence will be more likely to impede the eruption of an incisor than a supernumerary tooth. Ectopic position of the tooth bud

The development of a tooth bud in an abnormal position or in an abnormal angulation may have no apparent cause and may thus be attributed to traumatic or genetic factors (Figure 5.2). As a result of the displacement, normally placed adjacent teeth may provide the physical obstacle to the normal eruption of such a tooth. Alternatively, other physical obstacles, such as the above-mentioned supernumerary teeth or odontomes, may be the more likely reason for a secondary displacement of this tooth. While the early removal of this obvious aetiological factor may be strongly indicated, this will not necessarily affect the position of the tooth bud, which will probably continue to develop in its existing location. Variation in the position of a developing tooth will produce a concomitant variation in its eruption path. When the eruption path is very slightly deflected, the tooth will usually erupt, but with an abnormal angulation of its long axis, indicating the path along which it will have travelled. As its vertical development proceeds, its relationship to the deciduous predecessor is more lateral, medial, palatal or

Obstructive causes Supernumerary teeth

When an existing permanent central incisor does not erupt and the diagnosis of impaction is made, the most common aetiological factor is the presence of one or more midline supernumerary teeth [2–4] (see Figures 1.10 and 1.11). In a study of a sample of schoolchildren [5] the prevalence of supernumerary teeth was found to be between 1.5% and 3.5%. It has also been shown in a different sample group [6] that between 28% and 60% of cases with supernumerary teeth will have resultant eruption disturbances of the adjacent teeth. By arbitrarily integrating these two studies and assuming that they represented random samples of patients attending a children’s hospital dental department, it would seem that between 0.42% and 2.1% of child dental

Fig. 5.2  An abnormally sited central incisor, whose root apex is close to the canine area. The shape of the root also appears to be abnormal.

Maxillary Central Incisors  73  labial to it. This will bring about a partial and oblique resorption along one side of the root of the deciduous incisor. In due time, the further progress of the permanent incisor and the oblique resorption pattern bring it into contact with the crown of the deciduous tooth on that side. The permanent tooth may remain impacted if insufficient space exists. Alternatively, the tooth may finally erupt adjacent to the over-retained deciduous tooth and many months later than expected, possibly into a cross-bite relationship, or it may be proclined labially, or a diastema may be produced in the midline. This situation may not be selfcorrecting after the belated shedding or extraction of the stubborn deciduous tooth. Should the position of the developing tooth be more markedly displaced, which is unusual, its potential eruption path will be in a more obtuse direction and little or no resorption of the deciduous tooth will occur. In these circumstances, eruptive movements are minimal and the permanent tooth remains in a more or less unchanged position over a long period. Finally, when positive intervention is undertaken, removal of the cause will need to be supplemented with active appliance therapy for its resolution. Traumatic causes

Fig. 5.3  The tangential view shows severe labial displacement of the root of the deciduous incisor. (Courtesy of Professor J. Lustmann.)

Obstruction due to soft tissue repair

The traumatic, sudden and very early loss of the deciduous incisor teeth is most often the result of an accident that delivered a blow to dislodge the tooth, usually while the child was at play. The possibility also exists for this to have been caused by a dental extraction, prompted by the presence of deep caries or following the sequelae of an earlier trauma. This typically happens at the age of 3 or 4 years, at a time when the permanent incisor is not ready to erupt and a healing-over of the macerated gingival tissue occurs without the early eruption of the tooth. In time, changes take place in the connective tissue overlying the developing permanent incisor, which prevent the tooth from penetrating the mucosa [7, 8]. By the age of 7 or 8 years, one may see and be able to palpate the bulging profile of the central incisor (see Figure 3.2a). Dilaceration

In the early stages of their development, high in the anterior part of the maxilla, the permanent central incisors are situated lingual and superior to the apices of the deciduous incisors. Their positions change as the result of their labially and inferiorly directed migration, which is part of their normal further development and, as they do so, an oblique resorption of the roots of their deciduous predecessors is initiated. During this critical period, children are frequently involved in traumatic episodes of various degrees of intensity and a blow may be inflicted on the deciduous maxillary incisors from the front. A blow of sufficient magnitude will produce a lingual avulsion of the crowns of the incisors and

a concomitant labial displacement of the roots, which will sometimes cause a fracture of the labial plate (Figure 5.3). In this situation, the roots of the teeth and the sharp edge of bone will be palpable in the labial sulcus, although the overlying mucosa will usually remain intact. Since the unerupted permanent incisors are superiorly and lingually placed in relation to the resorbing root ends of the deciduous incisors, the successional teeth will usually not be displaced and will often continue unhindered in their normal developmental path. The roots of incisor teeth are tapered apically, which means that a blow directed along their long axis from below will drive the tooth upwards into a similarly tapered socket. It follows that the alveolar process fracture that may occur will cause a part of the labial plate of bone to become displaced labially and the teeth to be displaced superiorly (intruded). Under these circumstances, trauma to the anterior part of the deciduous dentition may cause damage to the growing tooth buds of the permanent dentition, and this may alter the further development of the permanent teeth in many ways. The anomalies that may occur vary from a discoloured hypoplastic mark on the enamel, through anatomic malformations of the crown or root, to non-proliferation of the root, to pulp death and sequestration of the tooth bud [8]. The alterations in the form of the crown and the root of these teeth are collectively referred to as dilacerations. These are the result of recovery from the blow that will have disturbed the natural development, resulting in a variable combination of a hypocalcified,

74  Orthodontic Treatment of Impacted Teeth

Fig. 5.4  An extracted dilacerated incisor. Reprinted from ref. [37], with permission.

altered, attenuated and directionally reoriented form of the crown and/or root. The final shape and appearance of the injured tooth will be dictated by the direction and force of the blow and by the particular stage of development of the unerupted permanent tooth. Each these anomalies will be unique in its form and no two trauma incidents will produce the same result. In direct contrast, there is one type of dilaceration, which we shall refer to here as the ‘classic’ dilaceration, which consistently reproduces an almost identically shaped tooth (Figure 5.4), whose unerupted location is always the same. Its causation has, over the past six or more decades, been the subject of much discussion among paediatric dentists and orthodontists. When the trauma is directed in the long axis of the deciduous tooth, it may be transmitted superiorly to the developing permanent tooth. According to this hypothesis, the force delivered by the violent blow to the deciduous incisor is transmitted to the resorbing root apex, which momentarily establishes a point of impact with the palatal side of the crown of the permanent incisor. This has been believed to cause the partially developed and unerupted permanent incisor tooth an immediate upward and labial rotation, in its crypt. It is then assumed that any further root development that occurs in the post-trauma period will continue in the same direction as before, producing a bizarre angle between the pre- and post-trauma portions of the tooth – the ‘classic’ dilacerated central incisor – with labial displacement of the crown portion. The site of this junction will depend on the stage of development of the root at the time of trauma, and with it the prognosis of any proposed orthodontic treatment for the tooth. This reconstructed scenario for the causation of this classic form of dilaceration is extremely well known and probably represents a majority opinion, if not consensus, within the profession. Palatal, rather than labial, displacement of the crown vis-à-vis the post-traumatic root portion may occur in rare instances as a variation of the above theme and is due to a more palatal position of the tip of the developing permanent incisor and the apex of the deciduous incisor root, at

impact. This is a more likely variation in the very young, during the early calcification of the tooth crown when its palatal location is normal (Figure 5.5). In an attempt to determine whether there was an evidence base for accepting the above hypothesis, a protocol was instituted some years ago in the emergency clinic of the Department of Paediatric Dentistry at the Hebrew University–Hadassah School of Dental Medicine, Jerusalem. Children who attended the clinic having suffered trauma to their anterior deciduous teeth were subjected to routine clinical and radiographic examination, vitality testing and emergency pulpal and restorative treatments, as indicated. Until the new protocol was established, the radiographic examination had generally been limited to a periapical film of the area. It is obvious that this radiographic view is not suitable for showing any labial and superior displacement of the crown of the unerupted permanent central incisor within the crypt. Accordingly, the new protocol included a tangential radiographic view of the anterior maxilla, which has been described in Chapter 2 as being a view taken from the side, across the occlusal plane, and identical to a restricted area of a lateral cephalometric radiograph. It is obtained on a small, occlusal-sized film by holding the film vertically against the cheek and parallel to the mid-sagittal plane of the skull. Any alteration in the labio-lingual and vertical orientation of the crown of an incisor will be immediately discernible on this film. The protocol was run for several years and did not discover a single case where the crown of the tooth had been displaced in the immediate post-trauma period in this way. However, in the succeeding years among the small but significant number of patients who turned up in the Department of Orthodontics with a fully developed, classic, dilacerated central incisor, several had been seen in the emergency clinic of the Department of Paediatric Dentistry following trauma in their earlier years. Since records existed from that time, the radiographs that had been taken when the protocol was in force were re-examined with specific regard to these patients. No displacement of the crowns of the unerupted permanent central incisors could be discerned on the immediate post-trauma films, effectively discrediting immediate tooth germ displacement as a cogent explanation for the aetiology of the phenomenon. A developmental origin has been suggested as an alternative cause for the classic dilacerations [9], with the contention that the active process of the development of cysts, odontomes or supernumerary teeth may produce this phenomenon by displacement of the crown of the tooth or by interference and redirection of its root. In a retrospective study of the phenomenon [10] no history of trauma could be elicited in 70% of the patients in the sample, nor was there macroscopic or microsopic evidence of trauma, or the existence of a cyst, odontome or extra tooth in these patients. No case was found with both central incisors affected and there had been no damage to neighbouring

Maxillary Central Incisors  75 

(b) (a)

(c)

(d)

Fig. 5.5  A palatally-oriented dilaceration of the central incisor. (a) Anterior section of the panoramic film to show the impacted dilacerate left central incisor with its labial surface facing inferiorly. The unerupted permanent left canine, which is transposed with the mesially-tipped lateral incisor, is seen to be directly above it. The deciduous canine with an intact root is seen distal to the lateral incisor. From this view, it is impossible to tell whether the crown of the central incisor points labially or palatally. (b) The lateral cephalometric view shows the outline of a screw post in the restored right central incisor. Above it, the profile of the palatally directed crown of the central incisor can be clearly seen, with its root portion curving labially and superiorly in a tight quarter-circle, encompassing the more superiorly placed and labially directed permanent canine. (c) The anterior occlusal view shows the typical form of the canine superimposed and largely masking the crown of the incisor. The apical portion of the incisor root is viewed in its cross-section anterior to the tip of the canine crown. (d) The periapical view provides a separation of the two teeth although, taken in isolation, it may give the inexperienced diagnostician the misleading impression that the crown of the incisor is labial.

teeth, which could be expected to occur in at least a few instances had trauma been the cause. These cases also failed to show two distinct and angulated portions to the root, but rather a continuous and tight curve (Figure 5.4), quite different from those in which trauma, as an aetiological factor, had resulted in any of the other forms of dilaceration. The conclusion of the study was that a fairly high proportion of dilacerations occur due to an ectopic siting of the tooth germ, whose root development is deformed by its proximity to and the anatomy of the palatal vault in the immediate vicinity.

These explanations are unsatisfactory on several counts. Different cases show an almost identical and very typical anatomy of the tooth, which affects maxillary central incisors exclusively – no case of bilateral occurrence or parallel incidence in lateral incisors has been reported in the literature. As if to illustrate the exception that proves the rule, the records of a single case of bilateral occurrence were sent to the author (Figure 5.6) a few years ago and it remains the sole case that the author has seen. The morphology of the crown of the affected tooth is normal and is an exact mirror-image of its erupted antimere and the coronal

76  Orthodontic Treatment of Impacted Teeth

(a)

Root apices palpable here (b)

(d)

(c) Fig. 5.6  An extreme rarity: bilateral classic dilacerations of the central incisors. (Courtesy of Dr. Srdan Marelic.) (a) Mesial drifting of the erupted lateral incisors has largely closed off the space for the unerupted central incisors. The intra-oral anterior view of the dentition. (b) The intra-oral occlusal view. (c) The cephalogram. (d) Panoramic view.

portion of the root shows initial normal development. The remainder of the root develops strictly in the labio-lingual plane along a tight and continuous circular path, rather than two straight portions of root at an angle to one another. The crown is grossly displaced in the bucco-lingual and vertical planes, while exhibiting minimal or no mesiodistal rotation. Not only is the anatomy typical, but the position and orientation of the tooth are also unique. The crown of the tooth is upturned and displaced high in the sulcus on the labial side of the alveolus, with its palatal aspect palpable on the labial side of the sulcus close to the root of the nose. Often, the root apex of the tooth is palpable on the palatal side of the alveolus (Figure 5.5) and may be the sign that

influences an unwary surgeon to mistakenly approach exposure of the tooth on the wrong side (see Figure 12.12). It has been suggested that the loss of a deciduous incisor may lead to scarring along the eruption path of the permanent incisor, which deflects the developing tooth labially [8]. This runs counter to Stewart’s observation that no history of early traumatic loss of the deciduous tooth had occurred in 70% of the cases in his series. The Jerusalem hypothesis It is possible to read a completely different aetiological interpretation into these very constantly occurring features, and it is pertinent to begin by questioning the reliability of a child’s or parent’s memory regarding traumatic injury of

Maxillary Central Incisors

77

Image not available in the electronic edition Image not available in the electronic edition

Fig. 5.7 A diagram to show how a vertically directed force through the deciduous incisor is transmitted to the labial aspect of the mineralizing root of the unerupted permanent incisor. Reproduced from previous edition with the kind permission of Informa Healthcare – Books.

the front teeth. Severe trauma is rare and always remembered, but non-disfiguring trauma (i.e. trauma that causes no loss, fracture or displacement of the deciduous anterior teeth) occurs quite frequently in young children, is rarely noted and almost never remembered in later years. Indeed, following a relatively minor blow, the child may have come home in tears, but the incident will often have been forgotten the next day, at most with some minor, residual, temporary soreness or tenderness. Abrupt and vertically directed force through the long axis of the deciduous tooth will bring about the transference of the impact to the intimately related, unerupted, permanent central incisor. Because the long axis of the permanent incisor has a more labially tipped orientation, the force will be transmitted in an oblique line which runs through the incisal edge and the most superior point on the labial side of the newly forming root, close to or at the rootmineralization interface (Figure 5.7). This most recently formed extremity of the partially developed root has a circular knife edge of calcified dentine. Thus, the intrusive blow will be delivered directly to the sensitive cells of Hertwig’s root sheath at this narrow rim. The intrusive force is thus concentrated along the knife edge root extremity and will inflict considerable damage on cells of the formative root sheath, with relatively low force values. It will be appreciated that precision in direction may be more critical than force magnitude. It is entirely possible that the root sheath may only partly recover from the blow, which may result in an attenuated rate of production of dentine on the labial side of the tooth. With the remainder of the root-forming system continuing to produce dentine unscathed, undeterred and unabated, it follows that the final shape of the root of this tooth will conform to a continuous labially directed curve (Figure

Fig. 5.8 A diagrammatic illustration of the progressive alteration in the orientation of a dilacerated incisor, during the disturbed root formation. Note that the position of Hertwig’s proliferating root sheath remains unaltered. Reproduced from previous edition with the kind permission of Informa Healthcare – Books.

5.8), until apexification is achieved. Furthermore, since the dental papilla base of Hertwig’s root sheath maintains its position within the alveolar process fairly constantly – against the eruptive force of the developing tooth – and provides the platform from which the downward development of the root is normally directed, the crown of the incisor moves labially and superiorly for as long as this bucco-lingually unequal mineralization gradient of the developing root continues. In other words, dilaceration of this classic type is an anomaly which is traumatic in origin but developmental in its expression. This hypothesis provides an explanation for the typical appearance of the dilacerated tooth, as well as its final unerupted position under the nose. Furthermore, since it may occur with a relatively minor trauma, this could account for the high proportion of cases with no apparent history of trauma experience and no premature loss of or damage to the adjacent teeth. Its relative rarity may be due to the positional relationship between the deciduous and permanent incisor at the time of injury and a very specific directional relationship with the traumatic force vector. This may account for an absence of bilaterally affected cases, for its non-occurrence among lateral incisors and for an absence of any association with supernumerary teeth, cysts and odontomes. It also provides an explanation as to why there is no obvious displacement visible on the tangential radiographs that were taken immediately following the traumatic episode (Figure 5.9) and why the tooth is never rotated in the horizontal plane.

78  Orthodontic Treatment of Impacted Teeth

(a)

(c)

(b)

(d)

Fig. 5.9  Dynamic development of a ‘classic’ dilaceration. (a) A periapical view of the maxillary incisor area of a 3.11-year-old child taken in the emergency room on the day that trauma had occurred. Note there is no apparent displacement of either central incisor. The left side appears to be the worst affected by the trauma. (b) A six-month follow-up film shows considerable inflammatory resorption of the root of the left deciduous central incisor and less on the right side, but there is a concomitant subtle change in the relative positions of the unerupted permanent incisors. On the right side, the incisal edge is more superiorly located in relation to the left incisor and to the root of its deciduous predecessor. (c) The initial diagnosis of dilaceration of the right central incisor was made on the basis of this panoramic view, taken at age 7.6 years (i.e. 3.7 years post-trauma). Note the anatomical labial surface of the crown faces superiorly, with the orientation of the crown portion being slightly above the horizontal. The pulp chamber is very large, indicating that root development is continuing. (d) A new panoramic view taken 2.4 years later shows the tooth to be higher still, to one side of the anteriorly nasal spine and tipped further posteriorly. Its palatal surface is now facing anteriorly and its pulp chamber is much smaller.

Arrested root development When a pre-school child suffers a very severe blow to the maxillary anterior dentition, it is likely to result in the loss of the deciduous incisors, but it may also cause fracture of one or both jaws. The root-producing ring of cells that comprises Hertwig’s sheath may have been so seriously damaged as to have effectively caused serious disruption or actual cessation of any further root development. These teeth may lose their eruption potential, while the adjacent teeth will continue to erupt, bringing with them vertical proliferation of alveolar bone. Only at a much later stage will this phenomenon be discovered when the affected tooth or teeth do not erupt and an area of vertically deficient and bucco-palatally narrow, edentulous alveolar ridge becomes evident.

Radiographs will usually reveal a normal axial inclination and an undisturbed sagittal and lateral location of the crown of the tooth. In the vertical plane, it will be situated very high up in the premaxilla, with minimal or no root formation, depending on how much root had already developed at the time of the accident (Figure 5.10). Acute traumatic intrusion (intrusive luxation) Traumatic injury occurs in young children as the result of play-related activities in school or at home, in accidents involving a fall or, occasionally, as the result of deliberate physical violence [8]. The effects on the teeth range from a transitory pulp inflammation, through the various types of fracture of the crown of the tooth or of its root, to, in the severest cases, avulsion of the entire tooth. Intrusion of one

Maxillary Central Incisors  79 

#21 #22

#21 #22

(a)

(b)

#21

#21 # 22 # 62

(c)

(d)

Fig. 5.10  Arrested root development due to severe trauma at age 3 years. Records taken at age 7.4 years. (a) A periapical view of the unerupted, but normally oriented, left central incisor (#21) shows a marked height discrepancy compared to the erupting right incisor. Note the late developing lateral incisor (#22) is inferiorly placed, tipping mesially and more advanced in terms of its eruption status. The affected incisor shows little or no root development. (b, c) The panoramic and cephalometric views show the incisor to be close to the floor of the nose and a normal crown orientation. (d) The anterior view seen in this three-dimensional image from the cone beam computerized tomography (CT) scan. (e, f) Two paraxial (vertical) cuts from the CT scan illustrate the vertical relationship between the unerupted central and lateral incisors and the deciduous lateral incisor (#62). They also show the labial cervical area of the crown coming to an abrupt step where cessation of crown formation occurred and where the minimal root development is almost at a right-angle to the general orientation of the crown and in close relation with the floor of the nose.

80  Orthodontic Treatment of Impacted Teeth

#21 #21

#22 #22

#62

#62

(e)

(f)

Fig. 5.10  (Continued )

or more of the incisor teeth is often associated with a fracture or comminution of the labial plate of bone and a tearing of the periodontal fibres. A child may present at the emergency clinic with what gives the appearance of a total avulsion, since the tooth is not visible in its former place, the gingivae are lacerated and there is a considerable amount of blood clot. A periapical radiograph of the area will reveal a superior displacement of the tooth into the alveolar bone, without necessarily producing a fracture of either the crown or the root. The labial plate is displaced labially, although it is most often held closed by the injured but uninterrupted band of labial gingiva and oral mucosa. The integrity of the blood supply to the soft tissues is usually intact, and this allows good and rapid soft tissue healing. In a sense this tooth has been totally avulsed, but in an atypical manner. It is completely displaced from its socket, with total severance of its attachment apparatus and disruption of its vital supply lines. When compared with the typical avulsed case, however, it has one enormous advantage, and that is that the tooth has not been allowed to dry; it has not usually been in contact with any form of contaminated material and it is not necessary to store it in saliva or milk or other recommended isotonic medium, before restoring it to its rightful place. It is situated in an area initially surrounded by a coagulating haematoma and later by organizing blood clot, and it must be assumed that the damaged periodontal fibres in this situation fare considerably better than do those of the replanted tooth, which

has spent some time out of the mouth. This is dealt with in detail in Chapter 13.

Diagnosis History A missing permanent central incisor is likely to be the presenting symptom of a child when the contralateral central incisor has been present in the mouth for several months. Urgency on the part of the parent may be sharpened when the lateral incisor of the same side erupts and clearly reduces the size of the place for the absent tooth. Ideally, many children will have been seen by the paediatric dentist for routine dental checks in the past and will have been referred by the dentist for the orthodontic opinion, but many others may be self-referred directly to the orthodontist. With the notable exception of the acute traumatic impaction cases referred to above, urgency does not exist in the present context in contrast to most other forms of presenting symptom, such as pain and swelling. When seeing a patient who attends for the first time exhibiting absence of an erupted permanent central incisor, the general medical history should be recorded carefully. It must be borne in mind that surgical intervention is very likely to be needed as an essential part of the treatment that is to be provided. Accordingly, such aspects as previous illnesses, particularly rheumatic heart disease, drugs being taken and bleeding tendencies, together with any other

Maxillary Central Incisors  81 

(a)

(b)

(c)

(d)

Fig. 5.11  (a–c) Clinical views of a patient with a bulging ridge form due to obstructive impaction of the central incisors. Three deciduous incisors are overretained and the permanent lateral incisors are erupting rotated and with a mesio-labial angulation. The ridge bulges due to the presence of dental obstruction. (d) Periapical views of the anterior region show displaced long axis orientation of the central incisors and the existence of several supernumerary teeth.

important and relevant items of information, require to be elicited at the outset. Questions should be asked, with particular emphasis placed on the possibility of an episode of past trauma. The parent should be questioned carefully to discover whether the child is generally accident-prone. Direct mention of bicycle accidents, falling from a chair, ladder or tree, or being hit in the mouth during play should be made and all relevant answers should be carefully recorded, together with the approximate dates of their occurrence. The possibility of well-hidden child abuse should be considered and, when there is suspicion of this, a report should be made to the local police. Clinical examination Much of the patient’s dental experience and history is possible to ascertain from a glance at the dentition itself. The existence of sealants and restorations, the absence of teeth, gingival inflammation and the level of oral hygiene will often tell a great deal about past attitudes of both the patient and the attending dentist to prevention and to restorative procedures. At the time the patient attends for treatment, the presence or absence of the deciduous incisor is generally

irrelevant. The central incisor of the opposite side and the lateral incisor of the same side will usually be seen to be tipped towards one another, and there will usually be insufficient space at the occlusal level for the placement of the unerupted tooth. Widely apically divergent long axes of the two adjacent teeth will suggest the presence of an unseen and undiagnosed space-occupying physical obstruction. Palpation In the obstructed cases, the unerupted tooth itself is often high on the labial side of the alveolar ridge and there may be additional and smaller irregularities bulging the alveolus more inferiorly. These are best identified by palpation. There will almost always be a labio-lingual widening of the ridge (Figure 5.11). If the ridge area is relatively thin inferiorly, it will indicate that teeth are not present at this level (Figure 5.12). The importance of palpation of the area is not to be underestimated since, if it is not performed sufficiently thoroughly, an important diagnosis may be missed. The presence of a dilacerated central incisor will only be revealed by clinical examination if palpation is made very high in the labial sulcus. Normally, the superior midline area is

82  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 5.12  (a, b) Frontal and occlusal clinical views of a patient with a dilacerate central incisor, illustrating a bucco-lingually and vertically deficient ridge, due to the absence of teeth in the immediate area – the ‘hourglass’ ridge.

delineated by the prominence of the anterior nasal spine, on each side of which a shallow depression will be felt. The palatal surface of a dilacerated incisor crown faces forwards and produces a hard swelling in the place where the shallow depression is expected. By superiorly retracting the upper lip, the oral mucosa may be seen to move freely over the stretched area, which will emphasize the outline of the cingulum of the tooth. Palpation of a dilacerated central incisor may often be made in two places. With the abnormal position of the coronal portion of the tooth, the further development of the root portion may be along an axis which is tipped more lingually and, in the later stages of root closure, the apex may become palpable as a small, hard lump in the palate. This is a feature which few clinicians seem to look for and is a more consistent finding than may be realized [11]. Mistaken diagnosis of crown location is an unusual event since both the orthodontist and the oral surgeon need to undertake a clinical examination and review the radiographs before treatment and it is difficult to imagine that the same mistake could be made twice. Notwithstanding, as we shall see in Chapter 12, such occurrences are seen from time to time (Figure 12.12). Radiographic examination In Chapter 2, the different methods of radiographically viewing unerupted teeth were discussed in general and it was pointed out that a periapical view provides essential qualitative information and as such, should be the first step in this part of the examination. In the case of an unerupted central incisor, this view will generally show associated pathology with great clarity, including hard tissue obstructions (supernumerary teeth of the carious types, odontomes), soft tissue lesions (cysts, tumours), and abnormal root and crown morphology of the unerupted tooth. From this alone, it will usually be possible to establish the reason for the failure of the tooth to erupt.

If supernumerary teeth or odontomes are seen on the film, the information that will then be required relates to their size, number and mesio-distal relationship to the midline and the incisor teeth, all of which will be obvious from this view. However, their labio-lingual orientation in relation to the adjacent erupted teeth will not be obvious from this one film. Since the periapical view is obliquely angled to the horizontal plane, a labial supernumerary tooth will appear lower in the vertical plane than a palatal supernumerary which is situated at the same height. Accordingly, the assessment of height is directly related to the labio-lingual position of the tooth, and this provides the basis for the vertical tube shift method of locating the bucco-lingual relationship of an impacted tooth to an erupted tooth, described in Chapter 2. For patients in whom the aetiology is the presence of unerupted supernumerary teeth and at the age at which most patients will attend for treatment, a true lateral, tangential view is not helpful, due to the superimposition of central and lateral incisors, deciduous and unerupted permanent canines, and the supernumerary teeth. A second periapical view, directed from a more distal vantage point, will usually help to localize the relative position of the unerupted teeth, using the principles of parallax. Similarly, a routine anterior (oblique) occlusal film will help to separate out the images of the unerupted teeth, using the same parallax principles, this time in the vertical plane. This will provide the information needed to compute the rela­ tive heights and labio-lingual relations of the individual structures. A good vertex occlusal film, directed through the long axes of the anterior teeth, will provide unequivocal evidence of labio-lingual tooth position, particularly if there is marked displacement. However, the relative lack of contrast in this view and the long exposure needed weigh heavily against its risk/benefit efficacy and have contributed to obsolescence of the method and to its demise.

Maxillary Central Incisors  83  Dilacerated central incisor teeth with labial displacement have a very special and characteristic appearance on a periapical radiograph. We have already described how the crown and the developed part of the root become rotated labially and superiorly following the trauma to the deciduous incisor. The long axis of the coronal part lies in the direct line of the X-ray beam, which is pointed at a periapical film of the area and, accordingly, will show up as a cross-sectional view of the crown, superimposed on and concentric with a cross-sectional view of the widest part of the root. It will be readily understood, therefore, that the labial surface will be seen to face superiorly and the cingulum will be clearly outlined inferiorly (Figure 5.9c, d). The apical (post-trauma) portion of the root, on the other hand, progressively turns in a tight labial and vertical arc as development proceeds, and ends up with a 90° or more angulation to the coronal portion. The root apex will be seen as a very short ‘tail’ extending superiorly above the image of the tooth’s labial surface. The picture is reminiscent of a scorpion viewed from the front (Figure 5.13a). Although this is clearly recognizable, the periapical film gives only an indication of its height in the alveolus, while the detail of its curved axis and its general apico-incisal orientation cannot be defined. Confirmation of the diagnosis and the degree of its severity may then be positively completed using a tangential or lateral skull radiograph

(a)

(Figure 5.13b). This will give information that will help to build up a more comprehensive picture of the tooth, particularly regarding details of its morphology, height and the overall orientation of its long axes. Computerized tomography in these impacted incisor cases in general is helpful for locating the exact threedimensional positions of these teeth, while eliminating the superimpositions inevitably seen in plain film radiography [12]. It will also facilitate pinpointing the location of the initial curvature of the root of a dilacerate tooth, so that the orthodontist may decide whether an apicoectomy will later be necessary as root torque is being performed. Similarly, the relative position of the impacted tooth vis-à-vis supernumerary teeth will help the surgeon to decide where to open the initial flap and to more easily identify one from another and from the permanent incisor. It will also assist the orthodontist in assessing the relative difficulty of the case in attempting to resolve the impaction and to enable the design of appliance auxiliaries to suit the task.

Treatment timing In Chapter 1, we discussed the occurrence of a chance pathological finding during routine X-ray examination. Obstructions and any other form of pathology should be eliminated wherever possible before they have the chance

(b)

Fig. 5.13  (a) The periapical view of a dilacerate central incisor typically shows the coronal portion to be viewed through its long axis, with the labial surface facing superiorly and cingulum area clearly depicted inferiorly. The pulp chamber is depicted in cross-section as a circle in the middle part of the root, while the apical portion points vertically upwards and is visible superior to the labial surface of the crown (the ‘scorpion’ appearance). (b) The lateral cephalogram shows the lateral profile of the typical ‘classic’ dilacerate tooth, with its incisal edge at the level of the anterior nasal spine. The palatal aspect of the tooth faces labially and the labial aspect superiorly and posteriorly. The exact configuration of the obviously shortened root is obscured by the superimposition of adjacent teeth.

84  Orthodontic Treatment of Impacted Teeth to create delayed eruption, in order to obviate the need for orthodontic treatment. Very young children are encouraged to first visit the paediatric dentist as early as 3 years of age. The practitioner may perform a minimal radiological examination which includes a pair of bite wings to identify interproximal caries and, often, a maxillary anterior periapical view as part of the initial induction protocol. This film will show the developing central incisor teeth separated by a small midline space, with the midline suture running between them and the lateral incisors overlapping the distal third of the central incisor crowns, on either side. Occasionally, this view will also reveal the existence of a midline supernumerary tooth (mesiodens). As we pointed out at the beginning of this chapter, the presence of the extra tooth in this position will not always cause an eruption disturbance, although the risk is high. However, it will undoubtedly trigger a round of consultations between the parents and paediatric dentist on the one hand, and an orthodontist and an oral surgeon on the other, in search of an appropriate preventive treatment regimen to avoid later problems. The orthodontist will express the preference for removal of the mesiodens in order to permit the adjacent and unerupted permanent incisor teeth to develop normally, to erupt in their due time without assistance and into their ideal location. The oral surgeon will caution against early surgery because of the possibility of collateral damage being unintentionally inflicted on the dental follicles of the immature permanent incisors, given such a constricted and dentally crowded area from which to pluck the unwanted extra tooth. In addition, this exercise will not be possible to achieve without the simultaneous extraction of the deciduous incisors in order to gain access to the area. If we are to assume that the time is not ripe for the permanent incisors to erupt, then the patient will be anteriorly edentulous for an extended period and healing of the tissues following these deciduous extractions will probably result in a thickened scar tissue which will later obstruct the normal eruption of the permanent incisor teeth, when their time is due. By and large, the oral surgeon’s opinion should take precedence in this scenario, although there are times and situations when the removal should be undertaken, particularly as the child reaches the age when the teeth would normally erupt, as indicated by their root development. There is, however, no preventive treatment to be recommended once trauma has generated a dilaceration and, regardless of the steady progression of severity of the crown displacement, the patient will need to wait until corrective treatment is appropriate. When a patient presents with a single central incisor and both lateral incisors erupted, the normal eruption date of the second central incisor will have passed. The impacted tooth will be seen on the periapical radiograph to have at least two-thirds of its eventual root, which is the developmental landmark that determines that a tooth should be

erupted. Orthodontic and surgical treatment is, therefore, indicated at that time, both for obstructive impactions and for the dilacerated tooth. Often, at this early stage one may be able to foresee an obvious need for orthodontic treatment for other reasons, treatment that may not normally be advised until three or four years later. It is not reasonable to delay the resolution of an impacted central incisor for this period of time merely in the interests of trying to achieve a single-phase orthodontic treatment plan in the full permanent dentition. The alignment of the impacted tooth should be undertaken and executed efficiently, avoiding unnecessary attention to other details. Root uprighting and torqueing should be performed as indicated, but an ideal, final and artistic alignment is not the aim at this stage, and extending this first phase of treatment in order to achieve this is contraindicated. Once appliances are removed following the restoration of normality, there will be natural spontaneous changes in the alignment of these and adjacent teeth during the many months that follow and before the permanent canines come into their place. It must be pointed out to the parent that these changes are expected, normal and not a matter for concern. The parent and patient should be advised that further treatment will most probably be necessary at a later date to treat the rest of the overall malocclusion, and that retention of the aligned incisors against these physiological movements may often not be advised. In this regard, a further factor has come to light following a clinical study by the Jerusalem group [13]. It will be realized that the advice and treatment proffered in this book are based on many years’ clinical experience, with many hundreds of treated impaction cases. Patterns sometimes emerge that would never be noticed under the more usual and more random conditions of orthodontic practice. This is particularly so in relation to impacted central incisors, which are too often treated at a young age by the paediatric dentist, general practitioner or oral surgeon, who rarely follow up their cases to the same degree as do orthodontists. Impacted central incisors are usually first diagnosed at 7–8 years of age and they are best treated at that time, which is approximately four years before the maxillary canines are due to erupt. It had been noticed that there is frequent disturbance of eruption of the canine on the side of the formerly impacted central incisor, and a large study of unilaterally affected impacted incisor cases was set up to investigate this. Its experimental group involved patients who had been treated for an impacted central incisor and had been under follow-up care until the eruption time of the canines. On the side where the maxillary incisor had erupted normally, 4.7% of the neighbouring canines showed eruption disturbances or displacement. On the side previously affected by impaction of the central incisor, 41.3% of the

Maxillary Central Incisors  85 

(a)

(b)

(c)

canines showed abnormality, with 30.2% buccally displaced, 9.5% palatally displaced and 1.6% with complete canine–lateral incisor transposition. Half the buccally displaced canines were pseudo-transposed with the adjacent lateral incisor [13] (Figure 5.14). This study emphasizes the need to thoroughly exa­ mine the positions of adjacent teeth, particularly canines,

Fig. 5.14  The development of maxillary canine ectopia adjacent to an impacted central incisor. (a) An 8-year-old boy has an impacted maxillary left central incisor. The contralateral central incisor and both lateral incisors are erupted. The unerupted canines are similarly normally located and the deciduous canines had been extracted earlier. (b) At 9.7 years and without treatment, the left central incisor has improved its position and the right canine has progressed to a limited degree both vertically and slightly mesially. The left canine has also progressed vertically, but it shows considerable mesial migration, superimposing the lateral incisor root. In view of the degree of crowding evident in this case, the three deciduous first molars and all four first premolars were extracted. A short first phase treatment was instituted to expose and erupt the incisor only. (c) At 12.3 years and in common with successful serial extraction procedures, the crowding in three quadrants of the mouth has spontaneously resolved, with the normal eruption of the canines and second premolars. On the side of the resolved incisor impaction, the canine and lateral incisor are in an incomplete transposition relationship, with a strongly buccal and mesial displacement of the canine.

whenever an impacted incisor is present, and to warn parents of the distinct possibility of later canine erup­ tion disturbance. Just as important, it should serve to counsel the orthodontist to make the first phase of treatment as short as possible, without unnecessary attention being paid to meticulous alignment detail at that stage.

86  Orthodontic Treatment of Impacted Teeth

Attitudes to treatment There has been a more or less standard protocol of treatment available for several decades in the orthodontic profession in Europe regarding central incisors that are anatomically normal in their development, but impacted. The recommendations advice is: (a) that adequate space be prepared for the tooth in the arch; and (b) that the cause of the non-eruption (usually a supernumerary tooth) be eliminated. The impacted central incisor teeth may then be expected to erupt spontaneously [14–17]. Studies that have been made of patients who have undergone this type of treatment have shown disappointing results with regard to three important parameters: 1. Non-eruption. Spontaneous eruption has been variously reported as occurring in 54–78% of cases [7, 17, 18, 19], which represents a low degree of reliability. 2. Delay in eruption. Even when eruption occurs, the average time for the affected tooth to make its appearance in the mouth is between 16 and 20 months [7, 17, 19]. This is an unacceptably long period of time, when one considers that the patient will be without a front tooth or teeth for so many months. Additionally, 25% of the patients required two surgical episodes, followed by a waiting period of 2.5–3 years before the tooth erupted! [17]. In a retrospective study of cases in which (a) space had been provided, (b) the supernumerary tooth had been removed, and (c) a stainless steel crown had been cemented to the impacted tooth, eruption was found to have occurred in 96% of the patients. However, this took on average three years! [20]. 3. Alignment. The third parameter that showed disappointing results relates to the adequacy of spontaneous alignment. Mitchell and Bennett [17] found that 36% of the teeth in their sample failed to erupt and 41% of the remainder required orthodontic assistance to rectify incomplete results. This means that 62% of the whole sample of cases needed mechano-therapy at that stage. Gardiner [21] also found that spontaneous alignment occurred in only a minority of patients. Obviously, the criteria for deciding what constitutes an acceptable ‘alignment’ varies from one clinician to another and, one may be permitted to speculate, depends on whether the treatment is being carried out in a community health (managed care) clinic, a hospital orthodontic department (from which the material for these studies was collected) or a private orthodontic practice. Ashkenazi et al. [22], in their more recent study, have found that in 64% of the cases where supernumerary teeth had been removed without other forms of treatment, the impacted incisors failed to erupt and in 9% there was only partial eruption. In 17% of their cases, eruption was successful but into an ectopic location, aggregating to 90% of the cases in need of orthodontic treatment to bring these teeth into acceptable locations.

Some workers [23–25] recognized the need for affir­ mative action to control (or actively encourage) incisor eruption and they devised methods to perform this using wire loops and pinning, and even advocated the passing of a wire through a drilled hole in the incisal edge, in those early days. Mills warned against exposure of the crown of the permanent tooth during the procedure to remove the supernumerary tooth, pointing out that periodontal prognosis of the final result would be compromised [16]. Beyond the use of a simple removable appliance to make space in the arch for the unerupted incisor, he displayed a reticence to use mechano-therapy and seemed to have influenced opinion in Britain, where there appears to be a wide consensus that the use of appliances in bringing down impacted central incisors is to be avoided. His reasons for this are as follows: teeth often erupt spontaneously, without help • these loss of labial bony plate • poor gingival margin, with less attached gingiva • gingival level discrepancy • Little objective and evidence-based research was offered in support of these contentions, and it is equally open to speculation that most or all of these factors could be the result of overenthusiastic or otherwise poor surgical technique [26, 27]. This is discussed fully in Chapters 3 and 6. Few children are brought to the orthodontist before 10 or 11 years of age, yet the marred appearance of the child with a single erupted central incisor generally encourages the parent to seek treatment much earlier. An orthodontist’s lack of concern for a rapid solution in response to the parent’s disquiet for the child’s compromised appearance is insensitive, if not callous. This is particularly disturbing in the present context, since simple and effective means of achieving this are freely available.

Treatment of impacted central incisors Following determination of the overall orthodontic diagnosis, a problem list should be drawn up. Occasionally, there may be just one item on the list, namely the impacted tooth. More often, the presence of mandibular incisor crowding, posterior cross-bite or a class 2 relationship may also be noted, and the clinician must then decide which of these should be treated in this early treatment phase and which left until later. As a general rule, treatment priority should be given to the unerupted incisor, and all other orthodontic procedures will be delayed until the incisor has been brought into alignment. However, an anterior or posterior cross-bite and malalignment of the erupted adjacent incisors will usually be treated at the same time, either because it is simple, of short duration, convenient and advantageous to do so or because their treatment may provide the needed space for the impacted incisor tooth. By

Maxillary Central Incisors  87  and large, however, most other elements of an existing overall malocclusion will be left until the eruption of the full permanent dentition. An orthodontic appliance for use in the early mixed dentition As has been pointed out, opening the space for the unerupted tooth prior to removal of the supernumerary requires some form of orthodontic appliance. The simple removable plate is manifestly unsuitable, since the only positive influence it is capable of producing is a distal tipping of the adjacent teeth. While this creates space in the arch, it does so only at the coronal level. The effect is quite the opposite more apically, where the roots of the tipped teeth will be moved towards one another and directly into the path of the (hopefully) erupting impacted tooth. Vertical force control on the impacted tooth is difficult to achieve with a removable appliance. Corrective rotatory movement of the finally erupted tooth is rarely adequate, while uprighting and torqueing root movements are quite impossible. A practitioner using this method would essentially be placed in the position of an observer, being able to exercise virtually no control over eruption, which is the most important aim of the exercise. It is true that in the event that the tooth erupts (a) spontaneously, (b) into good alignment and (c) within a reasonably short period of time, there will have been much to gain by this relative inactivity. However, an impacted tooth initially shares the limited labio-lingual width of the alveolar ridge with a supernumerary tooth, which is likely to have prevented its eruption. Sharing this space usually causes the root of the central incisor to become displaced in either or both the labio-lingual and mesio-distal planes of space. It is therefore likely that, in the final analysis, the erupting tooth will require root movement in a labio-lingual (torqueing) and/or a mesio-distal (uprighting) direction. This may be accompanied by the need for significant rotational movement. It becomes evident that a specific, purpose-designed type of appliance is indicated, one that has the potential to deal efficiently with all these eventualities. Given the significantly wide spectrum of cases where spontaneous eruption cannot be expected to result in a satisfactory alignment or where eruption has failed, it is essential to seek an alternative method of mechano-therapy which provides simple and rapid solutions to all the movements required. A technique must be employed that provides satisfactory answers to the following four aspects: 1. The appliance should have the capability to level and rotate the erupted incisor teeth rapidly and, with controlled crown and root movements, open adequate space to accommodate the impacted tooth. This space is demanded at both the occlusal level and for the entire length of the roots of the adjacent teeth.

2. The surgical exposure of the crown of the impacted tooth, together with the bonding of an attachment, must be performed in a manner that will achieve a good periodontal prognosis, as described in Chapter 3. Therefore, the appliance must hold the space during and after the surgical procedure, while not hindering the surgeon. 3. Light and controlled extrusive forces must be generated from the appliance to be effective over a long range of movement to bring the tooth down to the occlusal level, and attention must be paid to providing anchorage which is adequate for the purpose. 4. Final detailing of the position of the impacted tooth and its erupted neighbours must be completed without changing to another appliance, including movement of the crowns and roots of each of these teeth in all three planes. 5. While it is important that the appliance has the potential to achieve a good finish, we have argued against aiming for the meticulous placement of teeth in the young child – the pursuit of perfection and a ‘final’ alignment of the anterior dentition are contraindicated at such an early stage of dental development. This is particularly so when the permanent canines are very high and in close relation with the apical third of the lateral incisor roots. Typically, our young patient has two molars and three (or fewer) incisor teeth of the erupted maxillary permanent dentition. Strictly and in order to eliminate the long span between the permanent molars and lateral incisors, it is possible to include the deciduous canines and molars into a fully bonded appliance scheme with the use of regular brackets. Because of the anatomy of their buccal surfaces, this presents several difficulties. In the first place, no company presently manufactures bracket bases suitable for deciduous teeth, and bonding brackets designed for permanent premolars and canines will leave large voids and ledges that will have to be filled with composite bonding material. In order to improve the fit of the bases, the buccal surfaces would have to be fashioned to a more accommodating form which, given the short crown height characteristic of these deciduous teeth, would be challenging to achieve satisfactorily. The diminutive crown height of the deciduous teeth restricts the options for determining bracket height. This has repercussions on the subsequent fabrication of archwires, with bends and offsets included in each of the series of archwires to ensure passivity, because there is rarely any need or intention to move them. Accordingly, most practitioners side-step them and band only the molars, with bonded brackets on the incisors, leaving a long span of unsupported wire in the buccal region – the 2 × 4 appliance. With short inter-bracket distances in the anterior region, a light flexible wire will be needed to perform the initial levelling, aligning and space adjustment. But this wire is completely unsuitable in an unsupported state for the long

88  Orthodontic Treatment of Impacted Teeth span between lateral incisors and the first molars. It is impossible to avoid distortion and there can be no vertically extrusive force directed from the molar tubes, even when the archwire gauge is substantially increased. Anchorage for the extrusive movement of the impacted tooth is therefore poorly exploited and is limited to the adjacent incisors, which progressively intrude as the treatment proceeds. Conversely, using a much heavier archwire to achieve an acceptable degree of support in the posterior region and an extrusive component anteriorly is not compatible with the very specific finer movements needed for the levelling, alignment, rotating, uprighting and torqueing that may be necessary for the initially malaligned incisor teeth. Johnson’s (modified) twin-wire arch An updated version of the obsolete and largely forgotten Johnson twin-wire appliance [28, 29] presents certain unique features which make it especially suited and efficient in the many treatment aspects of this specific problem in the mixed dentition stage, and particularly regarding anchorage in the vertical plane. The appliance is based on fixed molar bands, interconnected by a soldered palatal arch (Figure 5.15). Long, narrow gauge (0.020 in internal diameter) tubes slide freely, but accurately and without lateral ‘play’ in the round molar buccal tubes (0.036 in), and are made to extend anteriorly to the deciduous canine area. An initial anterior, multistrand, sectional 0.036 in round molar tubes is used. The anterior sectional archwire in this case is a single 0.016 in wire, since only one erupted permanent incisor is present and the usual multi-strand wire is not needed. The alignment of the buccal tubes shows a downward tip as they proceed mesially, to encourage open bite closure and to aid the mechanically assisted eruption of the impacted tooth. Wire (0.0175 in) or nickel–titanium wire (0.016 in) is held in the long narrow tubes by a friction fit, created by placing three or four bends in the multi-strand wire (more difficult to do effectively with the nickel–titanium wire) and then drawing it through the tube between two pliers, one of which should be grooved. When the appliance was in general use several decades ago, as its name suggests, two fine 0.010 in stainless steel wires were used in the anterior portion to provide improved flexibility and springiness, which today’s nickel–titanium and multi-strand stainless steel wires achieve much better. The first step in the construction of the appliance requires that an impression of the dental arch of the patient is taken, with properly adapted, plain molar bands in place. The bands are removed carefully from the teeth and re-set into the impression before pouring. On the model, a palatal arch is fabricated and soldered to the lingual side of the molar bands to provide resistance to the extrusive forces that will later be needed. In a case requiring more than minimal anchorage, it is advisable to

(a)

(b) Fig. 5.15  (a) An occlusal view of Johnson’s (modified) twin wire arch, to show the soldered palatal arch. (b) 0.020 in round tube sections are slotted into the 0.036 in round molar tubes. The anterior sectional archwire in this case is a single 0.016 in wire, since only one erupted permanent incisor is present and the usual multi-stranded wire is not needed. The alignment of the buccal tubes shows a downward tip as they proceed mesially, to encourage open bite closure and to aid the mechanically assisted eruption of the impacted tooth. Reprinted from ref. [30], with permission.

add an acrylic (Nance) button to the palatal arch. Buccal tubes are best soldered to ensure precise alignment with the anterior bracket position. Slight upward or downward tipping of the molar tubes to suit the needs of an individual case (Figure 5.13b) will create a significant intrusive or extrusive vertical force component on the anterior teeth. The labial archwire is constructed on the model, initially using the multi-strand or nickel–titanium wire in the buccal tubes. The appliance is transferred to the mouth and cemented in place, brackets are bonded to the anterior teeth and the prepared initial archwire is placed. The brackets may be of virtually any type, although there are several advantages to Begg brackets in this situation as their vertical slot makes them particularly suited to the light vertical traction that may need to be applied to encourage eruption of the impacted tooth (Figure 5.16).

Maxillary Central Incisors  89 

(a)

(b)

(c)

(d)

Fig. 5.16  Impacted central incisors due to unerupted supernumerary teeth. (a) Panoramic view one year pre-treatment shows the permanent lateral incisor well advanced in their eruptive progress. The two supernumerary teeth are superimposed on the unerupted central incisors. (b) Periapical radiograph taken on the same date. (c) Intra-oral anterior view shows erupted lateral incisors and over-erupted mandibular incisors in contact with upper gingiva. (d) With the teeth apart, the degree of mandibular incisor over-eruption is evident. (e) Three-dimensional view seen on CBCT image shows the central incisor to be very high, with supernumeraries inferiorly and palatally situated. (f) A transaxial (vertical) CBCT slice cuts through the central incisor, supernumerary, the lateral incisor and the mandibular lateral incisor in the superior–inferior direction. (g) The modified Johnson twin-arch 2 × 4 (2 × 2) appliance in place, using Begg brackets on the lateral incisors. (h) At surgery, the supernumerary teeth are identified on the palatal side and extracted to leave empty sockets. (i) A minimal area of the labial surface of the incisors is exposed, without removing surrounding bone. Removal of bone inferior to the incisors would have left a deep defect, by including the sockets of the extracted supernumerary teeth. (j) Attachment bonding. (k) The lock pins in the Begg brackets are released to permit raising the archwire and ensnarement by the twisted ligatures. (l) The look pins are re-engaged to apply vertical traction to the incisor teeth. (m) The full flap is sutured back to its former place. (n) Close to the time the teeth are erupted, a similar Johnson 2 × 4 appliance is placed in the mandibular dentition to align and intrude the lower incisors. (o) Anterior intra-oral view, at the end of phase 1. (p) Note the root of the left lateral incisor is displaced palatally by the labially palpable and unerupted canine. This will be addressed in phase 2 of treatment. (q) Panoramic view at completion of phase 1. (r) Periapical view of the central incisors at the end of treatment.

(e)

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(g)

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(k) Fig. 5.16  (Continued )

(l)

Maxillary Central Incisors  91 

(m)

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(r)

Fig. 5.16  (Continued )

92  Orthodontic Treatment of Impacted Teeth By the second or third visit, some weeks later, alignment of the three erupted incisor teeth will usually have been achieved and the multi-strand/nickel–titanium wire is discarded and replaced by a plain round stainless steel 0.018 in or 0.020 in wire, which is similarly inserted in the long narrow gauge buccal tubes. An expanded coil spring is threaded onto it and tied into the anterior portion, compressed between the teeth on either side of the impacted tooth (Figure 5.17). Space is gained very rapidly, with the movement being at least partly achieved by tipping, depending on which brackets are used. Subsequent uprighting will need to be performed with vertically offset and compensated bends or using auxiliary springs. Once there is adequate room for the unerupted tooth and uprighting has been achieved, a carefully measured piece of stainless steel tubing should be threaded onto the archwire, the length of the tubing being cut so that it fits exactly between the brackets of the teeth adjacent to the impacted tooth. The presence of the tubing between the adjacent teeth ensures maintenance of the required space and contributes to the rigidity of the archwire. This in turn provides a firm platform from which light force may be applied to the unerupted tooth. Together with the rigid buccal tube arms and the soldered palatal arch, this constitutes a very significant anchorage unit in this biomechanical system. At this point the patient is ready for the surgical episode, at which an over-retained deciduous incisor and any buried supernumerary teeth are removed. The permanent incisor is exposed and an attachment placed, without removing any part of the orthodontic appliance. Erupting the impacted tooth ideally requires relatively little force, but a mechanism with a long range of action. As we have discussed in Chapter 4, directly ligating with elastic thread between the twisted pigtail ligature that was tied into the eyelet at the time of surgery and the main archwire is a very poor method, since force is high and uncontrolled and its range minimal. A more appro­ priate system is to stretch an elastic chain horizontally between the brackets on the teeth on either side of the affected tooth and to raise the middle of the chain and ensnare it over the rolled-up pigtail ligature. This pro­ duces a much more controllable force with a good range of movement. If the patient is seen every 3 to 4 weeks for adjustment, a previously obstructed tooth will usually erupt very rapidly and within a few months will be visible, providing the young patient with a more acceptable appearance which will enhance his self-confidence and self-image. The favourable time factor achieved by this approach is an advantage that should not be underestimated and one that needs to be taken into account, even when treating the younger patient. An obstructed incisor will take less time

to resolve than a dilacerate tooth, simply because it has a shorter distance to travel and considerably less root movement to experience, but the treatment principles are the same. At the point when the tooth reaches the occlusal level, a reassessment is made as to whether uprighting, torqueing or rotation of the tooth is needed, and whether it should be done at this stage or in the second phase of treatment, assuming that this will be necessary. If so, the eyelet is removed and a bracket similar to that on the other teeth is placed in its ideal position. Finishing is then achieved in the appropriate manner. In the dilacerate incisor case illustrated in Figure 5.17, the final photographs were taken at the end of phase 2 of treatment, at age 13 years and after considerable labial root torque had been achieved, both before and following the apicoectomy and root canal treatment. The construction, placement and activation procedure of the appliance is very simple and does not require a high level of expertise. The laboratory stage of appliance construction requires accurate soldering of the palatal arch and careful alignment of the buccal tubes, which a good orthodontic technician should master very quickly, although the orthodontist may prefer to do this himself. In the mouth, cementation of the bands and bonding of the brackets is routine, and the application of the prepared archwire presents a neat and robust appliance in the long span between the molar tubes and the incisor brackets, while anteriorly providing light and gentle vertically directed forces of good range, to give rapid results. The presence of the palatal arch will ensure that undesired movement of the adjacent incisors and the distant anchor molars cannot occur. In common with other patients with unerupted incisors, the patient with arrested root development will usually seek advice and treatment before the age of 9 years. By contrast in these cases, however, more than one and occasionally all the maxillary incisors may have been affected, since the condition is usually the result of a severe blow to the area at a very young age (Figure 5.18). While the principles of treatment are the same as for the patients we have already discussed, it is clear that in the most severe of cases, when all four incisors are aff­ ected, a different labial arch mechanism is needed. The same basic appliance, with palatal arch soldered to molar bands, is cemented into place before the surgical exposure is performed. This type of case is much more demanding on molar anchorage, and an acrylic (Nance) button on the palatal arch should be considered mandatory. All four impacted incisors are exposed and eyelets bonded to them, with the pigtail ligatures trailing through the sutured edges of the flap. In this case, a heavy buccal archwire of 0.036 in gauge is slotted into the round tubes on the molar bands, and is held at a minimal distance labial

Maxillary Central Incisors  93 

(a)

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(e)

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Fig. 5.17  An 8-year-old female with a dilacerate maxillary incisor and considerable caries experience treated entirely by postgraduate students. (a–c) Clinical intra-oral views of the dentition. Space has been lost due to tipping of the adjacent incisors. (d–f) Panoramic, occlusal and lateral cephalometric radiographs show the typical configuration and location of the affected tooth, adjacent to the anterior nasal spine. (g–i) A modified Johnson’s twin-wire arch has achieved a reopening of the space with an open coil spring. The space opening has been deliberately exaggerated and the spring is subsequently replaced by a measured and contoured steel tube to act as a space maintainer. This tube and the buccal tube arms, together with the rigid soldered palatal arch, constitute the very significant anchorage unit in this biomechanical system. (j–n) In preparation for force application, a T-pin is inserted from the occlusal into the vertical slot of the bracket of the two adjacent incisors. The surgical flap is taken from the crest of the ridge in order for it to include attached gingiva and is reflected high into the sulcus to expose only the palatal aspect of the incisor, which faces forwards. An eyelet attachment is bonded and the flap fully sutured to its former place, with the pigtail ligature exiting through its sutured edge and turned upwards into the form of a hook. The mid-point of a clear (and barely visible) elastomeric module, stretched between the two T-pins, is gently raised and ensnared in the hook, to provide an easily measurable, light traction force to the tooth. (o, p) Occasionally, as was seen in this case, providing the tooth with adequate torque will bring its forward-facing root apex through the labial plate of bone, to become excessively prominent in the sulcus. Radiographs of the completed treatment show the affected tooth after elective root treatment and apicoectomy. (q–u) The final treatment outcome of the overall malocclusion. The clinical crown is slightly longer than that of its antimere and is the only clue to identifying the affected tooth. There were no differences between the two teeth regarding any other periodontal parameters. A removable retainer is worn at night.

94  Orthodontic Treatment of Impacted Teeth

(g)

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Fig. 5.17  (Continued )

(m)

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Maxillary Central Incisors  95 

(q)

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(u) Fig. 5.17  (Continued )

96  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

Fig. 5.18  The initial diagnostic radiographs and computerized tomographic imaging of this patient, at age 7.4 years, were presented in Figure 5.10. This figure displays the surgical exposure of the affected central incisor showing its extreme height, with the lateral incisor inferior to it and directly in its potential eruption path. (a–d) Surgical exposure displays the affected central incisor to be very high and the lateral incisor inferior to it and directly in its potential eruption path. Eyelets are bonded and the pigtails separated and labelled for subsequent identification. The surgical flap is fully replaced and only the pigtail of the lateral incisor attachment ensnared into the archwire of the modified Johnson’s twin arch, which is initially free of its engagement in the sole existing bracket, on the only fully erupted incisor. By pinning the archwire back into the vertical slot of the Begg bracket, extrusive force is applied to the lateral incisor. The pigtail from the central incisor lies freely unattached. (e, f) Periapical and tangential views show the enormous height discrepancy at the time of exposure. (g–j) Clinical views showing the erupted lateral incisor and the use of a coil spring to move it distally, reopening space for the central incisor, to which traction is then applied. (k) Once erupted, the central incisor was torqued and uprighted, using auxiliary springs with the very lightest of forces, suitable to the severely reduced root length. In contrast to using ‘straight wire’ mechanics, with tip and torque built into the bracket angulation, the force exerted by these auxiliaries (when placed in Begg or Tip-Edge® brackets) can be easily measured, controlled and tailored to the needs of the moment. (l–n) Completion of the first phase has provided the child with a front tooth 14 months later, at age 8.6 years. Note the periodontal condition on the labial side of this tooth, which is due to the coronally sited junction of the incompletely formed crown and its right-angle dilaceration with the very short root. No retainers were used subsequently. (o–q) At age 11.1, the full permanent dentition has established and there is slight positional deterioration in the alignment of the incisor while its periodontal condition remains unchanged. The present aim is to maintain the tooth until it can be replaced by an implant, and to delay second phase orthodontic treatment until closer to that time. (r–u) the patient seen at 18 years in these intra-oral frontal and occlusal views, with new periapical and panoramic views of the dentition still showing the trauma-driven developmental cervical defect. Alveolar bone height is good and she has now been referred for an elective replacement of the left central incisor with an implant borne restoration.

Maxillary Central Incisors  97 

(e)

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Fig. 5.18  (Continued )

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Fig. 5.18  (Continued )

Maxillary Central Incisors  99 

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Fig. 5.18  (Continued )

to the line of the arch with bayonet bend stops at the molar tubes (Figure 5.19). The anterior portion of the heavy labial arch is raised with gentle finger pressure and ensnared by the four pigtail ligatures, thereby applying a gentle extrusive force to the four unerupted teeth. At the completion of this phase of treatment, and for all of the types of problem described here, it is good practice to reassess the overall orthodontic condition. Further treatment may be advised at this stage, as mentioned earlier. More frequently, however, the appliance is removed and the

patient is placed on recall over a period of several years, until the eruption of the full permanent dentition, when a new clinical assessment is made and an overall treatment plan developed for the entire dentition. In the meantime, the night-time wear of a simple removable retainer is usually advised in order to hold the achieved alignment. Delaying further treatment affords the orthodontist the opportunity to monitor the survival and progress of the tooth/teeth and the ability to predict its/their long-term prognosis with greater reliability. This is a wise precaution

100  Orthodontic Treatment of Impacted Teeth

(a)

(b)

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(d)

(e)

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Fig. 5.19  (a) This 9-year-old child has lost alveolar bone height following traumatic avulsion of his anterior deciduous teeth at age 2 years in an accident. (b, c) The panoramic and lateral cephalometric films show very little root development of all maxillary incisors. The central incisors are at the level of the anterior nasal spine. (d) View of soldered palatal arch. (e) The incisors are surgically exposed (note the large areas of hypoplastic enamel). (f) Eyelet attachments are bonded. (g) After suturing, a self-supporting ‘stopped’ labial archwire is placed into the molar tubes. Displaced superiorly by gentle finger pressure, the anterior part of the archwire is ensnared by all four steel pigtails, to deliver extrusive force. (h, i) Tangential and anterior occlusal radiographic views immediately postsurgery. (j) A clinical view at completion of the first phase of treatment. (k, l) Periapical and tangential radiographs at completion of treatment. Note poor development, anatomic form and life expectancy of the teeth at the end of treatment. Uprighting of the roots was considered inappropriate.

Maxillary Central Incisors  101 

(g)

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(i)

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(k) Fig. 5.19  (Continued )

(l)

102  Orthodontic Treatment of Impacted Teeth before committing to overall orthodontic treatment that may often require irreversible steps to be taken, such as extractions.

Prognosis The obstructed impaction The prognosis of the result depends on several factors.

Root length

For teeth whose impaction is due to obstruction, the root length is usually normal, although in some cases it may be somewhat shorter because of the cramped circumstances in which the root developed prior to the treatment. Nevertheless, mild shortening will not normally adversely affect prognosis. Surgical exposure

Overly radical exposure, taken down to and sometimes beyond the CEJ, with complete removal of the follicle is an unnecessary and harmful step which will inevitably have a long-term debilitating effect on the periodontium. Even though the eruption of the impacted tooth will bring with it new alveolar bone, this will not be sufficient to establish a bone level similar to that of the adjacent teeth and there will be an increased crown length relative to its unaffected and normally erupted antimere.

Type and height of periodontal attachment

If the surgeon opened a window in the oral mucosa directly over the impacted tooth, above the attached gingiva, then the prognosis of the result will be relatively poorer. Steps should be taken to properly manage the muco-gingival soft tissue by raising a full flap from the crest of the ridge at the time of the surgical exposure and by fully suturing the wound, at the end, wherever appropriate. If this is done, the tooth will be erupted through the attached gingiva and the periodontal result will be good. It has already been pointed out that in cases of obstructive incisor impaction the long axis of the unerupted tooth is abnormally oriented due to the presence of the extraneous displacing hard tissue. The mesiodens or odontome are usually palatally placed and the root of the incisor consequently displaced labially. Thus, when the tooth is drawn vertically downward following a closed exposure procedure, it will tend to break through the oral mucosa above the attached gingiva and the newly erupted incisor will exhibit a long clinical crown because of the relative labially prominent cervical region and a thin and delicate mucosal attachment.

In order to avoid this unfortunate sequela, traction may be applied in a downward and palatal direction in an attempt to draw it though attached gingiva. However, this will concurrently tip its root labially, thereby increasing the amount of subsequent root torque that will be necessary. A better approach is to draw the tooth down until it bulges the labial oral mucosa and then to pre-empt its eruption by performing an apically repositioned flap at this late stage. The flap is raised from the crest of the ridge immediately inferior to the unerupted tooth and this formerly attached gingival tissue is sutured over the labial (superior) aspect of the tooth. Further traction will bring the tooth down and into alignment with the repositioned tissue. Performing this procedure as the initial exposure may be preferred if the vertical displacement of the tooth is relatively mild but, for a higher displacement, the twostage procedure described here will produce a much better outcome. A dilacerate incisor will require a similar surgical initiative. A closed exposure procedure is probably the only reasonable surgical approach to take in these cases in the first instance, because of its extreme ectopic location in the root of the nose. As the tooth is drawn vertically downwards, its incisal edge bulges the oral mucosa covering the labial side of the alveolar ridge and the new horizontal orientation of its crown may be clearly outlined through the almost transparent mucosa. Here, too, one should wait until the tooth is well down and close to eruption before performing a similar apically repositioned flap. In this case in particular, the tightness of the suturing of the tissue above the crown of the tooth will exert considerable pressure to assist in the further traction of the tooth into its place. When the crown has been brought down to occlusal level, the extreme degree of labial root torque that is needed to properly and artistically reposition the crown of the tooth will become apparent. The question then arises as to how much of this root torque should be performed in the very young patient and how much should be left until the phase 2 of the treatment in the permanent dentition. It is quite clear that any appreciable torque will tip the curved root end forward causing it to protrude labially and to alter the contour of the mucosa covering the alveolar process. Yet for most cases this will still not be enough to adequately reorient the crown. Nevertheless, in the early mixed dentition this should be accepted as representing the completion of phase 1. The appliances should be removed and retainers placed. Over the next year or so, there may be some relapse of the achieved root torque. This is due to the final and natural apexification of the root end being resisted by the labial periosteum, which causes a reversal movement affecting the tooth axis. It becomes apparent therefore that, from the orthodontic viewpoint, the problem is considerably more challenging.

Maxillary Central Incisors  103  In the young patient, a careful study of the tangential radiograph may reveal the shape and orientation of the root, although this will be much more accurately assessed on a computerized tomography (CT) series. The more apical the dilaceration vis-à-vis the coronal third of the root, the better the prognosis. Similarly, if the dilaceration is in the crown of the tooth, the prognosis improves the closer it is to the incisal edge. A dilaceration situated apical to the coronal third of the root provides no serious impediment to orthodontic alignment and it should have an excellent prognosis. The crown of the tooth should be surgically exposed and an eyelet bonded to it. In most cases, the only surface of the crown that is available for the eyelet is the palatal surface. This surface faces the operator when the tooth is first exposed, while the anatomically labial surface of the tooth is inaccessible, facing superiorly and posteriorly and buried in the hard tissue adjacent to the anterior nasal spine. A stainless steel ligature is threaded through the eyelet, twisted into a pigtail and drawn downwards, to be ligated with an upward stretched horizontal elastomeric module, as described above and in Chapter 4. Care should be taken not to apply much pressure initially, since the tension introduced by suturing the surgical flap may itself apply a considerable downward force to the tooth in the first few weeks. As the crown of the tooth responds to the force it rotates downwards, causing the incisal edge of the tooth to become labially prominent, outlined beneath the oral mucosa on the labial side of the alveolar ridge. At the same time, the root apex rotates forward towards the labial plate of bone. For the most part, these cases may be completed without the root apex ever protruding excessively in the labial sulcus. If the apex becomes prominent and further labial root movement is still desirable, this will necessitate a surgical intervention, performed with the aim of amputating the root apex of this tooth. The labially directed portion of the root, corresponding to the post-traumatic developmental portion, is sectioned in a line that is continuous with the labial side of the main coronal portion of the root of the tooth. The pulp is extirpated and the root canal is obliterated using a combined conventional (coronal) and a surgical retrograde endodontic approach, wherever possible (Figure 5.17). Further extrusion and appropriate root torqueing of the incisor may necessitate a second rootshortening procedure, but, if the first procedure was delayed as late as possible and the root apex amputation was properly designed, this may usually be avoided. This is most advantageously done in the final stage of treatment in the full permanent dentition, at the dental age of 12–13 years. Further root torque will need to be initiated until the crown orientation is ideal, at which point endodontic treatment and apicoectomy of the prominent root will

need to be performed. In these cases, the outcome will display a shortened root, but the normal crown and soft tissue appearance should be excellent and largely indistinguishable from the adjacent incisor. The degree by which the final prognosis of the short-rooted central incisor will be compromised depends largely on how much root remains after the amputation has been performed. The desired site of the amputation is entirely dependent on the location of the dilaceration, and it eliminates a majority of that portion of the root apical to it, which had developed after the traumatic episode. Thus, the closer the dilaceration is to the coronal portion of the root, the shorter will be the final root length at the completion of treatment and the poorer its prognosis. Treatment duration As we have seen, treatment of impacted central incisor teeth is generally undertaken in the early to middle period of the mixed dentition, which means that it is classed as a phase 1 treatment, with its aims usually limited to resolution of the incisor impacted. Phase 2 becomes appropriate only in the fully erupted permanent dentition, at around the age of 12–13 years. Naturally, the later this treatment is embarked upon, the greater is the likelihood that the two phases will be incorporated into one long period of comprehensive biomechanical therapy. In an unpublished study [31], the duration and the rate of success of this phase 1 treatment was evaluated in relation to both obstructed and classic dilacerate impacted incisors. The study sample included 59 patients, 31 associated with supernumerary or odontome obstruction and 28 with dilaceration. Three stages of treatment were defined: T1 – the pre-surgical period between the application of fixed orthodontic appliances and the referral for surgery T2 – the period between the surgical exposure and the engagement of the orthodontic bracket of the impacted tooth in the labial archwire T3 – the period from the engagement in the archwire to completion of phase 1. For the group as a whole, T1 was found to be 5.2 months, with a range of ±4 months, the impaction resolution period T2 took 8 months (±5months) and the T3 to completion was 6.3 months (±4.5 months). While each stage may individually not appear very long, in total they amounted to 19.5 months (±9 months), which is a considerable period. Taken individually, the duration of treatment in the obstructed cases was 17 months (±7 months) and that of the dilacerate cases 22 months (±17 months), largely due to the greater complexity of treatment of the dilacerate

104  Orthodontic Treatment of Impacted Teeth incisors, particularly in the T3 period, where much labial root torque needs to be achieved. This is also reflected in the success rate of the two constituent diagnoses, with one failure (97%) in the obstructed group and five (82%) in the dilacerate group.

Relative bone height of the crestal alveolus In Chapter 6, we will refer to the fact that when teeth are supra-erupted, their vertical movement is accompanied by a vertical increase in their supporting alveolar bone. Thus, when the impaction of a tooth is resolved by augmenting the natural eruptive force following the removal of the causative agent, it will be seen that the bone support of that tooth will be greater than that around normally erupting adjacent teeth [27, 32–35]. However, this positive response on the part of the alveolar bone to the extrusive forces is dependent on the amount of pressure applied being within relatively narrow limits. A periapical radiograph taken at that time will show radiolucent areas where new bone is being laid down – new bone does not show up on X-ray. A similar view taken 4–6 months after cessation of this movement, when the bone will have matured and calcified, will show the excellence of its regeneration In the event that excessive extrusive force is brought to bear on these teeth, eruption will also occur rapidly, but without a regeneration of alveolar bone. The result will be characterized by the tooth having a long clinical crown and considerable mobility. The periapical radiograph performed even six months later in this case will show a much reduced bone level around the newly and apparently successfully resolved impaction. The prognosis of such a tooth will be impaired.

Preservation of vitality During the surgical procedure, removal of awkwardly placed supernumerary teeth may lead to an unavoidable devitalization of the impacted tooth. In the hands of a competent surgeon this is quite rare and it is more likely that excessive extrusive force, which compromises its bony support, may be a factor in bringing about the demise of its pulpal tissue. Oral hygiene During the initial phase of eruption of an impacted tooth, the surrounding gingiva is sensitive, tender and bleeds very easily. This will usually make the younger patient very apprehensive of brushing the area regularly and to an adequate standard of cleanliness. Secondary inflammation of the gingiva and a concurrent adverse effect on the regeneration of bone will be the inevitable result [36].

For all these reasons, the surgeon should be meticulous in the proper planning and execution of the surgical technique and the orthodontist in the application of extrusive forces whose magnitude is difficult to control. Elastic ligation thread is used widely for applying traction to impacted teeth, by tying it directly and tightly between the attachment and a relatively rigid archwire. It is exceptionally difficult to accurately judge the amount of force being applied by this method and so, when it is the only practical one available, great care should be taken not to tie too tightly. Wherever possible, alternative methods should be used, as described in Chapter 4. As the impacted teeth respond to the traction force, the orthodontist should be perceptive, aware and responsive to their changing relationship to the soft tissues, altering force directions as necessary and, if needed, requesting mucogingival surgery to cause the tooth to exit the tissues in the best possible location from both the periodontal and aesthetic points of view. Vertical ‘box’ elastics are often used in routine cases in orthodontics to enhance intercuspation at the close of treatment. These elastics are small and can produce forces which are very much in excess of that desirable for a single impacted tooth. This will be increased further during mouth opening. It is difficult to measure or control the forces applied in this way. Nevertheless, this is a valuable tool and should be used with only the very lightest and largest of elastics. It should also be remembered that, as orthodontists, we are apt to apply more than adequate extrusive forces by the downward deflection of an archwire and we then place a ‘box’ elastic, in addition, just to be sure! The aggregated force may thus become very much in excess of the physiological limit. The instructions to the patient who is prescribed this form of vertical intermaxillary anchorage reinforcement should insist on full time wear, including at meal times and removed only for toothbrushing, in order to maintain a light continuous force. Impaction due to past trauma Soft tissue obstruction

When deciduous incisor teeth have been lost early and well ahead of the time that the incisors are ready to erupt, the mucosa will generally heal over with a thickened attached gingival tissue, which is often fairly fibrous. This tissue may then act as a barrier, preventing the normal and timely eruption of the permanent incisors, although they are at the appropriate developmental stage for eruption. The only treatment needed to overcome the resistance of the thickened mucosa to eruption is surgical, involving an incision in the thickened mucosa, enough to expose the incisal edges of the already bulging crowns of the teeth. This is described in Chapter 3 and the prognosis is usually excellent.

Maxillary Central Incisors  105  The benefits of salvaging severely compromised impacted teeth

It is clear that the long-term prognosis of many dilacerated teeth and teeth with arrested root development is poor, and their extraction and replacement may be a part of the long-term treatment strategy, as noted in the treat­ ments described in the case reports above (Figures 5.17–5.19). This being so, the most pertinent question that needs to be asked regarding these teeth is whether there is any justification to expend energy on treating them at all. The answer is not necessarily the same for every case, and each must be considered on its own merits. No decision should be made until the practitioner first considers the following points in relation to the particular patient concerned: 1. A permanent artificial solution cannot be considered much before early adulthood, whether by conventional prosthodontic treatment or implant-borne restoration. 2. Any tissue-borne form of temporary replacement (partial ‘flipper’ denture) will be far less satisfactory from every point of view. Even when this solution is acceptable to the patient, long-term wear will lead to deterioration in the health of the palatal mucosa and of the gingiva adjacent to any teeth which are in contact with the removable denture – not to mention the possibility of enamel caries of the teeth concerned. 3. Any tooth-borne, resin-bonded (Maryland) bridge replacement may require some preparation of the adjacent teeth and may be unreliable in the long term [37]. It is unlikely that this restoration will remain for more than a few years, and an implant-borne permanent substitute will be preferred in early adulthood, which means that the earlier invasive tooth preparation will need to be reversed by restorative treatment. 4. Should it be decided to extract the dilacerate tooth, the already deficient alveolar ridge area will become even more deficient both vertically and in its labio-lingual width, making the case unsuitable for an implant and unaesthetic for a conventional bridge. 5. Orthodontic alignment of the dilacerate tooth will bring with it much alveolar bone to enhance both ridge width and vertical height to normal dimensions. 6. The retention of even a very short-rooted tooth will preserve the normal shape and architecture of the alveolar ridge. 7. The original trauma in these cases may have caused the teeth to develop close to the nasal floor and this may have been the cause of stunting of the root growth and loss of their eruptive potential. When these teeth are drawn down towards the line of the arch and assuming they still have open apices, they will often rapidly develop long spindly roots, which may improve their prognosis (Figure 5.19). With suitable restorative enhancement of their crowns, these rescued teeth may then usually be

maintained well into the second and sometimes third decade of life. Under these conditions, orthodontic alignment of the impacted and dilacerated tooth will usually be preferable. For the most part, however, this procedure must be viewed as providing only a temporary solution and, at a later time, when growth has ceased and conditions are more favourable, some form of permanent restoration will need to be considered. In the meantime, however, this decision will have been made much easier and will include a wider choice of prosthodontic modality options, and the result will be much more satisfactory in the long term because of the enhancement of the bony ridge that will have accompanied the eruption and retention of the damaged tooth. Apical root dilacerations

In the very young patient, treatment of the dilacerated incisor follows much the same lines as described for the obstructed incisor. Before this is done, however, a careful study of the tangential radiograph may reveal the shape and orientation of the root, although this will be much more accurately assessed on a CT series – the more apical the dilaceration vis-à-vis the coronal third of the root, the better the prognosis. Similarly, if the dilaceration is in the crown of the tooth, the prognosis improves the closer it is to the incisal edge. A dilaceration situated apical to the coronal third of the root provides no serious impediment to orthodontic alignment and it should have an excellent prognosis. The crown of the tooth should be surgically exposed and an eyelet bonded to it. In most cases, the only surface of the crown available for the eyelet is the palatal surface. This surface faces the operator when the tooth is first exposed, while the anatomically labial surface of the tooth is inaccessible, facing superiorly and posteriorly and buried in the hard tissue adjacent to the anterior nasal spine. A stainless steel ligature is threaded through the eyelet, twisted into a pigtail and is drawn downwards, to be ligated with an upward stretched horizontal elastomeric module, as described above and in Chapter 4. Care should be taken not to apply much pressure initially, since the tension introduced by suturing the surgical flap may itself apply a considerable downward force to the tooth, in the first few weeks. As the crown of the tooth responds to the force it rotates downwards, causing the incisal edge of the tooth to become labially prominent, outlined beneath the oral mucosa on the labial side of the alveolar ridge. At the same time, the root apex rotates forward towards the labial plate of bone. For the most part, these cases may be completed without the root apex ever protruding excessively in the labial sulcus. If the apex becomes prominent and further labial root movement is still desirable, this will necessitate a surgical

106  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 5.20  Tangential views of the completed alignment of a dilacerate tooth with root canal filling (a) prior to and (b) after apicoectomy and retrograde amalgam filling. (Courtesy of Professor I. Heling and Dr M. Morag.) This is the same case as in Figure 5.17.

intervention, performed with the aim of amputating the root apex of this tooth. The labially-directed portion of the root, corresponding to the post-traumatic developmental portion, is sectioned in a line which is continuous with the labial side of the main coronal portion of the root of the tooth. The pulp is extirpated and the root canal is obliterated using a combined conventional (coronal) and a surgical retrograde endodontic approach, wherever possible (Figure 5.20). Further extrusion and appropriate root torqueing of the incisor may necessitate a second rootshortening procedure, but, if the first procedure was delayed as late as possible and the root apex amputation was properly designed, this may usually be avoided. The degree by which the final prognosis of the shortrooted central incisor will be compromised depends largely on how much root remains after the amputation has been performed. The site of the amputation is entirely dependent on the location of the dilaceration and eliminates a majority of that portion of the root apical to it, which had developed after the traumatic episode. Thus, the closer the dilaceration is to the coronal portion of the root, the shorter will be the final root length at the completion of treatment and the poorer its prognosis. Crown dilaceration

Dilaceration may also occur in the crown portion of the tooth, although this is an extremely unusual sequel to trauma. In this eventuality, the tooth itself may be mildly labially displaced. When the crown is surgically exposed, an attachment is best placed on the labial surface, which is

almost certainly accessible. In this way, the continued downward-directed orthodontic traction will bring the root portion of the tooth from its more palatally displaced location close to its normal position and its long axis within normal limits. This will be due to the lingual tipping effect of the attachment on the labial surface. The tooth will erupt with the more incisal section of its crown labially tipped and the post-traumatic section in an acceptable angulation. Restorative treatment is indicated after grinding off that portion of the crown that represents the pre-trauma dental developmental portion. The future of the tooth will then be founded on the majority portion of the tooth, which developed subsequent to the traumatic episode. Root canal treatment may be required, and the ideal contour of the tooth restored using a crown and core restoration. If the dilaceration site is found to be very incisally placed, then a more modest composite material restoration may be used, with vitality maintained. In either case, the initial crown reconstruction that is placed should be made in a line continuous with the long axis of the root portion and an orthodontic bracket bonded to its appropriate mid-labial position, ready for finishing. Final root alignment, in both the labio-lingual and mesio-distal planes, is then achieved in the usual manner. Dilaceration of the coronal third of the root

The critical portion of the tooth for the dilaceration to occur is the coronal part of the root, close to the CEJ. In this situation, the prognosis of the aligned tooth is extremely

Maxillary Central Incisors  107  poor, since the majority of its root – that relating to the post-trauma period of development – will need to be amputated during the procedure, leaving the tooth with a non-viable coronal remnant of the root. Such a tooth will need to be extracted. Nevertheless, it will be necessary to reopen the space in the dental arch for some form of artificial replacement. Accordingly, and regardless of the prognosis, the same preparatory orthodontic procedure is still advisable. A modified Johnson’s twin-wire arch may be placed and space opened up as accurately as possible, to provide exactly the right amount of space, by comparing it with its erupted antimere. At this point, the dilacerate tooth should be exposed and, if its condition is confirmed as hopeless, it may be extracted – but not discarded! Instead, its contorted root is carefully severed from its perfectly shaped crown with a high-speed diamond burr, and the pulp chamber cleaned and filled with a composite filling material. The newly prepared natural crown may then be bonded to the two adjacent teeth, to act as its own space maintainer [38] until a more satisfactory permanent replacement may be made which, in view of the patient’s age, may not be for several years (Figure 5.21). Alternatively, and provided the apical portion of the root is substantial, it may be advantageous to treat it in the manner of a tooth whose root has been fractured below the level of the crest of the interproximal alveolar bone. To achieve this, it will be necessary to remove the crown of the tooth at the time of surgical exposure and perform an immediate root canal filling. A fixed, threaded post is prepared and a small hole is bored through its coronal end. The post is then firmly cemented. The cut root face and much of the coronal part of the post are covered with a composite filling material, leaving the tip of the post exposed. A stainless steel ligature wire is passed through the prepared hole and lightly twisted into a pigtail, with the help of artery forceps. In the absence of the acutely angled

(a)

crown portion, the remainder of the tooth presents a less complicated impaction, whose orthodontic resolution (socalled ‘forced eruption’ in perio-prosthesis parlance) is straightforward. The prepared tooth is erupted into the mouth until the post and the restoration covering the root surface become apparent at the gingival level. The orientation of the root of the tooth is then reassessed by palpation and by taking new radiographs – a periapical for the mesio-distal inclination and a tangential for the bucco-lingual relationship. The latter view will be considerably easier to discern than before, since the root canal filling will act as an excellent radioopaque marker for the root orientation despite the superimposition of other teeth. The patient may then be referred for any necessary and appropriate muco-gingival surgery by a competent periodontist, followed by the construction of a good quality temporary acrylic crown, which is placed over the existing post. A general dentist or a specialist prosthodontist is familiar with the need for ‘correcting’ an abnormal root orientation by constructing the artificial crown in line with the crowns of the adjacent teeth, regardless of the root axis. This may be a sensible compromise in the more minor non-impacted displacement cases, since orthodontic root movement may then be avoided. However, in dilaceration cases, considerable root movement is needed and this is most suitably performed with the existing orthodontic appliance. For this to be made possible, the temporary crown must be placed in a proper axial relationship to the recently confirmed orientation of the root. The desired orientation of this intended reconstruction of the crown of the tooth will be at odds with the alignment of its neighbours, and this is not always an easy message to convey to the prosthodontist! Once the temporary artificial restoration is cemented securely in place, a bracket is placed in the usual manner. Crown alignment, root uprighting and root torqueing are then undertaken.

(b)

Fig. 5.21  (a) Precisely measured reopening of the space has been performed, using a removable appliance. (b) The prepared crown of the dilacerate central incisor, shown in Figure 5.4, is bonded between the etched interproximal surfaces of the adjacent teeth.

108  Orthodontic Treatment of Impacted Teeth It may be seen that the point beyond which a root amputation should be avoided is when less than one-third of the root will remain after treatment. Crown amputation may be used as a viable alternative up to that point, but it must be remembered that the remaining root portion, which may be as little as one-half to two-thirds its original length, will be narrower in both mesio-distal and buccolingual dimensions. Additionally, this root stump will need to be erupted to the point where its amputated surface is just subgingival, because this will become the margin or shoulder of the future post and crown restoration. The diameter of this stump will be considerably smaller than is normal for a central incisor, which means that the emergence profile of the restored tooth will markedly compromise the appearance. These considerations illustrate the difficulties that exist in the placement of a satisfactory crown. It is emphasized that, once the space in the arch has been gained and the time has come for surgical exposure, accurate diagnosis of the exact location of the dilaceration is critical if a valid decision is to be made. As pointed out earlier, this is not always possible from the radiographs, due to the superimposition of other unerupted teeth and neighbouring roots on the tangential view; the periapical view can contribute nothing in this respect. However, the use of cone beam volumetric CT can easily supply the needed answer [12]. If CT is unavailable and it is still impossible to locate the dilaceration, then an attachment should be placed on the lingual side of the tooth as before and the initial traction applied to bring the crown of the tooth occlusally. A decision to amputate the root portion of the tooth must in any case be delayed until the root is palpably bulging into the labial sulcus. At each subsequent visit, the sulcus should be carefully checked and any palpable change in the position of the root apex should be compared with the downward progress and eruption status of the crown and its angulation. Progress radiographs should be taken at appropriate stages, until the exact location of the dilaceration can be pinpointed or otherwise clinically diagnosed, particularly in relation to the long axes of the two parts of the tooth. Once the accurate diagnosis has been established, a reassessment of the treatment approach should be made to decide whether the line of treatment is indeed appropriate or whether the crown portion should be amputated and the direction of traction altered accordingly.

References   1.  Kjaer I, Becktor KB, Lisson J, Gormsen C, Russell BG. Face, palate, and craniofacial morphology in patients with a solitary median maxillary central incisor. Eur J Orthod 2001; 23: 63–73.   2.  Howard RD. The unerupted incisor. Dent Pract Dent Rec 1967; 17: 332–342.   3.  Brin I, Zilberman Y, Azaz B. The unerupted maxillary central incisor: review of its etiology and treatment. J Dent Child 1982; 43: 352–356.

  4.  Zilberman Y, Malron M, Shteyer A. Assessment of 100 children in Jerusalem with supernumerary teeth in the premaxillary region. J Dent Child 1992; 59: 44–47.   5.  Brook AH. Dental anomalies of number, form and size: their prevalence in British schoolchildren. J Int Assoc Dent Child 1974; 5: 37–53.   6.  Tay F, Pang A, Yuen S. Unerupted maxillary anterior supernumerary teeth: report of 204 cases. J Dent Child 1984; 51: 289–294.   7.  Di Biase DD. The effects of variations in tooth morphology and position on eruption. Dent Pract Dent Rec 1971; 22: 95–108.   8.  Andreasen JO, Andreasen FM. Textbook and Color Atlas of Traumatic Injuries to the Teeth. Copenhagen: Munksgaard, 1994.   9.  Howe GL. Minor Oral Surgery, 2nd edn. Bristol: Wright, 1971: 135–137. 10.  Stewart DJ. Dilacerate unerupted maxillary central incisors. Br Dent J 1978; 145: 229–233. 11.  Seward GR. Radiology in general dental practice. IX-unerupted maxillary canines, central incisors and supernumeraries. Br Dent J 1968; 115: 85–91. 12.  Chaushu S, Chaushu G, Becker A. The role of digital volume tomography in the imaging of impacted teeth. World J Orthod 2004; 5: 120–132. 13.  Chaushu S, Zilberman Y, Becker A. Maxillary incisor impaction and its relationship to canine displacement. Am J Orthod Dentofacial Orthop 2003; 124: 144–150. 14.  Battagel J. The case for early assessment: 2: treatment with specialist support. Dent Update 1985; 12: 293–298. 15.  Houston WJB, Tulley WJ. A Textbook of Orthodontics. Bristol: Wright, 1986: 126–131. 16.  Mills JRE. Principles and Practice of Orthodontics, 2nd edn. Edinburgh: Churchill Livingstone, 1987. 17.  Mitchell L, Bennett TG. Supernumerary teeth causing delayed eruption – a retrospective study. Br J Orthod 1992; 19: 41–46. 18.  Witsenberg B, Boering G. Eruption of impacted permanent upper incisor teeth after removal of supernumerary teeth. J Oral Surg 1981; 10: 423–431. 19.  Ashkenazi M, Greenberg BP, Chodik G, Rakocz M. Postoperative prognosis of unerupted teeth after removal of supernumerary teeth or odontomas Am J Orthod Dentofac Orthop 2007; 131: 614–619. 20.  Bodenham RS. The treatment and prognosis of unerupted maxillary incisors, associated with the presence of supernumerary teeth. Br Dent J 1967; 123: 173–177. 21.  Munns D. Unerupted incisors. Br J Orthod 1981; 8: 39–42. 22.  Gardiner JH. Supernumerary teeth. Dent Pract Dent Rec 1961; 12: 63–73. 23.  Day RCB. Supernumerary teeth in the premaxillary region. Br Dent J 1964; 116: 304–308. 24.  Kettle MA. Unerupted upper incisors. Trans Eur Orthod Soc 1958; 34: 388–395. 25.  Hotz R. Orthodontia in Everyday Practice. Berne: Huber, 1961. 26.  Becker A, Kohavi D, Zilberman Y. Periodontal status following the alignment of palatally impacted canine teeth. Am J Orthod 1983; 84: 332–336. 27.  Kohavi D, Becker A, Zilberman Y. Surgical exposure, orthodontic movement and final tooth position as factors in periodontal breakdown of treated palatally impacted canines. Am J Orthod 1984; v85: 72–77. 28.  Johnson JE. A new orthodontic mechanism: the twin wire alignment appliance. Int J Orthod 1934; 20: 946–963. 29.  Shepard ES. Technique and Treatment with the Twin-wire Appliance. St Louis, MO: CV Mosby, 1961. 30.  Peretz B, Becker A, Chosak A. The repositioning of a traumaticallyintruded mature root permanent incisor with a removable appliance. Journal of Pedodontics, 1982. 31.  Chaushu S, Becker T, Becker A. Duration and Success Rate of Orthodontic Treatment for Impacted Maxillary Central Incisors 2010, unpublished. 32.  Ingber SJ. Forced eruption. Part I. A method of treating isolated one and two wall infrabony osseous defects – rationale and case report. J Periodontol 1974; 45: 199–206. 33.  Ingber SJ. Forced eruption. Part II. A method of treating nonrestorable teeth – periodontal and restorative considerations. J Periodontol 1976; 47: 203–216.

Maxillary Central Incisors  109  34.  Stern N, Becker A. Forced eruption: biological and clinical considerations. J Oral Rehabil 1980; 7: 395–402. 35.  Melsen B. Tissue reaction following application of extrusive and intrusive forces to teeth in adult monkeys. Am J Orthod 1986; 89: 469–475. 36.  Bimstein E, Becker A. Malocclusion, periodontal health and orthodontic intervention. In Bimstein E, Needleman HL, Karimbux N, van

Dyke TE, eds. Periodontal Health and Diseases in Children Adolescents and Young Adults. London: Martin Dunitz, 2001: 251–274. 37.  Boyer DB, Williams VD, Thayer KE, Denehey GE, Diaz-Arnold AM. Analysis of debond rates of resin-bonded prostheses. J Dent Res 1993; 72: 1244–1248. 38.  Becker A, Stern N, Zelcer Z. Utilization of a dilacerated incisor tooth as its own space maintainer. J Dent 1976; 4: 263–264.

6 Palatally Impacted Canines

Prevalence

111

Aetiology

111

Complications of the untreated impacted canine

123

Diagnosis

125

Treatment timing

127

General principles of mechano-therapy

133

The need for classification of the palatal canine

136

A classification of palatally impacted canines

139

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

Palatally Impacted Canines  111 

Prevalence

Aetiology

In any population, the prevalence of palatally impacted maxillary canines is low, but it seems to have a variable distribution with regard to ethnic origin. The lowest frequency reported in the literature relates to Japan [1], where the anomaly occurred in only 0.27% of the sample population. Some very early studies by Cramer [2] among white Americans and Mead [3] in an undefined sample found 1.4% and 1.57%, respectively. A study of a large series of full mouth dental radiographs among patients in the USA revealed a figure of 0.92% [4], while Brin et al. [5], in a study of an Israeli population, found a 1.5% prevalence. Higher figures for the anomaly have been found in more recent surveys: 1.8% was reported in the study by Thilander and Jacobson [6] of an Icelandic population, and 2.4% in an Italian sample [7]. Montelius [8] was the first to indicate a difference between Caucasian and Oriental populations, finding a frequency of 1.7% for Chinese and 5.9% for Caucasians. However, since he did not distinguish between buccal and palatal impaction in his study, little useful information may be gleaned from these figures in the immediate context. More recently, the work of Oliver et al. [9] indirectly indicated that Asians may suffer from buccally impacted canines more frequently than from palatal canines. While this appears to be supported by various case reports that have appeared in the literature from the Far East, no definitive study has been undertaken to investigate this possibility. A strong prevalence of impacted canines is found among females, with a ratio of 2.3:1 in the above-mentioned group of American patients [4]. 2.5:1 in an Israeli orthodontic group [10] and 3:1 in each of a Welsh orthodontic group [9], a US orthodontic sample [11] and an Italian sample [7]. However, some confusion exists with regard to these figures, since a subsequent random Israeli population study [5] showed an approximately equal male–female occurrence of the anomaly. Furthermore, Oliver et al. [9] indicated that, although a higher female incidence was present in their study of Welsh patients, this reflected the trend for more females to seek orthodontic treatment in the UK. Appearance is rarely marred by the presence of an overretained deciduous canine, since there is a complete and uninterrupted display of teeth, and any abnormalities are usually not disfiguring. That being the case, and if we are to accept an ‘appearance/aesthetics’ motivation for girls seeking treatment more frequently than boys, then the diagnosis of an impacted maxillary canine alone does not seem to be an adequate reason for the preponderance of females seeking treatment. Motivation for treatment may therefore rather depend on the ability and persuasiveness of a particular practitioner in pointing out the potential hazards of non-treatment. There may be no basis to expect that this would convince more female patients than males to accept treatment.

There is no single cause for the palatal displacement of the maxillary canine tooth. Space-occupying, extraneous entities of dental origin (Figure 6.1) will undoubtedly produce abnormal positioning of an unerupted permanent maxillary canine, but they are comparatively rare in the canine area. The fact that the majority of impacted canines occur in their absence compels us to look elsewhere for the main causes of impaction. Nevertheless, when a supernumerary tooth (Figure 6.1a) or an odontome (Figure 6.1b) appears in the area, they disturb the position and orientation of a developing canine tooth and deflect the eruptive force to express itself in a futile direction. Their timely removal may sometimes bring about spontaneous re-orientation and resolution, although this is by no means certain and active orthodontic intervention is usually necessary in the final instance. One other factor may be found in the context of premolar root morphology. An example of this is seen in Figure 6.1c, d, in which the buccal and/or palatal roots or a fused single root develops directly in the path of the unerupted canine. The canine may then become impacted, deflected or halted, but the physical presence of the canine may act as an impediment in the way of the developing root end, which may also serve to cause a mesial curving of the interfering root. In order to resolve this impaction, the premolar root may be uprighted distally and rotated mesially, with a modicum of palatal root torque, thereby moving its root apex distally and palatally to distance it from the canine. The canine may then be exposed and mechanically erupted in the usual manner and into its ideal position. Finally, the premolar should be returned to its upright position and re-rotated as much as possible, using light force, and the effort should be discontinued immediately it meets with resistance that will be caused by contact between the mesially curved premolar root end and the canine root. Other treatment options include: 1. Root treating and apicoectomizing the premolar and extracting the deciduous canine, which should all be done at the same time as exposure of the canine. 2. Extracting the canine and leaving the short rooted deciduous canine in place. 3. Extracting the premolar and the deciduous canine, which is an approach to be considered if the overall malocclusion may be treatment planned as a 2- or 4-unit extraction case. To return to the more usual forms and to explain the mechanism of palatal displacement of the maxillary canine, some of the hypotheses that have been put forward have been intimately involved with aberration in the normal process by which the maxillary anterior teeth erupt. For this reason, an understanding of normal development in this area is important.

112  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Permanent canine

Fused roots of premolar Deciduous canine

(c)

(d)

Fig. 6.1  (a) Anterior occlusal view shows an impacted canine, an odontome and a missing lateral incisor. (b) Periapical view of impacted canine and first premolar associated with an odontome and over-retained deciduous first molar. (c, d) A three-dimensional CBCT view showing the apical third of the root of a normally sited first premolar to be turned 90° to the mesial, directly in the path of the unerupted canine, which is being deflected further mesially and prevented from erupting. The transaxial (vertical) CBCT slice across the canine in the area of the CEJ and longitudinally through the deciduous canine. It also cuts across the mesio-distally oriented horizontal portion of the root close to the apex of the premolar. (Courtesy of Dr N. Dykstein.)

