Contemporary Restoration of Endodontically Treated Teeth: Evidence-Based Diagnosis and Treatment Planning [Hardcover ed.] 086715571X, 9780867155716

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Contemporary Restoration of Endodontically Treated Teeth Evidence-Based Diagnosis and Treatment Planning

Dedication I dedicate this book to my beautiful wife and love of my life, Roula, for her constant encouragement and never-ending support; to my kids, Rhéa and Ziad, for the many hours that I spent away from them working on this book; and to my father and mother, who provided me with a fine education and gave me the strength to achieve what I wanted and made me the person I am.

Library of Congress Cataloging-in-Publication Data Contemporary restoration of endodontically treated teeth : evidence-based diagnosis and treatment planning / [edited by] Nadim Z. Baba. p. ; cm. Includes bibliographical references. ISBN 978-0-86715-571-6 eBook ISBN 978-0-86715-600-3 I. Baba, Nadim Z. [DNLM: 1. Evidence-Based Dentistry--methods. 2. Root Canal Therapy. 3. Crowns. 4. Tooth Replantation. WU 230] LC Classification not assigned 617.6’342059--dc23 2012030471 5 4 3 2 1

© 2013 Quintessence Publishing Co Inc

Quintessence Publishing Co Inc 4350 Chandler Drive Hanover Park, IL 60133 www.quintpub.com All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Editor: Leah Huffman Design: Ted Pereda Production: Sue Robinson

Foreword Preface Contributors

Part I: Treatment Planning for Endodontically Treated Teeth

1 Impact of Outcomes Data on Diagnosis and Treatment Planning Charles J. Goodacre and W. Patrick Naylor

2

Treatment Planning Considerations for Endodontically Treated Teeth Robert A. Handysides and Leif K. Bakland

3 Treatment Options and Materials for Endodontically Treated Teeth Nadim Z. Baba and Charles J. Goodacre

Part II: Methods of Restoration for Endodontically Treated Teeth

4 Principles for Restoration of Endodontically Treated Teeth Nadim Z. Baba, Charles J. Goodacre, and Fahad A. Al-Harbi

5 Cementation of Posts and Provisional Restoration Faysal G. Succaria and Steven M. Morgano

6

Tooth Whitening and Management of Discolored Endodontically Treated Teeth Yiming Li

Part III: Management of Severely Damaged Endodontically Treated Teeth

7 Crown Lengthening Nikola Angelov

8 Preprosthetic Orthodontic Tooth Eruption Joseph G. Ghafari

9 Intra-alveolar Transplantation

Antoanela Garbacea, Nadim Z. Baba, and Jaime L. Lozada

10 Autotransplantation and Replantation Leif K. Bakland and Mitsuhiro Tsukiboshi

11 Osseointegrated Dental Implants

Juan Mesquida, Aladdin J. Al-Ardah, Hugo Campos Leitão, Jaime L. Lozada, and Aina Mesquida

Part IV: Treatment of Complications and Failures

12 Repair of Perforations in Endodontically Treated Teeth

George Bogen, C. John Munce, and Nicholas Chandler

13 Removal of Posts

Ronald Forde, Nadim Z. Baba, and Balsam Jekki

14 Removal of Broken Instruments from the Root Canal System David E. Jaramillo

15 Endodontic Treatment of a Tooth with a Prosthetic Crown Mathew T. Kattadiyil

16 Retrofitting a Post to an Existing Crown Nadim Z. Baba, Tony Daher, and Rami Jekki

It is an honor to have been invited to write the foreword for Dr Nadim Baba’s text on the restoration of endodontically treated teeth. The last book on this topic, published by Quintessence, was authored by Shillingburg and Kessler in 1982. Three decades later, this new book is much needed and long overdue. Dr Baba’s interest in the restoration of pulpless teeth dates back to his graduateschool days. I served as his program director and his principal research advisor during his studies at Boston University in the postdoctoral prosthodontic program, where the title of his master’s project and thesis was “The Effect of Eugenol and Non-eugenol Endodontic Sealers on the Retention of Three Prefabricated Posts Cemented with a Resin Composite Cement.” Dr Baba certainly has come a long way since receiving his certificate of advanced graduate study and master of science in dentistry degree in 1999. He is now a Diplomate of the American Board of Prosthodontics and a full professor at Loma Linda University School of Dentistry, and he is about to publish this comprehensive book on the restoration of endodontically treated teeth. This new text has a wealth of evidence-based information on all facets of restoration of endodontically treated teeth and will serve as an indispensable reference not only for dentists involved in the restoration of pulpless teeth, such as general practitioners and prosthodontists, but also for dentists who do not place restorations but are engaged in planning treatment for structurally compromised teeth, such as endodontists, periodontists, and oral surgeons. With the welldocumented success of osseointegrated implant-supported fixed restorations, combined with a better understanding of the factors that can influence the prognosis of severely broken down teeth, the profession’s approach to planning treatment for these teeth has evolved, and this text offers a well-balanced, contemporary approach

to the topic of treatment planning. Dentists encountering treatment planning dilemmas, such as determining when to extract a compromised tooth and when to retain it and restore it, can find the answers to most of their questions in this first-rate text. Traditional principles and techniques are reviewed and reinforced, along with modern materials and methods, all with a firm foundation in the best available scientific evidence and with an emphasis on clinical studies. Many of the chapters provide comprehensive, step-by-step descriptions of technical procedures with accompanying illustrations to guide the reader through all aspects of restoring pulpless teeth, including fabrication of various foundation restorations, cementation techniques, and methods of provisionalization of endodontically treated teeth. Preprosthetic adjunctive procedures, such as surgical crown lengthening, repair of perforations, and orthodontic measures, are also described and illustrated. Dr Baba has assembled a group of renowned experts on various topics related to the restoration of pulpless teeth, and these experts have collectively produced this outstanding text, which will remain a definitive reference for years to come. The profession as a whole is very fortunate to have this text. Many thanks must go to Dr Baba for undertaking this monumental task and to all contributing authors for their time and efforts in helping Dr Baba produce this new book on such a very important subject. Steven M. Morgano, DMD Professor of Restorative Sciences and Biomaterials Director, Division of Postdoctoral Prosthodontics Boston University Henry M. Goldman School of Dental Medicine Boston, Massachusetts

My interest in the restoration of endodontically treated teeth dates back to my graduate-school days at Boston University. When working on my master’s project and thesis and later while studying for the American Board of Prosthodontics exam, I realized that very few books dealt with the restoration of pulpless teeth. The first book on that topic was published by Quintessence in 1982; two decades later, three books were published but all were somewhat limited in their scope. They dealt mainly with fiber posts, their characteristics, and their clinical applications. This book is primarily intended to be a manuscript that reviews the basic principles of diagnosis and treatment planning and describes numerous treatment options and the techniques recommended for contemporary treatment of endodontically treated teeth. The purpose of this book is to provide general dentists, endodontists, prosthodontists, and dental students (postgraduate and predoctoral) with a comprehensive review of the literature and evidence-based information for the treatment of endodontically treated teeth, keeping in mind the integration of systematic assessments of clinically relevant scientific evidence. Four major themes are discussed. The first part focuses on treatment planning, treatment options, and materials used for the restoration of endodontically treated teeth. The second part reviews the principles and methods of restoration along with cementation, provisional restoration, and management of discolored endodontically treated teeth. The third part describes the different aspects of the management of severely damaged pulpless teeth. In the final part, treatment of complications and failures is reported.

Acknowledgments

I wish to express my appreciation and indebtedness to all my friends and colleagues who contributed chapters, sections of chapters, or clinical cases in specific areas in which they are experts. Without them the book would not have been possible. I would like to take the opportunity to thank Leif Bakland, Zouheir Salamoun, W. Patrick Naylor, and the dean of my school, Loma Linda University, Charles J. Goodacre, for their counsel and help during the preparation of the manuscript. Most importantly, I extend my special thanks to Ms Lisa Bywaters and the staff of Quintessence Publishing for their professionalism and guidance in bringing my book to life. I also would like to acknowledge my teachers and mentors who had a great impact on my visions, attitude, and career: Pierre Boudrias, Hideo Yamamoto, Steven M. Morgano, David Baraban (deceased), and Charles J. Goodacre. They remind me of the Lebanese-American poet and writer Gibran Khalil Gibran, who said: “The teacher who is indeed wise does not bid you to enter the house of his wisdom but rather leads you to the threshold of your mind.” I feel blessed, lucky, and proud to have had the chance to know and work with each one of these people in various stages of my professional career.

Aladdin J. Al-Ardah, DDS, MS Assistant Professor Advanced Education Program in Implant Dentistry Loma Linda University School of Dentistry Loma Linda, California

Fahad A. Al-Harbi, BDS, MSD, DScD Dean and Assistant Professor College of Dentistry University of Dammam Dammam, Saudi Arabia

Nikola Angelov, DDS, MS, PhD Professor and Director Predoctoral Program in Periodontics Loma Linda University School of Dentistry Loma Linda, California

Nadim Z. Baba, DMD, MSD Professor of Restorative Dentistry Director Hugh Love Center for Research and Education in Technology Loma Linda University School of Dentistry Loma Linda, California

Leif K. Bakland, DDS Ronald E. Buell Professor of Endodontics Loma Linda University School of Dentistry Loma Linda, California

George Bogen, DDS Private practice limited to endodontics Los Angeles, California

Nicholas Chandler, BDS, MSc, PhD Associate Professor of Endodontics University of Otago School of Dentistry Dundin, New Zealand

Tony Daher, DDS, MSEd Associate Professor of Restorative Dentistry Loma Linda University School of Dentistry Loma Linda, California Lecturer University of California at Los Angeles Los Angeles, California

Ronald Forde, DDS, MS Chair and Assistant Professor of Restorative Dentistry Loma Linda University School of Dentistry Loma Linda, California

Antoanela Garbacea, DDS Private practice Santa Rosa, California

Joseph G. Ghafari, DMD Head and Professor Division of Orthodontics and Dentofacial Orthopedics Department of Otolaryngology, Head and Neck Surgery American University of Beirut Medical Center Beirut, Lebanon

Professor of Orthodontics Lebanese University School of Dentistry Beirut, Lebanon Adjunct Professor of Orthodontics New York University College of Dentistry New York, New York

Charles J. Goodacre, DDS, MSD Dean and Professor of Restorative Dentistry Loma Linda University School of Dentistry Loma Linda, California

Robert A. Handysides, DDS Chair and Associate Professor of Endodontics Loma Linda University School of Dentistry Loma Linda, California

David E. Jaramillo, DDS Clinic Director and Associate Professor of Endodontics Loma Linda University School of Dentistry Loma Linda, California

Balsam F. Jekki, BDS Assistant Professor of Restorative Dentistry Loma Linda University School of Dentistry Loma Linda, California

Rami Jekki, DDS Assistant Professor of Restorative Dentistry Loma Linda University School of Dentistry Loma Linda, California

Mathew T. Kattadiyil, DDS, MDS, MS Associate Professor of Restorative Dentistry Director Advanced Specialty Education Program in Prosthodontics Loma Linda University School of Dentistry

Loma Linda, California

Hugo Campos Leitão, DMD, MSD Assistant Professor in Periodontics Universitat Internacional de Catalunya Barcelona, Spain

Yiming Li, DDS, MSD, PhD Professor of Restorative Dentistry Director Center for Dental Research Loma Linda University School of Dentistry Loma Linda, California

Jaime L. Lozada, DMD Professor and Director Advanced Education Program in Implant Dentistry Loma Linda University School of Dentistry Loma Linda, California

Aina Mesquida, DDS Resident Advanced Education Program in Implant Dentistry Loma Linda University School of Dentistry Loma Linda, California

Juan Mesquida, DDS Assistant Professor Advanced Education Program in Implant Dentistry Loma Linda University School of Dentistry Loma Linda, California

Steven M. Morgano, DMD Professor of Restorative Sciences and Biomaterials Director Division of Postdoctoral Prosthodontics Boston University Henry M. Goldman School of Dental Medicine Boston, Massachusetts

C. John Munce, DDS Assistant Professor of Endodontics Loma Linda University School of Dentistry Loma Linda, California Assistant Professor of Endodontics University of Southern California Ostrow School of Dentistry Los Angeles, California

W. Patrick Naylor, DDS, MPH, MS Associate Dean Advanced Dental Education Professor of Restorative Dentistry Loma Linda University School of Dentistry Loma Linda, California

Faysal G. Succaria, DDS, MSD Chair and Assistant Professor Department of Prosthodontics Boston University Institute for Dental Research and Education Dubai, United Arab Emirates

Mitsuhiro Tsukiboshi, DDS, PhD Chairman Tsukiboshi Dental Clinic Amagun, Aichi Japan

Impact of Outcomes Data on Diagnosis and Treatment Planning The purpose of diagnosis and treatment planning is to devise the longest-lasting and most cost-effective treatment that not only addresses patients’ chief complaints but meets or exceeds their expectations. Treatment recommendations are then based on practitioners’ individual knowledge, and their individual professional experiences serve as expanded frames of reference. Such an approach to diagnosis and treatment planning often proves successful because data from clinical or laboratory research frequently can point to one approach as “the best treatment” or a “best practice.” That said, other aspects in the clinical decision-making process can be drawn from the dental literature to render “evidence-based” recommended treatment modalities. When available, published reports based on randomized controlled trials are considered to provide the highest level of evidential rigor, 1 allowing their results and conclusions to guide clinical treatment decision making. Unfortunately, studies with this level of science are not only complex but also costly, and they are not always available for many aspects of dentistry. Yet outcomes derived from longer-term clinical studies, such as those of 5 years’ or more duration and completed by different investigators, do provide another rich resource to guide clinical decision making. Even the results of peer-reviewed laboratory studies offer valuable information such as potential clinical trends when actual clinical findings are not otherwise available. Therefore, it is recommended that outcomes data (the results of various scientific investigations) be used whenever possible so clinical diagnosis and treatment

planning are evidence-based processes. This recommendation certainly holds true in the management of teeth that have received root canal treatment. This chapter is intended to present reviews of published clinical and laboratory research, provide an interpretation of those research results, and then offer clinical guidelines to aid development of the best possible treatment plan for endodontically treated teeth (ETT). Varying levels of clinical and laboratory data are available in support of clinical guidelines. Therefore, a number of these key variables will be presented and discussed in this chapter to aid clinicians in arriving at the best treatment plan for each endodontic situation.

Tooth Fracture and Survival For decades, practitioners have recognized a difference between vital teeth and ETT. In fact, more than half a century ago, Healey wrote that, “the remaining coronal portion of the treated pulpless tooth quite apparently is more brittle or fragile than when it contained a vital pulp.”2 Healey’s perception was accompanied by another observation. ETT have a greater tendency to fracture during extraction and, therefore, are more likely to be removed in pieces than as intact teeth.2 Another clinical perception about ETT is that they do not have the same longevity as vital teeth. Case in point, fixed partial dentures are more likely to fail if the abutment teeth are nonvital.3–7 Moreover, when posterior ETT are not restored with a crown, they have been found to fracture more often than vital teeth.8 These perceptions have emerged from reports based on both clinical and laboratory research and now are sufficiently well recognized to guide clinical decisions.

Tooth fracture A 1999 study by Chan et al 9 involving 315 teeth with vertical root fractures over a 13-year period determined that 60% of those fractures occurred in ETT while 40% occurred in vital teeth. Furthermore, the incidence of fracture in both nonvital teeth and vital teeth was 1.4 times higher in male than in female patients. Vertical fractures occurred more frequently in first molars for both vital and nonvital teeth. Among ETT, the fracture rate of mandibular first molars was more than twice that of maxillary first molars, maxillary second molars, and maxillary first and second premolars. In molars that received endodontic treatment, the roots most likely to fracture were the mesiobuccal roots of maxillary molars and the mesial roots of mandibular molars.9 Interestingly, nonvital canines were the teeth least

susceptible to fracture. A subsequent survey of cusp fractures in general dental practices found that teeth with a history of endodontic treatment were susceptible to subgingival fracture in unfavorable locations.10

Tooth survival Clinical evidence also is available to support the perception that ETT have a lower survival rate than their vital counterparts. According to a 1992 Swedish study assessing the reasons for tooth extraction among 200 patients, ETT were lost more often than vital teeth.11 A subsequent retrospective study of 202 nonvital teeth by Caplan et al 12 compared the survival of ETT with their contralateral counterparts after a median time of 6.7 years. Of the 202 matched pairs, 16% were anterior teeth, 41% were premolars, and 44% were molars. For all types of teeth, those that were endodontically treated were three times more likely to be extracted then their vital, contralateral counterparts. Of particular note, molars that received endodontic therapy were seven times more likely to be extracted than endodontically treated premolars and anterior teeth.12

Presence or absence of proximal contact The survival of ETT has even been correlated to the presence or absence of proximal contact. Analysis of data from multiple studies determined that ETT with two proximal contacts had significantly longer survival rates than teeth with one or no proximal contacts.8, 13 In a review of charts, radiographs, and computer databases of 400 teeth from 280 patients, it was determined that ETT with two proximal contacts had substantially better survival than teeth with fewer than two proximal contacts.13 A meta-analysis of 14 clinical studies also identified ETT with both mesial and distal proximal contacts as having an increased rate of survival.14 In addition, a 4year, cumulative tooth survival analysis of 759 teeth with primary root canal treatment and 858 teeth with secondary root canal treatment (retreatment) determined that teeth with two proximal contacts had a 50% lower risk of being lost than teeth with one or no proximal contact. Terminal teeth in the arch were associated with almost a 96% higher risk of loss than teeth that were not the distalmost tooth in the arch.15 Furthermore, second molars had an appreciably poorer 10-year survival rate than all other types of teeth.8

Fixed partial denture survival rates As mentioned previously, multiple clinical studies, some dating back more than a quarter of a century, have shown that fixed partial dentures fail more often when supported by endodontically treated abutment teeth than when they are supported by vital abutment teeth.3–7 One clinical study compared single crowns and fixed partial dentures over a 16- to 20-year period. It was reported that the long-term survival rates of three-unit fixed partial dentures on vital teeth were comparable to those of fixed partial dentures with at least one endodontically treated retainer. However, fixed partial dentures with more than three units and those with cantilevered units had significantly more failures.16

Restoration Selection for Pulpless Posterior Teeth There is a substantial body of evidence to indicate that endodontically treated posterior teeth are likely to fracture unless they are restored with a completecoverage crown. In some instances, the resulting fractures are so significant as to result in tooth loss. According to a 20-year, retrospective study of 1,639 posterior teeth restored with amalgam but without cuspal coverage, maxillary premolars (with mesio-occlusodistal [MOD] amalgam restorations) had the highest fracture rates. In fact, 28% of the maxillary premolars fractured within 3 years of endodontic therapy, 57% fractured after 10 years, and 73% fractured after 20 years, in the absence of some type of complete crown.17

Tooth fracture rates Of all the teeth that fractured in the 20-year study cited above,17 4% experienced catastrophic vertical fractures. Within that 4% of fractured teeth, the maxillary second molars accounted for 34.5% (10 of 29 fractures) of the teeth requiring extraction. In another study involving 220 molars followed for as few as 6 months and as long as 10 years, there were a total of 101 failures due to caries, cracks in the tooth or the restoration, loss of the restoration, or root fracture. Of these 101 teeth, 14 (13.9%) were judged to be nonrestorable. However, teeth with maximal tooth structure, mirroring that of a Class I restoration with at least 2.0 mm of surrounding axial wall thickness, had the highest 5-year survival rate (78%).18 An even larger study of 837 endodontically treated posterior teeth, with and without coronal-coverage restorations, reported a significant increase in clinical

longevity when cuspal-coverage crowns were provided on maxillary and mandibular premolars and molars. The maxillary premolars experienced only a 6% failure rate when crowns were present, while the failure rate for premolars that did not receive a cuspal-coverage cast restoration was 44%. Similarly, maxillary molars restored with crowns had a 2% failure rate, while molars that were not restored with a crown had a 50% failure rate. Similar outcomes were noted in mandibular premolars. One study reported a 6% failure rate when crowns were present but a 38% failure rate for ETT without crowns. For mandibular molars, the failure rate was only 3% for ETT with crowns but 42% for ETT without crowns.19