Normal development In the middle period of the deciduous dentition, a periapical radiograph of the premaxillary region will show the fully completed deciduous incisor roots. It will show the overlapping shadows of the permanent central and lateral incisors more or less in the same vertical plane (Figure 6.2a) and at the level of the apical area of the roots of the deciduous incisors, with the canines being sited higher up. The overlap of the permanent teeth crowns is due to the fact that these relatively wide permanent teeth are all contained in a narrow

area and, at this time, are initially located palatally in the alveolus. The developmental position of the lateral incisors is palatal in relation to both the central incisors and the permanent canines. For these reasons, the periapical view described above gives the appearance of severe crowding. During the early eruptive movements of the central incisors, a progressive resorption of the roots of the deciduous incisors occurs. The permanent incisors migrate slowly across from the palatal side of the arch to the labial as they proceed in their downward path, until the teeth erupt into

Palatally Impacted Canines  113 

(a)

(b)

(c) Fig. 6.2  (a) A periapical view of maxillary permanent incisors, at age 3 years. Note the degree of overlap of unerupted permanent central and lateral incisors. (b) The same patient at 5 years. The permanent central incisors have migrated inferiorly and labially relative to the lateral incisors. Note the reduced degree of incisor overlap. (c) The central incisors are erupting at age 6.5 years. Note how the lateral incisors have migrated labially into the arch to eliminate the overlap completely. (Courtesy of Professor B Peretz.)

a more labial perimeter than was defined by the deciduous incisor teeth before their shedding. During this process, the wide crown portion of the central incisors will have moved downwards and labially, ahead of the lateral incisors (Figure 6.2b). As this occurs, the progressively narrower cemento-

enamel junction (CEJ) area and the root portion of the central incisor come to lie mesial to the unerupted lateral incisor crowns. This leads to the fairly rapid provision of space at this level in the alveolus [12]. The lateral incisor migrates labially into this area as it begins its downward

114  Orthodontic Treatment of Impacted Teeth

The Ugly Duckling Stage

(a)

Final Anterior Alignment

(b)

Fig. 6.3  (a) In the early stages the unerupted canines are mesially directed, restricting the incisor roots to the area of the midline, thereby flaring their crowns distally, to create spacing. (b) As the canines descend towards the crown, down the distal aspects of the lateral incisor roots, their influence is reversed. They now apply a mesially directed force on the distal surfaces of the lateral incisor crowns, which closes off the anterior spaces and encourages a distal root flaring.

eruption path. Additionally, the downward eruption movement distances it from the permanent canine crown, providing more space for it to move labially, following closely after the central incisor. With the eruption of the central incisors, the lateral incisor crowns move from a lingual relationship into a direct distal relationship with the central incisor roots, initially at a higher level (Figure 6.2c). As this occurs, the presence of the lateral incisor crowns displaces the developing roots of the central incisors towards one another, since these are at the same level within the alveolar bone. With the central incisor apices held together in this way, the crowns of these teeth are flared distally. A developmentally normal median diastema is thus produced, which has been termed the ‘ugly duckling’ [13]. A year or so later, the lateral incisors will have descended along the distal side of the central incisor roots, to release their ‘hold’ on the narrowed inter-radicular width of the central incisor roots, allowing the roots to drift apart. The lateral incisors continue to move inferiorly along their eruptive path, progressively reducing their constricting influence on the central incisor roots until they reach the distal side of the necks of the central incisor crowns. At this point, their presence and continued downward migration serve to provide a mesially directed force to the crowns of these teeth, moving them towards one another and partially closing off the median diastema. The long axes of the central incisor teeth will also have changed, with the roots becoming more parallel. The lateral incisor long axes, however, are relatively flared in the coronal direction, with their root apices close to those of the central incisors. A periapical view of the area at this time will show the unerupted permanent canine crowns of each side pointing mesially towards the lateral incisor apical area. They appear

to be the containing influence that causes the apical convergence of the incisor roots and the reason that the median diastema has not completely closed. Subsequent follow-up radiographs of the area will show the permanent canines altering their relationship as they move downwards along the distal side of the root of the lateral incisors. Having initially constricted the roots of the lateral incisors mesially, the downward descent of the canines alters their influence on the lateral incisor crowns, to tip them mesially. This brings about an uprighting of the long axes of the incisors on each side and a closure of the anterior spacing (Figure 6.3). The canines’ own long axes become more vertical as they progress and as the roots of the deciduous canines become resorbed. With the shedding of the deciduous canines, they finally erupt with a slight mesial inclination, taking up their place in the arch by moving the crowns of the incisors towards the midline, to close off the diastema completely [14]. As all this occurs, the long axes of the incisor teeth change from being apically convergent to become more parallel and even slightly divergent. Throughout the period of their downward progress, the permanent canines are conspicuously palpable on the buccal side of the alveolar ridge, from as early as 2 or 3 years prior to their normal eruption, which normally occurs at the age of 11–13 years. Theories regarding the causes of palatal displacement Long path of eruption

From the days of Broadbent, in the 1940s, the most common reason given for palatal displacement of the permanent maxillary canine was the fact that it had a long and tortuous eruption path, beginning close to the floor of the orbit. It was considered that, compared with other permanent teeth,

Palatally Impacted Canines  115  this tooth had much further to travel before it erupted into the mouth and that it therefore had a greater chance of ‘losing its way’. This has been standard teaching for many decades. Crowding

Hitchin [15] considered that crowding of the dentition was the reason for this condition, although he offered no evidence to support his contention. In general, crowding of the dentition results in the exaggerated displacement of a tooth from its developmental position in the arch. The developmental position of the maxillary lateral incisor is lingual to the line of the arch, as we have described above. Thus, when crowding affects the early mixed dentition, there will be insufficient space for the lateral incisor to migrate labially between the root of the erupting or newly erupted central incisor and the deciduous canine teeth, which is the manner in which it normally comes into the dental arch. For the most part, therefore, it continues to develop downwards, but in a lingual position, and erupts lingual to the adjacent teeth. A parallel environment is created when a second deciduous maxillary molar is extracted before its due time and the first permanent molar drifts mesially into the available space. Similarly to the lateral incisor, the developing second premolar develops palatally to the line of the arch, and its continued development and eruptive path will be in an exaggerated palatal direction in much the same way. We have pointed out above that the normal eruption path of the permanent canine is buccal to the line of the arch, and we also know that the lateral incisor and first premolar, the teeth immediately adjacent to the canine, erupt before the canine. Thus, in the presence of crowding, there will be reduced space in the arch in the canine area and the close proximity of these adjacent teeth will prevent the canine from moving into the arch. The vertical development of the maxillary permanent canine will therefore be accompanied by its buccal displacement, to give the typical picture seen in the class 1 crowded case (Figure 6.4). Whether the tooth eventually erupts or remains impacted is irrelevant, although buccal impaction is uncommon in Caucasian population groups. It is therefore quite clear that

the cause of this type of displacement of the canine is completely different from that involved with palatal displacement. The two conditions are different entities. They should never be confused, nor should they be lumped together to form an experimental group for clinical research, as if to offer a homogeneous sample of impacted teeth. For the purposes of study, it is far more logical to combine all palatally displaced canines, whether they are unerupted or erupted, since they share a common aetiology, although their clinical presentation may be different. In a series of clinical research studies, Jacoby [16], Becker [17] and Brin et al. [5] pointed out that the likelihood of palatal displacement is much reduced where crowding is present. They have shown it to be a far more prevalent occurrence when there is excessive space in the dental arch. Non-resorption of the root of the deciduous canine

Lappin [18] considered that it is the failure of the root of the deciduous canine to resorb that causes a palatal deflection of the eruption path of the permanent canine, leading to its impaction. Here, too, one may draw a parallel with other teeth. In cases where a second deciduous molar is over-retained, owing to the presence of a malposed premolar tooth germ, one may often see on the periapical or panoramic radiograph that one of the roots has totally resorbed, while the second root is only partially so. The long spicule of unresorbed root that may be present retains the tooth against natural shedding, while the fully developed and unerupted second premolar is situated immediately beneath the crown of the deciduous tooth in the area previously occupied by the resorbed portion of the roots. From this type of clinical evidence, which is seen so widely and frequently in practice, it is generally considered that the presence and advancing eruption of the permanent tooth provides the stimulus for the resorption, and a portion of root distant from the unerupted permanent tooth may be unaffected by this process. On the basis of this, Lappin’s view would appear to be ‘putting the cart before the horse’. Nevertheless, and in support of his argument, subsequent studies [19–22] have shown the spontaneous eruption of previously impacted canines in many cases, following the extraction of deciduous canines. This will be discussed at length later in this chapter, under the heading ‘Preventive treatment and its timing’. Trauma

In a clinical report, Brin et al. [23] have illustrated how trauma, which leads to a cessation in the development of a lateral incisor root, may be associated with palatal canine impaction. They explain this by assuming:

Fig. 6.4  Buccally displaced maxillary canines due to a crowded arch.

traumatic episode may have caused movement • ofthatthethelateral incisor, or by conduction, movement of the unerupted canine • itself, or

116  Orthodontic Treatment of Impacted Teeth in terms of the guidance theory, that this could be • explained as being due to the shortness of the lateral incisor root, whose development ceased as a result of the trauma. Soft tissue pathology

A further alternative could place the blame on the possible presence of chronic irritation, residual infection or granuloma around the apex of a non-vital deciduous canine

(a)

tooth (Figure 6.5). Deciduous maxillary canines may often be affected by interproximal, usually distal, caries. The lesions are frequently left untreated in the belief that the teeth are about to be shed. The tooth loses its vitality when caries reaches the pulp and a chronic periapical area develops. This soft tissue lesion by itself is a potent cause for deflection of the path of a developing unerupted maxillary canine (Figure 6.6). In rare instances, it may develop into a radicular cyst or it may initiate cystic change in the follicle

(b)

Fig. 6.5  (a, b) Periapical views of bilaterally impacted canines, each associated with a non-vital deciduous canine.

(a)

(b)

Fig. 6.6  (a) Panoramic view of a patient in the mixed dentition stage with a markedly displaced and unerupted right maxillary canine. The immediate area shows a large area of bone loss involving the canine and first premolar, associated with the non-vital deciduous first molar. The chronic periapical abscess represents a soft tissue obstruction that has deflected the eruption path of the permanent canine. The deciduous canine has an obliterated pulp. (b) Following extraction of the deciduous canine and deciduous first molar, there has been spontaneous resolution, with eruption of the teeth. For no apparent reason, the deciduous canine of the opposite side was overlooked! (Courtesy of Dr A. Renert.)

Palatally Impacted Canines  117  of the canine, either of which will alter the path of eruption of the canine, or prevent its further eruptive progress. This will be discussed in Chapter 11. The guidance theory

Miller [24] and Bass [25] reported that there appeared to be an unusually high prevalence of congenitally missing lateral incisors associated with palatally impacted canine teeth. They theorized that, under these circumstances, the permanent canine lacks the guidance normally afforded by the distal aspect of the lateral incisor root. As pointed out earlier, in relation to normal development, the canine initially has a strong mesial developmental path, which alters early on, with the canine being guided downwards, apparently along the distal aspect of the lateral incisor root. They concluded that, in the absence of this guiding influence, the canine continues in its initial mesial and palatal path. The tooth then becomes impacted in the palatal area, posterior to the central incisors, and fails to erupt in its due time, if at all. Miller’s concept was founded on information gleaned from the study of six such cases. He assumed that since a peg-shaped or otherwise abnormally small lateral incisor develops a root of more or less normal length, such a tooth would provide the required guidance for the normal eruption of its adjacent canine. He therefore rationalized that these anomalous teeth could not be an aetiological factor in canine impaction. Following the treatment of several hundred cases of this type by the present author, a different pattern of association seemed apparent. Palatal impaction of the maxillary canine appeared to be intimately bound up with the occurrence of anomalous lateral incisors and less with the congenitally missing teeth. Furthermore, a stereotype of the maxillary impacted canine patient could be offered (Figure 6.7), in General population 4% small

2% peg

which the patient is frequently a 15-year-old female, with well-aligned and normally related dental arches, slight spacing and no real malocclusion. Characteristically, the teeth are small, the lateral incisors particularly so, the incisors lack their normal rounded contour, there may be missing teeth, dental development is late and the patient’s motivation for treatment is low. A series of clinical research studies followed, in which a sample of patients who were successfully treated for a palatally displaced canine was investigated. In the first study [10] a wide and highly significant discrepancy in the numbers of normal, small and peg-shaped lateral incisors adjacent to an affected canine was found, compared with the published data for normal populations (Figure 6.8). In the interests of accuracy, a random study was later performed by the same research group [5] to quantify the various types of lateral incisors found within the general population of the same geographic area, while using the same definitions of anomaly. In the general population, 93% of all lateral incisor teeth were of normal shape and size, compared with only

Fig. 6.7  Late-developing dentition showing spacing, small peg-shaped lateral incisors, teeth of poor anatomic contour and minor class 1 malocclusion.

PDC population

1.8% missing 5.5% missing 17% peg

93% normal

25% small

Fig. 6.8  Lateral incisor anomaly in patients with palatally displaced canines. From ref. [5], with permission.

52.5% normal

118  Orthodontic Treatment of Impacted Teeth 52% in the palatal canine sample. In the random population sample, missing lateral incisors were found in approximately 1.8% of the cases [26], which contrasted markedly with the 5.5% of this anomaly among the impacted canine cases [10] or three times as frequent (Figure 6.8). These figures are valid for the Israeli population sample studied. However, congenital absence of maxillary lateral incisors in a meta-analysis of the collected data from a large number of different population studies was found to be lower, at 1.55% for males and 1.78% for females [27]. These results clearly support Miller and Bass regarding the part played by the lateral incisor as a guide in the normal eruption of the permanent canine. Without this guidance, normal eruption is compromised fivefold. However, Miller’s rationalization regarding the positive role of anomalous lateral incisors appears very much misplaced. Small lateral incisors were seen in only 4% of the random sample, while the palatal canine cases showed this anomaly to be six times as frequent (25%). Furthermore, only 2% of the general population had peg-shaped incisors, while 17% (nine times the frequency) were seen among the palatal canine cases. Similar results have since been shown in confirmatory studies that have examined Welsh [9] and west of Scotland [28] samples. If small or peg-shaped lateral incisors provide similar conditions to normally shaped lateral incisors in their role in the normal eruption of the canines, then one would expect figures for the association of these anomalous teeth with palatal canines to be much lower than the 5.5% figure for missing lateral incisors. Their presence is shown here to offer more than merely a loss of guidance to the developing permanent canine. The fact that they are associated with a greater prevalence of impaction compared to that of the missing lateral suggests that an additional, obstructive role is played by these teeth. In the first study [10] a hypothesis was presented based on the fact that the anomalous small and peg-shaped lateral incisors develop very much later than normal lateral incisors. While no figures are available for the extent of this delay, it seems clear from clinical observation that it may be as much as three years – and this for teeth whose calcification normally begins at age 10–12 months! If we are now to relate this to the ‘guidance theory of impaction’, we may postulate that at the critical time that the permanent canine requires the guidance, the root of the anomalous lateral incisor is too rudimentarily developed to provide it. Thus, initially the situation is parallel to that seen in congenital lateral incisor absence. The result is that the canine develops mesially and palatally and usually in a downwards direction, into the vertical alveolar process, where it proceeds towards the palatal periosteum. This describes the first stage of palatal displacement. The palatal periosteum may then halt further progress of the tooth, or it may alter the eruption path to a more horizontal direction, across the palate. In either instance, this may then be defined as a first-stage palatal impaction.

In particular circumstances, it seems that the palatal periosteum may deflect the developing canine from its first-stage displacement, in a downward direction. The alveolar process in the canine region is V-shaped in crosssection, such that, with continued vertical movement, the progressively narrowing alveolus will tend to guide the aberrant canine in a buccal/labial direction. These corrective movements of the palatally displaced canine are the characteristic feature of what may be termed the first stage of palatal displacement with secondary correction (Figure 6.9). In cases of congenital absence of the lateral incisor, a canine that was not palpable buccally at any point in its earlier development may often be seen to finally erupt more mesially than normal and in the line of the arch. In the presence of an over-retained deciduous lateral incisor or canine only, the corrective movements of the canine lead to the initiation of root resorption of these deciduous teeth. Following their shedding, the permanent canine may then erupt into the line of the arch and, often, in a more mesial location in the place of the absent lateral incisor. If a latedeveloping lateral incisor is present, it will now lie directly in the path of the displaced canine. The physical presence of the lateral incisor will bring an abrupt stop to these corrective movements, and any further vertical development of the canine may only then be on the palatal side of the dental arch, completing the second stage of palatal displacement. In summary, therefore, the ‘guidance theory’ comprises five elements: 1. Normal eruption. It adopts Broadbent’s original view that, given the timely and normal development of a lateral incisor, guidance for the canine is provided by the presence of a normally developing lateral incisor and a buccal path of eruption is to be expected, with the tooth palpable in the buccal sulcus early on. 2. First-stage impaction. It offers an explanation for the absence of guidance at a critical time in the normal development of the permanent canine, which leads to a deflection of the developmental path of the tooth, causing it to move palatally. This etiologic factor may be created by a congenitally missing lateral incisor or by a late-developing, anomalous lateral incisor. In the event that no vertical movement of the canine into the alveolar process occurs, the result may be a horizontal palatal impaction. 3. First-stage impaction with secondary correction. It goes on to explain the corrective influence of the vertical alveolar process, which redirects the canine on a more favourable downward path. This scenario may be difficult to diagnose accurately, and the clinician must draw his or her own conclusions from the further progress of the impacted tooth, which may be palpable, low down on the palatal side, before it finally erupts close to the line of the arch. The tooth may then spontaneously

Palatally Impacted Canines  119 

(a)

(b)

(c)

(d)

Fig. 6.9  (a–c) Serial radiographs showing the relationship of an unerupted canine to a late-developing and peg-shaped lateral incisor. (d) The two teeth have erupted and are superimposed on one another. At clinical examination the erupted canine was found to be on the palatal side of the lateral incisor.

120  Orthodontic Treatment of Impacted Teeth

Heredity

favourable to the development of palatally displaced canines and, as was to be expected, the lateral incisor phenomena were found to occur in an unusually high proportion of these cases. The view that these phenomena are each genetically determined and frequently occur together, including the canine displacement [30–32], is equally tenable, but would appear to be an oversimplification. The fact that the extraction of adjacent deciduous canines and anomalous lateral incisors and orthodontic space opening greatly improve the chances of canine eruption would lead us to believe that local factors cannot be ignored as exerting a powerful influence on the aetiology of canine impaction. Other forms of maxillary canine positional anomaly do occur from time to time, and are difficult to equate with the more usual pattern of palatal or buccal displacement. Genetic factors seem likely to be the governing factors, in which the entire tooth is located in an abnormal position. In these cases, it seems that the original site or orientation of the anlage from which the tooth developed was abnormal. Thus, we occasionally come across patients in whom there is adequate space in the arch for the ideal eruption and alignment of the maxillary permanent canines, yet these teeth erupt buccally ectopic (Figures 6.10 and 6.11). Additionally, the eruption occurs relatively high in the alveolus and the tooth has no mesio-distal contact with its immediate neighbours and, therefore, cannot be considered to have been guided into this position. On the other hand, this may be looked at and perhaps explained in the parlance and context of the guidance theory. As we have illustrated above, buccally displaced canines (BDC) are usually found in crowded dentitions. Nevertheless, there is a small but significant percentage of BDC cases where there is no crowding to account for the buccal displacement. A study was undertaken by the Jerusalem group to investigate the features of dentitions of BDC cases where no crowding was present and compared them with BDC cases with crowding and cases in which the canines had erupted normally. The results revealed reduced dimensions of the maxillary incisors in BDC in dentitions

Given the strong hereditary influence in palatal canine displacement, there are those who believe that heredity is the direct cause and dismiss other relationships as secondary or as similarly linked hereditary factors. In other words, the palatal canine is another link in the chain of genetically linked phenomena. In a study of the families of children affected by palatally displaced maxillary canines [29] a search was made among the parents and the siblings for the related anomalies to which we have referred above. The prevalence of small, peg-shaped and missing lateral incisors, late-developing dentitions and other missing teeth among these close relatives was very high, in addition to palatally impacted canines. This evidence seems to favour heredity as the causal agent for these associated phenomena. The guidance theory contends that their presence creates an environment

Fig. 6.10  Maxillary canine/first premolar transposition. An example of hereditary primary tooth germ displacement.

move more buccally and mesially, in the absence of a lateral incisor, to reach the occlusal plane in a close-tonormal bucco-lingual position. 4. Second-stage impaction. Self-correction is prevented by the presence of an anomalous and late-developing lateral incisor, redeflecting the tooth further palatally. This may be termed second-stage displacement, and is an aetiological factor that is not seen when the lateral incisor is absent. 5. Second-stage impaction with secondary correction. As we shall see later, in the discussion of treatment timing, extraction of an over-retained deciduous canine, or even the anomalous lateral incisor itself, may often lead to spontaneous eruption of the impacted tooth. There are several elements in this process which clearly indicate that the erupting canine is strongly influenced in the progress of its eruptive movements by environmental conditions, which determine the degree of success of its final eruption status, including its final erupted location, or its impaction. Small, peg-shaped, and missing teeth are more frequent findings among females than among males, in the approximate ratio of 2–3:1, as discussed earlier in this chapter. Furthermore, the maxillary permanent canine erupts earlier in females, which could mean that earlier lateral incisor guidance will be necessary for its normal eruption. These facts provide the hypothesis with some support in explaining why palatal canines are more frequent in females and why anomalous lateral incisors are a more powerful causal agent than congenitally absent lateral incisors. It is quite clear that heredity plays an important role in this hypothesis. The assumption is that the genetically determined factors (small, peg-shaped, missing lateral incisors, spaced dentitions, etc.) provide the environment that leads to a loss of guidance of the canine, its abnormal palatal path, and impaction.

Palatally Impacted Canines  121 

Fig. 6.12  A case of bilateral hereditary primary tooth germ displacement. Fig. 6.11  Despite the absence of crowding, the canine has erupted in an abnormal location. Is this evidence of a lack of guidance on the part of the adjacent peg-shaped lateral incisor or hereditary primary tooth displacement?

in which no crowding existed in comparison to the other two groups. More specifically, the lateral incisor was the only tooth which was consistently smaller when compared to both crowded BDC and normally erupted canine cases [33]. As pointed out earlier in this chapter, small lateral incisors develop very late, growing adequate root length at a time which is too late for it to influence the developing canine. Thus, it may be reasonably postulated that the lack of guidance from the anomalous adjacent lateral incisor provides a cogent alternative explanation for the buccal displacement of the canines in non-crowded dentitions, in a similar way to what occurs in the palatally displaced canine cases. The canine simply takes a buccal path instead. It becomes clear from a careful reading of this section that there are both undeniable hereditary and environmental/ developmental factors at work in the aetiology of maxillary canine impaction, neither of which may be discounted and both influencing the expression of the aberrant eruption. For a balanced, updated, evaluative and critical discourse on the place of both these elements as causative agents, the reader is referred to a recently published review (34). Peck et al. [35] have studied maxillary permanent canine/ first premolar transposition (Figure 6.11), and have found a strong hereditary influence in its aetiology. They point out that this very specific type of canine anomaly cannot be construed as deriving from guidance from the lateral incisor, and cannot be influenced in any way by the size, form or timing of the development of that tooth. With somewhat questionable justification, they then extend their reasoning to cover all maxillary canine displacements. They go on to claim that their findings, specifically vis-à-vis transposed canines, represent conclusive evidence that the aetiology of palatal impaction is also under total genetic control (Figure 6.12). Canine/first premolar transposition and palatal displacement of the canine are both aberrations of tooth position, but there is no reason for assuming that the aetiology of the one is the same as for the other, and there can be no basis

for comparing transposition with palatal displacement. This does not, therefore, present a valid argument with which to refute the ‘guidance theory’ [36]. We may prefer to define canine/first premolar transposition as primary tooth germ displacement [37]. In other words, their site of development is not in its expected location in the jaw and in relation to the other teeth. In the developed dentition, this is reflected in an abnormal position of the root apex, which is usually assessed clinically by the mental exercise of extending the orientation of the long axis of the tooth crown. This helps us to distinguish them from other and more common forms of displacement, which have an environmentally influenced aetiology. As a result of crowding, the position of the more frequent buccally placed canine is dictated by the amount of space available for it in the arch and by direct interproximal contacts with the adjacent teeth. The vast majority of buccally and palatally displaced canines show the root apex to be ideally placed, in the line of the arch [36]. Experi­ ence shows that extrusion and tipping of the crown into its place in the arch is usually sufficient to resolve the malalignment, with little or no root torque being required in most cases. Other associated clinical features Repeated studies have found that palatal canine patients have dentitions characterized by their small teeth [5, 10, 16, 35, 36]. In the general population, the individual teeth of males are larger than those of females, but a study of patients with palatal canines discovered that the individual teeth in the affected males were found to be significantly smaller than in unaffected males [38]. However, there was no difference in the size of teeth between affected and unaffected females. Oddly, the teeth of affected males were similarly sized to those of affected and unaffected (control) groups of females. Both male and female patients with palatal canines often feature missing teeth, such as third molars, maxillary lateral

122  Orthodontic Treatment of Impacted Teeth incisors, mandibular and maxillary second premolars, and mandibular central incisors [5, 7, 24, 25, 30, 33, 34]. From the literature, we learn that small and missing teeth in a dentition have been shown to be associated with late development [39–41], a fact that has largely escaped attention. Scant notice was taken within the profession of the shrewd observation made by Newcomb half a century ago [41] that ‘with few exceptions . . . potential impaction of permanent teeth is seen in patients exhibiting moderate to severe retardation of dental maturation . . . [and] . . . a slow rate of permanent teeth formation’. He considered ‘it would be useful . . . to correlate dental and bone ages’ among these patients. Newcomb based his conclusions on dental age as determined by the eruption status of the dentition. However, no specific study was ever undertaken to investigate this connection until recently. In a more recent study that attempted to investigate this factor, the 55 cases with palatal canines which constituted the experimental group were assessed for dental age on the basis of the root development of the dentition, as seen on the radiographs and using the principles outlined in Chapter 1. This is a more accurate method of age assessment than eruption status, which may be influenced by local factors. In approximately half of the cases, development was seen to be in line with the norms for their ages, while in the remainder, significant developmental delay was seen. None of the affected cases showed advanced dental development, underlining the absence of a normal distribution for dental development and a strong tendency for lateness [42]. As seen in the discussion in relation to tooth size, a sexual dimorphism in the pattern of delayed dental development was found. A dental age significantly younger than the chronological age was noted among affected males more than twice as frequently than among affected females. In the males, late dental development was observed in half the individuals with palatal canines, which was accompanied by the presence of smaller than average teeth and a high frequency of lateral incisor anomaly. The other half of the males showed a timely developed dentition, a statistically non-significant increase in the incidence of lateral incisor anomaly, and mesio-distal width reduction only in the maxillary central incisors and first molars. This latter male sub-group therefore resembled the unaffected cases that made up the control group in this study. Among the females, late dental age was accompanied by a slight increase in lateral incisor anomaly, although overall tooth size was not affected. With such contrasting and partially conflicting findings regarding tooth size and retarded dental development seen in males and females who exhibit palatally displaced maxillary canines, investigations of tooth size, congenital absence and dental age which involve a combined male–female group of patients, will produce confusing results. This combination may obscure important differences that exist between the sexes.

Infra-occluded deciduous mandibular molars have also been found in larger numbers in cases with palatal canines [7, 42]. The explanation may be viewed from the same two distinct standpoints. The first assumes that the canine aberration is totally hereditary and is linked with the associated hereditary factors of lateral incisor anomaly, late dental development, small and missing teeth – to which it is now proposed to add infra-occluded deciduous molars as an additional hereditary factor. The alternative standpoint notes that over-retained and infra-occluded deciduous molars are often found in situations where their permanent successors are small or congenitally absent. In both these situations, resorption of the roots of the deciduous molars may be partial, sometimes involving only one of the widely divergent roots. This results in over-retention of the deciduous molar and, under these circumstances, it is more likely to become infra-occluded than one that sheds normally and in its due time. Dentitions with small or missing premolars are often associated with lateral incisor anomalies, which have been shown to be allied with palatal canines, as we have discussed earlier in this chapter. Thus, the association between infra-occluded mandibular molars and palatal canines is an indirect one, with linked hereditary factors bringing about changes elsewhere, which generate the guidance factor that causes the canine aberration. There are more compelling arguments that seem to favour the guidance theory. For around half a century, it has been accepted that small and peg-shaped incisors represent a weak or partial expression (incomplete penetrance or microform) of congenital absence [43–48]. It follows, therefore, that if palatal displacement of a maxillary canine is under hereditary control, then one would expect to see this form of ectopia more frequently associated with congenital absence of the adjacent lateral incisor than with a lateral incisor of reduced size. Not only does this not occur, but the reverse appears to be true, with a significantly higher proportion of palatal canines involved with lateral incisors of reduced size [9, 10, 28, 36, 42]. In order to confirm or negate this reported tendency and to provide a firm scientific base for this apparent paradox, a study was designed in which the sample consisted of patients who were taken serially from the files of the Orthodontic Departments in the Universities of Jerusalem and Tel Aviv and in orthodontic private practice in Israel [49]. From a patient base of approximately 12 000 consecutively treated patients, only those exhibiting an anterior maxilla with the following pre-treatment conditions: lateral incisor on one side • aanmissing anomalous (i.e. peg-shaped or reduced) lateral incisor • on the other, and • a unilateral palatally displaced canine were included in the study. Given such rigorous inclusion criteria, 19 patients remained to form the experimental group. The null hypothesis of the investigation was that if:

Palatally Impacted Canines  123  (a) reduced or peg-shaped lateral incisors are hereditary and represent a microform/incomplete penetrance/partial expression of congenital absence and (b) palatal displacement of maxillary canines is a hereditary condition and associated with the lateral incisor anomaly, then it is logical to assume that the palatally displaced canine will occur far more frequently in association with congenital absence of the lateral incisor than with the dimensionally diminutive tooth. Not only was this not so, but the results of the study showed that in an overwhelming majority of the cases (84%), the palatal canine was found on the side of the anomalous lateral incisor, with only three cases (16%) found on the side of the missing tooth. From this, it was concluded that environmental factors are strongly bound up with the causation of palatal displacement of the maxillary canine and explained in terms of a second stage impaction, as described above. In the previous chapter, relating to impacted maxillary incisors, we pointed out that an early first phase of treatment is indicated in order to resolve the impaction of the affected tooth. In the long-term follow-up of many of these maxillary incisor impaction cases, it was observed that there seemed to be a substantial number of patients in whom there was a serious disturbance in the eruption of the canine of the same side. Accordingly, a study was undertaken to monitor the further development of children who had been treated for maxillary incisor impaction in the months and years following the resolution of the impaction in their first phase of treatment. Abnormality of position and disturbance of eruption were seen in the canine on the same side as the previously impacted central incisor in 43% of the cases. This was in contrast to the contralateral canine, where the rate of anomaly was only 4.7%. The abnormality in the affected side canine was expressed in several different ways, namely palatal impaction, buccal ectopia and pseudotransposition with the lateral incisor [50]. The frequent occurrence of canine aberration only on the side where the central incisor had been impacted indicates clear environmental influence (see Figure 6.20). In a radiographic study [51] of a series of 122 Israeli patients with multiple congenitally missing teeth, 20.4% of the maxillary canines were congenitally absent and 42.4% were mesially displaced, of which 5.7% became impacted and mostly adjacent to a missing lateral incisor. Of the remainder, 5.6% were distally displaced and only 26.4% were positioned in their correct locations, mainly adjacent to a lateral incisor. It was concluded that displaced and impacted maxillary canines were very frequently found in this highly special group of patients, although inadequate sample size prevented the drawing of meaningful conclusions. In summary, it may be learned from all this that the causation of palatal displacement or impaction of the maxillary canine is not due to any single factor. The simultaneously occurring factors related to or causing the canine impaction may be hereditary in nature, such as anomalous

or missing lateral incisors, late dentitions and infraoccluded deciduous molars, which themselves are under total genetic control. Equally, however, the path of eruption of the canine may be influenced both favourably and unfavourably by conditions and events that are environmental in nature and include local therapeutic countermeasures, such as orthodontic space opening, prophylactic extraction of the deciduous canine or of a minuscule lateral incisor, or the existence and/or treatment of an adjacent impacted central incisor, or due to a soft tissue lesion or hard tissue body. So, while the aetiological stage may be set by either genetic or environmental factors, there is strong evidence that casts doubt on the simplistic and dogmatic view that the palatal canine itself is solely under genetic control. Unquestionably, maxillary canine eruption is influenced by and responds to altered conditions within its immediate environment. At the time of writing, therefore, ‘there is currently too little robust statistical or genetic evidence to definitively ascribe malposition of the permanent canine as an isolated disorder of either genetics or environment’ [49, 50].

Complications of the untreated impacted canine Morbidity of the deciduous canine Early morbidity of the deciduous canine is common for two reasons. First, its root may become markedly resorbed, even when its unerupted successor is quite distant from it, causing considerable mobility and eventual shedding without the possibility of replacement by the permanent tooth. This creates a problem in terms of restoration, since the space is usually too small for a satisfactory replacement either by the misplaced permanent canine or by some form of artificial fixed bridge pontic or implant. The second reason that such a tooth may not survive relates to its relatively high susceptibility to interproximal (particularly distal) caries. As we have pointed out, it is still common to see a fairly extensive distal cavity in this tooth at around the age of 11 or 12 onwards, which may have been deliberately left untreated by a general practitioner who was unaware of the likelihood or existence of impaction of its permanent successor. Cystic change Loss of vitality may occur very early on in the carious process in the deciduous canine teeth, owing to the narrow width of the hard structures of these teeth and the relatively large pulp. Necrosis of the pulp and periapical pathology may then be asymptomatic. Under these circumstances, there may be a direct interconnection between the apical pathology and the follicular sac surrounding the impacted canine. This may stimulate an enlargement of the follicular sac, which is clearly seen on a periapical radiograph. It may also undergo cystic change, to produce a dentigerous cyst

124  Orthodontic Treatment of Impacted Teeth

Fig. 6.13  A dentigerous cyst surrounds the crown of an impacted canine.

(Figure 6.13). This may also occur without any relation to pathosis of the deciduous canine. In strictly radiological terms, an enlargement of the follicular sac to beyond 2 or 3 mm is generally considered to represent cystic change. In rare cases, these cysts may expand at the expense of surrounding maxillary bone and displace the canine higher and higher in the maxilla. Alternatively, the chronic periapical lesion on the deciduous canine may itself become cystic – a radicular cyst – and its subsequent enlargement may displace the adjacent teeth, including the palatal canine. The subject of cysts in relation to impacted teeth will be described separately in Chapter 11. Crown resorption The reduced enamel epithelium surrounding the completed crown of a tooth separates the crown of the tooth from the surrounding tissues. This intact epithelial covering may degenerate with age if the tooth remains unerupted, and its integrity may be lost. This allows bone and connective tissue to come into direct contact with the crown of the tooth. In time, osteoclastic activity will lead to resorption of the enamel and its replacement by bone – a process known as replacement resorption. Over a long period, repeated radiographs of the tooth will show a poorer definition of the profile of the crown, with the enamel becoming less and less contrasting in its opacity, highlighting this bone-for-enamel substitution (Figure 6.14). Subsequent surgical exposure of the crown of this tooth will show a

Fig. 6.14  Periapical view of maxillary incisor area in a 63-year-old female, showing advanced replacement resorption of the crowns of two impacted canines. The follicles of both teeth are almost completely absent and the teeth are very radiolucent, with poor definition.

pitted surface, which is difficult to separate from the surrounding bone, and sparse soft tissues. This condition seems more likely to occur in adult patients in whom the impaction has been left untreated over two or three decades [52] and is almost certainly the reason why, when attempting treatment of impacted teeth in adults in the fourth or fifth decade of life, the chances that the tooth will not respond to orthodontic force may be high [53]. Resorption of the roots of the incisors The proximity of the follicular sac of an unerupted permanent tooth to the roots of its deciduous predecessor appears to be the trigger that initiates the process of root resorption, probably as the result of pressure. The progress of this resorption process is then maintained by the further advance of the eruption of the permanent tooth, which moves into new areas vacated by the resorbing root. This is part of the normal process of transition from the deciduous to the permanent dentition. Little is known about the reasons for the resorption of the roots of deciduous teeth that leads to their eventual

Palatally Impacted Canines  125  other permanent teeth. However, in rare instances an aberrant and deeply located second premolar may cause the resorption of the mesial root of the first molar (see Figure 7.2). The central incisors and first molars erupt before their adjacent neighbours, and the lateral incisor is related to the neck area of the crown of the central incisor. The canine, however, is closely related to the roots of the adjacent lateral incisor and first premolar, while it is still fairly high in the maxilla during most of its eruption period. Similarly, unerupted third molars in crowded positions in the ramus or tuberosity areas may come into close relation with the root portion of the second molars, where similar damage may occur.

Diagnosis Unerupted permanent maxillary canines cause the patient relatively few problems, unlike impacted mandibular third molars. A retained deciduous canine may have a relatively poor appearance compared with a properly aligned permanent canine, but most patients are frequently unaware of the presence of and do not seek treatment for the overretained deciduous canine. The discovery of palatal impaction is therefore usually made by the general dentist during routine dental examination.

Fig. 6.15  The impacted canine crown is surrounded by a large dentigerous cyst, with associated root resorption of both the deciduous canine (to be expected) and the permanent lateral incisor (pathological).

shedding and why this does not normally occur with the roots of permanent teeth. Histologically, there is no way to tell the difference between the root tissue of a deciduous and that of a permanent tooth. Under certain conditions, however, the presence of an unerupted permanent canine tooth may be associated with the resorption of the root of the adjacent lateral (Figure 6.15) or central incisor [53–59]. Furthermore, and in a manner similar to that seen with deciduous teeth, the progress of this undesirable phenomenon depends on further eruptive movements on the part of the impacted tooth. In this context, it is perhaps pertinent to comment that the maxillary canine and, occasionally, the third molars are almost the only permanent teeth whose eruptive movements, both successful and unsuccessful, may cause resorption of the roots of neighbouring teeth to any significant degree. They are also the only permanent teeth that normally develop in close relationship with the developing apical areas of the roots of other permanent teeth, while the premolar teeth develop in a restricted area, encompassed by the roots of the deciduous molars and at a distance from

Inspection The maxillary permanent canine normally erupts at a dental age of about 11 years. Its non-appearance at this age should invite clinical inspection and radiographic investigation, especially if its antimere is present. The maxillary incisor teeth are normally spaced and flared laterally until the age of 10 years, as described earlier in this chapter. Should this situation still be true by 11 or 12 years, the clinician should be suspicious, since this means that there is a detail missing from the mechanism that smoothly transfers Broadbent’s ugly duckling stage into the final adult alignment, with interproximal incisor contacts. Indeed, a resultant persistent median diastema may be the factor that brings the patient to the office to request treatment, unaware of the impacted canine. It is unlikely that a missing lateral incisor or a frankly peg-shaped incisor will be overlooked. Nevertheless, care should be taken to examine the size and shape of existing lateral incisors. Central and lateral incisors whose crowns have mesio-distal straight or slightly tapering sides and lack the classical proximal contour are usually small teeth and often develop late. Some of these are frankly peg-shaped, a condition defined by their widest mesio-distal dimension being at the CEJ. Furthermore, the discovery of a late-developing dentition and a dentition in which there are missing teeth, other than the lateral incisors, should also be treated with a degree of caution. We have reported above that all these factors have been linked with palatally displaced canines, and this

126  Orthodontic Treatment of Impacted Teeth possibility should be thoroughly investigated, both at the time when the phenomena are first noticed and in subsequent follow-up examinations that have been scheduled to oversee the smooth changeover from the mixed to the permanent dentition. Abnormally positioned unerupted canines frequently affect the positions of neighbouring teeth, particularly lateral incisors. We have already pointed out that the root apex of a palatally impacted canine is usually in the line of the arch, with the crown mesially displaced, in addition to its palatal tilt. This brings it into close relation with the palatal side of the lateral incisor, often displacing its root labially. Clinically, this will be identified by the root being very prominent on the labial side of the ridge or by a lingual tilt of the crown of the tooth, sometimes into a cross-bite relationship. In contrast, a lateral incisor whose root orientation indicates a strong palatally directed apical displacement suggests that the unerupted canine is labially placed and, at least to a degree, also somewhat mesially directed (Figure 6.16). Palpation We have pointed out above that, under conditions of normal development, the permanent canine is palpable buccally above the deciduous canine for two or three years

(a)

prior to its eruption. The buccal aspect of the alveolus should be palpated above the attached gingiva and up to the reflection of the oral mucosa. A wide convex contour of the bone is indicative of the canine, immediately beneath. Care should be taken not to confuse this with the narrower profile of the root of the deciduous canine. In the event that this contour is concave, the palatal side of the alveolar process should be palpated to see if there is a clue to its location there. The deciduous canine should always be tested for mobility. If this test is even mildly positive, it will suggest that the permanent canine is fairly close to the desired eruption path and that severe displacement is unlikely. In this situation, the unerupted canine may not be palpable on either side of the alveolar ridge. When there is a strong palatally directed apical displacement of the root of the lateral incisor, we have just pointed out that it is likely that the canine is also mesially directed. In this case, the unerupted cuspid will usually be palpable high in the labial sulcus and much closer to the central incisor root than to its normal position in the arch, and the contour of the alveolus, superior to the deciduous canine, may be concave. Given the unusual distancing of the permanent canine from its normal position, its deciduous predecessor will have most of its root intact and will consequently exhibit no pre-shedding mobility.

(b)

(c) Fig. 6.16  Clues to the position of the unerupted canine. (a, b) The unerupted left canine presents a palpable bulge overlying the root of the lateral incisors, seen from the front and the lateral aspects. At the same time, the lateral incisor root appears to be displaced distally and palatally. (c) From the occlusal view, compared to the orientation of the central incisor, the lateral incisor root has a distinctly palatal axial inclination, which is less obvious in the other two views.

Palatally Impacted Canines  127  Radiography As we shall see later in this chapter, to plan the strategy of mechano-therapy properly for a particular case and to obtain a pre-treatment assessment of the periodontal prognosis of the treated result, it is essential to know the exact positions of both the crown and the root apex of the unerupted tooth. A single periapical radiograph is essential to identify pathology, such as root resorption, obstruction and cystic change, but it should be supplemented by other films that will help to precisely locate the unseen tooth. The use of a second periapical radiograph in the parallax method has the advantage of simplicity of technique and provides both the orthodontist and the surgeon with important information regarding positioning, although the exact locations of crown and apex are difficult to compute from these pictures. A true lateral view (as seen on the lateral cephalogram or on a tangential film) paired with a vertex occlusal or postero-anterior cephalometric view is technically more difficult to obtain, but will provide accurate three-dimensional positional information of the unerupted tooth in its most comprehensible form. However, these films involve a high radiation dosage for a relatively poor return on the amount of information provided. The central portion of a panoramic radiograph shows the incisor region in the postero-anterior view and will indicate a palatal displacement as an overlap of the impacted canine with the roots of the incisors. This is by far the most popular method used today. The reader is referred to Chapter 2 for a description of how this film may be used by itself, or in combination with a periapical film, with an occlusal film or with a lateral cephalogram, to extract the maximum information regarding the position of an impacted canine. We have already pointed out that plain film radiography cannot provide reliable information in the bucco-lingual plane and, therefore, incisor root resorption may occur and remain undiagnosed until well advanced. Additionally, the bucco-lingual distance that exists between the impacted tooth and its neighbour is very difficult to assess from these films and this may be an important factor in plann­ ing the strategy for the biomechanical resolution of the impaction. For both these reasons and certainly in relation to all of the more involved cases, it is recommended that the immediate area be subjected to a computerized tomographic examination, using a cone beam volumetric scanning machine, to provide the maximum positional information while, at the same time, reducing the dosage of ionizing radiation to the absolute minimum.

Treatment timing In normal circumstances, by the age of 9–10, it is usually possible to palpate a normally developing maxillary permanent canine tooth on the buccal side of the alveolus, high above its deciduous predecessor. In the presence of crowd-

ing, and particularly after the eruption of the first premolar, the bulging of the unerupted canine is emphasized. The greater the degree of crowding the greater will be this displacement and the more palpable will the canine become, as its eruptive process brings it further and further down on the facial side of the dental arch. It follows, too, that the greater the buccal displacement the greater the risk that it will erupt through oral mucosa, higher up the alveolar process, rather than through attached gingiva. In the event that the tooth is not palpable at this age, radiographs should be taken to assist in locating the tooth accurately and to secure other information regarding the presence, size, shape, position and state of development of individual unerupted teeth and any pathology. In a patient younger than 9 years, the radiographs will not usually show abnormality in the position of the unerupted canine teeth, even if the canines are not palpable and even if they are destined subsequently to become palatally displaced. Many of these non-palpable canines will finally erupt into good positions in the dental arch in their due time, provided that there is little or no mesial and palatal displacement of the crown of the unerupted tooth. It may be argued that even canines with an initial mild palatal displacement will achieve spontaneous eruption and alignment despite a first-stage displacement, if they undergo secondary correction (see ‘The guidance theory’ in the section on Aetiology above). Other canines, however, will not erupt, and their positions may worsen in time, as may be seen in follow-up radiographs. If it were possible to distinguish between the two early enough, a line of preventive treatment might be advised. Preventive treatment and its timing Using panoramic radiographs of young patients in the mixed dentition, Lindauer et al. [21] were able, to a relatively low degree of reliability (78%) only, to predict palatal impaction on the basis of canine overlap of the root of the lateral incisor. Extraction as a means of prevention: deciduous canines

As we indicated earlier in this chapter, several authorities [20, 22] prescribe the extraction of the deciduous canine teeth in an attempt to encourage the permanent canines to erupt. They have recommended seeing the patient and diagnosing the palatal positioning before the age of 11 years, and have shown that extraction performed at this time offers a good prognosis for the natural eruption of the canine, with 78% of the canines in their sample erupting into a clinically correct position. Caution must be advised in interpreting these results, however, since the authors did not study an untreated control group and thus are not in a position to determine just how many of these teeth would have erupted without this preventive treatment [21] (Figures 6.17 and 6.18).

128  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 6.17  (a) A case diagnosed from this panoramic view as having bilateral palatal canine displacement and referred for extraction of the deciduous canines. (b) A year later, a repeat film shows great improvement in the position of both canines and normal eruption of the canines is imminent, despite the fact that the deciduous canines have not been extracted.

(a)

(b)

(c) Fig. 6.18  (a) A case of early crowding treated by extraction of four deciduous canines, to relieve crowding at age 8 years. No hint of impending palatal displacement of the canine is discernible on this panoramic film. (b) One year later, the incisors are aligned and spaced. Extraction of the four deciduous first molars (the second stage of serial extraction) was advised. (c) The panoramic view taken a year later reveals the maxillary right canine in a palatally displaced location, despite early extraction of the deciduous canine. Treatment of this case may be seen in Figure 6.41.

Palatally Impacted Canines  129  From their study, Ericson and Kurol concluded that the prognosis becomes less favourable as the palatally displaced canine’s medial overlap of the lateral incisor root increases and as the angle between the long axis of the canine and the mid-sagittal plane widens. They also noted that, if positional improvement of the canine was not evident within 12 months of the prophylactic extraction, it was unlikely that improvement would occur. From this discussion and from some considerable anecdotal clinical experience, we may assume that, under certain circumstances, the extraction of a maxillary deciduous canine may be a useful measure in the prevention of incipient canine impaction. To achieve maximum reliability, the following conditions should be met before extraction is advised: 1. The diagnosis of palatal displacement must be made as early as possible. 2. The patient must be in the 10–13-year age range, preferably with a delayed dental age. 3. Accurate identification of the position of the apex should be made and confirmed to be in the line of the arch. 4. Medial overlap of the unerupted canine cusp tip should be less than half-way across the root of the lateral incisor, on the panoramic view. 5. The angulation of the long axis should be less than 55° to the mid-sagittal plane. 4 and 5 on this list represent conditions that, if not fulfilled, may still lead to spontaneous eruption and alignment, so that while the chances are reduced, extraction may still be worth considering. Notwithstanding, in two studies carried out in Italy by the same researchers, their earlier paper [60] found no statistically significant differences between those cases in which the deciduous canines had been extracted and those in which no extractions were performed. Contradictory figures were presented in their second paper [61], in which deciduous canine extraction produced 65% success against 36% for non-extraction cases. One further factor that is frequently missed when studying the radiograph and, therefore, not normally taken into account as a causative agent is the occurrence of nonsymptomatic soft tissue pathology, specifically chronic periapical abscesses associated with non-vital deciduous teeth and enlarged dental follicles or early dentigerous cysts. These may lead to quite severe displacement and impaction of the unerupted permanent canine. Their elimination may often have a favourable outcome even when displacement is quite extreme (Figure 6.6). The reader is referred to Chapter 11 for a description of the treatment of teeth impacted in positions of extreme displacement by dentigerous cysts. Given that there is no truly reliable method of early detection of a potential palatal displacement [21], a claim that it was the pre-emptive extraction of the deciduous

canine that had elicited the normal eruption of a permanent canine must be viewed with some reservation on the basis of the present state of our knowledge. Clinical experience would lead us to be encouraged by the procedure in many cases, but an accurate assessment of its efficacy has still to be determined. In the mixed dentition period, the unerupted maxillary canine is often held too far mesially by the mesio-distally wide crown of the unerupted first premolar immediately distal to it. If clinical experience is to be countenanced in these days of evidence-based treatment decisions, the author has found that, together with the extraction of the deciduous canine, there is merit in the simultaneous extraction of the adjacent first deciduous molar. The rationale for this ‘pearl’ is that loss of the deciduous molar encourages a very rapid eruption of the first premolar. With its eruption, the large crown of the tooth erupts and a much narrower cervical root is substituted at the level of and distal to the unerupted canine. This creates a potential void distal to the canine, which appears to encourage the latter to drop back distally into the space that has relatively suddenly become available. There is reason to believe that this may redirect a potentially wayward canine and encourage its more normal eruption. Extraction as a means of prevention: first premolars

Within the minority group of patients with impacted canines who are considered to be extraction cases, usually because of incisor crowding, a class 2 relation or bimaxillary protrusion, the choice of teeth for extraction usually devolves on the first or second premolar teeth. The reasons for this choice are bound up with the history of ortho­ dontics itself. This offers much potential benefit to the displaced canine, since the proximity of these teeth to the canine facilitates the immediate provision of space close by. It also affords considerable opportunity for a spon­ taneous improvement in the canine position (Figure 6.19) during the early levelling and aligning stages of the mechano-therapy. Extraction as a means of prevention: lateral incisors

We have noted above that many of the impacted cases that we see are associated with anomalous lateral incisors. At the end of the treatment it is often necessary to alter the shape of these teeth by prosthetic crowning, laminates or composite build-ups to make them aesthetically acceptable, particularly those that are peg-shaped. We have pointed out earlier that palatal canine cases generally have spaced dentitions, comprising small teeth, such that crowding and the need for extractions in the overall treatment are unusual. Nevertheless, if extraction has to be made to treat the overall malocclusion, consideration should be given to the extraction of these malformed lateral incisors as an alternative to the conventional but healthy and anatomically perfect first premolars.

130  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 6.19  (a) The left side of a case with bilateral maxillary palatal canine impaction. The maxillary deciduous canine, deciduous second molars and first premolars were extracted and an attachment placed on each of the exposed canines. No active orthodontic treatment was commenced. (b) The same patient seen 14 weeks later. Both canines and second premolars have erupted spontaneously and to a similar degree.

We have described how the guidance theory of eruption of the canine offers a cogent argument of how palatal displacement of the canine may occur. In those cases described as a first-stage displacement, it was pointed out how the vertical wall of the alveolar process on the palatal side steers the vertically and palatally directed eruption on a more buccal course, to produce a secondary correction. This continues until the developing canine comes up against the root of a late-developing lateral incisor, which forms a barrier to its further progress. A second-stage impaction is thus created. Logically, the removal of this barrier should lead to a natural improvement in the position and eruption status of the impacted canine – the second-stage impaction with secondary correction. In practice, clinical experience shows this to be largely true (Figure 6.20). Extraction of the lateral incisor is not a suitable procedure in most cases, but in those patients where it is indicated, treatment time may often be very brief. However, a normally sized canine adjacent to a central incisor may create a marred and unsatisfactory appearance, particularly if the central incisor has a poor profile (frequently seen in these cases). Furthermore, by lining up the canine and first premolar in place of the lateral incisor and canine, respectively, a discrepancy between upper and lower tooth sizes may compromise the occlusion. Orthodontic space opening The only preventive measures that we have described up to this point have involved the extraction of teeth adjacent to the impacted, namely the deciduous canine, the lateral incisor or the first premolar, in the hope that the impaction will resolve spontaneously. An alternative and sometimes supplementary line of preventive treatment involves the generous opening of space for the teeth, using orthodontic

appliances. One of the primary functions of orthodontic treatment preparatory to the treatment of impacted teeth is the creation of space in the dental arches for the impacted teeth. When this is done, unerupted teeth may often begin to improve their positions, as will be seen on repeat radiographs, and may often erupt without surgical intervention (Figure 6.21). This is clearly due to an alteration in the relation of the canine crown to the roots of the incisors and a concomitant alteration in the guidance influence of these teeth. It provides further evidence to support the guidance theory of impaction [60–62]. Rapid maxillary expansion Over the past few years, there has been speculation regarding the efficacy of a rapid maxillary expander as a means of prevention. There would not seem to be any logical reason to suppose that skeletal mid-palatal suture-splitting expansion should provide the impetus for the spontaneous correction of an incipient canine impaction – a latero-lateral response to a sagittal problem. Nevertheless, a study by the same Italian researchers has shown that the method used on 7.6–9.6 year olds will increase the chances for eruption from 13.6% for an untreated control group to 65.7% for the group treated with rapid maxillary expansion [63, 64]. The diagnostic parameter used by the authors for confirming impending impaction was a reduction in the distance between the unerupted canine and the midline on a posteroanterior cephalogram in these very young patients! We may summarize that, on the basis of the evidence from the many studies presented here, there are several steps that may be taken in order to reduce the chances of palatal impaction of maxillary permanent canines, provided that the patient is seen early enough. These include the extraction of deciduous canines, rapid maxillary expansion and distal movement of posterior teeth to create exces-

Palatally Impacted Canines  131 

(a)

(b)

(c)

(d)

(e) Fig. 6.20  (a, b) A palatally impacted right canine is adjacent to the peg-shaped right lateral incisor, while the opposite canine has erupted in place of the congenitally absent lateral incisor. (c, d) The periapical films used to diagnose the palatal position of the canine by parallax. At the time of extraction, the palatal position of the canine was confirmed clinically. (e) The canine has erupted on the buccal side.

132  Orthodontic Treatment of Impacted Teeth

(a)

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(i)

Fig. 6.21  (a–c) A class 2, division 2 case with crowding in the maxillary arch and severe space loss due to early extraction in the mandibular arch. (d) A panoramic view shows a palatally displaced right maxillary canine. (e) A similar radiograph taken following distal movement of all four molars and space reopening. Note improved positions and prospects of all the unerupted teeth, particularly the canine. (f–i) The final dental alignment and occlusion. The right maxillary canine erupted unaided.

sive space for the canine. The exploitation of two or more of these methods in a specific case will, in all probability, be synergistic. Timing of mechano-therapy Most cases are not identified early enough to take advantage of these preventive steps, and will usually be seen for the first time by the orthodontist only after the initial and, by then, more obvious diagnosis has been made by the generalist or paedodontist. A coexisting malocclusion will have often been the reason for the patient requesting treatment, and the impacted tooth may have been discovered only as the result of the orthodontist’s routine clinical and radiographic examination. The patient is generally in the full permanent dentition stage, with the exception of the deciduous canine of the affected side. Sometimes, the remainder of the dentition is in a close-to-ideal alignment and inter-arch relation, as has been pointed out earlier, although a minor degree of local tooth malalignment may often be seen. This generally includes a laterally flattened or collapsed archform (Figure 6.22) and space loss in the immediate area, with space opening more mesially [9]. In only about 15% of cases [16, 17] is actual crowding present.

Fig. 6.22  A preformed archwire blank laid over the occlusal surface of the teeth closely conforms to this dental arch, except in the area of the impacted canine, which shows lateral flattening.

The periapical radiographs should be carefully scrutinized to discover any evidence of resorption of the lateral incisor roots. Should this be seen, orthodontic treatment, designed to rapidly deflect the developing canine away from the incisor, should be undertaken as soon as possible. If the resorption is advanced, and in the relatively unlikely event that this is an extraction case, consideration should be given to extraction of this affected lateral incisor. A reasoned

Palatally Impacted Canines  133  approach to the problem of incisor root resorption seen in association with an impacted maxillary canine will be discussed at length in Chapter 7. For the most part, however, there is no reason to hurry into treatment simply because palatal displacement has been diagnosed. The patient must first be prepared for the treatment to be undertaken, initially by explaining the nature and ramifications of the problem using the radiographs and plaster models as visual aids. The principal function of this exercise is to overcome complacency that most of these patients have, since their problem is one in which the facial appearance and oral function are rarely compromised. The aim is to inspire motivation and the necessary future cooperation. The dentition must then be protected against the incipient dangers that the placement of appliances is likely to generate. The necessary measures include a high level of oral hygiene and the use of appropriate fluoridating procedures, at home and in the dental office, as well as the treatment of any carious or periodontal lesions. After a period of a few weeks, during which the patient will, it is to be hoped, have undertaken these oral hygiene responsibilities on a regular basis, an oral examination should show pink, firm and stippled gums and an absence of plaque on the teeth. This being so, the time will be ripe to begin orthodontic treatment. In the non-cooperative patient, treatment should be denied until the above conditions are fulfilled. Should the dental awareness of the patient be too low for this ever to occur, alternative treatment modalities should be considered, particularly prosthetic replacement, although for these to be successful in the long term they may be just as reliant on oral hygiene as is orthodontic treatment. Nevertheless, an operative decision may be delayed for quite a long time, so long as there are no signs of morbidity, particularly root resorption. This means that periodic radiographic monitoring will need to be carried out on an infrequent but regular basis. Postponement for a few months or even a year is rarely a problem in straightforward orthodontic terms, and if it serves to bring the patient round to the ways of proper home care, then the time spent will have been worthwhile. Unfortunately, as already mentioned, the dental development is often delayed, which is why these patients reach the permanent dentition stage with the canine impaction diagnosis made only at the age of 14 or 15 years. Thus, from a social point of view, the patient may be less inclined to wear appliances if further postponement is entailed. From the strictly developmental point of view, the best time for therapeutic intervention is when the root of any affected tooth is of a length that is seen at the time of normal eruption. For the canine, this is a little in excess of three-quarters of the potential root length, which is virtually always present by the time the diagnosis of palatal displacement may be determined.

General principles of mechano-therapy When a patient arrives at the orthodontist’s office and a palatally displaced and unerupted canine is diagnosed, treatment must be planned in a disciplined manner. We have seen in Chapter 5, in regard to the impacted maxillary central incisor, that orthodontic preparation of the case is required and that surgical intervention is not to be undertaken in any haphazard or unplanned manner. By and large, appliances that are to be used to disimpact, erupt and align these teeth are, with very little modification, the same appliances that are used to align the other teeth. For impacted incisor cases, the patient is in the early mixed dentition stage and the time is not ripe for the treatment of the overall orthodontic problem. Thus, a first phase of treatment is planned to deal with the incisor anomaly only, leaving the remainder of the malocclusion to be treated in a secondphase intervention much later. This is not so in the present context where, with the exception of the impacted canine, the full permanent dentition is usually erupted. For this reason, the local anomaly and the overall malocclusion are usually dealt with together in one full and comprehensive orthodontic treatment plan. A diagnosis of the overall malocclusion needs to be made and a problem list set out, which includes the palatal canine. The problem list is then sorted into a treatment priority list, in which alignment of the impacted canine should precede many of the other items, but only after space has been made for it in the dental arch. The same principles that were used in the planning of treatment in Chapter 5 are applicable in the present context, although we shall now be dealing with the treatment of the entire dentition and not merely the area immediately adjacent to the impacted tooth. These principles need to be adapted to the new circumstances, and may therefore be presented as follows: 1. The appliance should have the capability to level and align all the erupted teeth in the same jaw rapidly and, with controlled crown and root movements, to open adequate space to accommodate the impacted tooth. As we saw when dealing with impacted incisors, this space is required both at the occlusal level and between the roots of the adjacent teeth for their entire length. This stage requires the use of fine levelling and aligning archwires initially, and space subsequently gained with the use of a more substantial base arch and sliding mechanics. 2. With the initial alignment achieved and no further movement of individual erupted teeth needed, these teeth are transformed into a composite and rigid anchorage unit, in which each tooth plays an integral part. This is done with a heavier wire, whose gauge is as large as the bracket will take, in order to allow as little ‘play’ of wire within the bracket as possible, thereby maximizing the anchorage value of each erupted tooth.

134  Orthodontic Treatment of Impacted Teeth 3. The surgical exposure of the crown of the impacted tooth should be performed in a manner that will achieve a good periodontal prognosis of the treated result. For a closed procedure, an attachment is bonded to it and the flap fully closed, with only a fine ligature wire leading through the gingival tissue to the recovered tooth. Alternatively, an apically repositioned flap procedure or window technique may be indicated and a dressing placed as required, while the placement of an attachment may be performed then or at a later date. 4. Using an auxiliary means of traction from the now rigid orthodontic appliance, a gentle and continuous light force, with a wide range of activity, is applied to the tooth and is aimed at erupting the impacted tooth along a path that is free of obstruction from neighbouring teeth [65– 68]. When the impacted canine is located mesial to the lateral incisor, there is no direct path from the canine to the space created for it in the arch, since the root of the lateral incisor stands directly between the two. This means that the tooth will need to be diverted in a different direction first, to circumvent the obstruction, and, only then, drawn along a new and unimpeded path to its place. This will be discussed later on in this chapter. 5. There should be final detailing of the position of the formerly impacted tooth, together with that of all the other teeth in both jaws. A class 2 or class 3 dental relation will usually be reduced at this point. These principles are by no means immutable and the orthodontist should always be prepared to re-evaluate and adapt them in the light of other findings in a particular situation and to suit a particular case. There is one specific palatal canine scenario in which a race against time exists in relation to the timing of treatment for class 2 and class 3 cases which have a skeletal component. Many of these cases require to be treated with the use of orthopaedic/functional appliances whose aim is to realize as much of the growth potential of the deficient jaw as is possible. In these cases, there are several potentially conflicting factors which need to be carefully managed and prioritized in relation to treatment sequence. These are as follows: 1. The results in orthopaedic/functional treatment are best realized during the growth period. 2. Maxillary canine impaction is much more frequent in females who complete their growth much earlier than males. 3. Patients with palatally impacted canines frequently exhibit an overall late dental development, which could mean that menarche and the cessation of growth could occur before the eruption of the full permanent dentition (i.e. a mature 15–16-year-old girl with a dental development more akin to age 12). 4. The resolution of the impacted canine may take considerable time and is not dependent on whether further growth may be expected.

Thus orthopaedic/functional treatment will be advised first, aimed at reducing the skeletal discrepancy while there is the promise of growth. The canine impaction would then be treated only when the dental arches had been brought to a class 1 relation and in the late mixed/early permanent dentition period – but in a 16+-year-old female. At this juncture, it is important to recognize two very important exceptions to the order of things that we have outlined above. The priority rating for an impacted canine which is causing resorption of the roots of adjacent teeth will overrule space considerations and will make treatment of the canine a matter for immediate attention. In Chapter 7, the discussion will concentrate entirely on these cases in which the progress of the resorption often proceeds at an alarming rate and in which time spent preparing space can lead to loss of the incisor tooth. Once incisor root resorption has been positively identified, therefore, the full focus of treatment should be directed at distancing the impacted tooth from the adjacent root as quickly as possible. In the absence of space in the arch, as will be seen in the examples illustrated in that chapter, the tooth should be exposed as early as possible and traction applied to erupt the tooth either into the palate or into the labial sulcus. In these locations, the tooth is out of harm’s way and further resorption of the incisor root will be drastically reduced or entirely eliminated [69] even when subsequent orthodontic movement to modify the position and angulation of the damaged incisor will be performed with forces directed from the appliance. Space may then be provided in the normal way and the canine realigned in due course. In order to provide space for an impacted tooth, there is a sequence of tasks that orthodontists normally go through with fixed orthodontic appliances that constitutes a largely immutable routine. The sequence first concerns levelling and alignment, which are achieved with the use of light, springy archwires. Only when a heavier and more rigid base arch can be inserted do we begin to create space, using compressed open coil springs and sliding mechanics. If all of this is performed on round cross-section archwires, the adjacent teeth are tipped mesially and/or distally, labially and/or lingually, intruded and/or extruded and rotated. With few exceptions, for every orthodontic bracket in use today, the horizontal slot generates mesio-distal uprighting movements which, in some cases, may move the root apex several millimetres mesially and/or distally. If rectangular archwires are used at any stage in this initial sequence, then torqueing movements of the root apex in a lingual and/or labial direction will also be introduced. Under the heading of ‘Diagnosis’ earlier in this chapter, there is a paragraph describing clinical clues that may be present to indicate the position of the impacted tooth, by virtue of the displacing effect that the tooth has on the positions of the neighbouring teeth, particularly lateral incisors. On the radiographs of the area, one may usually discern a cause-and-effect relation between the angle of the

Palatally Impacted Canines  135 

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(f)

Fig. 6.23  (a–c) Inadequate space for unerupted permanent canines with inter-incisal spacing. (d–f) The permanent canines in place at the completion of treatment.

unerupted canine and that of the lateral incisor. It follows, therefore, that virtually every ‘corrective’ root movement performed during the levelling and alignment stage will have the effect of forcing the root of the incisor against the crown of the impacted canine. In some cases, this may encourage a realignment of the orientation of the long axis of the canine, which may then rekindle its eruptive potential and spontaneous resolution of the impaction may occur, obviating the need for exposure surgery. Equally, it may further displace the canine, which may not be a serious consequence, since exposure surgery had been the planned line of treatment anyway. The third and most dangerous possibility is that the clash between the two teeth may result in resorption of the root of the incisor. This distressing outcome will paradoxically be seen alongside the ‘success’ of the incisor uprighting effort. Radiographic monitoring of the initial few months of treatment, using simple periapical films, should certainly be considered, but unexpected difficulty and duration of what is normally a simple and rapid movement should alert the practitioner to this possible eventuality. There are essentially four ways in which space may be provided for the palatally displaced canine: 1. Existing incisor spacing is due to failure in the progress from the ugly duckling stage of development to completion of the natural alignment [13, 14] and it may be closed off by moving the lateral incisor mesially to increase the space in the canine area. It was pointed out at the beginning of this chapter that the final stage in anterior space closure occurs when the canine erupts and influences the lateral incisor to move mesially. It was also pointed out that impacted maxillary canine teeth

are often intimately linked with small and peg-shaped lateral incisors and with small teeth in general. These are the reasons that it is common to find anterior spacing in these patients (Figure 6.23). 2. Improving archform. When the maxillary permanent canine erupts normally, it does so along a more buccal path than the deciduous canine and slightly buccal to the lateral incisor and first premolar, earning the title ‘cornerstone of the arch’. Comparing the two sides of the maxillary arch in a unilaterally affected patient, we have already pointed out that in the canine areas there is a much narrower maxillary width on the side of the deciduous canine than on the normal side. Exploiting improvement in the form of the arch in this region, which is almost automatically achieved with any fixed orthodontic appliance and preformed arches, will add two or three millimetres of space for the displaced tooth (Figure 6.24). 3. Increasing arch length. Studying the plaster casts from the occlusal aspect, it may often be noted that there is mesio-palatal rotation of the first molars. Additionally, mesio-buccal rotation of the first premolar is a frequent occurrence in these cases. Correcting these rotations can provide the much-needed millimetre or more of space on each side. If crowding is mild, the use of a headgear or class 2 traction against open coil springs is recommended in order to move the maxillary molars distally. This will provide the extra space which may then be concentrated in the canine area, using a multi-bracketed appliance system (Figure 6.25). 4. Extraction of teeth. When crowding is more severe, particularly where there is also a class 2 dental relation that is to be treated with the use of intermaxillary elastics, the

136  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 6.24  (a, b) Improving archform has provided adequate space.

extraction of a premolar tooth on each side of the dental arch in the maxilla and usually in the mandible will be required. With the extraction of the premolar, space for the impacted canine is immediately and very locally available, and so appliance therapy is not needed to provide the space. Second, following the loss of the first premolars, alignment, levelling and rotation of the remaining teeth are very much simplified. Third, with a local anaesthetic already covering the area and a surgical wound inevitable, it is logical to extract the deciduous canine and expose the impacted canine at the same time to reduce the number of surgical interventions and postsurgical discomfort to a minimum. Thus, in extraction cases, it may sometimes be recommended that the surgical exposure be undertaken prior to the placement of an appliance (Figure 6.19). When orthodontic appliances are placed at the beginning of treatment, the achievement of a good archform is an important first step in the maxillary arch. After the initial levelling wires, a coil spring is placed on a more substantial archwire of idealized form to increase the canine space by moving the lateral incisor mesially and the first premolar distally, until interproximal contacts are established elsewhere in the maxillary arch. This will usually provide more than enough space for the unerupted canine. A heavier-gauge archwire is then firmly ligated into the maxillary appliance and the space for the canine must be retained. In the various edgewise and prescription pretorqued bracket techniques, as heavy a rectangular base arch as possible should be used. In the latest Tip-Edge® Plus™ technique, a round 0.020 in or 0.022 in wire or, preferably, a rectangular 0.0215 × 0.028 in wire should be used as the base arch, with the addition of an auxiliary nickel–titanium archwire threaded in the horizontal channel behind the main bracket slot, or uprighting springs and torqueing auxiliaries to act as ‘brakes’ if necessary. The space that has been reopened for the canine may be maintained using the same coil spring, which will need to

be deactivated. However, it is difficult to adjust the spring to maintain the space accurately, and one will usually find that the space will increase or decrease slightly over the succeeding months. Furthermore, a coil spring quickly fills with food particles and is impossible to clean effectively. A much better alternative involves using a measured and slightly curved length of stainless steel tubing, which is threaded on the archwire and tied between the brackets of the premolar and lateral incisor, in place of the coil spring. This adds a great deal of rigidity to the archwire in the area of greatest importance and helps in resisting distortion, thereby providing an excellent and firm base from which to apply force to the impacted canine. Many of these canines have to be moved over a long distance to bring them into the arch, and several will require root movement of the different types before they may be properly brought into position and the case completed. This inevitably expends anchorage. The measures and precautions that we have described will contribute much to the preservation of anchorage.

The need for classification of the palatal canine During the orthodontic treatment of a patient, as with any other prescribed form of medical or dental treatment, attention is paid to achieving the maximum benefit that the approach has to offer, while sustaining the minimum possible adverse collateral changes to the health of the dentition and its supporting tissues that may be caused by the treatment. To this end, the orthodontist must ensure an adequate level of oral hygiene before and during the period when the procedures are performed and the forces generated by the appliances must be within certain limits, compatible with physiological tooth movement, so that permanent and irreversible damage is not inflicted on the dentition. In an extraction case, the decision regarding which teeth to extract is usually made on strictly strategic criteria, insofar as certain teeth require to be brought to particular

Palatally Impacted Canines  137 

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Fig. 6.25  Creating space by distal movement. (a–e) The initial clinical views of a mildly crowded dentition with incisor retroclination and a deep incisor overbite. The left deciduous canine is in cross-bite. (f, g) A safety, removable, acrylic high-pull headgear appliance with the facility to move posterior teeth selectively distally (with two jackscrews), to torque the incisors (Bass torqueing spring), in addition to the overall distalizing effect. Note the facility to use inter-maxillary elastic from the Adams clasps on the molars, to aid in the distal movement of the mandibular dentition. (h, i) More than adequate space has been created for the canine to be aligned. Note how ill-advised labial traction from a palatal eyelet has introduced a degree of undesired rotation into the canine as it achieves its place in the arch. This needs to be redressed in the final stage. (j–n) The treated result seen five months post-treatment.

138  Orthodontic Treatment of Impacted Teeth places and appropriate anchor teeth need to be chosen in order to achieve this. Given a good prognosis of each of the teeth in the mouth, with no severely carious teeth and excellent periodontal health, the criteria of orthodontic treatment strategy are the guide to this extraction decision. However, when a tooth or teeth are present whose longterm prognosis is in doubt, such as a molar tooth that is in need of root canal treatment and a post-and-crown restoration, this becomes an additional factor that must influence the choice of tooth for extraction. It would not make longterm sense if the immediate and beautiful orthodontic results were to be predicated on teeth that would not be present in the mouth a few years later, while healthy teeth of excellent prognosis had been sacrificed in the name of strategic convenience. Maxillary canine impaction in a case where teeth require to be extracted as part of the overall orthodontic treatment presents a similar dilemma. The canine is a tooth that has an important role in the establishment of a good functional occlusion. It has a long root and contributes much to the patient’s appearance, particularly the smile. These are factors which makes it a very valuable tooth and one worth the expenditure of considerable effort to bring it into position. Its substitution by a first premolar is not usually desirable. It is inappropriate to automatically and blindly extract an impacted canine with a good prognosis in preference to an erupted first premolar, just as it is inappropriate to extract a first molar rather than a first premolar simply because the molar has a small occlusal filling. But what if the long-term prognosis of the canine is poor because of its initial intractable position or as a consequence of its having been through the processes of surgical exposure and orthodontic alignment over the period of many months or years that were spent in its meticulous alignment? In such a case, perhaps it would have been better to remove that particular canine at the outset and to have brought the first premolar to its place [70]. Since extraction cases are very much in the minority among patients with palatally impacted canines [16, 17] every effort must be made to bring the canine into the arc, and to do this in a manner that will provide it with its best possible periodontal prognosis. The clinician must carefully assess the several factors that affect the prognosis of the results of treatment in each individual case prior to the beginning of treatment, in order to be in a position to make the optimal decision regarding the choice of tooth for extraction. At the time that the patient’s records are being studied in order to formulate a suitable treatment plan, it would be helpful if there were a way in which it is possible to assess the long-term prognosis of an impacted canine before treatment is started. It is therefore crucial to seek a key that may be available to help us decide which canines will be adversely affected in periodontal terms and which will take an inordinately long time to resolve their impaction:

of the creation of surgical access to them • asby atheresult relative • into alignment.difficulty in orthodontically moving them From the surgical aspect, which we have discussed in Chapter 3, minimal exposure and full flap closure (with attendant attachment bonding) is the preferred line of treatment, aimed at primary healing, for the majority of cases. Does a tooth that requires a whole range of different types of orthodontic movement pay a periodontic penalty, in the final analysis, in comparison with one that is more simply aligned? Teeth that are mechanically erupted bring with them a generous amount of alveolar bone. It has been shown in studies in Israel [71–73] that the assisted eruption of buried teeth with the use of orthodontic appliances produces a collar of alveolar bone around the erupted tooth that is greater than that seen on normally erupted adjacent teeth. These studies have shown this to be true only where surgical exposure was conservative and did not involve removal of the entire follicular sac. Radical surgery leads to less bone support than is present in a normally erupted tooth and considerably less than the minimally exposed impacted tooth. The most likely explanation for this is to be found in the procedure that prosthodontists call ‘forced eruption’ [74, 75]. When one side of a tooth is fractured or destroyed by caries to below the height of the crestal bone, an infra-bony pocket is produced. The treatment that is prescribed to eliminate this is to mechanically erupt the tooth away from the bone margin and to thus orthodontically reverse the relationship between the prepared crown shoulder or cavity margin and the interproximal alveolar bone. At the same time, the other sides of the same tooth, whose relationship with the bone was normal to begin with, are extruded together with their adjacent alveolar bone. This generates excessive bone in the latter areas, extending more coronally than is normally seen, which sometimes needs to be reduced by periodontal/osseous surgery. In relation to the resolution of impaction, it has been shown [71–73] that, in contrast with extrusive movement, teeth that undergo root uprighting and torqueing movements end up with a significantly lower crestal bone level than untreated controls. The histogram in Figure 6.26 shows the influence of the various combinations of conservative vs. radical surgical exposure and extrusion/tipping vs. root movement orthodontic forces on the relative bone support of impacted canine teeth. These results are an indication of the periodontal prognosis of the teeth concerned. One last factor, which is often ignored or simply overlooked, relates to root resorption that may occur in the impacted tooth during the extended period that may be involved in its alignment. In orthodontic treatment generally resorption of the root apices of teeth may sometimes

Palatally Impacted Canines  139  96 94

Percentage

92 90 88 86 84 82

Control

X l Ml

Xl Mh

Xh Ml

Xh M h

Fig. 6.26  Bone support levels in the treated canines (light bars) compared with the normally erupted opposite canines (dark bar); Xl, minimal surgery and primary closure; Xh, surgery in which the follicular sac was removed down to the CEJ; Ml, orthodontic tipping, extrusion and rotation movements only; Mh, root uprighting and torqueing movements. (Adapted from ref. 72.)

be seen. The reasons for this are not clear and although some clues are available, there is no known key that may be used to predict with confidence those patients in whom resorption will occur. What is found, however, is that the resorption process almost invariably stops when orthodontic tooth movement is completed. In most patients for whom major orthodontic movements have been carried out, resorption is exceptionally small and of no clinical significance. Nevertheless, there are occasional cases where these ill-effects may account for the loss of 3 or 4 mm of the original root length. Although there are dissenting reports [76] regarding resorption and treatment duration, the overriding opinion is that there is a linear relation between resorption and treatment duration [77–80]. In the absence of definitive information regarding the mechanisms involved, therefore, it would seem wise that, for those patients who are prone to root resorption, orthodontic treatment should be kept to a minimum in terms of duration and complexity. The optimal result for those individuals may not even come close to the ideal. For the resorption-susceptible case, it could conceivably happen that all the precautions that we have described may be followed scrupulously and a good periodontal result may be obtained. However, unusually severe resorption may account for a final root length of, say, 12 mm. A 2 mm difference in height between crestal bone and the CEJ will give a relative bone support in this patient of only 83%, and the long-term prognosis must be judged accordingly. Thus, for cases in which there is a more compromised bone loss in the cervical area, with a greater CEJ-to-crestal bone height difference, the relative importance of root resorption as a factor in long-term tooth survival increases. Monitoring for early indications of root resorption may be performed during the progress of the mechano-therapy of a given impacted canine using periapical radiographs. However, since the position and, more specifically, the ori-

entation of the tooth is changing during the orthodontic treatment, comparison with earlier films may be difficult. It should also be remembered that even when marked resorption is noticed, it is unlikely that the orthodontic treatment will be stopped much before full eruption of the impacted tooth has been accomplished. Less would render the canine valueless for all practical purposes and under any circumstances. The efficacy of radiographic monitoring is only relevant at the point when the crown of the tooth has been brought into its place in the arch, and a decision has to be made whether root uprighting and torqueing movements are merely desirable in the interests of a meticulous alignment or essential, the absence of which would be to the long-term detriment of the treatment result. If a periapical radiograph taken at this juncture shows that significant resorption is evident, its severity must be offset against the relative importance of producing these root movements.

A classification of palatally impacted canines All forms of surgery inflict trauma which, in the present context, may have lasting effects on the success of the outcome in terms of its periodontal prognosis. In order to simplify the discussion and to exclude complicating factors, we shall assume that the most appropriate surgical technique has been chosen for exposure of a given impacted maxillary canine and that this procedure is performed with a high level of expertise. We have concluded that: trauma generated by surgery is greater when access is difficult; and orthodontic alignment is more complex when the impacted tooth has a greater displacement, particularly if the root apex is not in the line of the arch. Yet it is these two factors, both of which relate to the position of the tooth, that will later dictate the quality of the supporting structures of the treated result. Accordingly, it becomes clear that the patient’s best interests are served if an accurate visualization of the exact location of the buried tooth is made at the time of treatment planning. It follows that if palatal canines are classified in relation to their position in the maxilla, they will essentially be grouped in accordance with the prognosis of their therapeutic outcome. The classification that is offered here is based on two variables: the transverse relationship of the crown of the tooth to • the line of the dental arch, which may be close or distant (nearer the midline); the height of the crown of the tooth in relation to the occlusal plane, which may be defined as high or low.

•

Determination of the location of the crown of the impacted tooth is achieved by employing the radiographic methods that we have outlined earlier. More than anywhere else, the use of computerized tomography (CT) scanning has made this exercise much simpler and more relevant. It provides

140  Orthodontic Treatment of Impacted Teeth the clinician with a reconstruction of the three-dimensional image of the impacted tooth and its environs, with no effort and no possibility of error. This positional determination may be subsequently confirmed by direct vision at the time of surgical exposure. In this section, several cases will be presented to illustrate the salient clinical features of the impacted canines in each of the classification groups. An approach to treatment will be discussed within each group and how this needs to be adapted to suit the conditions seen in each. Where relevant, cases that were treated inappropriately will also be presented, with the aim of revealing how the shortcomings of the results occurred and to discuss what alternatives could have been employed to prevent the undesired sequelae. Group 1 proximity to line of arch: close position in maxilla: low.

• •

Typically, palatal canines that are close to the line of the arch and low in the maxilla suggest a good prognosis, insofar as the tooth is usually palpable in the palate and readily accessible to surgery (Figure 6.27). These canines represent by far the most common form of palatal impaction. In its simplest form, the canine is opposite the space and is not rotated. The root apex is usually in its correct location and root movements are rarely necessary. Surgery

If the canine is only mildly displaced to the palatal, it may be approached from the occluso-buccal (Figure 6.27d), in which case little bone removal is needed to reach it. A labial flap is raised from the crest of the ridge or from the gingival margin of the deciduous canine, which would be extracted. The edge of this flap would then comprise thick attached gingival tissue. For a more palatally located canine and following the reflection of a palatal flap (i.e. a flap of thick firmly bound mucosa), the canine is immediately obvious under its bulging but thin covering of bone on the inner surface of the alveolar ridge. Minimal removal of eggshellthin bone is needed to reach the follicular sac, and access for bonding an attachment to the tooth is good. After suturing of the full flap, the pigtail ligature is drawn through the sutured edge in the direction of the main archwire. Planning the orthodontic strategy

With the tooth immediately opposite its place in the arch, orthodontic alignment requires some extrusion, but principally a buccal tipping movement. Thus, direct force application between pigtail and archwire is the most appropriate (Figure 6.27e). Properly planned surgery will result in the intermediary, be it twisted steel ligature or gold chain, emanating from the sutured edge of the replaced flap. Traction applied to this intermediary will encourage the impacted tooth to erupt through attached gingiva, closely resembling

a naturally erupting tooth, to provide it with a normal periodontal environment. Problems that may be encountered

In the simplest group 1 case, the eyelet may be sufficient to complete all the movements required. Alternatively, and if surgery has exposed a sufficiently long clinical crown, a conventional bracket may be placed immediately. However, it should be remembered that, as the tooth moves buccally, it gathers gingival tissue ahead of it and, if oral hygiene is not excellent, the exuberant soft tissue will become inflamed and may impinge on the bracket. Undoubtedly, wider exposure of the crown will eliminate this, but will compromise the periodontal tissues in the final analysis. Thus, it is wiser to use an eyelet initially and replace it as necessary when the tooth reaches the main archwire. Complications

Group 1 canines in their initial positions may be complicated by rotation, mesial crown displacement or palatal root displacement. Rotation The type of rotation that the canine generally presents is a mesio-palatal, with the buccal surface of the tooth facing mesially towards the root of the lateral incisor. This means that during treatment the appliance must incorporate a rotational mechanism to bring the tooth into alignment. The simplest manner in which to do this is to initially place the eyelet on the anatomic labial surface of the crown of the canine, which faces anteriorly, towards the lateral incisor and orienting it vertically in the long axis of the tooth (Figure 6.28). A full-arch nickel–titanium auxiliary wire, together with heavy main arch, is the method of choice [81]. This fine and highly elastic wire is threaded directly through the vertically oriented eyelet, which introduces a strong deflection into this auxiliary archwire. This will then exert a force couple that will both bring the tooth to its place in the arch and, at the same time, bring about a very efficient correctional rotation (Figure 6.28). It is, however, essential to check that the ligation of the auxiliary into the other brackets of the appliance is not too tight so as to limit its movement, since the efficiency of the appliance is dependent on this free-sliding attribute. A good alternative involves the use of a ‘slingshot’ elastic (see Figure 4.7) or elastic thread tied between the eyelet and the cut length of stainless steel tube that has been threaded on to the main archwire, for use as the canine space maintainer and to add rigidity to the base arch. While the canine is being moved towards the line of the arch, it is also being rotated about its long axis in a corrective mesio-buccal rotatory movement. Since the stainless steel tube space maintainer will not allow individual movement of the adjacent teeth, the direction of rotation may be changed or

Palatally Impacted Canines  141 

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Fig. 6.27  (a, b) Intra-oral views of the initial condition. (c) Space was opened using a coil spring and sliding mechanics. An over-sized stainless steel tube was cut to measure, curved and placed in the archwire to maintain space and to increase base arch rigidity. (d) Exposure and attachment bonding – a closed eruption procedure. The pigtail ligature was drawn downward and shaped over the archwire to allow for replacement of the flap without impingement. Traction was applied immediately. (e) Two weeks post-surgery, a new ‘slingshot’ elastic module is stretched between the brackets of the lateral incisor and first premolar. Its middle portion is raised to engage the pigtail hook with a controlled and measurable light extrusive force. (f, g) Three months post-surgery. An inferiorly and laterally offset light wire arch is substituted and the tooth ligated with steel ligature wire to achieve full eruption. An orthodontic bracket now replaces the eyelet. (h, i) Periapical view, showing comparable supporting bone levels in the treated and untreated canines. (j, k) The gingival appearance shows comparable gingival levels on the treated versus the untreated side. It is unlikely that an open exposure procedure could produce a result of this calibre.

142  Orthodontic Treatment of Impacted Teeth

(a)

(b)

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Fig. 6.28  Using an eyelet for eruption and rotation. (Courtesy of Dr H Corimlow.) This canine was a group 2 canine, but was erupted into the palate and then drawn towards the labial archwire. (a, b) With the canine only partially erupted but markedly rotated, the original vertically oriented eyelet (bonded at the time of exposure) is exploited to rotate the tooth, using a fine (0.014 in) nickel–titanium auxiliary archwire, under the main 0.020 in stainless steel base arch. (c, d) Four weeks later, the auxiliary wire is removed and the base arch threaded directly through the eyelet. At the next visit a bracket will be substituted to effect appropriate finishing.

increased to fit other types of rotated palatal canines, by tying the elastic thread from the eyelet directly to the premolar or lateral incisor teeth. Mesial crown displacement This is very commonly seen in conjunction with the mesiolingual rotation that we have just described. Whether or not the rotation is present, the proximity of the anatomic labial surface of the canine to the lateral incisor creates constraints on the placing of a bracket at the mid-buccal position of the canine crown. As a general rule, this space is too small for the placement of any of the conventional brackets, which are much bulkier. To overcome this, many practitioners bond the conventional bracket, with its rigid and contoured base, on the irregular palatal surface of the tooth, to which it is totally unsuited and to which the reliability of the bond is much lower, increasing the risk of detachment to almost one case in two [82]. A further drawback to using a regular bracket on the palatal aspect of the tooth is that traction applied directly between it and the archwire will substantially increase the existing and adverse rotation of the tooth. This will be very

difficult to correct later and will significantly add to the amount of mechano-therapeutic manipulation that the tooth must undergo. As a result, the periodontal prognosis of the tooth will be compromised unnecessarily. Traction from an eyelet placed in the ideal mid-buccal position on the tooth, even if it is more incisally located because of the physical limitations imposed by the proximity of the lateral incisor, will bring about a corrective rotational movement as the tooth is drawn towards the target area. As with a bracket, palatal bracket-siting of an eyelet risks a complication (detachment) and, while it solves one problem (the impaction), it creates another (increased rotation), which may be just as formidable. It is relatively easy to bond an eyelet close to the ideal mid-buccal position of the exposed tooth and to draw elastic thread from it to the rigid tubing that has been placed on the archwire to maintain the canine space in the arch. It may be advantageous to tie the elastic thread to the bracket of the first premolar to increase the mesio-buccal rotatory component of the traction. The premolar will not close down the canine space because of the presence of the stainless steel tubing. When

Palatally Impacted Canines  143  the period of traction becomes extended, it may slowly bring about adverse changes in the dental midline by tipping of the incisors in that direction. In this case, additional precautions will need to be taken to protect the anchorage. Super-elastic auxiliary archwires threaded through a vertically oriented eyelet are a good alternative and will achieve a similar result. They will usually work with greater efficiency, provided the distortion of the wire is not so great as to cause binding in the brackets of the adjacent teeth. Palatal root displacement If the root apex of the canine is palatally displaced, in addition to the palatal crown displacement, the crown will first need to be aligned in the manner that we have just described. This includes the correction of any possible rotation and mesial crown displacement. With the canine crown in place and the main archwire firmly ligated into the newly substituted, conventional bracket, the palatal inclination of the crown-to-root orientation of the tooth will dictate that its palatal surface bulges inferiorly, while the buccal surface tips labially and superiorly. The heavy archwire is now needed to serve as the base arch to a labial root-torqueing auxiliary. The heavy base arch provides the fulcrum about which the auxiliary will buccally rotate the root apex. Employing a full rectangular arch, which is torqued in stages on the canine only, the long-axis inclination will be seen to improve. However, the equal and opposite reactive force is on the roots of the adjacent teeth, which provide the anchorage for this difficult movement. These adjacent teeth are being torqued lingually at each torque-adjusting stage and then buccally as the torqueing force is expended – a classic example of ‘round-tripping’ which, when considerable torque needs to be applied to the canine, transfers an equal and opposite torqueing force on the adjacent teeth. This, in the case of a small lateral incisor or one with a partially resorbed root that is associated with the impaction, may undermine the long-term prognosis of the incisor. Regardless of the type of orthodontic brackets employed, there are advantages to using a torqueing auxiliary that derives its anchorage from the narrowed archform of the heavy main archwire. This will avoid distortion of the dental arch, and will not create unwanted side-effects on the adjacent teeth. Group 2 to line of arch: close • proximity position in • incisor root.maxilla: forward, low, and mesial to lateral The root apex of the canine in this group is usually to be found in its correct mesio-distal location in the line of the arch, and at more or less the correct height. The crown of the tooth, however, is tilted mesially (forward) and in close

Fig. 6.29  The periapical view of an extreme example of group 2 canines. The left canine is located between lateral and central incisor roots and the right canine is mesial to the central incisor root. Reproduced with permission from Gill and Naini, forthcoming, with permission.

association with the palatal aspect of the root of the lateral incisor (Figure 6.29) and often sited between the roots of lateral and central incisors [66]. The tooth is not always palpable on the palatal side. Surgery

Surgical exposure in this group is complicated by the often unavoidable simultaneous exposure of the roots of these adjacent teeth. Aggressive surgical techniques may occasionally open the way for the orthodontist to bond on the labial surface, but not without considerable damage to the adjacent exposed incisor roots by the radical removal of bone. With the position of the crown of the impacted canine situated mesially to the root of the lateral incisor, several operative problems present themselves. In the first place, surgical exposure has to be carefully undertaken so as not to damage the roots of the incisors. The temptation to expose too widely should be resisted and only enough of the most conveniently accessible surface of the tooth should be uncovered to permit bonding. The palatal surgical flap should be replaced in its entirety in order to provide maximum protection and tissue reattachment for the exposed incisor roots and the area of exposed bone, and to re-establish a normal periodontium. However, to provide an exit for the twisted ligature pigtail that is tied to the attachment, a small piercing should be made in the flap immediately opposite the attachment on the tooth, using a wide-bore needle. Alternatively, the flap may be divided into two halves by a slit that is made with electro-cautery rather than a scalpel in order to prevent bleeding at the cut edge. The pigtail is passed through the pierced hole or the slit, and the flap is sutured back into place (Figure 6.30).

144  Orthodontic Treatment of Impacted Teeth

(a) (b)

(c)

(d)

Fig. 6.30  First published in Orthodontics Principles and Practice, Daljit S. Gill, Farhad B. Naini editors, Impacted Teeth and their Orthodontic Management by Adrian Becker & Stella Chaushu, 2011, Wiley-Blackwell, Oxford, UK, with permission of the publisher. (a–c) Intra-oral views of a class 1 malocclusion with retroclined and crowded incisors and an impacted left maxillary canine. (d) The initial panoramic view showing the canine to be displaced almost to the midline of the palate. (e) The cephalogram confirms palatal displacement. (f) The auxiliary stainless steel archwire intended to disimpact the canine. (g) Following alignment and space opening, the auxiliary archwire is ligated in, over the space maintaining steel tube place between lateral incisor and first premolar. The auxiliary is in its vertical passive mode. (h) The occlusal view immediately pre-surgery, showing the canine bulge in the palate. (i) A palatal flap is raised from the cervical margins of the teeth, up to the midline, leaving the incisive canal bundle intact. The canine is minimally exposed, revealing its proximity to the midline. (Surgery by Dr Harvey Samen.) (j) An eyelet attachment is bonded by the orthodontist on the anatomically labial aspect of the crown of the canine. (k) The twisted steel ligature pigtail is pushed through the palatal flap at a point immediately opposite the eyelet. (l) The flap is fully replaced and sutured, to leave no unprotected wound. The pigtail ligature can be seen to exit the palatal tissue immediately opposite the eyelet. (m) The pigtail is shortened and bent to form a firm hook around the vertical loop of the auxiliary archwire, which has been turned inwards and raised flush with the palatal tissue. This applies measurable extrusive force to the impacted tooth. (n) Several weeks later, the fully healed palatal tissue shows a very much increased and palpable bulge outlining the tooth beneath. (o) A small incision in the thick mucosa around the tip of the crown of the tooth has permitted the tooth to erupt. Labial traction is now applied using elastic thread to draw the tooth to the main archwire. (p) The occlusal view shows that much labial root torque is needed. (q) An accessory torqueing arch has been placed to move the root apex buccally. (r–u) The finished case showing a shorter clinical crown than on the untreated side. (v–x) Panoramic, lateral skull and periapical films of the completed case.

(e)

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(l) (k) Fig. 6.30  (Continued )

146  Orthodontic Treatment of Impacted Teeth

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(q) Fig. 6.30  (Continued )

Palatally Impacted Canines  147 

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(w) Fig. 6.30  (Continued )

148  Orthodontic Treatment of Impacted Teeth

(a)

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(c) Fig. 6.31  (a) A group 3 canine has been exposed by an open procedure and healing is by secondary intention. (b) An edgewise bracket (!) has been sited on the palatal aspect of the canine. The tooth is being drawn from this palatal attachment directly to a flexible labial archwire (!). (c) The tooth has reached the archwire, and is now rotated a further 30–40°. Note the swollen appearance of the gingiva and its poor contour.

The mesio-palatal rotation of the canine that is usually present in these cases places the labial surface of the canine in a completely inaccessible position. This means that only the palatal or distal aspect of the canine is available for siting the attachment. Planning the orthodontic strategy

From an eyelet placed on the palatal side of the tooth, direct traction to the labial archwire is sometimes possible. However, if traction is performed in this manner, the attached surface leads the way, and it will inevitably cause the canine to ‘roll’ over the root of the lateral incisor, to increase the existing rotation (Figure 6.31) and to risk damage to the incisor. Furthermore, the operator could well be faced with a 180° rotation to perform once the tooth reaches the archwire! Few will dispute that this task is formidable, but before the adventurous clinician even begins to argue that it is not insurmountable, the following three questions should be considered. 1. How long will the derotation prolong the appliance therapy? 2. Will the rotational relapse factor be possible to overcome?

3. What will be the prediction for the health of the periodontium at the completion of correction of what will have been an iatrogenic rotation? For many of the impacted teeth in group 2, the intimate relation between canine crown and lateral incisor root will block movement of the canine when traction direct to the archwire is applied. The inexperienced operator may then respond by increasing the pressure applied to the tooth and, within a fairly short period of time, there will be signs of loss of anchorage on the other teeth, characterized by the production of a cross-bite tendency, a midline shift from the affected side and tooth mobility, not to mention the possibility of damage to the lateral incisor root and failure to bring the canine down. A completely different approach is needed, in which the tooth must first be moved in a different direction to free it from potential entanglement with the incisor roots. The most practical manner of doing this is to draw it vertically downwards (towards the tongue), erupting it into the palate and thereby bringing it to face its target location. In this way, the tooth will have a clear path to its place in the arch without any interposing adjacent roots and the group 2

Palatally Impacted Canines  149  canine will have been converted to a group 1 canine. It may then be moved directly across the line of the arch, towards the labial archwire, in a second movement. It is for this reason that the pigtail ligature wire must be drawn through the fully replaced surgical flap and not through its sutured edge. The site of passage of the ligature wire through the flap should be immediately opposite the buried tooth, in order that vertical traction may be applied with ease and relative comfort for the patient. Traction in this direction from a palatally sited eyelet will not cause a rotation of the impacted tooth as it progresses. Three types of maxillary spring auxiliary may be used to bring about this desired movement that is needed initially, in this first stage of the resolution. These are the ballista [67], the active palatal arch [65, 66] and the light auxiliary labial arch [68]. With each of these methods it is essential that a heavy base arch be tied into the brackets of all the teeth on the labial side and to hold the opened space for the canine in the arch, to resist secondary distortion of the occlusal plane and archform and to provide a base from which to apply the force to the tooth. The ballista [67] (Figure 6.32) is a unilateral spring of rectangular wire, which is tied into one of the rectangular

(a)

molar tubes. It proceeds forwards until it is opposite the canine space. At this point, it is bent vertically downwards towards the lower jaw and terminates in a small loop. With light finger pressure, the vertical portion is turned upwards and inwards, across the canine space, and ensnared in this active mode by turning over the pigtail ligature around its terminal loop to hold it close to the palatal mucosa. In this way, torque is introduced into the horizontal part of the rectangular wire, which is the source of the vertical traction. Its equal and opposite reactive force is thus transferred to the anchor molar. The elasticity of the ballista spring exerts pressure for it to return to its original vertical position, which in turn applies extrusive force to the unerupted tooth. If the impacted tooth is fairly resistant to movement or if the distance that the tooth needs to be moved is great, lingual molar root torque may occur, representing a loss of anchorage. To overcome this, a rectangular main arch or a soldered palatal arch may be used. The active palatal arch (Figure 6.33) consists of a fine 0.024 in (0.6 mm) palatal archwire carrying an omega loop on each side. The wire is slotted into a soldered horizontal 0.024 in (0.6 mm) tube on the palatal side of the maxillary

(b)

Fig. 6.32  (a) A ballista in its passive mode, pointing downwards. (b) Using light finger pressure, the looped end of the spring is turned inwards and upwards towards the palate, where it is ensnared by the stainless steel pigtail from the unerupted canine.

(a)

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Fig. 6.33  (a) The active palatal arch in its passive mode, lying several millimetres away from the palate as seen from the occlusal. (b) The same view after the active palatal arch has been gently raised towards the palate and ensnared by the pigtail hooks, thereby applying vertically extrusive traction to the unseen canines.