Large-scale data analysis When examining the results of initial endodontic treatment in 1,462,936 teeth, researchers found that 97% of teeth were retained in the oral cavity 8 years after the initial nonsurgical endodontic treatment.20 Although the percentage of tooth loss was small, 41,973 teeth were actually extracted during this observation period, of which 85%, or 35,697 teeth, did not have complete-coverage crowns. There was a statistically significant difference (P < .001) between teeth with crowns and those without crowns for all types of teeth. In fact, the number of nonvital premolars without crowns that required extraction was 5.8 times higher than that of premolars restored with crowns. In the case of nonvital molars, the number of teeth without crowns that required extraction was 6.2 times higher than the number extracted when molars were protected by complete crowns.20 An analysis of data from multiple studies has demonstrated that ETT without crowns were lost at six times the rate of teeth with crowns.7 In a systematic review of single crowns on endodontically treated teeth, the 10-year survival of teeth with crowns was 81%, whereas the 10-year survival of ETT restored with a direct restoration (composite resin, amalgam, or cement) was 63%.21 A meta-analysis involving 14 clinical studies determined that crown placement on ETT increased tooth survival.9 The results of a recent 4-year cumulative tooth survival analysis, after primary and secondary root canal treatments, indicated a reduction in tooth loss by approximately 60% when ETT were restored with a cast restoration.10 Maxillary premolars and mandibular molars had the highest frequency of extraction due to tooth fracture.10

Time until failure

The time interval until failure and tooth loss also has been assessed for ETT with and without complete crowns. Those teeth without crowns failed after an average period of 50 months while pulpless teeth restored with a complete crown were lost after an average of 87 months following placement of a complete cast restoration.22 In contrast, a shorter, 3-year investigation found comparable success rates between endodontically treated premolars restored with only a post and direct Class II composite resin restoration and premolars restored with complete-coverage crowns.23 Similarly, a retrospective cohort study18 indicated that endodontically treated molars, intact except for the endodontic access opening, were successfully restored using composite resin restorations. Interestingly, composite resin restorations had better clinical performance than dental amalgam restorations. The 2-year probability of survival of molars restored with composite resin restorations was 90% versus 77% for amalgam restorations. At the 5-year point, the survival probability declined markedly for both restorative materials, to 38% for composite resin and 17% for dental amalgam restorations.18 Interestingly, clinical studies and other laboratory investigations mentioned previously reported positive results when composite resin restorations were used to restore ETT. In fact, these results support the use of composite resin rather than a cuspal-coverage crown when the tooth is intact except for the endodontic access opening or is minimally restored. Unfortunately, there are no long-term clinical data comparing the survival of pulpless posterior teeth with composite resin restorations to that of teeth restored with complete crowns that vary in terms of the amount of the remaining tooth structure. It would be helpful if there were studies comparing the survival rates of premolar and molar teeth restored without crowns with the following conditions: (1) intact except for a conservative endodontic access opening; (2) a Class I restoration and an access opening; (3) a small Class II restoration and an access opening; (4) a large Class II restoration; and (5) a large MOD restoration. Additionally, normal occlusal forces place substantial stresses on teeth. 24 These same stresses can cause vertical fractures in both nonvital and vital teeth.3 It also has been reported that parafunctional habits produce higher failure rates for fiber posts restored with composite resin.25 Therefore, the effects of heavier-than-normal occlusal forces, as well as parafunctional habits, on ETT restored without crowns should be examined more extensively to determine their impact on tooth survivability.

Complex amalgam restorations versus complete crowns

Aside from complete crowns, complex amalgam restorations also have been used to restore both vital and nonvital teeth. In these cases, an evaluation of the remaining tooth structure should be made to determine whether to replace or cover (“cap”) weakened cusps with dental amalgam restorative material. In one randomized, controlled clinical trial, vital teeth were carefully evaluated for cusp strength. Weak cusps were reduced, and an 88% survival rate was reported for the 268 teeth receiving extensive amalgam restorations after a 100-month period. Forty of the 268 restorations (14.9%) required some form of clinical treatment during the study to secure or increase their clinical lifetime, resulting in a 72% survival rate.26 A retrospective study of 128 vital teeth with complex amalgam restorations, described by the authors as posterior restorations replacing one or more cusps, included a time-life survival analysis. In that report, the percentage of restorations surviving for 10 years was 54%, but that amount declined to 36% after 15 years and only 19% after 20 years.27 In another study of 124 cusp-covered Class II amalgam restorations, the cumulative survival rate was 72% after 15 years.28 When amalgam restorations were placed in nonvital teeth, positive results also were reported in both laboratory and clinical studies, provided that a sufficient thickness of amalgam covered the cusps. In one laboratory study, 48 teeth were restored with mesio-occlusal (MO) restorations with a 4.0-mm thickness protecting the buccal cusps and 3.0 mm of amalgam over the lingual cusps.29 When an angular load was applied to the restored cusps, the authors concluded that amalgam was a suitable material for cuspal restoration of pulpless teeth.29 In another laboratory study of 36 extracted, intact mandibular molars, endodontic access openings were placed in the teeth, and the root canals were instrumented as they would be clinically to initiate endodontic therapy. The teeth were then prepared and restored with either MO or MOD amalgam restorations, with and without cuspal coverage. Specimens receiving amalgam coverage of the entire occlusal surface, with at least 2.0 mm of the cuspal coverage, retained their cuspal stiffness.30 However, without cuspal coverage, teeth with conventional Class II MO and MOD amalgam restorations were not considered adequately protected.30 One clinical study of 100 pulpless teeth, restored with amalgam overlying the cusps, found that the amalgam restorations were successful after 3 years of service.31 The results of another investigation included a recommendation that all cusps adjacent to teeth with missing marginal ridges be covered (“capped”) with a sufficient thickness of amalgam.32

Restoration Selection for Pulpless Anterior Teeth

One of the most misunderstood and perhaps challenging clinical decisions has to do with how to manage anterior teeth following root canal therapy. There is a clinical perception that endodontically treated anterior teeth without crowns are less prone to fracture than posterior teeth.19 A study of 1,273 ETT conducted more than 25 years ago found that crowns significantly increased the survival rate for posterior teeth, but the same outcome was not valid for anterior teeth.19 In this study, the maxillary premolar success rate for ETT increased from 56.0% when no coronal coverage was provided to 93.9% with coronal coverage. Maxillary molars exhibited similar results with the success rate increasing from 50.0% (no crown) to 97.8% (with coronal coverage). For maxillary anterior teeth, the success rate was 85.4% with no crown and 87.5% with a crown. For mandibular anterior teeth, the success rate was 94.4% with no crown and 97.5% with a crown. From these results it was concluded that intact pulpless anterior teeth, except for a conservative endodontic access opening, do not require complete crowns. The authors of this chapter suggest that the results of this study make it reasonable to restore pulpless anterior teeth with composite resin when they are intact except for the access opening; when they are weakened by large and/or multiple restorations; and when they require significant color or form changes that cannot be managed by some type of more conservative treatment. Despite the findings of Sorenson and Martinoff,19 anterior teeth without crowns can indeed fail and require extraction, as was reported in the previously cited study of more than 1.4 million teeth.20 In that extensive investigation, 83% of the anterior teeth that were extracted had not received a crown, while 9.7% of the extracted teeth had crowns and posts and 7.3% of the extracted teeth had crowns but no posts.20 Thus, stronger evidence confirms that the longevity of endodontically treated anterior teeth is increased when they are restored with crowns, in contrast to the findings reported by Sorensen and Martinoff in 1984.19 Clinicians must carefully evaluate the amount of remaining coronal tooth structure in anterior teeth before deciding not to recommend complete coronal coverage. Additionally, as with posterior teeth, there are no tooth survival data comparing intact pulpless anterior teeth with similar teeth having small restorations and those with large restorations where substantial amounts of tooth structure are missing. Likewise, data regarding the impact of heavy occlusal forces are not available to guide treatment planning. Therefore, tooth conditions and structural integrity remain key factors when clinicians assess anterior ETT and propose the most appropriate treatment regimen.

Physical Properties and Characteristics of Pulpless Teeth

As to the question of whether or not ETT are as brittle as many perceive, numerous studies have compared different physical properties and characteristics of both vital and nonvital teeth. While some definitive differences have been identified, there also are some conflicting findings. In fact, not all the data conclusively support the presence of substantial differences between vital and nonvital teeth. Additionally, some of the outcomes have not been replicated in multiple studies by different investigators. Nevertheless, a comprehensive review of available evidence provides insight into what happens or may happen to teeth following endodontic therapy. Therefore, this particular question is best addressed by assessing various physical properties and characteristics of pulpless teeth.

Moisture content Conflicting information exists as to the moisture content in teeth before and after root canal therapy. One study of the dentin in dogs determined that pulpless teeth had 9% less moisture than comparable vital teeth.33 Yet in another investigation of 23 matched pairs of human ETT and their vital contralateral teeth, the moisture levels (12.3% in vital teeth and 12.1% in nonvital teeth) were not statistically significantly different.34 In some teeth that had undergone root canal therapy as many as 15 to 20 years earlier, the moisture content was not necessarily reduced, even after extended periods of time.34 It has even been stated that dehydration alone does not account for changes in physical properties of dentin.35

Flexibility At least two studies have shown that ETT have less flexibility (ability to bend and then return to their original shape) than corresponding vital teeth.36,37 Another study found a measurable decrease in tooth stiffness and proportional limit as a result of root canal treatment.35 Stiffness also has been assessed as it relates to the type of restoration placed in vital teeth and the corresponding impact on root canal treatment. For example, a one-surface occlusal preparation was found to produce a 20% decrease in stiffness while an MO preparation caused a 46% reduction. Tooth stiffness was reduced even further (a 63% reduction) following placement of an MOD preparation. However, according to one investigation, endodontic treatment alone decreased stiffness by only an additional 5%.38

Cuspal deflection

Cuspal deflection Aside from moisture level and stiffness changes, cuspal movement or, better yet, resistance to deflection is another important characteristic. The cuspal deflection (separation of the cusps) that occurs on maxillary first premolars has been measured by applying a load to a steel ball positioned in the occlusal fossa. One study found the separation of the facial and palatal cusps to be 1.0 μm for an intact, vital tooth. The actual amount of deflection increased dramatically in premolars when these teeth were prepared for restorations. In fact, cuspal deflection increased from 1.0 μm (baseline) to 16.0 μm when there was a Class I occlusal cavity preparation, to 20.0 μm for a minimal width MO cavity preparation, and to 24.0 μm for a minimal width MOD cavity preparation in teeth that had not undergone endodontic therapy. Following a pulpotomy, the amount of deflection rose to the highest level, 28.0 μm. 39 The authors concluded that breaking the continuity of the enamel layer reduces tooth rigidity, and teeth that have a wide isthmus, as in a Class II MOD cavity preparation, should have some form of cuspal protection.39 Another study of cuspal deflection determined that intact mandibular molars had cuspal deflections of up to 1.0 μm.40 While MO cavity preparations changed the deflection to less than 2.0 μm of movement, MOD cavity preparations produced 3.0 to 5.0 μm of movement. Endodontic access preparations produced 7.0 to 8.0 μm of movement in the MO group and 12.0 to 17.0 μm of movement in the MOD group (a twofold to threefold increase).40 A third study of cuspal movement in 10 maxillary premolars reported a mean deflection ranging from 3.0 to 12.0 μm in intact teeth. The amount of the mean deflection actually increased from 14.0 to 26.0 μm following root canal treatment, removal of the marginal ridges, and restoration with composite resin.41

Proprioception The ability of teeth to respond to stimuli, such as possessing a sense of being contacted by opposing teeth or other hard objects, is known as proprioception. One clinical study used a spring device to apply force to 155 normal teeth (incisors, canines, premolars, and molars) until patients indicated that they first felt the sensation of pressure.42 The proprioception threshold, or point at which a pressoreceptive response is initiated, was significantly higher (57%) in nonvital teeth than vital teeth.42 This threshold level also increased significantly from anterior to posterior teeth.42 Another clinical investigation, with three patients, involved crowns with buccal bars placed on vital teeth and their adjacent or contralateral endodontically treated

teeth.43 Weights and their corresponding loads were applied at different positions on the bars until the subjects experienced pain. Nonvital teeth had pain threshold levels that were more than twice as high as those of their contralateral or adjacent vital tooth.43 Conversely, a study of 29 patients compared the response of 59 vital teeth with that of 22 endodontically treated maxillary teeth when a pushing force was directed from the incisal edge parallel to the long axis of each tooth. The load was applied at an incremental speed of 1 N/s until the patient pushed a button to indicate touch was sensed. In this investigation, the authors did not find a significant difference between the tactile sensibilities of ETT and vital teeth.44

Classic physical properties Considerable variation exists among the classic physical property tests, such as hardness, load to fracture, toughness, and strength (compressive, shear, and tensile), used to compare outcomes for vital and nonvital teeth. This makes it challenging to draw definitive conclusions and comparisons for specific properties. For example, it has been reported that pulpless teeth have decreased dentin strength.45, 46 It also has been reported that dentin strength is not decreased following endodontic therapy. 47, 48 When vital and nonvital dentin hardness were measured, one group of researchers found comparable hardness values49 while another group noted a significant (3.5%) reduction in hardness.50 A study of shear strength and toughness determined that ETT exhibited significantly lower values than corresponding vital teeth for both these tests.46 A subsequent study by different investigators did not find differences in shear strength, toughness, or load to fracture between vital and nonvital dentin.50 Comparable compressive and tensile strengths also were recorded for vital and nonvital dentin.35

Guidelines for Restoration Selection Recommendations for the type of restoration to be placed following endodontic treatment differ for posterior and anterior teeth.

Restoration of posterior teeth Most endodontically treated posterior teeth should be restored with complete-

coverage crowns to enhance their longevity, particularly teeth previously restored with large MOD, MO, or disto-occlusal intracoronal restorations. Such teeth benefit from crowns that encompass the cusps to prevent fracture from the occlusal forces responsible for cuspal separation. However, posterior teeth that are intact or minimally restored with a conservative endodontic access opening and are not subjected to heavier-than-normal occlusal forces can be restored with composite resin restorations. Dental amalgam restorations may be placed in situations where the restorative material covers the cusps at a thickness of at least 2.0 mm.

Restoration of anterior teeth In many instances, the access opening in endodontically treated anterior teeth can be restored with a conservative composite resin restoration. According to Sorensen and Martinoff,19 complete-coverage crowns are not always necessary unless a tooth has been weakened or compromised by large or multiple restorations or its color or form cannot be effectively corrected with conservative treatment. As previously discussed, however, Salehrabi and Rotstein20 found that failure rates were lower in all types of teeth that received crowns than in those that did not. Studies of the physical properties of ETT have produced some differing results, but there are documented changes in some of the physical properties and characteristics of nonvital teeth that may make them more susceptible to fracture.

Outcomes Data for Posts Laboratory data A popular misconception is that posts strengthen ETT. However, research indicates otherwise. In fact, numerous studies have shown that, rather than strengthen teeth, posts and cores actually weaken extracted teeth (decrease their fracture resistance) or fail to increase their fracture resistance.51–56 Maxillary incisors without posts were found to resist higher loads than were other types of teeth with posts and crowns.57 Likewise, mandibular incisors with intact natural crowns exhibited greater resistance to transverse loads than ETT with either prefabricated posts or cast posts and cores.58 However, if a ferruled cast post and core was used, the likelihood of root fracture was reduced.58 A condition where a post and core may have a positive impact on a tooth was identified in a photoelastic stress analysis study. 59 That research indicated that posts

reduced dentin stress in situations where the root canal space was excessively enlarged and the dentin walls were thinned.59

Clinical data Clinical data also fail to support the perception that posts enhance the survival of teeth. While one investigation demonstrated that teeth with and without posts had the same longevity outcome,60 another clinical study determined that teeth with posts exhibited significantly more apical periodontitis than teeth without posts.61 Results from the latter study indicated that the preparation and placement of a post can actually compromise the apical endodontic seal. The previously cited examination of 1.4 million teeth with initial endodontic treatment found no significant difference between the extracted teeth with posts and those without posts.20

Guidelines for use of a post While there is no evidence to support the contention that posts promote tooth survival or strengthen the root of a tooth, there is evidence that posts actually can decrease the fracture resistance of ETT. 51–56 Consequently, clinicians should recognize that the main purpose of a post is to retain a coronal core that cannot otherwise be placed in tooth structure by some other means.

Clinical Complications of Post and Core Restorations A review of the literature for clinical post and core studies identified the two most common types of postoperative complications as post loosening and root fracture.62 Both of these negative outcomes were reported in more than 10 studies and were found to be the most common reasons for failure. Root perforation is a serious complication but was not reported in this literature review.62 Therefore, a literature search was completed to identify clinical studies with data related to the incidence of clinical root perforation. In 1984, Sorensen and Martinoff19 reviewed the patient treatment records and radiographs of nine general dentists. Among 420 posts, only three perforations (0.7%) were noted. 19 In another study, a review of radiographs for 327 ETT with posts, most of which were referred by general dentists for a variety of reasons, only 5 teeth (1.5%) with root perforations were identified.63 A third investigation involving a radiographic

analysis of 3,178 ETT determined that 1.1% of the teeth had perforations of either the root walls or the floor of the pulp chamber.64 Additional studies published between 2005 and 2010 were identified in which the endodontic treatment was provided by predoctoral dental students.65–68 A review of 388 teeth with 620 treated root canals in an undergraduate dental clinic found perforations in 17 root canals (2.7%).65 A second study involved the assessment of endodontic treatment performed by predoctoral dental students in single-rooted teeth; examination of 100 radiographs of obturated root canals found no evidence of root perforations.66 A third investigation involving 550 teeth treated by predoctoral students reported the incidence of root perforation to be 7.0%.67 A 2010 retrospective study from a university clinic reported a total of 116 root perforations in 5,048 ETT in 2,002 patients for an incidence rate of 2.3%.68 Over a 26-year span, the incidence of root perforation by general dentists and predoctoral dental students ranged from 0% to 7%.68 The literature also has information about perforations as a reported complication in insurance claims, a reason for tooth extraction, and the basis for referral to an endodontist. In a review of 966 dental complications, claims submitted to the Swedish patient insurance program included 183 root perforations related to preparation for posts.69 The teeth identified as having the greatest number of perforations were the mandibular first molar followed by the maxillary first premolar.69 In another study of 119 teeth, iatrogenic perforations and thinning of the dentin to the location of the cementum (a process known as stripping) were responsible for 4.2% of the extractions.70 Of 2,000 patients referred to an endodontist, 1,688 patients required some type of treatment in 2,221 teeth. Perforations were identified in 119 teeth for an incidence of 5.4%, 71 well within the range of 0% to 7% reported in other studies. The aforementioned data on complications reveal why it is important to understand the factors responsible for post loosening, root fracture, and root perforation. Once identified, appropriate steps can be taken to minimize, if not totally avoid, such complications. As already mentioned, the main purpose of a post is to provide a core for a tooth when no other means is available for a coronal buildup; therefore, the following content relates only to clinical situations where a post is needed.

Post loosening Influence of post form

The geometry, or form, of a post also has been identified as a factor that can contribute to post loosening.72, 73 Threaded posts generally are recognized as the most retentive type of post.72, 73 At the same time, threaded posts also are responsible for producing high stess,74 and tapered threaded posts are the worst stress producers.75, 76 In fact, comparative clinical studies have linked high stress from threaded posts to root fracture rates that are higher than those associated with cemented posts.77, 78 One meta-analysis of clinical studies reported survival rates of 81% for threaded posts and 91% for cemented posts.79 Based on these findings, and to avoid potential root fractures, use of threaded posts is not recommended.