150  Orthodontic Treatment of Impacted Teeth

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Fig. 6.34  (a) Initial treatment has created space and a heavy base arch, carrying a stainless steel tube space maintainer, in place. (b) A typical auxiliary labial archwire of 0.016 in gauge with its vertical loop and terminal helix. (c) The auxiliary labial archwire was tied into the brackets piggyback style over the heavy base arch, immediately prior to surgical exposure. (d) Following full flap closure, the vertical loop was gently raised and turned inwards, with its helix secured into the terminal hook of the pigtail.

molars. It may optionally be further secured by a steel ligature tie and distanced from the palate by finger pressure. By elevating the downward-activated palatal archwire and hooking the pigtail ligature around it, the unerupted tooth comes to be erupted through the palatal tissue, in a direction slightly away from the teeth. The auxiliary labial wire [68] is a third possibility (Figure 6.34); it requires no advance preparation of any sort, such as the soldering of lingual tubes. It is most conveniently fashioned from an archform blank of 0.014 in or 0.016 in diameter round wire by forming a vertical loop in the area of the impacted canine. This loop has a small terminal helix. The auxiliary is tied into all the brackets of the arch, in piggyback style over a heavy main arch, with the extremities slotted into a spare tube on the molars or left free distal to the second premolar brackets. In a similar manner to the ballista, the vertical loop is activated by raising it palatally across the canine space, and ensnaring it in the pigtail ligature in the palate. The auxiliary labial wire draws its activa-

tion from its curved archform, which does not therefore transfer torque to the molar. This is a particularly useful method for use with a bilateral impaction, when two different loops will need to be inserted into the archform. Used without a base arch, as has been recommended elsewhere [83, 84], it will extrude the adjacent teeth and thereby alter the occlusal plane. It will move the molars buccally and additionally will alter the horizontal arch form in the incisor area. A base arch is therefore mandatory. In the construction of the ballista and auxiliary labial wire, it is important to calculate the length of the active arm in advance. This may be done by pinpointing the intended location of the eyelet on the tooth and its projected exit from the palatal flap, either on the plaster cast or directly in the mouth, by palpation of the bulge in the palate. Alternatively, the location may be estimated from the radiographs and, particularly, from the CBCT which will provide greater accuracy. The distance between this point and the

Palatally Impacted Canines  151 

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Fig. 6.35  (a, b) With the eruption of the canine into the mid-palate, the eyelet position has to be changed to enable labial traction that encourages simultaneous corrective rotation.

labial archwire represents the optimum length of the active arm. If the arm is made shorter or longer, it will be difficult to approximate it to the palatal tissue and the arm will stand uncomfortably away from the palatal mucosa, to interfere with tongue activity. If it is made too long, it will draw the tooth away towards the midline as it vertically erupts it and, with it, the apex of the canine will be similarly drawn down and palatally, adversely altering the tooth’s centre of resistance away from the line of the arch. This will mean that its final alignment will require more labial root torque than should otherwise have been necessary. It is therefore preferable to err on the side of a shorter active arm. A mandibular removable appliance represents a method that requires no maxillary appliance at all in the first instance [85]. Vertical extrusive force is derived from a removable appliance in the opposing jaw through the agency of a simple rubber band. This elastic is applied by the patient between the clasps of the mandibular appliance and the pigtail ligature in the palate. In order for this to be efficient, several clasps used for retention of the plate on the teeth need to be included in the design and the form of the teeth must lend itself to good retention, otherwise the plate will be easily dislodged by the vertical intermaxillary elastic force. A maxillary orthodontic appliance is later needed to move the tooth into the line of the arch, achieve levelling and aligning of all the teeth and any needed finishing, but only when the tooth has erupted through the palatal mucosa. A much better and more reliable method of applying intermaxillary force rests with the use of a simple temporary anchorage device. A screw implant may be placed in the mandibular jaw in the inter-radicular bony area between the canine and first premolar. Traction in the form of

simple latex elastic rings may be applied from the implant device directly to the pigtail ligature by the patient. However, if a maxillary appliance is present from the outset, it is more effective if the elastic is engaged in a hook attachment on the appliance, while the orthodontist controls the traction applied to the impacted canine by ligating it to the archwire. This represents indirect traction from the implant to reinforce the anchorage of the whole appliance on that side of the maxilla to permit the safe and controlled application of an extrusive force to the canine. Regardless of which method is employed, the successful end-result will find the newly erupted tooth, surrounded by a wide rim of palatal mucosa and bone, in the middle of the palate (Figure 6.35). The more the tooth is erupted, the easier it will be to place an attachment on its buccal surface to enable the tooth to be moved buccally, without the bracket impinging on the gingiva, yet encouraging a simultaneous corrective rotation. However, an excessively erupted tooth will lead to occlusal trauma as it moves across the line of mandibular teeth. For the first stage of the two-stage manoeuvre, the position of the eyelet is not critical. Therefore, bonding is performed to the most convenient surface available, since no adverse rotation of the tooth will occur while it is being moved vertically downwards. The tooth is cleared of the lateral incisor root and moved until it has an unobstructed path to the labial archwire. A second eyelet is bonded to the tooth, this time on the mid-buccal aspect, which will have become accessible as the result of the initial orthodontic movement. The second stage of traction may then commence, with the application of force from the second eyelet directly to the labial archwire.

152  Orthodontic Treatment of Impacted Teeth The point should be made that in this case, and in any other group or situation, direct traction to the archwire should only be performed from an attachment sited in the mid-buccal position of the tooth. Traction applied at any other site will engender an unwanted rotation as the tooth progresses towards its place in the arch – a rotation that will require correction in an extra and superfluous phase of orthodontics. Problems that may be encountered

As the tooth initially progresses in the eruption path that has been planned for it, the thick and resistant palatal tissue bulges more and more, but may not allow the tooth to erupt through it (Figure 6.36). Delay or increasing trac-

tion forces will not improve the chances of progress of the impacted canine, but the tissue resistance will encourage the forces of the auxiliary to be expressed against the anchor unit, causing the adjacent teeth to intrude, to generate an open bite and a serious disruption in archform. This obstacle will necessitate a very limited and super­ ficial surgical removal of the thick mucosa immediately over the crown of the tooth. The anterior palatine artery is located in this immediate area and care should be taken not to sever it, in what is otherwise a very simple procedure. This may be done without releasing the traction mechanism and then left another two or three weeks, during which time the tooth will be seen to advance at considerable speed.

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Fig. 6.36  (a) Minimal exposure and eyelet attachment bonding of the palatal aspect of a group 2 canine in a 17-year-old female. The tip of the cusp has not been exposed. (b) Suturing was completed with the pigtail emerging through the divided flap. The palatal arch is in its passive state. (c) The palatal arch fully tied in and active. (d) Seen three months later, after two intervening visits for adjustment, the archwire has become distanced from the palate and the canine can be seen to bulge the contour of the palate almost to the occlusal level. (e) The deciduous canine was extracted at the same time as the minimal re-exposure was performed, preparatory to buccal movement. A second eyelet is bonded slightly mesial to the mid-buccal position and elastic ligation is drawing the tooth directly to the archwire, with a favourable rotation vector from the second eyelet. (f) At 13 months post-surgery the canine is in the arch and a bracket is substituted for the eyelet. (g, h) The gingival health of the treated canine is good, but its clinical crown is longer than the untreated left canine. (i) The periapical view. Note the resorbed root apex of the right lateral incisor. (j, k) Post-treatment periapical views to show comparable bone support of treated and untreated canines.

Palatally Impacted Canines  153 

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(i) Fig. 6.36  (Continued )

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(k)

154  Orthodontic Treatment of Impacted Teeth Once the tooth is well erupted at the level of the occlusal plane, the new eyelet attachment is bonded to its anatomically buccal surface (Figure 6.36e). It is then drawn in a direct line to the labial archwire and to the place where space will have been provided for it in the initial ortho­ dontic phase of the treatment. Initial rotation of the canine will still be present when this second phase of the traction begins, but it will correct steadily as the traction proceeds, with the attachment and buccal surface leading the way. Even with good oral hygiene during the traction period, much exuberant gingival tissue precedes the canine during its migration towards the line of the arch. The premature bonding of a conventional bracket may result in tissue impingement, particularly as the tooth comes into close relation with the adjacent teeth. The orthodontist should not relinquish the use of the eyelet until no further buccal movement is needed. Complications

The initial location of the tooth may be complicated by one or both of the following conditions: 1. Rotation. As with the group 1 canine, a mesio-lingual rotation is common and is largely corrected during the second stage of resolution, when traction is made from the second eyelet on the buccal surface of the tooth. 2. Palatally displaced root. Occasionally a tooth in this group may present with the root palatally displaced, in addition to the crown (i.e. a palatal translation of the entire tooth). Its occurrence will complicate the appliance work by requiring the introduction of buccal root torque and often some mesio-distal root uprighting. These forces may only be applied once the crown has been engaged by the main labial archwire. It will be appreciated that a group 2 canine has to be approached with a good measure of preparedness. From the surgical point of view, access is not difficult, but exposure must be performed carefully to avoid exposing and damaging the roots of the adjacent teeth. The orthodontic appliance may need to execute as many as five different types of movement, involving both crown tipping and root movement (i.e. vertical extrusion to move the tooth away from the palate), buccal tipping to the line of the arch, rotation, mesio-distal root uprighting and buccal root torque. From the periodontal point of view, the prognosis of the result is dependent on the smooth execution of each of the surgical and orthodontic operative procedures. Mismanagement of any part of the orthodontic and the surgical stages may not be germane to the question of whether the final alignment of the tooth will be technically successful, but it will be critical in determining the final bone level (Figure 6.36j, k), periodontal condition, clinical crown length, gingival architecture and natural appearance that may be achieved (Figure 6.36g, h).

Group 3 to line of arch: close • proximity position in maxilla: high. • The root apex of the canine in this group is situated very high in the maxilla, although most often in the general bucco-lingual line of the arch and in its correct location in the antero-posterior plane. The crown is high and only relatively mildly displaced palatally; it is not usually palpable. Surgical and orthodontic strategy

Access to this tooth may be from either the buccal or the palatal side, with advantages and disadvantages to both approaches, since there is a significant thickness of bone both on the buccal side and the palatal side of the tooth. Considerable bone removal is needed to reach it from either side, with similar difficulty in the application of an attachment. The orthodontic treatment entailed in aligning such a tooth involves principally extrusion, together with a buccal tipping movement. The buccal approach

From the buccal side, the tooth is approached as for a buccal impaction, described in Chapter 3. The surgeon may have greater difficulty in locating the impacted tooth and will be more dependent on the radiographs. The apically repositioned flap [86, 87] would, at first sight, appear to be a good approach, since it offers suitable access for the application of orthodontic force direct to the archwire. It also ensures that an adequate band of attached gingiva be raised as a part of a split-thickness flap above the level of the impacted tooth and then accompany that tooth in its subsequent downward path. From the surgical point of view, however, this approach takes no account of the three-dimensional location of the canine. The method may be very suitable for a buccal canine whose vertical displacement is relatively minor, but in the case of a more superiorly displaced palatal canine, this type of exposure would leave a considerable expanse of periosteum and alveolar bone open to the oral environment. The flap would need to be sutured several millimetres lateral to the crown of the tooth unless considerably more bone were to be removed on the buccal side of the crown of the tooth to enable the flap to bridge the large gap between the labial mucosa and the palatal tooth. Furthermore, the maintenance of the exposure of a canine crown palatal to the line of the arch would secondarily cause a denuding of the interproximal areas of the roots of the adjacent lateral incisor and first premolar teeth. Postsurgical discomfort with this method is more severe and more prolonged than with a closed exposure procedure [88–90]. This method is only suitable for cases of very minor palatal displacement. Full labial flap reflection after reducing the size of the flap and its subsequent partial replacement over the exposed

Palatally Impacted Canines  155 

(a) (b)

(c)

(d)

Fig. 6.37  A case treated by the author c. 1972, using the approach recommended by Johnston (ref. 11), Lewis (ref. 91) and von der Heydt (ref. 92). (a, b) The group 3 canine has been exposed from the buccal side and bone has been channelled to clear a direct path to the archwire. (c) With the band cemented to the canine the radical nature of the surgery may be seen. (d) The aligned canine shows a healthy gingival appearance, but a long clinical crown and a lack of normal bony contour, with deficient interdental papillae. (Reprinted from Kornhauser, S, Abed, Y, Harary D and Becker, A (1996), The Resolution of Palatally-impacted canines using palatal-occlusal force from a buccal auxiliary, Am. J. Orthod. Dentofac. Orthop. 110: 528–534, with permission of Elsevier.)

tooth, together with the placement of a surgical pack to cover the exposed tooth and surrounding tissues during healing, has been used for many years and was widely advocated [11, 18, 91, 92] for mildly palatally impacted canines. It shares features with the apically repositioned flap procedure described above. In the case of a group 3 canine, however, it must be remembered that a considerable thickness of alveolar bone is present both inferiorly and inferobuccally to the canine, which must be traversed by the tooth. In order to overcome this physical impediment, the above authors have recommended the surgical channelling of bone to free a path in the direction of the dental arch (Figure 6.37). Experience with this procedure shows that while it lives up to its expectations regarding the provision of access and the enablement of direct traction, it does so only by the planned sacrifice of much of the bone of the immediate area of the alveolar process! The treated result then leaves an aligned canine with an unacceptably reduced

bone support, poor gingival contour and a poorer periodontal prognosis than could be achieved by other means. The tunnel approach

An excellent modification of this method has been described [93] in which the buccal plate of bone is preserved, while the impacted tooth is drawn through a tunnel in the bone provided by the vacated socket of the simultaneously extracted deciduous canine. This method is particularly suited to the group 3 canine. A full labial flap is reflected to include attached gingiva from the crest of the ridge and the impacted tooth exposed from its buccal aspect, leaving the buccal plate inferior to it intact. The deciduous canine is extracted and its socket extended and widened sufficiently to allow the passage of a fine wire through it as far as the impacted tooth (Figure 6.38). It is not necessary, however, to widen it to the full diameter of the crown of the canine, which must pass along this path. Much time will elapse

156  Orthodontic Treatment of Impacted Teeth

(b)

(a)

(c) Fig. 6.38  (a) The ‘tunnel’ approach of Crescini. Note the preservation of the buccal plate inferior to the tooth. The stainless steel pigtail is drawn inferiorly through the vacated socket of the deciduous canine. (b) At 2.5 months post-surgery, the ‘slingshot’ elastic module has brought the canine into a buccally palpable position. (c) One year after completion of treatment. Note the gingival height, wide attached gingival band and good bony contour. The lateral incisor is congenitally missing.

before a markedly displaced canine reaches the coronal end of this ‘eruption tunnel’ and much reparatory bone will be laid down in its path, well ahead of its final and unimpeded eruption. Nevertheless, the progress of the biomechanically encouraged eruption may be achieved with no more difficulty than that of impacted teeth in more favourable locations and with unimpeded paths of eruption. Given the narrow eruption path planned for this tooth in the present context, it is obvious that no attachment other than a small eyelet is suitable for bonding at the time of exposure. The eyelet is threaded with 0.011 in or 0.012 in soft ligature wire, ready for bonding to the newly exposed impacted canine. Following appropriate acid etching of the enamel surface, the attachment is loaded with the bonding agent and its steel ligature pigtail is lightly curved and threaded into the immediate area of the exposed tooth and on into the prepared tunnel until it emerges from the occlusal end of the deciduous canine socket. At this point, the eyelet attachment is pressed firmly into place on the impacted tooth and cured. Feeding a gold chain down

the tunnel is impossible, since the individual links adhere to the bloody walls of the prepared deciduous tooth socket, unless the chain is led down using a wire ligature threaded through the terminal link as a pathfinder. The surgical flap is fully sutured to its former place and visual contact with the impacted tooth is lost. Control of future movement of the canine is exercised through the application of force to the steel pigtail ligature or gold chain, whose extremity may be seen to extend through the sutured edges of the flap within the deciduous canine socket at the crest of the ridge. Any excess in length of the ligature is cut and it is fashioned into a small hook, to which elastic traction may be applied (Figure 6.38b). The surgical method affords good access to the canine and a minor degree of difficulty in threading the ligature through the vacated deciduous canine socket. Orthodontic traction may be efficiently applied and the treatment result shows a good bony profile and an uncompromised periodontal result, similar to that seen on normally erupted teeth [93] (Figure 6.38c).

Palatally Impacted Canines The palatal approach

If the canine is more palatally displaced, surgery approached from the buccal side will be more radical, involving the removal of comparatively large quantities of labial bone and, in these circumstances, a palatal approach is to be preferred. Following the raising of a palatal flap, the canine will be revealed high up, palatal to the roots of the adjacent teeth, which occasionally may themselves become denuded in the exposure process. Inferior and lateral to the canine is the vertical wall of the alveolar process. Bonding of the eyelet attachment is performed in the usual manner to the most conveniently accessible site, which is the palatal side of the tooth, although the buccal surface, close to the tip, is occasionally sufficiently approachable (Figure 6.39). In this situation, many surgeons will remove a part of the flap in order to leave the impacted tooth in visual contact with the exterior and will place a pack to cover the open area. If the stainless steel pigtail ligature is drawn towards the line of the arch and sutured into place so that its extremity comes through the deficient part of the flap, the application of orthodontic forces will give rise to significant danger of irritation and infection of the area. This is caused by the tooth being drawn buccally and vertically downwards by its ligation to the labial archwire. The resultant direction of this force will cause the impacted canine to be drawn laterally against the alveolus and its healing granulation tissue. The exposed tooth will become reburied in these tissues (Figure 6.40) as it proceeds downwards and buccally. This leads to inflammation, false pocketing, acute pain and the likely occurrence of an acute lateral periodontal abscess. It is therefore advised that orthodontic strategy for group 3 canines be approached in the same manner as with group

(a)

157

2 canines, by dividing their resolution into two distinct stages (Figure 6.41). Because of the considerable risk of exposing the root surfaces of the adjacent teeth, a closed eruption surgical procedure is to be preferred, since it requires a much more limited entry into the follicle and exposure of enamel surface – enough only to provide a bonding site for a small attachment under conditions that permit adequate haemostasis. More radical removal of

Image not available in the electronic edition

Fig. 6.39 Direct traction vs. two-stage traction in the group 3 canine. Reproduced from previous edition with the kind permission of Informa Healthcare – Books.

(b)

Fig. 6.40 Acute periodontal pain from prematurely attempted buccal movement in a group 3 canine. (a) The patient had bilaterally impacted palatal canines and these were drawn vertically downwards using an active palatal arch (see Figure 6.32). The left side canine erupted ahead of the right and the active palatal arch was discarded. New eyelets were bonded and traction was applied in a buccal direction on each. The left canine moved rapidly into place, but the insufficiently erupted right canine became partially buried in the vertical alveolar process and caused acute inflammation and pain. The swelling and redness can be clearly seen. The remedy is to irrigate the area, prescribe mouthwashes and return to the vertical eruption stage. An auxiliary labial archwire was placed, seen here in its passive mode, unattached to the eyelets. (b) The auxiliary labial archwire in its active mode to elicit further vertical eruption prior to the second attempt at buccal movement.

158  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

Fig. 6.41  (a) A group 3 canine exposed and viewed from the occlusal aspect to show the attachment bonded near the tip of the buccal side. (b) Six weeks later and without further adjustment, the canine has erupted through the closed flap. (c) Buccal traction to the buccally placed eyelet. (d, e) The buccal and palatal views of gingival tissues on the treated side, 16 months post-surgery. (f, g) The same views of the normal side. (h, i) Periapical views of the treated (right) and untreated sides, showing comparable bone support levels.

Palatally Impacted Canines  159 

(f )

(g)

(h)

(i)

Fig. 6.41  (Continued )

bone around the mesial and distal curvatures of the crown and enucleation of the follicle are both unnecessary and harmful to the final periodontal outcome and prognosis of the aligned tooth [94]. Orthodontic traction is first applied in the lingual and vertically downward direction, to erupt the tooth into the palate, palatal to the line of the arch, and brought down to the occlusal level. As it comes down it is accompanied by a wide collar of newly formed alveolar bone. As was noted in relation to the group 2 canines, in many cases the palatal tissue is very resistant and bulges more and more as the tooth progresses, not allowing the tooth to erupt – a situation that demands the very limited and superficial surgical removal of the thick mucosa immediately over the crown of the tooth. At this point, an additional eyelet should be placed on the buccal aspect, as for a group 2 case, and the direction of traction altered to a pure buccal tipping movement to bring it into the arch. It is often possible to bond a conventional bracket to complete this second stage if there is enough gingival clearance on the buccal surface of the tooth, although this may not be necessary. Since neither rotation nor ectopic root apex position is common in these cases, the second-stage tipping movement generally brings the canine into its desired position and inclination. The canine that is located in the position that we have described here presents different problems from the group 2 cases. Direct traction is, under these circumstances, technically possible, but periodontally hazardous. The most direct surgical remedy (from the buccal side) may be too radical and leaves the tooth relatively unsupported by bone, in the final analysis, unless the ‘tunnel’ approach [93] is used. However, for the palatal approach, careful two-stage orthodontic movement will require minimal surgery and avoid undesirable periodontal sequelae. As pointed out earlier in regard to the use of an auxiliary labial wire or ballista, it is important not to make the active arm too long and to thereby draw the root apex of the impacted tooth palatally. In such a case, a tooth which might otherwise have had a normally

located root apex will now iatrogenically require labial root torque in its final alignment. The principal feature that distinguishes the group 3 case from the simple and straightforward group 1 case is its relative height in the alveolus. The root apex is usually in the line of the arch and the crown is only relatively minimally displaced palatally, which often means that the tooth cannot be palpated. The group 1 canine requires a minimal degree of vertical development in the mechano-therapy and mainly a buccal tipping movement from its more severe palatal position. The group 3 canine, on the other hand, has primarily to be extruded vertically. If only a very minor buccal component is needed, then a buccal approach to surgery, using the ‘tunnel’ method, may be the best way to go with the promise of a superior periodontal outcome. Group 4 to line of arch: distant • proximity position in maxilla: high. • When the crown of the palatally displaced canine is not directly related to the roots of the incisors, it generally points medially and approaches or even crosses the midpalatal suture (Figure 6.42). It is not always palpable in the palate. Surgery

These teeth are generally at some distance from the adjacent teeth and little bone removal is needed to expose them, with scant danger of exposing the roots of other teeth. There is usually reasonably good access for the placement of a bonded attachment, although the immediate exposed surface is unlikely to be the buccal aspect of the tooth. Planning the orthodontic strategy

Since there is normal positioning of the root apex in most of these cases, all that would appear necessary is to draw the tooth directly to the labial archwire. If the long axis of the tooth is close to the horizontal plane, it would be inappropriate to do this since the direction of this force would

160  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 6.42  (a) The active palatal arch in place to erupt a group 4 canine that has traversed the midline. (b) Post-surgical periapical radiograph shows space opening and an active palatal arch ligated to the bonded attachment. (c) After three months of traction, minimal re-exposure of the now very superficial and palpable canine was performed. A posterior component was achieved using elastic thread to the lingual tube of the molar of that side. (d) Disto-buccal followed by purely buccal traction was also performed. Distal uprighting and buccal root torque were later needed. (e, f) Intra-oral views to compare the buccal gingival health and clinical crown length of the treated (right) and untreated canines. (g, h) The same on the palatal side.

Palatally Impacted Canines  161 

(g)

(h)

Fig. 6.42  (Continued )

be virtually coincident with its long axis. This makes the mechanics highly inefficient and little progress in resolving the impaction will be seen. The procedure will become excessively taxing on anchorage and will give rise to a reactive movement of the entire maxillary dentition to the opposite side. With the tooth close to the horizontal, a more cautious approach should be embarked upon. A wide downward tipping movement will be achieved more efficiently with the same vertical directional approach that has been described for use in group 2 and 3 cases with the use of spring auxiliaries. In their tied-in and activated positions, the ballista and the light auxiliary labial arch mechanisms lie across the palate, parallel to and closely mimicking the orientation of the long axis of the unerupted and horizontal canine. As these mechanisms work themselves out they move in the same downward and buccal arc of circle that is needed for the resolution of the canine impaction. Were the fulcrum for this wide tipping movement of the canine to be at the root end, it would follow that the root apex position would be unchanged when the crown finally reached its destination, vertically oriented and in the line of the arch. Unfortunately, however, the fulcrum is often some short way along the apical portion of the root; therefore, during the alignment of the tooth there will be a concomitant, but relatively minor, palatal displacement of the root apex of the canine. Thus, some buccal root torque of the group 4 canine will later be necessary. It also follows that in the unusual situation where there is a palatal displacement of the root apex at the outset much torque will be required, and this presents a major clinical problem.

Problems

Torque cannot be usefully applied until the crown of the tooth has reached its place in the arch and its newly bonded conventional orthodontic bracket firmly engaged by the labial archwire. At that juncture, the crown of the canine is at the occlusal level and has a strong buccal tilt. This places the palatally displaced root low in the palate, with its profile clearly outlined under the muco-periosteum. That critical portion of the lingual side of the root closest to the crown of the canine has a markedly convex shape, which dictates a distinct bulging of the mucosa covering it. In the clinical context, some dehiscence of this lingual area of the CEJ is usually present. Additionally, the cingulum area of the palatal aspect of the crown is very prominent and is likely to interfere with the occlusion. It is important to recognize that in group 4 and many group 2 cases, considerable lateral movement of the canine is required, most of which involves tipping. Quite frequently, buccal root torque is also needed, and this may be quite substantial, particularly in the present group. Accordingly, there is an equal and opposite reactive force acting over a long period on the entire anchor unit, which, if properly planned and prepared, will respond only minimally. This will be expressed as a movement of the dental midline to the opposite side and a cross-bite tendency on the same side. In order to minimize this, a heavy base arch should be used and its form altered to compensate for the expected movements. In the most extreme circumstances, the use of intermaxillary S-elastics will be a necessary adjunct, i.e. from the buccal of the lower molar to the lingual of the upper molar on the side where a cross-bite

162  Orthodontic Treatment of Impacted Teeth tendency has occurred, and from the lingual of the lower to the buccal of the upper on the other side. Thought should be given to the inclusion of temporary anchorage devices in the general scheme of anchorage preparation. A titanium screw may be placed in the same dental arch for direct traction application or in the opposing arch for use with intermaxillary elastics. A bilaterally affected case provides the opportunity for nullifying loss of anchorage by pitting one side against the other, such that midline and archform alterations need not occur. To summarize the group 4 cases, the clinician must be alert to difficulties in the mechanics that may be inherent due to the initial location of the canine. Care must be taken to preserve orthodontic anchorage by properly planning the mechano-therapeutic strategy of reducing the canine displacement. The practical limitations imposed may lead to adverse effects on the periodontic status of the lingual aspect of the tooth, where occlusal interference may be present in the interim until the root position is corrected. Finally, following long, meticulous and successful treatment of the group 4 canines, there appears to be a strong relapse tendency that will result in the canine crown dropping back a millimetre or two into an edge-to-edge relationship with the opposing teeth and sometimes into a renewed cross-bite relationship. This seems to occur even after a fairly lengthy period of retention and the tooth may require permanent splinting. It is also related to the tendency to underestimate the amount of labial root torque that is need in these cases and an under-torqued canine will be very prone to positional relapse into an edge-to-edge relation with the lower canine. The Seattle group [95, 96] has recommended open exposure and packing of canines before any orthodontic treatment is initiated. They do not give guidelines as to which cases are most suitable, nor have they investigated the success rate of this procedure, although it seems likely to be most appropriate for those canines in groups 2 and 4. In their view, the canines will erupt autonomously into the palate in the succeeding several months, thereby saving valuable time in appliance therapy when this is initiated at

(a)

a later date. In order for this to be successful, it is incumbent on the surgeon to ensure that the exposure wound will not later heal over and this will make it mandatory for the exposure to be wide and fully down to the CEJ, with removal of the follicle in its entirety. Moreover, it has been shown that canines may take a very long time to erupt adequately into the mouth – of the order of 20 months or so [60] – offsetting any advantages that a shorter period of time with orthodontic appliances might bring. From the periodontal investigation of these cases the researchers found loss of bone support on the affected side compared with the controls and 79% of these teeth could be identified as having been previously impacted. It remains to be seen whether the same level of outcome can be achieved using this method as with the closed exposure approach. Group 5 root apex mesial to that of lateral incisor or distal • tocanine that of first premolar. This tooth should be considered as transposed. To be completely consistent with the definition of transposition, the canine apex should be in the line of the arch in the place of the root apex of the adjacent tooth, but it is indepen­ dent of mesio-distal or bucco-lingual crown location. However, partial transpositions or pseudo-transpositions are more common, in which the apices are displaced to a more limited extent and the order of the crowns of the teeth has reversed. The canine–first premolar (CPm1) transposition must be considered as a three-dimensional phenomenon. The premolar may often be found in its ideal erupted location in the arch adjacent to the second premolar, but with a strong mesial displacement of its root, and also with a palatal displacement of its long axis when viewed from the occlusal aspect. On the buccal aspect of the sulcus above the premolars, there is usually a bulge which clearly identifies the position of the canine. In many cases, this tooth will erupt spontaneously, although it will emerge high in the oral mucosa (Figure 6.43).

(b)

Fig. 6.43  (a, b) A maxillary canine/first premolar transposition, treated to reverse the transposition.

Palatally Impacted Canines  163  Among the canine–lateral incisor (I2C) transpositions, the phenomenon is rarely limited to a two-dimensional model since this would mean that, while the positions of the crowns and/or roots of the two teeth involved are reversed, there is no bucco-lingual displacement from the line of the arch of either tooth. The more typical and frequent presentation of this transposition involves the interrelationship between the canine and both incisors mesial to it, and it affects their alignment in all three dimensions (Figure 6.44). There are discrepancies in the mesio-distal, bucco-lingual and height locations of the crowns and roots of the teeth concerned. The root of the lateral incisor is distally and palatally displaced under the influence of a more mesially sited and mesially tipped canine, which is located superiorly and labially to it. This strictly defines the canine as a labial rather than palatal impaction in relation to the lateral incisor. However, the further eruptive movement of the tooth may occasionally bring the crown tip further mesially and on the palatal side of the root of the central incisor. Thus, the canine traverses the alveolar ride obliquely with its crown on the palatal side of the central incisor, while its root is labial to that of the lateral incisor. This is not an uncommon configuration and it is difficult to diagnose using plane film radiography only. Without the benefit of CBCT imaging, this may nevertheless be achieved in the following manner: 1. Viewed clinically from the front of the patient, the orientation of the long axis of the lateral incisor will usually exhibit a distal displacement of the root in the apical (crown-to-root) direction. The canine is not palpable on the labial or palatal sides of the ridge. 2. Viewed from the occlusal aspect, with the patient’s head tipped back, the long axis of the lateral incisor also has a posterior displacement in the apical direction and the outline of the root may often be seen to bulge immediately beneath the palatal tissue. Its orientation is widely divergent from that of the long axis of the adjacent more upright central incisor. 3. A pair of periapical views employing Clark’s tube-shift method will place the canine crown palatal to the root of the central incisor on which it is superimposed. 4. A panoramic view will show the canine ‘riding high’ over the lateral incisor and, usually, partially superimposed on it. The root apices of the canine will be above and in line with or possibly distal to that of the incisor, but more superiorly located. The classic picture of the arrangement of the maxillary incisors in a class 2 division 2 malocclusion is depicted by central incisors tipped lingually and lateral incisors tipped labially. This is an incisor arrangement that seems to be associated with this particular scenario within the group 5 canine, presumably because of the wide divergence of the central and lateral incisor roots. In view of the very different eruption times of the incisors and canines, it would seem

(a)

(b)

(c) Fig. 6.44  (a, b) Canine/lateral incisor transposition seen intra-orally and on panoramic radiograph. (c) The completed alignment of the teeth in the transposed order. Grinding of the incisor edge of the lateral incisor needs to be performed to avoid occlusal interference and to improve appearance.

that the complexity of this impaction is the result of the incisor presentation and not its cause. On the CBCT, the various views clearly show the interrelations between the teeth with great clarity and the orthodontist should be in a position to devise a method to resolve this very awkward entanglement.

164  Orthodontic Treatment of Impacted Teeth Surgery

Surgical exposure of the CPm1 impacted canine is much simpler because of its favourable buccal position above the premolar teeth. Since the tooth is high in the oral mucosa, an apically repositioned flap is the most appropriate means by which the tooth will be rendered accessible and a periodontist will probably be the most suitable surgeon to perform this. It would appear that there are two possible approaches to provide surgical access to the I2C transposed canine: buccally or palatally. We have seen that for a palatally impacted canine the exposure must be performed on the palatal side of the ridge and the tooth drawn palatally away from the incisor roots and towards its place in the arch. The crown of the canine for the present canine-lateral incisor (I2C) situation is palatal to the crown of the central incisor, but it would be a serious mistake to use a palatal surgical approach. There can be no question that a labial approach to the canine is the simpler way. Palatal access is especially difficult because the tooth is very high up on the palatal side of the root of the incisor, much bone will need to be removed to reach it and attachment bonding will be fraught with difficulty. However, a palatal approach would be fatal to the outcome of the case because traction applied to the canine from a palatal auxiliary will draw the root of the canine against the labial side of the lateral incisor root and displace its apex palatally while, at the same time, obstructing the progress of the canine. The most likely outcome of such a manoeuvre would be the loss of both these entangled teeth (Figure 12.16). The only way to achieve success in these very special cases is to expose the tooth on the labial side, using a wide flap raised from the area of attached gingiva. Since the canine is high and close to the root apex of the central incisor, only a small portion of the more distally presenting surface of the canine should be exposed. This surface is readily accessible with little or no bone removal. The follicle is conservatively opened, wide enough for the bonding of a small attachment at that site. The tooth cannot be drawn directly down to the archwire, but must be directed disto-labially for it to have a clear path of exit from the palatal to the labial side of the ridge between the central and lateral incisors, respectively. To achieve this, the stainless steel pigtail or gold chain will need to be drawn horizontally and distally through a small puncture in the oral mucosa portion of the fully replaced surgical flap. It cannot, therefore, be drawn through attached gingiva in the first instance. In the subsequent weeks of successful activation, the tooth comes to bulge the oral mucosa as it moves labially and distally around the lateral incisor, towards its place in the arch. If care is taken not to apply too effective a labial traction component, the tooth may remain beneath the mucosa for much of its early movement. When appropriate, surgical apical repositioning of a flap taken from the attached mucosa over the alveolar ridge may be used to

re-expose the tooth and continue its traction to its final destination, encompassed by firm gustatory tissue. However, the response of these teeth to an efficient spring auxiliary may lead to early eruption of the tooth in the labial sulcus, often in a matter of weeks. Planning the orthodontic strategy

The canines in group 5 may be offered four possible lines of treatment that are appropriate procedures for their resolution: to resolve the transposition to the ideal relationship • (Figures 6.43 and 6.46); to move premolar mesially (or incisor distally) into • the caninethelocation and align the canine between the two premolars (or between central and lateral incisors) (Figure 6.44); to use the canine for auto-transplantation into a prepared socket in its ideal site; to extract the severely displaced canine, incisor or premolar, depending on which has the least chance to be aligned with a good prognosis and leaving the deciduous canine in place.

• •

In the scenario described above for the I2C transposed lateral incisor–canine, with the canine labial to the lateral incisor and palatal to the central incisor, many practitioners facing this scenario will elect to accept the transposition of the canine and lateral incisor and prefer to align these teeth in their transposed order (Figure 6.44). On the other hand, a three-dimensional approach to its resolution is necessary if the orthodontist is to aim for complete correction of the impaction and the transposition (Figures 6.45 and 6.46). Prior to the surgical exposure, an auxiliary labial arch similar to the one illustrated in Figures 6.30 and 6.34 is prepared for use on the labial side of the arch. Its loop is formed in the horizontal plane and tied piggyback into the brackets over the heavy main arch. At the conclusion of the surgical episode, the horizontal loop is pushed superiorly and mesially and ensnared in the pigtail ligature, as close to the mucosal flap as possible, to apply a traction force. This force draws the tooth back along its original path between the two incisors, tipping it labially and distally as it goes. It is important to recognize that ligating the lateral incisor bracket into the archwire will tend to upright this tooth and, if the archwire is rectangular in cross-section, to apply labial root torque to it. This will immediately close the window of opportunity for the canine, by reducing the mesio-distal and labio-lingual space between the roots of the two adjacent incisors. It is far better to leave the lateral incisor without a bracket at this stage. Once the canine has moved labially and is palpable on the labial side of the ridge, the bracket is placed on the lateral incisor and this tooth may then be uprighted and labially root-torqued to clear the way for the canine to be drawn distally and into its place.

(b) (a)

(d) (c)

(e)

(f)

(g)

Fig. 6.45  (a–c) Intra-oral views of a 12-year-old male with left maxillary impacted canine. (d) Panoramic view of a 12-year-old male with left maxillary impacted canine and two over-retained second deciduous molars. (e) An axial cut from the CBCT at a level high on the roots of the anterior teeth shows the lateral incisor root displaced palatally, with the crown of the canine labial to it but palatal to the root of the central incisor. (f) This transaxial cut shows the canine to be located labial to the root of the lateral incisor. (g) The transaxial cut along the central incisor shows the canine crown on its palatal side. (h) A three-dimensional CBCT view from the palatal side shows the canine to be labial to the lateral incisor and encroaching on the palatal side of the central incisor. (i) Surgery must be approached from the labial side, care being taken not to proceed too far towards the crown tip of the canine in order not to damage the central incisor root. (j) Attachment bonding. (k) The flap is fully closed and sutured. (l) Traction is applied in a labial direction by engaging the auxiliary looped archwire. (m) Due to missed appointments, the patient was seen only six weeks later. The tooth has emerged through the oral mucosa! (n) The left side in the closing stages of treatment. (o–q) The completed case. The left canine has a slightly longer clinical crown than the unaffected right canine. This is more common for labial impactions and when the tooth is drawn through oral mucosa, as occurred in this case.

166  Orthodontic Treatment of Impacted Teeth

(h)

(i)

(j)

(k)

(l)

(m)

(n)

Fig. 6.45  (Continued )

After a relatively short period of time, often within a month or so, the canine bulges the labial tissue as the tooth is drawn labially, indicating that it has moved clear of any contact with the root of the lateral incisor and care should be exercised not to draw the tooth too far labially, since this will reduce the width of its labial bone cover and risk a long clinical crown. Therefore, at this point mesial uprighting of the lateral incisor should be undertaken to permit distal and palatal movement of the canine into its designated

location. The final alignment manoeuvres needed include uprighting of the tooth, with labial root-torque of the lateral incisor and palatal root-torque to the canine, which can usually be performed with considerable efficacy using a simple reciprocal torqueing auxiliary. Problems that may be encountered

Care should be taken in the construction of the auxiliary looped arches in these cases, so that when the loop is

Palatally Impacted Canines  167 

(o)

(p)

(q) Fig. 6.45  (Continued )

directed superiorly (following flap replacement and suturing) to ensnare the twisted steel ligature and apply the required traction, it is not excessively long. Ideally, its length should be a couple of millimetres short of the height of the sulcus at that site, otherwise the patient will suffer unnecessary after-pain and swelling due to ulceration of this very mobile and delicate oral mucosal tissue at the corner of the mouth. If the CPm1 transposed canine tooth is palatal to the line of the arch, the secondary effect of root contact with the premolar will rotate the canine’s root apex both mesially and palatally across the palate, in a wide-sweeping movement. The tooth will become ‘laid out’ immediately beneath the periosteum and the long profile of its root will be palpable under the palatal mucosa. Dehiscence of the cervical area of the palatal surface of the root will occur. The amount of unavoidable labial root-torque that will then be required will be extreme and beyond therapeutic reason. If the canine position is buccal to the root of the adjacent tooth and the tooth is brought buccally to the first pre­ molar or the lateral incisor, further buccal displacement

of its root will occur, with gross dehiscence of the buccal periodontium. Plane film radiography in these cases can easily distinguish which of the teeth is buccal and which lingual in relation to their crowns. But there is great difficulty in determining the interrelation between the teeth for the full length of their roots and in measuring the exact proximity of the root of one to the root of the other. Without this information, the choice of which treatment approach to follow cannot be made with any degree of certainty regarding its outcome. The information needed is now easy to obtain using cone beam volumetric CT scanning techniques. While each of the above four treatment possibilities will be recommended in specific instances, it becomes clear that the most likely and practical course, in many cases, will be to recognize and accept the transposition. The canine should be brought into the dental arch with the first and second premolars (or between central and lateral incisors) as its mesial and distal neighbours, respectively (Figure 6.44).

(a)

(b)

(c)

(d) Central incisor root

Crown of permanent canine

Root of deciduous canine

Roots of first premolar

First permanent molar (e) Root of lateral incisor

Crown of infraoccluded second premolar

Fig. 6.46  A group 5 canine with obvious transposition between the left lateral incisor and the adjacent canine. (a) The panoramic view taken from the CBCT. The canine is high and although its apex is slightly distal to that of the lateral incisor, its crown is clearly mesial. The lateral incisor crown is close to its normal place, but its root orientation shows a marked distal displacement. (b) The three-dimensional view from the front shows the mesial edge of the canine crown palatal to the central incisor and the distal edge labial to the lateral incisor. It will be clear that surgical exposure from the palatal side followed by traction to the palatal will torque the root of the lateral incisor even more palatally. (c) Seen from the left side, these interrelations are very clear and the deciduous canine is unresorbed. Incidentally, there is a distally tipped first premolar and mesially tipped first molar which are due to the severely infra-occluded and almost totally resorbed deciduous second molar. The impacted second premolar can be seen on the palatal side of these teeth. (d) Seen from above, the strongly divergent long axes of the three anterior teeth are evident. The canine is firmly wedged between the central incisor and lateral incisor roots. (e) The axial cut across the maxilla at this level shows the relationship between the crown of the canine and the roots of the central and lateral incisors, close to their apices.

Palatally Impacted Canines  169  ‘Machismo’ may be the driving force behind the decision to place the teeth in their correct order since, after all, we are orthodontists and this is the sort of challenge for which we have been trained. It is difficult to pass over an opportunity to display our initiative, dexterity and clinical excellence. Sometimes this is justified – but not often. It should always be remembered that the reversal of a transposition of necessity dictates that the two teeth have to pass by one another in an alveolar process whose buccolingual width is suitable for just one of them. True, when teeth are moved buccally or lingually on the ridge, there is a concomitant bucco-lingual expansion of the alveolar bone. Clinically, however, there is loss in bone height and a dehiscence may occur, particularly if oral hygiene is inadequate or, paradoxically, when toothbrushing is compulsively aggressive, as seen in some individuals. Furthermore, the biomechanics are difficult to perform with adequate root control, and root proximity may occur during the exercise. This could seriously compromise bone support on that surface of the two roots and some loss of attachment or root resorption may occur. Group 6 erupting in the line of the arch, in place of and resorbing the roots of the incisors.

•

The teeth that fall into this last category of impacted canines are only marginally displaced buccally or palatally, since most of them do not merely generate resorption, but actually move into the newly resorbed area where resorption of the incisor root has occurred. They may frequently, therefore, be difficult to palpate in the clinical examination. Similarly, the plane film radiographic methods used in determination of the exact three-dimensional location of the tooth will be very difficult to interpret because of the minimal bucco-palatal discrepancy of the two structures. The difficulty in positional diagnosis is markedly increased if there is little or no radiographic superimposition of the image of the crown of the impacted tooth on the remainder of the resorbed incisor root, which occurs when the resorption begins at the root end due to a superiorly placed and axially oriented canine. Why unerupted permanent teeth, in particular the maxillary canine, which are in close proximity to the roots of their neighbours cause resorption of these roots is unclear. Nevertheless, a cause-and-effect relationship is present and it has been conclusively shown that the resorption largely ceases when the impacted tooth is removed from the area of the affected roots [69]. The type of root resorption that is seen frequently in the routine orthodontic treatment of patients without impacted teeth, although worrying, is fairly insidious in nature. While it is a cause for wariness and caution in advising treatment, and for careful monitoring during treatment, it is not usually more than a marginal phenomenon, which stops when active tooth movement stops. The finding before or

during treatment may make the case for shortening the duration of appliance therapy and limiting its goals to the essentials only. However, when the cause of the resorption is very specifically related to the proximity of an impacted tooth, the character or type of resorption appears to be different, insofar as its conduct is more aggressive [69, 97]. It follows that, with the very survival of one or more teeth at stake, early diagnosis is crucial in order to initiate appropriate treatment. The condition constitutes one of the very few situations in which orthodontic treatment may be considered a quasi-emergency. Given the very special nature of this type of canine impaction, the difficulty in gaining an accurate picture of its extent, its rate of progress and the implications for its treatment, the next chapter will be given over to a comprehensive discussion of this important topic, which haunts even the most proficient orthodontic practitioner. Treatment duration It is probably stating the obvious that orthodontic treatment of a malocclusion with an impacted canine will take longer than the same malocclusion in a fully erupted dentition. Nevertheless, the presence of an impacted canine will clearly involve an extra dimension in the treatment which, by and large, cannot usually be addressed at the same time as other required orthodontic movements. As we have seen here, the initial part of treatment of these cases is the same as with any other case, in that alignment and levelling need to be achieved and this requires the use of one of today’s sophisticated fixed orthodontic appliance systems. At this point, passive and heavy archwires are inserted to fill the bracket slots in order to convert the whole appliance into a multiple anchor unit, incorporating all the teeth in one or both jaws. Further progress in the treatment of the overall malocclusion is placed on hold, while purpose-designed auxiliaries are introduced into the system aimed solely at reducing the impaction of the ectopic tooth/teeth. Thus, therapeutic attention is diverted away from the overall malocclusion and becomes focused solely on the impacted tooth and its resolution, until it is brought into alignment with the other teeth. Once the canine becomes an integral part of the alignment scheme, renewed attention is directed to bringing the overall malocclusion to its successful conclusion. There are then both subjective factors that influence treatment duration (i.e. factors inherent in the treatment provider) and objective factors (i.e. factors related to the three-dimensional geometry of the canine ectopy). Subjectively, a more inventive orthodontist with a flair for original design based on sound mechanical principles will usually be able to fabricate a device that is particularly suited to a given situation, while another may rely on standard “cookbook” solutions that require more frequent and more numerous adjustments. The more efficient the auxiliary, in terms of its traction force level and range of action,

170  Orthodontic Treatment of Impacted Teeth the fewer the visits for adjustment will be and the shorter the treatment duration. Objectively, there are factors that make for extended treatment times. These include the height of the impaction [98–100], the horizontal position of the crown of the canine to the adjacent teeth and the maxillary dental midline [99, 101], the sector of overlap of the incisors, as seen on a panoramic radiograph [62, 99] and the angulation of the tooth [98, 99]. Studies described in the literature have shown that orthodontic cases that exhibit impacted canines have been variously reported with treatment times of 26.3 months [101], 19.7 months [102], 22 months [103] and 25.8 months for unilateral cases and 32.4 months for bilateral cases [98]. While these treatment periods do not seem unduly long compared with many routine malocclusion cases, it should be remembered that many impacted canine cases have largely normal alignment and jaw relations, with adequate space within the dental arches and little in the way of malocclusion, apart from the aberrant canine. This being so, most of the treatment period will be concentrated on canine resolution, while the biomechanics needed for the remainder of the treatment will be minimal, straightforward and of short duration.

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172  Orthodontic Treatment of Impacted Teeth impacted maxillary canines. Am J Orthod Dentofacial Orthop 2001; 119: 216–225.   99.  Zuccati G, Ghobadlu J, Nieri M, Clauser C. Factors associated with the duration of forced eruption of impacted maxillary canines: a retrospective study. Am J Orthod Dentofacial Orthop 2006; 130: 349–356. 100.  Crescini A, Nieri M, Buti J, Baccetti T, Pini Prato GP. Orthodontic and periodontal outcomes of treated impacted maxillary canines. Angle Orthod 2007; 77: 571–577.

101.  Fleming PS, Scott P, Heidari N, di Biase AT. Influence of radiographic position of ectopic canines on the duration of orthodontic treatment. Angle Orthod 2009; 79: 442–446. 102.  Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003; 124: 509–514. 103.  Baccetti T, Crescini A, Nieri M, Rotundo R, Pini Prato GP. Orthodontic treatment of impacted maxillary canines: an appraisal of prognostic factors. Progress in Orthodontics 2007; 8: 6–15.

7 Impacted Teeth and Resorption of the Roots of Adjacent Teeth

Prevalence

175

Aetiology, diagnosis and prevention

177

Treatment

177

Evidence-based answers to questions regarding canine-related incisor root resorption

188

Resorption in relation to vitality of the dental pulp

189

Invasive cervical root resorption

197

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

174  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(d)

(c) Fig. 7.1  An extreme case of resorption. (Courtesy of Dr P. Svanholt.) (a) Most of the root of the left central incisor has resorbed in response to the advancing unerupted canine in an 8.5-year-old female. On the right side, the central incisor shows considerable root resorption, which has arrested with the eruption of the right canine. The right lateral incisor is congenitally absent. (b) 16 months later the incisor is shed, following continued resorption. (c) The canine has erupted spontaneously in the position of the lost incisor. (d) Prosthodontic reshaping and restoration has made the canine more acceptable in its new role as an incisor.

One of the essential characteristics of the deciduous dentition is that the roots of the teeth physiologically resorb with the development and progress of eruption of their permanent successors. This leads to a smooth transfer through the mixed dentition and on to the permanent dentition in the adolescent. In contrast, resorption of the roots of permanent teeth does not normally occur even when there are unerupted or crowded teeth in the close vicinity of these roots. Nevertheless, in relatively exceptional circumstances, pathological resorption of the roots of certain teeth can and does occur (Figure 7.1). The ‘aggressor’ teeth concerned are principally the maxillary canines and, to a much lesser extent, the mandibular third molars, which cause resorp-

tion of the roots of the maxillary lateral/central incisors and the mandibular second molars, respectively (Figure 7.2). Occasionally, too, one finds an aberrant mandibular second premolar developing low in the alveolus and with a strong distal tilt, with signs of resorption of the mesial root of the first molar (Figure 7.3). In each of these circumstances the crown of the impacted tooth is in close relation with the root of its neighbour – a situation not normally seen in other areas, where unerupted teeth are to be found at the level of the cervical area of the crowns of the adjacent teeth. Nevertheless, why resorption of the roots occurs routinely and physiologically in deciduous teeth and rarely and pathologically in these exceptional permanent teeth is not

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  175  understood. Since resorption of the roots of permanent teeth has wide-ranging clinical implications, a discussion of the various aspects of this phenomenon is clearly warranted. The present chapter will deal mainly with the resorption of the roots of erupted permanent teeth by unerupted adjacent teeth in its most common location and where its clinical implications are also the most significant, namely the permanent canine/incisor area of the maxilla.

Prevalence Fig. 7.2  Bilaterally impacted mandibular third molars associated with resorption of the roots of the adjacent second molars in an adult.

(a)

(b) Fig. 7.3  (a) A section of the panoramic view of a female patient aged 12 years, showing a late-developing second premolar with a distal inclination. (b) A periapical view taken 2.5 years later. The second premolar has caused large-scale destruction of the first permanent molar.

Based on the use of plane film radiography, which was the standard of care in the late 1980s, early studies of the incidence of discernible root resorption of lateral and central incisors adjacent to an impacted maxillary canine revealed that 12% of the cases in the sample studied were affected [1–4]. While this finding in itself was alarming, the authors of the papers and others were at pains to point out that because of the limitations of plane film radiography, this figure was probably understating the extent of the problem [5–6]. It will be readily understood that an unerupted palatal canine is to be found closer to the palatal surface of the incisor roots than to any other surface of the root and, should there be root resorption of the incisor, it is logical to assume that it will be palatal surfaces that are most likely to be affected. By the same token, a buccal canine may cause similar damage to the labial surface of the root of the adjacent incisor. Furthermore, because the canine generally approaches the root of the incisor from above and along a path which is at an angle to the long axis of the resorbing incisor, the resorption process usually affects the incisor roots obliquely. However, the labial and palatal surfaces of the roots of the teeth are largely impossible to image using traditional plane film radiography. It is these palatal and labial root surfaces which, if affected by resorption, are least likely to be recognized in plane film radiography until the extent of the lesion is sufficiently well advanced for it to alter the mesio-distal profile of the root or the relative radiolucency of its projected shadow. In line with technical progress in the development of diagnostic radiology, computerized tomography (CT) presented the window of opportunity that could overcome this bucco-lingual imaging ‘blind spot’, as discussed in Chapter 2. Accordingly, when a similar study of root resorption was undertaken by the same researchers [7], this time using spiral CT scanning in place of the earlier plane film radiography, it revealed signs of root resorption in almost half the cases affected by an aberrant/ectopic and unerupted maxillary canine. The actual figures in this study showed 38% of lateral incisors and 9% of central incisors affected to a greater or lesser extent, or 47% of affected individuals, in total. In a more recent study, in which the imaging modality used was cone beam threedimensional volumetric CT, the figures were higher still, with 66.7% of adjacent lateral incisors and 11.1% of adjacent central incisors affected (Figure 7.4). All those cases

176  Orthodontic Treatment of Impacted Teeth

(a)

(c)

(b)

(d) Fig. 7.4  A case for double misdiagnosis. (Courtesy of Dr N. Dykstein.) (a) A section of a panoramic view showing the right impacted canine superimposed on the lateral and central incisors. There is no apparent resorption of the incisor roots and the canine is palatal according to Chaushu’s method (see Chapter 2). (b) Two periapical views, with lateral tube shift intended for positional diagnosis, show the crown of the canine to be palatal to the central incisor root and no apparent root resorption. The canine is clearly palatally impacted. (c) From the CBCT images, a single paraxial cut of the canine and central incisor relation shows marked oblique and palatal resorption of the incisor root, and the canine can be confirmed to be on the palatal side of the central incisor. (d) From the CBCT images, two parallel paraxial (vertical antero-posterior) cuts, at an interval of 1.5 mm, of the canine and lateral incisor relation show marked oblique and labial resorption of the incisor root. The canine is on the labial side of the lateral incisor.

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  177  which exhibited central incisor resorption also showed resorption of the lateral incisors and in all the cases in the study close proximity between the impacted tooth and the incisor root was found [8]. Of course, in a significant proportion of the impacted canine patients in whom root resorption has occurred, these canines will eventually erupt and the roots of the incisors may suffer little or no further resorption in the long term (see Figure 6.34i, j). The eruption may be generated by a spontaneous change in the orientation of the canine in relation to the affected incisor root, as has been shown in anecdotal case reports [9] or during orthodontic treatment to create space for the canine by an appliance-generated movement of adjacent teeth [10, 11] as described in Chapter 6 (see Figure 6.19) or by the prophylactic extraction of deciduous [5, 12, 13] or permanent teeth (see Figures 6.19, 6.20).

Aetiology, diagnosis and prevention Over the years, clinicians have searched for clues, specific tell-tale features, which may indicate a high risk for incisor root resorption associated with an impacted canine. Obviously, the mobility of an incisor, in the absence of any signs of premature contact or symptoms of pain, would offer such an indication after the fact. However, the quest was for an associated anomaly or phenomenon in the dentition that could predict the occurrence of incisor root resorption before it occurred. Two studies that have investigated sexual dimorphism as a factor in the prevalence of this phenomenon have found that it occurs 3–4 times more frequently in females than in males [3, 8]. In relation to those cases in which the resorption has been extensive, accounting for more than a third of the incisor roots, both published individual and multiple case reports in the orthodontic literature and the author’s clinical experience indicate that, in its severest form, the phenomenon may be almost completely limited to females [14]. However, caution should be exercised in this regard since no formal study has been made of these more advanced resorption cases in contrast to those that may be minimally affected or where the extent of the damage is clinically insignificant. Suspicion regarding the presence of an enlarged dental follicle surrounding the impacted canine is another factor that has been investigated. Two studies have been performed by the same Swedish group and they found there to be no apparent cause-and-effect relation between an enlarged follicle and root resorption [3, 15]. Notwithstanding, other clinicians have expressed concern regarding a possible cause-and-effect relation between an enlarged follicle and root resorption [16, 17]. In light of the potential seriousness of the condition in the more extreme expression of its occurrence and its very much higher prevalence among females, this concern should be heeded, care taken and caution advised in the

Fig. 7.5  An enlarged follicle associated with severe resorption of the left lateral and central incisor teeth, in a 10-year-old female patient.

clinical context, despite the absence of confirmatory investigative studies. Good anecdotal examples of this may be seen in Figures 7.5, 6.15 and 6.36 and 7.10b, where unambiguous evidence of advanced root resorption of the incisor is seen adjacent to an impacted canine which is encompassed by an enlarged dental follicle. By and large, the overwhelming majority of cases where resorption has been confirmed show only a very mild and clinically insignificant degree of root loss, which at least partly explains why the condition requires the use of CT for the diagnosis to be determined definitively. However, it should also be remembered that all severely affected cases began the pathological process to this advanced state with very small initial resorption lesions which, had they been diagnosed earlier, may have markedly improved the prognosis. As we have pointed out in Chapter 6, a number of studies relating to the aetiology of palatal canine impaction have been published over the past 20 years, and these have established a firm link between palatally displaced maxillary canines and anomalous lateral incisors. However, when the prevalence of resorption of an incisor adjacent to a palatal canine was investigated, anomalous incisors appeared to be relatively immune to resorption. The phenomenon was found to be much more frequently associated with a normal-sized adjacent lateral incisor [6]. The conclusion drawn from this study was that the practitioner would be well advised to investigate the possible existence of resorption in any impacted canine patient who shows no lateral incisor anomaly. This is, therefore, a factor to be taken into consideration in deciding the strategy of the orthodontic treatment and the timing and sequencing of the individual tasks within the overall treatment plan.

Treatment When the diagnosis of impacted canine-related resorption of the incisor root is made, a lack of positive action on the part of the orthodontist or surgeon carries with it the

178  Orthodontic Treatment of Impacted Teeth danger of further resorption of the root of the incisor, for which these two practitioners may justifiably be held responsible. Furthermore, for as long as the impacted tooth remains in close proximity to the resorbing root, its continued destructive nature remains undeterred by any initial orthodontic alignment and space-gaining procedures that may be under way. The resorption process seen in many of these cases is rapid and it has been shown conclusively that it will advance significantly during the preparatory orthodontic phase [14]. On the other hand, and as has been pointed out earlier, the creation of space in the arch by moving the adjacent teeth, one or more of which are themselves being actively resorbed, might be a factor that may change the course of the canine, causing it to move away from the area and spontaneously erupt (Figure 7.6). Treatment options Three possible lines of treatment are available, and each has its advantages, disadvantages, unanswered questions and manner in which it influences the outcome.

(a)

Extract the impacted tooth

First principles in medicine dictate that, in order to successfully treat a disease, it is first necessary to remove the cause. In the present context, the cause of the resorption is the unerupted tooth, and its extraction carries with it the bonus of eliminating what may be a problematic impaction from the point of view of the provision of surgical access and the mechano-therapeutic difficulty. If this apparently logical line of treatment is followed, then a healthy canine will be extracted and the incisor with the resorbed root will be left in place. There is uncertainty as to whether the resorption process will continue and, in this compromised state, it may be reasonable to assume that the tooth has a reduced longterm prognosis. Given that it is unlikely that the incisor is in its ideal position and will thus need to be orthodontically moved into alignment, we need to know if the orthodontic treatment prescribed to achieve this will generate further resorption, potentially adversely affecting its prognosis still further. If an implant may be planned as the ultimate substitute for the extracted canine, considerable root movement of the resorbed lateral incisor will probably be mandatory in order to provide adequate space between the roots of the adjacent teeth. Alternatively, it may be wiser to attempt space closure. This would increase the length of time that orthodontic forces will need to be applied to this endangered tooth in its capacity as an anchor unit, and it may finally need to be splinted. Although it could be argued that perhaps a fixed cast bridge might reduce the amount of orthodontic movement to which the tooth will need to be subjected, it should not be forgotten that a resorbed lateral incisor will not make a good abutment. With a premolar in the canine position, the appearance may be compromised, and canine protection of the occlusion would not be present.

(b) Fig. 7.6  Root resorption, space opening and spontaneous eruption. (a) The left impacted canine has caused a marked oblique resorption, which has shortened the root in general and its distal side in particular. The central incisors have short rounded roots. (b) Following the orthodontic creation of space, the canine is seen to be erupting spontaneously.

Leaving the deciduous canine in its place, in the hope of its enjoying long-term survival in the present situation, is a real possibility. Given the degree of displacement of the aberrant canine, it is quite likely that the root of the deciduous canine has remained untouched by the normal resorption process affecting deciduous teeth, and, in these cases, the tooth may last for many years before implant and/or prosthetic replacement is needed. However, if its position needs to be altered, to enable the placement of an appearance improving restoration, then perhaps the required orthodontic movement may trigger the physiological resorption that has not occurred.

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  179  Extract the resorbed tooth

Extracting the ‘victim’ tooth may appear unfair, but must be considered the pragmatic choice if it is to be assumed that it has a poor prognosis. By its extraction, the treatment of the impaction is much simplified. Whether the deciduous canine will also be lost in the overall long-term planning strategy or not, the permanent canine would be aligned in the lateral incisor site, with the accompanying poor appearance and lack of a canine-protected occlusion [18]. To address the appearance, some orthodontists, prosthodontists and ‘aesthetic’ dentists might prefer aligning the impacted canine in its normal place in the arch, performing a one-tooth implant to replace the lateral incisor and to achieve a more normal, uncompromised appearance [19, 20]. Non-extraction

This is perhaps the most difficult and most heroic line of treatment, the more so since the literature offers little evidence for us to believe that the outcome can provide hope for a stable future. In the first place, without the expedient of extraction, the canine impaction is much more difficult to resolve since the tooth will need to be surgically exposed, attachment bonded and drawn away from the resorbing root in a separate orthodontic manoeuvre and before the more usual directional forces may be applied to bring it to its place in the arch. Second, the lateral incisor has a shortened root and will almost certainly require to be moved orthodontically. It may need to be splinted for the duration of its presumably reduced lifespan. Third, this incisor may become non-vital as a complication of the surgical exposure and may subsequently require root canal treatment. These factors appear likely to reduce its long-term prognosis still further. On the other side of the scale, it has been noted in the previous chapter that most palatally impacted canines and a minority section of the buccally ectopic canines are to be found in conditions of spacing and the mildest malocclusion, which may generally be considered to be non-extraction cases. Therefore, this approach potentially offers the prospect of the greatest gain for the patient and, if carefully managed, perhaps provides a way in which our worst fears will not be realized. It has been proposed that there is a fourth alternative in this situation – a ‘masterly inactivity’ or ‘wait-and-see’ option. An anecdotal series of three cases has been reported in which severe resorption of incisor roots had been noted adjacent to impacted maxillary canines, in each case [9]. The patients were followed up clinically and radiographically for a long period on a half-yearly recall basis, without treatment of any sort being provided. The canines eventually erupted, although the progress of the spontaneous resolution of the impaction generated further root resorption. It is a sine qua non that additional damage to the roots of the adjacent incisors was fully anticipated at the outset in these three patients, although the full extent of its expres-

sion could not be predicted. It is therefore reasonable to assume that the significant risk that these teeth would be lost during this observation period was accepted as a conscious decision. The dilemma that faced the clinicians was whether more damage would have been inflicted iatrogenically had the impacted teeth been treated by the orthodontic/ surgical modality. It is germane to attempt to answer this question in relation to group 6 impacted canines in general. To do so, it becomes necessary to examine the anatomical, surgical and orthodontic contexts of the dilemma and discuss the several factors that need to be carefully evaluated. The anatomical context

The first factor addresses the anatomical relationship between the impacted tooth, the resorbing tooth and their location in the alveolar process. In general, and having been the first to erupt some 3–4 years earlier, the adjacent incisor tooth is sited in mid-alveolus in the bucco-lingual plane. The impacted canine generally follows a high and mesially angulated path towards the root of the incisor. The approach of a palatal canine is on the distal or disto-palatal aspect of the root of the incisor, some way down the root from the apex (Figure 7.6a), while a buccal canine will be on the disto-labial side. Resorption occurs in the immediate area of the proximity of the two, and will only be discernible radiographically if it also affects the distal profile of the root of the incisor and is not hidden by the superimposition of the two teeth. In the most extreme cases, which are the context of the present discussion, the canine does not ‘side-swipe’ the root of the incisor, but rather comes down from above its apex, obliquely resorbing most of the full width of the root as it progresses inferiorly into the area vacated by the resorbing root (Figure 7.1) The canine is also thus situated in midalveolus. In one scenario, further progress finds the incisor root being resorbed obliquely with the destruction proceeding coronally at an alarming rate, until the crown of the still unerupted canine reaches one side of the cementoenamel junction (CEJ) of the incisor. At this point, no further resorption can take place, since the enamel of the tooth crown will not resorb but will act to deflect the progress of the canine to one side, where it may then erupt. The incisor does not then shed naturally, since the oblique resorptive process will have left a longish spicule of root which will hold the tooth in the alveolus, although the tooth may (but not necessarily) become a little mobile. The incisor crown is also likely to be displaced in the opposite direction to the canine’s new eruptive path due to the eruptive force of the latter acting obliquely on one side of the incisor’s CEJ. The surgical context

If we are to try to change the course of what appears to be inevitable, it is logical to attempt to distance the canine

180  Orthodontic Treatment of Impacted Teeth from the resorption area as early as possible, which is immediately after the diagnosis has been established. In the orthodontic/surgical modality of treatment, this means that surgical access must be provided and an attachment bonded in order that orthodontic forces may be applied direct to the tooth to effectively draw it away from the immediate area by diverting it from its present path. Because of the intimate relationship between the crown of the impacted tooth and the resorbing root apex of the incisor, accuracy of positional diagnosis is vital, if simultaneous collateral surgical damage to the root area of the incisor tooth is to be avoided. A wide flap is reflected, the crown of the impacted tooth is identified immediately beneath its thin bony covering and only the smallest opening is made in the bony crypt to expose that area of the crown of the impacted tooth most superficially accessible and most distant from the resorption site. No attempt should be made to seek out the root apex of the incisor, or even to gently probe the area (Figure 7.7). It will be appreciated that a good radiographic diagnostic technique, specifically CT views employing a cone beam volumetric machine, should be considered an essential diagnostic aid that will contribute enormously to determining the preferred exposure site as accurately as possible. From these, the direction in which the tooth must be moved away from the sensitive resorption area will be decided. This may be in a labial direction or in a palatal direction, depending on the labio-lingual location of the crown tip vis-à-vis the residual root end. Exposure of the crown, clearance of the follicle and bone removal to the maximum width of the crown and down to the CEJ in this situation, as recommended by Kokich for the more accessible palatal canines [19], is strongly contraindicated in these cases, since it will surely inflict unnecessary trauma to the resorption area and lead to devitalization of the incisor. In these highly sensitive situations it is recommended that the area of crown to be exposed should be on an aspect of the crown as far as possible from the site of resorption. It should be exposed minimally, with an opening only large enough for placement of the small eyelet, while permitting adequate haemostasis during the bonding procedure (Figure 7.7j, k). An eyelet attachment is then bonded to the tooth in the most accessible site available on the crown surface, and the twisted steel ligature is made to point in the direction that traction will be applied. The full flap is then sutured back to its former place, leaving only the ligature wire peeking through it, either at the sutured edge or, preferably, to piercing through the flap in the direction that traction has been determined. Primary closure is essential in these cases to protect the wound from damage or infection of the vital tissue at the root end of the lateral incisor. If, following the earlier resorption, the canine crown tip has crossed over to the labial side of the incisor roots, a labial resolution will

be required (Figure 7.8). In this case, labial traction will be needed, and this will mean that a labial surgical approach will be preferred, with the attachment bonded in a convenient place on the crown and its ligature protruding through the flap, high in the labial sulcus. If the tooth is palatal, a palatal approach will be dictated, with the palatal aspect of the tooth being exposed and an attachment bonded there. Traction will need to be directed in the horizontal plane in a posterior horizontal direction. The orthodontic context

As we have discussed in the previous chapter, directional traction must be designed to meet the demands of each individual case. Nowhere is this more crucial than for the cases that we are discussing here. Ballista springs [21] and light auxiliary arches [22] are particularly suited to the provision of force in a palatal direction. They are specifically useful when designed to produce forces in a labial or vertically downward direction, but may be directionally modified to include apical or mesio-distal force components which are sometimes helpful in elevating a canine over the root apex of an incisor or to draw it in a wide labial sweeping movement around the root of the adjacent tooth. When a canine needs to be moved posteriorly in the horizontal plane, a trans-palatal arch carrying three or four soldered loops may be used. Elastic thread may then be tied between the steel pigtail wire, which is ligated to the eyelet attachment on the canine, and that soldered loop which is most suitably placed to provide the optimum directional pull. Exploiting the lingual cleat of a molar band may sometimes be adequate in many of these cases. Using these simple and mainly custom-designed accessories, rapid movement of the crown of the impacted canine may be effected to widely separate it from the resorption area. It is quite clear that the approach of Kokich [19] recommended for the open surgical exposure of an impacted canine uncomplicated by resorption of the root of the incisor cannot be used when the canine crown is in close association with a resorbing incisor root. In that approach, bone and follicular tissue are completely eliminated around the full width of the crown of the buried tooth, down to the CEJ, and a large circular opening is made in the flap, with placement of a periodontal dressing to maintain patency. To attempt this in the present context would seriously endanger the vitality and survival of the resorbing incisor. Acceptance of the rationale for Kokich’s method (see description in Chapter 3) precludes any remedy for the case where canine-related incisor root resorption is present, and one can only counsel ‘not to interfere with Mother Nature’ in its hoped-for trade-off between the possibility of spontaneous eruption and the near certainty of additional collateral resorption [19] as illustrated in a series of three cases [9].

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 7.7  This case was treated before the introduction of cone beam computerized tomography. (a–e) Initial clinical intra-oral views of the dentition. Note deciduous left maxillary canine in place and space loss in the left mandibular quadrant following early extraction of the deciduous second molar. (f) Section of the lateral cephalogram to show a single labially ectopic maxillary canine. (g) A section of the panoramic view shows the canine to superimpose on the lateral incisor root. It appears that most of the root of the lateral incisor has been resorbed. (h, i) The periapical views confirm labial impaction. (j) Surgical exposure is minimal to reveal only the disto-labial aspect of the tooth. The camera angle shows the canine to be in the same long axis of the incisor, obviously moving into the freshly resorbing area as it develops. (k) An eyelet is bonded to the disto-labial corner of the crown of the tooth. Its pigtail ligature is seen to hang loosely. Traction cannot be made direct to the archwire, for fear of resorbing more of the incisor root. (l, m) An open surgical exposure is strongly contraindicated here, since it would leave the sensitive apical area of the incisor exposed. Full flap closure is made to cover the entire exposed area, with the pigtail ligature taken through the oral mucosa, high up in the sulcus. In this situation, it cannot be taken through attached gingiva. The long loop of the light auxiliary labial archwire lies horizontally, in its passive state, ready for activation. (n, o) The loop is flexed upwards and engaged by the pigtail ligature, which ensnares it. This produces a light and highly controllable labial force to move the unseen canine. (p) At one month post-surgery, the tooth has exited the oral mucosa. (q) At two months post-surgery, the tooth has cleared the root of the lateral incisor and a distal direction of traction is applied, with a measured piece of cut tubing holding the space between incisor and premolar. The disto-labial position of the eyelet permits this movement without incurring unwanted rotation. (r, s) At three months post-surgery, the tooth has moved opposite its place in the arch and a regular bracket is substituted, in preparation for the finishing phase of treatment. (t) At five months post-surgery, finishing procedures are in progress. (u) Periapical radiograph checking for the status of root resorption indicates considerably more root than realized at the outset. The appearance is typical of an oblique resorption, in which the labial side of the tooth has been ‘shaved’ off, leaving a long spicule of palatal root. (v–z) The final clinical result. In view of the severity of the resorption process, meticulous attention to root uprighting and torqueing was considered inappropriate at the time. (a’–f’) Periapical and panoramic views of the immediate area, at the end of treatment. (g’–i’) Patient seen 7.6 years post-treatment. (j’, k’). Periapical and panoramic views of the dentition 7.6 years post-treatment, showing no change in the condition of the root of the resorbed lateral incisor. There is no hypermobility of the tooth and the removable retainer was discarded three years ago.

182  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(i)

(j)

(l) (k) Fig. 7.7  (Continued )

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  183 

(m)

(n)

(o)

(p)

(q)

(r)

Fig. 7.7  (Continued )

(s)

(t)

(v)

(u)

(x)

(w)

(z)

(y) Fig. 7.7  (Continued )

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  185 

(b')

(a')

(d')

(c')

(f')

(e') Fig. 7.7  (Continued )

186  Orthodontic Treatment of Impacted Teeth

(h') (g')

(i')

(j')

(k') Fig. 7.7  (Continued )

Clinical experience with a disproportionately large number of these cases over the years, employing the closed exposure approach to surgery, with the application of directional force that has been described in this text and supported by the findings of an investigative study [14], has permitted different conclusions to be drawn. During the past 35 years or so, a conscious and standardized effort has been made during the surgical episode to expose only the

smallest area of available enamel surface for these teeth and then to apply immediate and efficient light directional orthodontic traction. The patients have been rewarded with an eruption process that has occurred with considerable speed, and with periodontal and aesthetic outcomes that largely make the previously impacted teeth indistinguishable from their normally erupting antimeres and from other untreated teeth (Figures 7.7 and 7.8).

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  187 

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 7.8  (a, b) Periapical views of the group 6 canine with associated severely resorbed central incisor. (c) A variant of the auxiliary labial arch to move a tooth buccally. The loop is drawn upwards and into the sulcus to ensnare the pigtail. (d) Four weeks later, the pigtail has elongated, indicating progress of the canine. (e) After several adjustments over a three-month period, the eyelet attachment of the canine becomes visible. (f, g) Clinical and periapical views of the final stage of treatment. Note cessation of root resorption of the incisor and the gingival condition of the canine. (h, i) Lateral and anterior views one year after completion of treatment.

188  Orthodontic Treatment of Impacted Teeth

(h)

(g)

(i) Fig. 7.8  (Continued )

Evidence-based answers to questions regarding canine-related incisor root resorption When faced with the challenge of the patient whose impacted maxillary canines are associated with extensive resorption of the root of the adjacent incisor, several questions arise. These may be enumerated as follows: 1. Will the resorption process continue after the canine impaction is resolved? 2. After resolution of the impaction, will the resorbed tooth suffer further resorption if it is subsequently moved orthodontically into its ideal position, including the likely need for root movement? 3. Will the introduction of calcium hydroxide into the root canal of the resorbed tooth [23] be a necessary preventive remedy to help to eliminate further resorption? 4. Will rigid splinting of the severely resorbed incisor be an essential element of a successful outcome? 5. Can the patient reasonably expect a long-term prognosis for the resorbed incisor? With no guidance in the literature until recently, other than anecdotal reports, the practitioner needs to make

decisions that are based on clinical experience with lesser problems or what may appear to be common sense. In the more severe resorption cases, it may be that there is little to lose, since non-intervention may well result in exfoliation of the resorbed tooth and eruption of the impacted tooth into its place (Figure 7.1). As succinctly stated in correspondence with the author: ‘it is from the treatment or non-treatment of these extreme and apparently hopeless situations that we may sometimes find answers’ (Kokich, personal communication). If enough of these cases may be found to establish a database, then evidence-based and reliable conclusions may be reached that may set the foundations for valid treatment protocols to guide us when facing similar challenges. With this in mind, and to fully address the above five questions, a study was undertaken of severe resorption of the roots of 21 incisor teeth, each due to an associated impacted maxillary canine, in a group of 12 patients [14]. Radiographs of each of the cases were analysed and compared at four distinct stages, namely, T1 prior to the commencement of orthodontic treatment, T2 at the time the canine was distanced from the resorption site, T3 at completion of the overall orthodontic treatment and T4 at a follow-up

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  189  visit, which was at least one year later and up to 26 years post-treatment. The conclusions from this study may be listed as follows: Resorption of the roots stops when the canine impaction • has been resolved. Subsequent movement of the resorption• affected teethorthodontic does not generate further resorption The incisor teeth with severely resorbed roots have a high • survival rate. Prophylactic root canal therapy is contraindicated [23]. • The teeth remain vital. • The teeth retain their colour and appearance in the long • term. The teeth show a very low degree of mobility and an • improvement in bone support, following post-treatment retention. Splinting of the resorbed teeth is not usually necessary, although it is often recommended as the means to retain the alignment of the teeth at the completion of the orthodontic treatment.

•

These results may therefore lead us to conclude that a tooth that has suffered advanced root resorption from this cause can usually be treated conservatively with a fair prognosis (Figure 7.10). It is emphasized that these conclusions do not apply in cases where there has been root resorption from other causes. Reducing the time taken in the first stages of treatment and avoiding the customary pre-surgical preparation of space in the arch for the impacted tooth are considered by the authors to be crucial. They strongly advise that distancing the canine from the resorption area should take precedence over all other orthodontic movements, even before space opening and even if this means leaving the newly disimpacted tooth in limbo for several months while space for it is subsequently being prepared in the dental arch (Figures 7.8, 7.9). Finally, they issue a fairly optimistic assessment of the longevity of the resorbed teeth and encourage the orthodontist not to underestimate the prognosis of even those with very short roots. At the end of treatment, when the appliances are removed, the teeth may exhibit a fairly high degree of mobility, and this will undoubtedly be so for the more seriously affected incisors. However, after a few months of retention the teeth become very firm. It should be remembered that the resorption process is usually oblique, with a strong vertical component, which means that a long spicule of root may often remain firmly ensconced in the alveolar bone.

Resorption in relation to vitality of the dental pulp It is pertinent at this point to discuss the clinical histopathological implications of root resorption that has involved the pulp chamber. When an impacted canine is situated in close

relation to the apex of the incisor root, resorption begins at the apex and the pulpal tissues are immediately involved, but the vitality of the tooth is unaffected. The advance of the impacted canine goes hand-in-hand with the resorption process of the incisor, which may continue until much of the root is destroyed, but the pulp remains vital. Similarly, when the canine is associated with a severe resorption on one side of the root of the incisor, be it mesial or distal, palatal or buccal, the pulpal tissues will inevitably become involved with the resorption process at some point. Does this mean that the tooth will lose its vitality? Is it incumbent on the practitioner to perform root canal treatment? If this were so, then it would be necessary to restore the resorbed area of root with some form of filling material in addition to the normal procedures involved in the endodontic treatment. The situation may be likened to that of a shedding deciduous tooth. For both the deciduous tooth and the resorbing permanent incisor, the resorptive cellular layer or resorptive front fenestrates through to the inner pulpal surface of the root and meets the odontoblasts that line that surface. The periodontal and pulpal tissues merge and metaplastic changes occur in the pulpal tissue. Its vitality remains unchallenged, with neither inflammation nor pain. This is one reason why, when resorption is so severe as to penetrate the pulp in the apical or lateral areas, the process is asymptomatic and root canal therapy is not indicated. Once the impacted tooth associated with the resorption process is moved away, the resorption will generally cease and the affected tooth can usually be moved orthodontically without any significant danger of renewed resorption. Dental traumatologists recommend elective root canal treatment as a means of limiting or preventing the resorption that occurs frequently following trauma to incisor teeth [23], but there is no evidence that the same treatment will minimize or eliminate the resorption caused by the proximity of an unerupted canine. When the canine has caused root resorption of the lateral incisor close to the CEJ and to the gingival crevice, there is the danger of perforation, recession and secondary caries in the resorbed area. It would seem to be desirable to orthodontically extrude the tooth to expose the resorbed area and then to restore it, with or without endodontic treatment, as indicated by the depth of the lesion. However, this type of resorption is almost always oblique and extends a long way up the root, as dictated by the eruption path of the canine. Thus, if the resorbed root area is large, then the tooth will most likely need to be extracted. If it is small, then a flap operation will be needed to make good the defect, using a glass ionomer restoration. Since reattachment to the restoration cannot occur, the incisor will need to be actively erupted and its crown shortened, until the most apical extremity of the restoration becomes supra-crestal and a gingival crevice of normal depth is attained.

190  Orthodontic Treatment of Impacted Teeth

(b) (a)

(c) Fig. 7.9  Management of the rapid progress of resorption. (a) At age 8.5 years, the panoramic view shows a normally developing dentition, with enlarged follicles around the crowns of the maxillary canines, which are otherwise in a normal relationship with the lateral incisors at this age. No resorption is visible. Since treatment was not appropriate at this time, the patient was advised to return for follow-up a year later. (b, c) The patient returned two years later and new panoramic and periapical views show marked resorption of the central incisor and signs of an oblique resorption of the lateral incisors. (d, e) The patient was sent for CBCT imaging, which demonstrated the loss of root contour (resorption) in the horizontal and vertical planes. (f) Following diagnosis and treatment planning, a soldered trans-palatal arch with a Nance acrylic button was placed for the purposes of anchorage. (g–j) Two maxillary premolars and the second deciduous molar were extracted at the time of surgical exposure of both maxillary canines. The right canine was an uncomplicated impaction. The left canine was exposed minimally on its buccal aspect and an eyelet with a pigtail steel ligature was placed. The full surgical flap was sutured back and immediate traction made to the hook on the molar band. (k) At one month post-surgery, distal movement of the tooth has been rapid and the eyelet can be seen through the translucent gingiva. (l) At four months post-surgery, the remainder of the teeth have been bonded and the canine has reached its place in the arch. (m) A radiograph taken at this stage to monitor further resorption shows no further deterioration. (n–p) The alignment and occlusion on the day the fixed appliances were removed. (q) At one year post-treatment, the periapical radiograph shows complete elimination of the resorptive process, with a return of the lamina dura and good bony fill-in and texture. (r, s) At one year post-treatment, the clinical view comparing the canine on the side involved with the resorption and that of the opposite side, where a simple routine impaction was treated, shows them to be indistinguishable from one other and also from any normally erupting canine. The gingival contour is excellent, the clinical crown is of normal length, there is a good width of attached gingiva on each and the appearance is close to ideal – a tribute to accurate positional diagnosis (imaging), skilled execution of the closed eruption technique (surgery), with carefully planned directional force application (orthodontics).

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  191 

(d)

(e)

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Fig. 7.9  (Continued )

192  Orthodontic Treatment of Impacted Teeth

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(i)

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Fig. 7.9  (Continued )

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  193 

(p)

(q)

(r)

(s) Fig. 7.9  (Continued )

In summary, therefore, it is important to realize that even severely resorbed teeth need not be extracted and may well be treated conservatively to successfully occupy an important place in the scheme of the dentition for a long time, often for years to come. For this to happen, accurate 3-D localization of the tooth and its surrounding structures is mandatory, in order to guide the surgeon in identifying the exact position of the impacted tooth vis-à-vis the resorbing root face. Accurate positioning and designing of the soft tissue flap, minimal precision bone removal and attachment bonding then follow and a closed exposure procedure is absolutely essential if the vitality of the resorbed tooth is to be retained, if the canine can be diverted from its progressively worsening threat to its immediate neighbours and if both teeth are to be profitably salvaged from this debacle. Emphasis is placed on the surgery being undertaken very early in the treatment in order to permit immediate orthodontic traction to distance the tooth from the resorbing incisor root, in a planned direction. This will effectively and almost completely eliminate the resorptive

process. The orthodontist’s attention should then turn to treating the existing overall malocclusion and creating space for the canine in the dental arch, which may take several months. During this time, the canine remains in a ‘neutral’ location on the buccal or palatal side, depending on the escape route that will have been taken in its movement out of harm’s way. Following full correction of the canine ectopy and ‘fine-tuning’ of the alignment of all the teeth, reparative periodontal procedures are generally superfluous and the long-term prognosis of the canine will be excellent. In many cases, even those with a much reduced root length, the adjacent incisor usually enjoys a fair to good prognosis and, for the most part, the tooth will last the patient well into adulthood. The gingival architecture, crown lengths and dental alignment should be such that even a dental colleague will be able to recognize neither the previously impacted canine nor the incisor that was affected by root resorption. Appearance of the anterior dentition will be unsurpassed in comparison to any other form of treatment (Figures 7.9 and 7.10).

194  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 7.10  Enlarged dental follicle and root resorption. (a) Periapical radiographs of the canine areas, taken at the initial consultation of a 10-year-old female. The films show enlarged follicles around the unerupted canines. Aside from this and the obvious crowding, it was considered too early for orthodontic treatment per se, and the patient was placed on one year recall and sent for extraction of the left deciduous canine and first molar teeth in the hope that this might encourage the canine to improve its position. (b) Thirteen months later, the new periapical views show extremely aggressive root resorption of both lateral incisors. Orthodontic treatment was advised urgently. (c–e) The initial clinical photographs show a class 3 relation of the teeth on a mild skeletal class 3 base. Crowding was present in the maxilla but not in the mandible, and it was considered a non-extraction case with the possible option of dental compensation or later surgical advancement of the maxilla. (f) The right canine was palatally impacted, and it was exposed and attachment bonded immediately after placement of the fixed appliance. Note that this was done before space was made available in the arch in order to separate the canine from the incisor and, hopefully, thereby to prevent further resorption. (g) An active palatal arch was placed immediately after suturing of the closed exposure full flap and is seen in its passive state at a distance from the palatal mucosa. The pigtail ligature protrudes through the middle of the sutured flap, opposite the buried tooth. (h) The active palatal arch has been raised up close to the palatal mucosa arch and held in place by ensnaring it in the pigtail ligature. This produces a vertical force on the unerupted canine, away from the roots of the incisor. (i) The left canine was buccally impacted and treated with a closed surgical procedure. This picture shows the latter stages of its buccal and distal resolution, using a long rectangular lever arm. In the immediate post-surgical stage, a labial auxiliary arch was used, as in (j–l). The completed case shows the dental compensation for the skeletal class 3 relationship and all teeth in place. Overall gingival condition and contour are good, but the left maxillary canine shows an increased crown length. (m–o) At 3.5 years post-treatment, the gingival condition has remained largely unchanged. A bonded multi-strand wire splint functions as an orthodontic retainer and splint. (p) The monitoring periapical views taken following resolution of the impactions show severe resorption of both lateral incisors. There is no apparent bone support for the right and only a millimetre or so for the left lateral incisor. Should these teeth be removed? (q) Similar films at the time that orthodontic movement of the lateral incisors had been completed show minor improvement in the bone ‘support’ and obliteration of the pulp on the right side. (r) At debonding of the appliances and placement of the bonded multi-strand wire splint, corresponding to nine months after cessation of incisor movement, a new lamina dura and bone condensation have appeared around the root ends of the affected teeth. (s) At 3.5 years post-treatment, further bone support has been generated.

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  195 

(h) (g)

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(k) Fig. 7.10  (Continued )

196  Orthodontic Treatment of Impacted Teeth

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(s) Fig. 7.10  (Continued )

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  197 

Invasive cervical root resorption Quite unrelated to the presence of an adjacent impacted tooth, resorption of the cervical area on one side of the root of a tooth has been referred to in the literature and is described as a specific, recognizable and recurring entity in its own right, apparently unrelated to the factors that cause the more usually diagnosed resorption. Potential predisposing factors have been identified as trauma (15.1%), intracoronal restoration (14.4%), surgery (5.4%) and intracoronal bleaching (3.9%), while a significant number (16.4%) of the affected teeth showed no identifiable cause, but the most common link of this unusual phenomenon was found to be a history of having had past orthodontic treatment. This treatment had been provided for patients who comprised 24.1% of the affected teeth in the study sample [24–27]. By themselves, none of these factors or the condition itself would be relevant or appear to merit discussion in a book on impacted teeth. However, among the orthodontically treated cases in that study, arrested eruption was seen in five of the teeth concerned. Indeed, a number of instances of resistant impacted teeth have been seen by the present author in association with invasive cervical resorption. The resorption referred to here specifically affects the impacted tooth itself and not the adjacent incisor. The diagnosis of invasive cervical root resorption can easily be missed or mistaken for the ‘interproximal cervical burnout’ seen on periapical and bitewing radiographs (Figure 7.11). A typical narrative then follows. Presuming a healthy periodontium and root surface integrity, the tooth

Fig. 7.11  An impacted canine has resisted attempts to mechanically erupt it. The periapical film shows a distal resorptive lesion burrowing into the root of the tooth in its cervical region. The point of entry and the loss of integrity of the lamina dura are clearly seen.

is exposed, an attachment bonded and traction applied in the usual manner. The tooth does not respond and the orthodontist applies greater traction force. This is repeated for several more visits and increased traction force. The tooth still does not respond, but the neighbouring teeth show signs of anchorage loss, with the occurrence of intrusion and the creation of an open bite (Figure 7.12). The orthodontist then assumes the tooth to be ankylosed and refers the patient back to the surgeon. The surgeon’s intention is to re-expose the tooth and free the presumed ankylotic connection by seizing the tooth with a forceps and applying a force sufficient to break this direct connection to the bone – a luxation. However, with the tooth reexposed and in full view, it is found to be mobile – sometimes even excessively mobile, if the orthodontist had indeed increased the traction force, in the usually many months of unproductive traction. If we can assume that the direction of applied orthodontic force had been appropriate to the resolution of the impaction and that ankylosis is clearly not a factor, then there must be a flaw in the periodontium which does not permit the tooth to respond, since a healthy, complete periodontal ligament is a precondition for tooth eruption. It is in these circumstances that a tentative diagnosis of invasive cervical resorption may be determined by default. Identification is not easy because it entails subgingival probing and periapical radiography at different angles. Many of these lesions occur in buccal or lingual areas of the root surface which do not show up in plane film radiography. However, a careful examination of the relative radiolucency of the crown of the tooth may provide the clue to the presence of the condition (Figure 7.13). It may be seen as an atypical caries-like shadow, ballooning into the dentine, undermining the enamel of the crown of the tooth and, because the tooth is still unerupted, it is easily passed over or presumed to be an artefact. Unless the tooth is extracted, only a periodontal surgical flap will reveal the lesion. It seems that the invasive nature of this condition destroys the normal structure and integrity of the periodontium at this site and does not permit the histological changes normally associated with the application of orthodontic force to occur and to generate the desired tooth movement. Cervical root resorption is initiated by a local inflammatory process, indicating that infection, or perhaps trauma, is a necessary aetiological factor. A defective junctional epithelium has also been blamed, although assumptions are largely speculative [28]. An experimental model for cervical root resorption was developed to study the significance of the junctional epithelium in the prevention of cervical resorption [29]. The researchers reflected a muco-periosteal flap on the mesial and distal sides of the canines in the upper and lower jaws, respectively. The crestal alveolar bone with adhering periodontal membrane and superficial cementum and dentin was removed with a round burr, to

(a)

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Fig. 7.12  (a) Anterior section of the pre-treatment panoramic view shows the right canine to be palatally impacted and superimposed on the anomalous lateral incisor. The left canine has a complete root, there is no space problem to account for its non-eruption and it is in a direct line to its appointed place in the arch. The cervical resorption on the mesial aspect has affected approximately half the root length, although unnoticed at the time of commencement of treatment. (b) Periapical view of the left canine clearly shows the lesion and the disappearance of the lamina dura. (c–e) Intra-oral views of the dentition after 28 months of treatment. An orthodontic appliance is present in the maxilla, with molar bands and brackets on the first premolars, incisors and right canine, whose palatal impaction has been resolved. The left canine has not responded to treatment. The application of traction to the left canine has caused intrusion of the adjacent teeth and an open bite which is larger on the left side, indicating loss of anchorage. The second premolars are unconnected to the orthodontic appliance and have remained in occlusion. (f) Periapical view taken 28 months into treatment shows the progress of the resorptive process into the crown of the canine and extending widely to involve most of the root. (g–i) Successive axial (horizontal) cuts of the CBCT scan, taken 28 months into treatment, show the lingual and mesial radiolucency characteristic of resorption process. The slice represented in slice (g) is completely encircled in crown enamel, but slices (h) and (i) show the external portal of entry of the lesion on the palatal side. (j) The three-dimensional view from the buccal aspect shows the canine to have a complete and unblemished root surface. (k) From the palatal side, the three-dimensional view clearly shows the resorption process to have affected the entire palatal aspect of the tooth as far as the apex.

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  199 

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(j) Fig. 7.12  (Continued )

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200  Orthodontic Treatment of Impacted Teeth

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(f) (e) Fig. 7.13  Invasive cervical resorption with a history of early trauma. (Courtesy of Dr Joel Becker.) (a, b) The pre-treatment panoramic and cephalometric views (anterior portions presented only) show an impacted central incisor with a short root, very high in the anterior maxilla, at the level of the anterior nasal spine and floor of the nose. The crown appears ‘empty’ and there is a break in its labial cervical contour. (c) After space had been made and an attachment placed at surgery, traction was applied to no avail. (d, e) Frames from the paraxial views of the CBCT show the break in the enamel layer of the gingival third of the crown and the low density of the dentine area, compared with the similar view of the erupted incisor. The root of the tooth is not visible because of the angulation of the tooth vis-à-vis the vertical cut. (f) The sectioned tooth clearly demonstrates the labial cervical crown/root defect. The dentine is completely resorbed and the enamel remains as an unsupported hollow shell. There is a thin and continuous partition of secondary dentine separating the resorbed area from the pulpal tissue, which was vital.

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  201  a depth of 2 mm in an apical direction. In half the teeth in the sample, the exposed dentine was covered with thin polycarbonate foil. Eight weeks later, the dentine surface had not developed an epithelial cover but exhibited numerous resorption cavities associated with moderately chronically inflamed and cell-rich granulation tissue. Actively resorbing odontoclasts and osteoclasts were seen along the dentine and crestal bone surfaces, respectively. During the same period, the dentine surfaces of the non-foiled teeth were all covered by a dense squamous epithelium. The originally denuded dentine surfaces that did not come in contact with mucosal or periodontal connective tissue showed cementum repair in the more apical areas of the root. The reparative connective tissue that appeared under the epithelial coverage was cell-rich and presented a mild chronic inflammation. In the cervical area, where the damage was adjacent to the oral environment, repair was characterized by epithelial proliferation down the side of the root to epithelialize the exposed dentine and thus to produce a long junctional epithelium. However, before the proliferation was fully accomplished to completely cover all the dentine surface, there were sites of initiation of root resorption which were later inhibited once epithelium covered them. The authors of the study concluded that chronic inflammation in the granulation tissue, when in contact with the dentine, prevents the marginal gingival epithelium from forming a protective cervical cell layer in an angular defect and thus generates the resorption process. While this study helps us to understand why the lesion is essentially cervical, it should be remembered that, once initiated, the unchecked progress of the resorption process will see it extend into both the root and the crown. In the crown it may progress without symptoms of pain to destroy virtually the entire dentine content, with the exception of the layer of pre-dentine immediately covering the pulp tissue (Figure 7.13f). The pulp remains protected by the predentine until late in the process because pre-dentine is thought to possess an enzyme inhibitor (anti-invasion factor) present during the organic phase of pre-dentine formation. The resorption starts at what becomes a portal of entry on the root surface and continues to mushroom into the dentin (Figure 7.11). When the pre-dentine is reached, the resorption proceeds laterally and in an apical and coronal direction, progressively enveloping the root canal [30, 31]. The anti-resorptive effect of the pre-dentine and of the outer surface of the enamel causes the resorption to stop, leaving a narrow layer of dentine and pre-dentine around the pulp and giving it an irregular radiographic appearance. The enamel is thinned down, leaving only an outer, rodless, translucent layer and producing a characteristic ‘pink tooth’ due to the vascular pulpal and resorptive tissue [32]. Unless there is access to the oral environment from a periodontal defect or generalized periodontal disease, the portal of entry is not to be found in a more apically location along

the root, since an area of incomplete epithelial coverage that is isolated from direct access to the mouth will typically repair with a cementum deposit on the root surface. However, a resorptive lesion with a cervical portal of entry, will spread progressively coronally and apically to eliminate much of the root substance (Figures 7.12 and 7.14). A majority of the existing literature on the invasive cervical root resorption refers to its occurrence in relation to non-vital teeth which have undergone intracoronal bleaching. It seems that there is a high prevalence of invasive cervical resorption in previously bleached teeth in the years that follow, although the cause of the problem is from within. Non-vital bleaching is performed by sealing a bleaching agent into the prepared pulp chamber and the most coronal portion of the root canal (the remainder of the root canal will have already been sealed off by the root canal filling). The bleaching agent may leak through the more coronal accessory root canals of the tooth and its effect on the immediately adjacent cervical area is to generate a resorptive process, which is typically annular and uniform around the neck of the tooth [33]. Invasive cervical root resorption from this cause, therefore, is indeed beyond the context of this book. However, a successfully treated impacted tooth in the years that follow may sometimes become relatively infra-occluded and it is important to make the differential diagnosis of its cause. One of the possibilities is post-bleaching root resorption of the tooth, if it had been root-treated as described above. Another is vertical relapse that occurs when apically repositioned flaps are used to expose an impacted tooth [34]. This is due to a realignment of the mucosal lines between the flap and the adjacent mucosa, which was discussed in Chapter 3. Strictly, invasive cervical resorption of a vital tooth must be considered to be a third possibility, although this could have been the result of the treatment, just as it could have been the cause of the impaction. Clinical examination Invasive cervical root resorption in an unerupted permanent tooth is characterized by the absence of any response on the part of the tooth to orthodontic traction force and by the tell-tale radiolucent area in the cervical area of the tooth, as may often be seen on a periapical or panoramic radiograph. As we have noted, imaging and definitive diagnosis may be difficult to establish, particularly in an early lesion, and a cone beam CT will assist materially in recognizing the defect and mapping its extent. Because definitive diagnosis is difficult to establish, a thorough clinical examination assumes greater importance. Indirect clinical recognition of the phenomenon may often be derived from the clinical examination and is a very important first step in these cases. It may contribute much to the practitioner’s initial diagnosis of the case and to informing the patient at an early stage that there may be a questionable prognosis for the tooth.

202  Orthodontic Treatment of Impacted Teeth

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Fig. 7.14  (Courtesy of Dr B. Jesperson) (a–c) The intra-oral views show a normal alignment and occlusion of the left side, with anterior spacing. The right side shows a normal molar relation, but strongly mesial tipping of the second premolar and distal tipping of the canine, with under-eruption of both teeth. There are large spaces on either side of these teeth and a localized lateral open bite. (d) The impacted first premolar is seen with a very ‘woolly’ appearance of its crown and root, indicating very advanced involvement of the resorption process, undermining the enamel of the crown and much of the root. There is a loss of integrity of the lamina dura on the entire mesial side. Although apparently unassociated, the central incisors have very short roots in comparison with the lateral incisors.