Influence of post length Optimizing the post length is an important and safer method of preventing post loosening than the use of threaded posts to increase retention.80 Posts that are threequarters the root length were found to be 24% to 30% more retentive than those that were half the root length or equal in length to the crown height.81 However, with posts that are three-quarters the length of the root, there is an accompanying risk of compromise to the seal of the root canal filling material in teeth with average or shorter-than-average root lengths. What is more, extension of the post spaces to three-quarters the root length also reduces the amount of gutta-percha to less than that required to ensure the maintenance of an adequate seal. Therefore, post length should not be extended to the point that it requires the removal of so much apical guttapercha that the apical seal is unknowingly compromised. A number of laboratory studies have reviewed the amount of gutta-percha needed and its effects on the apical seal. It was determined that a large number of ETT specimens leak when there is only 2.0 mm of apical gutta-percha,82 and most specimens leaked when left with 3.0 mm of gutta-percha.83 In addition, a clinical study found significantly more posttreatment periapical radiolucencies in teeth with less than 3.0 mm of apical gutta-percha.84 However, in the presence of at least 4.0 mm of apical gutta-percha, studies show there is little leakage82, 85 or no leakage.86, 87 Based on these data, it appears that 4.0 mm should be considered the minimum amount of gutta-percha required for an adequate apical seal. However, because length determinations are frequently based on radiographic images and the angulations of radiographs vary clinically, it is proposed that 5.0 mm of gutta-percha be retained apically as measured on a radiographic image. Therefore, the guideline for appropriate length is to retain not 3.0 or 4.0 mm but rather 5.0 mm of apical gutta-percha, as determined radiographically, and to extend the post fully to the point where the gutta-percha is located.

Influence of root selection This 5.0-mm apical guideline for gutta-percha length works well for all teeth except molars. In 1982 Abou-Rass et al 88 prepared post spaces to depths of 4.0 mm and 7.0 mm into a canal space using No. 2 (diameter of 0.8 mm), No. 3 (diameter of 1.0 mm), and No. 4 (diameter of 1.2 mm) Peeso instruments.88 The thickness of remaining dentin was then measured at the 4.0- and 7.0-mm depths along with the incidence of root perforation or thinning to the dentin-cementum border. The authors concluded that the distal roots of mandibular molars and the palatal roots of maxillary molars are the roots best suited for post preparation. They also contended that these roots can be safely prepared to a depth of 7.0 mm using the No. 2 and No. 3 Peeso instruments. In contrast, perforations or root thinning occurred in the mesial roots of mandibular molars as well as the facial roots of maxillary molars.88 Of the 75 mandibular molars included in the study, perforations or instrumenting to only a thin layer of root structure occurred in 27.7% (20) of the prepared mesial roots.88 Based on these results, it is proposed that posts with diameters between 0.8 and 1.0 mm extend no more than 7.0 mm into a molar canal space. This depth guideline should only be applied to the distal roots of mandibular molars and the palatal roots of maxillary molars. The mesial roots of mandibular molars and the facial roots of maxillary molars should not be used for post placement.

Guidelines for prevention of post loosening By design, threaded posts provide greater resistance to post loosening than do cast root-form posts. As mentioned previously, however, posts with a thread design are not recommended because of their potential for generating high levels of internal root stresses and the associated higher incidence of root fracture. Prevention of post loosening is best accomplished by following the recommended guidelines for length and selecting the appropriate primary root. The clinician should leave 5.0 mm of intact apical gutta-percha and extend a post the length of the root space right to the level of the gutta-percha. The exception is in molar teeth, where the post length should be limited to 7.0 mm into the primary roots (palatal root of maxillary molars and distal root of mandibular molars). Care should be exercised to avoid preparing canal spaces in secondary roots (buccal roots of maxillary molars and mesial root of mandibular molars).

Root fracture and root perforation

Influence of threaded posts If the use of threaded posts is avoided, the threat of high internal root stresses is reduced along with the accompanying risk of root fracture.74–76 Multiple clinical studies comparing threaded and cemented posts have shown higher root fracture rates with threaded posts.77–89 One meta-analysis of clinical studies determined that cemented posts had a 10% higher tooth survival rate than did threaded posts.79 An evaluation of 95 ETT where vertical root fractures had occurred identified threaded posts as the most common type of post (64 of 95 teeth) present in teeth that fractured.89

Influence of post length Studies have determined that short posts increase the stress in teeth90, 91 while increases in post length enhance the resistance of a tooth to root fracture.92 Additionally, posts of optimal length offer the greatest rigidity and produce the least amount of root deflection.93 In an examination of 154 teeth that had been extracted because of vertical root fractures, 95 teeth had posts, and 66 of the posts ended in the coronal third of the root.89

Influence of post diameter In addition to post length, post diameter affects the potential for root fracture by increasing stress91, 94 and decreasing resistance to fracture.92 With large-diameter posts (those 1.5 mm or greater), root fracture increased sixfold for every millimeter of decreased root diameter. 76 Unfortunately, there have been no clinical studies comparing fracture resistance of teeth restored with several different post diameters to determine the most appropriate proportional relationship between post diameter and root diameter. However, in 2011 Du et al 95 reported results, based on finiteelement analysis of the mandibular first premolar, showing that posts with a diameter that was 50% of the root diameter exhibited the most favorable stress distribution.95 Nevertheless, the clinical guideline that has been used successfully is not to prepare post spaces that exceed one-third the root diameter in its smallest cross-sectional dimension.

Influence of residual dentin thickness The amount of dentin thickness remaining after root canal treatment is an important

factor because overenlargement of the root canal space for placement of a post can compromise tooth strength. It has been shown that only five teeth have more than 1.0 mm of dentin wall thickness remaining after conventional endodontic therapy. 96 Those five teeth are the (1) maxillary central incisors, (2) maxillary lateral incisors, (3) maxillary canines, (4) mandibular canines, and (5) maxillary first molars (palatal root only).96 According to Ouzounian and Schilder, 96 all other teeth have less than 1.0 mm of dentin thickness after endodontic cleaning and shaping. A study of maxillary first premolars with posts prepared to a depth equal to the clinical crown height determined that 1.0 mm of residual dentin thickness was only present when a 0.7-mm diameter rotary instrument was used to prepare the post space.97 It has been shown that any amount of root canal preparation in mandibular first and second molars following endodontic treatment decreased the residual dentin thickness to less than 1.0 mm.98 Additionally, a study of residual dentin thickness in the distal root of 26 mandibular molars after endodontic treatment alone determined that the canal wall on the furcal side of the root was less than 1.0 mm thick 82% of the time and less than 0.5 mm thick 17.5% of the time.99

Influence of instrument diameter Because of the potential for root perforation or root thinning that can lead to tooth fracture or perforation, appropriate post diameters have been identified in relation to average root diameters. Establishing appropriate post diameters helps to determine the maximum diameter of instruments that can be used safely in each type of tooth to prepare post spaces. One study measured 50 teeth of each type and recommended selection of a post provided its diameter was (1) no greater than one-third the root diameter at the cementoenamel junction; (2) at least 2.0 mm less than the root at the midpoint of the post; and (3) 1.5 mm smaller than the root at the apical end of the post.100 For mandibular incisors, it was proposed that posts be 0.7 mm in diameter. However, the authors proposed a diameter of 1.1 mm for the distal roots of mandibular molars, 1.3 mm for the palatal root of maxillary molars, and 0.9 mm for maxillary first premolars. The largest recommended diameter was 1.7 mm, for maxillary central incisors.100 Another study measured average root dimensions of 125 teeth of each tooth type. The authors recommended that post diameters not exceed one-third of the average root width,101 using a 95% confidence level. Based on these post diameters, certain instruments should not be used to prepare

post spaces. For instance, No. 5 and No. 6 Peeso instruments, No. 6 Gates Glidden instruments, No. 4 and No. 6 round burs, and prefabricated post drills such as the No. 6 and No. 7 ParaPost drills (Coltène/Whaledent) are too large and should not be used. The No. 4 Peeso, No. 5 Gates Glidden, and No. 5 ParaPost drills have diameters that are slightly larger than 1.1 mm and, therefore, are only recommended for teeth with large-diameter roots. Even a No. 4 Gates Glidden drill has a diameter that is too large for the distal root of mandibular molars.99

Influence of post depth and length The previously cited study of root thinning and perforations in molars by Abou-Rass et al88 determined that posts can safely be placed to a depth of 7.0 mm when instruments with diameters between 0.8 and 1.0 mm are used in the distal roots of mandibular molars and the palatal roots of maxillary molars.88 In another investigation where No. 4 Gates Glidden instruments were used to prepare post spaces in the distal roots of 26 mandibular molars, perforations occurred 7.3% of the time and even more frequently when larger drills were used.99 As a result, the authors recommended that Gates Glidden drills larger than No. 3 not be used in the distal roots of mandibular molars. The authors went on to state that “post spaces in such teeth should be limited to the endodontically prepared canal.”99 Findings from other research also support the recommendation that the root canal space not be enlarged after endodontic treatment in the distal roots of mandibular molars.98 Again, it was determined that the residual dentin thickness after root canal treatment was less than 1.0 mm,98 making root fracture or perforation more likely even with self-limiting Gates Glidden mechanical instruments. Similar characteristics and guidelines exist for mandibular second molars as well. To be optimally successful with posts, it seems reasonable to adopt the more conservative diameter recommendations reported in the studies cited. Therefore, the following maximal post diameters are recommended: 0.6 mm for mandibular incisors; 0.9 mm for most teeth (maxillary lateral incisors, maxillary and mandibular premolars, the distal root of mandibular molars, and the palatal root of maxillary molars); 1.0 mm for canines; and 1.1 mm for maxillary central incisors. When molar canals are prepared, the previously recommended guideline of 7.0 mm for post length must be followed in the primary roots (palatal roots of maxillary molars and distal roots of mandibular molars). However, as already mentioned, posts should not be placed in the mesial roots of mandibular molars; as one study showed, 20 of 75 teeth with 7.0-mm-long posts had only a thin layer of remaining dentin or were perforated.88

Influence of root morphology Root morphology has been well described,102 and an understanding of external root morphology is helpful in identifying the teeth and roots that are best suited for posts and less likely to be subjected to root thinning or root fracture. Maxillary root morphology. The nature of the root morphology of teeth in the maxillary arch has been characterized well in the literature. An understanding of this information, coupled with proper root selection for post placement, aids clinicians in negotiating these delicate spaces when placement of a radicular post is planned. Incisors. Maxillary central incisors have a cross-sectional root anatomy that is triangular or ovoid with a lingual taper. 102 Their form and dimensions usually allow placement of posts with the proposed optimal diameter of 1.1 mm.101 Maxillary lateral incisors also possess a single root with a circular, oval, or ovoid crosssectional form. The root canal is triangular in cross section in the cervical area and round apically. 102 However, the smaller root diameter makes it desirable to follow the recommended optimal post diameter of 0.8 mm.101 Canines. Maxillary canines have an oval cross-sectional shape with prominent developmental depressions,102 making their form less ideal than that of maxillary incisors for post placement. However, the root dimensions are usually sufficient to permit posts with the recommended optimal diameter of 1.0 mm.101 Premolars. In a 10-year retrospective study of both metal prefabricated posts and custom posts, posts in maxillary first premolars had the highest failure rate (30%).103 The canals in these teeth are not well suited for enlargement beyond the root canal diameter present after endodontic treatment. In fact, one study of residual dentin thickness validated the negative effect of post preparation on dentin thickness. When the first premolars were prepared using rotary instruments with diameters of 0.9 and 1.0 mm, 61% of the lingual roots and 77% of the buccal roots had less than the desired 1.0 mm of dentin remaining.104 Maxillary first premolars have prominent mesial and distal developmental depressions on the root trunk as well as a relatively narrow mesiodistal root dimension.105 Additionally, in two-rooted first premolars, the developmental root depressions on both the mesial and distal aspects of the root trunk deepen progressively from the cervical line to the furcation.106 When measured, the depth of the mesial furcal concavity increased to slightly more than 1.0 mm at a distance of

4.7 mm apical to the cementoenamel junction.107 In two-rooted maxillary first premolars, the palatal root is the more desirable location for a post because it is usually straighter and does not have the distal root curvature frequently present (66%) in the facial root.108 The palatal root of tworooted premolars also has a surface form that is more conducive to placement of a post because the facial root frequently has a concavity on the furcal aspect of the root.109 In one study of 100 maxillary first premolars, 37 of the teeth had bifurcated roots, and 62% of these teeth had a concavity (with a mean depth of 0.46 mm) on the furcal aspect of the buccal root.106 Another study found that 35 (78%) of 45 maxillary first premolars with two roots had this groove on the palatal aspect of the buccal root.110 A third study of 97 bifurcated first premolars determined that the residual dentin thickness after root canal treatment, at 6.0 mm apical to the cementoenamel junction, was less than 1.0 mm in 53% of the buccal roots on the palatal surface. After post preparation, the dentin thickness in the area of the furcal groove was less than 1.0 mm in 77% of the teeth. The authors recommended that the lingual root be used instead of the facial root when posts are necessary.104 When a single-rooted maxillary first premolar requires a post, the diameter of the canal should be 0.7 mm or less because the mesial and distal developmental root depressions restrict the amount of available tooth structure in the centrally located single root canal.97 Maxillary second premolars are better suited for post placement then are maxillary first premolars because they usually have one root with a slightly larger mesiodistal dimension at the cervical line and slightly greater root length than the first premolar. 105 While mesial and distal developmental root depressions are typically present on the root of maxillary second premolars,108 the mesial depression is shallower than the one present on the first premolar.111 Molars. In maxillary first molars, only the palatal root is well suited for post placement. This canal is ovoid in cross-sectional shape102 and has greater crosssectional dimensions than the facial roots.105 Additionally, while developmental depressions can be present on the facial and palatal surfaces of the lingual root, they are generally shallow. 102 One complicating factor for the palatal root is the frequent presence of a facial curvature in the apical third.112 However, when the recommendation of a 7.0-mm palatal post length is followed, the presence of facial curvature does not create a problem because the root curvature occurs apical to the end of an ideal post. The mesiofacial root of the first molar is relatively thin mesiodistally and also has prominent depressions or flutings on both the mesial and

distal surfaces,110, 111, 113–115 making it unsuitable for post placement. The distofacial root is rounded or ovoid in cross section102 and usually does not have a distal developmental depression,108 but it does contain a developmental depression on its mesial surface.102 It is also smaller faciolingually than the other roots and narrower mesiodistally at its attachment to the root trunk, making it a poor candidate for post placement.111 Maxillary second molars are similar to first molars and, therefore, only the palatal root is suitable for post placement. Their facial roots are even less suitable than the facial roots of first molars because of their distal curvature. Mandibular root morphology. The root morphology of teeth in the mandibular arch is important to understand so that appropriate treatment recommendations are made and post loosening and root fracture are averted. Incisors. Mandibular central and lateral incisors have roots that are broad faciolingually but narrow mesiodistally with substantial longitudinal depressions on both the mesial and distal surfaces.102 These depressions are usually deeper at the junction of the middle and apical thirds of the root.111 The roots’ cross-sectional form is ovoid to hourglass in shape.102 Because of the small mesiodistal root dimension, these teeth are not suitable for canal space enlargement beyond that resulting from endodontic treatment itself. Because prefabricated posts are larger than the maximum diameter recommended for mandibular incisors, these teeth are best treated with custom cast posts and cores made to fit the existing root canal morphology; the optimal post diameter is 0.6 mm.101 Canines. Mandibular canines have an oval cross-sectional shape and prominent developmental depressions.102 They also generally have root dimensions sufficient to permit safe post placement provided that the maximum diameter does not exceed 1.0 mm. Premolars. Mandibular first premolar roots typically are larger faciolingually than they are mesiodistally. Developmental root depressions are frequently found on both the mesial and distal surfaces of the root.102 Nonetheless, the root dimensions generally are large enough to permit the safe placement of posts when they adhere to the recommended diameter of 0.9 mm. Mandibular second premolars too have a root that is ovoid in cross section and have sufficient dimensions to permit placement of a post with the recommended diameter of 0.9 mm. However, mandibular premolars with oval or ribbon-shaped canals should not be subjected to any preparation of the root canal space beyond that

produced during endodontic treatment because it is likely to leave less than the desired 1.0 mm of residual dentin thickness.116 Molars. Data on mandibular first molar root morphology indicate that both the mesial and distal surfaces of the mesial root have developmental root depressions.108, 111 The depression is deep on the mesial surface but even deeper on the distal surface.108 Nevertheless, the distal root of the mandibular first molar is better suited for post placement because the distal root is straighter than its mesial counterpart and rounder in cross-sectional form. Also, the mesial developmental depression on the distal root often is not very deep, and the distal surface may not even have a depression or may possess only a slightly concave surface.108 The distal roots of mandibular molars should not be enlarged beyond the preparation produced by endodontic treatment because the residual dentin thickness after root canal treatment typically is less than 1.0 mm.98 Similar characteristics are present on mandibular second molars.

Guidelines for prevention of root fracture and root perforation Fracture is more likely to occur when roots are weakened by posts that are short because short posts also increase root stress. Therefore, the same guidelines used to minimize post loosening should be followed to minimize, if not prevent, root fracture. As stated previously, the recommended post length for most teeth (except molars) is what remains after 5.0 mm of apical gutta-percha is left in place. For molars, post length should not exceed a maximum length of 7.0 mm in the primary roots (the palatal root of maxillary molar and distal root of mandibular molars). Root fracture is more likely to occur when teeth are weakened by post spaces of an excessive diameter. A good guideline to follow clinically is to prepare post spaces to no greater than one-third the root’s original diameter. In some teeth, any root canal enlargement beyond that produced during root canal treatment will create excessive space because the amount of residual dentin remaining after endodontic treatment typically is 1.0 mm. As mentioned previously, only five maxillary teeth have more than 1.0 mm of root wall thickness remaining after root canal treatment: (1) maxillary central incisors, (2) maxillary lateral incisors, (3) maxillary canines, (4) mandibular canines, and (5) the palatal root of the maxillary first molar. Teeth with less than 1.0 mm of residual dentin thickness following endodontic treatment should not be subjected to further canal enlargement for placement of a post. Overenlargement of a canal space and subsequent fracture can occur when instruments with diameters that exceed the recommended dimensions are used. Therefore, most teeth should be prepared with instruments that do not exceed 0.9 to

1.0 mm in diameter. The largest recommended instrument diameter is 1.1 mm, and that is reserved for use in maxillary central incisors. Teeth with small roots, such as mandibular incisors, should be prepared with instruments that do not exceed 0.6 mm in diameter. Instruments used to prepare the distal roots of mandibular molars and the palatal roots of maxillary first molars should be between 0.8 and 1.0 mm in diameter, provided that the post does not extend more than 7.0 mm into the root canal. As stated previously, root perforation is more likely to occur for any one of the following three reasons: (1) instruments with diameters that cannot be accommodated by the morphology of the root are used; (2) the post is extended too far into a root with developmental root depressions and/or root curvature; and (3) a rotary instrument cuts on an incorrect angulation, and the instrument does not follow the root canal. Root perforations can be avoided if the same guidelines as those recommended for preventing root fracture are followed. That is, post spaces should be prepared so that they do not exceed one-third the root diameter, and instruments with diameters that can be accommodated by the dimensions of the roots being prepared should be used. One of the best means for clinicians to avoid root perforation is to have an understanding of root morphology. Although posts technically can be placed in any root, the maxillary roots most suitable for posts include maxillary central incisors as long as the post has the recommended diameter of 1.1 mm; maxillary lateral incisors when the post diameter does not exceed the proposed diameter of 0.9 mm; maxillary canines as long as the post diameter does not exceed 1.0 mm; maxillary second premolars as long as the post diameter does not exceed 0.9 mm; and the palatal roots of the maxillary first and second molars provided that their diameters are 0.8 to 1.0 mm. Posts should be avoided in the facial roots of maxillary molars. Maxillary first premolars have root morphology that has to be carefully respected if a post is required. There should be no enlargement of the root canal space beyond that produced by root canal treatment due to root dimensions and the depths of developmental root depression. With two-rooted first premolars, the lingual root is preferred because it is generally straighter and has a more suitable surface form. Two-rooted premolars frequently have a furcal depression in the facial root that compromises the facial root when the bifurcation occurs in the cervical one-third of the root because a post extended into the facial root would approximate this depression. When a single-rooted maxillary first premolar with one root canal requires a post, the post diameter should be 0.7 mm or less because the mesial and distal developmental root depression depths restrict the amount of available tooth structure peripheral to the centrally located single root canal. The mandibular roots best suited for posts include mandibular canines, provided

the post diameter does not exceed 1.0 mm, and mandibular first and second premolars when the post diameter is no greater than 0.9 mm. However, mandibular premolars with oval or ribbon-shaped canals should not be subjected to any preparation of the root canal beyond that produced during endodontic treatment because it will result in less than 1.0 mm of dentin. Posts can be placed in the distal roots of mandibular molars but there should be no enlargement beyond that produced by the endodontic treatment because the residual dentin thickness after root canal treatment is less than 1.0 mm. Posts should be avoided in the mesial roots of mandibular molars. Posts also should be avoided in mandibular incisors, if possible. When posts are absolutely needed, there should be no enlargement beyond that produced during root canal treatment. Posts in mandibular incisors should not exceed 0.6 mm in diameter; this dimension precludes the use of prefabricated posts because most commercially available posts have a diameter that exceeds this dimension.