It is common knowledge that when a deciduous molar tooth is extracted and space is lost in the arch, this will have occurred by the adjacent teeth mildly tipping into the area, from both the distal and the mesial sides. The successional premolar will either become impacted between the two adjacent tipped teeth or will find a pathway to erupt buccally or lingually displaced from the line of the arch. In contrast, the teeth adjacent to a markedly infra-occluded deciduous second molar will characteristically show much more pronounced tipping and their occlusal level has been shown to also be infra-occluded relative to the other teeth in the same jaw, but less so than the affected deciduous molar [35–37]. There is also usually a deviation of the dental midline to that side, even in a spaced dentition. In similar manner, the teeth adjacent to a site where an impacted tooth has been prevented from erupting due to invasive cervical resorption will show the same pronounced degree of tipping and the same picture of relative infraocclusion, as with those adjacent to an infra-occluded deciduous molar. So, from a clinical point of view, the orthodontist should look for the following signs:

exaggerated tipping of the teeth adjacent to the impacted • tooth (Figure 7.14); relative height deficiency of the adjacent teeth, often with • a localized lateral open bite; deviation of the midline to that side. • If the affected tooth had erupted prior to the onset of the cervical root resorption, the tooth will often be seen, in a growing child, to infra-occlude progressively further and further in relation to the occlusal level, to create an open bite (Figure 7.15). On the radiograph, the signs usually seen are: a radiolucency in the cervical area of the tooth which • may range from a small area that can be confused with typical interproximal radiographic ‘burn-out’, to a ‘woolly’ area affecting one side of the tooth and stretching into the crown and longitudinally further down the root; loss of the lamina dura in the immediate area; the root apices of the teeth on either side of the affected tooth are excessively distanced from one another and

• •

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  203 

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(b) 06 2009

(c) Fig. 7.15  (Courtesy of Dr M. Friedman.) (a) The left central incisor is relatively under-erupted in comparison with the right central incisor and an open bite is present on that side. (b) This picture was taken 14 months later and shows a very much increased infra-occlusion of the left central incisor and a much larger open bite, with mesial tipping of the right central incisor across the midline. (c) A periapical view of the left central incisor shows a small resorption lesion, with a very small portal of entry at the cervical level (see arrow). The lesion may be seen to have progressed coronally and apically parallel with the pulp chamber, with a narrow wall separating the two.

204  Orthodontic Treatment of Impacted Teeth imagining their corrective uprighting will create space for almost two teeth. Given the histopathological background to the possible causation of this very aggressive condition, it is time to look again at some of the time-honoured customs that are often routinely practised during the most crucial event in the treatment of the impacted tooth, namely the surgical exposure. It is conceivable that some of these customs might be precipitating factors that initiate the lesion. Thus, it is unlikely that a surgeon will deliberately remove bony tissue to such an extent that there is exposure of the cervical area of the root surface. Nevertheless and in the interests of making sure that the tissues do not subsequently heal over, this may be the unintended consequence. The risk may be increased if a surgical pack is pushed forcefully down the periodontal space. Old habits and idiosyncrasies in the exposure protocol die hard and the surgeon must be made aware of this possible source of danger. When the surgical field has been laid open the surgeon will usually check the tooth for mobility. The sole purpose of this test is to see if the tooth is ankylosed or not. However, many surgeons will actually aim to mechanically increase this mobility by passing an elevator beyond the CEJ and along the root surface to act as a lever. This exercise cannot be condemned strongly enough, because it damages the periodontium and cementum and may cause an ankylosis. This methodology has been used to deliberately ankylose a deciduous maxillary canine, to prepare it to be used as an absolute anchor unit against which forces may be applied to move other teeth [38]. In the light of the studies referred to above [24–27], there may be some basis to further speculate that this site-specific, acute trauma to the periodontium and cementum may alternatively initiate the process of invasive and equally site-specific cervical resorption by denuding the dentine surface and preventing the cementum or the oral epithelium from forming a protective cervical cell layer in an angular defect. During many years of orthodontic practice, the author has found that the temptation among many of the excellent surgeons with whom he has worked to ‘loosen’ the impacted tooth has been seen to be rife and it is only his restraining presence that has often prevented this from happening. Similarly, with the use of orthophosphoric acid etchant in the form of a liquid rather than a gel, it is difficult to limit the spread of the caustic material into the surrounding vital tissues that will have been exposed at surgery. Should the etchant come into contact with the denuded tooth beyond the CEJ, it is likely that inflamed granulation tissue, rather than cementum or oral epithelium, will encompass the tooth surface during the healing period and the stage will be set for the initiation of an invasive cervical resorption lesion. Performed in expert hands, surgery of this kind need not take long to complete. However, time is often wasted with

the surgical field wide open while suitable implements or bonding agents are searched for and, unless continuously irrigated with saline, the exposed tissues will become subject to desiccation. This becomes more acute if efficient suction is still being used by the attending staff to stave off the bleeding. Consequent cell death in these sensitive areas could create an environment conducive to the initiation of an ICRR process. It is known that acid etchant is a good haemostatic agent and has been recommended for use by paediatric dentists to control gingival haemorrhage to permit an uncontaminated restoration to be placed. Anecdotally, the author has been in irregular correspondence with one particular orthodontist regarding an abnormally disappointing record of failure in treatment of a series of impacted teeth, in which the most frequently diagnosed cause was invasive cervical root resorption. In a quasi-detective investigation of this strange phenomenon, it was found that the surgeon had been routinely flooding the exposed area with orthophosphoric acid to provide both a bloodless field and, at the same time, a suitably enamel-etched bonding surface for placing an attachment on the impacted tooth! By not being present at the surgical episode, the orthodontist loses control of the dynamics of the treatment, as pointed out in Chapter 3. Nevertheless and despite this apparently elementary safety precaution, the overriding majority of orthodontists still refer their patients, unaccompanied, to the oral surgeon or periodontist for the exposure. It is worth remembering that it is not the surgeon but the orthodontist who will be responsible for achieving a successful outcome. The notion is offered that the presence of the orthodontist during this critical and highly sensitive surgical procedure in the patient’s treatment will contribute much to the success of the treatments provided. It should be remembered that the role of the surgeon is to provide therapeutic access to a tooth whose future would otherwise be highly questionable. With the orthodontist on hand to answer questions regarding type of surgical exposure needed, the aspect of the tooth to be exposed, the degree of exposure required, as well as to take an active part in the bonding of the attachment and application of traction on the spot, control of the treatment is retained in the hands of the person ultimately responsible for its outcome. Treatment of this atypical form of resorption is possible, depending on its location and extent. It usually consists of gaining surgical access to the lesion, removing the fibrovascular tissue and repairing the defect with restorative material. It has also been recommended [27] to apply a topical 90% aqueous solution of trichloracetic acid, curettage, endodontic therapy where necessary and restoration with a glass ionomer cement. With the histopathological character of the lesion eliminated, the tooth may then be expected to respond to traction (Figure 7.16). An infrabony periodontal pocket will remain and will require

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Fig. 7.16  (a–c) Maxillary first premolars had been extracted by another practitioner ‘to allow space for eruption of the unerupted right lateral incisor’. Note the relative lack of vertical development and tipping of adjacent teeth, reminiscent of an association with infra-occlusion. (Compare with Figure 7.14.) (d) The pre-surgical periapical radiographic view shows a dark shadow in the distal half of the crown of the incisor and this extends to the cervical margin on the distal side of the tooth. (e) Following orthodontic space regaining, surgical exposure reveals the cervical resorption defect. Soft resorption-replacement tissue had prevented the eruption. (f) The resorption area was debrided and the exposed pulp extirpated and root-filled temporarily with calcium hydroxide. After amalgam restoration placement, an eyelet was bonded and immediate traction applied. (Surgery by Prof. A. Shteyer, endodontics by Prof. I. Heling.) (g) The final stages of eruption mechanics. (h–j) The completed orthodontic result, after definitive root canal therapy was completed and a porcelain crown placed. (k, l) The clinical and periapical radiographic views of the tooth.

206  Orthodontic Treatment of Impacted Teeth

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Fig. 7.16  (Continued )

periodontal treatment and a considerable degree of supraeruption (forced eruption) of the tooth to bring the affected root area to the surface. At best, then, this will leave the tooth with a short root and a long clinical crown. When an invasive cervical resorption lesion is extensive or occurs in a severely displaced impacted tooth, access for the necessary treatment may be inadequate and extraction is likely to be the only reasonable alternative. Pre-eruptive invasive coronal resorption An invasive resorptive process can only attack the crown of an unerupted tooth as its primary source through an enamel defect. This type of resorption is also very aggressive and may consume all the dentine within the crown, as it painlessly mushrooms beneath the enamel outer layer [39]. It may also resorb away some or most of the enamel shell itself (Figure 7.17). In these circumstances, it is easy to understand the concern and even panic of the orthodontist or the surgeon, when faced with this chance finding on the radiographic film. On presumptions of serious doubt for the chances of long-term survival of this tooth and the likelihood of its early demise, such teeth are often extracted or an ill-advised immediate and risky restorative procedure undertaken under the existing, far from ideal, conditions of partial eruption or impaction. Because the affected tooth is unerupted, its root development is incomplete, with wide open apical areas and broad, apically- divergent root canals. Nevertheless, the pulp tissue is entirely normal, with no inflammation and no stimulation for the formation of reparative secondary dentine. In these circumstances, it is easy for the orthodontist or the surgeon, when faced with this chance finding on the radiographic film, to come to hasty and mistaken conclusions. On presumptions of serious doubt for the chances of long-term survival of this tooth and the likelihood of its early demise, such teeth are often extracted or an ill-advised

immediate and highly risky endodontic and restorative procedure undertaken under the existing, far from ideal, location of under-eruption or impaction. Even when extensive destruction of the intracoronal dentine has occurred, pulpal involvement is unlikely and one may see the continuation of normal apexification in a diagnosed, coronally resorbed, unerupted tooth. As we have pointed out in relation to invasive cervical root resorption, the resorptive process stops short at the predentine, presumably for the same reason. It is usually possible to see the predentine bridge on a radiograph (Figure 7.18). It should be understood that these teeth are not likely to be impacted and they will usually erupt normally, regardless of the extent of the resorption and provided their dental follicle has remained intact. Nevertheless, treatment should be aimed at exposing and erupting the tooth as soon as possible after diagnosis in order to eliminate further damage. It is therefore logical to eliminate the urgency of the situation by simply exposing the crown of the tooth with an open surgical procedure, aimed at cutting off the blood supply to the resorptive tissue within the crown. This will deprive the tissue of its lifeline, causing it to become necrotic. Without question, an under-erupted tooth in that condition, and with the passage of time, will most likely and secondarily develop caries within the large dentine defect, making the need for restorative treatment still essential. A good temporary restoration may therefore be placed, without excavating the deeper part of the cavity, to seal off the lesion from the opportunistic initiation of caries. This effectively defuses and freezes the issue for the immediate to middle future, thereby making restorative treatment far less urgent. Permanent restorative procedures may be delayed until the tooth has fully erupted and when conditions for this will be optimal. Root canal therapy is not normally required if all the diseased material is carefully eliminated, but this may leave insufficient dental hard tissue to be retentive of

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  207 

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Fig. 7.17  (a–d) intra-oral photographs of 11-year-old male patient. (e, f) Panoramic and periapical views to show crown resorption of maxillary right permanent canine. (g) The exposed crown showing extreme degree of resorption. (h) An eyelet attachment in place, with twisted pigtail ligature. (i) The extrusion auxiliary arch in its passive mode. (j) The extrusion auxiliary arch engaged in the pigtail ligature, exerting extrusive force. (k) Seen from the occlusal aspect. (l) The tooth has erupted rapidly, seen from the occlusal. (m) The buccal view. (n–q) The competed case after root canal treatment and rehabilitation. (r) Periapical radiograph of completed case.

208  Orthodontic Treatment of Impacted Teeth

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Fig. 7.17  (Continued )

Impacted Teeth and Resorption of the Roots of Adjacent Teeth  209 

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210  Orthodontic Treatment of Impacted Teeth

Predentine bridge inhibits resorption Pre-eruption crown resorption Fig. 7.18  The unerupted second permanent molar has an extensive area of coronal resorption, which is separated from the wide pulp chamber by a narrow dentine bridge. Access to this lesion is extremely limited, the pulp chamber is wide and the roots are only partly developed.

the restoration. In this circumstance, an elective root canal procedure will need to be undertaken, to facilitate placement of a post and core reconstruction, in order to provide the foundation for good crown rehabilitation.

References   1.  Ericson S, Kurol J. Incisor resorption caused by maxillary cuspids. A radiographic study. Angle Orthod 1987; 57: 332–345.   2.  Ericson S, Kurol J. Radiographic examination of ectopically erupting maxillary canines. Am J Orthod Dentofacial Orthop 1987; 91: 483–492.   3.  Ericson S, Kurol J. Resorption of maxillary lateral incisors caused by ectopic eruption of the canines. A clinical and radiographic analysis of predisposing factors. Am J Orthod Dentofacial Orthop 1988; 94: 503–513.   4.  Ericson S, Kurol J. CT diagnosis of ectopically erupting maxillary canines – a case report. Eur J Orthod 1988; 10: 115–120.   5.  Ericson S, Kurol J. Early treatment of palatally erupting maxillary canines by extraction of the primary canines. Eur J Orthod 1988; 10: 283–295.   6.  Brin I, Becker A, Zilberman Y. Resorbed lateral incisors adjacent to impacted canines have normal crown size. Am J Orthod 1993; 104: 60–66.   7.  Ericson S, Kurol J. Resorption of incisors after ectopic eruption of maxillary canines: a CT study. Angle Orthod 2000; 70: 415–423.   8.  Walker L, Enciso R, Mah J. Three-dimensional localization of maxillary canines with cone-beam computed tomography. Am J Orthod Dentofacial Orthop 2005; 128: 418–423.   9.  Savage RR, Kokich VG Sr. Restoration and retention of maxillary anteriors with severe root resorption. J Am Dent Assoc 2002; 133: 67–71. 10.  Olive R. Factors influencing the non-surgical eruption of palatally impacted canines. Aust Orthod J 2005; 21: 95–101. 11.  Leonardi M, Armi P, Franchi L, Baccetti T. Two interceptive approaches to palatally displaed canines: A prospective longitudinal study. Angle Orthod. 2004; 75: 581–586. 12.  Lindauer SJ, Rubenstein LK, Hang WM, Andersen WC, Isaacson RJ. Canine impaction identified early with panoramic radiographs. J Am Dent Assoc 1992; 123: 91–92, 95–97. 13.  Power SM, Short MBE. An investigation into the response of palatally displaced canines to the removal of deciduous canines and an assessment of factors contributing to favourable eruption. Br J Orthod 1993; 20: 215–223.

14.  Becker A, Chaushu S. Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically-associated canine impaction. American Journal of Orthodontics and Dentofacial Orthopedics 2005, 127: 650–654. 15.  Ericson S, Kurol J, Falahat B. Does the canine dental follicle cause resorption of permanent incisor roots? A computed tomographic study of erupting maxillary canines. Angle Orthod 2002; 72: 95–104. 16.  Vanarsdall RL. What every orthodontist should know about impacted teeth. Presented at the 106th American Association of Orthodontists’ Annual Session, Las Vegas, May 2006. Audio 28:186B. 17.  Becker A, Chaushu S. Impacted canines and associated incisor root resorption: can it be a win–win situation? Presented at the 106th American Association of Orthodontists’ Annual Session, Las Vegas, May 2006. Audio recording 28:186A. 18.  16. Becker A, Chaushu S. Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically-associated canine impaction. Am J Orthod Dentofacial Orthop 2005; 127: 650–654. 19.  Kokich VG Jr, Kinzer GA. Managing congenitally missing lateral incisors. Part I: canine substitution. J Esthet Restor Dent 2005; 17: 5–10. 20.  Kokich VG. Surgical and orthodontic management of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2004; 126: 278–283. Kinzer GA, Kokich VO Jr. Managing congenitally missing lateral incisors. Part III: single-tooth implants. J Esthet Restor Dent 2005; 17: 202–210.Kokich VG. Maxillary lateral incisor implants: planning with the aid of orthodontics. J Oral Maxillofac Surg 2004; 62: 48–56. 21.  Jacoby H. The ballista spring system for impacted teeth. Am J Orthod 1979; 75: 143–151. 22.  Kornhauser S, Abed Y, Harari D, Becker A. The resolution of palatallyimpacted canines using palatal-occlusal force from a buccal auxiliary. Am J Orthod Dentofacial Orthop 1996; 110: 528–534. 23.  Farhad A, Mohammadi Z. Calcium hydroxide: a review. Int Dent J 2005; 55: 293–301. 24.  Heithersay GS. Clinical, radiologic, and histopathologic features of invasive cervical resorption. Quintessence Int 1999; 30: 27–37. 25.  Heithersay GS. Invasive cervical resorption: an analysis of potential predisposing factors. Quintessence Int 1999; 30: 83–95. 26.  Heithersay GS. Treatment of invasive cervical resorption: an analysis of results using topical application of trichloracetic acid, curettage, and restoration. Quintessence Int 1999; 30: 96–110. 27.  Heithersay GS. Invasive cervical resorption following trauma. Aust Endod J 1999; 25: 79–85. 28.  Patel S, Kanagasingam S, Pitt Ford T. External cervical resorption: a review. Journal of Endodontics, 2009; 35: 616–625. 29.  Brosjö M, Anderssén K, Berg J-O, Lindskog S. An experimental model for cervical resorption in monkeys. Dental Traumatology, 1990; 6: 118–120. 30.  Hiremath H, Yakub S, Metgud S, Bhagwat S, Kulkarni S. Invasive cervical resorption: a case report. Journal of Endodontics, 2007; 33: 999–1003. 31.  Frank AL, Torabinejad M. Diagnosis and treatment of extracanal invasive resorption. Journal of Endodontics 1998; 24: 500–504. 32.  Iqbal MK. Clinical and scanning electron microscopic features of invasive cervical resorption in a maxillary molar. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2007; 103: e49–e54. 33.  Friedman S, Rotstein I, Libfeld H, Stabholz A, Heling I. Incidence of external root resorption and esthetic results in 58 bleached pulpless teeth. Dental Traumatology 1988; 4: 23–26. 34.  Vermette ME, Kokich VG, Kennedy DB. Uncovering labially impacted teeth: apically positioned flap and closed-eruption techniques. Angle Orthod. 1995; 65: 23–32. 35.  Becker A, Karnei-R’em RM. The effects of infraocclusion: part 1 – tilting of the adjacent teeth and space loss. American Journal of Orthodontics 1992; 102: 257–264. 36.  Becker A, Karnei-R’em RM. The effects of infraocclusion: part 2 – the type of movement of the adjacent teeth and their vertical development. American Journal of Orthodontics 1992; 102: 302–309. 37.  Becker A, Karnei-R’em RM, Steigman S. The effects of infraocclusion: part 3 – dental arch length and the midline. American Journal of Orthodontics 1992; 201: 427–433. 38.  Kokich VG, Shapiro PA, Oswald R, Koskinen-Moffett L, Clarren SK. Ankylosed teeth as abutments for maxillary protraction: a case report. Am J Orthod 1985; 88: 303–307. 39.  Holan G, Eidelman E, Mass E. Pre-eruptive coronal resorption of permanent teeth: report of three cases and their treatments. Pediatric Dentistry, 1994; 16: 373–377.

8 Other Single Teeth

Buccally displaced maxillary canines (BDC)

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Maxillary first molars

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Mandibular second molars

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Maxillary second molars

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Mandibular third molars

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Impaction and crown resorption

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Infra-occlusion of permanent teeth

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Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

212  Orthodontic Treatment of Impacted Teeth Aside from third molars, the maxillary canines and central incisors are the principal teeth that may become impacted but, from time to time, other teeth may also be affected. For some of these teeth, familiar patterns emerge, typically affecting the same tooth and with the same aetiology in many of the cases. In others, unusual pathology is involved, which may affect any tooth or group of teeth and is, therefore, quite non-specific. Nevertheless, even with a widely heterogeneous group, trends may be recognized and treatment protocols may be suggested to cover a good proportion of them. Before moving on to buccally displaced canines, there is a small group of maxillary canines which are neither buccally nor palatally displaced, but are in the line of the arch. According to the panoramic or periapical view, the orientation of their long axes is mildly mesially inclined. By virtue of this combination of location and angulation, the crown comes to be jammed at an angle against the distal aspect of the root of the lateral incisor, whose long axis may be oriented distally. From there, the canine appears to be unable to free itself to erupt, unless the incisor itself is tipped mesially during the initial space-opening procedure. This standard preparatory orthodontic movement reduces the angulation between the long axes of canine and incisor to a marked degree, but it also moves the apex of the lateral incisor distally, providing the impetus to secondarily tip the crown of the canine distally and inferiorly and reduce the angulation still further. This will often be sufficient to elicit resolution of the impaction and spon­ taneous eruption of the tooth into its normal place in the arch. In the event that progress is not achieved within a few months, simple surgery, attachment bonding and traction from an auxiliary nickel–titanium wire or elastic ligature will be sufficient to resolve the problem. The type of surgery advised will depend on the height of the impacted tooth vis-à-vis the gingival tissue. If there is a thick band of attached gingiva above the height of the unerupted tooth, then a simple window exposure will be ideal, since the tooth will be erupted through this band and a width of attached gingiva will remain on the labial side of the tooth in the long term. Should this not be the case, then an apically repositioned flap will ensure that the tooth will have a normal gingival attachment [1]. Equally, a full-flap closed procedure will achieve largely the same result as the apically repositioned flap procedure and, for these relatively minor impactions, there would appear to be very little to choose between the two procedures in terms of the periodontal outcome.

Buccally displaced maxillary canines (BDC) In Chapter 6, it was recorded that palatal impaction of maxillary canines occurs in 1–2% of most Caucasian populations studied. They exceed the prevalence of buccally

impacted maxillary canines by a ratio of 2 or 3:1 [2, 3] while, paradoxically, buccally ectopic maxillary canines which have erupted into the mouth represent one of the most frequently encountered conditions in orthodontic practice. In contrast to Caucasian populations, one study [4] found that Orientals suffer more buccal impactions, while the frequency of palatal impaction in that ethnic group is very low. Tooth size and arch length play important roles in the difference between palatal and buccal impaction, insofar as the dentition with palatal impaction is characterized by an excess of space in the dental arches for the most part [5–7], while the buccal impaction cases show marked crowding [5, 8]. In males this seems to be more due to a deficiency in length of the dental arch, while in females it was found to be more related to larger than average teeth [9]. We have pointed out that the developmental location of the unerupted maxillary canine is slightly buccal to the general line of the dental arch and that the two adjacent teeth erupt ahead of the canine. This being so, and in the presence of any crowding, the space for the canine between these two teeth will be reduced, and this will cause the canine to exaggerate the buccal tendency of its eruptive path (see Chapter 6). Dental age also appears to be associated with these two very different phenomena. While patients with palatal canines showed a strong tendency for delayed dental development, a similar study of a large sample of patients with buccally ectopic canines showed a normal dental age distribution [10]. There was only a small variation on either side, when dental age and chronological age were compared. The dental age of patients with palatally impacted canines showed two distinct and separate trends. In half the cases, the dental age was normal, and in the other half, the dental development was very late, by as much as two years. Advanced dental development was not seen in any of the cases within the palatal canine group [11]. Ectopic canines in the absence of crowding Among the individuals that we see with buccal displacement of the canines, there is a small but significant number in whom there is no crowding to account for this phenomenon. In order to shed more light on this, the clinical features of the dentitions of a large sample of such cases were compared to those of a similar sample of BDC cases with crowding and another sample of cases in whom the canine had erupted into its place [12]. Dental age vs. chronological age and mesio-distal tooth dimensions showed no difference between the patients in the three groups. There was a single significant finding in this study, which related to the adjacent lateral incisor tooth. This tooth exhibited a much increased prevalence of anomaly and delayed development, in exactly the same way as has been recorded in relation to palatal canine displacement. Both the Guidance Theory and hereditary primary

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Fig. 8.1  The canine has developed in an abnormal location – primary tooth germ displacement or lack of guidance from the adjacent peg-shaped lateral incisor?

displacement of the tooth germ offer cogent aetiological explanations for the occurrence of this phenomenon, as pointed out in Chapter 6 (Figure 8.1). In the absence of crowding, the canine may erupt higher up in the area of the sulcus oral mucosa, which creates a poor gingival attachment. From the periodontal point of view, having only thin oral epithelium covering the root leaves the patient with a delicate and easily traumatized attachment apparatus. Different surgical approaches have been described in Chapter 3 to resolve the problem. Buccally impacted canines with mesial displacement Most buccally displaced canines have a slight mesial displacement, overlapping the distal side of the lateral incisor. These are so common in orthodontics that we may consider them routine, whether they are erupted or unerupted. However, on occasion one may find that the degree of displacement of the unerupted canine crown is quite extreme, overlapping very high up on the mesial side of the root of the lateral incisor. These canines will progress more mesially and inferiorly in the early teen years and may be found at the level of the apical third of the root of the incisor in the bony depression that is located in the height of the sulcus. Although these are often palpable, the unusual height and mesial displacement of the tooth in the sulcus may lead to an erroneous initial clinical diagnosis. In the clinical intra-oral examination, clues to their position may be found by studying the orientation of the adjacent incisors (Figure 8.2). Because the canines occupy bucco-lingual space in the alveolus, which is very narrow superiorly, their presence causes a palatal displacement of the root apex of the lateral and, occasionally, the central incisors. Tipping the patient’s head backwards and studying the anterior part of the maxilla from the occlusal aspect, the astute clinician will note that the lateral incisor has a strong palatal inclination, occasionally with its root promi-

nently outlined beneath the palatal mucosa. The tooth clearly needs considerable labial root torque. Diagnosis of labial location of the canine may not be easy to confirm radiographically. At this relative height, the panoramic view shows it to traverse the apical areas of the lateral and, sometimes, central incisors. Nevertheless, confirmation of labial location may be deduced given the presence of the tooth as it is imaged superimposed on the root of this lateral incisor and, from the clinical examination, the fact of palatally prominent root. Although the impacted canine is labial to the incisor roots, it is more distant from the film than are the incisor crowns, given its height and situation in the labial depression of the anterior maxilla and hence its radiographic image on the panoramic view will be enlarged, relative to those of the incisors. Canines in this location are precisely the teeth for which the method described for labio-lingual determination of canine position using a single panoramic view [13, 14] does not apply. Periapical or occlusal radiography of these teeth will superimpose them on the incisor roots at a lower level due to the acute angulation of the X-ray cone. Thus, the combination of a periapical or occlusal view with the panoramic view will facilitate diagnosis using vertical tube shift information (Figure 8.2c, d). Antero-posterior information will be seen on the lateral cephalogram, which will show the location of the crowns of these teeth relative to the incisor roots and to the anterior nasal spine. When a mesially directed and labially impacted canine is present in a patient whose maxillary incisor arrangement accords with the archetypal class 2 division malocclusion, the situation may become a very complex canine/lateral incisor partial transposition. In this scenario, the unerupted canine lies high on the labial side of the root of the lateral incisor and, as pointed out above, the root of this lateral incisor is tipped palatally and its crown proclined labially. The long axes of the central incisors, on the other hand, show lingually tipped crowns and a labial orientation of their roots, which are often palpably outlined in the labial sulcus. With the lateral incisor roots palpable on the palatal side and the central incisor roots on the labial, there is much space in the bucco-lingual plane between the root apices of these teeth. It will be appreciated that in these circumstances, the impacted canine may progress further mesially and migrate to the palatal side of the central incisor roots (Figure 8.3a–d). With the canine root labial to the root of the lateral incisor and its crown palatal to the central incisor, orthodontic resolution and alignment may be impossible. If positional diagnosis is based solely on the buccal object rule using two periapical films at different angles, the palatal location of the canine crowns to the central incisors will be confirmed, but without clinical observation or more sophisticated imaging the relation between canine and lateral incisor will be missed. The unsuspecting orthodontist, who routinely relies solely on Clark’s tube-shift method

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Fig. 8.2  (a, b) Clinical views showing an over-retained deciduous right maxillary canine. Note the labial and distal tipping of the right lateral incisor crown and the palatal root position. (c) Anterior occlusal view showing superimposition of canine crown and lateral incisor root on right side. From this view, the canine could be inferior to the lateral’s root on the palatal side or superior to the root on the labial. (d) A section of the panoramic view to show the severe mesial displacement and unusual height of the canine. Taken together with the anterior occlusal view, the vertical tube shift created shows the canine to be buccal. (e, f) Mesio-distal tube shift periapical views confirm the buccal diagnosis. (g, h) Extraction of the right deciduous and permanent canines only, together with maxillary arch mechano-therapy, has achieved space closure and good intercuspation in class 1 on the left and class 2 on the right, with midline correction.

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Fig. 8.3  (a–d) Three-dimensional CT views of the anterior maxilla, showing a high buccal canine that has displaced the lateral incisor root palatally and distally and which has progressed mesially to traverse the arch on the palatal side of the central incisor. (e, f) The two tube shift periapical views confirm the palatal location of the canine crown vis-à-vis the central incisor, but give no hint as to the complexity of the case. A palatal approach to surgical exposure would be disastrous (see Figures 12.16, 12.17 and 12.18). (Courtesy of Dr N. Dykstein.)

216  Orthodontic Treatment of Impacted Teeth (Figure 8.3e, f), will surely offer inappropriate treatment in this case because it will lead him/her to think of a palatal surgical and orthodontic approach to the crown of the canine. This would be totally misleading since the subsequent orthodontic manipulation of the canine in a palatal direction will hinge the canine root around the root of the lateral incisor, inflicting damage to that tooth. At the same time, the apex of the canine will be swung anteriorly to clash against the labial plate, from where there would be no reasonable possibility of success. The only available app­ roach would be to expose the canine crown from the labial side and apply traction in a labial and distal direction to bring the tooth clear of the central incisor. It would then need to be drawn labially and distally around the root of the lateral incisor and into its place in the arch. Nevertheless, a treatment decision will still be necessary since the canine will not remain static, but will continue on its ectopic path. The treatment options are: 1. To leave the canine in place – with suitable long-term radiographic follow-up planned; this policy precludes any possibility of orthodontic correction of the incisor relationship and it always carries with it the risk that neglect on the part of the patient will lead to further complications in later life. 2. To extract the impacted tooth and align the lateral incisor. 3. To extract the lateral incisor, align the canine into its normal place and prepare for an implant to replace the missing incisor. 4. To extract the lateral incisor, align the canine into the place of the missing incisor and draw the posterior teeth mesially to eliminate the spaces. 5. To align the teeth in their transposed order. 6. To expose the tooth and bring it into designated place in the arch, while realigning the lateral incisor in its place, with carefully planned directional orthodontic treatment. Regardless of its relation to the central incisor, a labial surgical and orthodontic approach is essential because of the relationship of the canine to the lateral incisor. Surgical access and orthodontic traction need to be negotiated very delicately between the roots of the central and lateral incisors and, above all, no attempt at root uprighting or torque of the incisors should be undertaken until the canine is well clear of both (Figure 8.3). This, therefore, rules out the early use of rectangular archwires and it is often wiser not to ligate the lateral incisor into the arch until the later stages of treatment. In these cases, the canine has to be drawn through between the incisor roots at a level high in the sulcus, above to the labial archwire, which makes it difficult to erupt it through attached gingiva (Figure 6.45). The three-dimensional relationship of the teeth to one another and the possible existence of incisor root resorption are very difficult diagnoses to make, particularly in

the bucco-lingual plane, as pointed out in Chapter 2, and cone beam computerized tomography should be performed to provide the relevant and much needed accurate information. For most other buccally impacted maxillary canines surgical access is good, but the ability to provide a satisfactory orthodontic strategy to reduce the impaction and still provide for a good periodontal prognosis may be poor. This is because the high buccal canine tooth must be brought buccally, inferiorly and distally in a manner that circumvents the root of the adjacent incisor. This involves its being drawn in a semicircular flanking movement around the lateral incisor root, in an area where the alveolar bone is too narrow to allow one root to pass by another. As the canine is moved labially, the bony alveolar plate responds and becomes more prominent as it remodels labially. This bony remodelling does not add width to the same degree as the dental movement, so that the root of the tooth loses some of its labial bone and soft tissue support, and a long clinical crown often results. The prospects for mucogingival surgery, performed at the time of exposure while possible [15, 16] are very limited for the high buccal canine and a long clinical crown with a relatively poor periodontal outcome are to be expected [17]. Given these drawbacks, the more severely displaced buccal canines of this type may occasionally need to be extracted, and, as far as possible, the deciduous canine left in place. In this instance, it is recommended to provide additional space mesially and distally, to allow for its crown to be prosthetically enlarged in anticipation of a later implant restoration when the deciduous tooth is finally lost. If the deciduous canine has a poor prognosis, an early decision regarding space closure or space opening should be made. Where appropriate, controlled orthodontic space closure may then be carried out, with or without a compensating extraction on the opposite, unaffected side. Alternatively, orthodontic preparation of the case for an implant-borne replacement crown will need to be undertaken as part of the overall orthodontic treatment. Buccally impacted canines with distal displacement It is unusual to come across a buccally located canine which is also displaced distally. These are almost invariably transposed with the first premolar tooth, to a greater or lesser extent (Figure 8.4). Many of these transposed canines erupt high in the sulcus where they are invested with oral epithelium rather than with attached gingiva. Others do not erupt and may need to be surgically exposed, depending on the orthodontic treatment plan. However, in these cases the orthodontist will frequently decide to align the teeth in their transposed order. By and large, these transposition patients present with the first premolar crown in its normal place, but its roots are displaced mesially, giving the tooth a distally inclined long axis. The tooth may be quickly

Other Single Teeth  217 

Fig. 8.4  A distally displaced maxillary canine, transposed with the first premolar.

tipped mesially, uprighting it into the site vacated by extraction of the deciduous canine. Under these circumstances, tipping the first premolar into the canine location reciprocally creates space for the canine in the first premolar place and the canine will usually respond with autonomous eruptive movement. Many of these teeth may then come down without the application of orthodontic forces, although full eruption may take many months, sometimes extending into a year or more. Nevertheless, and even though there may be no apparent reason for this natural process to be retarded, a good number remain unerupted or in their partially erupted state for a very long time and hardly progress. Therefore, following the mesial movement of the first premolar in the earlier part of the treatment, these teeth should be exposed and actively drawn to the labial archwire, using light elastic traction or an auxiliary nickel–titanium wire placed piggyback style over the existing heavier base arch. Leaving an orthodontic appliance in place for all this time without exploiting it to erupt and align the canine is counterproductive, insofar as its presence runs the risk of producing the deleterious side-effects of caries and periodontal inflammation and is to be discouraged. Thus, when the impacted tooth shows no signs of erupting or does not fully erupt within a reasonable period of time after space has been prepared for it, orthodontic traction and alignment should be initiated. If the tooth remains unerupted and situated above the level of the line of the attached gingiva, the window technique exposure will leave it with an undesirable labial attachment consisting of oral mucosa. Consequently, an apically repositioned flap or a fully closed flap exposure will be more appropriate, and the tooth brought down by direct traction to the labial archwire of the appliance. Many clinicians tend to judge severity of transposition by the relative positions of the crowns of the two affected teeth, when the only valid determinant of severity is in the relative positions of their root apices. As the result, the inexperienced practitioner may be unwisely drawn into attempting to bring the

teeth to their ideally corrected order – a task that requires considerable clinical skill and an extended treatment time. If the displaced canine can be moved mesially while it is still relatively high, then the danger of root proximity of the affected teeth, as they are drawn past each other across the narrow alveolar width, is reduced. However, while a closed surgical exposure may be preferred with a high canine, this can only be conveniently used when the direction of traction is vertically downwards. It is not easy to adapt the method when the direction of traction has more than a minor degree of mesial or distal component, because the elastic thread or closed coil spring that may be used will cause soft tissue impingement. Nevertheless, if full correction of the transposition is to be undertaken, it is wise initially to place an eyelet attachment on the mesial aspect of the exposed canine, so that mesial traction will not generate a mesio-lingual rotational component on the tooth as it moves forward. Once the crown of the tooth has been moved into its correct location, the eyelet is removed and a bracket of the type used on the other teeth is placed in its ideal position on the tooth to complete the remaining movements needed, usually mesial uprighting, palatal root torqueing and a degree of derotation.

Mandibular canines Mandibular impacted canines are rarely seen and, as the result, the more bizarre cases are published as single case reports in the literature [18, 19]. The very few numerically significant case series that have been published have gathered the cases from many centres and individual practitioners, on an international multicentre basis [20]. Impacted mandibular canines are usually chance findings and are not discovered because the condition is almost always symptomless. The over-retained deciduous canine may not raise the suspicions of a dental practitioner until well into the second decade of life and often even later. It seems possible that females are more frequently affected, although the evidence for this is tenuous, given the lack of large sample studies. The frequency with which this phenomenon occurs has been quoted as being 20 times less frequent than the parallel condition in the maxillary arch. While maxillary impacted canines crossing the mid-palatal suture has not been reported, mandibular canines do cross the symphysis (Figure 8.5) and have been reported to have reached as far as the permanent molar on the opposite side [21, 22]. They may sometimes be located on the lingual side of the alveolar process, when they will appear as a palp­ able hard swelling under the lingual mucosa. They are more frequently to be found buccally ectopic or in the general line of the arch. They travel relatively large intra-osseous distances and may become embedded in the chin prominence.

218  Orthodontic Treatment of Impacted Teeth

Fig. 8.5  The crown of the horizontally impacted right mandibular canine overlies the root of the erupted mandibular canine of the opposite side. (Courtesy of Dr T. Weinberger.)

The first clue to the existence of an impacted canine is the over-retention and lack of mobility of its deciduous predecessor and this should stimulate the clinician to perform a radiographic examination. Regarding aetiology, there may be obvious local factors to which the condition may be attributed, namely supernumerary teeth, odontomes (Figures 8.6 and 8.7) and an enlarged dental follicle. However, it is important to note that soft tissue lesions, such as expanding radicular cysts that may have developed from non-vital deciduous first molars or canines, are potent displacing agents for developing adjacent teeth (see Figure 11.7). Nevertheless, for most of these cases, including the extreme examples, there is no apparent local cause and it seems likely that a hereditary primary tooth germ displacement may account for the abnormal angulation of the long axis of the tooth [23]. If this angulation is between 30° and 50°, there is a good chance that the tooth will migrate across the midline in a relatively short period of time, while an angle in excess of 50° will make this eventuality virtually certain. Although there is some anecdotal evidence alleging a remarkably high speed of migration of these teeth, this is difficult to assess since these cases are usually seen postfactum and, even when seen before much of the movement has occurred, most patients will be advised to have interceptive or corrective treatment. Few will be merely kept under observation (i.e., supervised neglect!), given that a worsening of the situation seems inevitable. Interceptive treatment should generally be instituted as soon as the anomaly is discovered. The extraction of the deciduous canine may exert a positive influence to alter the orientation of the aberrant permanent canine. By also extracting the first deciduous molar, the first premolar may often be influenced to erupt early, assuming it has about half of its expected root development. This will have the effect of providing more space in the alveolar bone distal to the canine because, with the eruption of the tooth, the broader diameter of the crown will have given way to the

narrower root diameter adjacent to the canine. Removing a non-vital deciduous canine or first molar, particularly if these had been associated with an unresolved granuloma or with cystic change, may encourage a dramatic improvement (see Figure 11.7). When a canine has progressed beyond the mesial side of the lateral incisor, the majority of authorities have advised extraction of the canine itself, leaving the deciduous canine in place. Alternatively, if the case is considered to be an orthodontic extraction case, this tooth will be tagged for extraction rather than the more usual choice of a premolar. Corrective orthodontic treatment may seem to be the best choice, but this is likely to be disappointing, particularly if the tooth is on the labial side and has migrated mesially, which essentially means that it has developed into a transposition. Good 3-D imaging of the area will be necessary in order to decide if orthodontic treatment can provide a good answer. The periapical radiograph will most often provide adequate qualitative information regarding the mandibular canine, unless it is very deeply displaced. This is because it may not be possible to insert the film sufficiently deeply into the lingual sulcus. In these cases, a panoramic view may provide a better view of the tooth and its mesio-distal orientation. A true occlusal view will be required to provide the third dimension needed to accurately localize the tooth and it is important to remember that the central ray of the X-ray machine should pass along the long axes of the mandibular incisor teeth for this view to be of value. In the midline region, the missing aspect will be depicted on the lateral cephalogram that will have been taken to assist in the diagnosis and treatment planning of what initially appeared to be routine orthodontic treatment (Figure 8.7). In this type of case, extraction may sometimes be the only practical line of treatment. Given the presence of the roots of adjacent teeth immediately superior to it and the narrow dimensions of the mandibular body in this area, there may be inadequate room for successful orthodontic manoeuvre, particularly when a partial or complete transposition of teeth is to be corrected. A parallel anomaly occurring in the maxillary arch will usually be much more amenable to treatment, because the impacted tooth may be temporarily moved from the narrow alveolar ridge inwards into palatal bone to permit the movement of an adjacent tooth. For most of the impacted mandibular canines, however, the radiographic evaluation will indicate a reasonable prospect for orthodontic alignment. In line with the general principles set out in Chapter 4, an orthodontic appliance is placed and space is prepared in the arch to accommodate the tooth before its exposure is undertaken. Lingually impacted mandibular canines will almost invariably be found with their root apex in their normal location and the lingual displacement of the crowns of the teeth is due to an abnormal orientation of the long axis – a

Other Single Teeth  219 

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(c)

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(e) Fig. 8.6  (a) The left mandibular canine has been grossly displaced distally and inferiorly because of an odontome, and is in close association with the lower border of the mandible. (b) A true occlusal view of the canine/premolar area. (c) After alignment and space-opening, surgical removal of the over-retained deciduous tooth and odontome has permitted attachment placement. (d) Rapid improvement in position has occurred. Note the deleterious effects on archform and midline due to the use of a base arch of inadequate gauge. (e) A periapical view in the latter stages of resolution. Note that the tooth has responded well, despite having been covered with repaired and calcified bone after attachment bonding at the time of the closed exposure.

220  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c) Fig. 8.7  (a) Panoramic view of the mandible with mental region – the contrast of the mid-section over the chin has been altered to show the horizontally impacted canine, with compound odontome. (b) Cephalometric radiograph shows the canine to be completely horizontal and at 90° to the mid-sagittal plane and the film. (c) Occlusal view of the anterior mandible.

tipping displacement. Therefore, orthodontic realignment involves merely a corrective tipping movement of the crown in a buccal, extrusive and, possibly, distal direction. The tooth should be exposed, an attachment bonded to the buccal aspect and the wound fully closed with the sutured flap, unless the tooth is very superficial. In this way, traction from the attachment direct to the labial archwire is all that is needed to bring it to its place. The wire ligature pigtail, tied to the bonded attachment at the time of surgery, is rolled downwards to form a loop, close to the sutured gingival tissues. An elastic chain is placed across the span between first premolar and lateral incisor, and its middle portion is stretched downwards with a haemostat or ligature director and ensnared in the rolled down pigtail. This provides a light, easily measurable and vertically directed force on the impacted tooth, with a wide range of action. Alternatively, an auxiliary nickel–titanium wire may be passed through this rolled-down pigtail and through the brackets of a number of teeth on each side, under the main arch, to achieve the same effect.

Migration, transmigration and transposition Mupparapu [21] has attempted to classify buccal canines – teeth that are remarkably prone to the most bizarre eruptive movements – into five types, as follows: 1. Mesio-angular, lying inferiorly to the front teeth and, with its crown crossing the midline and termed a transmigrated tooth. 2. Impacted horizontally below the apices of the incisors. 3. Erupted mesially or distally to the contralateral canine. 4. Impacted horizontally below the apices of the contralateral canine and premolars. 5. Vertical, coinciding with the midline. It is the only type which may be declared a true transposition ab initio, rather than as the result of migration. A special case, therefore, must be made for the buccally displaced mandibular canine, migrated, transmigrated or transposed mesial to the lateral incisor. Although very uncommon, it is the most frequent form of transposition

Other Single Teeth  221  in the mandible, aside from third molars. The crown of the canine will need to be moved buccally in order to sidestep the lateral incisor root, before being moved towards the archwire. As with the parallel situation in relation to the buccally displaced maxillary canine, the orthodontic and periodontic prognoses of treatment for these teeth deteriorate in inverse relation to the amount and type of mechanotherapy used. Nevertheless, in a minority of these patients, full resolution of the transposition may be successfully achieved provided the cases are carefully selected, taking into consideration the periodontal prognosis, in addition to the biomechanics. In theory, it is possible to apply appropriate tipping and bodily movements to move the tooth back from whence it has clearly come. However, the more horizontal the tooth, the greater will be the need for a large component of force being applied through its long axis – a horizontal ‘intru-

sion’, which is clearly futile. The tooth will also need to be drawn below the incisor apices with its crown exposed in highly mobile mucosa and in the deepest part of the labial sulcus. Even the more amenable mesially migrated canines will need to be drawn distally and occlusally, but also laterally in order to skirt the roots of one or more incisors. Once the crown of the tooth has been brought to its place in the arch, the canine root must be distally uprighted and finally lingually torqued to an appreciable degree. Given in the best circumstances, it will be appreciated that it is unlikely there will be much bone covering the root on the labial side of the treated tooth, its clinical crown will be long and the marginal soft tissue on the labial side will be largely devoid of attached gingiva. Treatment will have been inordinately long to achieve an acceptable orthodontic result, but it will be accompanied by a poor periodontal outcome (Figure 8.8).

(a)

(b)

(c)

(d)

Fig. 8.8  (a) A transmigrated mandibular left canine has traversed the midline, with over-retained deciduous canine and odontome. (b) At surgical exposure, the canine is located inferior to the right central incisor and is situated below the depth of the sulcus. (c) In the final stages of orthodontic treatment aimed at completing the uprighting of its root and lingual root torque, the clinical crown is very long due to gingival recession and there is deep periodontal pocketing on the mesial side of the canine. (d) Root paralleling of the teeth is good, but apical root resorption is present on all teeth carrying orthodontic attachments. There is crestal bone loss in the immediate area of the affected canine. The periodontal prognosis of this tooth contrasts sharply with the success of the orthodontic treatment.

222  Orthodontic Treatment of Impacted Teeth There remain three additional and alternative lines of treatment for the non-crowded case. The clinician may: 1. extract the canine, leaving the deciduous canine in its place, provided its root is of reasonable length and prognosis; 2. extract an incisor and align the canine in its place, leaving the deciduous canine in place; 3. align the two teeth in the transposed relationship which, in the mandibular arch, may offer the optimal solution [24–27]. In the presence of crowding, extraction of the deciduous canine and the adjacent permanent incisor, or of the deciduous canine and the permanent canine, should be considered in addition (or in preference) to a more conventional choice. The space provided may then be used for the relief of crowding as an integral part of a comprehensive orthodontic treatment programme that includes other aspects of the malocclusion. One final thought in regard to transmigrated mandibular canine relates to its innervation. It should be remembered that, regardless of the distance it travels, the tooth takes with it the blood vessels and nerve supply with which it started out life. This needs to be taken into account when considering the surgical exposure or removal of the tooth under local anaesthetic cover.

Mandibular second premolars Crowding and space loss Perhaps the most common cause of impaction of the second mandibular premolar is the early extraction of its deciduous predecessor, although this has become less common with the decline of caries in the Western world. With the loss of the second deciduous molar, the adjacent permanent molar will usually tip mesially and ‘roll’ lingually. Additionally, there will be a degree of distal drifting of the first deciduous molar of the same side, but total elimination of the space for the second premolar does not often occur. The result will be that this successional tooth will be blocked from erupting into the line of the dental arch. Given that its early developmental position is slightly lingual to the line of the arch, and that it is prevented from migrating upwards in the normal manner, it either will move more lingually and erupt on the lingual side, or it may remain impacted and beneath the ‘pitched roof ’ formed by the two adjacent erupted and tilted teeth. The radiographic method for these cases is very similar to that described for mandibular canine teeth. The periapical film is used to provide detail but, in the mandibular premolar area, it also provides a lateral horizontal view in this area. In theory, therefore, it may be supplemented by an occlusal view to provide the third dimension and enable

accurate localization. Unfortunately, the occlusal view has the X-ray beam passing through the full thickness of the body of the mandible and, unless the tooth is markedly displaced to the lingual or buccal side it will not be possible to differentiate it from the mass of bone. If its presence can be confirmed in the periapical view and there is no clear view of the outline of the tooth on this film, it will be safe to assume the tooth to be close to the line of the arch and undeviated buccally or lingually. Alignment requires space, and this may be achieved by re-siting the drifted teeth back in their former or improved positions using a fixed orthodontic appliance with a coil spring. This may often require intermaxillary (class 3) traction to reinforce the anchorage of the lower jaw and to prevent undesirable incisor proclination. Alternatively, extraction may sometimes be necessary, in which case the impacted tooth or its immediate premolar neighbour may be the tooth that will be sacrificed along with a matching tooth in the other three quadrants of the mouth, in order to treat the overall malocclusion. Given space by distal movement of the molar and/or by mesial movement of a distally tipped first premolar or by extraction of the adjacent premolar, an impacted premolar tooth will normally erupt with considerable speed without further assistance. From the periodontal point of view, surgical removal of unerupted mandibular second premolars, which may be needed in an extraction case, may leave a marked bony defect in the area, even after the excess space has been closed and adjacent teeth have been fully uprighted. This may be accompanied by a deep mucosal fold or cleft in the interproximal area in the site where the extraction had been made. This may disappear once space closure has been completed, although it may persist and thus prevent the regeneration of bone in the interproximal area, to cause a periodontal defect. Abnormal premolar orientation The second deciduous molar of the lower jaw has much to answer for in relation to the non-eruption of its permanent successor, not merely when it is prematurely lost due to the ravages of caries, but also when its presence is abnormally prolonged. The second premolar tooth germ is not always in its ideal developmental position, directly between the mesial and distal roots of the deciduous molar. Indeed, an abnormal angulation or location seems to be a frequent finding. The premolar may often be tipped more distally, initiating resorption of only the distal root, leaving the mesial root of the deciduous molar largely intact. This will lead to over-retention of the deciduous tooth, often despite the complete disappearance of the distal root and much of the coronal dentine. A periapical radiograph will show the long-rooted premolar very superiorly positioned, almost

Other Single Teeth  223  inside the distal part of the crown of the deciduous tooth, whose long and thin spicule of the mesial root remains, grimly resisting exfoliation. A parallel scenario may occur with resorption of the mesial root due to mesial tilt of the second premolar from early on in its development, although it seems to enjoy a lesser frequency. In either of these cases, as long as the degree of tilting is relatively slight and the tooth is relatively high up in the alveolus, the extraction of the deciduous tooth will usually suffice to achieve the rapid and trouble-free eruption of the premolar tooth. Space is never a problem in these cases, since the second premolar has a smaller mesio-distal crown width than its healthy predecessor. A premolar tooth which has a stronger distal tilt is usually situated more apically, and the distal-occlusal aspect of its crown is in close relation with the mesial root of the first permanent molar. The second deciduous molar is usually over-retained at the time of detection and more than adequately holding the space in the arch (Figures 8.9 and 8.10). In terms of aetiology, it has been found that an exaggerated disto-angular malposition of the unerupted mandi­ bular second premolar is associated with agenesis of its antimere [28] and with retarded dental development. In Chapter 6, we have alluded to the existence of a connection between second premolar anomaly and palatally displaced canines, which are similarly affected by late development. It seems that individuals with both maxillary canine and mandibular second premolar anomalies suffer greater delay in dental development [29]. In these cases, a space-holding device should be used when the deciduous molar is removed to prevent tipping of the permanent molar, and an attempt may also need to be made to upright the premolar. An appropriate spacemaintaining device may be designed in many ways, but, classically, a buccal and lingual bar may be soldered to two bands to form a simplified fixed bridge, which is then cemented to these teeth. Alternatively a single rigid bar, with terminal loops or a mesh pad at each extremity, may be bonded to the buccal surface of the first molar and first premolar. This is a fairly good alternative provided it is well clear of the occlusion, although it may still become debonded by occlusal forces transferred through bulky and hard foods. Because of its small size, the debonded bar with terminal loops on a mesh pad presents a potential hazard, since it may be ingested or, worse, inhaled by the patient. At surgery, only the mesial and occlusal aspects of the impacted and distally tipped premolar tooth are exposed and, where possible, an eyelet should be bonded to this area of the crown of the tooth, carrying a twisted steel pigtail ligature. The tooth is fairly deep down and an open exposure is likely to leave the mesial root of the first molar exposed and devoid of attachment. For this reason, the flap should be completely sutured back into its place and the

(a)

(b)

(c) Fig. 8.9  (a) A late-developing left second premolar, horizontally oriented. (b) A year later, the tooth has moved distally to overlap the mesial root of the first permanent molar. (c) Extraction reveals some resorption of the mesial root of the molar. (Courtesy of Professor Y. Zilberman.)

224  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c) Fig. 8.10  (a–c) Serial periapical views of a failed attempt to bond an edgewise bracket to an inadequately developed second mandibular premolar. (Courtesy of Dr D. Harary.)

stainless steel ligature wire pigtail, ligated through the bonded eyelet, becomes the means of applying force to the unerupted tooth. An elastic chain may be stretched between a hook on the fixed band of erupted first premolar and first molar, parallel to and overlying the rigid bar. Once in place, the middle of the elastic chain is drawn downwards with artery forceps and ensnared in the pigtail ligature to apply a vertical erupting force to the impacted tooth. The greater the degree of movement required, the more substantial must be the anchor base, and, where indicated, a fixed lingual arch to the opposite molar may be advisable. This region of the mouth does not provide easy access to permit acid etch bonding and, particularly when the orthodontist is not present to do this part of the surgical procedure, eyelet attachment may not be possible (Figure 8.10). When this is the case, more radical surgical compromises may have to be made in order to salvage the tooth. Wider exposure is indicated and a buccal or lingual extension to the exposure may be needed, depending on the orientation of the tooth (Figure 8.11). This will then hopefully provide the needed access for bonding the attachment, with a satisfactory degree of reliability. Because of the difficulty in bonding, it is common practice to use an open exposure procedure, leaving the tooth exposed but covered with a surgical pack, particularly distally where the pack is wedged between the premolar crown and molar root. The pack is designed to remain in place for two or three weeks to prevent healing over of the gingival tissues. The deliberate wedging of gauze into the distal area helps to divert the eruption path of the premolar in a more mesial direction; subsequent eruption may then occur spontaneously. As was pointed out in Chapter 3, however, these procedures will make the establishment of an ideal periodontium unlikely for both the molar and the premolar because the open surgery will have left the mesial side of the mesial root of the molar exposed to the detriment of its final periodontal status. It is to be expected that the clinical crown of the premolar will, in the final erupted position, be longer, the gingival attachment and architecture compromised, the bone support reduced and the prognosis poorer than normal. While there are many impacted second premolars that may be treated in this way, success cannot be expected in some of the more extreme cases and the tooth has to be extracted. On occasion, extraction of the tooth is advised for other reasons, both objective and subjective. Care should be taken to follow up these cases once diagnosis has been established, since there may be a danger of resorption of the mesial root of the first molar, if the tooth is left untreated without suitable and long-term radiographic supervision (Figure 7.3). A lingually ectopic second premolar that is low down in the floor of the mouth and has migrated mesially in relation

Other Single Teeth  225 

(a) (b)

(c)

(d)

Fig. 8.11  (a) The left second premolar is impacted due to loss of space in the dental arch due to extraction of the second deciduous molar three years earlier. Both mandibular second premolars are very late-developing, relative to the other permanent teeth and both are strongly distally tipped. Note the associated bilateral palatally impacted maxillary canines. (b) A periapical view shows bonding of an attachment to the right second premolar was achieved only after wide exposure. (c) A similar follow-up radiograph shows improvement in the position of the tooth, but crestal bone height is deficient. (d) A panoramic view of the final stages of treatment clearly shows the reduced periodontal prognosis of the right mandibular second premolar. (Courtesy of Dr L. Rothstein.)

to the adjacent teeth is less commonly seen than the distally drifted teeth. In either case, direct traction to the labial archwire will not be practical. In these situations, the use of the same auxiliary labial arch – always as an addition to the main base arch, as noted above (Figure 8.12) and as recommended for many palatal canines – has excellent application and can be used with great efficacy to provide the vertical and distal eruptive components (Figure 8.13).

Maxillary second premolars The most common reason that these teeth become impacted, as with the mandibular second premolar, is

related to space loss in the dental arch following the early extraction of the deciduous second molar and the drifting of the two adjacent teeth, particularly the first permanent molar. It is also true that mesial movement of the first permanent molar in the maxilla is more rapid than occurs in the mandible, it more completely closes off the space and it does so by mesial tipping and a mesio-lingual ‘rolling’, even in the late mixed dentition stage. When, therefore, space has been lost, the maxillary second premolar is most often to be seen developing with its root apex in the line of the arch and its crown deflected palatally, palpable on the palatal side of the alveolar process. As with the mandibular second premolar and the lateral incisors of

226  Orthodontic Treatment of Impacted Teeth

2

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(f)

(j)

Fig. 8.12  (a) Panoramic view showing impacted right second mandibular premolar tipped 60° distally, overlapping the mesial root of the first molar. Note the missing maxillary right second and all four third molars, peg-shaped left second maxillary molar. (b) Axial slice from the CBCT shows the second premolar situated lingual to the roots of the first molar (arrowed). (c) At surgery, the deciduous molar is removed and the premolar exposed deep in the lingual sulcus in the floor of the mouth. (Surgery by Prof. R. Seltzer.) (d) An attachment is bonded. (e) The auxiliary labial arch is shown in its vertically passive mode and the pigtail ligature may be seen on the lingual side of the alveolus. (f) The auxiliary labial arch is engaged in the pigtail ligature after the full flap is replaced and sutured, exerting a vertical and slightly lingually directed force, to draw the tooth away from the molar tooth. (g) The tooth bulges the lingual mucosa more superiorly re-exposing the eyelet. Mesial traction is applied to the labial archwire at a point between canine and lateral incisor, to circumvent the mesial root of the molar tooth. (h) Elastic traction is applied direct to the archwire to de-rotate the tooth as it moves buccally. (i) The premolar moves into the arch, with much correctional rotation. (j) Completion of the alignment has been achieved and an orthodontic bracket has been substituted for the initial eyelet, to permit control of root movement.

Other Single Teeth  227 

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 8.13  (a–d) The initial radiographs including panoramic, lower occlusal views and partial views of lateral and postero-anterior cephalograms. (e, f) The auxiliary arch is placed in passive mode prior to surgery. (g, h) The mandibular premolars are exposed and bonded with eyelet attachments. Plastic tubing threaded onto the base arch holds the regained canine space. Because of their superficial positions, the second premolars were left partially exposed, while the first premolars were fully recovered with the surgical flap. (Surgery by Prof. J. Lustmann.) (i) Occlusal view of the lower jaw one week after the exposure of the teeth. The loops on the auxiliary arch are seen in their active mode, hooked round the pigtail ligatures of the first premolars. The more superficial second premolars are ligated with elastic ligature direct to the buccal hooks on the molar bands. Plastic tubing threaded onto the base arch holds the premolar space bilaterally. (j, k) Occlusal and panoramic radiographic views of the postoperative condition. (l–n) The finished case 25 months after completion of treatment. (o) Panoramic view taken 25 months post-treatment. Note the abnormal crown–root angulations and root dilacerations of the treated mandibular premolars. (p) Partial view of post-treatment lateral cephalogram.

228  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(i)

(j) Fig. 8.13  (Continued )

(k)

Other Single Teeth  229 

(l)

(m)

(n)

(o)

(p) Fig. 8.13  (Continued )

230  Orthodontic Treatment of Impacted Teeth both jaws, the developmental position of the maxillary second premolar is lingual to the line of the arch and any physical limitation in the mesio-distal width of its normal eruption path will tend to deflect the tooth in a more palatal direction. Palatal displacement can occur with over-retention of the deciduous second molar; it can also occur when there has been a more palatal orientation of the tooth bud of the unerupted premolar in its early development. The outcome may be its eruption or partial eruption at the palatal aspect of the cervical margin of the over-retained deciduous tooth. Alternatively, it may become more horizontally oriented, to remain unerupted and, occasionally, very palpable close to the mid-palatal suture. Because of the oblique angle of the X-ray tube in the vertical plane in periapical radiography of this area, the palatally tipped and unerupted second premolar will be viewed almost through the long axis, which may give the appearance of a short and underdeveloped root and, with a more exaggerated palatal tip, will be depicted on the film as an ellipse. This being the case, it is probable that further X-ray films are not necessary, particularly if the tooth is palpable in the palatal area. The conventional (oblique) occlusal film or a second, laterally shifted periapical film will offer the opportunity to add three-dimensional information. Both a postero-anterior cephalogram and the true vertex view would be more decisive, but the relatively high dose of radiation needed for these views should be considered excessive in relation to the information that they may provide in this situation. Nevertheless, if these views are available, they must be studied for any relevant information. In Chapter 2, we pointed out that a panoramic view of the maxillary second premolar area is taken when the X-ray beam is directed from behind the patient’s ear of the opposite side, which means that a palatally displaced second premolar will be imaged further mesially in relation to its erupted neighbours. If, at the same time, the lateral cephalometric view shows the tooth to be in its normal position, then the diagnosis of palatal displacement will have been confirmed in what is essentially another form of the tube shift parallax method (buccal object rule). Infra-occlusion of deciduous teeth and its influence on premolar successors Infra-occlusion of deciduous molars in either jaw is a relatively common occurrence and the affected teeth are known to shed quite normally in most cases, with only a relatively minor delay in their exfoliation time [30, 31]. The cause of the phenomenon is a local ankylosis at some point or area of the root of the tooth. The tooth will not then alter its position or develop vertically along with the adjacent teeth, which continue their passive eruption as vertical growth of

the alveolus progresses. The result is that the affected tooth becomes relatively ‘submerged’ or infra-occluded. Attempts to move these teeth and to overcome the infraocclusion by orthodontic means will fail and it is rarely possible to identify the site or extent of the ankylotic connection. Indeed, it is rarely a task that the orthodontist will need to or be called on to perform for as long as an unerupted permanent premolar is present. On the other hand, such a tooth may be used as an anchorage for the movement of other teeth without fear of unwanted movement, since it behaves very much like a temporary anchorage device. When the infra-occlusion is very marked, an extreme vertical displacement of the apically placed successor will also occur, as has been discussed earlier in this chapter. Indeed, in the mandible the apex of the root of the developing premolar may even cause a palpable prominence in the otherwise smooth profile of its lower border [32]. In these cases, extraction of the infra-occluded tooth should be made in line with the appropriate development of the root of the permanent successor, or earlier if the location of the premolar is abnormal, since the deciduous tooth may have been the cause of the ectopic location. It is often quite impractical to attempt to bond an attachment to many of these grossly displaced premolar teeth. However, their position generally improves quite dramatically once the deciduous tooth has been removed, usually in a reasonably short time. No studies or even case series have appeared of these extreme cases in the literature and opinions are strongly influenced by single published case reports or individual practitioner clinical experience. However, there would appear to be merit to a wait-and-see policy and some cause for optimism in these very special circumstances (Figure 8.14) following space opening and extraction of the infra-occluded deciduous tooth. Fortunately with infra-occluded teeth, actual space loss within the mandibular dental arch is very minimal, despite the obvious fact that the teeth adjacent to an infra-occluded tooth are often severely tipped towards it. The reason for this is that there is a displacement of the roots of the teeth immediately adjacent to the infra-occluded tooth, away from the affected tooth, with little or no approximation of their crowns [33–35]. Once the infra-occluded tooth is removed, space loss may be quite rapid and a space maintainer should be placed. No attempt should be made in the first instance to uncover the very deeply placed premolar but, following the removal of the deciduous tooth, the patient should be followed over a long period of time, with an occasional periapical radiograph taken to check for eruption progress. Infra-occluded deciduous teeth are associated with a lack of alveolar bone height in the immediate area. The height from the inferior border of the mandible to the occlusal table is significantly reduced, when compared with the normal, unaffected, opposite side. The height of the

Other Single Teeth  231 

(a)

(b)

(c)

(d)

(e) Fig. 8.14  (a) At age 6 years, all the deciduous molars appear infra-occluded to a greater or lesser degree, as can be seen in relation to the erupted deciduous canines. (b) At age 8 years, the first molars have erupted with mesial inclinations and the deciduous teeth have further infra-occluded. (c) At age 10 years, the infra-occlusion has increased and the permanent molars have developed a strong mesial inclination. Note that the maxillary second premolar tooth buds are mesially displaced and have caused total intra-coronal resorption of the maxillary second deciduous molars. (d) Nine months later, root treatments were performed on the recently traumatized incisors. Orthodontic treatment was begun to upright the molars with simple distal tipping, using a fixed lower and removable upper appliance, supported by an integral headgear. The right second deciduous molars have further resorbed and their degree of infra-occlusion has lessened, presumably due to the resorption of the causative ankylotic site. The four deciduous molars were finally extracted a few months later, when adequate space had been made. All the premolar teeth erupted spontaneously over a two-year period, while space was maintained and without the need to expose them. (e) At age 13 years, all teeth have erupted and orthodontic treatment has recommenced to bring about full alignment, particularly the de-rotation of the maxillary left second premolar. Full bony regeneration and alveolar height have been achieved. (f–j) Clinical views of the condition immediately prior to the commencement of orthodontic space opening procedures at age 10.6 years. Note severe bony defects in premolar areas, constituting a marked lateral open bite. (k–o) Clinical views of the condition at age 13 years and after eruption of the premolars. The maxillary right second premolar has a 110° rotation which is being treated in a final finishing stage of orthodontic treatment. Note full regeneration of alveolar bone height, establishment of occlusion and normal appearance of the teeth and gingivae. (p–r) Intra-oral photographs at age 16 years, two years post-treatment. (s) Panoramic view two years post-treatment.

232  Orthodontic Treatment of Impacted Teeth

(f)

(g)

(h)

(i)

(j)

(k)

Fig. 8.14  (Continued )

(l)

(m)

(n)

(o)

(q) (p)

(r) Fig. 8.14  (Continued )

(s)

234  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 8.15  (a) Characteristic extreme tipping of the teeth adjacent to an infra-occluded maxillary deciduous second molar. The second premolar is displaced superiorly and mesially, exhibiting a marked distal orientation. (b) Space regaining and maintenance, with extraction of the infra-occluded deciduous molar, has resulted in spontaneous correction of tooth position. Eruption is imminent.

teeth immediately adjacent to a severely infra-occluded deciduous molar is also reduced when compared with the height of unaffected contralateral teeth. This phenomenon has been blamed on the inclusion, by the infra-occluded tooth, of a vertical component in the normally horizontal trans-septal fibres, which inhibits their vertical development [34]. Extraction of the infra-occluded tooth initially leads to healing and bone reorganization which, in the absence of permanent teeth, will not increase the vertical height of the body of the mandible in that area. If a permanent tooth is present and begins to erupt, alveolar bone development accompanies the eruption and the vertical bony deficiency is eventually made good. However, this may be partial only and a lateral open bite may sometimes persist. Second premolars in either jaw occasionally become impacted in a situation complicated by the severe infraocclusion of the second primary molar (Figure 8.15). When infra-occlusion occurs in the very young child, the relative submergence of the tooth will occur rapidly in line with the vertical growth of the alveolar ridges, until the deciduous tooth is lost from sight beneath the gingiva. The erupting first permanent molar then migrates mes­ ially to an excessive degree and tips in an exaggerated manner, greater than would normally be seen as the result of the early extraction of a deciduous tooth. This is seemingly due to the influence of the infra-occluded tooth in the vertical plane [33–35]. Similarly, the deciduous or permanent tooth immediately mesial to the affected tooth tips strongly distally, such that the long axes of the two adjacent teeth converge coronally at an angle of almost 90°, instead of being parallel. When the practitioner comes across this type of unusually severe convergence, an infra-occluded deciduous tooth should always be suspected.

The infra-occluded tooth is now firmly locked in by the reduced space in the arch and remains there during the entire period of the resorption of its root, which normally would precede its shedding. In time, the entire dentinal contents of the crown become resorbed and the empty enamel shell remains sequestrated in situ. In the maxilla, the unerupted second premolar develops in these cramped circumstances and, with its further root growth, becomes displaced usually mesio-palatally, with its root oriented mesially. It may eventually side-step the empty enamel crown and erupt into the palate, but usually it will remain high up in the maxilla and close to the floor of the maxillary sinus. In a panoramic radiograph, the tooth may frequently be seen to superimpose on the unerupted maxillary canine of that side. Treatment of the problem is surprisingly simple (Figure 8.16). The molar must be moved distally to its ideal location to reopen the space in the arch. Since the tooth has a strong mesial tip, a removable appliance carrying a finger spring to distalize the molar is probably the most efficient appliance available for this task, particularly in the mixed dentition stage, and will usually take no more than three or four months to achieve its goal. The patient is referred to the surgeon for removal of the resorbed remains of the deciduous second molar. For this, the removable appliance may be taken out of the mouth, its acrylic base trimmed to be clear of the surgical field and, at the conclusion of the surgical procedure, replaced to retain the molar position. In the longer term, it is preferable to place a soldered lingual arch in the maxillary arch, based on two molar bands. The removable appliance itself is perfectly adequate as a space maintainer, but compliance may be a problem, particularly in the immediate postsurgical period. With the older patient, in the permanent dentition stage, a fully-bracketed fixed appliance should be used in order

Other Single Teeth  235 

(a)

(b)

(c)

(d)

Fig. 8.16  (a) The left first molar is strongly tipped mesially into the place of the second deciduous molar and out of occlusion. The first deciduous molar is distally tipped. (b) The occlusal view shows some distal drift of the deciduous first molar, canine and permanent lateral incisor. (c) The complex interrelations between the first permanent molar (6), the infra-occluded second deciduous molar (E) and the unerupted second premolar (5), first premolar (4) and permanent canine (3). Note the almost 90° angle described by the long axes of the first permanent and deciduous molars. (d) A simple removable appliance which is retained by clasps on the right permanent molar, both deciduous first molars and a labial arch. The spring is designed to move the molar distally. (e) The imprint of the spring in the palatal soft tissue can be seen, following removal of the first and second deciduous molars. (f) A soldered lingual arch holds the molar in its place in this occlusal view, taken 18 months later. The second premolar is now erupting into its place. No other orthodontic treatment was performed in this case up to this point. (g) The view from the left side on the same day.

to combine this local problem with the treatment of the overall malocclusion (Figure 8.17). Following the removal of the impediment and free of its physical constraints, the second premolar will rapidly respond spontaneously and, within a period of between several months to a year or so, it is highly predictable that it will erupt unaided into the location prepared for it in the arch. For this reason, the second premolar does not need to have an attachment placed on it, nor is it usually necessary to even expose it. In contrast to other impacted teeth, there appears to be little benefit in going through the elaborate orthodontic and surgical preparations that we have described in relation to incisor and canine teeth. Much surgical damage will be inflicted by the effort and difficulty involved in exposing and bonding an attachment to a tooth

in this location and the exercise would most often be superfluous.

Maxillary first molars In the early mixed dentition, one may occasionally see the erupting maxillary molar caught by the distal bulbosity of the adjacent deciduous second molar (Figure 8.18). This is usually an early sign of crowding of the dentition, although it may simply be due to an abnormal mesial tilt of the first molar. Clinically, the essential diagnostic criterion is that the marginal ridges of the two adjacent teeth are at different levels, with that of the deciduous tooth being more occlusally placed. In the severer cases, the mesial marginal ridge of the permanent molar is unseen beneath the area of the

236  Orthodontic Treatment of Impacted Teeth

(e)

(f)

(g) Fig. 8.16  (Continued )

(a)

(b)

Fig. 8.17  (a) The panoramic view of a 17-year-old female with missing mandibular second premolars and third molars and with infra-occlusion of three premolars. In the upper right side, the vertical and mesial displacement of the second premolar is evident. (b) The patient underwent the surgical removal of the deciduous second molars before being referred to the author for treatment. (c–e) The initial intra-oral views. (f) The bracket placement jigs demonstrate the 90° angulation between the long axes of first premolar and molar. (g) Five months later, levelling, alignment and space-opening has been prepared in the maxilla and the second premolar may already be palpated as a bulge in the buccal area above the archwire. (h) Seven further months later and without surgical exposure, the second premolar has erupted and is in its place in the arch. (i–m) Intra-oral views of the completed orthodontic treatment on the day appliances were removed. (n) Panoramic radiograph of the treated result on the same day.

Other Single Teeth  237 

(d) (c)

(e)

(f)

(g)

(h)

(i) Fig. 8.17  (Continued )

(j)

(k)

238  Orthodontic Treatment of Impacted Teeth

(l) (n)

(m) Fig. 8.17  (Continued )

distal CEJ of the deciduous tooth. At best, the distal cusps may be in occlusion with the mandibular molars, but usually the impaction prevents adequate eruption for this to occur. In rare instances, the permanent molar is completely prevented from erupting and does not break through the mucosa. A periapical or panoramic radiograph of the area will usually show that most or all of the distal root of the deciduous second molar has been resorbed, and the general long axis and path of eruption of the permanent tooth to be tipped too far mesially. To leave a partially erupted molar tooth without treatment is to invite caries in the large stagnation area that has been created between it and the deciduous molar, which serves to compound the existing potential gingival/pulpal problem in the area of contact. In general, the mesial and palatal roots of the deciduous second molar remain intact, which generally suffices to retain this tooth in its place. If the deciduous second molar is shed prematurely or is extracted, the permanent molar will move rapidly forward, significantly closing off the space vacated by the lost tooth within a few short months. The tooth also erupts occlusally at the same time, and its movement has a significant forward translation component, in addition to its mesial tip. With its centre of rotation more mesially placed on the ridge, orthodontic treatment to push the tooth back to its ideal position after full eruption will generate an excessive distal tip to the molar, which will leave the roots too far mesially. Second, the achieved space will need to be maintained for

around five years, until all the successional teeth have erupted. Regardless of how well designed and constructed the proposed space-maintaining device may be, its placement in a 7- or 8-year-old patient must provide some concern vis-à-vis its deleterious effect on the long-term prognosis of the first molar. Many original ideas and gadgets have been suggested to disimpact the ectopic first molar from beneath the distal bulbosity of the deciduous second molar, and the simplest of these has been to use an elastic separating ring or other form of orthodontic separator, which is normally used to create spaces to facilitate banding. This may be successful in some of the very mild cases, although what frequently happens is that a space between the teeth is produced within a week or so after placement of the ring. The elastic ring is then removed to allow the permanent tooth to erupt occlusally. In many cases, the molar tips right back into its previously impacted position and nothing will have been achieved. This type of relapse may occur with any method that is only concerned with tipping the tooth distally, without providing for a retention period. The retention period is essential in order to permit additional eruption of the affected molar, while preventing re-impaction. A fixed device has several apparent inherent advantages, but it must be remembered that the patient is a young child, who may be relatively unwilling to cooperate in its construction and placement. Furthermore, most orthodontists do not have a selection of preformed deciduous second molar bands, and

Other Single Teeth  239 

(a)

(b)

(c)

(d)

(e)

(f)

(g) Fig. 8.18  (a) Incomplete eruption of the maxillary first permanent molar, due to abnormal angulation of its long axis. It has become impacted beneath the distal bulbosity of the deciduous second molar. (b) The removable appliance carries five retention clasps and a palatal ‘finger’ spring that traverses the occlusal surface of the partially erupted first molar. An acrylic button is placed on that portion of the spring that comes into contact with the occlusal surface of the first molar. (c) The incompletely seated appliance shows the spring in its passive mode, distal to the molar. (d) The patient has brought the spring mesially, prior to fully seating the appliance. (e) The molar is disimpacted and in full class 2 occlusion. (f, g) Lateral oblique extra-oral films before and after treatment show the advanced resorption of the second deciduous molar.

240  Orthodontic Treatment of Impacted Teeth the placement of a band on the permanent molar is impossible in all but the simplest of cases. Suitable conditions for composite bonding are also exceptionally difficult to attain in the molar area of such a young child and results are unreliable. Nevertheless, appliances have been designed which are based on a fixed band on the deciduous second molar only, or on an additional fixed band on the second deciduous molar of the opposite side, through the agency of a soldered palatal arch. A soldered spring is formed on a model, which fits into the most convenient and deepest occlusal pit of the ectopic molar and activated prior to cementation of the appliance [36]. It is quite difficult to readjust this spring in the mouth, which may make this a one-time activation appliance, unless the whole cementation process is repeated. At first glance, a removable appliance seems inappropriate, since there appears to be no way of passing a cantilever spring across the interproximal area, mesial to the tooth, to apply the needed distal force. However, the removable appliance offers excellent ways of overcoming the drawbacks described above (Figure 8.18) [37]. Good retention is necessary, and this is best supplied by placing an Adams clasp on the second deciduous molar of that side, on the erupted first permanent molar on the opposite side and on the two central incisors. Additionally, a three-quarter circumferential clasp placed on the first deciduous molar usually offers excellent retentive support. On the plaster model, a simple cantilever spring is drawn across the erupted portion of the occlusal surface of the impacted molar, mesial to the palatal and between the two buccal cusps. In the area of the mesial occlusal pit, a dab of acrylic is cured onto the spring to adapt it to that surface of the tooth. Activation of the spring is made after the patient has experienced the passive appliance for a couple of weeks or so and is taught how to place the appliance with the spring in its appropriate place. The tooth will generally move distally and disimpact from the deciduous molar within a few weeks. At that time the spring is altered in shape to enter the newly accessible interproximal area between the two teeth and, once there, to maintain the molar position while allowing its eruption. When the permanent molar has reached occlusal level, the appliance may be discarded since, at this point, the presence of the second deciduous molars will prevent relapse. In the more severe cases of this type, the resorption process will have completely eliminated the distal root of the deciduous molar and, if careless probing is performed with a sharp explorer, perforation at the distal aspect of the deciduous molar is very likely to occur. Clinically, the sharp enamel edge at the cervical margin of the crown and the abrupt absence of continuity may be quite obvious in the same way as is seen with any deciduous tooth immediately prior to its normal shedding. In this area, former pulpal tissue will have merged with the surrounding gingival tissue. Inflammation of this tissue at this juncture

will, therefore, no longer give rise to a pulpitis and it will repair symptom-free, as with any other injured gingival tissue. In the cases of this type with which we have had experience there have been no adverse clinical symptoms related to the deciduous second molar tooth; nor has periapical radiolucency been evident on X-ray to suggest pulp death. Extraction has not been required and the tooth has remained to act as a natural space maintainer until shedding has occurred at a much later stage, closer to the normal shedding time and late enough to find the second premolar erupting rapidly thereafter. This is preferable from every point of view to extraction and replacement by an artificial space maintainer. To find the parallel situation in the first permanent molar of the mandibular arch is very rare. However, management would be very similar to what has been described for the maxillary first molar.

Mandibular second molars Impaction of the mandibular second molar is uncommon, but when it occurs it is very similar in its appearance to that so frequently associated with third molars. Unlike the maxillary first molar, the mesially impacted mandibular second molar is frequently unerupted and it usually comes to light in a routine dental examination, when it shows up on the bite-wing radiographs. A periapical film or a panoramic scan will show detail of the tooth from crown to apex and its relationship with the unerupted third molar. The tooth may also have a buccal or lingual tilt, which will generally be revealed by palpation, although an occlusal view will serve to confirm. Clues to a lingual inclination may also be seen on the panoramic view, since it is easy to distinguish between the form of the lingual cusps and that of the buccal cusps. It is also unusual to see a vertical discrepancy of any magnitude in the superimposition of the buccal cusps and the lingual cusps of each molar tooth. Thus, when the lingual cusps are seen to be much lower than the superimposed buccal cusps, one may conclude that the tooth has a strong lingual inclination. There are several aetiological possibilities and these may be listed as follows: 1. Wide molar crown contour: The teeth of some patients may sometimes show unusually wide crowns sited on narrow roots, which results in a deep concavity on both mesial and distal aspects of the teeth concerned. In the molar region, this presents the unerupted distallyadjacent molar with a potential cul-de-sac beneath the distal bulbosity, into which it may migrate in its mesial and vertical eruption path (Figure 8.19a). 2. Abnormal mesial angulation of the second molar tooth germ: The crypt of the developing second molar may sometimes be seen, ab initio, to have a mesial orienta-

Other Single Teeth  241 

(b) (a)

(c)

(d) Fig. 8.19  (a) Bulbous crown of second molar entrapped by similar contour of first molar. (b) Abnormal mesial angulation probably the result of abnormal crypt orientation. (c) a developing second molar mesio-angular impaction radiographed in 2002 and then in 2006 to show influence of third molar developing with a mesial angulation in the vertical ramus and its subsequent mesial migration. (d) Ramal development of the third molar has reduced the width of the eruption path of the second molar, to cause its vertical impaction. (e) A dentigerous cyst encompasses the crown of the second molar. (f) Two panoramic views of the same patient taken a year apart. The right mandibular second molar is relatively more infra-occluded and a gap has developed between it and the first molar. These are clear signs of ankylosis. (g) An odontome has displaced the molar to the lower border of the mandible, from where it is palpable externally. (h) CBCT images show the close proximity and encirclement of the inferior alveolar nerve bundle by the roots of the second molar.

tion. From this compromised position, the tooth will generally continue to progress along an eruption path that has been thus determined (Figure 8.19b). 3. Posterior crowding, with the third molar developing in the vertical ramus: Teeth normally develop in the alveolar bone of the horizontal body of the mandible. When crowding exists, it may be present in the incisor region, with the teeth developing, erupting and competing for space on the anterior rim of the two dental arches between the deciduous canines of each side. In the retromolar area of the mandible, it will be recognized by the third molar being located in the vertical ramus at a

higher level than would be expected and with a marked mesial rotation of the tooth bud. Any expression of eruptive potential will be directed mesially, towards the second molar, effectively pushing this tooth to tip mesially and become lodged below the distal bulbosity of the first molar (Figure 8.19c, d). 4. Mesial/distal root length differential: It has been noted that mesial angulation of what appears to have been a normally erupting second molar is seen frequently in these cases and it seems to occur quite late in its eventually unsuccessful eruptive progress. As this edition goes to press, an association has been recognized between the

242  Orthodontic Treatment of Impacted Teeth

(e)

(f)

(g)

(h)

Inferior dental canal

Fig. 8.19  (Continued )

development of a mesial root which is shorter than the distal root. Similarly, distally angulated second molars are associated with a shorter distal root. Assuming that the two roots develop at the same time and at the same rate, it is reasonable to speculate that a longer mesial or distal root will continue to grow after the other has apexified, thereby contributing a factor for change in the orientation of the tooth in the opposite direction [38]. 5. Heredity: This same study found an autosomal dominant hereditary factor, which was noted in comparing two different population samples [38]. There is almost certainly a considerable overlap in the five aetiological factors of this list so far and it may be that a given case could be associated with two or more of these

potential causes combined. This may make difficult the intellectual exercise of deciding which was the precipitating factor. 6. Enlarged follicle/dentigerous cyst: As we have noted in regard to maxillary canines (see Chapter 6), an enlarged follicle or dentigerous cyst will often be associated with non-eruption. This is because the intra-cyst pressure overcomes the natural eruption force of the tooth (Figure 8.19e). 7. Ankylosis: As with any other impacted tooth, this diagnosis is a rare and unlikely aetiological factor. Its presence will mean that orthodontic force to erupt the tooth will be unproductive and this may serve to confirm a tentative diagnosis (Figure 8.19f).

Other Single Teeth  243  8. Other local pathology (Figure 8.19g). 9. Root entanglement with the inferior alveolar nerve (figure 8.19h). Local treatment If the third molar is implicated in the impaction, or if a mesial and superior positioning of the third molar secondarily prevents the eruption of the second molar, then extraction of the third molar is obligatory. Following this step and in the absence of further treatment, the second molar will frequently be seen to improve its position and its spontaneous eruption is certainly possible. On the other hand, this would pass up the opportunity to place an attachment on the second molar at the time of the third molar enucleation and mandate a second exposure if the tooth did not erupt. Corrective orthodontic treatment is nevertheless often needed and, if it is to be performed on a local basis only in the absence of any other form of treatment for a concurrent malocclusion, then the first part of the treatment involves the surgical removal of the overlying mucosa, to expose the occlusal surface. It would be advantageous if the buccal aspect were also to be exposed, but this is not always possible due to the oblique line on the outer surface of the mandible that runs backward and upward from each mental tubercle. This oblique ridge reduces depth of the buccal sulcus, making it shallower as it proceeds past the molar region to become continuous with the anterior border of the ramus. Exposure of the buccal surface of an unerupted second molar therefore is difficult at best and frequently impossible. As the result, the only accessible surface may be the occlusal, for which a simple approach was described above in relation to the maxillary first molar, where a removable appliance was described and which may be employed here, with the same design and the same mechanical principles [37]. Alternative fixed appliance methods abound, but their design is too frequently restricted to just two or three teeth, which may seriously undermine the anchorage. Uprighting a second molar is notorious for causing the anchor teeth to move mesially or for the adjacent molar and premolars to be intruded and tipped buccally into a cross-bite relationship with the uppers. Every effort should be made to counter these tendencies. Ideally, teeth on both sides of the mandibular dental arch should be included in the anchorage unit [39] in order to minimize unwanted movement of other teeth in the arch, particularly to eliminate the possible occurrence of lower incisor crowding. A minimum suggested anchorage unit should include fixed bands on both first molars, joined by a soldered lingual arch, and orthodontic brackets on the premolars of the affected side. A useful alternative to the soldered lingual arch, particularly when there is bilateral impaction of the second molars, is to place a bonded multistrand wire retainer on the lingual side of the incisors and canines and extend it to the mesial occlusal pit of the first

premolar. In this way, the anchor unit comprises a sectional arch on each side engaging first molars and both premolars, together with the bonded retainer joining first premolar to first premolar. This brings the 12 teeth anterior to the second molars into the anchor unit without the need for anterior brackets. When the second molar is only mildly impacted and partially erupted beneath the distal bulbosity of the first molar, it is frequently possible to place a bonded tube or other attachment on its buccal surface and simply include it in the initial levelling arch that is used in the early stages of treatment. For the more severe cases, however, creative and problem-specific mechanisms will be needed to resolve the problem. The active element may be constructed in one of many ways: 1. A free-sliding sectional wire is slotted into the brackets and the molar tube on the affected side and is activated by an elastic module, with the distal end of the sectional wire fashioned into a small hook, which latches onto an eyelet attachment on the buccal or occlusal surface of the impacted tooth. This will tip the molar distally until the buccal surface rises sufficiently for a buccal tube to be placed and the remainder of the treatment completed with a buccal aligning archwire. 2. A similar method can be employed using a compressed coil spring (Figure 8.20). 3. A rectangular section arch can be used, containing an expanded open loop which is tied into the brackets after being compressed against the attachment on the molar. 4. A large and stiff open loop of rectangular wire is placed in the distal end of a buccal tube or wide Siamese bracket on the molar and is designed to widely encircle the impacted tooth, with a small helix at its extremity. By tying a stainless steel ligature between a bonded eyelet or button on the occlusal of this tooth and the small terminal loop, distal pressure is brought to bear on the impacted molar [39]. 5. A complete round wire loop with a distal helix may be slotted into buccal and lingual horizontal tubes on the molar band. Activation is made as for 4, by tying a steel ligature between the helix and an attachment on the tooth (Figure 8.21). With a more deeply sited tooth, one which may be seen on a radiograph to be well down in the junction between body and ramus, two essential problems exist. First, access in this area is difficult to obtain in order that bonding an attachment may be undertaken, but, with good teamwork on the part of the surgeon and the orthodontist, it can usually be done. The more difficult part of the problem involves the ability to conjure up a biomechanical method for applying appropriately directed traction, together with a solid anchor base that will resist unwanted movement.

(a)

(b)

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Fig. 8.20  (a, b) A coil spring is threaded onto a sectional archwire, which is slotted into the distal end of a buccal tube on the first molar band. The distal end of the wire carries a welded stop or cross-piece, which permits compression of the coil spring against a button or eyelet attachment on the second molar. A lingual arch and fully bracketed appliance is present for additional anchorage. (c, d) Panoramic views before and after treatment.

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(c) Fig. 8.21  (a) Button attachments bonded buccally and lingually to impacted second molar. (b) A wire loop carrying a distal helix is slotted into buccal and lingual tubes on the molar band. The wire loop is compressed by tying steel ligatures between the buttons and distal helix. (c) The final result.

Other Single Teeth  245  Applying forces from adjacent teeth only will intrude these teeth and generate a cant in the occlusal plane. Furthermore, the use of loop mechanics built into the archwire, as the means of applying uprighting, levelling or aligning forces, is extremely limited because of the shallowness of the buccal sulcus in the second molar area. However, the lingual sulcus is very much deeper and, with a little ingenuity, it may be exploited to accommodate a suitably designed uprighting, levelling and/or aligning spring.

Applying forces from teeth in the maxillary arch will increase what is probably already a considerable overeruption of the opposing molar, caused by the long-time absence of its antagonist. In the past, the only method was to use a high-pull headgear to maintain the vertical position of the molar while applying intermaxillary vertical traction to the impacted tooth (Figure 8.22). Today, this would be approached using a tempo­ rary micro-screw in the maxilla or a zygomatic plate. The

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(d) (e) Fig. 8.22  (a) A second permanent mandibular molar is impacted deeply with roots close to the lower border. There is indeterminate cystic or follicular tissue superiorly placed to it, which appears to have been the causative factor. (b) Following removal of the abnormal tissue, an attachment has been bonded to the tooth, with a minimal closed surgical procedure and without the removal of overlying bone or follicular tissue. The bony crypt is largely intact and the pigtail ligature is seen to be temporarily secured to the first molar. (c) An en bloc, high-pull, integral and removable headgear plate (not seen in the film) is the source of anchorage for the vertical elastics that are joined between the upper molar band and the sectional traction mechanism on the lower left side. Bone can be seen to have regenerated superior to the crown of the impacted tooth, similar to that of a normally erupting tooth. (d) The tooth has erupted and full multibracketed appliances are in place to treat the remaining malocclusion. (e) The case five years after completion of treatment, with bonded maxillary and mandibular 3-3 retainers still in place.

246  Orthodontic Treatment of Impacted Teeth advantages of a temporary anchorage device (TAD) include the fact that an orthodontic appliance in the affected jaw is, at least theoretically, unnecessary. However, this presupposes that the application of the vertical force will raise the tooth and align it in its ideal position (Figure 8.23). In practice, simple extrusion is rarely adequate because the tooth usually needs other force components to upright it. This means that an orthodontic appliance will be needed to complement the TAD in order to produce these aligning movements once the tooth is erupted and accessible for the placement of a suitable attachment. A second problem involves the patient’s ability to attach an intermaxillary elastic ring between the bone anchor and the hooked ligature wire that has been tied into the eyelet on the impacted second molar. The twisted ligature hook emanating from the impacted molar is not easily accessible for the patient to perform direct traction. It should be appreciated and accepted that not every patient is sufficiently dextrous or skilful at placing the elastic ring so far at the back of the mouth. It is usually considerably easier to teach the patient to apply vertical force from a convenient hook or bracket on one of the more mesial mandibular teeth to the TAD. This supports the anchorage, while active extrusion may be applied by the orthodontist direct from a suitably configured short rectangular sectional archwire to the pigtail hooks attached to the impacted molar. Treatment as part of a comprehensive orthodontic treatment plan For most cases, some form of overall malocclusion is present, for which treatment needs to be prescribed. The resolution of the impacted tooth should be integrated into the general treatment plan. If resolution of the overall malocclusion demands a reduction in the number of teeth, consideration should be given to the extraction of this impacted tooth, together with appropriate balancing and compensating extractions in the other quadrants of the mouth (Figure 8.24) [40–45]. Extraction of mandibular second molars is not a frequent extraction of choice, but under the circumstances of a very difficult impaction should be considered. This enables the dispersal of mild crowding to be effected with great facility in a distal direction, without the need for the extensive root uprighting movements that are seen with premolar extractions. However, the orthodontist will be counting on the favourable eruption of the third molars (which will be significantly earlier in these cases) and their spontaneous alignment. Should this not occur, a further period of treatment will need to be initiated, three or four years later in the young adult stage, aimed at uprighting the mesially tipped third molars from a position that may be reminiscent of the initial position of the extracted second molar! In this situation, the above procedures may be applied to

bring about third molar uprighting, in exactly the same way as with second molars. Perhaps the best way to visualize the potential influence of the extraction of different groups of teeth is on the panoramic radiograph. With a mesially tipped second molar in an extraction case, the loss of a first or second premolar and the mesial movement of the first molar may often free the tooth to erupt, but the tipping will remain and, in a few cases, may even become worse, with the tooth appearing to ‘fall flat on its face’. Uprighting will then need to be undertaken, using the existing multi-bracketed appliances. Where the mandibular arch, mesial to the first molars, is well aligned or slightly crowded, but there is a mild class 2 relationship or crowding of the maxillary dentition, all the upper and the posterior lower teeth will probably need distal movement, rather than extractions made. An extraoral headgear will be needed to take the entire maxillary dentition posteriorly and to provide the space for the alignment of its individual teeth. Class 3 intermaxillary elastics, supported by the headgear, may then be used against a full lower fixed appliance, whose purpose is to align the teeth and move the mandibular first molars distally. The force will be transferred through interproximal contacts to the second molar and, if this is tipped less than approximately 20° and has a relatively high contact with the distal of the first molar crown, above the CEJ area, the tooth will ultimately tip distally and upright, while the first molar will itself be tipped distally. Once the second molars have erupted and the distalizing force is discontinued, the first molar will spontaneously upright. Second molars that are tipped more than 20° and/or are located at or below the CEJ and the distal bulbosity of the first molar will not spontaneously upright in this way and will need to be treated more aggressively. This will necessitate surgical exposure and attachment bonding to the impacted tooth and the inclusion of this unit into a full mandibular fixed appliance. Initial levelling and aligning archwires extended to this tooth will usually suffice to bring it into alignment. In more extreme cases, the employment of a temporary implant should be considered, as detailed above.

Maxillary second molars In the posterior region of the maxilla crowding will be seen in the tuberosity area. Unerupted second and third molars will be seen to be ‘stacked’ almost vertically above the erupted first molar and above one another, rather than in a more horizontal, distally directed arrangement. Their root apices are mesial and their crown point distal, usually with a buccal component – clearly due to a basal shortness of the maxilla, with disproportionately large teeth. In this situation, the second molars will sometimes fail to erupt, which may delay the completion of orthodontic treatment. Provided there is no other obstacle most of these teeth will spontaneously erupt after the covering and

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Fig. 8.23  (a) A section of the panoramic view of a 19-year-old patient, showing an unerupted second molar with dentigerous cyst. A very late-developing third molar is present and the maxillary second molar is over-erupted. (b) The tooth is exposed to show the size of the cyst. The third molar was removed at the same visit. (c) Two attachments bonded since access is good and a large surface is available. (d) The exposure site is fully sutured closed with the two pigtail ligatures fashioned into hooks for elastic traction. (e) Post-surgical periapical radiograph. (f) The zygomatic plate is placed under local anaesthetic cover. (g) A palatal screw temporary anchorage device is placed. (h) An elastic chain is drawn between the palatal TAD to the zygomatic plate, across the occlusal surface of the over-erupted tooth and secured by a bonded button on the occlusal surface. An inter-maxillary elastic is placed by the patient between the zygomatic plate and the molar pigtail ligature hooks. (i) At the end of treatment, lasting eight months, the maxillary second molar is well intruded and the mandibular second molar has been erupted to the occlusal plane. (j) Periapical view of the mandibular second molar post-treatment. (k) Section of the post-treatment panoramic view to show maxillary and mandibular molars of affected side.

248  Orthodontic Treatment of Impacted Teeth

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(k) Fig. 8.23  (Continued )

Other Single Teeth  249 

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(c) Fig. 8.24  (a) Age 13.2 years all four second molars are in abnormal positions in a class 2, division 1 extraction case. Extraction of three second molars and right maxillary third molar performed. (b) Age 16.4 years follow-up radiograph at the end of orthodontic treatment, to assess the third molars. (c) Age 19.3 years the three-year post-treatment follow-up panoramic view shows the third molars in ideal alignment and fully juxtaposed with the first molars. Unfortunately, there are few reliable keys or guidelines by which this excellent result could have been predicted at the outset.

usually thickened mucosa is cut away. They will, however, often erupt buccal to the line of the arch into a buccal crossbite relationship with the lower second molar and will thus need to be aligned as a last stage in the overall orthodontic treatment. The occasional second molar may have a mesial tip with its mesial curvature locked in the distal concavity of the first molar, just beneath the surface. Following exposure, this may sometimes need the placement of a simple elastic separator ring for a few days to help, but these teeth usually come in well. There is one final condition that is seen on the panoramic radiograph that causes the maxillary second molar to become impacted. This is related to an anomaly in the development of the adjacent third molar. This tooth is characterized by having a banana-shaped crown, little or no root development and it is located inferiorly to the crown of the second molar, thereby acting as an obstruction to the latter’s eruption (Figure 8.25). In fact, the tooth is probably both inferior and palatal to the second molar, but nevertheless obstructing its path of eruption. Identifying this tooth at the time of exposure and removing it is disconcerting for the surgeon,

because of its unexpected position occlusal and lingual to the second molar. Nevertheless, following its extraction, the second molar will erupt very rapidly (Figure 8.25).

Mandibular third molars In the past, the ‘prophylactic’ removal of third molars was carried out almost blindly and, in many cases, in the belief that this would prevent secondary incisor crowding in the post-retention period [46–48]. Today, there are positive indications that an effort should be made to bring these teeth into the dental arch and make them useful functional dental units. This is particularly pertinent in the latter stages of the treatment of a premolar extraction case when excess space is closed by drawing the first and second molars mesially. This potentially opens up space at the distal end of the arch, which may sometimes be adequate to accommodate an erstwhile impacted third molar. In these instances, successful conservative treatment of the impaction, by orthodontic alignment, provides the maxillary third molar with an antagonist. This in turn allows both teeth to assume the same functional rating as any other tooth in the dentition.

250  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

Fig. 8.25  The ‘banana’ maxillary third molar. (a) In the panoramic view of a 13-year-old female, the left maxillary third molar is superimposed on the impacted second molar and is more occlusally located. The other second molars have erupted. (b, c) The extracted ‘banana’ molar from the occlusal and buccal aspects. (d) The second molar erupted autonomously four months after the extraction. This panoramic view was taken many months later, at the completion of the orthodontic treatment.

The decision to upright a mesially inclined and impacted third molar must be made taking into consideration its prospective final position in relation to the ascending ramus of the mandible and its thick soft tissue investment. Should the final position of the tooth be at the expense of a localized resorption of the anterior border of the ramus or in the exuberant and inflamed soft tissue covering it, then the effort will have been wasted. Given adequate space at the end of the arch, however, there are often good indications for this treatment. Treatment is very similar to that described for mandibular second molars above. Distally inclined and impacted third molars are much more of a problem, since control of root movement is poor at the end of the arch and extraction is often to be advised.