Requirements for Remaining Sound Tooth Structure Sound dentin tooth structure should extend cervically beyond any type of core material. In fact, it is essential that sound tooth structure remain circumferentially to produce a cervical ferrule. The minimum amount of sound tooth structure grasped by a crown is important to optimize a tooth’s resistance to fracture. It is generally recognized that more than 1.0 mm of circumferential tooth structure should be encompassed by the overlying crown,117–120 with some studies121–123 indicating that the minimum should be 2.0 mm. Furthermore, maximum potential resistance can be achieved when that 2.0-mm ferrule encompasses all four of the axial surfaces.123

Post Materials and Their Selection Prefabricated posts have become quite popular, and a wide variety of commercial systems are available. More recently, in response to a need for tooth-colored posts, several nonmetallic posts made of zirconia, glass fiber–reinforced epoxy resin, and ultrahigh polyethylene fiber–reinforced posts are available. Fiber posts require optimal length to avoid post loosening. In laboratory studies, they produced fewer root fractures or more favorable root fractures than metal posts, making them desirable for avoiding clinical root fractures.124–134 Most clinical studies found no root fractures,135–146 but three studies147–149 reported a relatively small number of root fractures (2 of 173, 1 of 106, and 15 of 985, respectively)

while one other investigation150 reported a modest number of root fractures (14 of 99). Fiber posts are not as resistant to post fracture as metal posts, and a small number of post fractures have occurred in clinical studies (1 of 173 and 7 of 105).147, 148 Fiber posts have lower failure risk when there are three or four walls of coronal tooth structure,151 indicating that crown ferrules are important to the success of fiber posts. When parafunctional habits are present, fiber posts have been reported to have higher failure rates.25 The first author of this chapter and the editor of this textbook both have placed a number of fiber posts and observed both success and failure. The post failures involved either post loosening or actual post fracture. These clinical observations, although not being part of a rigorous scientific investigation, suggest that there are some conditions where fiber posts are more likely to fail clinically. Therefore, until more definitive clinical data are available that identify all the factors responsible for fiber post failures, the following guidelines are proposed to help minimize, if not prevent, clinical failure of fiber posts: • Appropriate post length is required because fiber posts are more prone to loosening if their length is not optimal. • Fiber posts can fracture when little or no circumferential ferrule (sound tooth structure) is present. • Fiber posts can fracture, loosen, or induce root fracture when they are subjected to heavy occlusal forces, so excessive tooth contact and all occlusal interferences should be eliminated. Some clinicians consider a fiber post to be a good choice for ETT even when the root is short, there is no tooth structure below the core material (no ideal cervical crown ferrule), and heavy occlusal forces are present. The thought process expressed by these clinicians is that failure of a fiber post, including post fracture, still leaves the root in a restorable condition. Indeed, this situation may occur clinically, but the premise that the remaining root is restorable may not always be true. The first author of this chapter has encountered both loosening and fracture of fiber posts. Most, but not all, of those failures resulted in a root that could be restored again. However, challenges can arise with removal of the remaining post segment because the process is not as easy as some would portray. These fractures of fiber posts often occurred within the first 1 to 3 years in service. The thought of charging the patient to remove the fractured post, place another fiber post, and make a replacement crown was not appealing. Moreover, the patient might reasonably have concluded that the same type of failure could occur again before an appropriate

period of clinical service had transpired. In light of such failures, a metal post was used to replace the failed fiber post to provide more sustained clinical service for patients. Therefore, while fiber posts are an option, they are not the most cost-effective treatment when the post is shorter than ideal, when there will be little or no ferrule, or when excessive occlusal forces are present.

Summary The information presented in this chapter is intended to permit clinicians to make data-driven decisions in their clinical treatment of ETT based on known clinical complications. Guidelines have been provided for the decision of whether or not to place a post, the selection of an appropriate type of post material (if a post is used), and the indications and contraindications to placing crowns on ETT.

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quartz fiber-reinforced epoxy resin posts. Int J Prosthodont 2003;16:39–44. 139. Monticelli F, Grandini S, Goracci C, Ferrari M. Clinical behavior of translucent-fiber posts: A 2-year prospective study. Int J Prosthodont 2003;16:593–596. 140. King PA, Setchell DJ, Rees JS. Clinical evaluation of a carbon fiber reinforced endodontic post. J Oral Rehabil 2003;30:785–789. 141. Tidehag P, Lundstrom J, Larsson B, Molin M. A 7-year retrospective study of Composipost root canal posts [abstract 4080]. J Dent Res 2004;83(special issue A). 142. Grandini S, Goracci C, Tay FR, Grandini R, Ferrari M. Clinical evaluation of the use of fiber posts and direct resin restorations for endodontically treated teeth. Int J Prosthodont 2005;18:399–404. 143. Mannocci F, Qualtrough AJ, Worthington HV, Watson TF, Pitt Ford TR. Randomized clinical comparison of endodontically treated teeth restored with amalgam or with fiber posts and resin composite: Five-year results. Oper Dent 2005;30:9–15. 144. Naumann M, Sterzenbach G, Franke A, Dietrich T. Randomized controlled clinical pilot trial of titanium vs glass fiber prefabricated posts: Preliminary results after up to 3 years. Int J Prosthodont 2007;20:499–503. 145. Cagidiaco MC, Radovic I, Simonetti M, Tay F, Ferrari M. Clinical performance of fiber post restorations in endodontically treated teeth: 2-year results. Int J Prosthodont 2007;20:293–298. 146. Turker SB, Alkumru HN, Evren B. Prospective clinical trial of polyethylene fiber ribbon-reinforced, resin composite post-core build-up restorations. Int J Prosthodont 2007;20:55–56. 147. Wennstrom J. The C-POST system. Compend Contin Educ Dent Suppl 1996; (20):S80–S85. 148. Naumann M, Blankenstein F, Dietrich T. Survival of glass fiberreinforced composite post restorations after 2 years—An observational clinical study. J Dent 2005;33:305–312. 149. Ferrari M, Cagidiaco MC, Goracci C, et al. Long-term retrospective study of the clinical performance of fiber posts. Am J Dent 2007;20:287–291. 150. Segerstrom S, Astback J, Ekstrand KD. A retrospective long term study of teeth restored with prefabricated carbon fiber reinforced epoxy resin posts. Swed Dent J 2006;30:1–8. 151. Cagidiaco MC, Garcia-Godoy F, Vichi A, Grandini S, Goracci C, Ferrari M. Placement of fiber prefabricated or custom made posts affects the 3-year survival of endodontically treated premolars. Am J Dent 2008;21:179–184.

Treatment Planning Considerations for Endodontically Treated Teeth “Because I’ll have you know, Sancho, that a mouth without teeth is like a mill without its stone and you must value a tooth more than a diamond.” —Miguel de Cervantes, Don Quixote Preservation of the natural human dentition is an important factor in efforts to promote good oral health. The mouth has been referred to as “a window into our health.”1 We are attracted to a beautiful smile and have pity on those individuals with unsightly dentitions. Consciously, or even unconsciously, many make snap decisions as to a person’s socioeconomic status, integrity, reliability, and overall “value” by first impressions. Even in biblical times, the value of teeth was recognized, as justice was meted out “eye for eye, and tooth for tooth” (Matthew 5:38, The Bible, New International Version). Before the recent option of replacing broken-down teeth with dental implants, clinicians routinely attempted—sometimes with heroic efforts—to save teeth for as long as possible before extraction. While implant placement has increased and the population in general seems to readily accept this procedure, there is some sense that the pendulum is swinging too far in the direction of replacing teeth with implants. Some dentists seem inclined to routinely recommend replacement of teeth

that may otherwise have a good prognosis both endodontically and restoratively. The purpose of this chapter is to describe the various factors that must be evaluated when the practitioner is considering a treatment plan that may include endodontically treated teeth. Various clinical situations will be described in which teeth that have had—or will have—root canal treatment (RCT) are to be reviewed in developing a treatment plan.

Outcomes of Endodontic Therapy The first consideration of importance is to recognize that for a treatment involving an endodontically treated tooth to have a predictable outcome, the endodontic procedure must be skillfully accomplished. Perhaps this statement seems selfevident, but endodontists frequently report that they need to re-treat teeth that have initially been poorly treated (Fig 2-1). In fact, when the quality of RCT in general is evaluated, the level of quality is often disappointingly low. 2, 3 Patients, however, cannot see what has been done inside the roots of their teeth and can only judge a clinician on the aspect of pain relief and how they were treated.

Fig 2-1 (a) Inadequately performed RCT, including failure to find the second mesiobuccal canal, has resulted in a periapical lesion (arrow). (b) This radiograph shows well-prepared and filled root canals including two mesiobuccal canals.

When RCT is done correctly initially, it has a good prognosis. Many studies have evaluated the success rate of various types of endodontic therapy. 4–7 Torabinejad et al 6 did a systematic review of the literature pertaining to the outcomes of nonsurgical endodontic therapy. A strict set of parameters was followed for inclusion in the meta-analysis. Their results showed an overall radiographic success rate of 81.5% over a 5-year period. Friedman et al7 reported similar healing

results after 4 to 6 years. It is noteworthy that the rate of endodontic success is higher when RCT is performed before apical lesions are present.4 Also, when treatment mishaps occur, the prognosis is affected. It is therefore important for clinicians to recognize their own limitations when providing any type of dental care and to aim for the best treatment possible for the patient. Referring a patient to a specialist for RCT may provide the best foundation for a good outcome. The following are components of successful RCT that can provide a dependable basis for restoring an endodontically treated tooth.