Impaction and crown resorption In teeth that have remained unerupted for many years, the outer enamel epithelium of the dental follicle surrounding the crown of the tooth may occasionally break down and direct contact between bone and enamel occurs. In time,

this may lead to resorption of the enamel, often with the laying down of bone in the resorption lacunae. Any tooth may be affected, although it tends to occur in much older individuals whose dentition is established, and the unerupted tooth may have meanwhile been replaced prosthetically. Rarely, it may occur in a young person, for whom there is a relatively greater importance to bringing the tooth into the dental arch. The first clue of the existence of this pathological process is seen radiographically, with difficulty in distinguishing the outline of the dental follicle. This usually signifies the presence of a replacement resorption process of the enamel, with bone substituting for the resorbed enamel. In its more advanced stages, the radiographic appearance of the tooth shows a loss of the sharp outline of the crown and, later still, a reduction in the radiopacity of the crown, associated with a steady decalcification of the enamel [49, 50] and its replacement with trabecular bone (Figure 8.26). In order to move this tooth orthodontically, the entire crown area must be dissected free of the bone and a pack inserted to prevent the healing bone from again coming into contact with the enamel surface. A preformed crown

Other Single Teeth  251 

Fig. 8.26  A periapical view of the maxillary incisor region of an elderly lady, to show two impacted canines in an advanced stage of replacement resorption. The follicle is still visible in a localized area of the distal aspect of the right canine while elsewhere it is absent. The general vague outline of the two teeth may be seen, but the texture of each has given way to bony trabeculation.

would be a better alternative, but access to the tooth is too compromised to allow its proper adaptation and cementation. At the same time, orthodontic force should be applied to the tooth and its activity maintained by frequent religation. Success is far from guaranteed, because it may be difficult to fully separate the crown from the tissues and there may be secondary deterioration of tissues surrounding the root, as the tooth will also have been impacted for so many years. This is a very different entity from invasive coronal resorption, which was described at the end of Chapter 7. The tooth that has undergone invasive coronal resorption appears to have a normal dental follicle, a normal periodontal ligament and, while the initiation of the resorption is through a fault in the enamel itself, the resorption mushrooms out in the dentine and only affects the enamel last. There is no substitution of the resorbed tooth substance with bone, but rather with soft and vascular resorptive tissue. Consequently, there is no problem with orthodontic alignment provided there is an adequate area of residual enamel or new restorative material on which to bond an attachment.

Infra-occlusion of permanent teeth There is considerable confusion in terminology in relation to teeth that do not erupt to reach the occlusal plane and different designations are often applied to the same condition. Some authorities use a specific term to describe a very

specific condition, while others will use the same term indicating a much more general connotation. There are also language differences which, when translated literally, alter their meaning and an author’s geographical location may determine the particular word used in a journal report. Thus, clinicians and researchers from the Netherlands and Denmark refer to the condition in which there is arrested eruption occurring before the tooth penetrates the oral mucosa, as ‘primary retention’ [51, 52]. Elsewhere, the same condition will be classified under ‘impacted’ or, specifically in the French- and Italian-speaking world, as ‘included’. ‘Secondary retention’ in these same countries will mean cessation of eruption of a tooth after emergence without a physical barrier or ectopic position of the tooth, due to ankylosis [53, 54] which has been termed submergence or infra-occlusion elsewhere. The only recognizable similarity between the two forms of retention is that they both largely affect molars. These researchers restrict their definition of ‘impaction’ to mean a cessation of the eruption of a tooth caused by a clinically or radiographically detectable physiological barrier in the eruption path, or due to an abnormal position of the unerupted tooth. Primary retention is more frequently seen than secondary retention and there is an equal frequency of occurrence between the sexes. Primary retention occurs more often in the maxilla than in the mandible, while the opposite is seen in secondary retention. Primary retention may be seen in dentitions that have normal development of the second molar, as well as in dentitions with abnormal eruption patterns in the second molar region (late development and second molar agenesis), with or without generalized malocclusion. Secondary retention can occur in dentitions with normal development of the second molar independent of the presence or absence of generalized malocclusion. Furthermore, primary retention is an acquired condition, judging by phenotypic differences between the primary and secondary retention, in that variations of normal eruption of the second molar are seen in primary retention [52]. Over the past two decades or so, the Danish research group has come to implicate a defective nerve supply of the tooth as possibly instrumental in causing primary and second retention. Innervation of the dental follicle appears to be an important factor for the continued development of the teeth [55] and different groups of teeth have different sources of innervation, with one source covering a specific field. It is pointed out that neural pathways can spread viral or bacterial infections, particularly Herpes zoster and the mumps virus, but also in other conditions. Children suffer many undiagnosed acute infections in their younger years and neural spread would seem to be a possible cause of a compromised nerve supply, with consequent effects on the teeth [56]. Unilateral occurrence of the primary or secondary retention phenomena suggests infection as the cause, while bilateral occurrence suggests a genetic aetiology, either directly

252  Orthodontic Treatment of Impacted Teeth on the eruption mechanism or indirectly by affecting the nerve supply. The term ‘primary failure of eruption’ (PFE) was coined in 1981 by Proffit and Vig [57] and suggests a disturbance of the eruption mechanism that caused the complete or partial failure of a non-ankylosed tooth to erupt, although the molecular basis for this failure was unknown (Figure 8.27). This phenomenon is characterized by the following: 1. The posterior teeth are more frequently affected, that is, the first and second molars are more frequently affected than premolars and canines. 2. If a tooth in a further anterior position presents an eruption disturbance, the posterior teeth are usually affected as well. 3. The affected teeth resorb the alveolar bone above the crown, but erupt only partially or fail to erupt. 4. Both deciduous and permanent teeth can be affected. 5. The condition is usually asymmetrical. 6. Primarily non-ankylosed teeth tend to become ankylosed as soon as orthodontic forces are applied. Figure 8.28 shows panoramic radiographs of three children in one family, together with those of the father and the paternal grandmother, to show the differing familial expression of the phenomenon for each of these affected persons. Research on the molecular basis for PFE has recently placed the aetiological blame for PFE on mutations in the parathyroid hormone receptor 1(PTH1R) gene, which will provide the key to distinguish PFE from isolated ankylosis and secondary retention [58–62]. Differentiating the aetiology is of importance because it gives the clinician the ability to choose appropriate treatment. Teeth suffering from secondary retention, ankylosis and PFE will not be amenable to orthodontic treatment, but in PFE only the adjacent under-erupted teeth will also not respond to orthodontic traction, whereas the teeth adjacent to an isolated under-erupted tooth will. Never­ theless, in the clinical context at the time of writing, the time has yet to come when the diagnosis will be routinely determined by an appropriate genetic test. With continued vertical growth of the adjacent teeth and alveolar bone, ankylosed teeth become relatively lower and lower in the alveolus, until the gingival tissue grows over the tooth and they may even sometimes become covered by bone. Given that these teeth cannot be orthodontically moved, their ‘absolute’ anchorage potential may be exploited to orthodontically alter the position of neighbouring teeth in much the same way as any other ankylosed tooth, or an osseo-integrated implant may be used. Having no effect on the infra-occluded teeth, orthodontic extrusive forces will tend to intrude the adjacent teeth towards the level of the infra-occluded teeth. Nevertheless, it is not easy to give up on a tooth, particularly a single first permanent molar, in otherwise ideal circumstances [63]. In these situations and under local

anaesthetic, an attempt may be made to forcibly erupt an infra-occluded tooth following surgical luxation. Adequate space must be made for it and the tooth is held in extraction forceps and a rocking force applied aimed at fracturing the ankylotic junction and achieving a considerable degree of mobility of the tooth (Figure 8.29). This mobility will be achieved easily only when the area of ankylosis is small. In the presence of a wider area of ankylosis, the application of force is much more likely to cause root fracture. Accordingly, a good quality periapical radiograph should be carefully studied for signs and extent of any abnormality, ahead of time, since in the vast majority of cases of ankylosis the lesion and its location are radiographically undetectable. Healing is rapid and generally quite painless, but the ankylosis will soon become re-established if delay is incurred before traction is applied. Therefore, a force level must be maintained, not permitted to lessen and renewed on a regular (ideally weekly) basis. This means that the timing for this treatment must not span a period when the patient or the practitioner will be on vacation for any length of time. Should it happen that the patient is not seen for a few weeks and the force value drops, then re-ankylosis will occur and the tooth will resist further movement. In this event, a second surgical subluxation will be required to remobilize the tooth. Attempts at orthodontic correction are, therefore, frequently disappointing. Nevertheless, and despite the advice of Proffit and Vig, the parent and the orthodontist may not be prepared to accept the ‘no treatment’ verdict for a single affected tooth in a young patient. If the parents understand the poor prognosis, treatment may be attempted employing the partial surgical luxation technique referred to above, provided that attendance for frequent activation is assured. Beyond the treatment of single accessible teeth, attempts to resolve the impaction of multiple teeth whose roots have undergone ankylosis will generally fail (Figure 8.30). If strictly dental anchorage is used and the anchor teeth are in the same jaw as the infra-occluded tooth, the reactive force will likely lead to their intrusion. If intermaxillary forces are used, then the anchor teeth in the opposing jaw may become over-erupted and a canting of the occlusal plane may well occur. Skeletal anchorage, using a temporary screw implant or bone plate, should always be considered in these cases in order to avoid deleterious effects on the remainder of the dentition. This type of movement is more a microcosm of distraction osteogenesis than orthodontic movement per se and as such requires heavier and continuous forces to be applied. In many of these cases, the use of an orthodontic implant as the platform from which forces are applied, particularly a mini-plate secured with screws to the zygomatic process of the maxilla, or titanium mini-screws, may be very advantageous, because this source of anchorage will have no illeffects on the dentition as a whole. Accordingly, there is a

Other Single Teeth  253 

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(b)

(c) Fig. 8.27  (a) A normal occlusion of the posterior teeth is present on the right side. (b) A severe lateral open bite has developed on the left side due to primary failure of eruption. (c) The panoramic radiograph shows very marked infra-occlusion of the left mandibular first molar and, to a lesser extent, also of the left maxillary second premolar and first molar.

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Fig. 8.28  The family of the patient in Figure 8.28 including (a) grandmother, (b) father, and (c, d) two siblings showing varying expression of primary failure of eruption.

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Fig. 8.29  (a) An occlusal view of the mandibular dentition to show the severely infra-occluded left first molar, with tipping of the adjacent teeth. (b) Panoramic view of the initially diagnosed condition. (c) A clinical occlusal view of the achieved space opening. (d) Panoramic view of the achieved space opening. (e) Periapical view of the infra-occluded molar after bonding of two eyelets to the available occlusal surface. (f) Eight weeks after partial surgical luxation the tooth has erupted sufficiently and a regular bracket is bonded to the now available buccal surface. (g, h) Post-treatment panoramic and periapical views after extrusion, alignment and mesial root uprighting. (i, j) Clinical views of the treated tooth at two months post-treatment. (k–m) The occlusion at two months post-treatment.

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(m) Fig. 8.29  (Continued )

256  Orthodontic Treatment of Impacted Teeth

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(c) Fig.8.30  (a–c) Panoramic view, and lateral and postero-anterior cephalograms of an extreme case of primary failure of eruption.

case to be made for the use of implant anchorage in most cases where ankylotic teeth are treated in this way. On the basis of the above argument, it is logical to expect that, once successful treatment has been completed in the younger patient and the infra-occluded tooth is brought to the occlusal level, a renewed ankylosis will occur and the treated tooth will steadily and progressively infra-occlude again. Anecdotally, in several of the cases treated by the author, this has not happened, encouraging the belief that perhaps re-ankylosis does not always result and the tooth maintains its occlusal height over the long term. Given this favourable outcome, it should become possible to subsequently include orthodontic movement of this tooth as part of an overall orthodontic treatment plan for a given patient.

The trend in orthodontics today is to attempt to incorporate all malrelations of the jaws, occlusal interferences, individual tooth malalignments and space problems in one all-encompassing episode of treatment. By doing so, treatment is streamlined in terms of appliance efficiency, quality of results and overall treatment duration. Controlled studies, from the Universities of South Carolina [64], Washington [65], Michigan [66], Florida [67] and Oxford [68], have indicated that there is little long-term advantage to be gained from treating a class 2 case in a two-phase treatment. Provided the optimum timing for the treatment of the impacted tooth coincides with the establishment of the full permanent dentition, therefore, it makes sense to integrate

Other Single Teeth  257 

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(e)

(f)

Fig. 8.31  (a) This 4-year-old child was seen in the Department of Oral Surgery with a cystic lesion around the right deciduous second molar, whose development appears to have become arrested at an early stage. The adjacent deciduous first molar is infra-occluded. There appears to be a similar disturbance of the follicle of the first permanent molar. Surgical removal of the cystic lesion was undertaken and the pathological report yielded a diagnosis of ameloblastic fibroodontoma. No teeth were extracted at that time. (b) Two years later healing had occurred and there were no signs of recurrence. The first deciduous molar had erupted normally and both the second deciduous molar and first permanent molar showed the beginnings of root development. However, they showed no signs of eruptive movement, in contrast to the other molars. The second premolar had failed to develop. (c, d) Right lateral and occlusal clinical views of the edentulous ridge immediately before surgery at 8 years of age. (e) Two eyelets are bonded to the buccal surface of the molar. (f) A closed eruption procedure leaves only the two pigtail ligatures exposed. (g) The zygomatic implant is screwed into place. A pigtail ligature will be placed here too. (h) Vertically extrusive latex elastics are placed by the parent and subsequently the child between the hooked pigtail ligatures. (i) The panoramic view at this stage. Note how the developing root and the lack of eruption have caused an alteration in the shape of the lower border of the mandible. (j, k) The tooth responded slowly to the force, showing early signs of erupting into the mouth within about half a year. (l, m) Full eruption was achieved in a further nine months. Treatment was stopped at this point. The eyelets were detached and, under local anaesthetic, the zygomatic implant was removed. (n) Initiation of orthodontic treatment with fixed appliances for the first time. (o-q) The final result of the orthodontic treatment. The first mandibular right premolar is located in the place of the second premolar. The patient will be retained until an implant may be placed. (r) Post-treatment panoramic radiograph showing normal root development of the previously affected teeth and adequate space preparation for a future implant to replace the missing premolar.

(g)

(h)

(i)

(j)

(k)

(l)

(m) Fig. 8.31  (Continued )

Other Single Teeth  259 

(o) (n)

(p)

(r) Fig. 8.31  (Continued )

(q)

260  Orthodontic Treatment of Impacted Teeth it into the overall treatment plan. While this is fine for the maxillary canine, which is often among the last permanent teeth to make up the full complement of erupted permanent teeth (apart from the third molars), this would be totally inappropriate for a maxillary central incisor or for the permanent molars, which make up a small but significant number of affected cases. Thus, due to developments in the area of implantology, one of the more valuable approaches that now presents itself is the ability to divorce the treatment of an impacted tooth from the treatment of a malocclusion. Using only an implant in the opposite jaw and an elastic band, it is now possible to resolve an impaction and bring about full eruption of a tooth without the use of an orthodontic appliance and without causing ill-effects either to the adjacent teeth or to the teeth in the opposing jaw. Being no longer dependent on the presence of other teeth to influence the decision, the practitioner may choose the optimum timing for treatment of the impaction, based solely and objectively on considerations related to the impacted tooth itself, without reference to the other teeth, which may then be treated at a different time (Figure 8.31). Iatrogenics Aside from the naturally occurring ankylosis, there may be reason to suspect the possibility of an iatrogenic variety. It was pointed out in Chapter 3 that it is not uncommon to find an oral surgeon widely exposing the crown of the impacted tooth down to the CEJ and beyond, with consequent instrumentation of the cementum of the root surface of the tooth and a drying out of the PDL. We have also discussed the accidental spillage of liquid etchant over the root surface during the bonding of an attachment. Surgical trauma, desiccation and chemical burns are potent causes for both ankylosis and invasive cervical root resorption and this would never be discovered until many months later, when attempts at moving the tooth have failed. Aggressive surgical practices or careless bonding procedures have no place in the treatment of impacted teeth, since these will undermine the highly sensitive eruptive mechanism of the tooth from which it may not recover. The best way to reduce the chances of morbidity is for the orthodontist to be present and an active participant in the critical surgical episode.

References   1.  Kokich VG. Surgical and orthodontic management of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2004; 126: 278–283.   2.  Nordenram A, Stromberg C. Positional variations of the impacted upper canine: a clinical and radiologic study. Oral Surg Oral Med Oral Pathol 1966; 22: 711–714.   3.  Fournier A, Turcotte JY, Bernard C. Orthodontic considerations in the treatment of maxillary impacted canines. Am J Orthod 1982; 81: 236–239.   4.  Oliver RG, Mannion JE, Robinson JM. Morphology of the maxillary lateral incisor in cases of unilateral impaction of the maxillary canine. Br J Orthod 1989; 16: 9–16.

  5.  Jacoby H. The etiology of maxillary canine impactions. Am J Orthod 1983; 84: 125–132.   6.  Zilberman Y, Cohen B, Becker A. Familial trends in palatal canines, anomalous lateral incisors, and related phenomena. Eur J Orthod 1990; 12: 135–139.   7.  Peck S, Peck L, Kataja M. Prevalence of tooth agenesis and pegshaped maxillary lateral incisor associated with palatally displaced canine (PDC) anomaly. Am J Orthod Dentofacial Orthop 1996; 110: 441–443.   8.  Becker A. Etiology of maxillary canine impactions. Am J Orthod 1984; 86: 437–438.   9.  Chaushu S, Sharabi S, Becker A. Tooth size in dentitions with buccal canine ectopia. Eur J Orthod 2003; 25: 485–491. 10.  Becker A, Chaushu S. Dental age in maxillary canine ectopia. Am J Orthod Dentofacial Orthop 2000; 117: 657–662. 11.  Chaushu S, Sharabi S, Becker A. Dental morphologic characteristics of normal versus delayed developing dentitions with palatally displaced canines. Am J Orthod Dentofacial Orthop 2002; 121: 339–346. 12.  Chaushu S, Bongart M, Aksoy A, Ben Bassat Y, Becker A buccal ectopia of maxillary canines in the absence of crowding. Am J Orthod Dentofacial Orthop, 2009; 136: 218–223. 13.  Chaushu S, Chaushu G, Becker A. The use of panoramic radiographs to localize maxillary palatal canines. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999; 88: 511–516. 14.  Chaushu S, Chaushu G, Becker A. Reliability of a method for the localization of displaced maxillary canines using a single panoramic radiograph. Clin Orthod Res 1999; 2: 194–199. 15.  Vanarsdall RL, Corn H. Soft tissue management of labially positioned unerupted teeth. Am J Orthod 1977; 72: 53–64. 16.  Vanarsdall RJ. Periodontal/orthodontic interrelationships. In Graber TM, Vanarsdall RL, eds. Orthodontics. Current Principles and Techniques, 4th edn. St Louis, MO: Mosby, 2000: 801–838. 17.  Kohavi D, Zilberman Y, Becker A. Periodontal status following the alignment of buccally ectopic maxillary canine teeth. Am J Orthod 1984; 85: 78–82. 18.  Kuftinec MM, Shapira Y, Nahlieli O. A case report. Bilateral transmigration of impacted mandibular canines. J Am Dent Assoc 1995; 126: 1022–1024. 19.  Shapira Y. Bilateral transposition of mandibular canines and lateral incisors: orthodontic management of a case. Br J Orthod 1978; 5: 207–209. 20.  Joshi MR. Transmigrant mandibular canines: a record of 28 cases and a retrospective review of the literature. Angle Orthod 2001; 71: 12–22. 21.  Mupparapu M. Patterns of intra-osseous transmigration and ectopic eruption of mandibular canines: review of literature and report of nine additional cases. Dentomaxillofac Radiol 2002; 31: 355–360. 22.  Peck S. On the phenomenon of intraosseous migration of nonerupting teeth. Am J Orthod Dentofacial Orthop 1998; 113: 515–517. 23.  Nodine, A.M. Aberrant teeth, their history, causes and treatment. Dent Items of Interest 1943. 65: 440–451. 24.  Shapira Y. Transposition of canines. J Am Dent Assoc.1980; 100: 710–712. 25.  Shapira Y, Kuftinec MM. Orthodontic management of mandibular canine–incisor transposition. Am J Orthod 1983; 83: 271–276. 26.  Brezniak N, ben-Yehuda A, Shapira Y. Unusual mandibular canine transposition: a case report. Am J Orthod Dentofacial Orthop 1993; 104: 91–94. 27.  Shapira Y, Kuftinec MM. Intraosseous transmigration of mandibular canines – review of the literature and treatment options. Compend Contin Educ Dent 1995; 16: 1014, 1018–1020, 1022–1024. 28.  Shalish M, Peck S, Wasserstein A, Peck L. Malposition of unerupted mandibular second premolar associated with agenesis of its antimere. Am J Orthod Dentofacial Orthop. 2001; 121: 53–55. 29.  Shalish M, Chaushu S, Wasserstein A. Malposition of unerupted mandibular second premolar in children with palatally displaced canines. Angle Orthod. 2009; 79: 796-799. 30.  Kurol J. Infra-occlusion of primary molars. An epidemiological, familial, longitudinal, clinical and histological study. Swed Dent J Suppl 1984; 21: 1–67. 31.  Kurol J, Thilander B. Infra-occlusion of primary molars and the effect on occlusal development, a longitudinal study. Eur J Orthod 1984; 6: 277–293.

Other Single Teeth  261  32.  Becker A, Shochat S. Submergence of a deciduous tooth, its ramifications on the dentition and treatment of the resulting malocclusion. Am J Orthod 1982; 81: 240–244. 33.  Becker A, Karnei-R’em RM. The effects of infra-occlusion: part 1 – tilting of the adjacent teeth and space loss. Am J Orthod 1992; 102: 257–264. 34.  Becker A, Karnei-R’em RM. The effects of infra-occlusion: part 2 – the type of movement of the adjacent teeth and their vertical development. Am J Orthod 1992; 102: 302–309. 35.  Becker A, Karnei-R’em RM, Steigman S. The effects of infra-occlusion: part 3 – dental arch length and the midline. Am J Orthod 1992; 201: 427–433. 36.  Proffit WR. Contemporary Orthodontics. St Louis, MO: Mosby Year Book, 1992. 37.  Becker A. The correction of mesially angulated semi-impacted molar teeth by simple orthodontic means. Isr J Dent Med 1977; 2: 17–22. 38.  Shapira Y, Finkelstein T, Shpack N, Lai YH, Kuftinec MM, Vard­ imon A. Mandibular second molar impaction – Part 1: Genetic traits and characteristics. Am J Orthod Dentofacial Orthop 2011; 140: 32–37. 39.  Majourau A, Norton LA. Uprighting impacted second molars with segmented springs. Am J Orthod Dentofacial Orthop 1995; 107: 235–238. 40.  Wilson HE. The extraction of second permanent molars as a therapeutic measure. Trans Eur Orthod Soc 1966; 42: 141–145. 41.  Richardson ME, Richardson A. Lower third molar development subsequent to second molar extraction. Am J Orthod Dentofacial Orthop 1993; 104: 566–574. 42.  Cavanaugh JJ. Third molar changes following second molar extraction. Angle Orthod 1985; 55: 70–76. 43.  Gaumond G. Second molar germectomy and third molar eruption. Angle Orthod 1985; 55: 788. 44.  Gooris CGM, Artun J, Joondeph DR. Eruption of mandibular third molars after second molar extractions: a radiographic study. Am J Orthod Dentofacial Orthop 1990; 98: 161–167. 45.  Staggers JA. A comparison of results of second molar and first premolar extraction treatment. Am J Orthod Dentofacial Orthop 1990; 98: 430–436. 46.  Richardson ME. The role of the third molar as the cause of late lower arch crowding: a review. Am J Orthod Dentofacial Orthop 1989; 95: 79–83. 47.  Southard TE. Third molars and incisor crowding: when removal is unwarranted. J Am Dent Assoc 1992; 123: 75–79. 48.  Zachrisson BU. Mandibular third molars and late lower arch crowding – the evidence base. World J Orthod 2005; 6: 180–186. 49.  Blackwood HJJ. Resorption of enamel and dentine in the unerupted tooth. Oral Surg Oral Med Oral Pathol 1958; 11: 79–85. 50.  Azaz B, Shteyer A. Resorption of the crown in impacted maxillary canine. A clinical, radiographic and histologic study. Int J Oral Surg 1978; 7: 167–171. 51.  Raghoebar GM, Boering G, Vissink A, et al. Eruption disturbances of permanent molars: a review. J Oral Pathol Med 1991; 20: 159–166.

52.  Kjaer I. Phenotypic classification of 90 dentitions with arrested eruption of first permanent mandibular or maxillary molars. Seminars in Orthodontics, 201; 16: 172–179. 53.  Raghoebar GM, Boering G, Jansen HWB, et al. Secondary retention of permanent molars: a histologic study. J Oral Pathol Med 1989; 18: 427–431. 54.  Raghoebar GM, Boering G Vissink A, Stegenga B. Eruption disturbances of permanent molars: a review. Journal of Oral Pathology and Medicine, 1991; 20: 159–166. 55.  Christensen LR, Janas MS, Mollgaard K, Kjaer I. An immunocytochemical study of the innervation of developing human fetal teeth using protein gene product 9.5 (PGP9.5). Archives of Oral Biology 1993; 38: 1113–1120. 56.  Becktor KB, Bangstrup MI, Rolling S, Kjaer I. Unilateral primary or secondary retention of permanent teeth and dental malformations. Eur. J Orthod 2002; 24: 205–214. 57.  Proffit WR, Vig KWL. Primary failure of eruption: a possible cause of posterior open bite. Am J Orthod 1981; 80: 173–190. 58.  Frazier-Bowers SA, Koehler KE, Ackerman JL, et al. Primary failure of eruption: further characterization of a rare eruption disorder. Am J Orthod Dentofacial Orthop 2007; 131: 578.e1–11. 59.  Decker E, Stellzig-Eisenhauer A, Fiebig BS, et al. PTHR1 loss-offunction mutations in familial, nonsyndromic primary failure of tooth eruption. Am J Hum Genet 2008; 83: 781–786. 60.  Frazier-Bowers SA, Simmons D, Wright JT, Proffit WR, Ackerman JL. Primary failure of eruption and PTH1R: The importance of a genetic diagnosis for orthodontic treatment planning. Am J Orthod Dentofacial Orthop 2010; 127: 160.e1–7. 61.  Stellzig-Eisenhauer A, Decker E, Meyer-Marcotty P et al. Primary failure of eruption (PFE) – clinical and molecular genetics analysis. J Orofac Orthop 2010; 71: 6–16. 62.  Frazier-Bowers SA, Chaitanya PP, Mahaney MC. The aetiology of eruption disorders – further evidence of a ‘genetic paradigm’. Seminars in Orthodontics 2010; 16: 180–185. 63.  Chaushu S, Becker A, Chaushu G. Orthosurgical treatment with lingual orthodontics of an infra-occluded maxillary first molar in an adult. Am J Orthod Dentofacial Orthop 2004; 125: 379–387. 64.  Tulloch JFS, Proffit WR, Phillips C. Outcomes in a 2-phase randomized clinical trial of early class II treatment. Am J Orthod Dentofacial Orthop 2004; 125: 657–667. 65.  King GJ, McGorray SP, Wheeler TT, Dolce C, Taylor M. Comparison of peer assessment ratings (PAR) from 1-phase and 2-phase treatment protocols for class II malocclusions. Am J Orthod Dentofacial Orthop 2003; 123: 489–496. 66.  Livieratos FA, Johnston LE Jr. A comparison of one-stage and twostage nonextraction alternatives in matched class II samples. Am J Orthod Dentofacial Orthop 1995; 108: 118–131. 67.  Dolce C, Schader RE, McGorray SP, Wheeler TT. Centrographic analysis of 1-phase versus 2-phase treatment for class II malocclusion. Am J Orthod Dentofacial Orthop 2005; 128: 195–200. 68.  McKnight MM, Daniels CP, Johnston LE Jr. A retrospective study of two-stage treatment outcomes assessed with two modified PAR indices. Angle Orthod 1998; 68: 521–524.

9 Impacted Teeth in the Adult Patient (In Collaboration with Stella Chaushu)

Neglect and disguise

263

Management

265

The need for temporary prostheses during the treatment

267

Supplementary clinical concerns

270

Tooth transposition and temporary prosthetic replacement

273

The unerupted third molar as a potential bridge abutment or antagonist for an unopposed tooth

273

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

Impacted Teeth in the Adult Patient  263 

Neglect and disguise A small but significant number of untreated impacted teeth will eventually find some way of erupting into the mouth without treatment, although this may be many years after their normal eruption time and then often into an ectopic eruption site. This is particularly true of maxillary canines [1] and, at least to a degree, in contradiction to the popular view that eruption potential is lost when the root apex closes [2]. Nevertheless, a good proportion will remain unerupted and asymptomatic for many years. Prostho­ dontists are aware of the occasional patient complaining of the eruption of a tooth under a denture often many years after the patient had become otherwise edentulous. For the most part, during the childhood of the particular adult patient concerned, advice was probably sought and rejected, with the reasons for this being very varied. The patient may have been an orthodontically unmanageable child at the appropriate age; perhaps the dentist or orthodontist was insufficiently convincing in the task of informing the parent of the consequences of non-treatment; or the parents’ level of dental awareness was inadequate, the idea that surgery would be needed was possibly abhorrent to the parents or simply the cost and duration of the proposed treatment were unacceptable. Just occasionally, a surgical exposure procedure would have been carried out at the appropriate time, but failed to elicit eruption and was not then followed up. Some impacted teeth, particularly maxillary canines, may simply have never been diagnosed. One further possibility that is not unfa­ miliar is that a dentist succumbed to the pleadings of the parent to ‘do something temporary to make it look good’, until they would be ready for the definitive treatment – a time that never arrived! The impacted maxillary central incisor It may be difficult for the orthodontist to imagine the situation where a patient has reached adulthood still with an

(a)

impacted central incisor. This will have been obvious from around the age of 7 years, but the patient only sought treatment in his/her twenties or even later. This type of neglect is indeed unusual and its prevalence seems likely to vary from country to country, in inverse proportion to the level of dental awareness in the population. A country that offers its citizens some form of national dental insurance may be expected to have a lower prevalence among its adults, since one would hope that treatment would have been carried out at the appropriate time, given the relative freedom from financial constraints in a welfare state. Cost, however, is not the only factor, probably not even the dominant one. Whatever the reason, the adult patient will usually present with the incisor anomaly unsuccessfully disguised in one of three ways: 1. A retained deciduous tooth may have been enlarged with the addition of composite material, although this will probably only have improved its length. Any increase in its width will be limited by the reduced mesio-distal space available to the tooth, the result of the marked mesial tipping of the adjacent lateral incisor and the central incisor of the opposite side. 2. This reduced space may have been maintained with a ‘flipper’ (spoon) partial denture, carrying a single and poorly matched small tooth (Figure 9.1a, b). 3. The lateral incisor may have been enlarged, with the use of composite material, in an attempt to simulate the shape of the impacted central incisor (Figure 9.2a). There are serious drawbacks with each of these treatment alternatives, which focus principally on the very poor appearance of the results. The absence or reduction in size of a central incisor is always obvious, as is any significant shift in a maxillary dental midline, even to the casual observer. The tipping of the two teeth adjacent to the impacted incisor is too severe for this to escape notice and the angle of the lateral incisor is too acute for its long axis

(b)

Fig. 9.1  Impacted right maxillary central incisor (a) replaced by poorly matched artificial tooth on ‘flipper’ (spoon) denture (b).

264  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 9.2  (a) Impacted right maxillary central incisor. The right lateral incisor crown has been enlarged by a composite build-up. (b) Initial stages of alignment and space-opening. The composite build-up of the maxillary right lateral incisor is still in place. (c) Space has been reopened, the composite build-up of the lateral incisor has been removed and the artificial central incisor is in place, attached to the soldered palatal arch closing the anterior open bite. (d) The soldered arch has been deflected slightly vertically downwards to elongate the artificial tooth. (e) Placement of the archwire shows the degree of vertical displacement. The artificial tooth is now fully engaged in the archwire. (f) The extrusive force of the palatal archwire closes off the open bite. (g) The periapical view shows the impacted tooth to be dilacerated. The palatal arch is clearly seen, with the forward-pointing loop used to carry the radiolucent artificial tooth. An orthodontic bracket is also attached to this radiologically invisible tooth. (h) Pre-treatment tangential radiograph. (i) Bonding of an eyelet to the anatomically palatal aspect of the incisor crown. (j) The elastic chain is gently raised and ensnared in the pigtail to provide immediate and controlled vertical traction. (k) Post-surgical periapical view to show the bonded eyelet and pigtail ligature. (l) The tangential view post-surgery showing the length of the unseen part of the ligature and the relative heights of the tooth, the ligature extremity, and the occlusal plane. (m) The impacted tooth has erupted five months later: note the reduction of the cervical portion of the artificial tooth to allow for further progress. Traction was made to a newly placed labial attachment at this juncture. (n) Periapical view of the dilacerate incisor at the completion of treatment. (o) The orthodontic result: note the gingival appearance of the treated and untreated maxillary central incisors.

Impacted Teeth in the Adult Patient  265 

(h)

(g)

(i)

(j)

Fig. 9.2  (Continued )

to be visually ‘realigned’ by composite additions or by reshaping. The narrowness of the neck of the tooth makes an aesthetically convincing reconstruction, as a central incisor, difficult to achieve.

Management It is quite clear that in these circumstances the first and most important prerequisite to any form of treatment for the missing tooth is to provide the maxillary dental arch

with an ideal shape in each of the three planes of space. In practical terms, this means: Levelling and aligning the entire dental arch. All ectopi• cally placed teeth will need to be brought into an ideal archform, teeth will need to be aligned in a single, uniform occlusal plane and all rotations dealt with. Reopening a space of suitable mesio-distal width in order to accommodate the impacted tooth in the arch. Correcting the palatal inclination of the canine and tipping the lateral incisor of the same side and the central

•

266  Orthodontic Treatment of Impacted Teeth

(k) (l)

(m)

(n)

(o) Fig. 9.2  (Continued )

Impacted Teeth in the Adult Patient  267  and lateral incisor of the opposite side will usually provide adequate space, although distal movement, extraction or interproximal enamel stripping may need to be considered. Correcting the dental midline, to be continuous with the lower and with the midline of the face. This is normally achieved as a result of the reopening of space, but it may require the use of coil springs or anterior, oblique, intermaxillary elastics as part of a more comprehensive orthodontic appliance programme. The use of anterior intermaxillary elastics in the adult is often a difficult request to put before the patient for obvious social reasons. The judicious placement of temporary anchorage devices to permit forces to be applied unilaterally within the same arch is clearly to be preferred. Closing down an anterior open bite and bringing the teeth into occlusion. This may sometimes be achieved by properly aligning the molar tubes and by altering bracket height on the anterior teeth, thereby bringing about the desired extrusion of the teeth − and unpopular anterior vertical elastics are of material help in this situation. Often, however, an increased height of the lower third of the face and excessive vertical exposure of the maxillary anterior teeth and gingivae (gummy smile) may dictate the intrusion of the posterior teeth rather than extruding the anteriors. This may be achieved using zygomatic plates screwed into the inferior aspect of the zygomatic process of the maxilla, opposite the molar teeth. In this scenario, it should be understood that a force applied from a zygomatic plate, high in the sulcus, to the buccal tube on the molar will produce a rolling-out of the molar. It is therefore mandatory to use a transpalatal bar, preferably soldered from molar to molar. This bar should be prepared in such a manner as to be positioned a couple of millimetres away from the palatal mucosa to permit molar intrusion without palatal impingement.

•

•

Once these aims have been achieved, the patient is ready for that stage in treatment when all resources will need to be concentrated on the impacted tooth. The entire dental arch must be consolidated into a compound and united anchorage unit, to which the unerupted tooth will be drawn. In Chapters 6 and 7, it was noted that teeth that have been impacted for many years sometimes undergo pathological change which prevents their eruption [3], even when all other factors are favourable. It is by no means always possible to diagnose pathological change from a radiograph, unless there is a loss of the follicular sac and actual enamel resorption has become evident over wide areas of the surface of the unerupted tooth. It is therefore true to say that, whenever an adult patient presents for the treatment of an impacted tooth, a calculated risk is taken in offering this kind of treatment to resolve the impaction. In the most adverse of circumstances, the central incisor tooth will have to be extracted and, perhaps, replaced with

an implant-borne restoration. In that event, the preparation of the dental arch described above will have provided optimal clinical conditions to accept the implant or other form of artificial restoration of the space. An ideal pontic width is present, the roots of the adjacent teeth have been uprighted to make sufficient inter-radicular space for implant placement, all other teeth are aligned and the occlusion is good. However, the surgical removal of a grossly displaced impacted tooth, high above its normal position, will leave a considerable and unsightly bony defect. This will be difficult to conceal in the gingival area around a fixed prosthesis and will not lend itself to the placing of an implant without suitable and prior osseous ridge reconstruction [4–7]. The patient must be brought into the decision-making process from the outset and should be informed of the potential advantages of each of the stages of treatment. This is best done using a set of plaster models of the patient’s teeth, together with a wax duplicate set-up, to show a scheme of the proposed treatment result. Prognosis for the success of the pre-surgical stages of the treatment is excellent, but for the alignment of the impacted tooth it is not so certain. Offering the treatment plan to the patient is, therefore, probably best accomplished if it is based on explaining the benefits of the limited objectives, i.e. aligning the teeth for the purposes of achieving improved conditions for the construction of a conventional prosthodontic or implant-borne replacement. The added bonus, which will be derived from success in the resolution of the impaction, may then be properly brought into perspective to provide the desirable added incentive. By whatever means the value of the treatment is explained, care should be taken to fully inform the patient that the possibility of failure to bring the impacted tooth into the arch is real, but that contingency plans are available in this disappointing eventuality.

The need for temporary prostheses during the treatment The impacted central incisor For the adult patient, planned orthodontic space opening for an unerupted anterior tooth is a daunting prospect. All central and lateral incisors and maxillary canines require some form of immediate temporary prosthetic replacement until such time as the permanent tooth comes into its place. With some patients, particularly those more concerned with their appearance or those who have a broad smile or a wide dental display which is evident in facial expression and social intercourse, there may be a need to artificially replace even premolar teeth. Perhaps the most popular solution for an impacted incisor is to trim an artificial acrylic tooth to a suitable shape and size, bond a bracket to it and ligate it into the archwire of the appliance. In the early stages, the archwire

268  Orthodontic Treatment of Impacted Teeth is probably nickel−titanium and of round cross-section, which means that the new artificial pontic is very unstable and will rotate around or slide along the archwire. Placing a V-bend in the wire or welding a small piece of wire in the vertical position will prevent the rotation but complicate use of the archwire. It will also need to be copied into each of the subsequent archwires until a rectangular crosssection wire is used. An artificial acrylic tooth may be bonded to the mesial surface of the contralateral central or ipsilateral lateral incisor, although this assumes that the archwire is absolutely passive when ligated into the bracket on these teeth. A minor rotatory movement will cause a major lateral or medial swing of the pontic, while an uprighting component will markedly intrude or extrude it at its opposite end. Alternatively, the artificial restoration may take the form of a removable plate carrying a single tooth − a ‘flipper’ (spoon) denture. The average adult patient may have considerable difficulty becoming accustomed to it, even if its retention is adequate initially. Of greater concern, however, is the fact that the adjacent teeth and many other teeth need to be moved during the orthodontic treatment, which will rapidly make this artificial denture ill-fitting. Furthermore, the close adaptation of the acrylic base to the contour of the other teeth in the jaw may actually interfere with the planned orthodontic movement. For this type of artificial replacement to be successful, Adams clasps may have to be used on the second molars; alternatively, a modified circumferential clasp may hook over the buccal tubes of the first molars. These teeth are often excluded from the planned dental movements and may sometimes be helpful in retaining such a plate, although the distance between the clasps and an incisor pontic may be the cause of an unacceptable degree of instability. Clearly, more satisfactory alternative methods of artificial replacement are essential to the successful pursuit of treatment for the adult patient, and these must provide an answer to the several shortcomings of the ‘flipper’ denture. Indeed, given a little thought in their design, and rather than their playing the role of the villain of the piece, assistance in the application of force to the impacted tooth may be derived from the method of artificial replacement, which may actually contribute to the smooth running of the active orthodontic appliance. The active removable plate If a removable plate is to be worn to hold the artificial tooth in place, it makes good sense to augment that plate with active elements that will also produce tooth movement. Looked at in a different way, this means designing a simple removable orthodontic appliance carrying springs of one sort or another, which are aimed at realigning the teeth to reopen the anterior space and, at the same time, to fill that space with an artificial tooth.

This method has some important advantages. The active plate is straightforward and easy to use, requiring very limited expertise in adjustment of the forces applied and in their direction. Because the plate is removable and generally adjusted at the chair side out of the mouth, the size and shape of the artificial tooth may be easily altered in size or speedily replaced as space opening occurs, to maintain appearance. However, the active removable appliance is unable to produce more than tipping movements of the adjacent teeth. Methods have been described where removable appliances have been used to produce the extrusive movements needed to resolve the impaction of teeth [8, 9]. Their effectiveness in this capacity is limited and they cannot be expected to perform the labio-lingual or mesio-distal root movements or rotatory movements that are often needed to fully align these aberrant teeth. In cases where removable appliances are used to resolve the initial impaction and to erupt the tooth, therefore, they must be followed by a fixed appliance to bring about the successful completion of a second phase of treatment, which is aimed at the fine functional and aesthetic positioning of the teeth in all three planes of space. The soldered palatal arch In the adult patient, the scope of orthodontic correction that is planned tends to be more localized and less comprehensive, particularly when a single and grossly displaced tooth is present. The first maxillary molar teeth are most commonly used as anchor teeth for the fixed appliance, and their orthodontic movement is not usually required. This being so, the buccal aspects of these teeth and buccal/labial aspects of the teeth more anteriorly placed will be used to carry the orthodontic attachments, archwires and auxiliaries. This leaves the palatal side of the teeth and the palate area free, and available to serve the interests of the patient’s appearance. A soldered palatal arch, based on the molar bands, can provide the orthodontic appliance with an excellent anch­ orage base, at the same time as acting as the vehicle for a satisfactory prosthetic replacement. Several approaches are available. They depend on the adaptation of wellfitting preformed orthodontic bands to the molar teeth and their accurate transference to a plaster working model of the jaw. On the working model, a palatal arch is fabricated and soldered on the palatal side of the molar bands. A small wire extension may then be soldered or bent into the anterior portion of the palatal arch, extending towards the space in the arch and terminating immediately palatal to the position of the missing tooth, with a configuration that will mechanically retain an artificial acrylic tooth. The exact location of the artificial tooth should be decided in accord-

Impacted Teeth in the Adult Patient  269  ance with the projected treatment goals of the case and not necessarily in line with the adjacent natural teeth. Thus, if an overjet is to be closed or a cross-bite treated, the siting of the artificial tooth should be made according to the intended final, post-treatment position of the adjacent teeth. An occluded plaster cast of the opposite jaw is therefore necessary to assist in its accurate placement. This is the simplest approach of this type and offers the patient a good artificial replacement, which is well tolerated (Figures 9.2a, b). It also allows the adjacent teeth to be aligned without hindrance, while actually enhancing the anchorage value of the molars during retraction of a procumbent labial segment. The anchor molars cannot be rotated or tipped easily when using horizontal, intramaxillary elastics, due to the stabilizing effect of the rigid soldered palatal arch. A significant and valuable refinement of this approach involves bonding a conventional bracket to the artificial tooth, as with the other teeth. This makes the artificial tooth aesthetically compromised to a similar degree as the other teeth and, therefore, less recognizable as other than a part of the natural dentition. Since this tooth is rigidly attached to the molar teeth and at a fixed distance from them, this method has much more to offer. Its integration into the appliance system makes alignment and levelling more accurate and more rapid. Additionally, the need for elastic traction to reduce the overjet will be eliminated, since the use of the initial fine gauge levelling and aligning wires in the early weeks of treatment will perform this without any further modification. The distance and relationship between molars and the artificial incisor is fixed to the ideal length and position by the palatal arch. Thus, a progression of ideal wire archforms will align all other teeth within that arch. Essentially, by linking the archwire to the fixed pontic in its normal overjet and overbite location, the first stage of mechano-therapy, which generally deals with initial levelling and alignment only, now comes to include automatic overjet and overbite reduction. The overall length of the heavy palatal arch provides it with a degree of elasticity despite its heavy gauge. Thus, while carrying a temporary prosthetic replacement, it may be used to widen or constrict the dental arch. In the present context, however, it has one other possible function which is less obvious, but most helpful. The palatal arch has the potential to provide the vertical component of force that is needed to close an anterior open bite and, subsequently, the vertical traction needed to resolve the incisor impaction (Figures 9.2 d–g). The impacted maxillary canine Aside from third molars, and in common with the younger patient, the tooth most frequently found to be impacted in the adult is the maxillary canine. The principles of

diagnosis, treatment planning and appliance therapy in the adult are no different from those in the child, alth­ ough certain demands are made by the adult patient, which may make treatment methods less routine and more individualized. Palatally impacted canines are frequently associated with only minor malocclusions and, as we have already pointed out in Chapter 6, in dentitions in which the dental age is often very late. Therefore, we may occasionally see a case of impaction which has eluded diagnosis until a much later age, and the circumstance that led to the discovery was the exfoliation of the deciduous canine or, sometimes, a routine examination by the general dentist, which revealed the buried tooth. Additionally, the increase in demand for orthodontic treatment among adults in recent years may change the attitude of some patients who had strongly opposed orthodontic treatment in adolescence and who may be more inclined to reconsider it later. The question therefore arises as to whether we can expect that treating impacted teeth in adults will produce the same results, in the same period of time and with a similar degree of confidence in achieving a successful outcome. Little has been published in the orthodontic and surgical journals to enlighten us regarding these extremely important points, since the number of cases is very small and most ortho­ dontists have limited experience with them. Nevertheless, two articles have appeared which have reported conflicting findings. According to one study, the duration of such treatment in the over-25 years is likely to be significantly longer than for the child patient [10]. A more recent investigation found the opposite, namely that treatment was longer in younger patients with impacted canines than in an older group [11]. However, the patients who took part in the latter study were all under the age of 20 years, and among these, the younger individuals in the group had, on average, more serious impactions than did the older ones. Thus, given the fact that the ‘adult’ patients were little more than adolescents and barely definable as adults, both chronologically and dentally, as well as the small difference in age and a difference in the objective complexity of the treatment of the younger vs. the older patients, it seems that little may be concluded from this study regarding the effect of age. Aside from these two papers and until quite recently, the available articles on adult patients have been anecdotal case presentations, which can give no indication regarding these basic questions. Accordingly, a study was initiated [12] in which 19 adults, whose ages ranged between 20 and 47 years (mean age 28.8 years) and who had been treated for 23 impacted maxillary canines, took part. They were compared with a control group of younger patients, ranging from 12 to 16 years of age (mean age 13.7 years). The control group had been objectively selected on a matched case-by-case basis to

270  Orthodontic Treatment of Impacted Teeth ensure a similar degree of complexity of the impaction and with similar positions of the canine location in three planes of space, using the classification described in Chapter 6 above. Successful treatment was possible in approximately 70% of the adult canines and in 100% of the younger controls. While the duration of the overall treatment of the general dental malocclusion did not differ significantly between the two groups, the part of the treatment that was strictly concerned with the impacted canines took considerably longer in the adult group, both for the simpler cases and for the more complicated cases, when compared with their matched younger counterparts. All the failed cases occurred in the over-30-year-old patients. The conclusions that were drawn were that the prognosis for successful reduction and alignment of impacted canines among adults was lower in general and that it worsens with increasing age. Additionally, it was noted that a successful outcome of the part of the treatment concerned with the resolution of the canine impaction and its alignment in the adult should be expected to take considerably longer – in contrast to the remainder of the orthodontic treatment for the overall malocclusion. To camouflage the absence in the arch of an impacted canine, an artificial acrylic tooth may be bonded to the mesial surface of the first premolar (see Figure 10.11), although this assumes that the archwire is passively ligated into the premolar bracket. A minor rotatory movement will cause a major lateral or medial swing of the pontic, while an uprighting component will markedly intrude it into the gingival tissues or extrude it into premature occlusion at its opposite end. In a case with impacted incisor teeth, the presence of a palatal arch does not encroach on the area where surgical exposure will be performed and where postsurgical swelling is likely to occur, provided the anterior portion of the palatal arch is not brought too far forward. A cut-back design is usually most appropriate. For the surgical episode involved in the exposure of a palatally displaced maxillary canine, a wide area of palatal mucosa may need to be reflected back, and this, together with the possible sequel of even a minimal degree of postsurgical oedema, effectively disqualifies the use of a rigid palatal arc. A transpalatal bar, such as a Goshgarian or a simple ‘acrossthe-palate’ soldered arch, is usually sufficiently posteriorly located from the surgical site to be used in these circumstances. It cannot be used for prosthetic replacement and its only functions are to enhance the anchorage and to maintain arch width. However, in combination with a buccal arm, it may be very useful and have definite indications. In the illustrated case (Figure 9.3), the adapted molar bands were transferred to a plaster working model and a trans-palatal arch was soldered to the palatal side of the bands. To the buccal side of the bands and gingival to the buccal tubes a heavy buccal arm was soldered, which

extended vertically upwards into the sulcus. The arm was then fabricated to follow the depth of the sulcus anteriorly until it reached the canine area, where it again dipped inferiorly to terminate in a loop in the canine site. An artificial acrylic tooth was cured into this retention loop, in the place of the missing permanent canine. Immediately after extraction of the natural deciduous tooth, the unit, which comprised two molar bands, a palatal arch and a buccal extension arm, was cemented into place, followed by appropriate orthodontic attachments on the first premolar teeth. After placement of a sectional arch on each side, the impacted canine was exposed surgically in the normal way. Traction was then applied behind the façade of the buccally retained artificial tooth. As with the placement of a bracket on the artificial central incisor, described above, it is advantageous to design the integration of these prosthetic expedients into the orthodontic appliance system in such a way that they may materially contribute to the efficiency of the appliance. Thus, after cementation of the bands carrying these additions, the buccal arm may be displaced further buccally, so that its passive position stands a few millimetres buccal to its original location. If it is then tied directly to the impacted canine, using a steel ligature, which will draw the displaced buccal arm and artificial tooth back into alignment with the adjacent teeth. The energy stored by this long, elastic and now deflected buccal arm will thus provide the traction needed to draw the impacted tooth towards its place in the arch.

Supplementary clinical concerns The basic premise for the use of these palatal and buccal arches for both impacted incisors and canines has been that the first molar tooth does not require to be ortho­ dontically moved. Needless to say, there are cases in which movement of the first molars is an essential part of the orthodontic strategy of the treatment of a particular adult. These may include cases where there is a pronounced rotation or a palatal or buccal displacement of this tooth, but they may also include the premolar extraction cases where closure of excess space from the distal will be needed. In these cases, several options are still available to allow the smooth pursuit of orthodontic treatment under aesthetically acceptable conditions. In the first place, a single buccally displaced or palatally displaced molar tooth, which is planned to be used as an anchor unit, may be tipped into its place using a removable appliance. This appliance will need to carry some form of buccal or palatal spring, which will be used to move the tooth in the appropriate direction, suitable clasps to retain the appliance firmly in position and, possibly, carry an artificial tooth to replace the impacted incisor tooth in the interim. Alternatively, an existing

Impacted Teeth in the Adult Patient  271 

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Fig. 9.3  (a–c) A 47-year-old female has a maxillary left canine that is impacted adjacent to a peg-shaped lateral incisor. This case was treated by the author in the early 1970s. The erupted right canine is in the place of the congenitally absent lateral incisor. (d) The patient wears a removable partial plate to fill the canine sites on each side. (e–g) The molar bands are interconnected by a soldered ‘across-the-palatal’ heavy arch (not seen). A high buccal arm is soldered on each molar band, carrying an artificial canine tooth, to replace the discarded partial plate. (h) A small hook is cured into the left artificial canine, and the buccal arm is deflected buccally and inferiorly at the time of surgical exposure of the impacted canine. (i) Ligating the impacted tooth to the artificial tooth applies extrusive and buccal traction. (j–l) The left canine has been brought into its place and a fixed partial prosthesis fills the gap on the right side.

‘flipper’ denture may be augmented to incorporate the same clasp and spring elements. When more extensive movement of the anchor teeth is required, this is usually enacted in a preparatory orthodontic treatment phase, which is aimed at producing good alignment by uprighting, rotating and torqueing the teeth, while limiting the appliance work and movement of the anterior teeth to levelling and aligning. During this procedure, it is important to enable the patient who has been

wearing a removable artificial prosthesis to continue to do so until such time as the alignment stage is complete. Similarly, an over-retained deciduous incisor tooth should be allowed to remain until the planned temporary prosthetic rehabilitation becomes practical. With the satisfactory completion of the preparatory orthodontic treatment phase and the teeth having been brought into good alignment, the precise reopening of the space for the missing tooth is undertaken.

272  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(i)

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(l)

Fig. 9.3  (Continued )

At this point, the palatal arch is constructed on a plaster model, into which the molar bands have been accurately seated and the artificial tooth is sited, as described above. The patient’s ‘flipper’ denture is now discarded, or the overretained deciduous tooth is extracted, and the palatal arch carrying the artificial incisor tooth is inserted by recementing the molar bands to their former place. When moving teeth mesio-distally along an archwire with a multi-bracketed fixed appliance, the establishment of interproximal contacts between the teeth enables a high degree of control of individual tooth position. Once this is

achieved, uprighting and torqueing movements may be carried out, with care being taken to see that the spaces do not reopen. The desired treatment result includes closed contacts. In the situation where a tooth is unerupted and space needs to be made for it, the orthodontist should err on the side of reopening excess space and then maintaining it until the tooth reaches its place. However, to do so, the space needs to be maintained during the many further months of treatment, when the adjacent teeth will be altering their relationships to one another. While attention is diverted to

Impacted Teeth in the Adult Patient  273  the details of treatment in these other areas, changes may inadvertently alter the space. The original coil spring which may have opened the space requires to be deactivated, since it will otherwise continue to increase the dimensions of the space. However, the placement of active root-uprighting springs will tend to close the space by compressing the spring. The size of the artificial incisor tooth and its mesiodistal siting may be very useful in holding the achieved space and in ideally placing the adjacent teeth, regardless of their locations and without the need for the coil spring or the ligation of groups of teeth. The natural teeth are swiftly brought into interproximal contact with the artificial tooth and with each other, and this status is then simple to maintain.

Tooth transposition and temporary prosthetic replacement Rarely, one or more of the impacted teeth are also transposed. For the most part, it is preferable to align the teeth in their transposed positions rather than try to re-transpose them to their ideal positions, for reasons discussed in Chapter 6. Nevertheless, there are situations in which this may be the preferred line of treatment. Given the high frequency of missing lateral incisors in cases of transposition of maxillary canine/first premolar transposition, treatment of the transposition may have to consider the artificial replacement of the missing teeth during the appliance therapy. The use of a palatal arch to augment the anchorage value of the molar teeth and to provide the vehicle for the artificial replacement teeth is an effective way to deal with the problem (Figure 9.4). By tying in a labial archwire from molar tube to molar tube, passing through a bracket on each of the artificial lateral incisors, these four strategic attachments on the perimeter of the arch are defined in relation to one another, since the incisor pontics are also rigidly fixed to the molar bands on the lingual side. The long span of labial archwire that intervenes between molar tube and incisor bracket is therefore well supported in terms of anchorage and may be used to slide the more buccal of the transposed teeth (usually the canine) in the mesio-distal plane. At the same time, the more lingual of the transposed teeth must be moved further lingually to allow its neighbour to pass by. Finally, it must be moved in the opposite mesio-distal direction and back in the line of the arch. To achieve this, the more lingual tooth may be ligated to several different and strategically planned loops and cross-pieces that will have been prepared on the palatal arch, ahead of time, using elastic thread. Once again, positive use is made of the palatal arch as an integral part of the orthodontic appliance system, together with its function as a buttress for anchorage. It does not serve merely as a means of supporting an artificial tooth.

The unerupted third molar as a potential bridge abutment or antagonist for an unopposed tooth In the previous chapter, we discussed the disimpaction of molar teeth, which were prevented from erupting partially or fully by their relationship with an immediate mesial neighbour. It is pertinent in the context of the present chapter to discuss a related scenario which commonly presents. Following the extraction of posterior teeth in the adult patient, the establishment of a ‘free-end edentulous saddle’ makes oral rehabilitation problematic. This may sometimes find a potentially convenient solution in the discovery of an unerupted third molar. However, the absence of standing posterior teeth creates mechano-therapeutic difficulties in providing the vertical traction which is aimed at enhancing the eruptive potential of an unerupted third molar. Elastic traction of the tooth to the opposing jaw is a useful method, and has been referred to above [9], but the use of removable appliances in the adult patient is unreliable. Adults have far greater difficulty becoming accustomed to the bulk of the removable plate and its interference with masticatory and articular function. The use of a fixed mandibular appliance offers a much more satisfactory and dimensionally modest alternative, which interferes neither with eating nor with speech. Furthermore, if the mandibular appliance is to be used only as a source of anchorage, brackets and archwires may be dispensed with, making it very inconspicuous indeed. The second molar in the opposite arch is unopposed. It is the tooth which faces the potential eruption site and the proposed final position of the unerupted tooth. Using this tooth as the sole source of elastic traction will cause its highly undesirable over-eruption [13]. The premolars in the same quadrant may be in occlusion further forward and these teeth may be included in the anchor unit if they are rigidly linked together, to prevent or limit their reactive intrusion. Using a plaster model of the patient’s opposing jaw, a length of 0.024 in (0.6 mm) stainless steel wire is adapted to the general form of the buccal surfaces of the teeth, from second molar to the second or, preferably, first premolar (Figure 9.5). The wire extends very slightly mesial to the most anterior tooth and a few millimetres distal to the second molar, where it is bent into the form of a hook. Those parts of the wire immediately overlying the tooth surfaces should also include small retention loops and/or welded mesh pads. Returning to the patient, the buccal surfaces of the teeth are etched and the wire bonded to them using a composite material. Transbond™ or equivalent lingual retainer bond­ ing agent is probably the easiest to use, is adequate for the task and is easy to remove at the conclusion of the treatment.

274  Orthodontic Treatment of Impacted Teeth

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Fig. 9.4  (a–c) A 27-year-old female with congenitally absent maxillary lateral incisors and maxillary canine/first premolar bilateral transposition treated by the author in the 1970s, before the advent of bonded brackets. The deciduous canines and right lateral incisor are still present. (d) Occlusal view of maxillary arch. (e–g) Intra-oral views after extraction of deciduous teeth. (h–j) Treatment progress seen from the right side. (k, l) Use of a palatal arch as support for lateral incisor pontics and also to move premolars through varying use of elastic thread. (m) Occlusal view of complete maxillary dentition, with wire splint from first premolar, including lateral incisor pontics. (n–p) Intra-oral views of the completed orthodontic result. The patient was referred for permanent prosthodontic treatment of the lateral incisor problem.

Impacted Teeth in the Adult Patient  275 

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Fig. 9.4  (Continued )

276  Orthodontic Treatment of Impacted Teeth

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(p)

Fig. 9.4  (Continued )

A small, custom-made hook or button is prepared and bonded to the unerupted tooth following its exposure. At the same visit as these procedures are performed, the patient is taught to place a small latex elastic (3/8 in medium or 5/16 in light gauge) on the hook and to draw it round the wire extension distal to the opposing second molar, and then forward to engage the small protrusion of the wire mesial to the first premolar. This forms an L-shaped configuration to the elastic, which has a dual purpose: the overall length provides a light force of excellent range while, at the same time, making the manipulation of the elastic very easy for the patient. The vertical traction that is applied to the tooth may be altered to include a horizontal component by altering the position of the distal end of the bonded wire, thereby also directing the tooth mesially, distally, lingually or buccally. An easier alternative in this case would be to place a mini-screw in bone on the buccal side of the alveolus just distal to the roots of the second molar tooth and to use that as the source of anchorage for the vertical

elastic. However, while this particular treatment was carried out several years before temporary implant devices were in routine use, both approaches to treatment are entirely valid and today provide both operator and patient with a choice. Implant anchorage When an adult patient requires oral rehabilitation following the loss of one or more teeth, the prosthetist/prosthodontist will often favour artificial replacement with an osseointegrated implant. If that same patient also has an impacted tooth, then the implant may be exploited to assist in its resolution. A successful implant can be used to provide ‘absolute’ anchorage, since it forms an osseo-integrated union with the bone and, like an ankylosed tooth, will not respond to orthodontic forces [14] (Figure 9.6). Alternatively, a temporary orthodontic implant, in the form of a mini-screw which can be used in a variety of places in either jaw (see Figure 10.16), or a zygomatic plate screwed into the inferior surface of the zygomatic arch of

Impacted Teeth in the Adult Patient  277 

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Fig. 9.5  (a) A 54-year-old male patient, showing unopposed mandibular right second molar. (b) Close-up views of buccally displaced and partially erupted third molar. (c) A 0.024 in round wire has been adapted to buccal surfaces of the premolar and molar teeth on the mandibular model. Note the retention loops and welded mesh pads. The distal extremity is in the shape of a hook, which has been covered with solder for patient comfort. (d) The L-shaped elastic configuration for ease of placement and wide range of action. (e) Following eruption, a partially bonded appliance is used to upright the third molar. Additional anchorage is derived from a soldered palatal arch from first molar to first molar. (f) The final stage of treatment.

278  Orthodontic Treatment of Impacted Teeth

(a)

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Fig. 9.6  (a, b) An osseo-integrated implant has been placed in the maxillary left second premolar site. A partially erupted and distally tipped third molar shows only its mesial surface and mesial occlusal cusps. (c) An elastomeric chain module applies force to the implant post via the bonded eyelet on the molar. (d) Vertical force is applied to a mandibular bonded buccal bar to achieve occlusal contact. (e) Fully occluding third molar. Note the use of three button attachments to provide vertical force with buccal or lingual vectors, as needed. The mesial button is to prevent the elastic from impinging on the gingiva. (f, g) Pre- and post-treatment radiographs. (h) Lateral view of the prosthodontic reconstruction.

Impacted Teeth in the Adult Patient  279 

(g)

(h)

Fig. 9.6  (Continued )

Fig. 9.7  A plate orthodontic implant has been screwed onto the surface of the inferior aspect of the zygomatic arch, with its looped extension passing through the oral mucosa and lying adjacent to the first or second molar. The patient places vertical elastics from this plate to the hooked end of the pigtail ligature which is tied to an attachment bonded to an impacted third molar (not seen). No other orthodontic appliance is presently being used to elevate this tooth.

the maxilla (Figures 9.7 and 9.9), may be used as a platform from which elastic traction is applied to individual teeth, with or without the need for the use of complex orthodontic appliances. An implant may also be placed in the midline of the palatal vault – a midplant. However, unlike the above-mentioned devices, this is unsuitable for direct traction to an impacted tooth, because of its non-strategic position vis-à-vis the tooth. It may nevertheless be used to reinforce the anchorage of an orthodontic appliance that has been customized to open space within the dental arch and to apply the nee­ded directional extrusive force to the impacted tooth (Figure 9.8).

At the completion of their specific tasks, these nonintegrated devices are removed very simply, provided they have not been in place for more than a half year or so. Those that are present for much longer may become progressively osseo-integrated in many instances and will be more difficult to remove. The use of both temporary and osseointegrated implants in this manner offers considerable opportunity for the development of novel ways of applying forces in general, particularly for partially dentate adults, for replacing extra-oral anchorage in non-growing patients [15] (Figure 9.9) and in lingual orthodontics, as will be seen in the next chapter.

280  Orthodontic Treatment of Impacted Teeth

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(g) Fig. 9.8  Anchorage derived from a mid-plant. (a, b) Buccal and occlusal intra-oral views of an infra-occluded maxillary first molar. (c) A regular fixed appliance is used with a coil spring to open the space between second premolar and second molar. (d, e) The space is opened and the mid-plant is placed, with soldered arms connecting it to the second premolar and second molar. Buccal and lingual attachments are bonded to the infra-occluded molar prior to the surgical procedure to loosen the tooth from its ankylotic attachment. Elastic ties apply extrusive force from the buccal eyelet to the vertically offset archwire. (f) The buccal surface has become more exposed as the tooth erupts, and a new horizontal tube is substituted for the eyelet. (g) The molar tooth has reached the occlusal level and intercuspates well with the opposing teeth.

Impacted Teeth in the Adult Patient  281 

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Fig. 9.9  The use of a zygomatic plate implant for distal movement of the entire buccal segment on one side only in a patient with a missing central incisor, following trauma. (a, b) Intra-oral views of the posterior occlusion on each side. (c) A compressed open coil spring is placed between first premolar and first molar, with the intention of moving first and second molars distally. The canine is tied back with an elastic power chain to the inferior extremity of the plate implant, to provide anchorage against the reactive force of the coil spring. (d) With the molars in class 1 intercuspation, the implant is used to tie elastic elements to retract the premolars and canine and to support the anchorage for the uprighting of the canine. (e, f) The completed result. (g) A section of the panoramic radiograph shows the plate implant.

282  Orthodontic Treatment of Impacted Teeth

References   1.  Thilander B, Jacobson SO. Local factors in impaction of maxillary canines. Acta Odont Scand 1968; 26: 145–168.   2.  Kokich VG, Mathews DP. Surgical and orthodontic management of impacted teeth. Dent Clin North Am 1993; 37: 181–204.   3.  Azaz B, Shteyer A. Resorption of the crown in impacted maxillary canine. A clinical, radiographic and histologic study. Int J Oral Surg 1978; 7: 167–171.   4.  Sailer HF. Two new methods combining osteotomies and endosseous titanium screw implants for the narrow maxillary ridge and the atrophic lateral mandible. Abstract presented at the Third International Congress on Preprosthetic Surgery, ‘The edentulous jaw’. Arnhem, the Netherlands, 1989: 62–63.   5.  Richardson D, Cawood JI. Anterior maxillary osteoplasty to broaden the narrow maxillary ridge. Int J OralMaxillofac Surg 1991; 20: 342–348.   6.  Simion M, Baldoni M, Zaffe D. Jawbone enlargement using immed­ iate implant placement associated with a split-crest technique and guided tissue regeneration. Int J Periodont Restor Dent 1992; 12: 463–473.   7.  Lustmann J, Lewinstein I. Interpositional bone grafting technique to widen narrow maxillary ridge. Int J Oral Maxillofac Implants 1995; 10: 568–577.

  8.  Fournier A, Turcotte J, Bernard C. Orthodontic considerations in the treatment of maxillary impacted canines. Am J Orthod 1982; 81: 236–239.   9.  Orton HS, Garvey MT, Pearson MH. Extrusion of the ectopic maxillary canine using a lower removable appliance. Am J Orthod Dentofacial Orthop 1995; 107: 349–359. 10.  Harzer W, Seifert D, Mahdi Y. The orthodontic classification of impacted canines with special reference to the age at treatment, the angulation and dynamic occlusion. Fortsch Kieferorthop 1994; 55: 47–53. 11.  Stewart JA, Heo G, Glover KE et al. Factors that relate to treatment duration for patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2001; 119: 216–225. 12.  Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003; 124: 509–514. 13.  Peck L, Peck S, Attia Y. Maxillary canine-first premolar transposition, associated dental anomalies and genetic basis. Angle Orthod 1993; 63: 99–109. 14.  Stern N, Becker A. Forced eruption: biological and clinical considerations. J Oral Rehabil 1980; 7: 395–402. 15.  Roberts WE, Smith RK, Zilberman Y, Mozsary PG, Smith RS. Osseous adaptation to continuous loading of rigid endosseous implants. Am J Orthod 1984; 86: 95–111.

10 Lingual Appliances, Implants and Impacted Teeth (Stella Chaushu and Gabriel Chaushu) The context of impacted canines vis-à-vis the lingual appliance

284

Differences in treatment approach engendered by the use of lingual appliances

284

Canine traction, eruption and alignment

285

Finishing procedures

286

Anchorage considerations

286

Integrating implants with lingual appliances

287

Case report

290

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

284  Orthodontic Treatment of Impacted Teeth

The context of impacted canines vis-à-vis the lingual appliance There are four major areas of concern in the ortho-surgical approach for the resolution of impacted teeth in adults, namely, the need to wear orthodontic appliances, prognosis, duration of treatment and anchorage. While the objective treatment difficulties are considerable, the adult patient may reject the whole plan of treatment because of the need to wear unaesthetic fixed orthodontic appliances for long periods. Among the ‘invisible’ appliances, the lingual orthodontic appliance is, at present, the only viable alternative to the traditional labial appliance which may be efficiently used to treat such complex conditions in adults. In a Medline search of the English-language orthodontic literature, only one article was found that describes the use of lingual appliances in the treatment of impacted teeth in adults [1]. This is rather surprising in the light of the growing demand for facial and dental aesthetics by adult patients, and in view of the fact that lingual orthodontics has become established as a well-recognized and widely accepted discipline. It is nevertheless understandable because, in the treatment of the cases under discussion, an orthodontic appliance may need to execute as many as five different movements on the impacted tooth, involving vertical extrusion, tipping to the line of the arch, rotation, mesio-distal root uprighting and buccal root-torque (see Chapter 6). Achieving these with a lingual appliance is still considered to be more difficult by most clinicians, who would undoubtedly prefer to treat cases requiring these complex manipulations with the more familiar labial appliances. In Chapter 9 it was pointed out that the prognosis for the success of the orthodontic resolution of the impacted canine in an adult is lower than in the young patient and that it worsens with advancing age. Furthermore, when such treatment is undertaken, its successful completion should be expected to take considerably longer than in younger patients [2]. For this reason, it is important to find creative ways to shorten the whole treatment, especially that part of treatment related to the canine impaction.

Differences in treatment approach engendered by the use of lingual appliances Changes and adaptations need to be made to the protocols for the treatment of impacted teeth, which have been suggested in earlier chapters of this book in line with the demands of each of the various stages of treatment. Several problematic areas arise, and it is necessary to show how these may be overcome using the lingual appliance. Following accurate positional diagnosis and a carefully planned strategy for erupting the impacted tooth, the lingual appliance will be bonded into place. Its aims will initially be directed at levelling, alignment and space-

Fig. 10.1  Space opening with an open coil spring.

Fig. 10.2  Space maintenance with a closed coil spring. Note open surgical exposure of the canine.

opening for the impacted tooth. These goals may be realized in the present context with the help of copper–nickel– titanium (CuNiTi) archwires initially, followed by a heavier steel archwire, an open coil spring and sliding mechanics (Figure 10.1). The space achieved must then be maintained until the impacted tooth has been initially aligned in the arch. With labial appliances, the use of a gently curved stainless steel tube threaded on the wire has been recommended to act as the space maintainer (see Chapter 6). However, this is not feasible in the lingual appliances, because of the need for a premolar offset. Therefore, in lingual treatment, space is usually maintained with a closed coiled spring (Figure 10.2) or with a pair of offsets distal to the lateral incisor and mesial to the first premolar, or by ‘figure-of-eight’ ligation of the teeth on either side of the space. At this stage, the patient is referred for surgical exposure of the impacted tooth. In Chapter 3, the advantages of a closed eruption technique have been discussed and it was shown that it provides

Lingual Appliances, Implants and Impacted Teeth  285  a better periodontal and aesthetic result when compared to the open eruption technique [3, 4]. The closed eruption technique also results in less postoperative discomfort for exposures in the palate [5]. However, a closed eruption procedure for a palatal canine generally requires an intra-sulcular incision along the cervical margins on the palatal side of all the teeth, with the flap raised from first molar forward. In the presence of a lingual appliance, this procedure is clearly difficult to perform, since the brackets and their hook attachments are adjacent to and extend deeper than the cervical margins, obstructing access. Removing the archwire is mandatory prior to surgery, which complicates its postsurgical replacement and the application of traction. The alternative approaches are: to perform closed surgery before appliance placement, • leaving the ligature unattached and free in the palate until traction can be initiated, several weeks or months later; to perform an open surgical exposure, accepting the disadvantages of its postsurgical discomfort and posttreatment outcome.

to circumnavigate the canine on its medial side and close to the palatal midline raphe, while labial/buccal traction will need to be made to a small buccal attachment on a posterior tooth (Figure 10.4). In group 2 canine cases, the intimate relation between the canine crown and lateral incisor root will block the canine movement if direct traction is applied, while in group 3 canines the height of the tooth may contraindicate the use of direct buccal traction. Therefore, the canine must be erupted first in a vertically downward and somewhat palatal movement in order to free it from its entanglement with the incisor roots, as has been amply demonstrated in earlier chapters. An appropriate canine auxiliary should be prepared to be placed at the time of surgery as in a labial approach, such as a suitably modified full auxiliary arch [6]. Again, due to the considerably shorter distance between the impacted tooth and the lingual archwire, the range of action will be significantly decreased and there is the risk of inadvertently applying excessive extrusive forces (Figure 10.5).

•

Canine traction, eruption and alignment In cases in which traditional labial orthodontic appliances are employed, direct traction to the archwire is often the most efficient line of treatment and is best achieved using elastic ties from the impacted tooth across the line of the arch to the labial side. However, with lingual appliances the distance to the lingual archwire is very short and direct traction is rarely appropriate, except in the early eruption phase of the traction. Following eruption, the lingual wire becomes an obstacle in the way of further progress of the canine. A buccal offset with a helix may be incorporated in the canine area of the lingual archwire to increase this distance and the range of the elastic (Figure 10.3). A palatal offset may also be used, in which the archwire is designed

Fig. 10.4  Elastic thread tied between the buccal eyelet of the impacted canine and an attachment bonded on the buccal aspect of the first molar (unseen). A palatal offset has been inserted in the lingual archwire.

Fig. 10.3  Elastic thread tied between the buccal eyelet of the impacted canine and a loop in the buccal offset of the lingual archwire.

Fig. 10.5  Canine auxiliary ligated to canine eyelet under main lingual arch.

286  Orthodontic Treatment of Impacted Teeth Therefore, the auxiliary should be made from lighter wires or its activation range should be decreased. This spring is inserted piggyback under a lingual heavy rectan­ gular base arch – the latter having been placed to con­ solidate the anchor unit, while the spring provides a light extrusive force to the canine. In this way, unwanted movement on the adjacent teeth will be avoided. Alternatively, a light active palatal arch (see Chapter 6) may be used in combination with lingual appliances, although it requires double molar tubes. Preferably, these should be welded to preformed orthodontic bands, although the bands themselves may not be acceptable by the patient for aesthetic reasons, despite the fact that they are so distally sited in the mouth. Once the canine has erupted in the palate, it must be moved buccally towards its place in the arch and the same means may be used as described above. Vertical offsets, designed to erupt the tooth, are limited by the likelihood of impingement by the occlusion of the lower teeth. How­ ever, during movement towards the buccal, occlusal interferences with the opposing teeth, which are sometimes encountered when a labial appliance is used, are obviated by the bite-opening effect of the lingual appliances, which eliminates these interferences and which facilitates canine migration at this stage. The short inter-bracket span characteristic of lingual appliances is another difference which has clinical implications and will demand the much wider use of super-elastic archwires. With such short inter-bracket spans, even these wires are sometimes too stiff to be fully engaged in the bracket slots, and may often be tied tightly into the initial canine attachment only when this tooth has reached a position which is relatively close to its place in the arch. This is done to avoid the application of excessive force on the resolving impacted tooth and also to minimize the reactive forces on the adjacent teeth (Figure 10.6). When the canine reaches its place in the arch a bracket has to be bonded. In traditional labial orthodontics,

bonding of a bracket at its ideal height on the buccal aspect of the canine is usually impeded at this stage by exuberant gingival tissue, which accumulates on the buccal aspect during the canine’s migration towards the buccal, even with good oral hygiene. In contrast, bonding of a lingual bracket is much easier, since the clinical crown on the palatal side is usually fairly long, particularly if an open exposure was performed for this tooth.

Finishing procedures Finishing procedures with lingual appliances are similar to those with labial appliances. However, since torqueing auxiliaries are largely unsuitable and certainly difficult to design and insert, torque has to be introduced in the rectangular archwire or in the bracket base. As with the labial appliance, torqueing a canine with a rectangular archwire might take a long time because of the small range of deflection possible with the wire and the need for a number of progressive activations. It should be clearly understood that these torqueing deflections will generate small but undesirable reciprocal torqueing movements of the adjacent anchor teeth at each activation, which correct themselves as each activation works itself out. This is generally referred to as ‘round-tripping’ the anchor teeth, a phenomenon which has been blamed as a cause of root resorption generally. So, while torqueing auxi­ liaries are highly recommended in labial appliances to avoid this potentially harmful side-effect, since these do not derive their anchorage from a reverse torque of the adjacent teeth their use with lingual appliances is presently limited. An additional aspect of lingual treatment, already referred to, is the fact that many of the patients concerned have very high aesthetic demands and will not tolerate the extraction space of the deciduous canine without some form of temporary pontic placement. For this reason, the extraction of the deciduous canine has to be delayed until a very late stage of the treatment. If it is necessary to remove the deciduous tooth at an earlier stage, an artificial tooth must be bonded to the adjacent teeth during the intervening period (Figure 10.7). This may also be a problem with an adult undergoing any form of orthodontic treatment, although the likelihood is much less when the patient has agreed to wear labial appliances, particularly if these are all metal.

Anchorage considerations

Fig. 10.6  Nickel–titanium archwire inserted through the palatal eyelet.

One of the most important principles of mechano-therapy in the treatment of cases with impacted canines is to establish a firm anchorage unit. This is obviously true for both labial and lingual techniques. Because impacted teeth are

Lingual Appliances, Implants and Impacted Teeth  287  movement is required in the absence of adequate alternative anchorage. Mini-/micro-screws have many advantages. They are inexpensive, small, simple to place, immediately loadable and well tolerated by patients [7–11]. Their main disadvantage is their proximity to the roots, which may be damaged during placement of the screws or when the adjacent teeth are displaced [12].

Integrating implants with lingual appliances Fig. 10.7  Aesthetic pontic bonded to the first premolar. Note the impacted canine has been brought to the line of the arch, beneath the pontic.

Fig. 10.8  Trans-palatal arch integrated into lingual appliance design.

much more resistant to movement in adults than in children, the effort to bring them into alignment will be reflected in a greater loss of anchorage. This may be further undermined and the problem compounded if, in addition, the anchor teeth are periodontally involved, with loss of bone support. The use of most traditional means of enhancing the anchorage in children, such as palatal arches (Figure 10.8), consolidation of anchor units with heavy rectangular arches and intermaxillary traction, are appropriate for adults, while others, such as extra-oral appliances and lip bumpers, are taboo for adults in general, and particularly for the patient who wants the appliance to be completely invisible and who is averse to anyone knowing that the treatment is being performed at all. New opportunities have been opened for adults with the introduction of temporary and osseo-integrated anchorage devices, which have been developed and used in cases in which a large amount of tooth

A well thought-out strategy for the placement of implants offers the possibility of facilitating and shortening treatment while, at the same time, decreasing the deleterious effects of anchor loss. This may be achieved in the follow­ ing ways: 1. A titanium mini-screw may be inserted on one side of the posterior area of the palate, to provide anchorage for erupting a group 2 or group 3 canine (see Chapter 6) into the palate (Figure 10.9a). To generate the extrusive forces, a 0.016 in stainless steel ballista spring with a loop at its end may be inserted through the internal slot of the mini-screw (Figure 10.9b). The spring is activated by making a permanent bend in it, down towards the tongue, and then tying it to the pigtail ligature wire of the impacted tooth (Figure 10.9c). The elasticity of the spring exerts pressure for it to return to its more vertical resting shape and position, thereby applying extrusive force to the unerupted tooth. The ballista spring should be ligated into place at the end of the surgical procedure, while the local anaesthetic is still effective. 2. A micro-screw may be inserted into the bone on the labial side of the alveolar ridge [1] to provide the necessary anchorage for moving the tooth buccally towards its place in the arch, once it has been erupted into the palate. Elastic thread, tied from an attachment bonded on the buccal aspect of the canine to the micro-screw, will create a buccally directed force and a moment for correcting its rotation. The archwire should be offset in the canine area to permit the canine movement and a helix added in the offset will direct the buccal migration more mesially or more distally, as needed (Figure 10.10a). If the canine is located in a direct line open to the implant, then a useful alternative would involve cutting out the short span of archwire between the distal of the lateral incisor and the mesial of the first premolar to leave a larger and a smaller sectional archwire in place and the canine area unencumbered (Figure 10.10b). A continuous archwire may be reinserted once the canine is close to its place, through the palatal eyelet or a newly bonded lingual bracket. 3. In cases where direct traction of the impacted tooth to the archwire is possible from the beginning of treatment,

(a)

(b)

(c) Fig. 10.9  (a) Immediately post-surgery, showing fully sutured flap (closed procedure) with pigtail ligature from the canine attachment piercing the flap. Miniscrew inserted in the palatal mucosa near the space of the missing first molar. Ballista spring tied into mini-screw. (b) Passive state. (c) Activated by ligation to pigtail ligature, applying traction to the unerupted canine.

(a)

(b)

Fig. 10.10  (a) Elastic traction from a secondary labial eyelet to a labially situated micro-implant, via a directional helix placed in the archwire. (b) The canine is in a direct line to its place. The lingual archwire has been divided into two, leaving the canine area unencumbered.

Lingual Appliances, Implants and Impacted Teeth  289  a micro-implant may be introduced in the buccal bone at the same appointment during which the surgical exposure is performed (Figure 10.11a). An elastic force from the impacted canine to the micro-screw may then be applied immediately, while the area is still anesthetized (Figure 10.11b). If the deciduous canine has to be extracted, an aesthetic pontic needs to be fabricated and the elastic passed under the pontic. In these cases, it is recommended to delay the insertion of the implant until a period of healing of the extraction space has occurred, since the chances of failure are greater when an implant is inserted into a fresh extraction site. Thereafter, the canine may be moved under the palatal mucosa towards its place in the arch. In order to move it further buccally and also to extrude it, a titanium–molybdenum alloy

(a)

(TMA™) spring with an artificial tooth may be connected to the implant and activated buccally and vertically, as necessary (Figure 10.12). It will be seen that a group 2 canine requires two implants, one in the palate to erupt and move the canine away from the lateral incisor root and the other in the buccal alveolar plate for moving the tooth buccally into the dental arch. Group 1 cases, in which direct traction is possible, require only one implant placed in the buccal plate. The most important advantage of using orthodontic implants is that treatment of the impaction may be initiated before levelling and alignment and opening of adequate space in the arch and continued in an entirely independent manner. Hence, the clinician has two possible options:

(b)

Fig. 10.11  (a) Micro-implant inserted during the appointment for canine exposure. (b) A clear chain will be drawn beneath the pontic to the micro-implant, to apply buccal traction to the impacted canine.

(a)

(b)

Fig. 10.12  (a, b) The titanium–molybdenum alloy (TMA™) spring in its passive mode, bonded to the implant and carrying an artificial tooth. Ligation to the canine will draw the tooth vertically and buccally.

290  Orthodontic Treatment of Impacted Teeth 1. To erupt the canine concomitantly with and as an integral part of the orthodontic treatment of the other teeth. This is relevant when space opening in the dental arch is needed first. In this case, it would be wise to erupt the canine only partially (in contrast to what is recommended for labial treatment – see Chapter 6), and then to continue its buccal movement underneath the palatal mucosa until it passes the lingual archwire to the buccal side. This will avoid archwire interferences and the need to fabricate offsets. 2. To perform the entire stage of treatment required for treating the impaction before placing any orthodontic appliance. This approach is suitable in cases in which there is adequate space for the canine in the arch, but also in many other cases, in the interests of reducing the time that orthodontic appliances need to be in the mouth. The use of implants in this way is valid for both labial and lingual treatments and may significantly shorten the period the patient has to wear either unaesthetic labial or uncomfortable lingual orthodontic appliances. The idea of completing the resolution of the impaction before placing appliances is particularly advantageous in lingual treatment, since the problem of interference of canine movement by the archwire is circumvented before appliances are placed. Orthodontic treatment in general is a discipline in which a force system is set up to move certain teeth in predetermined directions and in a particular way, while at the same time preventing the reactive forces that are transferred to the anchor teeth from causing unwanted deterioration in their positions. Thus, implant anchorage, which is absolute and not relative anchorage, greatly simplifies the approach, because forces may be applied solely to the impacted tooth, thereby avoiding ill-effects on the other dentition and the need for a cumbersome orthodontic system. Implants may be placed in a wide variety of positions, both within and well outside the dental arch, and as such may be carefully planned and strategically chosen for optimal direction and range of force application. The combination of lingual appliances and implant anchorage is useful in the ortho-surgical treatment of impacted teeth in the adult patients who would otherwise reject treatment altogether because of the need to wear an unaesthetic labial appliance over a long period of time. This combination has the ability to provide answers to three major drawbacks of the ortho-surgical treatment of impacted teeth in the adult patient, namely, unimpaired orofacial appearance, length of time that fixed appliances need to be worn and anchorage.

Case report A 24-year-old woman presented with a palatally impacted left maxillary canine, an adjacent over-retained deciduous

canine and a missing maxillary left first molar (Figure 10.13a, b). Lingual brackets (Ormco 0.018 in slot) were bonded on all the teeth in the upper arch, with the aim of improving the anterior alignment, correcting the midline deviation and opening adequate space for the impacted canine and the missing first molar. Since the impacted tooth was classified as a group 2 canine, it needed to be moved in two stages: first, to erupt it into the palate to the occlusal level, in order to distance it from the roots of the lateral incisor, and second, to move it buccally into its place in the arch. To provide the extrusive forces, a 0.016 in stainless steel ballista spring with a loop at its end was inserted through the internal slot of a Spider Screw® orthodontic implant (11 mm length and 2.3 mm diameter; HDC Company, Sarcedo, Italy) [13] as described above. In this case, the mini-screw was inserted through the palatal mucosa near the space of the missing first molar, into an area of bone that would later become the molar implant site and where there was no possibility of damaging adjacent teeth (Figure 10.13c, d). In the succeeding months, the canine was erupted using a force applied from the implant, through the agency of the ballista spring. At the same time, routine orthodontic treatment was under way on the other teeth using forces provided from a conventional lingual orthodontic appliance (Ormco 0.018 in slot), based on all the other teeth. The two systems operated independently in the early stages and there was no initial interaction between them. When enough space had been created in the arch, an additional eyelet was placed on the buccal aspect of the canine and the direction of traction altered to a pure buccal tipping movement to bring the tooth into the arch. A new, round, lingual archwire with a buccally directed offset and a loop was fabricated. Ligation with elastic thread tied between the buccal eyelet of the impacted tooth and the loop produced the buccally directed force at this stage (Figure 10.13e). When the canine approached its place in the arch, the deciduous canine was extracted and the rectangular wire changed to a 0.014 in nickel–titanium wire, inserted through the palatal eyelet of the impacted tooth. In addition, a clear elastic thread was inserted through the buccal eyelet and ligated to an attachment bonded on the buccal side of the upper molar (Figure 10.13f). Subsequently, the lingual eyelet was changed to a lingual bracket and a 0.016 × 0.022 in in CuNiTi archwire was reinserted. Active treatment was completed in 19 months (Figures 10.13g–i). The spider screw was subsequently removed without complications. No treatment was performed in the lower arch. At the end of the orthodontic phase, the patient was referred for placement of a single tooth implant in the reopened extraction site of the maxillary first molar.

Lingual Appliances, Implants and Impacted Teeth  291 

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 10.13  Pre-treatment clinical (a) and panoramic (b) views showing the impacted maxillary left canine, the over-retained deciduous canine and the missing maxillary first molar. Mini-screw inserted through the palatal mucosa and into the bone opposite the space of the missing first molar: (c) clinical view, (d) radiographic view. Canine traction: (e) elastic traction to buccal offset in archwire, (f) engagement of nickel–titanium wire in palatal eyelet and elastic chain in buccal eyelet, drawn to buccal attachment on second molar. Post-treatment intra-oral views: (g) frontal, (h) left side, (i) post-treatment panoramic view showing the impacted canine aligned in the arch.

292  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(i) Fig. 10.13  (Continued )

References   1.  Park HS, Kwon OW, Sung JH. Micro-implant anchorage for forced eruption of impacted canines. J Clin Orthod 2004; 38: 297–302.   2.  Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003; 124: 509–514.   3.  Becker A, Brin I, Ben-Bassat Y, Zilberman Y, Chaushu S. Closederuption surgical technique for impacted maxillary incisors: a postorthodontic periodontal evaluation. Am J Orthod Dentofacial Orthop 2002; 122: 9–14.   4.  Chaushu S, Brin I, Ben-Bassat Y, Zilberman Y, Becker A. Periodontal status following surgical-orthodontic alignment of impacted central incisors with an open-eruption technique. Eur J Orthod 2003; 25: 579–584.   5.  Chaushu S, Becker A, Zeltser R, Branski S, Chaushu G. Patients’ perception of recovery after exposure of impacted teeth: a comparison of closed- versus open-eruption techniques. J Oral Maxillofac Surg 2005; 63: 323–329.

  6.  Kornhauser S, Abed Y, Harari D, Becker A. The resolution of palatally impacted canines using palatal-occlusal force from a buccal auxiliary. Am J Orthod Dentofacial Orthop 1996; 110: 528–534.   7.  Roberts WE, Marshall KJ, Mozsary PG. Rigid endosseous implant utilized as anchorage to protract molars and close an atrophic extraction site. Angle Orthod 1990; 60: 135–152.   8.  Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of palatal implants for orthodontic anchorage. Design and clinical application of the orthosystem. Clin Oral Implants Res 1996; 7: 410–416.   9.  Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997; 31: 763–767. 10.  Melsen B, Costa A. Immediate loading of implants used for orthodontic anchorage. Clin Orthod Res 2000; 3: 23–28. 11.  Lee JS, Park HS. Micro-implant anchorage for lingual treatment of a skeletal Class II malocclusion. J Clin Orthod 2001; 35: 643–647. 12.  De Clerck H, Geerinckx V, Siciliano S. The zygoma anchorage system. J Clin Orthod 2002; 36: 455–459. 13.  Maino BG, Bednar J, Pagin P, Mura P. The spider screw for skeletal anchorage. J Clin Orthod 2003; 37: 90–97.

11 Rescuing Teeth Impacted in Dentigerous Cysts

Dentigerous cysts

294

Radicular cysts

296

Treatment principles

297

The prognosis of teeth which have been severely displaced by cysts

299

Integrating spontaneous resolution into a combined treatment regimen

304

Eyelets and brackets

316

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

294  Orthodontic Treatment of Impacted Teeth Cysts are found in a variety of tissues and in many sites in the human body. They are fluid-filled, epithelium-lined, balloon-like lesions, which generally enlarge progressively and painlessly due to hydrostatic pressure from within. If they are developing in a homogeneous medium, then the laws of physics determine that they will be spherical in shape. If the medium is bone, then this will resorb in response to pressure from within, thereby progressively permitting the enlargement. Simultaneously, there is a reactive bone apposition process on the outer side, which causes the bone to become expanded. This apposition is slower than the resorption from within, and so the bony expansion is accompanied by a thinning of the bony walls of the cyst, which may eventually become paper-thin. In the final instance, the cyst will resorb the last remnant of the hard tissue to become fluctuant beneath the skin or, in the context of this book, the oral mucosa.

Dentigerous cysts A dentigerous cyst is a specialized type of cyst insofar as it is located around the crown of an unerupted tooth and arises as an expansion of what is normally the very narrow space

(a)

between the inner and outer enamel epithelia of the dental follicle, in which the completed crown of the tooth has developed. These two layers meet at the cemento-enamel junction (CEJ) at the neck of the developing tooth [1]. The cystic area enlarges due to the production of fluid by the epithelium, forcing the layers apart into its typical spherical shape, except where the crown of the tooth protrudes into the cyst, with its long axis traversing the centre of the lesion. In its early stages, therefore, it is difficult to distinguish a dentigerous cyst from a benign enlargement of the dental follicle, and between that and the normal follicle of the tooth. Furthermore, when eruptive movements of the tooth bring it through the bone and in close proximity with the oral mucosa the early dentigerous cyst may be fluctuant to palpation, is termed an eruption cyst and usually resolves spontaneously by rupture into the oral cavity. The tooth then erupts normally, its gingival attachment becomes normal and no subsequent signs of the earlier pathology remain. However, when the cyst becomes larger, the pressure from within overcomes the tooth’s inherent eruptive force potential to stop its normal eruption, and it may even cause the tooth to ‘back up’ along its former eruption path, displacing it apically, while still remaining in the middle of the cyst (Figure 11.1). It

(b)

(c) Fig. 11.1  A dentigerous cyst surrounds the crown of the mandibular right first molar has arrested eruption and has apparently slowed down root development. (b, c) The follow-up radiographs, taken two and five years later, show space closure having occurred from both the distal and the mesial, impacting the second premolar. The bizarre root morphology of the molar is the same on the affected and unaffected sides. Nevertheless, for what seemed a short root of questionable prospects for further growth in its initial position, growth has rebounded very impressively.

Rescuing Teeth Impacted in Dentigerous Cysts  295 

(a)

(b)

(c) Fig. 11.2  A large cyst occupies much of the right side of the maxilla. (a) The anterior occlusal film shows the central incisor ‘backed up’ in line with its long axis. (b) The initial panoramic film shows the lateral incisor and both premolars laid out horizontally in the floor of the cyst. The canine has become displaced posteriorly into the molar region (arrow). The location and orientation of these teeth defines the perimeter of the cyst. Because the central incisor has been displaced superiorly and posteriorly, and is distant from the film, its image is beyond the focal trough of the film and hence has largely disappeared. (c) A Waters projection radiograph of the skull shows the degree of buccal displacement of the canine (arrow), indicating the lateral boundary of the cyst.

seems, therefore, that the term ‘eruption cyst’ may represent a state of pressure equilibrium between the forces of eruption and the opposing force of intra-cystic pressure. With a smaller eruption cyst, the forces of eruption might prevail, as we have pointed out above. However, a larger eruption cyst may require surgical incision to bring about decompression, which will then permit the tooth to erupt spontaneously and quite quickly in the younger patient. Regarding the affected tooth itself, its long axis is generally perpendicular to the epithelial outer wall of the cyst at

its CEJ (Figure 11.2a). A good portion of the apical section of its root remains firmly in bone, but the pressuregenerated enlargement of the cyst will cause its lining to circumferentially and progressively outline more and more of the otherwise bared coronal portion of the root, by a resorptive squeezing out of the crestal area of bone. With further expansion, the lateral aspects of the cyst come up against adjacent unerupted teeth, which become pushed aside as their supporting bone becomes thinner and as the cyst lining comes into direct contact with their

296  Orthodontic Treatment of Impacted Teeth

(a)

(b)

Fig. 11.3  (a) An incomplete root canal treatment has been performed in the mandibular left deciduous canine, as seen on this panoramic view. (b) A routine follow-up panoramic radiograph, taken prior to impending orthodontic treatment, reveals the development of a dentigerous cyst around, and displacement of, the permanent canine. (Courtesy of Dr M. Barzel.)

periodontal ligament (PDL). Each of these teeth then becomes profiled in the walls of the cyst, with only a thin epithelial lining to cover one side of the bared tooth along its full length (Figure 11.2b, c). The other side of the displaced adjacent tooth is invested by bone, with PDL intervening over the root area and its own dental follicle intervening in the crown area. The degree of displacement of these teeth will depend on the size of the cyst, but they lie in and are oriented parallel to the walls of the cyst, in contrast to the perpendicular orientation of the causal tooth. Histologically, the cyst lining is squamous or stratified squamous epithelium and as such is similar to the follicle from which it originated. Thus, the only criterion for distinguishing between an enlarged follicular sac and a dentigerous cyst is size, as seen on a periapical radiograph. Accordingly, a workable definition for a dentigerous cyst is when the distance between the crown of the tooth and the dental sac is larger than 2.5–3 mm on the film. This is the definition most frequently used in radiology and surgery. However, we may like to refine this definition with more discerning biological criteria, which take into account the implications of the increased hydrostatic pressure within the lesion. Thus, should the eruptive progress of the affected tooth be halted or reversed, or should the radiolucent outline of the lesion appear to connect with the tooth some way down the root, apical to the CEJ, these might be considered more valid diagnostic signs. The aetiology of a dentigerous cyst is strictly unknown, although it is associated with chronic local inflammation, as may be seen when the deciduous predecessor has become non-vital and an apical granuloma has initiated cystic change in the follicular sac of the unerupted permanent successor. An incomplete root canal treatment may leave the deciduous tooth symptomless, but the chronic periapical lesion may remain unresolved and this may act

Fig. 11.4  The anterior portion of a panoramic view showing cystic enlargement of the follicles of the two maxillary permanent canines.

as the irritant that induces a cyst to develop from the follicle of the permanent successor (Figure 11.3). Unerupted permanent teeth, particularly maxillary canines, often exhibit enlarged follicles, and these may sometimes become further enlarged (Figure 11.4). This seems to occur frequently when there is a close association with the roots of the lateral incisors, although no specific explanation is forthcoming.

Radicular cysts After root formation of a tooth is completed, Hertwig’s root sheath disappears, leaving behind only the epithelial rests of Malassez in the immediate area. These remnants may sometimes be stimulated by the presence of a periapical granuloma to become cystic [2]. The radicular cyst is therefore to be found at the apex of a non-vital tooth, and it too may grow at the expense of the surrounding bone, to displace and partly envelop unerupted adjacent teeth, with the crowns and roots covered by the cyst epithelium. In this

Rescuing Teeth Impacted in Dentigerous Cysts  297  case, all the displaced teeth will be found in the walls of the cyst and oriented at a tangent to the cyst lining that covers them. No tooth will have its entire crown enveloped within the cyst, and the cyst lining will not be attached to the cervical area of any one of the teeth involved. Histologically and clinically, the radicular cyst is similar to the dentigerous cyst and the clues to its identity are largely clinical (Figure 11.5). Accordingly, the following discussion of treatment and outcome will not differentiate between the two in any substantial manner.

(a)

(b) Fig. 11.5  This figure shows two similar situations arising from different causes. (a) The crown and coronal part of the root of the second premolar are encompassed within the cyst and the orientation of the tooth is towards the middle of the cyst. The asymmetry may be due to the relative ease with which the first premolar root has been moved away from the lesion, while the more robust, two-rooted molar has withstood the cyst pressure. This is a dentigerous cyst. (b) The root of the erupted first premolar has been displaced mesially as with the above case, but the second premolar has been pushed distally against the molar and there has been distal root movement away from the cyst. There has been total stripping of bone support of the entire mesial side, while a thin wedge of bone can be seen between the molar and the affected premolar. This is a radicular cyst, presumably due to an incomplete root treatment on the second deciduous molar.

Treatment principles Surgery Professional intervention may influence the future of the displaced tooth, depending on the type of treatment employed to resolve the cyst. The cyst may be opened and its lining completely shelled out in a procedure called enucleation [3]. The excised tissue is then sent for histological examination. Following the procedure, the crown of the tooth is left fully exposed within the cystic cavity and the tooth itself exhibits a high degree of mobility, due to its very rudimentary and reduced supporting periodontal attachment. A complete and hermetic closure of the surgical flap is usually attempted, sealing the former cyst cavity from the exterior to protect the exposed bone and soft tissue from infection. The aim is that this will fill with a blood clot and healing is by primary intention. If the cyst is very large, then the chances of infection and breakdown of the clot become significant and, even in successful cases, the associated unerupted tooth becomes deeply buried in the newly forming bone, and it will need to erupt a considerable distance through this repairing bony tissue. In such circumstances, spontaneous eruptive movement of the tooth may be slight and a tooth grossly displaced by a large cyst may remain in an inaccessible position, following a fillingin of the surrounding tissues. Its extraction may then be unavoidable [4]. The prognosis for its eruption would appear to be in inverse proportion to its distance from the oral cavity. In the event that the blood clot breaks down due to infection and the area is left to heal by secondary intention, the entire former cystic area remains exposed to the exterior and will require some form of protective dressing or pack. In this situation, most of the teeth involved will need to be extracted, leaving a large defect of the basal bone in the final analysis, which may alter the shape and contour of the patient’s face. This will have marked functional, cosmetic and psychological consequences in the long term [4], with the need for artificial replacement of the missing teeth and, possibly, even a maxillofacial prosthesis to overcome the basal defect. Accordingly, enucleation is generally recommended for relatively small cysts. For larger cysts, a two-stage procedure is often advised, in which the first stage is aimed at decompression and drainage of the cyst without removing its epithelial lining. Several months later, when the cyst has reduced in size, the lesion will be reopened and the remaining epithelium shelled out, in what has been termed the ‘curative enucleation of the cyst lining’ [4]. There can be little doubt that total removal is not always easy to achieve, since the exercise may threaten the unerupted teeth that are lodged in the walls of the cyst (Figure 11.6). These teeth have a very limited, rudimentary and tenuous periodontal attachment to the adjacent bone. Thus, the teeth themselves may be inadvertently plucked from their places and, conversely, some detached areas of epithelium may remain within the healing tissues, which may later regenerate.

298  Orthodontic Treatment of Impacted Teeth

(a)

Figure 11.6a shows a portion of a panoramic view of the right side of the lower jaw of a 7-year-old patient, in which a large cyst is present. It seems likely that this is a radicular cyst related to the non-vital second deciduous molar, which has pushed aside the developing and largely rootless un­ erupted second premolar, whose long axis is parallel to the wall of the cyst. This patient was treated by extraction of the deciduous tooth, together with excision and complete enucleation of the cyst. In the accompanying transfer letter, the surgeon noted that he had found it necessary to remove the second premolar, and the second film (Figure 11.6b), taken postoperatively, shows the absence of this tooth. From the surgeon’s perspective, three points are noteworthy in the management of this patient: 1. The very underdeveloped second premolar had a minimal attachment to its surroundings, as seen on the original film. 2. The cyst lining itself probably constituted a significant part of the attachment of this tooth. 3. During a surgical procedure of this type, visibility inside a cyst cavity is poor.

(b)

(c) Fig. 11.6  (a) A radicular cyst, due to unresolved periapical pathology after root canal treatment of a second deciduous molar. The very rudimentarily developed second premolar has become severely displaced inferiorly in the lower border of the mandible. (b) The same view immediately after enucleation of the entire cyst lining. (c) The same view six months later, showing bony fill-in.

The surgeon may have judged that a tooth in this position, with this orientation, with an obvious absence of bony support and in the absence of a developed root had a poor prognosis and therefore removed it. Indeed, had the tooth remained in place, there is room to question whether it would have continued to develop a normal root and if it could ever have been expected to erupt into the mouth, either spontaneously or with orthodontic help. However, its root shows the very earliest stages of its development, is wide open and is vital, indicating potential for the genesis of a reasonable root, which will generally occur in time, as illustrated above (Figure 11.1). One remaining possibility is that under these exceptional circumstances it is conceivable that this very early developing tooth, with its very tenuous attachment to its surroundings, had been dislodged inadvertently during the removal of the cyst lining! It should be remembered that the lining of a dentigerous cyst arises from the inner and outer enamel epithelia of the tooth germ. In the long term and under normal circumstances, this epithelial tissue of the follicle eventually fuses with the epithelium of the oral mucosa, opens and everts to form the normal gingival attachment of the healthy tooth (see Chapter 6). During cyst formation the lining usually remains unaltered, and opening it to the oral environment, with a marsupialization procedure, will allow it to become contiguous with the oral mucosa. In time, a metaplasia of its epithelium will occur, as is the case with every normally erupting tooth, following which the former cyst lining will become histologically indistinguishable from the remainder of the oral mucosa. Marsupialization is the surgical treatment option that is to be preferred for the larger lesions of this type [5–8]. This

Rescuing Teeth Impacted in Dentigerous Cysts  299  involves opening the cyst into the oral cavity at its most superficial point and maintaining the patency of this orifice over a long period of time. The cut linings of the cyst and the oral mucosa fuse to become continuous with one another. The teeth involved directly or indirectly with the lesion are deliberately left undisturbed and remain covered by the thin epithelial continuum of the cyst lining. In time, the lined cyst cavity becomes smaller and smaller as bony regeneration occurs behind the epithelium, to fill the defect in from the bottom up. As it does so, the causal tooth is generally carried bodily forward, as if on the crest of a wave, in the vanguard of the naturally occurring regeneration. Understanding this natural process was, no doubt, the stimulus that caused periodontists to invent guided tissue regeneration in which bone will regenerate under an artificial membrane, by deliberately preventing the encroachment of epithelium. Of much greater significance, the areas of root surface that had earlier become denuded by the enlarging cyst, with only the thinnest epithelial covering of cyst lining, now become infused with new bony support. Bone levels return to the more normal values seen in other unerupted teeth due to the osteogenesis that lifts the epithelial lining away from the root surface. In this way, teeth that previously appeared to be in hopeless situations may now take on a new lease of life, provided that orthodontic treatment may later be instituted to complete any final eruptive assistance they may need and then to align them. However, any attempt to apply orthodontic traction to teeth before complete resolution of the cyst and before the maximum amount of spontaneous eruption has occurred will extrude them ahead of the advancing bone, thereby weakening their bony and periodontal support and prejudicing their longevity. Spontaneous resolution of the impaction may be expected to occur to a significant degree when the cyst is eliminated in this way, and several truly remarkable cases have been reported in the literature [5, 6]. From our experience in Jerusalem, these case reports are by no means exceptional and, with rational and careful management, have been repeated with a high degree of reliability in the most extreme cases that have come under our care [8]. It is therefore to be concluded that the cyst must be treated first and that monitoring of the healing process should be instituted until the bone has completed the reparative fill-in of the bony defect. Only at that point, which will be many months later, should an assessment be made of how much improvement has occurred naturally, how much more may be expected and how much orthodontic treatment is needed to improve the positions of the teeth. Not only, therefore, is there no value in bonding an attachment to the tooth at the time that the marsupialization is undertaken initially, but the procedure is likely to be quite harmful to the natural recuperation and positional

improvement of the target teeth and for the health and integrity of the surrounding tissues – not least the cyst lining. From the point of view of the oral and maxillofacial surgeon, treatment of this cyst is a priority in order to confirm the relatively innocent diagnosis. It must be remembered that, until a biopsy and pathological investigation are performed, the diagnosis is only tentative. The more sinister alternative diagnoses are fortunately extremely rare; nevertheless, the surgeon cannot take the chance involved in delaying the performance of the necessary diagnostic procedures until the patient is ready to accept orthodontic treatment. Therefore, the first stage of surgical treatment, aimed at eliminating the pathological entity, must be regarded as obligatory, and must include histopathological examination of biopsy material and careful follow-up. Orthodontics From the orthodontic point of view, the patient should be prepared for treatment, with an understanding of the demands of oral hygiene and the need to wear appliances and to expose the impacted teeth. These requirements may often be fulfilled quite quickly, but it is unfair to coerce young patients into a hurried decision before they are ready and is usually counterproductive. It would be logical to infer from this discussion that, although the orthodontist has much to contribute to the outcome of the treatment, this contribution relates to the later stages and not to the immediate prospects. It would therefore be wise to include the orthodontist in the decision-making team, but inappropriate for him/her to become actively involved in the early stages of treatment, until much of the bony fillingin has occurred and the tooth has migrated down ahead of this.

The prognosis of teeth which have been severely displaced by cysts Given the presence of defined pathology and an extreme displacement of the affected tooth or teeth in relation to dentigerous cysts in general, the orthodontist and the oral surgeon need answers to the following five questions, before being equipped to formulate a treatment protocol: 1. Following treatment to eliminate the cyst, how much improvement in the realignment of the severely displaced teeth can be expected to occur spontaneously? 2. Can these teeth be subsequently brought into the arch? 3. Might there be disturbances or anomalies in the calcification or form of these teeth that may occur as the result of the circumstances and the site of their development, which may limit the quality of the treatment outcome? 4. Will they be accompanied by a good periodontium and bone support?

300  Orthodontic Treatment of Impacted Teeth 5. Can this be done in such a way as to make them indistinguishable from any other teeth, at the end of treatment? The short answer to four of these questions is in the emphatic affirmative, as the following discussion will

(a)

attempt to illustrate. Perhaps the most dramatic part of this is the incredible potential for spontaneous resolution, with an amazing response of the body to regenerate lost bone and to restore normal anatomy (Figure 11.7). Figure 11.8 shows clinical and radiographic views of an 8-year-old child with a cyst of dental origin in the left man-

(b)

Expanded cyst cavity (c)

(d)

Fig. 11.7  Extreme displacement of teeth and its spontaneous resolution. (a) The left side of the patient’s face shows considerable swelling when first seen. (b) The left side of the maxilla in the canine premolar area shows bone expansion and a blue discoloration of the overlying mucosa, with fluctuant mucosal swelling. (c) In the initial panoramic view, a large radiolucent cystic area may be clearly discerned and demarcated approximately with the orange broken line circle, which has pushed aside the lateral incisor and the two premolars (#24, #25) and has displaced the maxillary canine (#23) very high and close to the inferior border of the orbit. The origin of the cyst is likely to have been caused by the presence of the heavily filled and poorly restored maxillary first deciduous molar. (d) Gross maxillary expansion and the degree to which displacement of the canine and premolar has occurred, may be easily seen in this coronal ‘slice’ from the CBCT. (e) The canine can be seen to protrude anteriorly from the base of the nose. (f, g) More than 3 ml of fluid is drawn from the cyst. (h) A large opening for continued drainage is made, through which the unerupted first premolar can be discerned. (i) The stomium is loosely packed with an antiseptic-impregnated ribbon pack. (j) The panoramic view taken 26 month later shows a total reversal of the condition, with the maxillary left canine and premolars erupting into ideal locations and a regeneration of the lost bone on that side of the maxilla. The only orthodontic treatment provided in this case was the placement of the soldered palatal arch space maintainer. An eruptive cyst is now seen surrounding the crown of the unerupted right canine.

Rescuing Teeth Impacted in Dentigerous Cysts  301 

(e)

(f)

(g)

(h)

(i) Fig. 11.7  (Continued )

302  Orthodontic Treatment of Impacted Teeth

(a)

(b)

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(e)

(f)

Fig. 11.8  (a, b) Clinical lateral and occlusal views of the left side to show expansion of the alveolus adjacent to the deciduous canine and first molar. The deciduous molar has a large restoration. (c) The panoramic view shows a large cystic lesion apparently centred on the horizontally displaced, unerupted premolar, ‘pushing’ the unerupted canine mesially. The premolar has a 110° tip, and the canine 30°, from their normal angulation. (d) The deciduous canine and first molar are extracted and the wound packed and sutured. (e, f) A fixed lingual arch space maintainer is placed. (g, h) Thirteen months later, the permanent canine and first premolar have erupted into their normal locations. (i) A panoramic view taken at the same time shows the canine to have self-corrected by 30°, while the premolar has uprighted spontaneously by 115° and now sports a 5° distal tip.

Rescuing Teeth Impacted in Dentigerous Cysts  303 

(g)

(h)

(i) Fig. 11.8  (Continued )

dibular canine/premolar area. In terms of aetiology, it may be reasoned that this is a radicular cyst originating from the non-vital deciduous first molar, which has displaced the first premolar and canine downwards and mesially to a very marked degree. Equally, it may be argued that the chronic periapical granuloma of the deciduous tooth has stimulated the follicular sac of the first premolar to enlarge into a dentigerous cyst and, because of the resistance of the erupted deciduous tooth, the premolar and canine have rotated downwards and mesially. The long axis of the premolar appears to traverse the middle of the cyst. As already noted, this argument is academic, since the approach to treatment will be the same in either case. Treatment was provided in the form of extraction of the deciduous canine and deciduous first molar. This effectively resulted in the surgical marsupialization of the cyst by virtue of the fact that, as expected, the cyst lining was ruptured during the extraction. The remainder of the cyst lining was left undisturbed. A pack was placed in the wound and the socket margins partially approximated with sutures. The sutures and pack were removed a week or so later and, at the same time, a lingual arch space maintainer was placed.

In follow-up visits over the succeeding few months, the two displaced teeth improved their positions and erupted into the mouth very rapidly and without any further assistance. A comparison of the panoramic radiographs taken at the time of surgery and at the 13-month post-surgery follow-up shows the amount of spontaneous correction that occurred, with the regeneration of alveolar bone into the void previously occupied by the cyst. In the pre-surgical film, the canine shows a mesial tipping displacement of about 30°, and the first premolar about 110° from their normal axial inclinations. Ten months later finds the long axis of the first premolar fully corrected and that of the canine to exhibit a 5° over-correction and a distal tilt! All this had occurred spontaneously, strictly due to a reversal of the progress of the expanding pathological entity that had caused the initial displacement and without the need for any orthodontic correction [7]. The larger the cyst, the greater is the displacement and, with the defusing of the lesion, there is a great deal of migration of the affected teeth in a very short time and it is directly related to the contraction of the previously cystic area. There can be no question that corrective treatment of

304  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c) Fig. 11.9  (a) The initial film taken in January 2007 is of an 8-year-old patient with a history of extensive dental caries and early extraction of many deciduous teeth. The left side of the maxilla exhibits a large cyst extending from the lateral incisor to the first molar, which has apparently displaced the canine against the mesial extremity wall of the lesion. It seems likely that this developed from apical pathology associated with one of the extracted deciduous molars. Surgical treatment of the cyst was performed a month or two later. (b) The film taken 7−8 months later shows considerable reduction in the size of the lesion and a distinct migration of the canine distally. (c) At approximately one year post-surgery, the canine is seen to have moved much further distally and occupying a location between the two premolars. Note that the development of the roots of the canine and premolars has continued uninterrupted.

these cysts of dental origin depends largely on surgical intervention and that the displacement of teeth trapped within or adjacent to them may sometimes be completely reversed. Notwithstanding, total spontaneous resolution is not always the outcome and it does not always bring the teeth back to their ideal place in the dental arch (Figure 11.9).

Integrating spontaneous resolution into a combined treatment regimen Trauma to the anterior teeth is common in the very young and may result in the loss of vitality of a deciduous incisor, as indicated by a deleterious colour change of the crown of the tooth. Should this tooth remain untreated in the long term, the chronic granuloma present may itself produce a radicular cyst, or it may stimulate the follicle of the devel-

oping central incisor to become cystic, as we have described above. Clinically, an expansion of the alveolus is seen both in the labial sulcus and on one side of the anterior portion of the palatal vault, where its normally concave anatomic form has become convex (Figure 11.10a, b). In the panoramic radiograph (Figure 11.10c), the unerupted central incisor shows a marked height discrepancy, with its long axis remaining in the vertical plane. This tooth is bare of bone on its distal side and is in contact with continuous bone from crown to developing root end on its mesial side. This is due to hydrostatic pressure from within the cyst, which has pressed the tooth against the bony wall of its perimeter, suggesting the diagnosis of radicular rather than dentigerous cyst. The dilaceration of the root of the central incisor is also indicative of its lying in the wall of the cyst. The canine is seen on the panoramic view to be markedly displaced

Rescuing Teeth Impacted in Dentigerous Cysts  305 

(a)

(b)

(c)

(d)

Fig. 11.10  (a, b) Clinical anterior and occlusal views of a 6-year-old child, showing a discoloured deciduous central incisor and considerable alveolar expansion in the labial sulcus and palatal area on either side of the teeth. (c) The panoramic view at age 6 years shows the left incisors and canine arranged in the form of a circle, apparently ‘chasing each other’s tails’. The first premolar has also been affected by the presence of the cyst whose perimeter may be fairly accurately assessed, using these four teeth as landmark signs. (d) All four deciduous incisors were removed and the cyst cavity opened to the exterior. (e, f) These intracystic photographs were taken with a camera-mounted optic probe, which was passed into the cyst cavity to show the glistening, epithelium-covered incisors in the cyst wall. (g) The edges of the oral mucosa flaps, which are also the deciduous tooth sockets, were approximated after including a small pack and drain to permit further drainage and healing of the oral mucosa to the cyst lining. (h) The follow-up radiograph taken 26 months later shows that the incisors and canine have moved forwards and downwards and have come together very close to their normal locations. This, together with the bony trabeculation seen on the film, indicates the elimination of the cystic cavity. Note that the central and lateral incisors have dilacerated roots in their apical areas. (i, j) There has been spontaneous eruption of the affected incisors, a little later than normal, but the orientation of their long axes means that considerable root torque will be necessary. (k, l) At the age of 9 years, a 2 × 4 appliance (modified Johnson, twin arch) was placed to align these teeth and to improve the parallelism of the roots. (m) At the end of the short first phase of treatment, it was noted that further labial root torque of the lateral incisor was not possible due to the apical section of the dilacerate root of the central incisor and also by the mesio-labial location of the erupting canine. (n–r) The final photographic records of the treated case, at age 12 years, show an excellent position, crown height, gingival level and appearance of the two incisors. The quality of the canine gingival appearance, gingival level and crown height are poorer than for the canine of the unaffected side. However, the lateral incisor needs further labial root torque and the canine needs palatal root torque, which could not be completed adequately because of the root dilacerations. (s, t) The occlusal views show the bonded multi-strand wire splints. (u–w) The intra-oral clinical views seen two years post-treatment. (x–z) Close-up views of the anterior region to show the gingival condition and appearance at two years post-treatment. (a’) Two-year follow-up periapical radiographs to show the excellent bone resolution and the root entanglement that limits the root movement possible.

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

Fig. 11.10  (Continued )

Rescuing Teeth Impacted in Dentigerous Cysts  307 

(m)

(n)

(o)

(p)

(q)

(r)

(s)

(t)

Fig. 11.10  (Continued )

308  Orthodontic Treatment of Impacted Teeth

(u)

(v)

(w)

(x)

(y)

(z)

(a') Fig. 11.10  (Continued )

Rescuing Teeth Impacted in Dentigerous Cysts  309  upwards and backwards with a distal tip, and the lateral incisor has adopted a severe horizontal posture inferiorly. The unerupted developing premolars are also mildly affected. The marked variation in the long axes of the three anterior teeth, as though they are lying in a circle, is indicative of the fact that they are to be found in the wall of the cyst and, as such, they outline its extent. Using these indicators, it is now possible to estimate the shape and size of the cyst cavity and to define its borders. In this case, the non-vital deciduous central and vital deciduous lateral incisors were extracted, which was all that was needed to produce a marsupialization of the cyst. The extractions immediately brought about spontaneous drainage of the cyst, and the edges of the torn lining of the cyst healed and became contiguous with the oral epithelium. The insertion of a very small camera, mounted on a long optic probe, into the cyst cavity allowed us to see and record the appearance of the teeth, as they lay glistening under the epithelium, in the walls of the cyst (Figure 11.10e, f). No further treatment was provided at that time and the patient was followed up periodically. The two permanent incisors of that side began to erupt, after 26 months, into abnormal positions. A simple partially bracketed appliance (a modified Johnson’s twin-arch appliance – see Chapter 5) was placed to draw the teeth to their normal positions. In Figure 11.10l it can be seen that the central incisor is in an excellent position, with a short clinical crown and even an excess of gingival tissue. While the lateral incisor crown has been brought into alignment, the orientation of its long axis indicates a strong palatal displacement requiring considerable root torque, which may usually be corrected at this stage or in the full permanent dentition, when a second phase treatment will be initiated. However, the radiographs reveal a marked dilaceration of the root of the central incisor. If we study the initial panoramic view of the case, it will be seen that the tooth had been displaced very high in the alveolus and its root was developing in close relation to the floor of the nasal cavity. It is reasonable to assume that its development in this site and subsequent deliverance from this extreme displacement in the wall of the cyst was the cause of the dilaceration. This does not account for the lesser dilaceration of the lateral incisor. The orientation of the apical portion of the root is distal and labial to the root of the lateral incisor, as can be determined from the two periapical films, employing the tube shift method (Figure 11.10n). This implies that labial root torque of the lateral incisor must not be attempted before this anomaly is remedied or circumvented, if this is possible and judged justifiable. The following options are available: 1. Leaving the situation without further treatment and the lateral incisor in this position. 2. Rotating the central incisor disto-labially, which effectively rotates the abnormally shaped apical portion labi-

ally and mesially. However, this will then involve crowning the tooth to achieve a good appearance. 3. Performing root canal treatment and an apicoectomy, thereby eliminating the root apex, but compromising the health and appearance of the tooth. 4. Over-uprighting the central incisor root mesially, thereby moving the apical portion mesially and superiorly. This may then be reversed, when the lateral incisor has been adequately (or possibly excessively) torqued, to permit the root apex of the central incisor to be re-sited palatal to the lateral incisor root. This was the treatment actually attempted, in the full permanent dentition, as a second-phase procedure. Unfortunately, the degree of the dilacerations of both the incisors did not permit full torque of the root of the three teeth involved (Figure 11.10o–s). Because dentigerous and radicular cysts are not normally associated with pain, they may become very large before the patient seeks treatment, and the presenting symptom may be facial swelling, as seen in Figure 11.11a–g. In this patient, there was marked swelling on both sides of the alveolar processes, over-retention of the deciduous teeth in the area and non-eruption of the permanent teeth that would normally be erupting at this time. The maxillary right deci­ duous central incisor was discoloured and non-vital. The radiographs of the area (Figure 11.11h–l) indicate severe displacement of all the teeth on that side of the maxilla, from the anterior midline to the first permanent molar, as well as an upward extension of the cyst, raising the floor of the maxillary antrum. The pattern of the displacement clearly indicates the extent of the cyst. The maxillary central incisor of that side has been pushed superiorly and mesially across the midline. The root apices of the lateral incisor and, to a lesser extent, the two premolars have been pushed inferiorly and distally to cause these teeth to lie almost horizontally above their deciduous predecessors in the floor of the cyst, while the canine has been displaced superiorly and laterally in close relation to the floor of the orbit. Given the orientation of these teeth, together with the presence of a non-vital deciduous incisor, it seems likely that the cyst was radicular, but this is by no means certain. With much of the right side of the patient’s maxilla virtually devoid of bone, the likelihood of a minor blow to the face causing a pathological fracture and becoming the presenting symp­ tom was quite high. Under the influence of simple infiltration local anaesthesia, the fluid was first drained from the cyst using a syringe and wide bore cannula needle, easily passed directly through the buccal sulcular area of the bony alveolar ridge, which had become expanded and extremely thin due to the size of the cyst. A relatively large quantity of brownish liquid was withdrawn from the cyst into the syringe. A circular incision was made in the immediate area over the cyst, to produce a hole of about 5 mm in diameter, communicating

310  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

Fig. 11.11  (a) A 7.6-year-old boy presented because of swelling of the right side of the face. (b–d) Clinical views of the right side of the maxilla show extensive hard swelling of the buccal alveolus and palatal areas, extending from the first molar to the anterior midline. (e–g) Clinical views of the dentition showing normal buccal and antero-posterior relations, with a discoloured maxillary right deciduous central incisor. (h–k) Oblique occlusal, panoramic, Waters’ view, and lateral and postero-anterior cephalograms show the extent of the cyst and the extreme degree to which the involved teeth have been dispersed in its walls. (l) The barrel of the syringe contains a brownish liquid, drawn off from the cyst through the cannula. (m, n) A 10 mm diameter stomium is established. (o) At the 39 months follow-up visit, at age 11 years, the hard swelling in the face has disappeared. (p, q) Panoramic and oblique occlusal films show that the affected teeth have come together, indicating elimination of the cystic area and its replacement by bone. The bony trabeculation can be seen around the teeth on the occlusal view. (s, t) Clinical views of the affected area from the right and the front. The two premolars are erupting and the stomium made into the former cystic area has remained patent. (u–w) Treatment initiated at age 11 years, aimed at levelling, alignment and the creation of space for the three unerupted teeth, including midline correction. (x) Eight months later, a pre-surgical panoramic view shows the widely divergent long axes and locations of the affected teeth. (y) The lateral incisor is seen ‘peeking’ through the stomium. (z, a’) Exposure and eyelet bonding, after full flap reflection. (b’) The flap is fully sutured back, with the pigtail ligatures temporarily held in place by turning them over the steel tube that has been placed on the archwire as a space maintainer. (c’) The pigtail ligatures are shortened and formed into hooks, as close as possible to the sutured flap, and elastic ties apply traction to the archwire. Note that the lateral incisor is being drawn downwards through attached gingiva, rather than through the oral mucosa of the stomium, which was later sutured closed. (c’) A year later, the teeth have been actively erupted, the central incisor has been brought to abut the midline and the lateral incisor lies horizontally, with its apex distal to that of the canine, whose root lies very buccally prominent. (d’–f’) These clinical photographs show the extreme degree of root torque that is needed to align the lateral incisor, canine and first premolar, and the auxiliaries that were used to achieve this. There is a combined orientation discrepancy between the long axes of the lateral incisor and the canine, requiring approximately 90° of aggregated reciprocal torque! (h’–j’) The final result shows excellent alignment, axial orientations and occlusion, with only a mild degree of lateral incisor and canine clinical crown elongation. The periodontal condition is good, and an experienced practitioner would be hard-pressed to guess that these teeth had even been impacted, let alone affected to the degree that the initial films show. (k’) At two years post-treatment, periapical radiographs of the anterior teeth show a lack of bony support around the two previously affected incisors, a dilacerate central incisor root and obliteration of the pulp of the canine. All other periodontal parameters were normal.

Rescuing Teeth Impacted in Dentigerous Cysts  311 

(e)

(f)

(g)

(h) Fig. 11.11  (Continued )

(i)

(j)

(k)

(l)

(m)

(n)

(o) Fig. 11.11  (Continued )

Rescuing Teeth Impacted in Dentigerous Cysts  313 

(p)

(q)

(r)

(s)

(t)

(u)

Fig. 11.11  (Continued )

314  Orthodontic Treatment of Impacted Teeth

(v)

(w)

(x)

(y)

(z)

(a')

(b')

(c')

Fig. 11.11  (Continued )

Rescuing Teeth Impacted in Dentigerous Cysts  315 

(d')

(e')

(f')

(g')

(h')

(i')

(k')

(j') Fig. 11.11  (Continued )

316  Orthodontic Treatment of Impacted Teeth directly with the cyst (Figure 11.11m–o). The oral mucosa and cyst lining were left to heal and to become contiguous, while the hole itself remained patent. The excised tissue was sent for pathological examination and found to be innocent and consistent with benign cystic epithelium. In the 39 months that constituted the follow-up period, the widely dispersed teeth in the walls of the cyst were seen to improve their positions and to come together, indicating the disappearance of the cyst and a considerable filling-in of the bony defect (Figure 11.11p–t). At this point, a fixed orthodontic bonded appliance was placed on the erupted teeth, to act as a composite anchorage unit (Figure 11.11u, v) for the extrusion and alignment of the teeth within the former cyst cavity. The central incisor of the healthy left side of the maxilla had traversed the midline and the first premolar had partially erupted, mesiolingually rotated and mesially displaced. A simple coil spring was used after initial levelling to move the premolar distally and correct its rotation, while reciprocally moving the left central incisor back to the midline (Figure 11.11w, x). This effectively opened more than adequate space to accommodate the three impacted teeth. While this preliminary orthodontic space regaining and alignment was taking place, the lateral incisor in the floor of the former cyst area had suddenly become visible through the still patent stomium that had earlier been surgically opened to drain the cyst (Figure 11.11y). The relatively simple and minor surgical exposure of the crowns of the three teeth was then undertaken on an ambulatory basis under local anaesthetic in the Department of Oral and Maxillofacial Surgery, and small eyelets bonded in strategic positions, with twisted steel pigtail ligatures threaded into the eyelets (Figure 11.11z, a’). The surgical area was then fully closed and the pigtail ligatures were taken through the sutured edges of the flap (Figure 11.11b’). Directional elastic traction was applied between these ligatures and the main archwire (Figure 11.11c’) before the patient was released from the operatory. The elastic traction was subsequently renewed periodically until the teeth had fully erupted and been brought into approximate alignment. At that stage, sophisticated brackets of the same type used on the other teeth were substituted for the eyelets and the treatment was continued until full alignment was achieved and, it should particularly be noted, until the extreme amount of root uprighting and root torque were completed (Figure 11.11d'–k'). Orthodontic brackets have been developed over the years with the incorporation of various highly sophisticated slot angle prescriptions and ligature tie alternatives, to make them as versatile as possible in aligning, rotating, tipping, uprighting and torqueing the teeth. This has allowed the orthodontist to cater to well over 90% of cases without having to change attachments and to achieve excellent alignment, offset, tip, torque and inter-arch relationships. The prerequisites for these brackets to achieve their goal are

that they be placed in the mid-buccal position of the teeth and, at the end of the treatment, that a full-sized archwire be fully tied into them for them to realize their maximum programmed potential. When the ideal bonding site of a tooth is not accessible, the route taken by most orthodontic practitioners is to place their regular ‘straight wire’ bracket at a different site on the tooth, where it can be used to achieve some alignment and levelling. In this position, however, it cannot be used to realize the full potential of the prescription slot – a prescription that is able to perform any other type of movement with considerable accuracy and efficiency – and nor would one want it to, unless a series of complicated bends are introduced into the archwire by way of compensation. Beyond a minor degree of rotation, height discrepancy and ectopia, it is difficult to ligate the archwire into the bracket, and this stage of the treatment becomes very clumsy and inefficient, slowing down the momentum of the desired correction. It is obvious that brackets cannot be placed in their ideal positions on teeth which are severely rotated or partially erupted; nor can an archwire be easily and usefully tied into the bracket of a tooth which is grossly tipped or ectopically placed. In these cases, an initial temporary attachment should be preferred, or the archwire modified with a series of offsets and loops.

Eyelets and brackets In Chapter 4, we discussed the use of eyelets in relation to impacted and markedly displaced teeth. Using eyelets as initial attachments on the impacted teeth provides for superior management of the gross movements of the teeth, movements that are needed in the early stages of their resolution. It simplifies ligation of teeth in the most extreme positions of displacement in these situations and makes directional traction much more efficient. Threading a super-elastic auxiliary archwire through one and sometimes a pair of eyelets makes large-scale extrusion, tipping, rotation and uprighting movements extremely easy over a broad amplitude of positional dislocation. Within a relatively few short appointments, the formerly impacted teeth may be brought into general alignment over large distances in this context, to a point prior to the detailing and finishing procedures that will be necessary to achieve excellence. At this stage, in the patient who is being treated for the resolution of a dentigerous cyst, new radiographs of the involved teeth should be evaluated to check the form of their roots. We have noted above that teeth which have developed their roots while being displaced by the progressive enlargement of a dentigerous cyst are likely to have abnormal root form. The discovery of this phenomenon in a particular tooth or teeth will obviously modify the amount and direction of root movement that is indicated for the patient. Once this has been determined, the eyelets should

Rescuing Teeth Impacted in Dentigerous Cysts  317  be removed and regular orthodontic brackets, of the type used on the other teeth, should be substituted in preparation for the final stage of treatment aimed at the fine-tuning of the alignment and occlusion of the dentition. In essence, the eyelets are responsible for the resolution of the impaction and the gross movement of bringing the severely displaced teeth into the orthodontic ‘ball park’. When all that remains to be performed are the final millimetre or two of levelling and crown alignment, the extensive root uprighting and torque, and the additional few degrees of tooth rotation, this can only be achieved with a sophisticated bracket system, which should then be applied. Alternative surgical approaches are presently in use in many centres, particularly where the orthodontist is not involved in the decision-making process. Perhaps the most common approach has been described by two oral surgeons in a study of 40 dentigerous cyst cases [4]. Apart from one instance, all their cases were treated by enucleation. Their treatment sequence was aspiration, followed by an incisional biopsy for pathological examination. The cysts were subsequently enucleated, and extraction of the affected impacted tooth was considered to have been indicated in 34 of their 40 cases. In one isolated case, decompression was performed first and then excision of the cyst done several months later. The histopathological reports indicated only innocent diagnoses, and postsurgical bone regeneration occurred in all cases within 6–12 months. Grafts were not needed in any of the cases. In the view of these authors, ‘cyst enucleation . . . in extensive cysts will lead to loss of several teeth’ and ‘when the teeth involved with the cyst are extracted (especially in children) function, cosmetic and psychological consequences may follow’. While they mention that marsupialization is one of the treatment options, it was not the modality chosen in any of the individuals in this series of cases. Their clear preference is for ‘curative’ enucleation of the lining. As a general rule, surgeons will prefer not to run the risk of introducing infection, which could track along a stainless steel ligature wire that is ligated to an attachment on the impacted tooth, when the wound is a relatively large one. Many are uncomfortable with the idea of leaving the cyst lining in place and prefer to shell it out completely on the premise that it is pathological tissue. These two surgical concerns are addressed in the approach to treatment described in this chapter. In the first place, by virtue of the marsupialization procedure that has been performed many months earlier, the large surface area of exposed bone that would be engendered by a ‘curative enucleation of the lining’ is avoided. Instead, an epitheliallined cavity of ever-reducing size is present, with no exposure of the underlying tissues to the exterior. At the later stage, when the teeth themselves are finally exposed and attachment bonded, the exposure is extremely minimal, less than in a routine impacted tooth exposure. There are no

large wounds whatsoever in this approach and the risk of infection is insignificant. The literature reports only the rarest incidences of neoplastic change in the lining of a dentigerous cyst, and these have been cases in which the histopathological examination has been performed on excisional biopsy material taken at the time of the initial treatment of the cyst. In the present approach, a small portion of the lining is sent for microscopic examination and the patient is followed up clinically over the succeeding months until full resolution of the cyst cavity has occurred. It would appear that the chances of undiagnosed neoplastic alteration occurring in the former cystic epithelium are extremely small, probably no greater than finding it in another unrelated area of the oral mucosa. The rate with which neoplastic change might occur in a dentigerous cyst has never been investigated. An early histological study of a sample of 52 patients with widened follicles, as distinct from dentigerous cysts, around their impacted maxillary canines showed a zero incidence of neoplastic change [9]. However, there are no studies investigating neoplastic change in large samples of patients with clearly defined dentigerous cysts and as such there can be no foundation for always assuming the worst. The fact of the acceptance for publication in the dental literature of only occasional, single individual, case reports of neoplasia in these cases speaks more of typical editorial eye-catching sensationalism and, therefore, of extreme rarity. With no other information available, these articles arouse readership interest based on emotional appeal and exert an exaggerated influence on surgical decision-making. There is a great deal of highly emotive, alarmist and even incendiary input influencing the decision of which surgical route to take on the part of both the patient and the surgeon. Hence the surgeon will sleep better if he/she performs a ‘curative enucleation’ of the lining of the cyst, along with removing the tooth or teeth involved in the lesion. Legally, this degree of caution cannot be easily faulted. But clinically in some of these cases, this relatively radical surgical procedure will leave a large bony defect, which may also adversely affect the patient’s facial appearance. Bony reconstruction and implant-borne restorations will be necessary in the long term. But the clinical experience of experienced surgeons tells us that neoplastic alteration of the epithelial cyst lining is extremely rare and, although it is essential to biopsy that part of the cyst epithelium removed in establishing adequate drainage, experience in the overriding majority of these cases must justify the use of the more conservative marsupialization option whenever possible. This naturally presupposes careful radiography of the healing process and clinical follow-up of the appearance of the epithelial tissue in the ensuing months during which the lesion is resolving. By the nature of their work, surgeons do not have the same follow-up as do orthodontists. The orthodontist, on

318  Orthodontic Treatment of Impacted Teeth the other hand, maintains considerable control over frequent periodic visits. He/she will place a space maintainer, with the patient on close recall for clinical and regular radiographic examination and later for orthodontic appliance adjustment. A follow-up periapical film taken a month later should reveal rapid resolution and healing and a dramatic improvement of the position and orientation of the affected tooth. In the extremely unlikely event that the lesion becomes more sinister, the change will be seen on this film and another taken three months later. For these reasons, the parents must be told of the importance of follow-up with the argument that marsupialization surgery is simple and minimal, it will most likely save teeth, it will generate a normal ridge bony contour and cause no facial disfigurement. This is in direct contrast to enucleation surgery which is more radical, will likely necessitate the loss of tooth or teeth, create a large bony defect with possible consequent facial change and require long-term space maintenance, ridge enhancement bony procedures, implants and crowns. Conclusions In regard to the marsupialization of dentigerous and radicular cysts, the anecdotal evidence that has been presented above and from other cases treated by the author points to several important, if tentative, conclusions that may be made at this stage. These are as follows: 1. The cystic area shrinks rapidly as bone fills in behind the cyst lining, to repair the initial bony defect. 2. The teeth that have been displaced by the lesion come together within the repairing defect, their orientation improves and there are positive movements in the direction of eruption, and actual eruption may occur in some instances over time. 3. Alveolar bone regenerates around the roots of the teeth. 4. The root form of teeth impacted within cysts may be dilacerate. 5. Treated in the following protocol, there is rarely any need to extract the involved teeth, and their eventual prognosis is excellent. The following is the suggested protocol for a conservative approach to the resolution of teeth impacted within dentigerous cysts: Simple decompression surgery – marsupialization and • biopsy of the removed epithelial tissue. Awaiting bony fill-in, which will be seen by periodic • radiographic monitoring, indicated by the coming together of the teeth within the former cyst location – a year or more after the decompression, depending on the size of the lesion (Figure 11.12).

Fig. 11.12  The same patient illustrated in Figure 11.2, seen 20 months after the initial decompression surgery. This panoramic radiographic view shows the coming together of the three teeth that were grossly displaced by the cyst and some incidental improvement in the positions of the premolars on the same side.

Orthodontic aligning of the erupted teeth, levelling and • preparation of the anchor unit. Surgery to • attachments.expose impacted teeth and bond eyelet Traction to main arch with extrusion, tipping, rotation • and some root uprighting movements. Check root morphology of involved teeth. • Substituting brackets for controlled root • uprighting andstandard torqueing and finishing procedures.

References 1.  Shafer WG, Hine MK, Levy BM. Oral Pathology. Philadelphia: Saunders, 1983. 2.  Shear M. Cysts of the Oral Regions, 2nd edn. Bristol: Wright, 1983: 114–141. 3.  Archer WA. Oral Surgery, 4th edn. Philadelphia: Saunders, 1966. 4.  Motamedi MHK, Talesh KT. Management of extensive dentigerous cysts. Br Dent J 2005; 198: 203–206. 5.  Fearne J, Lee RT. Favourable spontaneous eruption of severely displaced maxillary canines with associated follicular disturbance. Br J Orthod 1988; 15: 93–98. 6.  Sain DR, Hollis WA, Togrye AR. Correction of a superiorly displaced impacted canine due to a large dentigerous cyst. Am J Orthod Dentofacial Orthop 1992; 102: 270–276. 7.  Miyawaki S, Hyomoto M, Tsubouchi J, Kirita T, Sugimura M. Eruption speed and rate of angulation change of a cyst-associated mandibular second premolar after marsupialization of a dentigerous cyst. Am J Orthod Dentofacial Orthop 1999; 116: 578–584. 8.  Becker A, Chaushu A. Healthy periodontium with bone and soft tissue regeneration following the orthodonticsurgical retrieval of teeth impacted within cysts. In Davidovitch Z, Mah J, eds. Biological Mechanisms and Craniofacial Adaptation. Boston, MA: Harvard Society for the Advancement of Orthodontics, 2004: 155–162. 9.  Olow-Nordenram M, Anneroth G. Eruption of maxillary canines. Scand J Dent Res. 1982; 90: 1−8.

12 The Anatomy of Failure

Age

322

Abnormal morphology of the impacted and adjacent teeth

322

Ankylosis and invasive cervical resorption

323

Wildly ectopic teeth

323

Incorrect positional diagnosis

327

Surgical exposure without prior orthodontic planning

330

Resorption of the root of an adjacent tooth

340

Poor anchorage

347

Inefficient appliances

351

Expert opinion and second opinions during treatment

355

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

320  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c) Fig. 12.1  (a) A pre-treatment panoramic view of a patient whose mandibular right second molar had not erupted at the completion of treatment. (b) A panoramic view of the same patient seven years later and five years after the completion of the treatment shows the mandibular right second molar impacted between the two adjacent molars. (c) A month after the surgical removal of the unerupted third molar and exposure of the impacted second molar, the second molar is erupting spontaneously. The impaction is due to the obstruction created by the distal anatomy of the first molar and the large and horizontal third molar.

There are many factors complicating the treatment of impacted teeth that are not present in routine general orthodontics. In the first place, the affected tooth is not visible, and is only imaged using clinical and radiographic aids. It thus cannot be examined for abnormality in the same manner or with the same degree of thoroughness as a normally erupted tooth. The precise, three-dimensional location of a normally erupted tooth is obvious from a clinical examination. So too is its degree of rotation, the orientation of its long axis and its relation to the erupted adjacent teeth, as well as minor flaws in the morphological features of its crown, surface imperfections in the smooth outline or colour of the enamel. Exactly what types of corrective movement its orthodontic treatment will demand can be seen by direct vision, and biomechanical planning is straightforward. These luxuries are not available when dealing with an impacted tooth. One of the most constant features of the normal growing child is the natural and spontaneous eruption of teeth. In

the deciduous dentition, this occurs between the ages of 6 months to 2.5 years and these teeth shed normally between 6 and 10 years later, to be replaced within just a few months and in rapid succession by the permanent teeth. This innate attribute is so universal that a single tooth failing to erupt, when all other factors are apparently favourable, should raise the suspicions of the discerning orthodontist. The very fact of its non-eruption raises questions as to why this should be, and the answers range from the common and the obvious to the unusual and least expected. Determining aetiology must not be looked on as a mere theoretical exercise, but rather an essential prerequisite that provides the basis for the treatment plan for each individual case. Perhaps the tooth is quite normal, but there is some local impediment blocking its path (Figures 12.1 and 12.2), or perhaps the location of the tooth germ is ectopic. Alternatively, the cause may lie in a local abnormality of the tooth follicle itself, or perhaps the patient suffers from a general pathological condition that, among other features,

The Anatomy of Failure  321 

Fig. 12.2  A cause of incisor crowding? (Courtesy of Dr N. Casap.)

adversely affects tooth eruption. Accurate positional diagnosis is often fraught with difficulty and mistakes may be made in locating the tooth – even by experts [1, 2]. As the result, a tooth in an intractable position may be thought to have a good treatment prognosis, and an inappropriate, ill-advised and ill-fated course of treatment will be prescribed. In many cases all that may be required is for space to be made and this will sometimes reawaken dormant eruptive movements in the tooth, which may then respond by improving its position and even open the window of opportunity to its spontaneous eruption, with the passage of time [3] (see Figure 6.21). At the other end of the scale, a complicated directional traction strategy may be needed to bring the tooth into its place in the arch, while avoiding the roots of adjacent teeth. This we have seen in Chapters 6 and 7 in relation to maxillary canines which are located mesial to the root of adjacent incisors or where the tooth is associated with the resorption of those roots. An open surgical exposure of the impacted tooth may close over in the succeeding days and weeks and make later attachment bonding unreliable or impossible to achieve. When bonding is performed by the surgeon as an integral task during an open or closed exposure, an attachment may be placed in an inappropriate position on the tooth surface or the pigtail ligature wire or gold chain may have been drawn through the tissues in the wrong direction for traction to resolve the impaction. Alternatively, the bond may fail and, without further surgery, suitable conditions for rebonding may be limited or unattainable (see Figure 8.10). We have seen in the preceding chapters that the successful outcome of treatment of a difficult impaction, from the orthodontic and surgical points of view, may founder in the long term because of a lack of periodontal support of the treated tooth – a situation that could have turned out very differently had certain precautions been taken in diagnosis, treatment planning, surgical exposure or biomechanics. From the foregoing, we come to appreciate that there are many different areas where opinions regarding attitudes

to treatment and where levels of expertise may vary among the three principal specialists involved with the treatment: orthodontist, oral radiologist, oral and maxillofacial surgeon. Taken from the standpoint of how to serve the best interests of our patients, it helps us to understand that communication and rapport between these specialists is of paramount importance. Given the broad spectrum of concerns that are so intimately bound up with the whole approach to this relatively limited phenomenon, it should not be surprising that the chances of error are legion, and with them the distinct likelihood of embarrassing failure. The purpose of the present chapter, therefore, is to analyse the possible causes of failure that occur from time to time in clinical practice and to group them in relation to the various aspects involved in each scenario. In a recently published study [4], the Jerusalem group collected a sample of 28 young patients for whom treatment for the resolution of their impacted canines had failed. These patients had been referred to the authors by a large number of different orthodontists individually and over a period of several years, with the intention and in the hope that the cases could be salvaged. These 28 patients had 37 failed canines in total and had been in treatment for an average of 26 months for the sample, with a range of 7−72 months, before being referred and, for 10 of these canines, surgical exposure had been performed three times! The referring orthodontists were questioned as to why they thought the case had failed and a large majority had assumed it to be due to ankylosis, while most of the others had missed diagnosing root resorption of the adjacent teeth. A few had blamed bond failure, an intractable location of the tooth and failure to adequately surgically expose the impacted tooth. These cases were then re-evaluated, many with the help of a CBCT examination and re-treated in accordance with the new findings. The outcome saw 28 of the original 37 failed teeth successfully aligned in the dental arch. Of the remaining cases, two individuals had refused the revised treatment. Of the seven canines with confirmed ankylosis, three were successfully realigned following surgical luxation. In their conclusions, the authors of this study noted that there are many aspects and minutiae in the treatment of impacted maxillary canine that may cause the treatment to founder. They specifically had the following comments to make: 1. Diagnosis of the location of the tooth and its immediate relationship with the roots of the adjacent teeth is generally treated with cavalier and often negligent simplicity, even though modern technology has provided the tools to achieve this with great accuracy in all three dimensions. 2. With inappropriate positional diagnosis, it follows that traction will be applied in the wrong direction.

322  Orthodontic Treatment of Impacted Teeth 3. A lack of appreciation of the considerable anchorage requirements of the case and the need to exploit all available means of enhancing them will inevitably lead to inefficient mechano-therapy and unnecessarily longer treatment. 4. Ankylosis might have afflicted the impacted tooth either a priori or as the result of the earlier surgical or orthodontic manoeuvres.

Age In Chapter 6, we referred to the fact that the chances for orthodontic traction having a positive effect on an impacted tooth are extremely high in the young patient, but that with advancing age, notably in the over-thirties, the risk of nonmovement becomes quite significant [5]. By contrast, the compliance factor among adults undergoing orthodontic treatment towards the relatively undemanding tasks which are in the patient’s realm of responsibility within the treatment protocol (i.e. maintaining a high level of oral hygiene, attending pre-arranged treatment visits, taking proper care of the appliances, placing elastics), is usually considerably better. Thus, while tissue response to orthodontic forces in the child is very positive, the endeavour may be more likely to founder due to a lack of compliance. In the adult, the ravages of time will often be evidenced by a loss of attachment and bone support, which have been due to large measure by chronic inflammation. But once these factors have been brought under control by appropriate periodontal treatment, routine orthodontic treatment may be recommended with considerable confidence and with a high degree of predictability. But this is true only in regard to the root of a tooth. For the unerupted crown of the tooth this situation may be quite different, since the dental follicle undergoes deterioration in time and direct contact between tooth enamel and the encroaching bony tissues may occur, which will effectively eliminate the orthodontic therapeutic option. Since this phenomenon is agerelated, it will rarely be encountered in the young patient, but must be a factor to be considered in planning the treatment of an adult, particularly in the over-thirties age group.

Abnormal morphology of the impacted and adjacent teeth Unusually large or small teeth and abnormalities of crown form or root configuration, regardless of their cause, are findings which may affect the decision whether or not to attempt to bring the tooth into the arch. Uncomplicated abnormal morphology presents no impediment to orthodontic movement, since the roots of the teeth are generally invested with normal periodontal tissues and their crowns protected within a normal follicle in which they developed, however abnormally. The unusual form of the teeth may affect the position of the centre of rotation and the centre of resistance, which in turn may affect the direction that

orthodontic traction will need to be applied. However, the teeth will respond. In many of these cases, as discussed in Chapter 5 with reference to dilacerate incisors, the orthodontic/surgical modality of treatment may provide an optimal result in aligning these abnormal teeth and in carrying the young patient through the years of childhood and adolescent growth, during which time prosthetic/implant substitution is generally contraindicated. Minor artificial modifications in crown or root form may be necessary during this time but, with this treatment modality, the child is free of iatrogenic, periodontal disease-producing or caries-generating prosthetic devices, when the dentition is at its most vulnerable. At least as important, alveolar bone in the area proliferates quite normally with the resolution of the impaction and maintains its height throughout growth, in parallel with the other teeth. It would be a serious mistake to indiscriminately extract these teeth simply because of a diagnosis of morphological abnormality, and the practitioner is strongly advised to consider all the alternatives before recommending extraction. Fixed bridges and implants have a limited life expectancy, and failure may occur much earlier in some instances. This, together with the atrophy of alveolar bone in the immediate area, which inevitably occurs following an extraction, must be considered to be a failure to utilize naturally occurring and available raw material (i.e. the imperfectly formed tooth). Nevertheless, there are cases in which the location of the dilacerations and the degree of the tooth’s distortion leave little option but extraction (Figure 12.3). Rather than the canine itself being the cause of the problem, it may occasionally occur that the root morphology of the first premolar is the hidden impediment. The adjacent first premolar normally erupts before the canine and has a buccal and a palatal root, which may sometimes be fused. These roots, particularly the palatal one, may develop in the direct eruption path of the canine which may happen when the premolar erupts with a distal crown tip or when the tooth is rotated mesio-buccally. The root itself may be deformed and exhibit a mesially directed dilaceration of its root apex, as has been described in Chapter 6 (Fig. 6.1c, d). In plane film radiography, the individual roots of the premolar are sometimes not possible to distinguish and superimposition on the canine leaves the bucco-lingual interrelation of the two teeth difficult to ascertain. CBCT imaging of these cases will often clarify the problem and permit the determination of a suitable direction for the application of traction to resolve it. In the case illustrated in Figure 6.1, the root orientation of the premolar must be over-uprighted in a distal direction and then the tooth should be rotated mesio-palatally to free the canine from interference. Once the canine has been brought into alignment, the first premolar may then be re-uprighted and re-rotated into a more optimal position, having due care to avoid a clash of roots in the final analysis.

The Anatomy of Failure  323 

(a)

(b)

(c)

(d)

(e) Fig. 12.3  A 15-year-old female presented with a dilacerate but erupted right maxillary central incisor. (a) The initial malalignment. (b) Following alignment and levelling, the root apex can be seen to be pointing labially under a thin cover of overlying oral mucosa. (c) When the flap was raised over the area, with the view to perform an apicoectomy, it was seen that there was no labial bone covering the short and malformed root. (d) The root apex was trimmed back and a retrograde filling placed. (e) At the two-month follow-up visit, the root apex had fenestrated the oral mucosa and the tooth was extracted.

Ankylosis and invasive cervical resorption These two phenomena are difficult to diagnose in their early stages, even with good radiographic technique. The presence of either will result in failure of the affected tooth to respond to the applied orthodontic force because of a loss of integrity of the normal periodontal tissue in one or more, often very small, locations on the root surface

(Figures 12.4–12.7). This has been discussed fully in Chapter 7 (Figures 7.11–7.13).

Wildly ectopic teeth Although wildly ectopic teeth are seen extremely rarely, there would appear to be few limitations on where teeth may be found in the tooth-bearing areas and beyond, in

324  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

Fig. 12.4  Invasive cervical resorption. (a) The orthodontic attempt to erupt the left central incisor had failed and the tooth was extracted. A close look at the distal side of the cervical area of the tooth shows a defective outline. (b, c) A large area of inflammatory soft tissue in the cervical area of the extracted tooth on the distal side. (d, e) With the soft tissue removed with a scaler, the full extent of the erosive lesion can be seen.

(a) (b)

(c) (d) Fig. 12.5  Invasive cervical resorption. (a) A panoramic view shows a deeply situated mandibular left second premolar, which had not responded to extraction of the adjacent first premolar. (b) The treatment plan involved the extraction of a premolar in each of the other quadrants and placement of a fixed appliance. (c) The premolar was exposed and an attachment bonded. Traction was applied immediately. (d) The left side, seen one month post-surgery. (e) Despite the application of light forces, the impacted tooth did not respond and the adjacent teeth had intruded. (f, g) These light forces, over a long period, had generated a left-side open bite and a strong cant of the occlusal plane. (h) A new periapical view at this stage showed a radiolucent area within the crown of the tooth, which turned out to be advanced invasive cervical resorption on the lingual side, which was not seen at the time of surgery, although it was obvious on the original panoramic view and had been overlooked! The original location of the premolar, with its developing apex on the lower border of the mandible and with no obstruction superiorly, had raised the suspicion of the author at the outset.

The Anatomy of Failure  325 

(e)

(f)

(g) (h) Fig. 12.5  (Continued )

Fig. 12.6  This patient was seen by the oral surgeon and referred for an orthodontic opinion as to which tooth should be extracted. The surgeon suggested the following options: (a) to extract the third molar, expose the first and second molars, drain the cyst, and leave the remainder to the orthodontist; (b) to extract the second molar, together with cyst enucleation, and to free the first molar to erupt; or (c) to extract the first molar, curette the cyst lining, and then upright the second and third molars. Are all these equal possibilities? The missing element is the diagnosis. The first molar was infra-occluded due to invasive cervical resorption (arrow) and must therefore be the tooth to be sacrificed, together with defusing of the cyst. The possibility of pathologic fracture of the mandible was known and accepted, and the molar therefore removed piecemeal. Enucleation of the cyst was impossible, due to poor access and the danger of damaging the second molar – it was marsupialized. An attachment was placed on the second molar and occlusally directed traction was applied from a zygomatic arch implant.

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 12.7  Patient seen by the author in consultation, three years after surgical exposure and failure to resolve the bilateral canine impaction. (a) Intra-oral view at consultation: patient complaining of an open bite. (b) Intra-oral view from the initial treatment records, five years earlier. (c) Anterior section of panoramic view taken prior to surgical exposure showing canines with no apparent pathological involvement. (d) Periapical view taken at time of consultation visit shows aggressive cervical root resorption on the distal aspect of the root of the left canine. (e) A buccal three-dimensional view from the CBCT series shows the lesion extending from the distal to lingual sides of the root. (f) A lingual three-dimensional view from the CBCT series shows the lesion extending from the distal to lingual sides of the root. (g) A single axial (horizontal) slice from the CBCT to show the right canine lying horizontally above the roots of the incisors. The cross-section of the left canine shows a distinct break in the continuity of the root on the distal side. It is possible to discern the narrow pulp chamber outlined by more radiolucent predentine and the resorbed area of root around it. (h) Two transaxial (vertical) slices from the CBCT show the palatal point of entry of the resorption process and its mushrooming extension inwards.

The Anatomy of Failure  327 

(g)

(h)

Fig. 12.7  (Continued )

Incorrect positional diagnosis

Fig. 12.8  A ‘condylar’ third molar complete with dentigerous cyst. (Courtesy of Dr A. Renert.)

remote areas of the jaws generally. Several of these are worth exhibiting here, for curiosity value only (Figures 12.8–12.12). Satisfactory imaging of many of these teeth may be achieved with the use of straightforward plane film radiography because of the wide separation of these teeth from the remainder of the dentition. There may be little or no added value in the use of CBCT in many of these cases. As with teeth of abnormal form, their surrounding tissues are generally quite normal and the potential that they may have for responding to the application of orthodontic forces may be excellent. Nevertheless, the question that needs to be answered is whether the estimated length of time involved in their treatment and the periodontal prognosis of the outcome are sufficiently favourable to make the orthodontic/surgical modality superior to other therapeutic options. The answer will usually lean towards extraction or, occasionally, towards leaving the tooth untreated because of difficulty and possible complications in extraction.

Inadequate or inappropriate use of imaging techniques may sometimes give the operator a false impression of the position of an unerupted tooth. Often, films exist, but are simply not considered as contributory because positional diagnosis was not the original intention for obtaining the particular view concerned. As a routine, most orthodontists insist that the initial records of all their new patients include a panoramic, lateral cephalogram and sometimes a posteroanterior cephalogram. The panoramic films are used to ensure the presence of all the teeth and to register their state of development, and the cephalograms are studied and evaluated by the measurement of angles and distances between anatomic and dental structures. An undetermined but significant proportion of our orthodontic and surgical colleagues fail to exploit all the information that is contained in these films, particularly in regard to threedimensional diagnosis of impacted tooth position (Figure 12.13). The patient is then further irradiated in the search of information already available. We have discussed wildly ectopic teeth as one of the factors that a patient may present to us for which the orthodontic/surgical modality may not provide the best treatment solution. However, to arrive at this decision a careful analysis of the orientation of the tooth in its ectopic location needs to be made, and this must be done by the orthodontist. One of the most important guiding principles relates to the accurate diagnosis of the location of the root apex of the aberrant tooth. If the apex is in a fairly normal position, the prognosis will generally be fairly good, because the main part of the treatment for that tooth will involve a tipping movement, which is easy to apply and rapid in its response. However, whenever the root apex is also displaced, particularly when it is located on the same side of the arch as the displaced crown, very considerable

328  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c) Fig. 12.9  (a–c) Panoramic, lateral cephalometric, and occlusal views of a mandibular left impacted canine crossing the midline and exactly at right-angles to the mid-palatal and antero-posterior planes (arrows). The direction of the X-ray for the cephalogram is in the long axis of the tooth and depicts it in cross-section.

(a) (b) Fig. 12.10  (a, b) The maxillary parallel of Figure 12.9. (Courtesy of Dr M. Barzel.)

(b)

(a) Fig. 12.11  (a, b) Bilateral ‘high-flying’ maxillary canines. (Courtesy of Dr P. Teper-Adler.)

(a)

(b)

(c) Fig. 12.12  An ‘eye-for-an-eye’ tooth. (Courtesy of Dr M. King.) (a, b) The panoramic and lateral cephalometric views of this young female patient show the left maxillary canine (arrows) to be in close relation with the floor of the orbit of that side. It was important to establish its exact location in the three planes of space and whether further ‘eruptive’ movements in the present direction would threaten the eye. (c–e) Three-dimensional computerized tomographic views of the tooth provide accurate positional information with which to consult the ophthalmologist.

330  Orthodontic Treatment of Impacted Teeth

(d)

(e)

Fig. 12.12  (Continued )

torqueing and/or uprighting movement will be required. Root movements are largely impossible to accomplish before the bonded attachment on the crown of the tooth has reached and been ligated into the main archwire. Therefore, during the mechano-therapy employed to bring the tooth to the line of the arch, the orientation of the impacted tooth will generally change unfavourably to cause the root to bulge the palatal or buccal mucosa to an exaggerated degree and lead to a dehiscence of its cervical area. The severity of this bulging and, by extension, its dehiscence will depend on the distance that separates the root apex from the general line of the arch – its normal place. In the more extreme cases, this will require a disagreeably wide angle of torque correction (Figure 12.14), which will translate into many months or years of treatment, and the periodontal implications of the treated result will often leave much to be desired. In Chapter 8, the buccally impacted maxillary canine with mesial displacement was highlighted, and it was explained why its positional diagnosis was particularly prone to error when using plane film radiography. When these teeth are more severely mesially displaced, a periapical or anterior occlusal radiographic view will depict them superimposed on the mesial aspect of the root of the lateral incisor and on the distal aspect of the root of the central incisor. Being sited in the depression between the two roots, it may not produce an adequately convincing differential overlap of the incisors that is needed for the lateral tube shift method in determining its labio-lingual positional diagnosis. Because of the angle of the central ray from the periapical or anterior occlusal vantage points, this labially displaced tooth will appear to be more occlusal than its true position, superimposing on the middle portion of the roots of the adjacent teeth. However, on a panoramic film, the relative height of the tooth will show it to be more apically superimposed on the roots of the incisors (for a description

of vertical tube shift, see Chapter 2). Given the frequency with which misdiagnosis appears to be made in these cases, the attempt to surgically expose a labially impacted canine may be mistakenly made from the palatal side! The surgeon may then report the case as having been a very difficult one or that the tooth was impossible to find (Figure 12.15) – this would be the good news! A more persistent surgeon might succeed in exposing it, but fail to bond an attachment to it, or perhaps the lateral incisor may be subject to a totally superfluous and iatrogenic vital apicoectomy on the way (Figure 12.16)! Compounding the problem, the orthodontist may follow the surgeon’s lead by attempting to draw the tooth from the palatal side, which may then result in one of three possible ill-fated outcomes: (a) the tooth will not move at all, (b) it may cause resorption of the labial and interproximal aspects of the incisor roots, against which it is being drawn, or (c) it may erupt through the palatal mucosa, with the orientation of its strongly tipped long axis clearly indicating that the root apex is on the labial side (Figure 12.17)!

Surgical exposure without prior orthodontic planning For the surgical approach to most impacted canines, the essential design and extent of a palatal surgical flap in a closed eruption case differ very little, regardless of the position of the canine. The same is true of those canines to be exposed in an open ‘window’ technique. For this reason, and once the surgeon knows that the tooth is on the palatal side, he/she may consider further radiographic refinement of the positional diagnosis to be unnecessary and will simply rely on the two, very conveniently acquired, periapical views used in Clark’s tube shift method. After all, and in contrast to the needs of the orthodontist, knowing the position of the root apex and orientation of the root portion

The Anatomy of Failure  331 

(a) (b)

(d)

(c) Fig. 12.13  A case of mistaken identity. (Courtesy of Dr N. Shpack.) (a) An occlusal view of a patient with an unerupted maxillary left central incisor. (b) The anterior occlusal view of the maxilla shows the typical appearance of a classical dilacerate central incisor, with the crown viewed in its long axis and the apical portion of the root pointing superiorly. (c) The cephalogram confirms the position of the crown high up and labial, adjacent to the root of the nose. (d) Excessive space had been deliberately made and a rectangular archwire placed, ready to be used as the base from which to apply traction to the impacted tooth. After the second surgical exposure an elastic ligature was tied to the labial archwire. However, the site of the first surgical exposure was mistaken and the decision was made through inadequate attention being given to information that was readily available from the radiographs. The exposed root apex of the tooth (arrow) can be clearly seen in the mid-palate. This tooth was subsequently extracted.

(a)

(b)

Fig. 12.14  (a) A severely displaced (group 4) canine crown has been brought to the line of the arch and needs much labial root torque. Considering the length of the root of a canine, its apex must be moved buccally through approximately 10 mm of alveolar bone! (b) Root torque was achieved with a torqueing auxiliary and took 17 months to complete. (Courtesy of Professor S. Chaushu.)

(a)

(c)

(b)

(d)

Fig. 12.15  A transfer case following failure of the surgeon to find the impacted canine one year into orthodontic treatment. (a–c) Good alignment had been achieved by the previous practitioner, but all potential clinical signs of canine location were eradicated. (d) A palatal approach had been chosen for the surgical exposure. The canine was not found. This is the residual soft tissue and bony defects can be clearly seen. (e, f) Intra-oral views taken from the original pretreatment records show labial tipping of the crown of the left maxillary central incisor and palatal tipping of its root – an indication that the canine is on the labial side of the incisor root. (g, h) The anterior section of the original panoramic view and an anterior occlusal view show differing levels of superimposition of the canine crown over the incisor root. The vertical tube shift method confirms the diagnosis of a labially displaced canine. (i, j) A vertical (paraxial) cut and a three-dimensional view from the newly ordered CBCT to show the labial position of the canine. (k) Surgical access to the canine was simple and shows the canine crown to be sited between the roots of the two central incisors. (l) The full flap has been sutured back in place. The pigtail ligature exits through the flap opposite the tooth. Note the horizontal passive position of the auxiliary arch. (m) The horizontal loop of the auxiliary arch is flexed vertically upwards and a little mesially to be engaged by the pigtail ligature and to impart a labially direct force with a distal component in order to circumvent the central incisor root. (n–r) Intra-oral views of the case 2.3 years post-treatment. The clinical crown is slightly elongated and the palatal view shows the central incisor defect. There is no difference between the appearance and clinical condition of right and left canine. (s, t) Anterior portion of panoramic film and a periapical view, 2.3 years post-treatment.

The Anatomy of Failure  333 

(e) (f)

(g)

(h)

(j)

(i) Fig. 12.15  (Continued )

334  Orthodontic Treatment of Impacted Teeth

(k)

(m) Fig. 12.15  (Continued )

(l)

The Anatomy of Failure  335 

(n)

(o)

(p)

(q)

(r)

(s)

(t) Fig. 12.15  (Continued )

336  Orthodontic Treatment of Impacted Teeth

(a) (c)

(d)

(b) Fig. 12.16  A miscarriage of justice! (a) Two adjacent views from the initial periapical survey radiographs. Using the buccal object rule, the right maxillary canine is labial to the lateral incisor root. (b) The initial lateral cephalogram shows both canines to be labial to the incisor roots. (c) A panoramic film taken seven months post-surgery. Exposure was mistakenly performed from the palatal side (!) and a button bonded to the inferior (anatomically palatal) aspect of the canine. Surgical access was ‘very difficult’. The lateral incisor has a shortened root – the immediately pre- and post-surgical periapical radiographs were ‘lost’. (d) Months later, the surgeon extracted the canine (!), and endodontic treatment of the incisor was prescribed in order ‘to stop further root resorption’. Subsequently the lateral incisor was extracted because it was considered to have a poor prognosis and implants placed to replace the missing teeth. The orthodontist was successfully sued by the patient for negligence ‘for having caused the entire problem’.

The Anatomy of Failure  337 

(a) (b)

(c)

(d)

(e) Fig. 12.17  Exposed on the wrong side. (a, b) Clinical intra-oral views show a strongly proclined lateral incisor (i.e. the root is strongly palatally oriented). (c, d) The panoramic and lateral cephalometric views show the canine to be sited between the incisor roots. Combining the clinical image of lateral incisor orientation with that seen on the cephalogram places the canine labial to the lateral incisor root. (e) Surgical access was attempted from the palatal side, despite the fact that much tissue was removed, the impacted canine was very difficult to find (!). An attachment was placed by the surgeon and the orthodontist applied traction from the palatal side. The canine is seen here having been drawn from the labial side, between roots of the central and lateral incisors, and erupted into the palate! There is a severe periodontal defect on the lateral incisor. The lateral incisor and canine were subsequently extracted and the case completed with implants and crowns.

338  Orthodontic Treatment of Impacted Teeth is less crucial for the surgeon, who has only to locate the crown of the tooth in order to approach it with surgical precision. The palatal canine is often palpable in the palate and, when the flap is reflected, the position of the canine is usually self-evident by the manner in which its crypt bulges the bone overlying it. While this modus operandi is shared by a large number of surgeons, it does not fully take into account those canines in group 3, which are to be found higher up and whose position may not be obvious after initial flap reflection. Thus, when surgical exposure is attempted with merely a pair of periapical views to hand, much surgical rummaging in the palatal bone may be necessary before the exact location of the canine crown is found. The intention may be to perform an open exposure and to maintain the opening with the placement of a pack in the hope that the impacted tooth will oblige and erupt spontaneously. In the more favourable cases this will take

(a)

many months, but there is a distinct possibility that the tooth will not erupt, and access to it may have become severely limited by palatal soft tissue overgrowth in the interim. In due time, a clinical and radiographic reassessment may show little or no progress, and the conclusion reached, in retrospect, might well be that perhaps the earlier procedure had been too conservative. A second attempt at surgical exposure may be advised, this time with a more radical bone-clearing procedure, a wider opening and a larger pack. This may or may not finally elicit the eruption of the impacted canine. However, under the most favourable circumstances, and even taking into consideration the alveolar bone that will undoubtedly be regenerated along with the eruption process, the finally erupted and aligned tooth will suffer from a compromised bone support and a very long clinical crown, with a good section of the exposed cervical third of its root. This will be accompanied by a similarly compromised condition of the palatal surface of the root of the neighbouring incisor (Figure 12.18).

(c)

(b)

(d) Fig. 12.18  Three failed surgical interventions. (a–d) The intra-oral photographic records show the missing deciduous canines (extracted during the first procedure) and severe soft tissue and bony defects on the palatal sides of the lateral incisors, following three ‘open-and-pack’ interventions, over a three-year period. Neither canine had shown any signs of erupting and the periodontal prognosis of the lateral incisors was considered to be poor. (e) A periapical view shows the canines to be associated with resorption of the incisor roots. (f–i) The case was treated as an extraction case, with removal of the periodontally involved lateral incisors, and compensated by first premolars in the lower jaw.

The Anatomy of Failure  339 

(f)

(g)

(e)

(i)

(h) Fig. 12.18  (Continued )

340  Orthodontic Treatment of Impacted Teeth It seems clear that the choice in these situations is difficult. On the one hand, we seek to make a net gain to avoid early active orthodontic intervention by substituting it with an extended surgical alternative. But in so doing, we undertake to bring about a spontaneous eruption of the impacted canine, using a surgical procedure that will compromise the final outcome of the overall treatment of the tooth, in terms of its final periodontal condition. At the same time, we must not forget that an integral part of this deal is that we run the risk that the tooth will still not respond. There are no published figures or available evidence to indicate what degree of reliability may be attributed to this method that may justify its routine use in generating spontaneous eruption, thus to overcome our natural and healthy reserve regarding its efficacy in a sufficient proportion of cases. By contrast, the use of an orthodontic force applied from a suitable auxiliary, with an appropriate direction, range of activity and energy level, must accord the treatment a much greater level of reliability and the possibility of limiting the surgical exposure to the least damaging of the surrounding structures, both directly and indirectly. By taking this proactive stance and with proper management, therefore, the chances of failure must be very considerably reduced.

Resorption of the root of an adjacent tooth Chapter 7 is devoted in its entirety to this subject. It is emphasized that the occurrence of this phenomenon in the incisor area is much more common (66.7% of adjacent lateral incisors and 11.1% of adjacent central incisors) than once thought [6] and, in its severest form, it develops rapidly and may irretrievably destroy much of the root of an adjacent central or lateral incisor in a relatively short time. The young patient with a mixed dentition may be seen on a regular basis, watching the development of the early malocclusion in anticipation of starting the orthodontic treatment in the full permanent dentition. Even with yearly radiographic monitoring of the immediate area, resorption may cause much root shortening in the intervening months before it comes to the attention of the orthodontist (Figure 12.19). In these cases, therefore, suspicious positioning of an unerupted canine vis-à-vis the lateral incisor root should encourage the orthodontist to recommend a closer followup procedure. A single periapical view (not a panoramic view) taken 4–6 months after an initial base-line film should show the presence or absence of downward eruption progress of the canine, and comparison should be made with its antimere. A lack of progress, strong overlap of the incisor roots or alteration in root form or length should be treated with suspicion. When the condition is mild, traction on the impacted tooth will distance it from the resorbing area and the resorption will effectively stop [7]. However, when the resorption has become extensive, accurate relative posi-

tional diagnosis of the impacted canine and the affected root end must be established for two reasons: the exact direction that traction must take needs to be determined; and on the basis of this, the site of the surgical exposure will be chosen such that the attachment is placed on a surface that faces the direction of future traction. Exposure should be as conservative as possible, sufficient only to accept the full base of a small attachment, while haemostasis is maintained. Meticulous closure of the surgical flap is then performed. Failure to observe these precautions will lead to failure in one or more aspects of the treatment. The application of orthodontic force to the impacted canine in an illdetermined direction vis-à-vis the resorbing root end may bring the two in closer contact and thereby encourage further resorption (Figures 12.20 and 12.21). An open surgical exposure in this situation and the clearance of tissue around the crown of the tooth, aimed at freeing the crown from all potential contact with bone, are to be avoided. Either of these two procedures will risk exposing the resorption front at the root face to the oral environment, which will lead to the devitalization of the incisor and further endanger its viability, whether or not a surgical pack has been placed. In the case illustrated in Figure 12.22, the influence of the unerupted canines in producing root resorption of the lateral incisor root was not apparent in the initial panoramic view taken at 11 years of age. A repeat film taken two years later, immediately prior to the commencement of treatment for the patients class 3 malocclusion, showed oblique distal resorption of the roots of both lateral incisors, clearly in association with the proximity of the unerupted canines. On the other hand, the left central incisor had lost almost half its root length due to resorption from no obvious cause, since the unerupted canine was quite distant from it. Orthodontic treatment was begun and, before adequate space was provided in the arch, the left canine was exposed with traction being applied directly to the labial archwire. From that height, this caused the canine to move down and directly towards the root of the lateral incisor. The followup radiograph showed the resultant severe resorption of the lateral incisor root. At this point, the patient was referred to the author for continuation of treatment and, on the first visit, an auxiliary labial arch was placed to change the direction of the traction to the labial. The rest of the treatment was completed with the now buccally displaced canine remaining ‘in limbo’ until space became available for its alignment. Root uprighting and torqueing procedures were avoided and the treatment was completed with simple levelling and aligning movement only and in a very short time period. At 17 years of age, the follow-up radiograph, taken one year after bonded splints had been placed at the end of treatment, revealed severe resorption of the roots of the

The Anatomy of Failure  341 

(a)

(c)

(d)

(b)

(e) Fig. 12.19  The bucco-lingual blind spot in the pre-computerized tomography era. (a) The pre-treatment panoramic film shows undoubted root resorption, but a continuation of the root under the superimposition of the canine. (b) Following careful surgical exposure and orthodontic treatment, the canine is distanced from its intimate relationship with the root of the incisor, to reveal an area of root resorption at and just apical to the CEJ. Because of the danger of exposure of this area to the oral environment, the patient was referred for endodontic treatment of this tooth. (c) Obturating the canal with root canal filling material proved impossible due to obvious lack of a wall to the pulp chamber. The tooth was extracted. (d, e) Views of the extracted tooth from the labial and mesial sides show a severe longitudinal resorption of the entire labial side of the root of the tooth, involving the pulp. This was not possible to diagnose sufficiently well from the radiographs in hand, and ill-advised treatment was undertaken which, in today’s world of CBCT, would have been avoided.

342  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

Fig. 12.20  A canine that resisted applied traction due to inappropriate directional traction. Treatment was begun before accurate positional diagnosis had been made. (a, b) Cone beam tomography presents two aspects from the labial side in a three-dimensional reconstruction. The canine is mesial and labial to the lateral incisor root, which is almost horizontally displaced. The crown tip of the canine appears to be in a resorption trough in the lateral incisor root. It is being inappropriately pulled labially and inferiorly, against the cervical part of the root of the incisor. (c, d) The two views from the palatal side show that most of the incisor root has disappeared and that only a thin sliver of its palatal side remains. Further traction to the labial archwire will almost certainly result in total root resorption. The patient would have been better served by the canine being drawn labially and superiorly, using an auxiliary labial archwire, as seen in Figure 12.16m.

other three maxillary incisors, having lost between one half and two-thirds of their initial root length. The left lateral incisor had lost almost its entire root but, with the splint in place, there was no obvious mobility. With the cessation of orthodontic movement, it is estimated that further resorption will not occur and it is hoped the patient may look forward to several years of stability before artificial replacements become necessary [8]. In stark contrast, none of the other teeth in the mouth were affected by root resorption! This raises an interesting point. On the one hand, resorption of the root of the tooth immediately adjacent to an impacted canine is well known and the effect is clearly a local one. On the other hand, the fact that there are cases in which there may be generalized resorption of the roots of all the teeth either with or without orthodontic treatment has also been extensively documented and its aetiology has been variously ascribed to genetic, humoral, hormonal or idiopathic factors. It is therefore an enigma,

as seen in this case, that three incisor teeth with no obvious proximity to the impacted canine are resorbed to more or less the same degree as the immediately adjacent lateral incisor, while the remainder of the dentition is totally unaffected. Iatrogenic damage may also be inflicted because of inadequate attention to detail and specifically to an incomplete examination of the diagnostic radiographic material. It was pointed out in Chapter 6 that a displaced lateral incisor is usually due to the proximity and angulation of an adjacent impacted canine. Reopening space with simple mechanics brings the root of the incisor into direct contact with the unerupted crown of the canine. When the angle between the long axes of the two teeth is small, this will often bring about improvement in the angulation of the impacted tooth and subsequent spontaneous eruption, as has been pointed out by other workers [9−11]. However, when the angle of orientation of the teeth approaches 90°, then

The Anatomy of Failure  343 

a

b Sept 1998

Jan 1997

c Clinical views in Oct 1998

d e Fig. 12.21  A transfer case first seen by the author in October 1999. The patient spent eight months in Jerusalem during her father’s sabbatical leave. Accompanying radiographic records were received as follows. (a) Anterior portion of initial panoramic view (January 1997) at commencement of treatment, shows bilateral maxillary canine impaction and severe resorption of all four incisor roots. (b) Follow-up view (September 1998) taken after alignment, levelling and space opening, shows improvement in position of right canine and worsening position of left canine, with considerable additional resorption of the roots. Surgical exposure and attachment bonding was performed at this time. (c) The clinical condition at the patient’s first visit in October 1999 shows a palatal arch soldered to molar and premolar bands and a sectional arch linking the incisors only. The right canine had erupted with its palatal eyelet attachment in place. The ligature wire attached to the Edgewise bracket on the unerupted left canine is visible exiting the palatal mucosa and a Ballista spring is present, tied into molar and premolar brackets. The following are signs of failing anchorage: the burrowing of the ballista into the palatal mucosa, intrusion of the left premolar, extrusion of the incisors. (d) From the newly commissioned CBCT, a paraxial cut shows the severity of the resorption of the root of the central incisor and the location of the canine tip immediately superior to the resorbed root end. (e) An oblique occlusal three-dimensional view of the palatal side of the left incisor area shows how the canine crown is immediately above the resorbed root end. The vertically directed traction force has clearly extruded the incisors (all four are linked by the sectional archwire), it has largely resisted the force of the ballista, causing it to burrow into the mucosa and brought about the infra-occlusion of the premolar. Additionally, it has aggravated the resorption of the incisor roots. (f) Traction force was directed posteriorly and laterally to a transpalatal arch with soldered loops in November 1999. (g) The canine was drawn away from the incisor root and erupted in the mid-palate in March 1999. (h) The bonded bracket on the palatal side of the canine was substituted with an eyelet on the labial side in May 1999 and drawn towards its place in the arch, while a coil spring was used to reopen space by moving the four incisors to the right. (i) A view from the left side at that stage. (j) Photographs of the case 6.7 years post-treatment. (k) Periapical radiographs taken one year post-treatment in June 2001. (l) Periapical radiographs taken of the case 10 years post-treatment in September 2009 show no pathology, arrest of the resorption process, excellent regeneration of bone, intact lamina dura and pulp obliteration of and caused by a vital left lateral incisor.

344  Orthodontic Treatment of Impacted Teeth

f

g

h

i

j

k

l Fig. 12.21  (Continued )

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 12.22  (a) Panoramic view at age 11 years showing no abnormality. (b) Panoramic view at age 13, with early oblique root resorption on the distal side of the root of the lateral incisors. The left central incisor has lost almost half its root to resorption. (c) Following exposure and traction of the canine, there is resorption loss of almost the entire lateral incisor root. (d−f) The situation at the first transfer visit. The open surgery exposure had almost completely closed over, with the head of the bonded button attachment still visible and part of the steel ligature wire re-buried in oral mucosa. (g) At the same visit the appliance was refurbished and an auxiliary labial arch placed to draw the canine labially away from the incisor. (h) Full appliances placed and space opening begins. (i−m) The completed treatment with lingual twistflex wire bonded retainers in place. Note that labial root torque of the resorbed lateral incisor was considered inappropriate. (n) The one-year follow-up panoramic view shows the severe degree of resorption of the maxillary incisor teeth and the normal roots of the other teeth.

346  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(i)

(j)

(k)

(l)

Fig. 12.22  (Continued )

The Anatomy of Failure  347 

(m)

(n)

Fig. 12.22  (Continued )

uprighting the incisor will bring its root apex into contact with the crown tip of the canine and develop a force that attempts to force the canine to ‘back up’ along its long axis. This will be a very potent cause of resorption of the incisor root apex. In the case illustrated (Figure 12.23), it will also be seen that negligent positioning of the bracket on the first premolar has brought the root of that tooth mesially and into contact with the inferior aspect of the impacted canine. This further limits the canine’s room for manoeuvre and effectively blocks the desired pathway for its eventual resolution. In this case, a re-evaluation of the biomechanics was made and the bracket of the lateral incisor was immediately removed. The bracket on the first premolar was debonded and replaced by another whose function was to upright the roots distally and, at the same time, to rotate the tooth in a mesio-lingual direction to thereby distance the palatal root from contact with the canine. Once these movements were completed, the canine was exposed on the labial side as high as possible above the resorbing root area of the lateral incisor. Traction was made using an auxiliary labial arch to bring the canine labially high in the sulcus and above the lateral incisor root. Once clear of this entanglement, the labial auxiliary arch was discarded and the canine drawn occlusally towards the archwire. Only at this point does it become appropriate to rebond a bracket on the lateral incisor. In the final stages of the treatment, as the canine comes down to the alveolar junction of the oral mucosa with the attached gingiva, a partial thickness flap will be raised from the attached gingiva on the crest of the ridge, to be apically repositioned over the labial side of the tooth.

Poor anchorage Anchorage is an important consideration in all forms of orthodontic treatment where forces are applied to teeth. The reactive force is distributed to all the other teeth that

share in supporting the fixed or removable appliance. When the unit to be moved comprises a single tooth that may require levelling and tipping only, there will be no perceivable counter-movements on the anchor teeth. However, when an impacted tooth needs to be drawn over a long distance from its initial location to its place in the arch, and then requires to be subjected to significant root uprighting and torqueing movements, loss of anchorage may often be noticeable, specifically altering intermaxillary relations and creating premature contacts and functional mandibular shifts. Since extrusion is one of the main force vectors needed in the treatment of impacted teeth, open bites will often result due to the reactive intrusive forces brought to bear over longish periods on the other teeth in the same jaw. Many practitioners will employ ‘up-and-down’ intermaxillary elastics from the outset as a means of reinforcing the anchorage of the affected arch. However, a mandibular dentition is not immune to adverse movement from consistently applied intermaxillary forces. The long-term use of these vertical elastics will cause an over-eruption of the teeth in the opposing arch and a consequent cant in the occlusal plane, with similar occlusal disturbances. The way to avoid these unfortunate sequelae is to use anchorage elements that are not dependent on other teeth, such as extra-oral headgears and temporary or osseo-integrated implants, as described in earlier chapters. When the side-effect that has occurred is a vertical loss of anchorage, as expressed in the establishment of an open bite, an ‘up-and-down’ elastic placed on a mini-implant in the opposing jaw will be most useful in controlling this unintended consequence. Alternatively, the problem may be conveniently ignored in some cases while vertical traction is being applied to the impacted tooth. The degree of intrusion that may occur is not without limit, and, once the impacted tooth has been aligned in its place in the dental arch, the situation is easily reversible. In this way, and strictly in the final stages of treatment only, the use of

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 12.23  (a−d) Intra-oral photographs to show the initial alignment of the anterior teeth. The disto-labially flared right lateral incisor indicates the expected orientation of the impacted canine. Note the normal axial angulation of the right maxillary first premolar. (e) Initial panoramic view confirming the relationship of impacted canine to incisor root. (f, g) Space is made using routine biomechanics, including levelling and alignment. Poor bracket position has displaced the first premolar root in an excessively mesial direction. (h) Periapical radiograph reveals canine-related, extensive resorption of the root of the lateral incisor. (i) A transaxial slice from the CBCT to show the bucco-lingual and vertical resorption damage and the presence of an enlarged follicle around the unerupted canine. A palatal surgical and orthodontic approach would be technically very difficult and be more damaging to the incisor. (j) A three-dimensional view from the CBCT also indicates the mesial movement of the roots of the first premolar due to the improperly placed Edgewise bracket (compare a and g, above). The palatal root of the premolar introduces a new factor in the impaction of the canine. (k) A transaxial slice from the CBCT to show the premolar palatal root actually contacting the root of the canine and negating a labial approach to the canine impaction. In order to resolve this impaction, the premolar root must be over-uprighted distally and rotated mesio-palatally. This will permit a labial approach both for surgical exposure and orthodontic resolution of the canine. (l) Re-bracketing the case. The red bracket placement jigs illustrate the angulation built into the orientation of the slot. (m) The initial 0.016 in nickel−titanium archwire is tied in. (n) The occlusal view shows the rotation component achieved by correct bracket placement. (o) Surgical exposure and eyelet attachment bonding are performed with the prior placement of the auxiliary archwire ligated in its passive mode. (p) Activation of the horizontal loop of the auxiliary arch is ensured by its vertical ensnarement in the twisted wire ligature emanating through the sutured flap, immediately opposite the re-covered canine. (q) Ten weeks later, the canine breaks through the oral mucosa, high in the sulcus. (r) The auxiliary arch is discarded in favour of vertical traction with elastic thread. An orthodontic bracket may now be re-bonded to the lateral incisor.

The Anatomy of Failure  349 

(g)

(h)

(i)

(j)

(k)

(l)

Fig. 12.23  (Continued )

350  Orthodontic Treatment of Impacted Teeth

(m)

(n)

(o)

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(q)

(r)

Fig. 12.23  (Continued )

The Anatomy of Failure  351  vertical elastics against two heavy base arches of slightly exaggerated, corrective archform will rapidly achieve this goal. Notwithstanding, this is a form of ‘round-tripping’ that many will frown on. It was pointed out in Chapter 6 that, following a closed eruption exposure in the palate, vertical traction of the tooth will cause the thick palatal mucosa to bulge more and more occlusally, with the shape of the tooth clearly outlined beneath. Yet the tissue is sometimes too resistant to permit eruption. In this situation, a small window of palatal mucosa needs to be opened and the tooth will then respond very quickly. Failure to do this will give rise to unwanted movement of the anchor unit (loss of anchorage) and palatal arches may become buried in the palatal tissue (Figure 12.24). A corollary to the use of the labial auxiliary arch in the treatment of a palatal canine is the lack of an appreciation of the three-dimensional picture. A group 2 or a group 3 canine usually needs to be brought down on the palatal side of the arch and erupted through the palatal mucosa, as we have seen above and in several instances illustrated in Chapter 6. This movement is essential in order to take the canine on a vertically circuitous route around the roots of the neighbouring incisors and to provide an obstacle-free path to its place in the arch. However, there is also a height factor, since the tooth may often have been erupted on the palatal side of the line of the dental arch in a high-vaulted palate. Drawing this tooth labially with traction applied from the main archwire, before it has been adequately erupted vertically, may now cause the tooth to become re-buried in the palatal mucosa of the medial wall of the alveolar ridge. This will cause an acute inflammation of these tissues, including swelling and much pain. The mucosal tissue will frequently grow to obscure the tooth, the bonded attachment and the elastic thread (Figure 12.25). The immediate treatment required is to eliminate the lateral traction element, which usually means cutting the elastic tie to the labial archwire, together with irrigation of the area with an atomized water spray and prescribing antiseptic mouthwashes. The symptoms will disappear and the inflammation will subside within a few days. In the longer term, traction should be renewed within a week or so of the acute episode by reinstating the auxiliary labial arch to reapply vertically extrusive traction for a further period until the canine is at the level of the occlusal plane. At that point, traction towards the labial archwire will usually not then produce further problems. A second corollary can produce the opposite effect, due to a lack of appreciation of the efficacy and range of a wellactivated auxiliary labial arch. It was pointed out above that when the buried canine bulges the palatal tissue and does not succeed to break through this thick tissue, it is essential to cut a small window in the mucosa to free the tooth to erupt under the influence of this spring device. Much of

this impressive bulge comprises palatal mucosa and the tooth itself still needs much extrusion. The auxiliary arch is therefore left in place for a further period of activity to overcome this vertical discrepancy. In some cases, however, the speed and extent of the extrusion may be so exaggerated as to markedly over-erupt the aberrant tooth until it actually interferes with the patient’s occlusion (Figure 12.26).

Inefficient appliances The various orthodontic techniques in general use today are extremely efficient in moving erupted teeth around the dental arches, to correct abnormal intermaxillary dental relations and to align crowded teeth to a high standard of finish. The individual brackets have been specifically engineered to achieve this and, given proper professional attention and good patient compliance, most treatment plans can be easily completed within a two-year period. These same fixed appliances are, however, not so efficient when it comes to focusing all one’s energies into the singular effort to resolve the impaction of a severely displaced tooth, and it may take much time to bring the tooth from its ectopic location to an advantageous position close to the main archwire. It is only at that point that a tooth may be reckoned to be in the orthodontic ‘ball-park’. This is the arbitrary point at which further treatment of the erstwhile severely ectopic tooth may be combined with that of all the other teeth, and where the practitioner may be permitted the luxury of relating to the patient as ‘any other routine case’. For many of us, elastic thread tied to the most gingival link of a gold chain and stretched to a rigid archwire is the manner in which we apply traction to the impacted tooth. As we have explained in Chapter 4, this is a very poor way to achieve good and efficient results, because of the small distances across which the elastic thread is drawn. Much clinic time is wasted in the short time-lapses that are necessary between appointments to change the elastic thread and to maintain the extrusive momentum. The practitioner’s ability to control the force delivered and to differentiate between a knotted elastic tie which produces a high force from one that generates no force at all is very limited. The patient may quickly become disconcerted by largely superfluous attrition of his time, which may exhaust his cooperation, courting the possibility of failure by default. Using a spring with a wide range of activity and a measurable force level produces much more rapid results, with excellent control of the force levels being applied and the freedom to allow several weeks between visits, without loss of activity in the spring. To summarize the causes of failure in the resolution of impacted teeth, the orthodontist should consider the following points: 1. Patient-dependent factors (a)  abnormal morphology of impacted tooth (b) age

352  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e) Fig. 12.24  Lost anchorage. (a) Following a closed surgical exposure of this palatal (group 2) canine, traction was applied and the tooth quickly became palpably evident beneath the palatal mucosa. Despite many months of further traction, the tooth did not break through the mucosa but, instead, the soldered palatal arch became buried in the palate, indicating loss of anchorage. (b) A simple incision and removal of palatal tissue over the crown tip reveals the original bonded attachment. (c) A month after the re-application of light occlusal force, the tooth has erupted well. (d) A new eyelet is placed in a more advantageous position and elastic traction direct to the archwire incorporates a rotatory component. (e) Six months later, the archwire is engaged through the eyelet, as the tooth completes its rotation and is brought to its place in the arch.

The Anatomy of Failure  353 

(a)

(b)

(c)

(d)

Fig. 12.25  Inadequate vertical extrusion and iatrogenic damage. (a, b) Viewed from the occlusal aspect and from the left side, the left maxillary canine was mechanically erupted into the palate. It was prematurely drawn labially and became buried in the medial side of the alveolar ridges to produce acute pain, inflammation and swelling. The tooth, the attachment and the traction elastic were buried in the inflammatory tissue. (c) Ten days later, the inflammation and swelling have receded to reveal the formerly impacted canine. An auxiliary labial arch is tied into the brackets piggyback fashion and the position of its active loop section may be seen in its unligated passive mode. (d) In its active extrusive mode, the ligated active loop is now drawing the canine vertically downwards towards the occlusal plane.

(c) pathology of the impacted tooth (d) grossly ectopic teeth (e) resorption of the root of an adjacent tooth (f) lack of compliance (missed appointments, inadequate oral hygiene, etc.) 2. Orthodontist-dependent factors (a) mistaken positional diagnosis and inappropriate directional force (b) missed diagnosis of resorption of the root of an adjacent tooth (c) poor anchorage (d) inefficient appliance (e) inadequate torque 3. Surgeon-dependent factors (a) mistaken positional diagnosis − exposure on wrong side – rummaging exposure (b) injury to impacted tooth

(c) injury to adjacent tooth (d) soft tissue damage (e) surgery without orthodontic planning It is paradoxical that, on the one hand, orthodontics has reached the pinnacle of excellence in the treatment of malocclusion with the highest level of predictability and confidence, which is the envy of virtually every other specialty within dentistry or medicine. The wide spectrum of malocclusions that can be treated well and within a fairly short space of time, with the continuing evolution of more efficient appliances, is truly impressive. On the other hand, when an impacted tooth is one of the elements of this malocclusion, the confidence of the orthodontist is often shaken to the core and there is a degree of apprehension and uncertainty as to whether a successful result may be achieved. The clinician may decide not to accept the patient

354  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 12.26  Excessive vertical extrusion and iatrogenic damage. (a) The initial panoramic view showing the maxillary left canine impacted high in the palate due to an adjacent supernumerary tooth. The deciduous canine has a full-length root. (b) Following a closed surgical exposure, eyelet bonding and immediate traction with a labial auxiliary arch, the tooth has come down and now bulges the thick palatal mucosa, but is unable to penetrate it. The auxiliary arch is seen with its loop in the passive mode (i.e. lying vertically), freed from the twisted steel ligature. (c) A simple minimal re-exposure of the cusp tip is performed, with the loop of the auxiliary arch in its passive mode. (d) The loop of the auxiliary arch is re-ligated in its active mode (i.e. horizontal) to erupt the crown of the tooth. (e) Three weeks later, an unexpected, highly unusual and rapid over-eruption has occurred, bringing the tooth down below the occlusal level. (f) The view from the left side to show severe occlusal interference. An auxiliary nickel−titanium wire is placed in the brackets under the main arch, to apply a corrective rotational, labial and intrusive force to the tooth. (g) The tooth has a long clinical crown, with root exposure on the palatal side, and now requires considerable labial root torque. Both of these handicaps are due to the excessive extrusion. (h) The final stage of treatment to effect the labial root torque is best achieved using a Begg-type torqueing auxiliary.

The Anatomy of Failure  355 

(g)

(h)

Fig. 12.26  (Continued )

for treatment and suggest that the parent seek treatment with another practitioner, who may be more experienced and have greater expertise in this specific area of orthodontics. In the final instance, treatment is most often undertaken accompanied by some form of let-out clause or warning that this particular element of the treatment could fail.

Expert opinion and second opinions during treatment When treatment of an impacted tooth has failed, is in the process of failing or has not shown the expected resolution after a long period, the patient or the orthodontist treating the case may want to consult another orthodontist. Alter­ natively, the request may come from a lawyer representing a patient who feels aggrieved at what he perceives as failure and the possibility of negligence that he assumes must have caused it (Figure 12.27). Regardless of the source of the referral, the principal aim must be the well-being of the patient and a satisfactory resolution of the problem. In general, the patient will arrive for the consultation appointment, together with some radiographs of the initial condition, which may or may not be adequate for accurate positional diagnosis. The orthodontist should perform a careful examination and take note of every detail that may appear relevant. The clinical examination will usually reveal fixed appliances in place on the teeth, which will probably have achieved levelling and alignment of the teeth. Some form of traction applied to a gold chain or wire ligature will be present. If the exposure had been with the closed approach, then careful palpation of the expected location of the impacted tooth should be made, to try to assess its position, and it is especially relevant to attempt to define the direction that force has been applied to the buried tooth, by observing the

(a)

(b) Fig. 12.27  A patient treated by the author c. 1971, using threaded pin attachments for maxillary bilaterally impacted canines. (a) At surgery, the threaded pins were screwed into prepared drill holes in the canine crowns. There was severe, unexplained post-surgical pain, which lasted several days. (b) The orthodontic treatment was successfully completed, but the right canine was markedly discoloured and found to be non-vital. It transpired that the threaded pin had inadvertently entered the pulp chamber during surgery! It should be remembered that the pulps of unerupted teeth in young patients are large, that under the conditions pertaining during a surgical procedure, a clear view of the crown anatomy is not easy to obtain, and directional control for accurate drilling is poor.

356  Orthodontic Treatment of Impacted Teeth traction mechanism. The amount of space prepared in the dental arch for this tooth should then be measured, to see if this is adequate to accommodate the impacted tooth, although this will only be a cause of non-eruption if the tooth is close to the line of the arch. The existing films should be reviewed to see if they are adequate for the task of accurately locating the tooth in three planes of space, and a note made of the dates on which they were taken. If these films are older than a year or so, progress films should be made, and any supplementary views required for positive positional diagnosis ordered. If the diagnosis is not completely clear, or the tooth is in a position and orientation in which three-dimensional relations are difficult to mentally reconstruct, then a CBCT examination should be requested. At the same time, clinical photographs should be taken of the case, without disturbing the appliances. If the patient has not brought the original radiographs, clinical photographs, and plaster casts to the first appointment, every effort should be made to obtain them from the treating orthodontist, even if they are old records. It should be remembered that clinical signs seen (or missed!) in the original malocclusion models or intraoral photographs may show displacement of the crown or root of an adjacent tooth, which may help in diagnosing the initial position of the tooth concerned. These signs will have been largely eradicated by the initial levelling and aligning procedures that will have been completed by the time the second orthodontist sees the patient (Figure 12.16). Second, the active movement of teeth adjacent to an impacted tooth, whether to bring about alignment and levelling or to reopen space, is known to be often associated with renewed eruption activity of the impacted tooth. This may finally be successful in generating eruption or, conversely, in directing the tooth further along the wrong path. So, comparing the old films and the old photographs with new films and a clinical examination may usually lead to a better understanding of the dynamics surrounding the

impaction and to the chance of a more successful resolution of the problem. Before a new treatment plan may be formulated, new casts of the teeth will be needed, and this should be done when all the ordered radiographs have been assembled and after the archwires have been removed. The archwires should then be replaced without renewed activation until a definite line of treatment is devised and until it is decided whether the original practitioner will continue with the case or, for whatever reason, the case will transfer to the new orthodontist or elsewhere, for this part of the treatment.

References   1.  Jacobs SG. Localisation of the unerupted maxillary canine. Aust Orthod J 1986; 9: 313–216.   2.  Armstrong C, Johnston C, Burden D, Stevenson M. Localizing ectopic maxillary canines – horizontal or vertical parallax? Eur J Orthod 2003; 25: 585–589.   3.  Olive RJ. Orthodontic treatment of palatally impacted maxillary canines. Aust Orthod J 2002; 18: 64–70.   4.  Becker A, Chaushu G, Chaushu A. An analysis of failure in the treatment of impacted maxillary canines. American Journal of Orthodontics & Dentofacial Orthopedics, 2010; 137: 743–754.   5.  Becker A, Chaushu S. Success rate and duration of orthodontic treatment for adult patients with palatally impacted maxillary canines. Am J Orthod Dentofacial Orthop 2003; 124: 509–514.   6.  Walker L, Enciso R, Mah J. Three-dimensional localization of maxillary canines with cone-beam computed tomography. Am J Orthod Dentofacial Orthop 2005; 128: 418–423.   7.  Becker A, Chaushu S. Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically-associated canine impaction. Am J Orthod Dentofacial Orthop 2005; 127: 650–654.   8.  Becker A, Chaushu S. Long-term follow-up of severely resorbed maxillary incisors following resolution of etiologically associated canine impaction. American Journal of Orthodontics and Dentofacial Orthopedics 2005, 127: 650–654.   9.  Ling KK, Ho CT, Kravchuk O, Olive RJ. Comparison of surgical and non-surgical methods of treating palatally impacted canines. I. Periodontal and pulpal outcomes. Aust Orthod J. 2007; 23: 1–7. 10.  Ling KK, Ho CT, Kravchuk O, Olive RJ. Comparison of surgical and non-surgical methods of treating palatally impacted canines. II. Aesthetic outcomes. Aust Orthod J 2007; 23: 8–15. 11.  Olive RJ. Factors influencing the non-surgical eruption of palatally impacted canines. Aust Orthod J. 2005; 2195–2201.

13 Traumatic Impaction (In Collaboration with Stella Chaushu)

Acute traumatic intrusion

358

Spontaneous re-eruption

358

Manipulative/surgical repositioning and splinting

358

Orthodontic reduction

358

Orthodontic treatment considerations

360

The indications for the different types of orthodontic appliance

360

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

358  Orthodontic Treatment of Impacted Teeth

Acute traumatic intrusion The waiting areas attached to the offices of local dentists, to emergency rooms of general hospitals and to departments of paediatric dentistry of dental schools are places where one will often see young children who have suffered trauma to the lower part of the face and jaws, which may have resulted in fracture or avulsion of the front teeth. By and large, the traumatic incident will have occurred an hour or two earlier as the result of an accidental blow to the mouth during innocent play, a fall or sporting activity, although the attending practitioner should be watchful and alert to the possibility of child abuse. The treatment for the dental condition and any soft tissue lacerations involves the considerable skills of the paediatric dentist, the endodontist and the oral surgeon, and is not within the scope and context of this book. Nevertheless, there is one small corner of the field of traumatic injury in which emergency adjunctive orthodontic treatment may sometimes be of value, and this relates to those injuries in which there has been displacement of the damaged teeth, particularly intrusive luxation. This may be alternatively referred to as the acute, traumatically induced impaction of a previously erupted tooth, and it requires special attention. It will be readily understood that, however successful endodontic and restorative treatments may be in providing for a renewed healthy retention of the tooth in its surroundings, it is with regard to our ability to realign it to its former place in the dental arch that a favourable outcome must be judged and success measured. This type of injury occurs as the result of a severe blow in the general orientation of the long axis of the tooth, which will drive the tooth upwards into the alveolar process. This results in injury to the periodontal ligament, involving a severance of the gingival and periodontal fibres, which will usually be accompanied by varying degrees of crown fracture and fracture and comminution of the bone lining the socket. In the longer term it will be a major factor in the occurrence of root resorption [1]. The insult to the pulp will cause pulp necrosis in virtually every case where the apex is closed and in about half the cases when the root apex is still open [2]. In the latter, there will often be arrest in further root development [1]. Intrusive luxation may find its resolution in one of three ways: re-eruption • spontaneous manipulative/surgical • orthodontic reductionrepositioning and splinting •

Spontaneous re-eruption Following the vertical displacement, an affected tooth may re-erupt and eventually return to its original position [3], particularly if its root apex is still open [1] (Figure 13.1), although some will re-erupt even after root closure. Should

the teeth remain intruded after several weeks of follow-up, corrective relocation will be needed. For these cases, some emergency treatment and initial restorative procedures will already have been carried out by the paediatric dentist, endodontist or oral surgeon, and the patient will not be in pain at the time that this assistance is required. However, whether the relocation of the intruded tooth is achieved by orthodontic movement or surgical manipulation, additional insult is borne by the tooth, which would be avoided if the potential for spontaneous re-eruption could be realized [1].

Manipulative/surgical repositioning and splinting For immediate repositioning of the tooth to be successful, the tooth needs to be gently manoeuvred into its former place and splinted there for several weeks, in the hope that the severed gingival and periodontal fibres will heal to maintain the tooth in its place for the long term. Concern for the future of the tooth is expressed on three levels, namely: restoration of the periodontal attachment, assuring re• establishment of the integrity between the tooth and its supporting tissues; healing of the pulp tissues or of the periapical environment after pulp extirpation and root canal therapy (the reader is referred to appropriate texts in paediatric dentistry, endodontics and oral surgery for details of these procedures); the degree of root resorption that is virtually an inevitable sequela.

• •

Orthodontic reduction If extrusive forces are applied to an intruded tooth which has few intact periodontal fibres immediately following the traumatic episode, it is highly likely that the tooth will be exfoliated within a very short time. Thus, before initiating traction, it is essential to wait for at least a couple of weeks to allow for healing and the re-establishment of some measure of periodontal support that will hopefully occur with the organization of the blood clot and reattachment of the periodontal fibres. For this tooth to ‘take’ and be successful, the desired union of tooth to the surrounding bone is by periodontal fibre healing alone or by healing with surface resorption. According to Andreasen and Andreasen [4], healing without surface resorption is probably not a possibility in the clinical situation since it needs to be completed totally without injury to the innermost layer of the periodontal ligament. However, healing with surface resorption will leave the luxated tooth attached to the socket with a normal periodontal ligament and new cementum. Such a tooth will respond to orthodontic forces.

Traumatic Impaction  359 

(b)

(a)

(d)

(c) Fig. 13.1  An 8-year-old female following trauma to the lower face. (a, b) Seen four days post-trauma, there is an intrusive displacement of both central and right lateral incisors. (c, d) At seven weeks post-trauma, the teeth have partially re-erupted without orthodontic treatment.

If, on the other hand, healing is by replacement resorption, there is a direct union between the root and the surrounding bone. Repair will be counted as successful, but the tooth will then never be amenable to orthodontic forces. Sometimes a transient replacement resorption will occur and the tooth may then regain a normal attachment. This is by no means certain, and it is probably more likely that areas of ankylosis will occur over the root surface and the tooth will then remain intruded permanently. In this condition, the tooth is a liability to the dentition; nor is it useful as a foundation for a lasting prosthodontic restoration. An intruded and ankylotic tooth in a growing child will become more and more infra-occluded in relation to the adjacent teeth, and its accompanying bone will also be lacking when compared to the normal vertical development of the alveolar bone surrounding the unaffected teeth. For this reason, there is only limited value in maintaining the tooth as a

means of preserving alveolar bone and under these conditions its extraction may often be preferred. Orthodontic intervention at the appropriate time may offer the only viable treatment option, which, together with certain relatively minor restorative procedures, may produce a good result, with a fair prognosis. If the tooth is still completely sub-gingival, then the labial gingival soft tissue will need to be pared back or apically repositioned until 2 mm of the incisal edge of the tooth is revealed. Light extrusive force must be applied after the time that the periodontal fibres have begun to reunite and in the earlier stages of organization of the blood clot, but before the deposition of bone (i.e. 10–28 days post-trauma). In a meta-analysis designed to evaluate the orthodontic modality of treatment of these cases [2] and which included material taken from other published studies of individual cases and case series reports, there was a 90% rate of

360  Orthodontic Treatment of Impacted Teeth successful repositioning of the intruded teeth. As pointed out above, all those teeth with closed apices lost their vitality, together with approximately half those with an open apex. External root resorption was diagnosed in 54.8% of the involved teeth. Marginal bone loss was rarely seen in the patients, which is in sharp contrast to the findings of other studies [1]. Inflammatory root resorption occurred as a late complication in teeth with closed apices, and pulp obliteration was seen in those teeth that remained vital. The ‘takehome message’ from that study was that orthodontic reduction was the most reliable of the three alternatives and was found to be kinder to both hard and soft tissues than the surgical option. It provided the opportunity for a superior outcome in terms of fewer teeth lost and potential complications. This view is not universally held, since other studies have found little difference in the long-term results between the orthodontic and surgical options, and it has been argued that the extra clinic time and attention needed for orthodontic reduction of the traumatic intrusion does not justify any potential minor difference in the long-term results [1].

Orthodontic treatment considerations Special care must be exercised when using fixed appliances in this situation [4]. First, for any extrusive movement of a single tooth or group of teeth, some kind of resistant framework needs to be bonded to the adjacent teeth, which acts as a multiple anchor unit from which force would be applied to the intruded tooth or teeth. This may take the form of a few brackets and an archwire, although the composite bonding of a customized rigid wire directly to the labial enamel of these teeth (illustrated below) would be more satisfactory from many points of view. Unfortunately, these adjacent teeth will themselves have almost certainly been traumatized at the time of the accident, and using them in this manner may lead to further damage even at the light force levels involved. Second, if the intended extrusion is initiated later than two months post-trauma, ankylosis may have affected the intruded tooth [4]. Active extrusive forces generated by the appliance will then be to no avail. Instead, the reactive forces will be absorbed by the anchor teeth and these will become intruded. Many children attending for routine comprehensive orthodontic treatment, particularly in the presence of an enlarged overjet, have a history of non-displacement trauma to the maxillary incisor teeth, which have then undergone root canal therapy. The advice usually given is that orthodontic treatment should be delayed for several months, until there is some radiographic evidence of repair. However, following intrusive trauma, the possibility of the occurrence of ankylosis (replacement resorption) is significant and will be evident within two months. Teeth that had completed root development at the time of the accident are

generally scheduled for root treatment in the first week after the traumatic incident. Thus, these exceptional circumstances dictate that the orthodontic extrusion of these teeth must begin at the latest six weeks or so after the traumatic episode, although the 10–28-day time-frame is to be preferred [2]. The risk of failure of extrusion due to replacement resorption is high and absolute, which is why treatment should begin within this time. The risk of an orthodontically induced complication of the root treatment is much lower and of less therapeutic significance. Once the tooth is brought into alignment it may be retained and splinted to its immediate neighbours, using a short length of multi-strand wire, which is bonded to the labial surface of the three teeth for a few weeks only. It has been considered important not to cover the wire completely with composite material, but to place a small quantity of composite material across the wire over each tooth and to leave broad interproximal areas of exposed and flexible wire. Rigid bonding for long periods is contraindicated, since it seems to lead to a greater incidence of pulp necrosis and pulp obliteration [5, 6]. The use of a multi-strand wire splint allows a degree of movement, which is similar in extent to that seen in physiological mobility [7–10] and thus it may be argued that it can be safely used for considerably longer if desired. However, newer evidence appears to find no difference in outcome between rigid and flexible splinting, nor does it find that the length of time that stabilization is present alters the prognosis [1].

The indications for the different types of orthodontic appliance The removable appliance Simple removable appliances (Figure 13.2) are most suitable since they need apply no force to the adjacent teeth, the anchorage being derived from their broad contact with the palatal mucosa, via the acrylic base [11, 12]. A small button attachment is bonded on the labial side of the tooth and the labial bow of the removable appliance is divided at the midline. One arm of this divided labial bow may then be activated vertically downward against the button while the other half of the labial bow is removed. Treatment generally proceeds rapidly, with the tooth appearing in the mouth and at the level of its neighbours within a few weeks, depending on the amount of extrusion required. This method has the advantage of simplicity and, since it is independent of support from other anterior teeth which may have been damaged in the trauma incident, its use will incur fewer dangers than other methods. However, since the activation depends on the patient placing the activated labial bow over the labial button attachment, clumsiness or lack of care may result in the tooth being displaced labially or palatally or the activation being nullified.

(a)

(b)

(c)

(d)

(e) Fig. 13.2  The removable appliance. (a) Acute intrusion of a maxillary left and crown fracture of the maxillary right central incisors. (b) The tangential radiograph shows intrusive and buccal displacement. (c) At 14 days post-trauma, a button attachment is bonded to the intruded incisor. The labial arch is activated to extrude the tooth and the patient is instructed in accurate placement and care. (d, e) The tooth has re-erupted. Both central incisors have had root canal treatment and crown restoration. (Courtesy of Professor B. Peretz.)

362  Orthodontic Treatment of Impacted Teeth

(b) (a)

(c)

(d) Fig. 13.3  The wire frame. (a) As the result of a fall in an 8-year-old female patient disabled with cerebral palsy, the right maxillary central incisor has suffered intrusive avulsion and its incisal edge is barely visible at the gingival margin. (b) During the intravenous (propofol) sedation session, endodontic treatment was undertaken, while the wire frame was fashioned chair side and bonded to the adjacent teeth. After debridement, an eyelet was bonded to the visible incisal edge and light elastic traction was applied. (c) A month later, the tooth was fully erupted and the frame was removed. No further retention was used. (d) The periapical view of the root-filled tooth shows evidence of resorption of the root.

The bonded wire frame Fractured incisors are very common in special needs children [13–18], particularly those afflicted by cerebral palsy. Depending on the area of the brain affected, the child may be unable to walk or may do so only with great difficulty and will consequently be more prone to accidental falling. With similarly affected upper limbs and slower reactions, he may be unable to protect himself with his hands and the result will often be that the nose, lips and teeth – particularly protruding teeth – will absorb the brunt of the

trauma as he/she hits the ground. Most young children, healthy or disabled, will need sedation or general anaesthesia to enable the successful performance of the variety of different treatments that are likely to be required in the emergency session that may follow the traumatic incident. While undergoing gingival debridement, suturing of a lacerated tongue or lip tissues or an initial pulp treatment the bonded wire frame (Figure 13.3) may be fabricated at the chair side, even if these are being carried out under a general anaesthetic. It may also be made on a plaster model

Traumatic Impaction  363  cast from a snap impression taken at the start of this multidisciplinary session and while the other procedures are being performed. A length of 0.020 in steel wire may be adapted and bonded to the labial surfaces of two or three teeth either side of the intruded tooth. The middle portion of this wire is formed into a vertically offset section with a loop opposite the intruded tooth and 3 or 4 mm vertically below it. Tying elastic thread lightly between an eyelet bonded to the tooth and this loop will apply gentle extrusive pressure to the tooth (Figure 13.3). Directly bonding the wire to the adjacent teeth transfers the reactive force to these teeth with relatively little chance of overtaxing them, since they are united into a rigid anchor unit and the force is divided more or less equally between them. This method has the advantage that it may be constructed and placed as part of the single session with simplicity and requires neither sophisticated orthodontic brackets nor any great skill. A self-supported labial arch on fixed molar bands A third possible appliance design involves the placement of molar bands with a soldered palatal arch, preferably (although not compulsorily) including an acrylic Nance button in the palate. Round 0.036 in (0.9 mm) tubes are soldered to the buccal side of the bands and a heavy self-supporting 0.036 in labial archwire is fashioned to include adjustment loops immediately mesial to the tubes to act as stops. These loop stops hold the archwire a millimetre or two labial to the anterior region and, in its passive position, is at or slightly below the occlusal level. With light finger pressure the anterior portion may be raised and tied with steel ligature wires to the button or eyelet attachments to the labial side of one or more intruded teeth to generate extrusive traction, whose force is measurable and controllable and its range adjustable (Figure 13.4). This method is to be preferred over the use of a regular fixed orthodontic appliance, with brackets on each of the anterior teeth and the use of progressively heavier wires as the teeth come into alignment, since the need for initial levelling will take unaffordable time and it is unnecessarily sophisticated in these emergency conditions. The selfsupported arch is also a method that is particularly suited to the resolution of multiple intrusion cases. Once the tooth erupts, root canal therapy is usually needed [2] and a permanent restoration may be placed, followed by a short period of retention. Parents of very young children who have recently experienced this type of acute trauma are often confused by the need for the multidisciplinary treatments and they may have approached their insurance company, or the insurance company representing the school where the accident occurred, seeking financial recompense. Accordingly, much

time may be lost in the interim, during which the various aspects of the treatment slowly become understood and accepted and informed consent granted. Frequently, therefore, orthodontics is delayed and ankylosis may have begun. The recommended approach in these cases is to place appliances as planned and to spend a few weeks during which light force is applied to the tooth to see if it will respond. If there are several teeth involved, and if the active extrusive mechanism is a shared one, it should be remembered that it requires just one ankylosed tooth to prevent the others from re-erupting. Freeing one or another of a group of teeth or applying individual extrusive force delivery elements, therefore, may permit one of the teeth to respond. If there should be no change in the position of one or more of the teeth, then the very rudimentary and poorly developed ankylotic connection should be gently broken, using an extraction forceps under local anaesthetic cover, and the extrusive force immediately reapplied. The palato-labial partial avulsion A child may sustain a severe blow to the premaxillary area so as to displace a maxillary central incisor in such a way that the crown is tipped inwards and the root, still covered by the labial oral mucosa, protrudes through the labial plate of alveolar bone – the so-called lateral avulsion. The patient is unable to close the teeth together due to prematurity of the displaced tooth. In the heat of the moment and lacking suitable direction, the parents of a child do not always attend the appropriate clinic or the most knowledgeable dental practitioner. Emergency treatment indicated for this case is to manipulate the tooth to its original site under local anaesthetic, and to splint it in place. The patient seen in Figure 13.5 was treated by grinding the incisor to reduce the occlusal interference and given a bite plate to disarticulate the teeth! By the time the parent was finally referred to a trained paediatric dentist, several days had elapsed. The paediatric dentist referred the patient on to an oral surgeon, with the request that manipulative relocation and splinting be undertaken. The oral surgeon considered that reduction without evacuation of the several days-old blood clot was no longer appropriate, and evacuation of the blood clot would have dictated an open flap procedure which, in turn, would have relegated the prognosis of the incisor to an unacceptably low level. Orthodontic treatment was prescribed to re-site the tooth by applying labial tipping and then palatal root torque. Since this involved its being moved through freshly organizing blood clot, the treatment proceeded with great speed. The tooth maintained its vitality, as evidenced by positive pulp testing and subsequent pulp obliteration. Finally, the ground-down crown was restored with composite material, and follow-up periapical radiography has

364  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d) Fig. 13.4  The self-supporting labial arch. (a, b) A 9-year-old cerebral palsied child fell forwards from her wheelchair and displaced all four maxillary incisors superiorly upwards into their sockets. (c) A periapical view of the anterior teeth shows the degree of the displacement and the absence of root fracture. (d) A tangential view of the anterior maxilla shows the incisor teeth to have been displaced upwards and labially, with the labial plate of bone visibly displaced. (e, f) Molar bands were adapted and an impression taken from which this simple appliance was constructed, involving a soldered palatal arch and a labial archwire of 0.036 in gauge, which slots into soldered round molar tubes of the same diameter. This preparation was done during the same intravenous (propofol) sedation session as was exploited for surgical debridement of the gingival tissue and root canal therapy. (g, h) Eyelet attachments are composite bonded to the labial surfaces of the intruded incisor teeth, after some gingival reduction, and the removable heavy archwire is inserted into the molar tubes. The front of the labial arch is gently raised and tied with steel ligatures up to the eyelet attachments. (i) A month later, the teeth have all re-erupted. A periapical view of the left lateral incisor shows inflammatory root resorption. (j) At six months post-treatment, the lateral incisor has been removed and there is early cervical root resorption of the right lateral incisor. (k) The intra-oral view at six months shows the central incisors in good positions. The cervical root resorption lesion of the right lateral incisor is clearly seen.

Traumatic Impaction  365 

(e)

(f)

(g) (h) Fig. 13.4  (Continued )

not shown signs of root resorption, while the pulp chamber has become totally obliterated. It is clear that the paediatric dentist, rather than the orthodontist, is the person who has to face the challenges that the patient who has suffered intrusive luxation or gross displacement of a maxillary incisor tooth presents and to accept responsibility for the conduct of the treatment. It is the paediatric dentist who must surely be the main contractor in the care of the injured child, bringing in a surgical, endodontic or orthodontic ‘subcontractor’ to perform specific parts of the multidisciplinary treatment, as and when necessary. In spite of this, there appears to be an unexplained over-enthusiasm among paediatric dentists to undertake the limited orthodontic procedures described here, which may sometimes be quite complicated. At the same time, there is a reticence on the part of orthodontists to accept these patients for treatment because of the very real risk that the injured tooth may become resorbed, ankylosed or lost during the treatment. Such sequelae are rarely encountered in routine orthodontic treatment and, when they are diagnosed, they come as an unwelcome surprise to the orthodontist. Orthodontists see these as signs of treat-

ment failure, and many will thus prefer to shy away from undertaking orthodontic treatment on traumatized teeth when the chances of these phenomena occurring may be high. This represents an unfortunate and misplaced evasion of responsibility on the part of the orthodontist towards the patient. The experienced orthodontist is the most skilled professional trained and able to apply appropriate directional forces to resolve intruded and other displaced teeth and to do so with speed, with suitable force levels and with least discomfort to the patient. In this respect, he/she has an important role to play as an occasional but integral member of the multidisciplinary dental trauma team in the early stages of the emergency treatment in cases of traumatic impaction. One further point leads on from this specific issue. Judging by what we see in our orthodontic practices, there appears to be a very significant minority of children who show signs of past trauma to their anterior teeth to a greater or lesser extent, which has obviously occurred over the few years between their eruption and the age at which they are ready for orthodontic treatment. But of the remainder, the apparently silent majority who show no

366  Orthodontic Treatment of Impacted Teeth

(j)

(i)

(k) Fig. 13.4  (Continued )

outward signs of trauma, there is an unknown number who have suffered a relatively minor blow at one time or another and who woke up the following morning with no pain or discomfort. Most of these children will soon have no memory of the traumatic incident, yet this may be the cause of the silent, degenerating health and possibly a slow and asymptomatic death of the pulp. There is reason to believe that this may be a more common sequence of events than is commonly thought. Suffice it to say that when orthodontic treatment is initiated and even minimal force is applied to such a

tooth, the hyperemia that normally affects the pulp in the first few days merely serves to reawaken the vital remnants of degenerated pulp tissue, and a cycle of events occurs which may then lead to discoloration of the crown and, from there, to endodontic therapy [19, 20]. The common accusation of the general dentist or the endodontist may then be that the orthodontist has applied excessive force with the appliance and that this was the cause of the pulp pathology. From these ill-considered and irresponsible comments to the law courts may sometimes be a very short path!

Traumatic Impaction  367 

(a)

(c)

(e)

(b)

(d)

(f)

Fig. 13.5  (a, b) Front and left views, showing palatally displaced central incisor, one week post-trauma. The crown reduction is clearly seen. (c, d) Modified Johnson’s twin-arch appliance in place. Buccal coil springs apply labially directed force on the single 0.018 in archwire, which engages the bracket of the displaced tooth. (e, f) A torqueing auxiliary is laced down to the main archwire and tied back to the molar tubes. (g–i) Twelve months after completion of treatment: front and left views of the occlusion and a close-up view of the maxillary central incisor teeth. (j, k) Periapical and tangential pre-treatment views. (l, m) Tangential and periapical views four weeks later. (n) Periapical view at two years post-treatment showing obliterated pulp – evidence of maintained pulp vitality.

368  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(i)

(j)

(k) Fig. 13.5  (Continued )

(l)

Traumatic Impaction  369 

(m)

(n)

Fig. 13.5  (Continued )

References   1.  Andreasen JO, Bakland LK, Andreasen FM. Traumatic intrusion of permanent teeth. Part 3. A clinical study of the effect of treatment variables such as treatment delay, method of repositioning, type of splint, length of splinting and antibiotics on 140 teeth. Dent Traumatol 2006; 22: 99–111.   2.  Chaushu S, Shapira J, Heling I, Becker A. Emergency ortho­ dontic treatment following the traumatic intrusive luxation of maxillary incisor teeth. Am J Orthod Dentofacial Orthop 2004; 126: 162–172.   3.  Shapira J, Regev L, Liebfeld H. Re-eruption of completely intruded immature permanent incisors. Endod Dent Traumatol 1986; 2: 113–116.   4.  Andreasen JO, Andreasen FM. Textbook and Color Atlas of Traumatic Injuries to the Teeth. Copenhagen: Munksgaard, 1994.   5.  Andreasen RM, Verstergaard Pedersen B. Prognosis of luxated permanent teeth – the development of pulp necrosis. Endod Dent Traumatol 1985; 1: 207–220.   6.  Rock WP, Grundy MC. The effect of luxation and subluxation upon the prognosis of traumatized incisor teeth. J Dent 1981; 9: 224–230.   7.  Zachrisson BU. Clinical experience with direct-bonded orthodontic retainers. Am J Orthod 1977; 71: 440–448.   8.  Becker A. Periodontal splinting with multistrand wire following orthodontic realignment of migrated teeth: report of 38 cases. Int J Adult Orthod Orthogn Surg 1987; 2: 99–109.   9.  Becker A, Goultschin J. The multistrand retainer and splint. Am J Orthod 1984; 85: 470–474.

10.  Dahl EH, Zachrisson B. Long-term experience with direct-bonded lingual retainers. J Clin Orthod 1991; 25: 619–630. 11.  Peretz B, Becker A, Chosak A. The repositioning of a traumaticallyintruded mature rooted permanent incisor with a removable appliance. J Pedodont 1982; 6: 343–354. 12.  Mamber EK. Treatment of intruded permanent incisors: a multidisciplinary approach. Endod Dent Traumatol 1994; 10: 98–104. 13.  Becker A, Shapira J. Orthodontics for the handicapped child. Eur. J. Orthod 1996; 18: 55–67. 14.  Becker A, Shapira J, Chaushu S. Orthodontic treatment for disabled children: motivation, expectation and satisfaction. European Journal of Orthodontics. 2000; 22: 151–158. 15.  Chaushu S, Gozal D, Becker A. Intravenous sedation: an adjunct to enable orthodontic treatment for children with disabilities. European Journal of Orthodontics 2002; 24: 81–89. 16.  Chaushu S, Shapira J, Heling I, Becker A. Emergency orthodontic treatment following the traumatic intrusive luxation of maxillary incisor teeth. A J Orthod Dentofacial Orthop 2004; 126: 162–172. 17.  Becker A, Chaushu S, Shapira J. Orthodontic treatment for the special needs child. Seminars in Orthodontics 2004; 10: 281–292. 18.  Becker A, Shapira J, Chaushu S. Orthodontic treatment for the special needs child. Progress in Orthodontics, 2009; 10: 34–47. 19.  Brin I, Ben-Bassat Y, Heling I, Engelberg A. The influence of orthodontic treatment on previously traumatized permanent incisors. Eur J Orthod 1991; 13: 372–377. 20.  Brin I, Ben-Bassat Y, Heling I, Brezniak N. Profile of an orthodontic patient at risk of dental trauma. Endod Dent Traumatol 2000; 16: 111–115.

14 Cleidocranial Dysplasia

Clinical features and dental characteristics

371

Treatment modalities

373

Dental crowding

380

Retention of the treated result

381

The Jerusalem approach in clinical practice

381

Treatment experience

393

Patient variation

396

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

Cleidocranial Dysplasia  371 

Clinical features and dental characteristics The cleidocranial dysplasia patient is typically of short stature, with a brachycephalic skull and bossing of the parietal and frontal bones. There is hypoplasia of the mid-face, giving the misleading appearance of mandibular prognathism. The skull sutures and fontanelles exhibit delayed closure and secondary centres of ossification occur in these areas, with the formation of wormian bones. The development of the clavicles is defective and ranges from a small medial gap to total absence in severe cases [1–7]. The patient usually has a narrow chest and sloping shoulders. According to Stewart and Prescott [8] more than 100 other anomalies have been associated with these major clinical features of the condition. Cleidocranial dysplasia does not affect the sufferer mentally or intellectually and, from this aspect, he/she is completely normal. The palate is narrow and occasionally high, and there is a marked degree of lateness in the development of the deciduous dentition, while eruption is generally normal. There is rarely any alteration in the number of the deciduous teeth, although on occasion, erupted supernumerary/supplemental deciduous teeth may be seen in the incisor area. The permanent molars usually erupt late, but spontaneously, while the remainder of the permanent dentition (i.e. the successional teeth – incisor, canines and premolars) exhibit very delayed or non-eruption. Additionally, supernumerary teeth typically develop in the successional teeth areas and much less frequently in the molar areas in numbers that may vary from none to around 12 in general. While greater numbers are uncommon in these cases, the highest recorded number reported in the literature was 63 [9]. Apart from barrel-shaped teeth and the rare occurrence of peg-shaped teeth in the maxillary incisor area only, the supernumerary teeth take the form of premolars in the premolar area, canines in the canine area and incisors in the incisor area. They may therefore be more appropriately referred to as supplemental teeth. At the other end of the scale, the author’s experience with a large number of these cases has revealed two patients with the correct number of teeth, another with congenitally missing maxillary lateral incisors and yet another with a missing third molar. Equally affecting males and females, cleidocranial dysplasia is an autosomal dominant inherited disease [4] and there is a high incidence of new mutations at around 20– 40% of all cases [5]. Part of the RUNX family of transcription factors, RUNX2 (Runt-related transcription factor 2) is known to be the gene directly involved. It encodes a nuclear protein, 521 amino acids, (56648 Da) with a Runt DNA-binding domain. RUNX2 is essential for osteoblastic differentiation and skeletal morphogenesis, acting as a scaffold for nucleic acids and regulatory factors involved in skeletal gene expression. RUNX2 is the only gene specific to the aetiology of CCD, with sequence analysis showing 60–70% of CCD patients

present with a missense or nonsense mutations, small insertions or deletions and exon skipping. Among the remaining 30–40% of patients with mutations, 13% may be found by other means of testing (karyotype for visible deletions, insertions and rearrangements involving the RUNX2 locus in chromosome 6p21, qPCR, Real-time PCR, FISH, etc.) to have large deletions of the gene and of the genes following. Mutations in the RUNX2 gene span the whole gene and are highly penetrant. There is no clear genotype/phenotype correlation in CCD. Although, when mutations of RUNX2 are found, they are pathognomonic of the disease and phenotypes of other diseases are not associated with them [10]. Approximately one-third of the cases we have seen have been sporadic occurrences, with no family history of the condition. Most of the cases that have been under our care come from families where a parent was affected and thus diagnosis was usually (but not always) made at birth. For most of the other cases, a tentative or initial diagnosis was suspected only several years later by the child’s paediatrician or orthopaedist, although the discovery may sometimes be made at a routine paediatric dental examination. Corroborative evidence from a clinical examination and a wider radiological examination was then obtained to establish the definitive diagnosis. During the physical examination, the clinician should attempt to confirm as many of the features described above as possible. In particular, the patient should be asked to approximate the shoulders to confirm the clavicle anomaly (Figure 14.1). Palpation should also be made of the areas between the parietal bones on the crown of the skull and between the frontal bones at the upper forehead/hairline region. In both of these midline areas, a smooth and wide hollow, concavity or furrow (Figure 14.2) may be clearly felt, in contrast to the convex contour of the skull of a normal child. Radiological examination should include views of the clavicles (Figure 14.3), the fontanelles, which may be seen on lateral and posteroanterior cephalometric films (Figures 14.4 a, b) and an initial panoramic film of the jaws (Figure 14.6). Aside from the principal bony defects of the cranium and clavicles, a good proportion of CCD individuals suffer other skeletal and orthopaedic anomalies. According to Cooper et al. in 2001, 57% suffer from flat feet, 28% from knock-knees and 18% from scoliosis, while joint dislocation of the shoulder and elbow may also occur [11]. Additionally, infections of the upper respiratory tract are common, specifically the sinuses and the ears, where conductive hearing loss occurs in 39% of the cases. Treatment for these associated conditions is indicated and should be performed by the paediatric specialist concerned. For the most part, the signs and symptoms of the condition are very distinct and, these predispositions aside, entirely benign. They are in no way progressive, the patient is not physically or mentally disabled and, in general, other body systems are not adversely affected.

(a)

(b)

Fig. 14.1  (a, b) The approximated shoulders of a cleidocranial dysplasia patient.

Fig. 14.2  Frontal midline furrow passing through the hairline.

Fig. 14.3  Chest radiograph to show incomplete clavicles.

Fig. 14.4  (a, b) The postero-anterior and lateral cephalograms show abnormal cranial form, open fontanelles and numerous wormian bones (arrowed).

Cleidocranial Dysplasia  373  At present, there is no way to change the underlying inherited condition, treatment cannot therefore be advised for the primary condition [5, 6] and its diagnosis does little more than label the child as an oddity. The only situation where treatment is needed is when one or more of the associated consequences become burdensome. By and large, it is the oral and dental disability of the condition that undoubtedly presents its most serious ramifications, since this affects the vertical and horizontal growth of the face and oral structures, including alveolar bone and teeth. From student to experienced practitioner in the dental profession, and out of all proportion to the rarity of the condition, its clinical features are surprisingly well known, again reflecting its curiosity value rather than any ability on the part of the profession to have been able to promote change and correction in the past. For many decades, the profession has stood in awe of the overwhelming number of the dental problems that these cases present, unable to offer satisfactory answers. The dental characteristics typically include overretention of the deciduous dentition, non-eruption of the permanent dentition and the presence of many supernumerary teeth (Figure 14.5). Nevertheless, there is no dental discomfort or disturbance, unless the deciduous teeth become decayed. These teeth are small relative to the growing face and are not visible below the upper lip, particularly when an often seen anterior open bite is present. In many cases, in the rest position it is the tongue that is visible between the lips (Figure 14.6). The horizontal growth pattern generally produces a mandible of normal length and an underdeveloped maxilla which therefore produces a skeletal and dental class 3 relationship. However, this relationship is not always present initially in the younger patient, but may gather momentum during the adolescent growth spurt to a greater or lesser degree [12] (Figure 14.7). This trend is by no means certain, and there are cases of good class 1 relationships and even the occasional class 2 case that may be diagnosed, as they complete the development of their facial pattern, at the end of the adolescent growth period. The vertical growth of the alveolar processes is generally deficient, which leaves the patient with very shallow labial and lingual sulci in both jaws. Taken together, these features give the patient an edentulous appearance, which may often be the presenting symptom. Some light has been shed on a possible reason for the non-resorption and over-retention of the deciduous teeth and the non-eruption of the permanent teeth in these cases [13]. It has been proposed that decreased root surface resorption occurs in the deciduous teeth due to a thin uniform layer of resorption-resistant acellular cementum covering virtually the entire root. In the permanent teeth, very little cellular cementum is seen on the roots of the teeth. However, secondary deposition of reparative cementum is found in areas of focal resorptive defects, and this

may be blamed for the non-eruption of the permanent teeth. Given that: 1. the child with cleidocranial dysplasia has little by way of a tangible complaint involving pathology (no pain, no swelling, no difficulty in functioning), yet 2. the dentist has diagnosed a benign condition of extraordinary therapeutic magnitude, 3. the dentist has no available guidelines on how to even begin to approach the resolution of the problem, 4. a practitioner seeing a case for the first time is unable to predict treatment results, and 5. the degree of facial deformity is usually of insufficient consequence to demand surgical modification, at least in the younger patient, it is entirely understandable that a responsible clinician will hesitate before undertaking treatment. The options are: to offer treatment at all; • not to suggest more radical approach of extraction of • many teeth,thefollowed by prosthetic replacement; or to advise an orthodontic–surgical treatment procedure, • with an unknown level of confidence in the ability to achieve the desired outcome. However, non-treatment becomes less of an option as the patient grows older. Because of considerable occlusal attrition and caries there is a progressive morbidity of the deciduous dentition, which starts in the early teens and gathers pace over just a few years. Root canal treatment is often needed and restoration becomes difficult. The patient’s appearance suffers further, with a reduced lower face height [14], impaired masticatory function and continuing facial growth contributing to the increasing over-closed appearance. Treatment is needed to provide an efficient masticatory apparatus and improvements in the dental appearance and the facial proportions.

Treatment modalities These goals may be realized in several ways. The methods that have been proposed over a period of many years have most often reflected the particular area of dentistry in which the treating dentist has specialized. Therefore, to a degree, the mode of treatment may depend on whose door the patient first knocks! Prosthodontics The most popular approach has been to provide the patient with removable partial or full prostheses, which fulfil all the immediate needs of the patient. This approach has been suggested by many only after the removal of all the deciduous teeth and the unerupted supernumerary and permanent teeth [9, 15, 16]. Given that the alveolar bone height

374  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e) Fig. 14.5  Variation in number of supernumerary teeth in cleidocranial dysplasia patients. (a) A 14-year-old female with eight extra teeth. (b) A 14-year-old female with five extra teeth. (c) A 13-year-old male with one mesiodens. (d) A 12-year-old male with a missing tooth and no supernumeraries. (e) A 14-year-old female with a full deciduous dentition and two erupted supernumerary deciduous maxillary lateral incisors. Only one erupted (deeply carious) permanent molar is present. There are 27 supernumerary teeth, in addition to the 31 unerupted permanent teeth – a total of 81 teeth! Note the presence of supplemental molar teeth.

Fig. 14.6  The tongue is visible at rest, protruding between the lips.

(a) (c)

(b)

(d)

(e)

(f)

Fig. 14.7  Typical growth in the cleidocranial dysplasia patient. (a, b) At age 10 years, the facial soft tissue profile is orthognathic, although the intra-oral dental and dental base relations are class 3. (c, d) At age 17 years, there is a clear underdevelopment of the mid-face, with an accompanying mandibular prognathism and a marked worsening of the class 3 dental and skeletal relations. The patient is being prepared for orthognathic surgery. (Courtesy of Dr D. Harary.) (e, f ) At age 17.5 years and following surgical correction.

376  Orthodontic Treatment of Impacted Teeth in these cases is very limited, with shallow sulci, the dentist should ponder the implications of the construction of replacement tissue-borne prostheses 10 years later, after additional and iatrogenic ridge resorption has occurred. Others have advised retaining the standing teeth and the construction of prostheses around them [8, 16–18]. A further refinement recommends the exploitation of any standing teeth, together with the surgical exposure of the more superficial unerupted teeth, to serve as supports for an over-denture [18–20]. By making it tooth-borne, the denture is less likely to cause further ridge resorption, but the supporting teeth will deteriorate quickly under these circumstances, both from caries of their crowns and their root surfaces and from loss of their periodontal attachment. Implant-based prosthodontics is largely ruled out because implants cannot be placed in a jaw that is full of unerupted teeth, without the removal of a very large number of these teeth. Extensive extraction will take its toll with the postsurgical resorption of additional alveolar bone from the already severely reduced bony ridge. For the most part, therefore, the relative absence of suitable implant sites and the thinness of the mandible itself will rule out the use of implants. Surgical relocation In the search for a non-prosthetic method that utilizes the existing teeth, surgical removal of the supernumerary teeth, followed by careful dissection of the unerupted teeth and their repositioning or transplantation into artificially prepared sockets, has been proposed [5, 21, 22]. However, the long-term results of this method, in the context of its use in cleidocranial dysplasia, and with the presence of multiple impactions and deficient alveolar bone width, have not been investigated. This is an important area for study, since it would give the profession some inkling as to the fate of these teeth in later years. Accordingly, the practitioner seeking appropriate answers is left to ponder whether the transplanted teeth will erupt autonomously and behave like normal teeth or perhaps undergo ankylosis and root resorption in common with other transplanted teeth. These methods all suffer one serious drawback, namely that the results thus achieved deteriorate fairly rapidly and their prognoses are relatively poor. When one considers that treatment for the condition needs to be carried out in the patient’s second decade of life, these modalities must be considered to be of limited value and essentially inadequate to the aim of lasting through to old age. Orthodontics and surgery Before the mid-1960s, while some limited positive results were obtained with orthodontics, the idea was considered to be fanciful and impractical, and was widely derided. Nevertheless, it caught the imagination of a small number of clinicians, and, particularly in the late 1970s and early

1980s, several publications appeared advocating a surgical and orthodontic method. Methods were designed to bring about the eruption of the teeth by extracting the deciduous teeth, surgically removing the unerupted supernumerary teeth and exposing the buried permanent teeth, with or without the use of a surgical pack, depending on the depth of the individual teeth within the tissues [14, 23–25]. The patient was then seen in routine follow-up visits, until the teeth erupted or had reached a sufficiently accessible position, occlusal to the healed gingival tissues, for the application of orthodontic bands or bonded attachments. In other words, assisted eruption was provided only for those teeth that had already partially erupted. For CCD, characterized as it is by a lessened power of eruption, many months will pass before teeth appear and some of the more deeply sited teeth will never erupt. Additional surgical exposure is needed for some of these, but still with no guarantee of success. Immediate bonding and ligation at the time of surgery for these cases was introduced in the literature in the 1980s, when Trimble et al. [26] and Davies et al. [27] each showed a single case in which this was done. The advantage of being able to apply forces to the most intractably impacted teeth is well illustrated in these two cases. The results and prognosis that may be achieved by a method involving surgical removal of the unwanted deciduous and supernumerary teeth, followed by the orthodontically assisted eruption and alignment of the natural permanent teeth, must be viewed as warranting exploitation. What, after all, could be better than to restore the dentition with the patient’s own teeth and with normal alveolar bone support, through the medium of a healthy periodontal ligament? Since the orthodontic literature records few attempts to standardize orthodontic treatment strategy beyond the above-mentioned single case reports, it must be concluded that the orthodontic option had not been exercised for many cases and that there seem to be few centres anywhere in the world where a significant number of patients had been treated. For these reasons, the present state of opinion regarding recommended or appropriate procedure is difficult to assess accurately. Nevertheless, within this modality, three courses of action have been suggested over the years, each based on the experience of the treatment of several cases and each with its own relative merits. These will be referred to as: Toronto–Melbourne approach • the the approach • the Belfast–Hamburg Jerusalem approach. • The Toronto–Melbourne approach

This method was originated by a team from Toronto [14] and was later further developed in Melbourne [24]. Surgical procedures are performed in a stage-by-stage series under

Cleidocranial Dysplasia  377  endotracheal general anaesthesia, with the degree of root development of the permanent teeth dictating the timing of each stage. Thus, initially, the deciduous incisor teeth are extracted at 6 years of age, followed by the deciduous canines and molars at 9–10 years. Supernumerary teeth overlying the crypts of the unerupted permanent teeth are removed, together with substantial amounts of bone to uncover the crowns of the permanent teeth to their maximum diameter. The teeth are left widely exposed. The Melbourne team prefers to expose the incisors at a separate and additional surgical episode, and this is done after the first molar bands are placed following the late eruption of these teeth, which may reach full expression only at about the age of 10–11 years. Surgical packs are used to maintain the patency of the surgical exposure and to safeguard access for eventual bonding of the teeth. The expectation is that, following the removal of the obstructive elements (i.e. the deciduous and supernumerary teeth, together with a liberal amount of bone and soft tissue), the teeth will then erupt of their own accord to a varying degree and over an extended time-frame. When convenient, orthodontic brackets are bonded to individual teeth and these are drawn to a light archwire, which spans the unsupported premolar/canine areas, from the banded molars to one or more anteriorly erupted incisors. Teeth are then drawn to the archwire, depending on their becoming accessible to bracket bonding. Smylski et al. [14] and Hall and Hyland [24] do not propose any special or purpose-designed appliances to deal with the vertical traction that is needed in every area of the mouth, but appear to rely on conventional methods used in routine orthodontic treatment. Limitations In this method, the patient is under treatment for many years, starting from a very early age and requiring several recommended and fairly extensive surgical interventions, followed by several smaller ones for individual teeth. The age of the patient in the early stages and the scope of the surgery are the major determinants as to whether all these interventions should be carried out under general anaesthesia. The deciduous anterior teeth are removed at an early stage in order to encourage the eruption of permanent incisors. Nevertheless, in their subsequent recommendation to fully expose the permanent incisor teeth in a distinct and separate surgical stage, Smylski et al. [14] and Hall and Hyland [24] recognize that spontaneous eruption does not always occur. This means that the patient is anteriorly edentulous for some considerable time. This would seem a high price to pay for what may be undue optimism regarding the potential in cleidocranial dysplasia for normal eruption. In two of the three cases described by Smylski et al. [14] unerupted supernumerary teeth were not present in the anterior segments and the permanent incisor teeth res­

ponded to simple exposure and packing. However, there are many cases where spontaneous eruption does not occur, this being one of the diagnostic criteria of the condition, which may be associated specifically with the frequent presence of supernumerary teeth in this region. The placement of attachments to the deeply sited permanent teeth is not performed at the time of surgery, but some time later, after full healing (by secondary intention) has occurred and the surgical packs have been removed. Thus, at each surgical stage, valuable time is lost between the exposure and the force application needed to encourage the eruption of the teeth. The Belfast–Hamburg approach

Simultaneously, but quite independently, Richardson and Swinson [28] of Belfast and Behlfelt [29] of Hamburg proposed a diametrically opposite method of treatment of the teeth in cleidocranial dysplasia. They recognized that, while there is the need for extensive surgery in these cases, this could be completed at one time, including the extraction of all deciduous and supernumerary teeth and the exposure of all unerupted permanent teeth. This is carried out under general anaesthesia, under operating theatre conditions, and with surgical packs placed over the remaining teeth to encourage epithelialization of the exposed tissue, which is the essence of healing by secondary intention. During the succeeding weeks, these surgical packs remain in place and are perhaps changed over a further quite short period, until brackets may be conveniently bonded to the exposed teeth. This can then be done under what the proponents consider to be more reliable conditions for bonding than those pertaining during the surgical procedure. Whether or not eruption of these teeth occurs without assistance is the subject of some debate, with one source insisting that, while there is apparent improvement, this is due to the radical loss of surrounding soft and hard tissue during the surgical procedure rather than actual vertical dental change [30]. Nevertheless, even with the most favourable and optimistic assessment, there can be no doubt that the eruption will be neither sufficient nor reliable enough to eliminate the need for extrusive mechanics. As with the Toronto– Melbourne approach, appliances consist of molar bands and bonded brackets, with long spans of unsupported and relatively fine archwire used to vertically develop the partially erupted teeth. Limitations By recommending all extractions and exposures at one time, the Belfast–Hamburg surgical policy has clear advantages from the patient’s point of view, although a balance has to be struck in terms of timing. The earlier-developing permanent teeth, particularly the incisors, should not be exposed too late in their development to lose any eruptive potential that they may have, while the later-developing

378  Orthodontic Treatment of Impacted Teeth teeth should not be exposed too early when their roots are insufficiently developed. Accordingly, the Belfast team [28] recommends that the one-time, comprehensive, surgical intervention be performed at age 12–14 years. The immediate advantage of this policy is very clear and encouraging, although its drawbacks are of considerable consequence and not so obvious. By delaying treatment until this late age, the teeth of the normal series will have been held deep down in basal bone by the supernumerary teeth, particularly in the lateral incisor/canine/premolar area, for an extended period of time. Their roots will have reached an advanced stage of development in these cramped circumstances, which is likely to exaggerate the tendency for a stunted, tortuous and distorted root morphology [31]. Removal of the unwanted extra teeth at this late stage will relieve the impaction of the permanent teeth of the normal series, but it will do so at a time when they exhibit even less potential for spontaneous eruption, particularly in the incisor region, since the root apices will already have been completed. During growth in a normal child and with the eruption of permanent teeth, the vertical development of the alveolar processes that occurs makes a significant contribution to the height of the lower face. It also leads to the establishment of deep vestibular and lingual sulci, with a clear differentiation of wide zones of oral mucosa and attached gingiva. In the untreated cleidocranial dysplasia patient, vertical growth of the alveolar bone appears to be markedly diminished. This brings about the typically reduced height of the lower third of the face that is so frequently a feature of the condition. Thus, with the late removal of the unwanted deciduous and supernumerary teeth at a time when most of the patient’s growth has already occurred, the ultimate vertical alveolar growth that accompanies the erupting permanent teeth will be correspondingly less, leaving a shallower sulcus, an absence or reduced width of attached gingiva and an incompletely vertically developed lower third of the face. Furthermore, and in addition to removing the unwanted supernumerary teeth, it is necessary to gain access to the canine and premolar teeth of the normal series and to expose them widely. When the procedure is performed at this late stage, these target teeth are very deeply situated, often with their developing root apices close to the lower border of the mandible or the floor of the nose and maxillary sinus. This necessitates the removal of considerable quantities of bone [14] and, as recommended by several authors, the placement of a surgical pack over and around the crowns and necks of the teeth to prevent bony healingover and to encourage spontaneous eruption. This packing procedure will markedly delay healing and is designed to prevent the reparative filling-in of bone. It is difficult under these circumstances to avoid pushing the pack into the area of the cemento-enamel junction (CEJ), which will inevitably lead to a poor periodontal prognosis for the finally

erupted tooth, with an exposed CEJ and lessened bone support [32]. The frequent need to change packs over a long period incurs pain, discomfort and nuisance, difficulty in maintaining oral hygiene and a limitation of normal function, with a prolonged bad taste and odour in the mouth due to the unhygienic circumstances. From the surgeon’s point of view, this entails seeing the patient for many timeconsuming appointments. There is no active encouragement of eruption until brackets may be successfully bonded and traction applied, in a case already afflicted by slow or non-eruption as a characteristic of the disease. Thus, at an age when facial appearance is very important, the patient will spend an unacceptably long time without teeth. Furthermore, bone regeneration will have been retarded by the use of a method involving healing by secondary intention [33]. Eruption is thus delayed, and a growing over of the soft tissues, to re-cover the deeper and newly exposed teeth, may still occur. From the discussion of these two approaches, it becomes clear that treatment could be vastly improved if the placement of attachments and the initial application of extru­ sive traction could be included as two of the functions to be addressed during the surgical procedure. This creates several formidable obstacles, the largest of which is the ability of the surgeon to create a series of microenvironments whereby a small area of the crown of each of the teeth is exposed and conditions of haemostasis and isolation prepared, to permit the delicate attachment bonding procedure. There can be no question that the skills needed to achieve this type of complicated treatment protocol require more than one pair of hands and more than one qualified operator in the operating theatre. The ideal situation is the interdisciplinary cooperation of the surgeon with the orthodontist at this critical time. As pointed out in Chapter 3 and in several subsequent chapters, there are enormous advantages to be gained by the presence of the orthodontist at this crucial stage, which has a long-term bearing on the efficacy of the later orthodontic resolution of impacted teeth in general. If this is true of the treatment of a single impacted tooth, then its benefit is exponentially more valuable in relation to multiple impactions, many of which are often located deep in basal bone. Without the placement of attachments at the time of surgery, access to the unerupted teeth must be guaranteed by the surgeon performing wide opening and radical bone resection, with the placement of surgical packs. With attachment placement, a conservative surgical policy is possible – only enough bone is removed to allow access for the placement of a small eyelet attachment on the minimally exposed tooth surface. The surgery may then be aimed at preserving rather than removing bone, since the presence of bone in the eruption path does not hinder mechanically encouraged eruption of the teeth, in these cases or in

Cleidocranial Dysplasia  379  general. Its lack would be a greater drawback in terms of the eventual degree of bone support and thus of the periodontal prognosis of the erupted teeth [32]. It has been reported [14] that denser alveolar bone is present in cleidocranial dysplasia. We have not found abnormal bone in any of the cases in our care, although the observer could understandably be misled by the fact that cortical bone is found, to the relative exclusion of spongiosum. It should be remembered that the impaction of many teeth within the jaws takes up much of the volume within the body of the mandible where spongiosum would normally be present. Thus, while cortical bone encompasses all these teeth and is present in normal amounts, spongiosum is sparse. The Jerusalem approach

This method [34, 35] was presented for the first time at the same forum as the Belfast–Hamburg approach described above [36]. Its modus operandi is quite different from either of the two other approaches. The Jerusalem approach is based on a rationale that is related to the abnormal dental development of the patient and on the factors that produce it. This comprehensive approach to treatment addresses the following points: recognition of the clinical features of the facial, oral and • dento-alveolar structures in the disease; the surgical measures • to the areas concerned;that are required to provide access the need for an orthodontic strategy to enable the appli• cation of extrusive mechanics to the buried teeth in an efficient and reliable manner; attending to the patient’s psychological well-being by focusing the earliest stages of treatment on the resolution of the incisor impactions.

•

Recognition of the clinical features Cleidocranial dysplasia patients exhibit each of the following features to a variable degree: 1. non-resorption of deciduous teeth roots; 2. the presence of supernumerary teeth, markedly displacing the developing permanent teeth and providing a physical barrier to their eruption; 3. lessened eruptive force, although eruptive movements are evident; 4. poor vertical development of alveolar bone, as witnessed by a shallow sulcus, a reduced height of the lower face and a class 3 skeletal tendency, due to an underdeveloped maxilla and to a counter-clockwise mandibular rotation; 5. late but normal and unhindered eruption of first and, much later, second permanent molars in both arches; 6. late dental development, as judged by the root development of the permanent teeth, whether erupted or unerupted – a 12-year-old patient will typically show a

dental age more appropriate to that of a 9-year-old [24, 35, 37]. Surgical therapeutic measures The timing regarding the actual exposure of the permanent teeth is critical, and only two interventions are planned at distinct points in time, depending on the extent of root development, as follows. Intervention 1

At the dental age of 7–8 years, the anterior deciduous teeth, together with all the supernumerary teeth, in the anterior and, as far as reasonably possible, posterior areas are extracted. However, only the crowns of the anterior permanent teeth whose roots are sufficiently developed (twothirds of their expected length) are surgically exposed. Attachments are placed immediately and surgical flaps fully closed. Given the usual lateness in development of the dentition in these cases, the chronological age of the patient at this stage is usually around 10–12 years. At this time, the canine and premolar teeth are at an early stage of development, with their roots less than half their expected final length. The surgical intervention in the posterior region is therefore limited to removal of supernumerary teeth. Actual exposure of the developmentally immature posterior teeth of the permanent series is not undertaken and, most importantly, their dental follicles are left intact until later. If there are no supernumerary teeth in the posterior areas, the deciduous teeth are left in place. Intervention 2

The dental age of 10–11 years (chronological age 13–15 years) is the most appropriate time for the second intervention, because the root development of the posterior successional teeth will be sufficiently well advanced and eruption and alignment of the incisor teeth will have been achieved. This intervention involves the exposure of the crowns of the canines and premolars in both dental arches and the immediate placement of orthodontic attachments. The special requirements of the surgical procedure relate to the conservation of bone in general and of the cortical part of the bone in particular. Removal of the unerupted supernumerary teeth with a minimum of buccal plate of bone creates enough space around the crowns of the impacted permanent teeth of the normal series to allow the immediate bonding of small eyelet attachments. The lingual plate is left intact and at its original height. Maxillary second premolars may require a palatal approach, in which case the buccal plate should be left intact. Bone that covers the occlusal surface of the crowns of deeply impacted teeth is not removed, and the dental follicle is untouched except for the small window opening in the immediate area of attachment bonding. A wide soft tissue flap exposing the surgical field is advised to enable good vision and access and to help in

380  Orthodontic Treatment of Impacted Teeth maintaining the conservative attitude to the removal of bone. The partial-thickness muco-gingival flaps are finally replaced intact and sutured back, without the use of packs, in the manner of primary soft tissue closure [32, 36–40]. Immediately following the first intervention, it becomes necessary to supplement the eruptive force of the incisors. In this way, the vertical migration of the teeth that rapidly occurs brings with it a pronounced vertical development of the alveolar bone [14]. This will have been planned for the stage of dental development when root length is between half and three-quarters of its final expected form, which corresponds to the stage of development at which teeth normally erupt [41]. Similarly, occlusally directed forces are applied to the posterior teeth immediately following the second intervention. Orthodontic strategy In the broad overview, the provision of space within the arch is made by appliance-generated antero-posterior expansion of posterior-versus-anterior erupted teeth [21], while the removal of deciduous and supernumerary teeth provides space in the vertical plane. In this way, and while space is being provided, self-realization of any eruptive potential that the permanent teeth may possess is permitted, to present the opportunity for them to migrate towards the occlusal plane and to take up a more normal developmental position within the alveolus. This seems to occur to a varying degree and has the advantage of allowing the roots to develop in uncramped circumstances, thereby leading to the acquisition of more normal root morphology [33]. However, it is important to emphasize that no reliance is placed on spontaneous eruption of these teeth [14], although should this occur, it is only to be welcomed and will simplify the treatment plan. However, the Jerusalem approach has been formulated to combat the worst eventuality: non-eruption. From the point of view of the orthodontic mechano-therapy, achieving efficient force application in an appropriate direction for each tooth, requires examination of the following points. There must be a sufficient number of erupted anchor • teeth in the mouth to act as a base from which forces may be generated. As we have already pointed out, the permanent molars usually erupt without help, and one or two incisors may also be visible. One has to design a rigid appliance frame that will endure chewing and other functional and para-functional movements that may be expected to occur during daily oral function, considering the long spans of free, unattached and unprotected archwire mesial to the two erupted anchor molar teeth in each jaw. Individual and groups of unerupted teeth must be subjected to light continuous extrusive forces. Appliance design has to feature sufficient versatility to enable it to:

•

• •

–  apply vertical extrusive forces to erupt the impacted teeth rapidly; – open spaces between recently erupted teeth, to provide room for other unerupted teeth and to establish interproximal contacts and archform; – bring these teeth into occlusion and to upright their roots. And all this with only minor alterations! The patient’s psychological well-being In Chapter 5, we pointed out that it is unacceptable to leave even the youngest patient without front teeth for an extended period of time, and that it is important to make the child aware that efforts are being made to rectify such a situation speedily. The physical obstacles to eruption (i.e. the deciduous and supernumerary teeth) must be removed in order to facilitate the eruption of the anterior teeth. Proper timing is critical. This should only be done at the age when the permanent incisor teeth indicate adequate root development for eruption and only when an appliance is in place to actively supplement their limited eruption potential.

Dental crowding When studying the radiographs of an untreated cleidocranial dysplasia patient, one is immediately struck by the intra-bony crowding provided by the large number of unerupted permanent teeth (those of the normal series and the supernumeraries). During surgery, and after all of the superfluous deciduous and supernumerary teeth have been removed, the surgeon and the orthodontist will view the open surgical field and, given the relatively underdeveloped alveolar processes, find it difficult to see how it is possible to fit all the remaining permanent teeth into the dental arch and in full alignment. On the basis of this ‘spot’ diagnosis, the orthodontist will be tempted to advise the oral surgeon to take advantage of the prevailing general anaesthetic to remove a premolar tooth in each quadrant of the mouth, in what would appear to be a logical step necessary to reduce the apparent crowding. However, for most cases, this step would be regretted later when the subsequent size and form of the alveolar processes, which may be developed as a by-product of the mechanical eruption of the teeth, become evident. Initially, the appliance-generated eruption of the anterior teeth brings the teeth into the mouth with a pronounced lingual tipping of their long axes. This is due to the influence of purely vertical forces that will have been brought to bear on the permanent incisors, whose developmental position is very much lingually placed and apical to the recently extracted deciduous incisors. For this reason, the permanent incisors must be tipped labially to create a normal archform and to provide a more

Cleidocranial Dysplasia  381  procumbent support for the lips. This will contribute much additional space in the dental arches for the premolar and canine teeth, and will be instrumental in significantly eliminating the dental crowding and the patient’s edentulous appearance. It is only after complete or almost complete eruption has occurred that a decision should be made as to whether extractions are needed. Our limited experience has shown that, in these younger patients, extractions usually are not needed, and that adequate space for alignment of all the teeth anterior to the first molars may easily be provided.

Retention of the treated result Once the permanent teeth have all reached their final positions in the arch, the removal of the fixed appliances will not usually be accompanied by a loss of vertical height of these teeth, despite the fact that their vertical positions will have changed so dramatically over the treatment period. The lateral width of the two arches will have been set initially by the first permanent molars and the over-retained deciduous teeth. The use of fixed lingual arches during treatment will have allowed good control against any change in this dimension. Therefore, the orthodontist may confidently expect no natural post-treatment alteration of the arch width. However, in the event of maxillary narrowness, rapid suture-splitting expansion may be performed early on in the treatment and its results maintained throughout the treatment, initially by a transpalatal soldered bar and, thereafter, by the archform of the successive labial archwires. Subsequent post-treatment loss of width is generally marginal. The only dilemmas of any consequence in the context of retention relate to the labio-lingual post-treatment position of the incisors of both jaws and to those teeth that have undergone rotational orthodontic movement during treatment. It is axiomatic to say that proper labio-lingual positioning of the anterior teeth in any patient is dependent on the muscular balance between the lips and the tongue. Teeth placed too far labially or lingually will inevitably be pushed by the lips or tongue in the opposite direction when all retaining devices are removed. During the orthodontic treatment of the normal patient and in the interests of stability, the positions of adjacent teeth are often used as a measure against which the displaced teeth should be moved to achieve the desired alignment. Alternatively, cephalometric standards may be preferred against which to compare the dentition, such as the lower incisal edges vis-à-vis the A–Po line [42]. With the cleidocranial dysplasia patient, there is no scientific way to judge the ‘biologically correct’ and therefore stable position of the incisors. Nor are there any published cephalometric data on a large group of treated and postretention cleidocranial dysplasia patients to help establish

such norms. By no means may the cephalometric values of these patients be compared with the average values found in the various growth studies that have been carried out with samples of normal patients. Consequently, the use of Holdaway or Ricketts analyses and a growth prediction analysis, as proposed elsewhere [24], is invalid and highly misleading. The orthodontist can never be sure of the stability of the final result in this aspect of the treatment, and some form of long-term retention will usually be advisable. This being so, we have adopted the view that the incisors should be brought well forward, extruded below the upper lip, so that 2 or 3 mm of their incisal edges are clearly visible at rest, and the recommendations of Zachrisson regarding the so-called ‘smile line’ be followed [43, 44] to slightly over-compensate to some degree for the years that the patient has lived with very short and largely unseen teeth. When only deciduous teeth were present, or in the initial stages of treatment, the patient’s social interaction with others would have been dictated by a desire to mask the missing anterior teeth, and he/she may have adopted unnaturally unwelcoming and unsmiling facial expressions and a reserved attitude. Once dental alignment is complete and appliances removed, a positive and dramatic psychological change in the patient’s attitude to life seems to occur and, from then on, many treated cleidocranial dysplasia patients seem to have a permanent smile on their faces, consciously and deliberately displaying their newfound teeth! They adopt an optimistic outlook on life and become much more open in their dayto-day contact with others. After a short period of time with conventional removable retainers, our practice has been to prepare and apply fixed multi-stranded bonded retainers to the maxillary and mandibular six or eight anterior teeth [45–48]. These will then hold the labio-lingual positions of all the anterior teeth, as well as preventing rotational relapse. The conventional removable retainers may then be discarded.

The Jerusalem approach in clinical practice Patients who are suspected to be suffering from cleidocranial dysplasia are referred to us through different agencies, including the various medical specialties and general dental practitioners or dental specialists. A small proportion also arrive on their own initiative, requesting advice and help in the search for a solution to the presence of ‘very small teeth’ or to their ‘toothless’ appearance. CCD individuals vary widely in the expression of the phenotypal features, with some exhibiting a broad spectrum of the associated characteristics and others with relatively few. Some may even escape detection and diagnosis until early adolescence. In order to confirm that the patient does indeed suffer from cleidocranial dysplasia, our diagnostic routine has come to include:

382  Orthodontic Treatment of Impacted Teeth a family history to check for parents or other rela­ • tives who may have been diagnosed with cleidocranial dysplasia; a clinical examination in search of the general characteristics of the condition, which takes in the form of the cranium, face and clavicles, including the mobility of the shoulders; an intra-oral examination to relate the eruption status of the dentition vis-à-vis the patient’s chronological age; a radiographic evaluation, which plays a critical role in the confirmation of the clinical diagnosis, includes a chest X-ray and antero-posterior and lateral skull radiographs, which are performed in a cephalostat. At the same time, a panoramic radiograph is studied and supplemented with periapical and occlusal views, as required.

• • •

Following the establishment of the tentative diagnosis, a genetic analysis should be undertaken. It is recommended that a small blood sample be taken and forwarded to a laboratory specializing in dealing with the gene specific to CCD, namely RUNX2. The laboratory will extract the DNA from the blood sample and then perform the sequencing. There is a 60–70% likelihood of finding the gene although, as has been pointed out at the beginning of this chapter, its absence does not mean that the disease is not present. Once the diagnosis has been confirmed, genetic counselling is offered to the parents regarding their own future offspring, but more particularly regarding future offspring of the affected child. An important part of the geneticist’s examination will include gathering information about relatives and the possibility that other, more distant family members may be similarly affected. Treatment of the oro-facial characteristics of the condition will involve the talents of a team of three dental specialists: the paedodontist, the orthodontist and the oral and maxillofacial surgeon. They will need to work in close collaboration and the first stage may begin immediately. Stage 1: Assuring the health of the dentition Treatment of the cleidocranial dysplasia patient will necessitate the wearing of orthodontic appliances for several years. Therefore, an essential requirement in all cases is that the health of the dentition be guaranteed by proper oral hygiene instruction, with follow-up to check that an adequate level of compliance is attained. Appropriate use of fissure sealants and fluoride applications is recommended. Carious teeth will need to be treated, but, in order for the paedodontist to be in a position to decide on the type of restoration indicated, the timing of the extraction of the remaining deciduous teeth will need to be determined at the outset. Stage 2: Vertical correction in the incisor region It has already been emphasized that there is a lag in the dental development of about three years in relation to the

child’s chronology. Thus, for most cleidocranial dysplasia cases, it will not be until about 10 years of age that the spontaneous and unimpaired eruption of all first permanent molars will herald the dental age of 7–8 years. Sometimes, one or more of the permanent incisors will also have erupted, but the following description of the technique will assume the least favourable initial scenario and we shall assume that no permanent anterior teeth are present. Orthodontics

Plain orthodontic bands are fitted on the erupted first molars (Figure 14.8) and an impression is taken of each dental arch. The bands are then carefully removed from the teeth, re-seated in the impressions and a model is cast. Heavy soldered palatal and lingual arches are prepared on the two models, and single soldered buccal tubes (0.036 in round) are oriented such that they run mesially, close to the buccal side of the deciduous teeth, parallel to the occlusal plane. A lingually displaced first permanent molar may need to be aligned buccally with a removable appliance first in order to be able to align the buccal tubes accurately as described, since the efficient working of the appliance depends on this. A heavy ‘incisor-erupting’ archwire is prepared for each arch in advance (Figure 14.8f), and its function is to achieve a correction in the vertical plane. This archwire is made of 0.036 in round wire, which slots into the buccal molar tubes up to a predetermined bayonet bend on each side. This holds the wire 2–3 mm labial to the anterior teeth and 3–4 mm gingival to the occlusal plane. In the canine area, an S-shaped hook is soldered, with its mesially pointing extremity on the occlusal side and the distally pointing extremity gingival. In the midline area, a small finewire frame is also soldered and points towards the sulcus depth. An ‘incisor-aligning’ archwire is also prepared in advance, although it will not be put to use until all the permanent incisors have been fully erupted. This consists of 0.020 in internal-diameter tube (0.036 in external diameter) sidepieces, which freely slide accurately into the 0.036 in buccal tubes, without allowing lateral or vertical play. The tubes are cut so that their mesial extremity is in line with the distal of the deciduous canine. A length of 0.0155 in or 0.0175 in multi-stranded wire or of 0.016 in or 0.018 in nickel–titanium wire is then drawn into the buccal sidepiece tubes, and is made to ‘friction-fit’ by incorporating three or four sharp bends in that part of the wire. This updated version of Johnson’s twin-wire arch [49, 50] is placed to one side until it is needed at that later stage, when it will be used to achieve correction of the alignment of the teeth in the horizontal plane. The reader is referred to Chapter 5 for a full description of the Johnson twin-wire appliance.

Cleidocranial Dysplasia  383 

(b)

(a)

(d)

(c)

(e) Fig. 14.8  (a) Plain bands have been adapted to the maxillary left second deciduous molar and the first permanent molars in the other three quadrants. (b) Upper (shown here) and lower compound impressions are made. (c) The bands are removed from the mouth and carefully replaced in the impression. The bands are then partially filled with wax, before a model is poured. (d) The cast model with accurately located and stabilized molar bands. (e) The occlusal view of the mandibular model shows right and left tubes converging in the midline and the lingual arch in place. (f) The heavy ‘incisor-erupting’ archwire is slotted into the molar tubes. Note the S-shaped hook soldered in the canine area and the anteriorly soldered fine-wire frame. (g) Disassembled mandibular appliance ready for intra-oral placement. (h, i) The appliances cemented in the mouth.

384  Orthodontic Treatment of Impacted Teeth

(f)

(g)

(h)

(i) Fig. 14.8  (Continued )

Surgery

The patient is now ready for the first surgical intervention (Figures 14.8 and 14.9), which must be performed under endotracheal general anaesthesia. At the completion of this episode the patient will have lost all of the anterior deciduous teeth and will also have had the unerupted supernumerary teeth removed in both arches. Fine pigtail ligatures will have been placed in the eyelet attachments bonded to the incisor teeth (ideally by the orthodontist) and, following suturing of the flaps back to their original place, these will be the only link between the invisible unerupted permanent teeth and the exterior (Figure 14.10). Deciduous teeth not associated with supernumerary teeth are generally left until the next surgical stage. Under these circumstances, this surgical procedure will generally take between 3 and 5 hours, depending on the number of supernumerary teeth removed and on the number of unerupted permanent teeth that need to be exposed, with the placement of attachments. Orthodontics

Still under the endotracheal anaesthesia in the operating theatre, the orthodontist replaces the prepared ‘incisorerupting’ archwire in the buccal tubes. The archwire may be secured by drawing an elastic chain between the distal

of the buccal tubes to the mesially pointing extremity of the S-hook, although this is rarely necessary. The anterior portion of the archwire is raised with light finger pressure and engaged by looping the pigtail ligatures around it. Since these pigtails are tied directly to the buried incisor teeth, this displacement of the archwire elicits a vertical extruding force which is shared by the unerupted teeth (Figure 14.12c). The extrusive force and its range are very easily measured and, therefore, controllable to within appropriate levels. This force generates a rapid response of the teeth, as witnessed by elongation of the pigtail ligatures over a period of a few weeks. By displacing the archwire apically and then rolling up the pigtail around it, extrusive pressure may be simply and efficiently reapplied over several visits, until eruption occurs. This procedure is performed simultaneously in both arches in order that the two may then subsequently be treated more efficiently. To support the orthodontic anchorage, a single, large and fine-gauge elastic should be placed in the form of a rectangle, engaging the distally-pointing, soldered hooks in the canine area on each side of the archwires in both jaws. When the elastic is placed, its midline portion is laid over the soldered vertical frame of the archwire in order that tissue impingement may be avoided

Cleidocranial Dysplasia  385 

(a)

(c)

(b)

(d)

Fig. 14.9  A 14-year-old patient. (a–c) Intra-oral views of initial condition. (d) Anterior intra-oral view of appliances in place.

(a)

(c)

(b)

Fig. 14.10  The same patient as in Figure 14.9. (a) Four maxillary incisors have been exposed and attachments bonded. (b) Six mandibular anterior teeth have been exposed and attachments bonded. The exposed chin button and the lingual arch indicate the depth of these teeth. (c) The ‘incisor-erupting’ archwire is replaced when full-flap suturing is completed, and the steel ligature pigtails are made to ensnare the archwire, which has been displaced superiorly by light finger pressure.

386  Orthodontic Treatment of Impacted Teeth

(a)

(a)

(b) (b)

(c) Fig. 14.11  The same patient as in Figures 14.9 and 14.10. (a) At five weeks post-surgery, a very light anterior ‘box elastic’ is placed on the distally pointing element of the S-hooks in the canine areas to enhance the anchorage. Note the use of the midline frames to prevent tissue impingement. (b) At nine weeks post-surgery, five incisors have erupted and the archwires have been disengaged to increase their deflection. (c) Re-engaging the archwires illustrates their range of effectiveness.

(c) Fig. 14.12  The same patient as in Figures 14.9–14.11. (a–c) At 6.5 months post-surgery, all incisors have erupted. Conventional brackets have been substituted for the eyelet attachments, and the ‘incisor-aligning’ archwires are in place. Note the extrusive component generated by these archwires.

Stage 3: horizontal correction in the incisor region Orthodontics

(Figure 14.11). This anterior vertical elastic provides an intermaxillary vertical force to each archwire. This means that the forces used to erupt teeth in one jaw are anchored by the reactive force that is producing the eruption of the teeth in the opposite jaw.

The incisors erupt relatively quickly and with a strong lingual inclination, in general. At that point, their eyelets should be replaced by the orthodontic bracket of the orthodontist’s choice, which should be sited in the routine manner (Figure 14.12). The prepared ‘incisor-

Cleidocranial Dysplasia  387 

(a)

(b)

(c)

(d)

(e)

Fig. 14.13  The same patient as in Figures 14.9–14.12. (a, b) At 15 months post-surgery, the incisors have been moved labially, aligned and a positive overbite– overjet relationship has been established. In this case, the mandibular canines were included in this stage of treatment. Note the severe mesial root displacement of these teeth. (c) The occlusal view of the mandibular anterior teeth indicates gross labio-lingual displacement of the roots of the lateral incisors and canines. (d, e) Following four months of further treatment, the root displacements have been corrected. This was done during a waiting period for adequate premolar development, to allow the initiation of the second surgical intervention.

aligning’ archwire is then ligated into place, where its first task will be to undertake the levelling and alignment phase of treatment (i.e. incisor height, rotation and uprighting). With proper buccal tube orientation at the outset, the long buccal tube side-pieces maintain the achieved vertical extrusion, while providing stability and resistance to distortion. The light anterior vertical elastics may be attached to the lateral incisor brackets to continue the vertical extrusive force, if and when necessary.

As levelling proceeds, the light wire middle portion of the ‘incisor-aligning’ archwire may be substituted for heavier and thicker stainless steel wires (Figure 14.13) until an 0.018 in or 0.020 in wire is in place, using the same side-pieces. At this point, an expanded coil spring is placed on the side-pieces, which now have a ‘stop’ soldered or welded to their mesial end. When the side-pieces are replaced in the buccal tubes, the coil spring is compressed between the buccal tube and the mesial stop, which displaces the archwire forwards. The archwire is ligated into

388  Orthodontic Treatment of Impacted Teeth the anterior brackets under pressure. The compressed coil spring is now producing an antero-posterior expansion force, acting between the first molars and the incisors. This rapidly tips the incisors to a more normal labial inclination and, at the same time lengthens the arch in the buccal region to subsequently accept the unerupted canine and premolar teeth. Archform will be greatly enhanced and the patient’s appearance will, for the first time, begin to improve markedly. An estimate of treatment time up to this point (stages 2 and 3) would be between 9 and 18 months. New radiographs should now be taken of the unerupted canines and premolars (Figure 14.14) to assess the degree of their root development and to reassess their vertical location within the alveolus. Absence or earlier removal of super­ numerary teeth in this area, together with an increase of space in the arch and the passage of time, may have led to an improvement in their position, which should be recorded.

(a)

Stage 4: vertical correction in the posterior region Surgery

The second surgical intervention (Figure 14.15a–d) is performed at dental age 10–11 years and will leave the patient devoid of any remaining deciduous teeth that had been left undisturbed in the first intervention. The surgical flaps will have been replaced to completely cover the eyelet attachments bonded to the buccal side of the unerupted permanent teeth, although it is unlikely that full closure of the sockets of the deciduous teeth will be possible. Stainless steel pigtail ligatures will be visible emanating superiorly through these sockets. Strictly speaking, the scope of this surgical procedure, potentially involving 12 teeth (eight premolars and four canines in the four quadrants) is large enough to warrant a repetition of endotracheal anaesthesia and operating theatre conditions. However, in the more favourable cases, spontaneous eruptive movement of the unerupted teeth will have occurred since treatment was initiated and several teeth may have partially erupted. This may encourage the oral surgeon to prefer to perform the remaining exposures under local anaesthetic one or two quadrants at a time and with an open exposure technique. Orthodontics

The buccal side-pieces of the modified Johnson twin wire arch, with its more rigid 0.020 in middle section, are now used as a rigid beam, from which elastic thread may be tied, under pressure, to the rolled-up pigtail ligatures of the unerupted premolar and canine teeth. Re-ligation will be needed at frequent intervals because of the relatively poor range of action of the elastic thread. Alternatively, this composite archwire may be discarded in favour of a plain 0.018

(b)

(c) Fig. 14.14  The same patient as in Figures 14.9–14.13. (a) A panoramic view taken 10 months pre-surgery. (b) A similar view six months post-surgery. (c) A similar view 21 months post-surgery.

Cleidocranial Dysplasia  389 

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 14.15  The posterior region. (a–d) At surgery, exposure of the premolars and canines. Eyelet attachments have been bonded on the maxillary teeth and full closure was performed. (e, f) Four months post-surgery, vertically offset 0.018 in round archwires are used to erupt the teeth, with anterior vertical intermaxillary elastics maintaining the vertical dimension and reinforcing the anchorage in both arches. (g–i) Immediately prior to appliance removal. (j–p) Immediately after appliance removal, with 3–3 twistflex splints placed the same day. Note the pitting of the enamel of the incisors and several other teeth. (q–u) At 18 months follow-up. (v, w) Panoramic views at appliance removal and at 18 months after completion of treatment, respectively. Note the steady progress in the spontaneous second molar eruption and development of third molars. (x, y) Profile views of the face before and after treatment (5.11 years), showing an atypical exaggerated growth of the mid-face.

390  Orthodontic Treatment of Impacted Teeth

(g)

(i)

(h)

(k)

(j)

(l)

(n) (m) Fig. 14.15  (Continued )

Cleidocranial Dysplasia  391 

(o)

(p)

(q)

(r)

(s)

(t)

(u)

(v)

Fig. 14.15  (Continued )

392  Orthodontic Treatment of Impacted Teeth tion may now be performed, if desired, together with the uprighting and torqueing movement needed to produce optimal alignment. Standard finishing procedures that are de rigueur in the protocol in any routine orthodontic case now become possible and are carried out in the usual way. It is important to note that in many cases the teeth had earlier been markedly displaced by the physical presence of supernumerary teeth and, as a result, may need degrees of uprighting and torqueing movements almost never seen in unaffected individuals. These movements take much time even when an efficient root-moving mechanism is used because of the distances that the root apices have to travel through alveolar bone in order for the tooth to become optimally sited. Under these circumstances, the orthodontist is encouraged to use auxiliary springs on rigid base arches, since they possess a greater range of action with more controllable forces, while the base arch holds the overall archform.

(w)

(x)

(y)

Fig. 14.15  (Continued )

in or 0.020 in round archwire, stretching from molar to molar (Figure 14.15e). Its long span, between lateral incisor and first molar, is flexible in the vertical plane, and the pigtail ligatures may be turned over to engage the wire under light extrusive tension (Figure 14.15e). Stage 4 is expected to be completed within 5–12 months. Stage 5: correction of the axial orientation of the roots of the teeth Orthodontics

Much mesio-distal uprighting of the anterior teeth may have already occurred in the earlier stages of treatment, although root-torqueing movements will usually need to await the use of a full rectangular arch. However, given the amount of root displacement seen in these cases, it is most likely that stage 5 will see these movements still being applied to the anterior teeth, while uprighting and rotating movements will need to be initiated in the premolar/canine regions, following the substitution of the eyelets with standard brackets (Figure 14.15g–i). At this stage, the palatal and lingual heavy arches are no longer needed, while rectangular tubes on the molars now become an essential aid to the remaining finishing procedures. The molar bands are removed and new bands adapted, with rectangular tubes. Molar expansion or rota-

Treatment follow-up and the eruption of second molars For most patients, the stages of whose treatment have been undertaken at the recommended ages and developmental milestones, the protocol described above will be completed before the eruption of the second molars. It was pointed out at the beginning of this chapter that, in cleidocranial dysplasia, permanent molars generally erupt under their own steam and in accordance with the patient’s dental age. This is largely true of both the first and second molars. This being so, we would not expect to see eruption of the second molars before the age of 15–16 years, with a normal range of +2 years – hopefully after completion of the overall treatment of the remainder of the teeth. A new panoramic radiographic view at this time (Figure 14.15v, w) will usually show the eruption of the second molars to have progressed markedly, with the teeth heading towards their place in the arch. The film should also be scanned for signs of the possible early development of new supernumerary teeth. If all appears well, orthodontic treatment should not be prolonged until the second molars erupt and the appliances should be removed. The second molars may still take many months, stretching into a year or two, before intra-oral signs of eruption are noted. For as long as unerupted supernumerary teeth do not interfere with the eruption of teeth of the normal series and do not threaten to disturb an existing dental alignment and occlusion, the decision whether or not to extract them should be made by a competent oral surgeon and not by the orthodontist. Therefore, if newly developing supernumerary teeth are identified on this new film, a surgical opinion should be sought regarding the need and the timing for their removal.

Cleidocranial Dysplasia  393  Supplemental molars From time to time, supplemental molars are seen in a small number of CCD cases and these may occur in what appears to be a simple distal extension of the dental lamina, to produce a fourth molar which is located distal to the unerupted third molar, in either jaw. Their presence will not adversely affect the autonomous eruption of the second molars. However, supernumerary molars may occasionally be seen lateral, medial or superior to the unerupted second molar, when it is almost certain to impede eruption. The difference between the supernumerary tooth and the normal second molar will usually be decided by the root development of the teeth. Supernu­ merary teeth usually develop much later than teeth of the normal series and, as such, will have rudimentary root development which lags far behind the dental age of the rest of the dentition. Furthermore, when fully developed, the supernumerary teeth will often exhibit considerable root stunting. When eruption of the second molars is obstructed by these unerupted teeth, surgical removal is justified, following which some improvement in the eruption status of the second molars is very likely. It is therefore wise to review the case on a half-yearly recall basis, for at least a year or more, before advising further treatment to augment the limited eruptive potential of the teeth. Retention Retention procedures are similar to those used in any orthodontic case. It should be remembered that beautifully aligned teeth need to be retained long term. All teeth move during the life of normal individuals and of CCD patients, whether or not orthodontic treatment has been carried out. The degree of immediate post-treatment movement is always considerably greater than after some months in retention, and it is also greater for teeth that have been moved over large distances or had been initially rotated. For this and other reasons, the long-term use of anterior lingual bonded retainers is advised [46–48].

Treatment experience To date, over 40 cleidocranial dysplasia patients have been treated or are still in the various stages of comprehensive orthodontic/surgical treatment at our centre (Figures 14.16, 14.17). It is from their treatment that the Jerusalem approach has been formulated and refined over the years. In the published reports that described the treatment of the first 16 patients in this series [34, 35] three had no supernumerary teeth and one had a congenitally miss­ ing premolar. Seven patients had four supernumerary teeth or fewer and four others had six, eight, 10 and 27,

respectively. Treatment of the remaining case was initi­ ated elsewhere, and information was not available for that patient. Gathering information from all the cases that we have seen over the years, most supernumerary teeth were found to be recognizable supplemental teeth, similar to those adjacent to them (i.e. with the characteristic morphology of incisors, canines, premolars or molars). In the anterior region of the maxilla, occasional barrel-shaped supernumerary teeth are relatively frequent. The presence of supplemental teeth has been helpful in permitting a choice of teeth for extraction, since a displaced tooth may be removed and the better placed adjacent tooth aligned in its place without regard to distinguishing which is the abnormal tooth, provided the root development is potentially adequate. Without exception, the dental age range of our cases lagged between 2.5 and 4 years behind their chronological ages. Spontaneously erupted first permanent molars have been seen in all but two cases, which were associated with supernumerary molar teeth. Unlike other teeth, the permanent molars appear to erupt spontaneously in cleidocranial dysplasia, and it seems reasonable to assume that, in the absence of these obstructions, the molars of these two patients would also have erupted normally. Following the removal of the supernumerary teeth, in both of these cases the unerupted molars were exposed and a surgical pack placed to encourage healing by secondary intention and to maintain the patency of the exposure. The teeth erupted spontaneously after this preparatory surgical procedure and both patients were then treated with the above protocol. A single erupted maxillary first premolar was present in three patients whose deciduous predecessor had had an apical abscess. The shape of the well-developed permanent teeth, while clearly recognizable and classifiable into their different tooth types, showed labial concavities in the incisors, broad mesial and distal ridges on the labial and lingual aspects of both canines and incisors, and mesio-distally wide and bucco-lingually narrow widths of the lower second premolars. The roots of the successional teeth were relatively short and the orientation of their long axes was often significantly divergent from the overall orientation of the crown in both the mesio-distal and bucco-lingual planes. This created the need for a more controlled periapical X-ray monitoring of the uprighting and torqueing movements of these teeth than may be usual. In the above treatment protocol, the ability to use intermaxillary vertical elastics on the previously impacted teeth was emphasized. Their value is seen in the augmentation of the eruptive forces, to improve anchorage and to encourage vertical alveolar growth that normally accompanies erupting teeth. Therefore, efficiency is not served by treating the mandibular anterior teeth before the maxillary anterior

394  Orthodontic Treatment of Impacted Teeth

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

Fig. 14.16  (a–c) Intra-oral views of a class 1 case of cleidocranial dysplasia, to show the initial condition and (d–f) the final outcome, using the Jerusalem approach to treatment, as described here. A class 3 relationship did not develop. (g–j) The en face and profile comparisons of the facial appearance before and after treatment.

(i)

(j)

Fig. 14.16  (Continued )

(a)

(b)

(c)

(d)

(g)

(e)

(f)

(h)

Fig. 14.17  A pleasing result with good profile, dental display and smile line, using the Jerusalem approach to treatment. (a–c) The patient before treatment. (d–f) At one year post-retention. (g) The dentition prior to treatment, at age 10. (h) The dentition a year after the completion of treatment at age 15 years. During the treatment the patient was involved in a car accident and fractured her mandible, with the fracture line passing through the unerupted right canine socket, causing ankylosis. This tooth was extracted and the remaining teeth aligned across the midline. All the mandibular incisors had been fractured and restored.

396  Orthodontic Treatment of Impacted Teeth teeth, merely because there is a time lapse of a year or so between the normal eruption times of these teeth. The treatment of the anterior areas of both jaws should begin at the same time. Nevertheless, it is essential that the forces produced by these vertical ‘up-and-down’ elastics be kept within very minimal values, avoiding the temptation to use elastics which are too heavy. Excessive extrusive forces will bring about rapid eruption, but the clinical crown length of the erupting teeth will be long, owing to a relatively lesser generation of alveolar bone. The teeth will be very mobile, the cervical root area will be exposed and sensitive and they may lose their vitality. In the first surgical intervention, the aim is to remove all the supernumerary teeth, since these seem to be the principal factor in the displacement of the adjacent permanent teeth more deeply into basal bone. The continued presence of these extra teeth will prevent the teeth of the normal series from expressing what little eruptive potential they may have, and hence importance is attached to their early removal. Furthermore, late-developing supernumerary teeth increase in size as they complete their crowns and their roots grow, thereby occupying more space in the alveolus. This results in a progressive displacement of apically placed permanent teeth, pushing them deeper into basal bone and away from the oral cavity. Our experience has been that, when supernumerary teeth are not present in certain areas, the normal permanent teeth in those areas are not severely displaced and, while they may still not erupt spontaneously, their development is fairly normal. Occasionally, their presence may stimulate the shedding of the deciduous predecessor and they may, in time, erupt. For this reason, in those areas where supernumerary teeth are not found, deciduous teeth are not removed in the first surgical intervention. Normal development and maximum eruption potential are probably best realized when the integrity of the dental follicles is maintained until two-thirds to three-quarters of the root length has developed. For this reason, the canine and premolar teeth are not exposed when the supernumerary teeth are removed in the first surgical phase of the treatment. Trauma to developing teeth has been shown to cause damage to both developing roots and the enamel of their completed crowns [51–53] and surgical trauma is no exception. Both in this text and elsewhere [32, 39, 54–57] we have been at pains to point out our opposition to the accepted and established practice of wide surgical exposure of unerupted teeth in normal cases with isolated impacted teeth [58–61]. Typically, in cleidocranial dysplasia there is underdevelopment of the maxilla in the antero-posterior plane and of both jaws in the vertical plane [1, 4, 5]. A very large number of unerupted teeth are present within the bone, largely eliminating the presence of spongiosum. This

being so, the wide removal of the cortical plate [14, 24, 28, 29] would appear to be wasteful and compromising. In the Jerusalem approach, access to the teeth is gained by a minimal opening in the cortical plate immediately overlying the teeth, together with a small window in the dental follicle. The size of the opening is determined by two factors: exposing a surface large enough to accommodate a small • eyelet attachment; enlarging to the minimum size that will allow the • surgeon tothis achieve haemostasis for long enough to allow the bonding procedure to take place in a contaminationfree micro-environment. There is no reason to remove further bone and certainly not to reduce the vertical height of the adjacent cortical plate. The complete surgical flaps are sutured back to close off the surgical field fully, and healing is by primary intention, which should offer a healthier and more rapid period of healing and promote a speedier and more generous response on the part of the alveolar bone [62]. Deeply displaced teeth may thus be drawn occlusally through the overlying bone, which offers no real resistance to the mechanically assisted eruptive force. New alveolar bone accompanies the erupting teeth as they progress towards the occlusal plane in a manner similar to that occurring with normal, unassisted eruption in the normal patient [32, 39]. This will enhance the vertical height of the alveolar processes of the two jaws, incidentally deepening the labial and lingual sulci and improving the overall facial proportions. The final periodontal status of the teeth will also be more normal [32, 37, 55, 56] and the appearance will make it difficult for the trained eye to distinguish between a previously impacted tooth and a normally erupted adjacent tooth. Even in the cleido­cranial dysplasia case exhibiting impaction of the patient’s entire complement of permanent teeth, it is now possible to make the teeth, their supporting tissues and the sulcus depth appear completely normal, as in any routine orthodontic case. In both the Toronto–Melbourne and the Belfast– Hamburg approaches, the need to maintain patency of the exposure and visual contact with the unerupted teeth dictates that the bone level must be pared down to that of the deepest tooth. This clearly includes the reduction of both the lingual and buccal cortical plates to this level – and this in a patient whose alveolar processes are already of reduced height because of the syndrome, and whose teeth are deeply sited in basal bone due to displacement by supernumerary teeth.

Patient variation Similarities are seen among all of the patients suffering from cleidocranial dysplasia, with a varying degree of

Cleidocranial Dysplasia  397 

Fig. 14.18  Panoramic radiograph of a patient 12 years after all appliances were removed. A newly developing supernumerary premolar tooth is noted.

expression of the various characteristic features of the disease, together with many other sporadic phenomena that have been reported to occur with the condition. Erupted permanent incisors are sometimes seen and these may eliminate the need for the ‘incisor-erupting’ initial heavy archwire in one or both arches. Instead, the treatment may begin with the levelling phase using the modified Johnson twin-wire arch. At the completion of all the treatment and the placement of retainers, new radiographs should be taken to check for the development of recurrent supernumerary teeth, which sometimes occurs in the 14–16-year-old patient (Figure 14.18). At this point, any decision regarding the extraction of such teeth is strictly a surgical one [36, 63]. When newly developing teeth are identified at this late stage, their extraction is no longer an orthodontic decision, since full alignment of the teeth has been achieved and suitable retention will prevent any adverse effects. Such factors as location and accessibility, incipient resorption of neighbouring erupted teeth and cysts will all influence the surgeon regarding the necessity and timing of their extraction. The very young and the adult cases While the parents of most cleidocranial dysplasia patients will seek advice and treatment from about 9–10 years of age, at a time when the initiation of the first phase of treatment is opportune, some children may present earlier. If the diagnosis has been made at or shortly after birth, the parents may wish to consult regarding prevention or simply to know what the future holds for their young child. With the accessibility of the internet, its ease of use and the body of information it can make available to the general public, they will often attend the first consultation visit already well informed of the implications of the condition and, as with

many of the rarer conditions and syndromes, may sometimes possess more knowledge of the condition than the first practitioner they consult. Among the initial complaints about which the parents are concerned is the steadily progressive problem of appearance and its psychological effect on this child, whose intelligence is normal. The child is generally shorter, he may have a class 3 skeletal appearance and there is the continued presence of deciduous teeth, when the other children in the class at school are already erupting permanent teeth. However, a panoramic radiograph is likely to show that the 7- or 8-year-old child has a dental age which is three years younger and, as such, is too young for the first phase of the treatment to begin. For this patient, a pre-first phase treatment of an existing class 3 skeletal relation may be usefully initiated in the form of maxillary protraction, with or without preparatory rapid maxillary expansion (Figure 14.19). Since no permanent teeth are present at this dental age, it is probably most practical to use an acrylic cap splint cemented with glass ionomer cement or acid-etch and composite bonding agent. A standard or, preferably, custom-made face mask is then provided, with elastic force to a hook cured into the buccal aspects on each side of the acrylic splint. Compliance is always a problem with these appliances, but it will usually be at its best in patients of this age and younger, and whose parents are understanding, encouraging and proactive. At the completion of this stage, the patient is reassessed regarding the timing for the first phase. At the other end of the scale (Figure 14.20), we may see an untreated patient in his mid- to late teens, with a virtually complete deciduous dentition, few erupted permanent teeth and a strong class 3 skeletal relationship that clearly demands surgical reduction. Despite the obvious facial disfigurement, the presenting symptom may often be pain or swelling from the deciduous teeth that will likely have suffered a considerable degree of morbidity. This may have triggered the patient’s initial request for emergency treatment for their immediate distress. Even following only a cursory clinical and radiological exam­ ination, the concerned dentist will then (hopefully) refer the patient on for orthodontic and surgical evaluation and treatment. As a general rule, bringing the teeth into the dental arches and aligning them will precede the skeletal correction. In the child patient, the Jerusalem approach describes the division into two separate phases of treatment because of developmental determinants of the dentition. With the young adult patient this is irrelevant, since all the teeth will have passed the stage of development that is appropriate for eruption in the unaffected individual. Nevertheless, erupting all the teeth in both arches in a single biomechanical treatment phase has its limitations.

398  Orthodontic Treatment of Impacted Teeth

(a)

(c)

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(d)

(e) (g)

(f) Fig. 14.19  Pre-first phase protraction orthopaedics at age 8.5 years (dental age 5.6 years). (a–c) The occlusion showing a full complement of deciduous teeth in a strong class 3 relationship. (d–g) An acrylic cap splint carrying a Hyrax® screw is bonded to the maxillary posterior teeth. This carries a small button cured into the acrylic, one each side for elastic attachment to the face mask (not shown). (h–k) The occlusal relationships have been slightly over-corrected. (l, m) The profile before and after protraction.

(h)

(j)

(i)

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(m)

(l) Fig. 14.19  (Continued )

(a)

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Fig. 14.20  Late treatment in a 15.7-year-old male. (a–e) Initial clinical views. The patient never brought his teeth into occlusion due to severe overclosure – he chewed on his tongue. In the lateral views in forced occlusion, the anterior maxilla is totally enveloped by the anterior portion of the mandible. Apart from the permanent molars, only two lower incisors of the permanent dentition have erupted. (f, g) Cephalogram and panoramic views show the extreme skeletal class 3 relation and the fully developed, but unerupted permanent dentition. Note supernumerary teeth in the maxillary incisor and canine regions, but congenitally absent mandibular third molars. (h) Intra-oral occlusal views of the appliances immediately prior to exposure surgery. (i, j) All the unerupted teeth are exposed only to the most minimal degree to permit bonding of the small eyelet attachments (not shown). (k) The post-surgical panoramic radiograph after extraction of 18 deciduous teeth, five supernumerary teeth, and the exposure of 16 unerupted permanent teeth with attachment bonding to 15 of them. The right mandibular second premolar was left uncovered and unattached, while the remainder of the teeth were covered fully by the surgical flaps in a closed exposure technique. Note that bone may be seen to surround and cover most of the unerupted teeth, except those that are more superficially placed or had been adjacent to the areas where the supernumerary teeth were removed. Ligation to the vertically activated labial arches was effected immediately. (l–n) Two years later, all teeth had been erupted into the class 3 relation and treatment was discontinued. (o–q) The panoramic, profile and cephalometric views prior to appliance removal. (r–u) Two years later, maxillary (Le Fort 1) advancement surgery was performed. (Courtesy of Dr E. Regev and Dr D. Harary.) The outcome may be seen in these intra-oral clinical and panoramic radiographic films, profile photograph and cephalogram. Note the excellent appearance of the teeth and supporting tissues – hardly what may be expected in a case with previously multiple impacted teeth!

400  Orthodontic Treatment of Impacted Teeth

(c)

(d)

(e)

(f)

(g) Fig. 14.20  (Continued )

Cleidocranial Dysplasia  401 

(i)

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(h)

(k) Fig. 14.20  (Continued )

Accordingly, there is merit in following the same overall two-stage procedure as recommended for the younger person, with the exception that the phases will follow on, one after the other. Thus, for practical/operative rather than biological/developmental reasons, it remains convenient and makes clinical sense to divide the objectives of treatment of the multiple impactions into anterior and posterior areas of activity. The fact of closure of the root apices of these teeth does not appear to impede their eruption once their own innate, minimally existing eruption potential is augmented with extraneous forces provided by the orthodontic appliances.

Appliance-driven eruption of the teeth during the active phase of their root development is generally accompanied by an excellent regenerative alveolar bone reaction. This contributes much to an increased height of the alveolar ridges, to a deepening of the labial and lingual sulci and to an enhancement of the reduced height of the lower third of the face, as has already been pointed out. When the patient reports for treatment only after his growth is completed, and while resolution of the impactions may generally be completely successful, there will be a much less favourable contribution of the alveolar bone to the overall result.

402  Orthodontic Treatment of Impacted Teeth

(n) (l)

(m)

(o)

(p) Fig. 14.20  (Continued )

(q)

Cleidocranial Dysplasia  403 

(r)

(s)

(t)

(u)

Fig. 14.20  (Continued )

For the most part, the overall active treatment to resolve the multiple tooth impaction and achieve good alignment should take between three and five years, depending on its complexity and, generally, excluding the interlude that may occur between first and second phases. At the conclusion of the orthodontic treatment, the teeth will be fully erupted and aligned, with tip, rotation, uprighting and torque all corrected. At this stage, a renewed look must be taken at the jaw relations. New records need to be assessed and the orthosurgical aspects of the condition evaluated, as with any other non-cleidocranial dysplasia orthosurgical case. By and large, it will be the maxilla that needs to be brought forward, but mandibular surgery is sometimes needed either because of occasional true man-

dibular prognathism or in order to create a harmonious relationship of the jaws, in the presence of other abnormal skeletal parameters. Considerable jaw growth occurs during and around the adolescent growth spurt, which sometimes alters the jaw relation into a more class 3 relation, and this generally occurs during the mid-treatment second phase period. In this situation, the orthodontist should continue on the steady path of eruption resolution until all the teeth are in the arch, with the exception of the third molars. Only at this stage should the case be re-evaluated for orthosurgery. In those cases where the growth has brought about a marked skeletal class 3 relation, the changes that occur in the jaw relation are usually far too major for

404  Orthodontic Treatment of Impacted Teeth a protraction headgear or a chin cap to ameliorate this developing skeletal pattern, even with excellent compliance. For these patients, surgery will be the only satisfactory answer.

References   1.  Kalliala E, Taskinen PJ. Cleidocranial dystosis: report of 6 typical cases and 1 atypical case. J Oral Surg 1962; 15: 808–822.   2.  Bixler D. Hereditable disorders affecting cementum and the periodontal structures. In Stewart RE, Prescott GH, eds. Oral Facial Genetics. St Louis, MO: Mosby, 1976: 282–284.   3.  Cohen MM Jr. Dysmorphic syndromes with craniofacial manifestations. In Stewart RE, Prescott GH, eds. Oral Facial Genetics. St Louis, MO: Mosby, 1976: 566–567.   4.  Zegarelli EV, Kutscher AH, Hyman GA. Diagnosis of Diseases of the Mouth and Jaws. Philadelphia: Lea & Febiger, 1978: 137.   5.  Shafer WG, Hine MK, Levy BM. A Textbook of Oral Pathology, 4th edn. Philadelphia: Saunders, 1983: 678–680.   6.  Tachdjian MO. Pediatric Orthopedics, 2nd edn. Philadelphia: Saunders, 1990: 840–844.   7.  Gorlin RJ, Cohen MM Jr, Levin LS. Syndromes of the Head and Neck, 3rd edn. New York: Oxford University Press, 1990: 249–253.   8.  Stewart RE, Prescott GH, eds. Oral Facial Genetics. St Louis, MO: Mosby, 1976.   9.  Yamamoto H, Sakae T, Davies JE. Cleidocranial dysplasia: a light microscope, electron microscope and crystallographic study. Oral Surg Oral Med Oral Pathol 1989; 68: 195–200. 10.  Mendoza-Londono R, Lee B, Cleidocranial Dysostosis. NCBI Resources, Gene Reviews, Pagon RA, Bird TC, Dolan CR, et al., editors, 1993. 11.  Cooper SC, Flaitz CM, Johnston DA, et al. A natural history of cleidocranial dysplasia. Am J Med Genet. 2001; 104: 1–6. 12.  Ishii K, Nielsen IL, Vargervik K. Characteristics of jaw growth in cleidocranial dysplasia. Cleft Palate Craniofac J 1998; 35: 161–166. 13.  Hu JCC, Nurko C, Sun X et al. Characteristics of cementum in cleidocranial dysplasia. J Hard Tissue Biol 2002; 11: 9–15. 14.  Smylski PT, Woodside DG, Harnett BE. Surgical and orthodontic treatment of cleidocranial dysostosis. Int J Oral Surg 1974; 3: 380–385. 15.  Winther JE, Khan MW. Cleidocranial dysostosis: report of 4 cases. Dent Pract 1972; 22: 215–219. 16.  Kelly E, Nakamoto RY. Cleidocranial dysostosis – a prosthodontic problem. J Pros Dent 1974; 31: 518–526. 17.  Frommer HH, Lapeyrolerie FM. Two case reports of cleidocranial dysostosis. New York J Dent 1964; 34: 103–107. 18.  Hitchin AD, Fairley JM. Dental management in cleidocranial dysostosis. Br J Oral Surg 1974; 12: 46–55. 19.  Weintraub GS, Yasilove IL. Prosthodontic therapy for cleidocranial dysostosis. Report of a case. J Am Dent Assoc 1978; 96: 301–305. 20.  Probster L, Bachmann R, Weber H. Custom-made resin-bonded attachments supporting a removable partial denture using the spark erosion technique: a case report. Quintessence Int 1991; 22: 349–354. 21.  Muller EE. Transplantation of teeth in cleidocranial dysostosis. In Husted E, Hjorting-Hansen E, eds. Oral Surgery: Transactions of the 2nd Congress of the International Association of Oral Surgeons. Copenhagen: Munksgaard, 1967: 375–379. 22.  Oksala E, Fagerstrom G. A two-stage sutotransplantation of 14 teeth in a patient with cleidocranial dysostosis. Suom Hammaslaak Toim 1971; 67: 333–338. 23.  Elomaa E, Elomaa M. Orthodontic treatment of a case of cleidocranial dysostosis. Suom Hammaslaak Toim 1967; 67: 139–151. 24.  Hall RK, Hyland AL. Combined surgical and orthodontic management of the oral abnormalities in children with cleidocranial dysplasia. Int J Oral Surg 1978; 7: 267–273. 25.  Frame K, Evans RIW. Progressive development of supernumerary teeth in cleidocranial dysplasia. Br J Orthod 1989; 16: 103–106. 26.  Trimble LD, West RA, McNeill RW. Cleidocranial dysplasia: comprehensive treatment of the dentofacial abnormalities. J Am Dent Assoc 1982; 105: 661–666.

27.  Davies TM, Lewis DH, Gillbe GV. The surgical and orthodontic management of unerupted teeth in cleidocranial dysostosis. Br J Orthod 1987; 14: 43–47. 28.  Richardson A, Swinson T. Combined orthodontic and surgical approach to cleido-cranial dysostosis. Trans Eur Orthod Soc 1987; 63: 23 [abstract]. 29.  Behlfelt K. Cleido-cranial dysplasia: diagnosis and treatment concept. Trans Eur Orthod Soc 1987; 63: 25 [abstract]. 30.  Miller R, Sakamoto E, Zell A et al. Cleidocranial dysostosis. A multidisciplinary approach to treatment. J Am Dent Assoc 1978; 96: 296–300. 31.  Becker A, Shochat S. Submergence of a deciduous tooth, its ramifications on the dentition and treatment of the resulting malocclusion. Am J Orthod 1982; 81: 240–244. 32.  Kohavi D, Becker A, Zilberman Y. Surgical exposure, orthodontic movement and final tooth position as factors in periodontal breakdown of treated palatally impacted canines. Am J Orthod 1984; 85: 72–77. 33.  Howe GL. Minor Oral Surgery, 2nd edn. Bristol: Wright, 1971: 135–137. 34.  Becker A, Lustmann J, Shteyer A. Cleidocranial dysplasia: part 1 – general principles of the orthodontic and surgical treatment modality. Am J Orthod Dentofacial Orthop 1997; 111: 28–33. 35.  Becker A, Shteyer A, Bimstein E, Lustmann J. Cleidocranial dysplasia: part 2 – a treatment protocol for the orthodontic and surgical modality. Am J Orthod Dentofacial Orthop 1997; 111: 173–183. 36.  Becker A, Shteyer A. A surgical and orthodontic approach to the dentition in cleidocranial dysostosis. Trans Eur Orthod Soc 1987; 63: 121 [abstract]. 37.  Seow WK, Hertzberg J. Dental development and molar root length in children with cleidocranial dysplasia. Pediatr Dent 1995; 17: 101–105. 38.  Becker A, Zilberman Y. The palatally impacted canine: a new approach to its treatment. Am J Orthod 1978; 74: 422–429. 39.  Becker A, Kohavi D, Zilberman Y. Periodontal status following the alignment of palatally impacted canine teeth. Am J Orthod 1983; 84: 332–336. 40.  Vermette ME, Kokich VG, Kennedy DB. Uncovering labially impacted teeth: apically repositioned flap and closed-eruption techniques. Angle Orthod 1995; 65: 23–32. 41.  Gron A. Prediction of tooth emergence. J Dent Res 1962; 41: 573–585. 42.  Ricketts RM. Perspectives in the clinical application of cephalometrics. The first fifty years. Angle Orthod 1981; 51: 115–150. 43.  Zachrisson BU. Premolar extraction and smile esthetics. Am J Orthod Dentofacial Orthop 2003; 124: 11A–12A. 44.  Zachrisson BU. Incisal edge recontouring in orthodontic finishing. World J Orthod 2005; 6: 398–405. 45.  Zachrisson BU. Clinical experience with direct-bonded orthodontic retainers. Am J Orthod 1977; 71: 440–448. 46.  Becker A, Goultschin J. The multistrand retainer and splint. Am J Orthod 1984; 81: 470–474. 47.  Becker A. Periodontal splinting with multistrand wire following orthodontic realignment of migrated teeth: report of 38 cases. Int J Adult Orthod Orthogn Surg 1987; 2: 99–109. 48.  Becker A, Chaushu S. Non-invasive periodontal splinting with multistrand wire following the orthodontic realignment of periodontally migrated teeth. Orthodontics, 2004; 1: 159–167. 49.  Johnson JE. A new orthodontic mechanism: the twin wire alignment appliance. Int J Orthod 1934; 20: 946–963. 50.  Shepard ES. Technique and Treatment with the Twin- Wire Appliance. St Louis, MO: Mosby, 1961. 51.  Brin I, Ben Bassat Y, Fuks A, Zilberman Y. Trauma to the primary incisors and its effect on the permanent incisors. Pediatr Dent 1984; 6: 78–82. 52.  Ben Bassat Y, Brin I, Fuks A, Zilberman Y. Effect of trauma to the primary incisors on permanent successors in different developmental stages. Pediatr Dent 1985; 7: 37–40. 53.  Zilberman Y, Fuks A, Ben Bassat Y et al. Effect of trauma to primary incisors on root development of their permanent successors. Pediatr Dent 1986; 8: 289–293. 54.  Becker A. Early treatment for impacted maxillary incisors. Am J Orthod Dentofacial Orthop 2002; 121: 586–587.

Cleidocranial Dysplasia  405  55.  Becker A, Brin I, Ben-Bassat Y, Zilberman Y, Chaushu S. Periodontal status following surgical-orthodontic alignment of impacted maxillary incisors by a closed eruption technique. Am J Orthod Dentofacial Orthop 2002; 122: 9–14. 56.  Chaushu S, Brin I, Ben-Bassat Y, Zilberman Y, Becker A. Periodontal status following surgical-orthodontic alignment of impacted central incisors by an open-eruption technique. Eur J Orthod 2003; 25: 579–584. 57.  Becker A. An interview with Adrian Becker. World J Orthod 2004; 5: 277–282. 58.  Lappin MM. Practical management of the impacted maxillary canine. Am J Orthod 1951; 37: 769–778. 59.  Lewis PD. Preorthodontic surgery in the treatment of impacted canines. Am J Orthod 1971; 60: 382–397.

60.  von der Heydt K. The surgical uncovering and orthodontic positioning of unerupted maxillary canines. Am J Orthod 1975; 68: 256–276. 61.  Kokich VG. Surgical and orthodontic management of impacted maxillary canines. Am J Orthod Dentofacial Orthop 2004; 126: 278–283. 62.  Laskin D. Oral and Maxillofacial Surgery, Vol 2. St Louis, MO: Mosby, 1985: 44–47. 63.  Becker A, Bimstein E, Shteyer A. Interdisciplinary treatment of multiple unerupted supernumerary teeth. Am J Orthod 1982; 81: 417–422.

15 Extreme Impactions, Unusual Phenomena and Difficult Decisions

Case 1: Monster tooth, supernumerary tooth, impacted central incisor and the maxillary midline

407

Case 2: Bilaterally impacted maxillary canines in a patient suffering with aggressive juvenile periodontitis

412

Case 3: Labially impacted maxillary canine at the level of the nasal floor

412

Case 4: Impacted mandibular molars and premolars with over-eruption of the opposing teeth

419

Case 5: Severe trauma in infancy causing damage to anterior tooth buds

420

Case 6: Buccal to the lateral incisor and palatal to the central incisor

430

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

Extreme Impactions, Unusual Phenomena and Difficult Decisions  407  In this chapter, the intention is to present a few cases featuring impacted teeth in a variety of difficult, interdisciplinary or extreme situations. For these cases, there are no hardand-fast rules, the literature offers the practitioner little assistance and, despite all the advice that may be sought and received, the orthodontist largely remains alone in a diagnostic or treatment planning wilderness without a compass. Options may be few, but they also may be so many that each potential scenario must be acted out in the fertile imagination of the orthodontist to find the direction that will offer relative success, cause the least collateral damage and carry with it the least risk of failure. Some may require the active participation of specialists in fields other than orthodontics and oral surgery, particularly the paediatric dentist, the endodontist and the periodontist. By their very nature, these cases are frequently one of a kind and thus determining the diagnosis, the treatment options, chosen treatment approach and prognosis may never be evidence-based, but largely dependent on the logic acquired from the collected clinical experience of the operators. This is both the strength and the weakness of published single case reports. There is often much to learn from them individually but, whatever that may be, it cannot be used to draw conclusions in relation to other apparently or arguably similar cases in the future. Without doubt legitimate criticism may be levelled by any dentist regarding the treatment decisions that were made in the following indivi­ dual presentations. Moreover, an alternative approach to the same case might be preferred, a choice that will be influenced or biased by that orthodontist’s positive or negative experience with the same or contrary modalities of treatment. The clinical cases shown here are mostly finished cases with long-term post-treatment follow-up and they are offered here specifically as they relate to impacted teeth. Others are in the final stages of their overall active treatment as this book goes to print but, in all cases, the principal issue under discussion (i.e. resolution of the impaction) will have been fully and successfully addressed.

Case 1: Monster tooth, supernumerary tooth, impacted central incisor and the maxillary midline The existence of an unusually large maxillary central incisor with talon cusp or cusps, otherwise known as dens evaginatus, is rare and usually published in the literature as a single case report [1–3]. Since it takes up more than the space of a normal central incisor and its location is at the front of the mouth, the dens evaginatus is unsightly and disfiguring. To reduce it in size with the view to reshaping it to more normal proportions is difficult or impossible, because of a large pulp chamber and/or a very broad crosssection in the cervical region. In such circumstances, it is often extracted and replaced prosthetically, or it may be

enlarged and reshaped to make it resemble two teeth, a central and lateral incisor, while sacrificing the adjacent normal and healthy lateral incisor. In the present case of a 7-year-old healthy girl (Figure15.1a-e), the right central incisor was much enlarged with a Y-shaped crown cross-section, due to the talon cusp and a much enlarged pulp chamber and root cross-section at the CEJ. The dentition comprised the four erupted first molars, mandibular central incisors and rotated erupting mandibular lateral incisors, associated with mild dental crowding. On the maxillary left side, there was an atypical incisiform ‘central incisor’, which was assumed to be a supernumerary tooth. The dens evaginatus occupied most of the space for both central and lateral incisor of that side. The remainder of the dentition comprised healthy and restored deciduous teeth in normal intermaxillary occlusal relations. Periapical and panoramic radiographs (Figure 15.1f, g) revealed the unerupted teeth superimposed on one another with inadequate differentiation for appropriate diagnosis. Accordingly a CBCT was performed (Figure 15.1h, i) from which it was concluded that the unerupted teeth in the maxillary incisor region included two normal lateral incisors and an unerupted, normally shaped, left maxillary central incisor. This lent credence to the assertion that the erupted ‘central incisor’ was a supernumerary tooth and that the dens evaginatus represented a fusion between a right central incisor and an additional supernumerary tooth. The shape and size of the dens evaginatus, together with its pulp chamber dimension and cross-sectional breadth at the CEJ, determined that the limited alteration of crown shape possible would not provide a satisfactory answer to the overall space problem, nor would it contribute to improving the patient’s appearance. Thus, its extraction was unavoidable. This created the unbalanced situation in which an incisor would be missing on the right side, while an extra incisor was present on the other. The treatment proposed, therefore, was to move the erupted and presumed supernumerary tooth across from the left to fill the place of the extracted dens evaginatus on the right side and thus to permit the eruption of the impacted normal left central incisor tooth into its designated place. Once this was completed, the deciduous canines in both jaws would be extracted to provide space temporarily to permit the alignment of the four incisors in both jaws. A modified form of the 2 × 4 appliance (in fact, a 2 × 1 appliance) was placed, with a palatal arch soldered to two molar bands and the typical modified Johnson twin arch set-up described in Chapter 5, with a Tip-Edge® bracket placed on the single erupted permanent supernumerary incisor and an archwire of 0.016 in round steel wire inserted into the buccal arms of the composite archwire which, in turn, would be inserted into the molar tubes (Figure 15.1j–m).

(b)

(a)

(c)

(d)

(e)

(f)

Fig. 15.1  (a–e) The clinical intra-oral views. (f, g) Periapical and panoramic radiographic views. (h) CBCT axial cut through the roots of the erupted teeth. #D.E is the dens evaginatus and #S the erupted supernumerary tooth. (i) Right and left CBCT transaxial views. (j-m) The modified Johnson 2 × 4 (2 × 1) appliance in place. (n) Following the extraction of the dens evaginatus, a coil spring is compressed between the soldered stop on the mesial end of the left buccal tube arm and the bracket on the supernumerary tooth. (o) With the TipEdge bracket, tipping of the left supernumerary across the facial midline takes only six weeks. (p) Four months later, the left central incisor has erupted and is incorporated in the appliance, with a coil spring moving it to the midline, while the supernumerary tooth is being uprighted in the right central incisor position. (q) The condition prior to lateral incisor eruption. (r) The lateral incisors erupt spontaneously and are incorporated in the appliance. (s–u) The completion of phase 1 treatment. (v, w) Panoramic and periapical views clearly show the midline suture on the right side of the supernumerary tooth, together with an enlarged right canine dental follicle/early dentigerous cyst. (x) The midline raphe is seen to deviate sharply to the right in this pre-phase 2 occlusal view of the palate, as indicated by the arrows. The incisive papilla has also been displaced. The dental follicle of the unerupted right canine has enlarged into a small dentigerous cyst and can be seen to have expanded the alveolar ridge. (y) The pre-phase 2 view of the patient from the front shows a pleasing appearance, a normal dental smile line and an apparently natural dental midline.

Extreme Impactions, Unusual Phenomena and Difficult Decisions  409 

#DE #12

(g)

(h)

#13 #21 #22

#12 #53

#62

(i)

(j)

(k)

(l)

Fig. 15.1  (Continued )

#S

#21 #22

410  Orthodontic Treatment of Impacted Teeth

(n) (m)

(o)

(p)

(q)

(r)

Fig. 15.1  (Continued )

Extreme Impactions, Unusual Phenomena and Difficult Decisions  411 

(t) (s)

(u)

(v) Enlarged follicle of canine

#S

#12

#21

Incisive papilla #22

#24

Midline raphe

(w) Fig. 15.1  (Continued )

(x)

(y)

412  Orthodontic Treatment of Impacted Teeth The orientation of the soldered molar tubes and these buccal arms was tipped slightly downwards on each side to encourage incisor eruption and bite closure and a welded stop was placed on the buccal arms of each side mesial to the molar tubes to maintain the initial arch length and to prevent unwanted sliding of the buccal arms through the tubes. The abnormal right dens evaginus central incisor was extracted at the next visit and, on the same day, a coil spring was compressed between the soldered stop at the mesial end of the left buccal arm and the bracket on the left erupted incisiform supernumerary tooth (Figure 15.1n). Six weeks later, the tooth was seen to have tipped across the midline and into proximal contact with the deciduous canine of the opposite side (Figure 15.1o). The impacted left central incisor erupted rapidly and autonomously five months after placement of the coil spring, driven by the sudden provision of space in the arch. This tooth was bracketed and a coil spring again placed on the arch to move it to the midline. An auxiliary spring was placed in the vertical slot of the Tip-Edge® bracket of the supernumerary tooth to upright its root across the facial midline (Figure 15.1p, q). During the subsequent 12 months of treatment, the four deciduous canines were extracted and the lateral incisors erupted without further assistance. Brackets were placed on them and the teeth were aligned and moved towards and slightly across the midline. Further root uprighting was then initiated (Figure 15.1r). Phase 1 treatment was completed seven months later, with satisfactory alignment of the teeth (Figure 15.1s-u). The root configuration of the substitute ‘right central incisor’, formerly the supernumerary tooth (Figure 15.1v, w), strengthens the assumption that it was indeed a supernumerary tooth. It should be clearly understood that moving a tooth across the left side of the maxilla to the right, across the midline, does not infer that the tooth actually traverses the midline palatal suture. What happens is that the bone on each side of the suture is remodelled and moves together with the tooth, so that the suture remains on the mesial side of the left incisor, as can be seen on the radiographs and the radiograph (Figure 15.1v–x). The total treatment time was 26 months, a removable maxillary Hawley retainer is being worn nightly and phase 2 treatment will be considered in the full permanent dentition.

dontal disease and there were no symptoms that might have indicated this. An examination of the initial panoramic view (Figure 15.2a) indicated a routine palatal impaction of both maxillary canines, both classified as group 1 type (see Chapter 6). Clinically, there was a close to normal occlusion with excellent alignment in both jaws, good intercuspation and a normal overbite and overjet. The complicating factor here was that the patient suffered from aggressive juvenile periodontitis, with the loss of much alveolar bone in the molar and incisor regions of both jaws. The patient returned 18 months later having completed her periodontal treatment, which included the grafting and integration of bovine bone in the more severely affected locations mesial to the first molars (periodontic treatment by Professor Ayala Stabholz). These may be clearly seen as small radio-opacities on the new film after a long period of post-treatment follow-up (Figure 15.2b). Note also the spontaneous closure of the spaces between the second premolars and the first molars which had been present before treatment began. Pre-surgical orthodontic preparation for this almost normal occlusion (Figure 15.2c–e) involved levelling, aligning and space-opening and lasted just four months, before closed exposures were performed on both canines (Figure 15.2f–h). A measured length of steel tube was threaded over the base arch, with the purpose of holding the distance between the premolar and lateral incisor brackets. The right side is shown here, to illustrate the use of an elastic e-link stretched between the occlusally inserted power pins into the vertical slots of the Tip-Edge® brackets of the lateral incisor and first premolar, which was then raised and engaged in the pigtail ligature close to the sutured flap. In this way, renewable vertical traction was applied to the impacted teeth to bring about their eruption (Figure 15.2i–k). The final result, shown here eight years after completion of the orthodontic treatment (Figure 15.2l–n), shows excellent alignment and inter-arch relations. The clinical appearance of the teeth and the new periapical radiographs offered no signs or clues that would indicate that the canines had previously been palatally impacted (Figure 15.2o–t). While still discernible in the radiographs, the bone grafts have become progressively more integrated into the trabecular picture. The orthodontic treatment time for this case was 18 months and the patient is followed up by the periodontist on a regular basis.

Case 2: Bilaterally impacted maxillary canines in a patient suffering with aggressive juvenile periodontitis

Case 3: Labially impacted maxillary canine at the level of the nasal floor

The patient was a 15-year-old girl, who had been referred to the author for the treatment of her bilaterally impacted maxillary canine teeth. No mention was made in the referral letter to the effect that the patient suffered from perio-

The patient, a girl aged 11 years in the late mixed dentition stage, was referred to the author with accompanying radiographs from which bilateral labially impacted upper canines had been diagnosed, one of which was extremely high in the maxilla.

Extreme Impactions, Unusual Phenomena and Difficult Decisions  413 

(a)

(b)

(c)

(d)

(e)

(f)

Fig. 15.2  (a) Initial panoramic view with bilateral maxillary palatal canine impaction. The typical picture of aggressive juvenile periodontitis is seen, with deep vertical periodontal defects and severe bone loss in the four molar and maxillary incisor regions. (b) A new panoramic film taken after the successful completion of periodontal treatment shows the radio-opaque areas where bovine bone was used to regenerate bone in the defective areas. (Periodontics by Professor Ayala Stabholz.) (c–e) The post-periodontic intra-oral appearance of the malocclusion. (f–h) After extraction of the maxillary deciduous canine, orthodontic alignment, levelling and space opening, the canine spaces are held open with the use of cut lengths of stainless steel tube of broad gauge (0.036 in internal diameter) threaded onto the main arch. (i–k) At surgery, the orthodontist has bonded an eyelet attachment to the exposed canine and traction is applied using an elastic chain stretched between the inverted power pins on the adjacent teeth. This is raised in its middle portion to engage the twisted pigtail ligature that has been turned into a small hook close to the sutured tissues. (Surgery by Dr H.P. Samen.) (l–n) At 8 years following the completion of orthodontic treatment, there is an excellent alignment and appearance of the gingival tissue around the previously impacted canines. There are no signs that these had been impacted. (o–t) Periapical views of the areas that were most seriously affected by the condition, seen eight years post-treatment.

414  Orthodontic Treatment of Impacted Teeth

(g)

(h)

(j) (i)

(k)

(l)

(m)

(n)

Fig. 15.2  (Continued )

Extreme Impactions, Unusual Phenomena and Difficult Decisions  415 

(o)

(q)

(t)

(r)

(p) Fig. 15.2  (Continued )

(s)

416  Orthodontic Treatment of Impacted Teeth The existing occlusion was almost ideal, with good general dental alignment, a class 1 occlusal relationship of the molars and normal incisor overbite and overjet (Figure 15.3a-c). The panoramic radiograph (Figure 15.3d) showed the presence of a lingual arch space maintainer, which had been placed following the extraction of deciduous teeth. It showed the presence of all the permanent teeth, together with the about-to-be-shed maxillary left first and second

deciduous molars and the mandibular left second deciduous molar. The two maxillary deciduous canines were also present with virtually complete and unresorbed roots. The maxillary left first premolar root was mesially displaced and in partial transposition with the left canine, which was extremely high and lying horizontally in the palatal plane on a line shared by the floor of the nose and the floor of the maxillary sinus. The right canine was also very high, in

(a)

(b)

(c)

(d)

Fig. 15.3  (First published in Seminars in Orthodontics, reprinted with permission.) (a–c) The intra-oral clinical views of the patient when first seen by the author. (d, e) The initial panoramic view and cephalogram to show the position and orientation of the left canine (arrow). The right canine is also impacted on the labial side of the arch. (f–h) CBCT three-dimensional views and a transaxial view to show the extreme height of the canine, adjacent to the nasal cavity and maxillary sinus, high above the sulcus height. (i–k) Closed exposure technique used to expose the canines on both sides, with eyelet bonding. At the completion of the surgical procedure, the pigtail ligature was shortened and formed into a small hook and an elastic ligature was used initially to apply immediate traction. (Surgery by Dr E. Regev.) (l–n) On the right side an auxiliary NiTi wire has been used to draw down the canine, which is about to erupt through attached gingiva. On the left side, an offset 0.016 in round wire with steel ligature has been used progressively, until the tooth is about to erupt through the oral mucosa. At this point an apically reposition flap has been used to place attached gingiva on the labial aspect of the canine before continuing the traction process. (o–q) The final result shows some labial recession on all the teeth due to obsessive toothbrushing, although the canines are worst affected, which is typical of labial canines. (r, s) Post-treatment periapical and panoramic views of the teeth show normal bone pattern, but marked apical root resorption of several teeth. This is not expected to alter in the future, following the cessation of orthodontic movement.

Extreme Impactions, Unusual Phenomena and Difficult Decisions  417 

(e)

(f)

(g)

(i) Fig. 15.3  (Continued )

(h)

(j)

(k)

418  Orthodontic Treatment of Impacted Teeth

(l)

(m)

(n)

(o)

(p)

(q)

Fig. 15.3  (Continued )

comparison with any ‘regular’ impacted canine, although not reaching the severity of the left canine. The a–p and vertical orientation of the two canines was clearly depicted in the lateral cephalogram, as well as the mesial displacement of the root of the first premolar (Figure 15.3e). In the CBCT 3-D views and the transaxial slice shown here, the relative difficulty of the impactions will be clearly appreciated (Figure 15.3f–h). Orthodontic alignment, levelling and space-opening were completed very quickly and measured stainless steel tube lengths were threaded on to the heavy 0.020 in main arch to maintain canine spaces and add rigidity to the anchor unit.

Labial surgical flaps were raised from the attached gingiva around the deciduous canines on each side of the maxilla under local anaesthetic cover (Figure 15.3i, j). These were reflected high into the depth of the sulcus area on both sides but, on the left side, exposure of the canine was only achieved about 10 mm above the extremity of the sulcus. Small eyelet attachments were bonded, with the twisted pigtail ligature drawn vertically downward, closely adapted to and lying over the exposed alveolar bone. The surgical flaps were then fully replaced and sutured, with the terminal hook of the pigtail ligatures emanating from the sutured edges on each side. The deciduous canines were not extracted at this stage.

Extreme Impactions, Unusual Phenomena and Difficult Decisions  419 

(r)

(s) Fig. 15.3  (Continued )

Orthodontic traction was provided immediately following the suturing of the flaps with elastic thread ties (Figure 15.3k). Subsequently, traction was variously applied with NiTi auxiliary wires and with offset light wire auxiliary arches. On the right side, it was found possible to erupt the canine through the attached gingiva and directly into its designated location (Figure 15.3l). On the left side, the canine bulged the oral mucosa above the attached gingiva (Figure 15.3m) and a secondary surgical procedure was undertaken to apically reposition the attached gingiva over the tooth (Figure 15.3n). At the end of treatment, the alignment of the teeth was excellent and, due to the compulsive aggressive toothbrushing, there was a general displacement of the gingival tissues in an apical direction. This was more noticeable over the two canines, which is largely to be expected with labially displaced canines (Figure 15.3o–q). Post-treatment radiographs (Figure 15.3r, s) show significant root resorption of the lateral incisors on both sides and of the central incisors and the left canine to a lesser degree.

Case 4: Impacted mandibular molars and premolars with over-eruption of the opposing teeth This patient was seen first by his dentist at the age of 8.6 years, when it was noted that all the teeth distal to the deciduous canine in the lower right side of the jaw were unerupted. The deciduous molars on that side had been extracted some time earlier, together with those on the maxillary opposite side. The other three first permanent molars were erupted and the deciduous canines were still present. As the result of the extractions, the left maxillary molar had drifted mesially, reducing the extraction space and preventing the second premolar from erupting fully between it and the erupted first premolar. The maxillary posterior teeth, together with the alveolar ridge of the right side, had markedly over-erupted due to the absence of antagonists and the permanent molar was in direct occlusal contact with the mucosa covering its lower counterpart.

420  Orthodontic Treatment of Impacted Teeth Radiographic records from that time consisted only of a panoramic film (Figure 15.4a), which showed that all the teeth were present, were situated low down in a narrowed body of the mandible and fully enclosed within alveolar bone, with no apparent follicular abnormality. The roots of the first molar were short, their apices were distally hooked, with almost completed apexification, and their apices were abnormally close to the lower border of the mandible. These observations label the first molar as impacted due to an unknown causal agent which had clearly overcome the natural eruption potential of the tooth. The radiographic appearance of the adjacent premolars and second molar was normal for the age of the patient, with early root development only and, as such, would not have been expected to erupt for some time. No treatment was performed at that time. The child was referred to the author three years later, at the age of 11.6 years, when the situation of the first mandibular permanent molar had not changed and both premolars and second molar also remained unerupted, although their root development was now beyond that expected of normal unerupted teeth. However, the crowns of the first premolar and second molar could be palpated immediately beneath the overlying mucosa and, before treatment was commenced, the second molar had just broken through the tissues. Elsewhere, the premolars and permanent second molars had all erupted or were palpably close to eruption (Figure 15.4b–g). It was obvious from the outset that any attempt to raise these teeth using forces derived from intra- or inter-arch dental anchorage would seriously worsen the occlusal plane in both jaws, particularly since the maxillary right side was already severely vertically compromised and was itself in need of intrusive mechanics to bring about some semblance of normality. Furthermore, without knowledge of the cause of the non-eruption of the molar, it was by no means certain that it would respond to extrusive mechanics. The differential diagnosis was principally between primary failure of eruption, ankylosis and invasive cervical root resorption, none of which could be confirmed. Accordingly, therapeutic diagnosis was the only remaining option. The non-eruption of the premolars was considered to be due in part, at least, to the very early extraction and thickened reparative mucosal covering, having regard to their being prominently outlined in the gingiva. Nevertheless, the second premolar was also deeply impacted and this may have been secondary to the more severe impaction of its distal neighbour [4]. Accordingly, it was felt that the only serious problem related to the first molar and, to a lesser extent, the second premolar, while the first premolar and second molar would be expected to erupt following simple elimination of the mucosa covering the occlusal surfaces of these teeth. Treatment was planned with the simultaneous use of two separate and unconnected systems. Skeletal anchorage from

a zygomatic plate was to be employed to apply vertical traction to the impacted first molar and second premolar teeth in the attempt to overcome the non-eruption. At the same time, the plate would also be used as the anchor base from which to apply intrusive forces to the maxillary teeth of the right side. The second independent system was the placement of traditional orthodontic appliances for the purpose of levelling, alignment and treating the inter-maxillary relationship of the erupted teeth and, after their hopefully successful eruption, to the impacted teeth. The surgical procedure was performed under intravenous sedation [5], during which all the unerupted teeth on the right side of the mandible were exposed. The superficially located second molar and both premolars were treated by open exposure without attachment bonding. The first molar and second premolar were much more deeply placed and small attachments were bonded to their buccal surfaces, before the teeth were re-covered by full replacement of the surgical flap, to leave only the two twisted steel ligatures visible above the sutured mucosa (Figure 15.4h, i). These were fashioned into two small hooks close to their exit from the tissues. During the same surgical episode, the zygomatic plate was placed via an incision at the height of the sulcus, into the exposed inferior surface of the zygomatic arch (Figure 15.4j), with its free end drawn through attached gingiva close to the buccal side of the first permanent molar. At the next visit, sutures were removed and the patient was instructed in the placement of latex elastics between the hooked end of the zygomatic plate and the pigtail hooks in the lower jaw. Over the period of several months, traction was applied continuously and the first molar and second premolar teeth slowly responded. In the meantime, the first premolar and second molar teeth erupted normally without assistance. A fixed multi-bracketed appliance was subsequently placed in the maxillary arch to align the teeth (Figure 15.4k). A mandibular fixed appliance was placed only when the affected molar had fully erupted (Figure 15.4l–n). The treatment was brought to its successful conclusion at 24 months post-surgery, having achieved levelled right and left sides of the occlusal plane in both arches (Figure 15.4o–t).

Case 5: Severe trauma in infancy causing damage to anterior tooth buds The patient was a 10-year-old female who attended with the complaint that she had missing maxillary anterior teeth. She had suffered the ravages of caries in the deciduous dentition, the restorative and preventive treatment for which had been grossly neglected. From the patient’s history it was learned that the child had suffered severe trauma from a fall at the age of 4 years, when the four deciduous maxillary incisors had been lost. Since that time, she had been without her front teeth.

Extreme Impactions, Unusual Phenomena and Difficult Decisions  421 

(a)

(b)

(c)

(d)

(e) (f) Fig. 15.4  (a) An old panoramic view taken at age 8.6 years, three years before the patient was first seen by the author. (b–g) The initial orthodontic records taken at age 11.6 years. (h, i) At surgery, the mandibular canine, premolars and molars were exposed. Attachments were placed on second premolar and first molar, which were subsequently recovered with the soft tissue flap, to leave only their pigtail ligatures visible intra-orally. The other three teeth remained exposed in an open procedure. (j) The zygomatic plate was placed at the same visit. (k) Vertical elastic traction was applied by the patient from the pigtail ligature hooks to the TAD, simultaneously with the placement of an orthodontic appliance in the maxilla. (l–n) The closing stages of appliance therapy. (o–q) The immediate post-treatment outcome. Note the leveled occlusal plane achieved by the intrusion of the teeth in the right side of the maxilla. (r–t) lateral cephalogram and panoramic view, with a periapical film of the immediate area, taken 24 months after initiation of treatment.

422  Orthodontic Treatment of Impacted Teeth

(g) (h)

(i)

(j)

(k)

(l) Fig. 15.4  (Continued )

(m) (n)

(o)

(p)

(q)

(r)

(s) Fig. 15.4  (Continued )

(t)

424  Orthodontic Treatment of Impacted Teeth At examination, the mandibular counterparts of the missing incisors were over-erupted and retroclined, the maxillary arch was narrowed and a left side unilateral crossbite was present, with accompanying functional shift into full closure. The dental arches were restricted, with obvious potential crowding. The anterior maxillary bony ridge was very thin and underdeveloped, as is to be expected in the absence of teeth (Figure 15.5a-e). The radiographic records that accompanied the child included periapical, panoramic, cephalometric films and a CBCT scan (Figure 15.5f–j). These showed the presence of all permanent teeth, with anomalous development of the maxillary incisors and canines. The roots of the incisor teeth were very rudimentary, of a length to be expected at 3–4 years and with wide, open apices. These teeth were of abnormal form and they were located very high in the anterior maxilla close to the nasal floor. From the point of view of the child’s age, the eruption time of these teeth was long overdue, but from the length of their roots and their height in the alveolus, normal eruption could not be expected for 4–5 years, although the likelihood of this occurring at all was in considerable doubt. By contrast, the developmental status of her unaffected teeth, erupted and unerupted, was closely identified with the child’s chronological age. She had been taken to several orthodontists for treatment of the unerupted incisors, each of whom had been at a loss to prescribe appropriate treatment. When finally seen by the author, the conclusions drawn in relation to these teeth were that their development had been seriously hindered by the trauma that had occurred many years earlier, root development seemed to be adversely influenced by the proximity to the nasal floor and it could not be assumed that further root length development would occur, particularly given the apparent lack of eruptive potential of these teeth. To extract them, with the view to temporary prosthodontic replacement and, subsequently, with implant-supported crowns, would have caused very much more alveolar bone resorption and a large anterior bony defect. In light of the age of the child and her dental history, long-term wear of artificial prostheses would likely seriously reduce the prognosis for the survival of the other teeth. The prostheses would need to be present for 10 or more years, for the majority of which she would only be seen periodically by her dentist and therefore at considerable risk to develop further caries and gingival inflammation. On the other hand, a successful plan that attempted to enhance the attenuated innate eruptive force these teeth would bring with it the benefits of providing the child with her own natural and adequate, if temporary, anterior dental rehabilitation. Furthermore, this would be accompanied by excellent natural regeneration, contributing materially to the replacement and reconstitution of the defective alveolar bone height. True, the prognosis of these teeth was unknown

and the presence of orthodontic appliances in the mouth was also a risk factor for caries and gingival inflammation. Nevertheless, the expected treatment duration would be relatively short and the child would be under frequent and routine professional supervision, thereby reducing potential collateral damage to a minimum. Molar bands with a soldered palatal arch were cemented and a removable self-supporting labial arch slotted into the round buccal tubes on the bands, as with the first phase of CCD treatment (see Chapter 14). At surgery, the four maxillary incisors were exposed, bonded with small eyelet attachments and the full flap sutured back to its former place, with the twisted steel pigtail ligatures emanating from the sutured edge (Figure 15.5k–m). In subsequent visits, the pigtail ligatures were rolled up higher as the teeth responded and a mandibular Johnson modified appliance was placed with the intention of intruding and proclining the lower incisors (Figure 15.5n–p). Once the incisors had erupted, the eyelet attachments were substituted by orthodontic brackets on the incisors, which were then aligned and proclined labially (Figure 15.5q, r). At this point, sufficient space had been provided for the maxillary canine teeth which were impacted in the line of the arch, but which had also suffered anomalous development, as the result of the trauma, with an abnormal bucco-lingual crown angle and form. A second surgical procedure was performed to expose and bond attachments to both maxillary canines (Figure 15.5s, t) and this was followed by full alignment of the remaining teeth (Figure 15.5u). In this final stage, mandibular second premolars were extracted to provide space to eliminate the lower crowding and to permit the necessary anchorage for class 2 traction to control the overjet that was produced. Thus, in the final occlusion, the molars were brought to a full unit class 3 intercuspation, while the canines were normally related. In this manner, the orthodontic treatment was completed, with a good smile line relationship between the lower lip and the incisal edges (Figure 15.5v–y). Treatment duration was 26 months, with bonded 3-3 twistflex retainers in place in both arches. The posttreatment radiographs (Figure 15.5z–za) show considerable root growth which, it was believed, would have been a most unlikely outcome in the pre-treatment location of these severely damaged teeth. It is reasonable to speculate that this length of root may have been the reward generated by the extrusion of the teeth away from their anatomically limiting nasal floor. The follow-up records taken at age 17 years (i.e. four years post-treatment; Figure 15.5zb, zc) show further improvement in the root length, with the exception of the left central incisor, which required root canal treatment about nine months after the completion of the orthodontic treatment. The health of the teeth and surrounding tissues was good and the prognosis of the teeth appeared to be fairly good in the medium term. Nevertheless, there was a

Extreme Impactions, Unusual Phenomena and Difficult Decisions  425 

(a)

(b)

(c) (d) Fig. 15.5  (a–e) Intra-oral photographs transferred with the patient to the author, showing the initial condition. Note missing incisors and defective alveolar ridge, marked potential crowding, left side cross-bite and poor overall dental status. (f–h) Initial cephalometric, panoramic and maxillary anterior occlusal radiographs. (i, j) Transaxial and anterior coronal ‘slices’ from the CBCT to show incisor crown anomaly, very early root development and location of the teeth in relation to the nasal floor. (k, l) Bonding of eyelets to the exposed incisor crowns. (m) The surgical flap is fully sutured with only the twisted steel pigtail ligatures engaging the raised self-supporting labial arch. (n) An occlusal view of the active extrusion appliance one month post-surgery. (o) The anterior occlusal radiographic view shows the soldered palatal arch and the bonded eyelet attachments with their pigtail ligatures attached to the removable, self-supported, labial arch. (p) A month later, the mandibular Johnson modified appliance is placed. The anterior portion of the composite archwire may be seen to be expressing an intrusive influence on the anterior teeth. (q, r) Regular orthodontic (TipEdge plus) brackets are placed on the newly erupted teeth, the teeth are aligned and brought forward with buccal coil springs, to provide space for the canines. (s, t) The canines are exposed and bonded. (u) The final alignment showing lingual torqueing auxiliaries on the two canines. (v–x) The final alignment and occlusion. Note the anomalous long clinical crowns of the incisors and the crown/root angle of the canines and the mottled hypoplastic enamel. (y) The normal appearance of the patient’s smile and the excellent smile line. (z, za) Panoramic and periapical radiographs show the remarkable growth of the incisor roots. (zb, zc) Panoramic and periapical views taken four years post-treatment show further incisor root growth and the root canal treatment in the left central incisor.

426  Orthodontic Treatment of Impacted Teeth

(e)

(f)

(g)

(h)

(i)

(j)

Fig. 15.5  (Continued )

(k)

(l)

(m) (n)

(o)

(p)

(q)

(r)

Fig. 15.5  (Continued )

428  Orthodontic Treatment of Impacted Teeth

(s)

(t)

(u)

(v)

(w)

(x)

Fig. 15.5  (Continued )

Extreme Impactions, Unusual Phenomena and Difficult Decisions  429 

(y)

(za)

(zb) Fig. 15.5  (Continued )

(z)

430  Orthodontic Treatment of Impacted Teeth

(zc) Fig. 15.5  (Continued )

mildly marred appearance due to enamel hypoplasia and long clinical crowns of the affected teeth, despite the reshaping that was performed at that time.

Case 6: Buccal to the lateral incisor and palatal to the central incisor The 14-year-old male patient attended with what seemed a very minor problem. The dental arches in both jaws were well aligned and the occlusion textbook perfect. The posterior teeth met in a fully interdigitated class 1 occlusion, the incisor relations were ideal and there was a modicum of spacing generally in the dentition. The right maxillary canine had clearly recently shown its first signs of eruption into its place in the dental arch. The only flaw was to be found in the left anterior maxilla, where the canine had not erupted and the long axis of the lateral incisor appeared to be proceeding apically in a slowly rising distal and palatal direction, such that the root could be envisaged low down on the palatal surface, lingual to the line of the arch in the canine location (Figure 15.6a–e). Additionally, the tooth was rotated 30° mesio-labially, overlapping the adjacent central incisor. In a situation like this, the clinician should always suspect a labial canine, with the strong possibility of a canine-lateral incisor transposition. The scenario indicates a labially placed space-occupying body within the alveolus, the presence of which displaces the lateral incisor root palatally and distally. The displacing factor is usually an unerupted labial canine, which may be palpated on the labial side of the ridge, above the lateral incisor. However, on occasion, futile and vertically downward eruptive movement of a relatively high labial canine brings it more mesially and on the lingual side of a vertical root of the central incisor. Thus, the canine may end up straddling the ridge labial to the lateral incisor and lingual to the central incisor, in partial or complete

transposition with the lateral incisor (see Figures 7.3, 8.3, 12.16 and 12.19). Under these circumstances, the canine will not be palpable labially or palatally. The radiographs of the patient under discussion in the present context showed a full complement of teeth, including the unerupted third molars (Figure 15.6f, g). The right maxillary canine was unerupted, but could be seen to have an unimpeded line of approach to its place in the arch. The left maxillary canine was noted on the panoramic view to have migrated mesially and its crown tip was superimposed on the middle root area of the central incisor. On this film, the lateral incisor was tipped in the mesio-distal plane at an angle of 45° with its partially resorbed apex displaced into the area of the alveolar ridge reserved for the canine. From the CBCT, it was confirmed that the body of the canine was labial to the lateral incisor and its crown tip was palatal to the root of the central incisor (Figure 15.6h, i). Furthermore, root resorption of the lateral incisor root was identified as an oblique defect in the integrity of the normal root outline. A maxillary orthodontic appliance was placed on all the teeth from the first molars forward on each side, with the exception of the two canines and the ectopically oriented left lateral incisor. Immediately prior to the surgical exposure, a prepared auxiliary arch of 0.016 in gauge was tied into the brackets with elastic modules, in piggy-back fashion over the 0.020 in steel base arch, with its active loop lying horizontally, in its passive mode (Figure 15.6j). Surgical exposure was undertaken from the labial side of the ridge under local anaesthetic and an eyelet attachment was bonded by the author at the time (Figure 15.6k, l). Access to the canine was difficult, since coincidental exposure of the apically and widely diverging roots of the two incisors needed to be explicitly avoided. The pigtail ligature from the bonded attachment was directed labially and slightly distally and pushed through the oral mucosa area of the surgical flap at the height of the canine. Once the

Extreme Impactions, Unusual Phenomena and Difficult Decisions  431 

(a)

(b)

(c)

(d)

Fig. 15.6  (a–e) The initial intra-oral condition. (f) The relevant section of the cephalogram shows no A-P or height difference between the two superimposed maxillary canines. (g) The panoramic view confirms a full complement of teeth, with the maxillary right third molar ‘banana’-shaped (see Chapter 8). The left maxillary canine has tipped mesially and its tip superimposes on the distal aspect of the central incisor roots. The left lateral incisor root apex is tipped distally into the canine location, in partial transposition with the canine. This view gives no bucco-lingual information. (h) The anterior three-dimensional view taken from the CBCT reconstructions provides the essential missing bucco-lingual information needed to plan the treatment. The canine is labial to the root of the lateral incisor and palatal to the root of the central incisor. (i) The angle that exists between the adjacent surfaces, as indicated by the green dotted line drawn on the three-dimensional view from the left side, provides the ‘window of opportunity’ through which the canine may be accurately drawn high in a labial direction to resolve the impaction. (j) The auxiliary labial arch in its passive mode is ligated piggyback over the main arch, immediately before the surgical exposure begins. Note the absence of a bonded bracket on the left lateral incisor. (k) With the full flap exposure, the crown of the canine is exposed at a distance from its tip, which is buried between the roots of the incisors. The surgeon refrains from wider exposure and bone removal to protect the vitality of the teeth and to avoid exposing the root surface. (Surgery by Dr H. Samen.) (l) A small eyelet is bonded. The loop and terminal helix of the auxiliary archwire is seen in its passive horizontal mode. (m) Full replacement and suturing of the flap is performed, with the pigtail ligature pushed through the flap, high in the sulcus. The loop of the auxiliary archwire is turned upwards and engaged tightly in the shortened end of the pigtail ligature, thereby transferring labial traction force on the hidden canine. Note that the auxiliary loop is too high in the sulcus and caused subsequent pain and swelling of the lip tissue, necessitating removal of the pigtail ligature after three months, by which time the canine was palpable on the labial side. (n) The canine was now well clear of its earlier relationship with the palatally displaced root of the lateral incisor and a mesial uprighting spring was placed in the lateral incisor bracket. (o) With the lateral incisor fully uprighted, the canine was re-exposed and a new ligature applied. (p) The flap was again fully sutured back to its former place, with elastic thread drawing the pigtail distally towards the canine location. There are auxiliaries mesially uprighting the incisor and distally uprighting the first premolar, to clear a path to accommodate the distally and vertically moving canine. (q) With the canine close to its intended location, a bracket is substituted for the eyelet in the closing stages of the case. (r–t) The alignment of the teeth on the day of debanding and prior to the placement of removable finishing and retaining appliances. (u) Periapical views of the anterior maxilla. (v) Panoramic view shows good parallelism of the teeth concerned. Note the ‘banana’-shaped right maxillary third molar. (w) The post-treatment cephalogram.

432  Orthodontic Treatment of Impacted Teeth

(e)

(f)

(g)

(h) The window of opportunity

(i)

(k) Fig. 15.6  (Continued )

(j)

(l)

Extreme Impactions, Unusual Phenomena and Difficult Decisions  433 

(m)

(n)

(o) (p)

(q) Fig. 15.6  (Continued )

(r)

434  Orthodontic Treatment of Impacted Teeth

(s)

(t)

(u)

(v) (w) Fig. 15.6  (Continued )

Extreme Impactions, Unusual Phenomena and Difficult Decisions  435  attached gingival flap was fully sutured to its former place, the pigtail ligature could be seen to pierce the oral mucosa, high up in the sulcus and was the only means of communication with the impacted tooth. The loop of the auxiliary archwire was then raised, turned towards the pigtail ligature and ensnared by turning the pigtail around its terminal loop, as close as possible to the oral mucosa (Figure 15.6m). This had the effect of applying traction to the canine, high up and in a labial direction, through the ‘window of opportunity’ provided by the widely divergent roots of the two incisors in the mesio-distal and bucco-lingual planes (Figure 15.6i). In the subsequent 2–3 months the patient had considerable discomfort due to ulceration of the highly mobile oral mucosa from what transpired to be excessive length of the loop of the auxiliary archwire. The inflamed tissue grew over the loop and the auxiliary archwire had to be removed. However, at this point the canine was palpable on the buccal side of the ridge, which meant that it had moved from the palatal side of the central incisor and was also now clear of the root of the lateral incisor. Accordingly, a bracket was placed on the lateral incisor. It was aligned and its root mesially uprighted with relative ease, using an auxiliary uprighting spring (Figure 15.6n). The canine was then reexposed with an apically repositioned flap and its ligation renewed to permit distally and vertically downward traction towards its place in the arch (Figure 15.6o, p). With the eruption of the canine into its appropriate location, a

bracket was substituted for the eyelet attachment (Figure 15.6q) and, as expected in the finishing stage, much labial root torque of the lateral incisor and lingual root torque of the canine were then applied. After 25 months of treatment, the fixed appliances were removed (Figure 15.6r–t) and removable finishing and retaining appliances were placed. The radiographs show good root parallelism and good intra- and inter-maxillary relationships of the teeth in the immediate area of concern (Figure 15.6u–w). The lateral incisor, which had suffered pre-treatment root resorption, remained with the same degree of root shortening, while some minimal and clinically insignificant resorptive blunting was noted of the apices of the maxillary central incisors.

References 1.  Dankner E, Harari D, Rotstein I, Dens evaginatus of anterior teeth. Literature review and radiographic survey of 15,000 teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endod, 1996; 81; 472–476. 2.  Danesh G, Schrijnemakers T, Lippod C, Shafer E. A fused maxillary central incisor with dens evaginatus as a talon cusp. Angle Orthod 2007, 77: 176–180. 3.  Abbott PV, Labial and palatal ‘talon cusps’ on the same tooth: a case report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998; 85: 726–730. 4.  Becker A, Karnei-R’em RM: The effects of infraocclusion: part 2 – the type of movement of the adjacent teeth and their vertical development. American Journal of Orthodontics 1992; 102: 302–309. 5.  Chaushu S, Gozal D, Becker A. Intravenous sedation: an adjunct to enable orthodontic treatment for children with disabilities. European Journal of Orthodontics 2002; 24: 81–89.

Index Note: Page numbers in italic refer to tables and the legends of illustrations.

abscesses, periapical, maxillary canines 129 acrylic buttons, maxillary central incisors, non-eruption 92 acrylic plates, pack holding 32 acrylic tooth, for maxillary central incisor impaction (adults) 268, 270 active arm, ballista spring 150–1 active palatal arches lingual appliances and 286 maxillary canines, palatal impaction, Group 2 149–50 active removable plate, for maxillary central incisor impaction (adults) 268 adults 262–82, 322 anchor units 287 cleidocranial dysplasia 397–403 lingual appliances 284 age (dental), see dental age age (of patient) 322 agenesis, mandibular second premolars 223 aggressive juvenile periodontitis 412, 413–15 ALARA principle, radiation dosage 27 alignment, maxillary central incisors, after treatment 86 alveoli, see bone ameloblastic fibro-odontoma 257–9 amputations, maxillary central incisors apices 103, 105–6 crowns 108 anchor units 56–7 adults 287 anchorage 347–51, 352 indirect 62, 63 molars as (adults) 270–1 reduction of intrusion 360 skeletal, for infra-occlusion 252 see also headgear appliances; implants; temporary anchorage devices Angle’s class 2 malocclusion 8 ankylosis causes 52 failed treatment and 321, 322 iatrogenic 260 infra-occlusion 33, 252 invasive cervical root resorption and 204 mandibular second molar impaction 240–3 trauma 359, 360, 363 see also replacement resorption

anomalies 322 incisors, root resorption and 177 maxillary central incisors 407–12 maxillary third molars 246, 250 midline anomalies 71–2 second premolars 223 see also cleidocranial dysplasia anterior occlusal view, maxillary arch 12–13 anterior palatine artery 152 antero-posterior radiographs 18 anti-invasion factor 201 apical repositioning of flaps 34, 40–2 central maxillary incisor non-eruption 102 palatal impaction of canines 154 traction and 62 apices assessing dental age 3–5 maxillary central incisors, amputation 103, 105–6 three-dimensional diagnosis 20, 327–8 appearance, see facial appearance arch length, buccally-displaced maxillary canines 212 archwires 56–7 central maxillary incisor non-eruption 87–100, 100–1 cleidocranial dysplasia 382, 383–4, 384, 385, 387, 388–92 with elastic ties 61 for Johnson’s modified twin-wire arch 88 labial, on molar bands 363, 364–6 lingual appliances 284 for mandibular second molar impaction 243, 244 for maxillary canine impaction 134, 136, 143, 169 for maxillary central incisor impaction (adults) 268 super-elastic, lingual appliances and 286 see also labial auxiliary arch; palatal auxiliary arch arrested development of roots 78, 79–80 attachments (orthodontic) 44, 57–9 bonding 49–53, 58 adults 273 closed eruption technique 36–7 by surgeons 36, 40

Orthodontic Treatment of Impacted Teeth, Third Edition. Adrian Becker. © 2012 Adrian Becker. Published 2012 by Blackwell Publishing Ltd.

auxiliary arches lingual appliances and 285–6 palatal 52 see also labial auxiliary arch avulsion, central incisors 72, 80, 100–1, 363–9 axial plane, radiography vs CT 25 background radiation 26 ballista springs lingual appliances with 287, 288, 290 maxillary canines, palatal impaction, Group 2 149, 150–1 banana-shaped crowns, maxillary third molars 246, 250 bands (orthodontic) 57–8 cleidocranial dysplasia 382, 383–4 eyelets attached 59 maxillary first molar impaction 240 molar, labial archwire on 363, 364–6 bars (space-holding devices) for mandibular second premolar impaction 223 transpalatal, maxillary central incisor impaction (adults) 267, 270 Begg brackets, for Johnson’s twin-wire arch 88, 96 Belfast–Hamburg approach, cleidocranial dysplasia 377–9, 396 bilateral dilaceration of maxillary central incisors 75–6 bitewing radiographs, radiation dosage 26t bleaching, invasive cervical root resorption and 201 blood supply 42 bloodless field 50 see also haemostasis bonded wire frames, trauma 362–3 bonded wire retainers, for mandibular second molar impaction 243 bonding agents 49, 50 bonding of attachments 49–53, 58 adults 273 closed eruption technique 36–7 by surgeons 36, 40 bone aggressive juvenile periodontitis 412, 413–15 anchorage for infra-occlusion 252

438  Index buccally-displaced maxillary canines and 216 cleidocranial dysplasia 45, 378, 379, 396 cysts, effect of 294, 309, 310 defects mandibular second premolar extraction 222 from surgical exposure 42 dilaceration of maxillary central incisors 322, 323 eruption through 45 grafts bovine 412, 413–15 eruption through 45 infra-occlusion of deciduous teeth 230–5 maxillary canines eruption 138 palatal impaction, Group 4 162 moving teeth across midline 412 obstruction by 32–3 relative height, maxillary central incisors 104 removal 44 palatal impaction of canines, Group 3 155 reparatory deposition 44–5 bovine bone grafts 412, 413–15 box elastics vertical, maxillary central incisors 105 brackets 37, 49–50, 52, 58–9 cyst cases 310, 316–18 dehiscence and buttonholing 37, 38 I2C transpositions and 164 for Johnson’s modified twin-wire arch 88, 96 lingual appliances and 286, 290 maxillary canines, palatal impaction, Group 1 140 maxillary central incisors impaction (adults) 269 non-eruption 87 tweezers to hold 49, 51 wrong placement 347, 348–50 braiding, pigtails 59 bridges anterior maxilla 105 root resorption and 178 buccal approach access 40–2 apically repositioned flap 34 cleidocranial dysplasia 45 discomfort after 48 flap closure 40, 42 maxillary canines 42 palatal impaction, Group 3 154–5 buccal canines 220–2 maxillary 115, 120–1, 212–17, 330, 332–5, 336, 337 surgical exposure, misdiagnosis 330, 331, 332–5, 336, 337 see also labial canines

buccal object rule buccally-displaced maxillary canines 213 maxillary second premolar impaction 230 buccal tubes cleidocranial dysplasia 382, 383–4, 387 Johnson’s twin-wire arch 92 mandibular second molar impaction 243 bucco-lingual plane computerized tomography 21, 25, 26 three-dimensional diagnosis 20–1 buttonholing, from orthodontic brackets 37, 38 buttons acrylic, maxillary central incisors non-eruption 92 canine–first premolar transposition 121, 162, 167, 169, 216–17 canine–lateral incisor (I2C) transpositions 163, 164, 213, 430–5 canine-to-incisor index formula 17 canines cleidocranial dysplasia 388–92 computerized tomography 21 deciduous, root resorption of permanent teeth and 178 duration of treatment 321 adults 269–70 maxillary, group 6 169–70 root resorption 139 first premolars affecting 322 lingual appliances and impaction 284–92 open exposure techniques 34 surgical exposure, outcomes 38 transpalatal arch, traction 180 see also mandibular canines; maxillary canines cantilever springs, maxillary first molar impaction 240 caries, deciduous teeth 5 maxillary canines 123–4 casts, cleidocranial dysplasia 383–4 CB MercuRay, computerized tomography 22t cemento-enamel junction, packing 30 cementum, cleidocranial dysplasia 373 central incisors, see maxillary incisors, central cephalograms lateral 18, 19, 20 computerized tomography vs 23–4 maxillary central incisors 83 parallax radiography 16 radiographs at right angles 19 postero-anterior 19–20 radiation dosage 26t using CT machines 26 cerebral palsy, trauma 362–3, 364–6 cervical root resorption, invasive 197–206, 324–5, 326

chains 59, 61 see also elastic chains; gold chains channelling of bone, palatal impaction of canines 155 child abuse 81 circular incisions surgical exposure 38 see also open exposure techniques Clark’s tube-shift method, see parallax radiography clasps, maxillary first molar impaction 240 ‘classic’ dilaceration 74, 83 bilateral 75–6 clavicles, cleidocranial dysplasia 371, 372 cleaning of teeth, for attachment bonding 36–7, 50 cleidocranial dysplasia 45, 370–405 patient variation 397–403 pre-first phase treatment 397 clinical examination, see examination closed eruption technique 34–8 duration 38 lingual appliances and 284–5, 288 maxillary canines, palatal impaction, Group 3 157–9 open exposure techniques vs 39, 44 soft tissue resistance 62 closure, flaps 40 Cochrane Data Base Collaboration, on surgical exposure 39–40 Coe PackTM 7, 32 collimation, computerized tomography 22t complete flap closure 40, 48, 65–6 compliance age of patient 322 see also oral hygiene; patient skills composite disguise of neglected impaction 263 splinting for trauma 360 computerized tomography (CT) 21–7 maxillary central incisors 83, 108 root resorption 175–6 see also cone beam computerized tomography cone beam computerized tomography 21–7 canines 322 CPm1 transposition 167 maxillary arch 12 maxillary canines 127 maxillary central incisors 108 second opinions 356 superfluous films 27 congenital absence of maxillary incisors 71–2 role in maxillary canine impaction 117–20 coniform teeth, dental age and 4 connectors, see elastic ties; gold chains; intermediaries; ligature wires consent 48 emergency treatment 363 explaining radiation dosage 26 see also patient involvement

Index  439  Crescini’s technique 34–5, 45, 155–6 cross-bite, maxillary central incisors, treatment timing 86 crowding apparent 112 buccally-displaced maxillary canines and 212–13 in cleidocranial dysplasia 380–1 mandibular canine impaction 222 mandibular second molar impaction 240 maxillary canine impaction 42, 127, 128 theory 115 treatment 135 maxillary second molars 246 see also space loss crowns amputation 108 artificial 108 banana-shaped, maxillary third molars 246, 250 location, misdiagnosis 82 maxillary canines, mesial displacement, palatal impaction Group 1 142–3 maxillary central incisors, dilaceration 107 resorption 43, 246–50 deciduous maxillary canines 124 pre-eruptive invasive 206, 207–10, 251 wide, mandibular second molar impaction 240 curative enucleation of cyst lining 297 cysts 8, 32, 257–9, 293–318, 325 dilaceration of maxillary central incisors 74–5 prognosis of affected teeth 299–304 see also dentigerous cysts; radicular cysts deciduous teeth brackets and 87 cleidocranial dysplasia 373 maxillary canines 123–5 non-resorption of roots 115 non-vital 116 palpation 126 root resorption of permanent teeth and 178 perforation of molars 240 retention 2, 3, 4–5, 251 second molars, maxillary first molar impaction 235–8 see also extractions, deciduous teeth; infra-occlusion, deciduous teeth; over-retention definitions 3, 5–7 dehiscence mucosa, from orthodontic brackets 37, 38 roots, CPm1 transposition 167 delayed eruption 2, 3, 56 cleidocranial dysplasia 371 maxillary central incisors, after treatment 86 see also late development

dens evaginatus 407–12 dental age 2–5 cleidocranial dysplasia 379 maxillary canines buccally-displaced 212 impaction 122 dental follicles 42–5 deciduous maxillary canines, caries 123–4 dentigerous cysts vs 296 enlargement mandibular second molar impaction 240 root resorption and 177, 194–6 dentigerous cysts 65–6, 294–6, 298, 317 deciduous maxillary canines 123–4, 129 mandibular second molar impaction 240, 247 marsupialization 298–9, 309, 317, 318 neoplastic change 317, 318 dentin, invasive cervical root resorption and 201 dentures cleidocranial dysplasia 376 disguise of neglected impaction 263 for maxillary central incisor impaction (adults) 268 temporary 105 see also prostheses desiccation 38, 44 for attachment bonding 50 causes of ankylosis 52 invasive cervical root resorption and 204 development late 5 maxillary canine impaction and 122, 134 see also delayed eruption normal 2–5, 112–14 roots 2, 42–3 arrested 78, 79–80 devitalization maxillary central incisors 104 see also vitality of pulp differential enlargement, radiography 16–17 digital volume tomographic machines 21–2 radiation dosage 26 dilaceration of maxillary central incisors 73–6, 304, 305, 309, 322, 323 apices 105 computerized tomography 83 crowns 107 Jerusalem hypothesis 76–7, 78 palpation 81–2 radiography 19, 74, 83 roots 106–7 surgery 103–4 treatment benefits 105–6 treatment duration 103 distal displacement, buccally-displaced maxillary canines and 216–17 distraction osteogenesis 252

drainage of cysts 309, 310 dressings 7 drying, see desiccation duration of treatment 56 canine impaction 321 adults 269–70 maxillary, group 6 169–70 root resorption 139 cleidocranial dysplasia 388, 403 maxillary central incisor impaction 103 surgical exposure 37–8 ectopia canines, effect of central maxillary incisor impaction 84–5 extreme 323–7, 328, 329 mandibular second premolars, lingual 224–5 tooth bud 72–3 dilaceration of maxillary central incisors 75 elastic chains 59, 65–6 for buccally-displaced mandibular canines 220 for central maxillary incisor impaction 92 for Johnson’s twin-wire arch 92 for mandibular second premolar impaction 224 temporary anchorage devices 62, 63 elastic rings, maxillary first molar impaction 240 elastic ties 59–62, 65–6, 351 cleidocranial dysplasia 384–6 maxillary canines, palatal impaction 180 Group 1 140–2 maxillary central incisors impaction (adults) 267 non-eruption 93 periodontitis case 412, 413–15 rubber bands, to mandibular removable appliance 151 for traumatic intrusion 363 unopposed tooth (adults) 276 vertical box elastics, maxillary central incisors 105 see also intermaxillary elastics; superelastic wires elevators causes of ankylosis 52 invasive cervical root resorption and 204 emergency treatment 169, 358, 362–3 cleidocranial dysplasia 397 radiography 74 enamel cuticle 43 contact with soft tissue 43 invasive cervical root resorption and 201 resorption 246–50 enlargement (differential), radiography 16–17

440  Index enucleation of cysts 297, 317 epithelial rests of Malassez 296 epithelium surgical healing 43 see also junctional epithelium eruption 43, 45 after traumatic intrusion 358, 359 cleidocranial dysplasia, assistance 380 dental age and 2 dentigerous cysts on 294–5 ectopic tooth bud 72–3 maxillary canines 138 lingual appliances and 285 long path theory 114–15 maxillary central incisors, after treatment 86 neglected impaction 263 normal timings 71 odontomes on 6 premature 5 primary failure 252–3, 256 resorption of neighbouring roots 125 speeding after surgical exposure 38 spontaneous 56 in cleidocranial dysplasia 376 supernumerary teeth and 6 see also delayed eruption; non-eruption; over-eruption eruption cysts 294–5 etchants 50 causes of ankylosis 52 invasive cervical root resorption and 204 orthophosphoric acid gel 36 ethnicity, impaction of maxillary canines 111 eugenol, effect on bonding 36 examination invasive cervical root resorption 201–6 maxillary incisors 125, 126 non-eruption 81–2 expert opinions 355–6 exposure, see surgical exposure extra-oral radiographs 13–14 extractions buccally-displaced maxillary canines and 216 cyst cases 303, 304, 305–8, 309 deciduous teeth 5, 6 canine impaction and 127–30, 135–7 cleidocranial dysplasia 376 healing after 30 infra-occluded 231–3, 234 mandibular canine impaction 218 mandibular second premolar impaction 222 molars 115, 129 second 234 premolars 222 prevention of canine impaction 129 for tunnel approach 155 dilaceration of maxillary central incisors, for reshaping 106

impacted teeth 178 mandibular second premolars 222, 224 maxillary central incisors (adults) 267 intruded tooth 359 mandibular second molars 246 mandibular third molar 241 premolars 42, 136, 222, 224, 249 resorbed tooth 179 third molars 43, 249 ‘eye-for-an-eye’ tooth 329–30 eyelets 49, 50, 59 brackets vs 58 Crescini’s technique 35 cyst cases 316–18 maxillary canines, palatal impaction Group 1 140 Group 2 151, 154 Group 3 156, 159 maxillary central incisors 105 root resorption and 180 face masks, cleidocranial dysplasia, pre-first phase treatment 397 facial appearance cleidocranial dysplasia 373, 375, 394–5 motivation and 7, 8 facial swelling, cysts 309, 310 failures 319–56 maxillary central incisor impaction (adults) 270 positional misdiagnosis 20 field of view, computerized tomography 22t first molars infra-occlusion of second primary molar 234, 235–6 mandibular first molars, infra-occlusion 325 see also maxillary molars, first first premolars affecting canines 322 see also canine–first premolar transposition flaps 7 apical repositioning 34, 40–2 central maxillary incisor non-eruption 103 palatal impaction of canines 154 traction and 62 central maxillary incisor non-eruption 93 cleidocranial dysplasia 379–80 closed eruption technique 34, 35, 36, 37, 38 closure 40 high unerupted teeth 41–2 maxillary canines buccally-displaced 217 palatal impaction Group 1 140 Group 2 143–8, 149 Group 3 154

open exposure technique 34 wide 36, 37, 38, 44, 45 ‘flipper’ partial denture 263, 268 follicles, see dental follicles follow-up cleidocranial dysplasia 392 root resorption and 340 force decay, elastic ties 60 forced eruption, maxillary canines 138 forceps 51 fracture incisors, cerebral palsy 362–3 labial plate 73 frames/revolution, computerized tomography 22t free gingiva 43 free-sliding wires, for mandibular second molar impaction 243 full flap closure 40, 48, 65–6 gender differences maxillary canines buccally-displaced 212 impaction 111, 120 dental age 122 root resorption 177 general dental practitioners 7 genetic counselling, cleidocranial dysplasia 382 gingiva after open tooth exposure 34 attachments 43 cleidocranial dysplasia 378 effect of brackets 58–9 maxillary canines, palatal impaction, Group 2 154 at tooth eruption 43 gold chains 59 closed eruption technique 34, 35 maxillary canines, palatal impaction, Group 3 156 grafts (bone) bovine 412, 413–15 eruption through 45 guidance theory, maxillary canine impaction 117–20, 120–1, 122–3, 130 guided tissue regeneration, cysts 299 haemostasis 37–8, 50 hair dryers 50 hard tissue obstruction 32–3 headgear appliances for mandibular second molar impaction 244, 245 maxillary canine impaction 138 healing deciduous tooth extractions 30 epithelium 43 by primary intention 48 by second intention 36 hemidesmosomes 43

Index  441  heredity mandibular second molar impaction 240 maxillary canine displacement 120–1 Hertwig’s root sheath Jerusalem hypothesis and 77 trauma 78 high unerupted teeth flaps 41–2 maxillary canines 329–30, 412–19 history-taking 80–1 holoprosencephaly 71–2 hooks 65–6 central maxillary incisor non-eruption 93 cleidocranial dysplasia 382, 383–4 ‘hourglass’ ridge 82 i-CAT, computerized tomography 22t iatrogenic ankylosis 260 Iluma DentalCAT, computerized tomography 22t impaction, geographical variations in meaning 251 implants adults 276–81 for maxillary central incisor impaction 267 cleidocranial dysplasia and 376 lingual appliances with 287–90 temporary anchorage devices 62 traction for infra-occlusion 252, 256, 257–9 impressions, for Johnson’s modified twinwire arch 88 incidental findings, cone beam computerized tomography 26 incisors anomalies, root resorption and 177 in cleidocranial dysplasia 380–1, 382–8 fracture, cerebral palsy 362–3 open exposure techniques, closed eruption technique vs 39 radiography 19 vs computerized tomography 25 panoramic views 20 parallax 15 root resorption 340 anomalies and 177 computerized tomography 21, 22 maxillary canine impaction 124–5, 132–3, 134, 135, 169–70 see also canine-to-incisor index formula; maxillary incisors inclusion (term) 252 indirect anchorage 62, 63 infections cyst surgery 297 neural spread 251 inferior alveolar canal 22–3 inflammation after open exposure techniques 36 dentigerous cysts 296 invasive cervical root resorption 201

maxillary canines, palatal impaction, Group 3 157, 351, 353 infra-bony pockets 138, 204–6 infra-occlusion deciduous teeth 64, 67–8, 230–5 mandibular molars 122 invasive cervical root resorption and 201, 202, 325 permanent teeth 33, 251–60 mandibular first molar 325 maxillary premolars 236–7 see also open bite innervation 251 transmigrated mandibular canines 222 intermaxillary elastics 62, 63, 65–6, 347 cleidocranial dysplasia 386, 389, 393 maxillary canines, palatal impaction Group 2 151 Group 4 161–2 intermaxillary traction for infra-occlusion 252 for mandibular second molar impaction 245, 249 intermediaries (connectors) 59 see also elastic ties; gold chains; ligature wires intrusion reactive 62, 197, 252, 273, 347 traumatic 78–80, 358–69 invasive cervical root resorption 197–206, 324–5, 326 invasive coronal resorption, pre-eruptive 206, 207–10, 250 Jerusalem approach, cleidocranial dysplasia 379–80, 381–93, 393–6 Jerusalem hypothesis, dilaceration of maxillary central incisors 76–7, 78 Johnson’s twin-wire arch 88–100, 107 cleidocranial dysplasia 382, 388 junctional epithelium 43 invasive cervical root resorption 197–201 juvenile periodontitis 412, 413–15 Kokich technique 44, 180 labial approach, maxillary canines, palatal impaction, Group 5 164 labial archwire, on molar bands 363, 364–6 labial auxiliary arch 49–50 I2C transpositions 164, 166–7 mandibular second premolar impaction 225 maxillary canine impaction 143, 144, 150–1, 351, 354 labial canines 12–13, 430–5 see also buccal canines labial impaction, maxillary canine 412–19 labial plate, fracture 73 lamina dura 3 lasso wires 57

late development 5 maxillary canine impaction and 122, 134 see also delayed eruption lateral cephalograms 18, 19, 20 computerized tomography vs 23–4 maxillary central incisors 83 parallax radiography 16 radiographs at right angles 19 ligature directors 51 ligature wires 49, 50, 59, 65–6 closed eruption technique 34, 35 maxillary canines, palatal impaction Group 2 149 Group 3 156 light-cured adhesives 51 lingual appliances, canine impaction and 284–92 lingual arches infra-occluded deciduous teeth 67, 68 mandibular second molar impaction 243 mandibular second premolar impaction 224 maxillary second molar impaction 234, 235 lingual ectopia, mandibular second premolars 224–5 lingual impaction, mandibular canines 218–20 lingual mucosa, mandibular canines under 217 liquid etchant, causes of ankylosis 52 local anaesthesia, initiation of traction 38 luxation infra-occlusion 33, 252 see also intrusion magnets 64–9 magnification (effect), radiography 16–17 Malassez, epithelial rests of 296 malocclusions 56–7 Angle’s class 2 8 mandibular second molar impaction and 246–9 maxillary incisors, class 2 division 2 163 mandibular arch, occlusal radiographs 11–12 mandibular canines 217–22 cleidocranial dysplasia 387 crossing midline 217, 218, 328 mandibular molars deciduous, infra-occlusion 122 first, infra-occlusion 325 impaction with over-eruption of opposing teeth 419–20 second 240–9 failed treatment 320 pressure packs 32 third 249 extraction 243 orthodontics 246 timing of development 3, 4 mandibular posterior area, radiography 18, 19

442  Index mandibular premolars exposure alone 30 impaction with over-eruption of opposing teeth 419–20 second 222–5, 226, 227–9 abnormal orientation 222–5 infra-occlusion of second primary molar 234 late-developing 5 timing of development 3, 4 mandibular removable appliance, maxillary canines, palatal impaction, Group 2 151 markers, computerized tomography 23 marsupialization, dentigerous cysts 298–9, 309, 317, 318 Matthieu forceps 51 maxillary arch, occlusal radiographs 12–13 maxillary canines buccal displacement 212–17, 330, 336, 337 computerized tomography 22, 23–4, 25 Crescini’s technique 34–5 crowding 42 effect of central maxillary incisor impaction 84–5 eruption 138 lingual appliances and 285 long path theory 114–15 extreme ectopia 328, 329 impaction adults 269–70, 271–2 labial 412–19 in line of arch 212 see also maxillary canines, palatal impaction labial auxiliary arch, treatment 143, 144, 150–1, 351, 354 labial impaction 412–19 malocclusions and 56–7 open exposure techniques, closed eruption technique vs 39 palatal impaction 110–72 adults 269 buccal impaction vs 212 complications 123–5 diagnosis 125–7 elastic ties 140–2, 180 Group 1 140–43 Group 2 143–54 lingual appliances 290–2 mucosa 151, 351 Group 3 154–9, 330–8 inflammation 157, 351, 353 mucosa 159, 351 Group 4 159–62 Group 5 162–9 Group 6 169–70 see also roots, resorption prevention 127–32 prognosis 138

resorption of neighbouring roots, see roots, resorption theories 114–21 treatment 132–6 parallax radiography 14–15, 16–17, 127 buccally-displaced 213–16 periodontitis case 412, 413–15 radiographs at right angles 18, 19, 127 root resorption of neighbours 45 surgical exposure, see surgical exposure, maxillary canines see also canine–first premolar transposition; canine–lateral incisor transpositions maxillary incisors central 70–109 anchor units and 57 anomalies 407–12 development 112–14 diagnosis 80–3 dilaceration, see dilaceration of maxillary central incisors examination 125 exposure alone 30, 31 maxillary canine abnormalities associated 123 neglected impaction 263–9, 270 prognosis 102–8 treatment 86–100 benefits 105–6 duration 103 results 86 stages 103 timing 83–5, 86 lateral buccal canines and 212–13 deciduous teeth, extraction 129–30 development 113 examination 125, 126 late-developing 5 maxillary canine impaction and 117–20, 134–5, 338 timing of development 3, 4 see also canine–lateral incisor transpositions malocclusions, class 2 division 2 163 open exposure techniques, closed eruption technique vs 39 trauma 420–30 maxillary molars first 235–40 maxillary second molar impaction against 249 second 249 third, anomalies 249, 250 maxillary premolars, second 225–35 infra-occlusion of premolars 236–7 infra-occlusion of second primary molar 234, 235–6 Melbourne approach, cleidocranial dysplasia 377 mesh 49 eyelets attached 59

mesial displacement buccally-displaced maxillary canines and 213–16, 330 maxillary canine crowns, palatal impaction, Group 1 142–3 mesial/distal root length differential, mandibular second molar impaction 240 mesial movement, molars 225 mesiodens 84 micro-screws, lingual appliances with 287 microforms 3 mid-buccal aspect, bonding site 51, 52 mid-plants 279, 280 midline mandibular canines crossing 217, 218, 328 maxillary canines crossing 328 moving teeth across 412 midline anomalies 71–2 midline correction, maxillary central incisor impaction (adults) 267 migrated buccally-displaced mandibular canines 220–2 mini-screws, lingual appliances with 287 missing teeth, maxillary canine impaction and 121–2 mixed dentition stage 71 mobility, maxillary canines 126 molar bands, labial archwire on 363, 364–6 molars as anchorage, adults 270–1 cleidocranial dysplasia 371, 380, 382, 392, 393 supplemental 393 deciduous, extraction 115, 129 mesial movement 225 see also first molars; mandibular molars; maxillary molars; third molars monster tooth 407–12 mortality risk, radiography vs CT 21 mosquito forceps 51 motivation of patients 8–9 impacted maxillary canines 111, 133 impacted maxillary central incisors (adults) 267 movies, computerized tomography 22t muco-gingival attachment 33–4 muco-gingival flaps, apical repositioning 34 mucosa cleidocranial dysplasia 378 irritation by brackets 58 maxillary canines, palatal impaction Group 2 151, 351 Group 3 159, 351 Nance buttons, maxillary central incisors non-eruption 92 nasal floor level, maxillary canine at 412–19 Nasmyth’s membrane 36 natural background radiation 26

Index  443  neglected impaction 263–70 neoplastic change, dentigerous cysts 317, 318 nerve supply, see innervation NewTom machines computerized tomography 22t radiation dosage 26 nickel-titanium wires 61 Johnson’s twin-wire arch 88 maxillary canines, palatal impaction, Group 1 140–2 no-mix systems, bonding agents 50 non-eruption causes 320–1 cleidocranial dysplasia 373, 380 examination 81–2 maxillary central incisors, archwires 87–100, 100–1 non-extraction, root resorption 179 non-treatment, see ‘wait and see’ approach obliquity extra-oral radiographs 13–14 periapical radiographs 11 obstructive impaction 32–3 maxillary central incisors 72–3, 81 previous trauma 104 prognosis 102–4 occlusal radiographs 11–13, 18, 19, 20 anterior, in parallax radiography 15, 82 maxillary central incisors 82 radiation dosage 26t odontomes 8, 72 dilaceration of maxillary central incisors 74–5 impaction of maxillary canines 111, 112 mandibular canine impaction 219, 220 periapical radiographs 11 radiography 82 on tooth eruption 6 oligodontia 3 open bite 347 maxillary central incisor impaction (adults) 267 see also infra-occlusion open eruption technique, exposure 33–4 open exposure techniques advantages and disadvantages 48 closed eruption technique vs 39, 44 soft tissue resistance 62 duration 38 inflammation after 36 palatal side 34, 40 see also circular incisions oral hygiene 9, 104, 133 cleidocranial dysplasia 382 CPm1 transposition 169 surgical exposure and 40 orbit, tooth close to 329–30 orthodontic bands, see bands orthodontists 7 closed eruption technique and 36, 38 cooperation with surgeons 48–52

cyst cases and 299, 317–18 presence at surgery 36, 52–3, 204, 260 cleidocranial dysplasia 378 three-dimensional diagnosis and 20 trauma and 365 views on mesiodens 84 orthophosphoric acid gel 36 over-eruption 63, 65–6 mandibular premolars and molars 419–20 over-jet, adults 269 over-retention of deciduous teeth 2, 3, 5, 7, 8, 13, 30–2, 73, 112 cleidocranial dysplasia 373 mandibular molars 122 mandibular second premolar impaction 222–3 role in maxillary canine impaction 118, 120, 214 overclosure, cleidocranial dysplasia 399 packs 30–2 Belfast–Hamburg approach 377, 378 for crown resorption 250 effect on bonding 36 effect on outcomes 43–4 for mandibular second premolar impaction 224 maxillary canines, palatal impaction, Group 4 162 palatal side impactions 40 periodontal 7 paediatric dentists, trauma and 365 pain cleidocranial dysplasia 397 maxillary canines, palatal impaction, Group 3 157 pigtail manipulation 51 postoperative 48, 355 palatal approach maxillary canines, palatal impaction, Group 3 156–9, 330–8 open exposure techniques 34, 40 palatal arches for maxillary central incisor impaction (adults) 270 see also soldered palatal arch see also active palatal arch; transpalatal arch palatal auxiliary arch 51 palatal displacement canine 430–5 maxillary second premolar impaction 230 palatal impaction, canines, see maxillary canines, palatal impaction palatal root displacement, maxillary canines, palatal impaction Group 1 143 Group 2 154 palatally oriented dilaceration of maxillary central incisors 74, 75

palato-labial partial avulsion 72, 80, 100–1, 363–9 palpation maxillary canines 126, 127 maxillary central incisors 81–2 panoramic views 13 buccally-displaced maxillary canines 213 computerized tomography vs 23–4, 25 with CT machines 26 incisors 20 mandibular second molar impaction 246 maxillary canines 127 maxillary second premolar impaction 230 parallax radiography 15–17 radiation dosage 26t radiographs at right angles 18 papilla, dental 3 parallax radiography 14–17 anterior occlusal radiographs 15, 82 maxillary canines 14–15, 16–17, 127 buccally-displaced 213–16 parathyroid hormone receptor 1 gene mutations 252 partial anodontia 3 partial avulsion, palato-labial 72, 80, 100–1, 363–9 partial dentures 263, 268 partial flap closure 40 partial thickness surgical flaps 34 Parylene coating, magnets 68 patient involvement 8–9 impacted maxillary canines 111, 133 impacted maxillary central incisors, adults 267 see also compliance; consent patient skills for mandibular second molar impaction 245–6 unopposed tooth, adults 276 peg-shaped teeth dental age and 4 role in maxillary canine impaction 118, 122–3, 125 perforation, deciduous molars 238–40 periapical abscesses, maxillary canines 129 periapical radiographs 11, 13, 20 computerized tomography vs 23–4, 25 maxillary central incisors 82, 83 parallax radiography 14–15 posterior mandibular area 18, 19 premaxillary 112 periodontal attachments, central maxillary incisor non-eruption 102–3 periodontal ligaments dentigerous cysts and 296 trauma 358 periodontal membrane, development 43 periodontal packs 7 periodontitis, maxillary canine impaction with 412, 413–15 periosteum, role in maxillary canine impaction 118

444  Index photography second opinions 356 at surgery 51 pigtails 50, 51–2, 59 cleidocranial dysplasia 384 cyst cases 310 for Johnson’s twin-wire arch 93 maxillary canines, palatal impaction Group 2 149 Group 3 156 ‘pink tooth’ 201 pins T-pins, for Johnson’s twin-wire arch 93 threaded 57 entry to pulp chamber 355 plate onlays 63 plates, maxillary central incisors and 87 active removable, adults 268 pockets, infra-bony 138, 204–6 positional diagnosis, see three-dimensional diagnosis post-treatment movement, in cleidocranial dysplasia 381 posterior mandibular area, radiography 18, 19 postero-anterior cephalograms 19–20 postoperative pain 48, 355 postponement of treatment, maxillary canine impaction 133 posts (threaded), dilaceration of maxillary central incisors 108 pre-dentine invasive cervical root resorption and 201 pre-eruptive invasive coronal resorption 206 pre-eruptive invasive coronal resorption 206, 207–10, 251 premature eruption 5 premolars 129 cleidocranial dysplasia 388–92 eruption, resorption of neighbouring roots 125 extraction 42, 136, 222, 224, 249 first affecting canines 322 see also canine–first premolar transposition roots first 322 impaction of maxillary canines 111 see also mandibular premolars; maxillary premolars pressure packs 32 pretorqued bracket techniques, maxillary canine impaction 136 prevention, maxillary canine impaction 127–32 primary failure of eruption 252–3, 256 primary intention, healing 48 primary retention 251 problem lists 133

prostheses cleidocranial dysplasia 373–4 lingual appliances with 286, 289 for maxillary central incisor impaction (adults) 267–9, 270 treatment of transpositions 273 see also dentures psychological aspects 7, 8, 86, 133 adults 267 cleidocranial dysplasia 380 cyst surgery 32, 297 see also compliance pulp chamber entry of threaded pin 355 root resorption and 189–96 trauma 366 pumicing of teeth, for attachment bonding 36–7 purpose-designed appliances, maxillary central incisors and 87 quality of image, computerized tomography 22t quality of life, after surgical exposure 45–8 radiation dosage ALARA principle 27 computerized tomography 21, 22t, 23–6 explaining to patient 26 radical exposure 40 radicular cysts 296–7, 298 deciduous maxillary canines 124 trauma 304–16 radiography 10–28, 327–8 at 3 years of age 84 canine–lateral incisor transpositions 163 canines 322 mandibular 218 maxillary 127 buccally-displaced 213–16 treatment monitoring 139 maxillary central incisors, 82–3 dilaceration 19, 74, 83 new bone formation 104 maxillary second premolar impaction 230 previous films 327 qualitative 11–14 root resorption 175, 176 invasive cervical 197, 200, 202–4 second opinions 355 three-dimensional diagnosis 14–27, 327–8, 330, 331 see also periapical radiographs ramus of mandible, third molar in 240, 241–2, 327 rapid maxillary expanders 130–2 rare earth magnets 64–9 reconstruction, computerized tomography 22 records, dental, incidental findings 26 rectangular wires, for mandibular second molar impaction 243–4

reduction, trauma 358–69 relapse, maxillary canines, palatal impaction, Group 4 162 relocation of teeth, cleidocranial dysplasia 376 Rely-a-Bond™ 50 removable appliances active removable plate for maxillary central incisor impaction (adults) 268 adults 270–1 maxillary canines, palatal impaction, Group 2 151 maxillary first molar impaction 238, 239 maxillary second premolar impaction 234, 235–6 trauma 360, 361 see also temporary anchorage devices replacement resorption 124 trauma 360 see also ankylosis repositioning of teeth, cleidocranial dysplasia 376 resorption bone, due to surgery 44 crowns 43, 246–50 deciduous maxillary canines 124 pre-eruptive invasive 206, 207–10, 251 see also roots, resorption restoration maxillary central incisors, crown dilaceration 106 pre-eruptive invasive coronal resorption 206 root resorption 189 invasive cervical 204 retention deciduous teeth 2, 3, 4–5, 251 see also over-retention retention of result of treatment, cleidocranial dysplasia 381, 393 retention periods, elastic rings, maxillary first molar impaction 238 right angles, radiographs at 17–21 maxillary canines 18, 19, 127 Right-On™ (bonding agent) 50 rinsing 50 roots cyst cases 316 dehiscence, CPm1 transposition 167 development 2, 42–3 arrested 78, 79–80 hard tissue obstruction 32–3 maxillary central incisors dilaceration 106–7 length on outcome 100–4 mesial/distal length differential, mandibular second molar impaction 240 movement 327–30, 332 non-resorption, deciduous maxillary canines 115

Index  445  premolars first 322 impaction of maxillary canines 111 resorption 45, 173–210, 340–7, 348–50 anatomy 179 incisors 340 anomalies and 177 computerized tomography 21, 22 maxillary canine impaction 124–5, 132–3, 134, 135, 169–70 invasive cervical 197–206, 324–5, 326 mandibular second premolar impaction 223 maxillary canine impaction 138–9, 169–70 prevalence 175–7 trauma 358, 360 treatment 177–87 surface damage 44 torque, see torque, on roots see also palatal root displacement rotations correction 135 maxillary canines, palatal impaction Group 1 140–2 Group 2 148, 154 ‘round-tripping’ canines 143 lingual appliances and 286 rubber bands, to mandibular removable appliance 151 RUNX2 gene 371, 382 sacs, see dental follicles saline, rinsing 50 ‘scorpion’ appearance, dilaceration of maxillary central incisors 83 screws mini-screws, lingual appliances with 2 87 temporary anchorage devices 62–3 second intention, healing 36 second molars cleidocranial dysplasia 392 deciduous 234, 235–8 mandibular 240–9 failed treatment 320 pressure packs 32 maxillary 249 second opinions 355–6 secondary retention 251 self-supported arch, for traumatic intrusion 363, 364–6 separators, maxillary first molar impaction 238 sexual dimorphism, see gender differences shoulders, cleidocranial dysplasia 371, 372 size, see small teeth; tooth size skeletal anchorage, traction for infraocclusion 260

skull, cleidocranial dysplasia 371, 372 ‘slingshot’ elastic ties 60 small teeth 322 cleidocranial dysplasia 373 maxillary canine impaction and 121, 122–3 smile line, treated cleidocranial dysplasia 381 soft tissues cleidocranial dysplasia 378 contact with enamel cuticle 43 devitalized maxillary canine on 117 effect of brackets 58 resistance 62, 351, 354 management 30, 31 maxillary canine impaction treatment 152, 159 trauma 73, 104 soldered palatal arch Johnson’s twin-wire arch 88, 92 for maxillary central incisor impaction (adults) 268–9 soldered springs, maxillary first molar impaction 238 space closure, root resorption and 178 space-holding devices, for mandibular second premolar impaction 223 space loss local 6, 7, 7, 32 second premolar impaction mandibular 222 maxillary 225–30 see also crowding space maintenance adults 272–3 maxillary central incisors 107 space opening 321 cleidocranial dysplasia 380 infra-occlusion 254 maxillary canine impaction prevention 130 treatment 133, 134–6, 138 maxillary central incisor impaction (adults) 264, 265–7 for root resorption 178 Spider Screw*.110 implant 290 splinting cleidocranial dysplasia 397, 398 trauma 358, 360 spontaneous eruption 56 in cleidocranial dysplasia 376 spontaneous resolution impaction from cysts 299, 300–16 traumatic intrusion 358 spoon denture (‘flipper’ partial denture) 263, 268 springs 61, 351 cleidocranial dysplasia 387–8, 392 for Johnson’s twin-wire arch 92, 93 lingual appliances and 285–6, 289 mandibular second molar impaction 243, 244

maxillary canine impaction palatal, Group 2 149 treatment 136 maxillary first molar impaction 238 space maintenance, adults 273 for temporary anchorage devices 62 see also ballista springs stainless steel wires Johnson’s twin-wire arch 88, 92 see also ligature wires standardization, radiographs at right angles 17–18 steel tubing, with elastic ties 60 see also ligature wires; stainless steel wires ‘straight-wire’ brackets 58 suction 50 super-elastic wires 61 lingual appliances and 286 maxillary canines, palatal impaction, Group 1 143 supernumerary teeth 8, 72 central 84 cleidocranial dysplasia 371, 374, 392, 393, 396 recurrent 397 dilaceration of maxillary central incisors 74–5 impaction of maxillary canines 111 maxillary central incisors 407–12 periapical radiographs 11, 13 radiography 82 results of removal 86 on tooth eruption 6, 8, 89 supplemental molars, cleidocranial dysplasia 393 surgeons 30, 49 attachment bonding by 36, 40 cooperation with orthodontists 48–52 three-dimensional diagnosis and 20 views on mesiodens 84 surgical exposure 29–54, 50 alone 30 cleidocranial dysplasia 45, 376–9, 384, 388, 396 cysts 297–9 duration of procedures 37–8 effect on outcomes 43–4 invasive cervical root resorption and 204 for mandibular second premolar impaction 224 maxillary canines 134 alone 30, 31 buccal approach 42 palatal impaction (Group 3) 154–5 buccally-displaced 216, 217 misdiagnosis 330, 331, 332–5, 336, 337 discomfort after 48 Kokich technique 44 and packing 32

446  Index surgical exposure, maxillary canines, cont’d palatal impaction Group 2 143–8 Group 4 162 Group 5 164 maxillary central incisors, on outcome 102 methods 33–40 outcomes 38–40 packing with 30–2 quality of life after 45–8 root resorption 179–80, 186 traumatic intrusion 359 T-pins, for Johnson’s twin-wire arch 93 tangential radiographs 18, 20 dilaceration of maxillary central incisors 74 temporary anchorage devices 62–4 mandibular second molar impaction 245 maxillary canines, palatal impaction, Group 4 162 see also removable appliances temporary dentures 105 third molars anomalies 249 extraction 43, 249 maxillary 249, 250 uses 273–6, 277 in vertical ramus 241, 242, 327 see also mandibular molars, third threaded pins 57 entry to pulp chamber 355 threaded posts, dilaceration of maxillary central incisors 107 three-dimensional diagnosis 14–27, 321 incorrect 327–30, 331 root resorption and 340, 341, 342 time factor, see duration of treatment timing of surgery 8 timing of treatment maxillary canines 127–33 maxillary central incisors 83–5, 86 Tip-Edge*.110 Plus™ technique, maxillary canine impaction 136 tipping, invasive cervical root resorption and 202 titanium-molybdenum alloy springs, lingual appliances with 289 TMJ radiograph series, radiation dosage 26t tooth buds ectopic 72–3 dilaceration of maxillary central incisors 75 trauma 420–30

tooth size 322 buccally-displaced maxillary canines 212 cleidocranial dysplasia 373 see also small teeth Toronto–Melbourne approach, cleidocranial dysplasia 376–7, 396 torque lingual appliances and 286 on roots cyst cases 310 maxillary canine impaction, treatment 143 maxillary central incisors 102, 104 traction after luxation 252 apical repositioning of flaps and 62 closed eruption technique 34 direction 51 central maxillary incisor non-eruption 102 elastic ties 60 follicle opening for 43 infra-occlusion 33 implants for 253, 256, 257–9 initiation 38 lingual appliances and 285 maxillary canine impaction 134 maxillary central incisors 104 root resorption and 180–7 see also intermaxillary traction trans-septal fibres, infra-occlusion of deciduous teeth 234 Transbond™ 273 transmigrated buccally-displaced mandibular canines 220–2 transpalatal arch, traction of canines 180 transpalatal bars, maxillary central incisor impaction (adults) 267, 270 transplantation of teeth, cleidocranial dysplasia 376 transpositions adults 273 buccally-displaced mandibular canines 220–2 maxillary canines, palatal impaction (Group 5) as 162 see also canine–first premolar transposition; canine–lateral incisor transpositions trauma 357–69 anterior maxilla 72, 73–8, 100–1, 105–8 Jerusalem hypothesis 77 intrusion 78–80, 358–69 maxillary canine impaction 115–16 radicular cysts 304–16 root canal treatment and 189

tooth buds 420–30 undiagnosed 365–6 true occlusal radiographs, maxillary arch 12–13 tube-shift method, see parallax radiography tubing elastic ties with 60 for Johnson’s twin-wire arch 92, 93 see also buccal tubes tumours 8, 32 tunnel variation, closed eruption technique (Crescini’s technique) 34–5, 45, 155–6 tweezers, to hold brackets 49, 51 twin-wire arch, see Johnson’s twin-wire arch 2 × 4 appliance 87 ‘ugly duckling’ 114, 125 unopposed tooth, adults 273–6, 277 vertex occlusal radiographs, maxillary arch 12–13 vertical box elastics, maxillary central incisors 105 vertical parallax radiography 15 vertical ramus, third molar in 241, 241–2, 327 vitality of pulp root resorption and 189–96 see also devitalization ‘wait and see’ approach buccally-displaced maxillary canines 216 cleidocranial dysplasia 373 root resorption 179, 188, 189 ‘wait-and-see’ periods 56 water, rinsing 50 window technique buccal side 42 exposure 33–4 wire frames bonded, trauma 362–3 wires rectangular, for mandibular second molar impaction 243–4 splinting for trauma 360 unopposed tooth, adults 273, 277 see also archwires; ligature wires; nickel-titanium wires zygomatic plate TAD 63, 64, 420 adults 281 maxillary central incisor impaction, adults 267