Diagnosis and Treatment Planning Successful RCT is based on numerous factors, starting with an accurate diagnosis and appropriate treatment plan. Each individual patient presents with a unique set of conditions that the clinician must manage in order to provide a better oral health status for that patient. The patient’s medical and dental histories provide the background for collecting the necessary information. Because this chapter is about the endodontic aspects of the overall treatment plan, the focus will be on diagnosis as it relates to the status of the pulp, the anatomy of the pulp and the roots, and the conditions affecting these tissues.

Assessment of the pulpal status Pulpal status is conveniently described as normal pulp, reversible pulpitis, irreversible pulpitis, or pulpal necrosis. However, it can be a challenge to make diagnostic decisions when the examination findings overlap, and a clearcut diagnosis is difficult to make. It is beyond the scope of this chapter to go into detail about endodontic diagnosis; the interested reader will find excellent material in any current endodontic textbook. For practical purposes, we can say that endodontic treatment is indicated when the pulpal diagnosis is either irreversible pulpitis or pulpal necrosis; in some cases, however, it may be prudent to recommend RCT even in situations of normal pulp or reversible pulpitis (Fig 2-2). For example, RCT may be recommended in teeth with normal pulpal conditions or reversible pulpitis if the pulpal health might be compromised by the particular restorative or prosthetic procedure planned.

Fig 2-2 The deep caries lesion may not have invaded the pulp yet, but if placement of a prosthetic crown is planned, it may be prudent to recommend RCT before completion of the prosthetic treatment.

Anatomical considerations Successful RCT requires a thorough knowledge of tooth anatomy and root canal morphology, both of which can be very diverse.8 Variations occur with respect to the number of roots, the number and shape of canals within these roots, and even the frequency of variations. Numerous factors can account for these variations, such as tooth location, age of the patient, ethnicity, gender, congenital conditions involving tooth development, and even the means of assessment or the definition of what constitutes a canal.9–11 When an endodontically treated tooth is assessed, careful attention should be given to the external root morphology, the number of roots, the shape of the root canal system, and the variations and anomalies that are particular to the tooth. When the internal morphology and obturation are evaluated and compared with the external anatomy, the filled canal shape should match the flow of the external anatomical outline. When endodontic procedures are performed correctly, the external and internal radiographic appearance of the root should be harmonious: The root canal filling should be centered in the root and correspond to the external shape of the root (Fig 2-3).

Fig 2-3 (a) The root canal fillings are centered in the roots, indicating careful attention to root canal morphology and root anatomy. (b) Wellprepared canals correspond to the shape of the root, even when multiple canals are present.

Schilder12 described five objectives for root canal preparation: 1. There is a continuously tapering funnel shape from the apex to the access cavity. 2. Cross-sectional diameters are narrower at every point toward the apex. 3. The root canal preparation flows with the shape of the original canals. 4. The apical foramen remains in its original position. 5. The apical opening is kept as small as practical. In addition, Schilder12 named four biologic objectives for these preparations: 1. Treatment procedures are confined to the roots. 2. Necrotic debris is not forced beyond the apical foramina. 3. All pulp tissues are removed from the root canal space. 4. Sufficient space exists for intracanal medicaments and irrigants. These objectives provide a basis for assessing the quality of the endodontic procedure prior to restoration of the tooth. Deviation from the original canal shape is referred to as transportation of the canal. The greater the transportation, the greater the likelihood of a poor endodontic outcome, resulting in the need for either endodontic retreatment or extraction of the tooth. Root canal systems The root canal system is complex (Fig 2-4), and its anatomy has been studied

extensively for many years. Of special interest in the current context, Weine et al 13 called attention to the frequent presence of two canals in the mesiobuccal roots of maxillary molars. Pineda and Kuttler14 and Vertucci 15 developed classification systems for canal configurations in individual roots. Research in root canal morphology has led to descriptions of more than 20 canal configurations.11

Fig 2-4 (a) The complexity of the root canal system is well illustrated in these sections of maxillary molars. Note the variety of canal configurations in the mesiobuccal roots and in particular the location of the second mesiobuccal canal in the molar on the right. (b) A radiograph of a maxillary molar seems to show two palatal roots (arrows). (c) On the patient’s request, the tooth was extracted; two palatal roots were identified (arrows).

These considerations are important for the evaluation of a tooth that has undergone RCT. They also point to the challenges inherent to treating teeth with endodontic disease prior to restoration to full function. Achieving full function requires that the treatment-planning process be a teamwork process: RCT can be performed on almost any tooth, but restorability must be determined prior to the endodontic component of treatment. Communication among the various treating dentists before, during, and after RCT offers the best possibility of an optimal outcome.

Assessment of other conditions Cracked/fractured teeth Fracture lines involving cusps of teeth have been a problem in dentistry, probably throughout human history. The pain associated with such fracture lines was described by Gibbs,16 who termed it cuspal fracture odontalgia. Every dentist has probably had a patient who complains about pain on chewing and later shows up with the broken-off cusp, usually from a premolar tooth. Whether or not the pulp is directly involved (by exposure), it is usually necessary to complete RCT before the

tooth is restored. Diagnosis of a fracture line under a cusp, before it breaks off, can be a challenge and will be discussed in the next section on infractions. Teeth may develop cracks and fracture for a number of reasons, including trauma, excessive masticatory forces, and iatrogenic incidents. Regardless of etiology, when cracks or fractures develop in dental hard tissues it is not possible to repair them, except for a short period of time with bonding agents. In contrast, bone and cartilage routinely undergo repair following fracture. Although tooth fractures and cracks cannot be healed, it is possible in many cases to maintain such teeth for various periods of time following identification and diagnosis. For convenience in discussing cracks and fractures, three categories will be used: enamel craze lines, infractions, and vertical root fractures (VRFs). Enamel craze lines. Craze lines are small cracks that are confined to the enamel of teeth (Fig 2-5). They are not typically visible unless light rays highlight them incidentally. They develop over time, so they probably can be found in most teeth eventually. Occasionally they will show stains from exposure to liquids such as coffee and red wine. Because these cracks are confined to enamel, they have no pulpal impact, and no treatment is necessary, except optional bleaching if they are stained. There is no evidence that craze lines progress to involve more than enamel.

Fig 2-5 Enamel craze lines (arrow) are common and present no particular problem other than their potential for staining.

Infractions (cracked teeth). The term cracked tooth is commonly used to

describe a tooth that has developed an infraction, which is defined as “a fracture of hard tissue in which the parts have not separated”17 (Fig 2-6). Cameron18 incorrectly defined this condition as cracked tooth syndrome; the use of syndrome is not appropriate for pain associated with fractures in teeth. It is, however, a situation with a variety of symptoms, and diagnosis can be very difficult.

Fig 2-6 (a) Infractions (arrow) can be identified visually with the help of dyes, in this case a red dye. Infractions usually run in a mesiodistal direction; they may be asymptomatic or associated with pain on chewing and cold stimuli. (b) A tooth extracted because of symptoms associated with an infraction shows the presence of the infraction (arrow). They typically originate in the crown of the tooth and progress in an apical direction. (c) On

rare occasions, infractions run in a faciolingual direction (arrow).

Mandibular molars and maxillary molars and premolars are the teeth most frequently associated with infractions. The teeth usually have vital pulps and the infractions typically run in a mesiodistal direction. They begin in the crowns of teeth and progress in an apical direction. Not all teeth with infractions are symptomatic, but when symptoms develop they can range from pain on chewing, to an exaggerated response to cold stimuli, to severe pain episodes that can mimic trigeminal neuralgia; chronic orofacial pain can also develop. The wide range of pain experiences is probably why Cameron18 used the term syndrome to describe this dental situation. The etiology of infractions is probably in most cases related to occlusal forces, whether from regular daily chewing or isolated trauma such as blows to the underside of the mandible.19–25 It is likely that teeth with infractions become symptomatic when the infractions become invaded by bacteria26 (Fig 2-7). Bacteria stimulate inflammation in the pulp, whether or not the infraction communicates directly with the pulp tissue. The inflamed tissue is responsible for the exaggerated cold response. It is also likely that the tooth will become sensitive to biting when the infraction progresses from the tooth crown to the root, and the bacteria that will soon occupy the infraction then stimulate an inflammatory response in the adjacent periodontal ligament (PDL).

Fig 2-7 Infractions become populated with bacteria very quickly and produce an inflammatory response in the pulp (located to the right in this section), whether they communicate directly with the pulp (as in this case) or not. This explains why such teeth respond abnormally to cold stimuli.

Diagnosis of infractions is complicated by many factors. Because infractions are usually located in a mesiodistal direction in the crown, they are not visible on radiographs. Before the infractions progress down the roots to significantly involve the PDL, patients are unable to point to the problem teeth. Based on the patient’s complaints, the first goal of examination is to identify the problem teeth and the second is to determine the pulpal condition of these teeth. The presence of an infraction can be determined by the use of various biting tests (Fig 2-8a), with the aid of colored dyes (see Fig 2-6a), and through transillumination with an intense light source27 (Fig 2-8b). In contrast to the way enamel craze lines are highlighted by intense light, infractions actually block the transmission of light, clearly identifying their presence.

Fig 2-8 (a) The bite test is a useful way to identify a tooth with an infraction. After biting down on a wet cotton roll (or on one of many types of biting devices), the patient will often experience a strong response when he or she releases biting pressure—the so-called release pressure pain. (b) The use of an intense light, such as that from a fiber-optic light source, will illuminate the part of the crown near the light, but the light stops at the infraction, which involves both enamel and dentin. In contrast, enamel craze lines only involve enamel, through which light rays travel unimpeded.

The status of the pulp—reversible or irreversible pulpitis— can be determined as in other situations of pulpal inflammation, that is, by the presence or absence of lingering pain to application of cold stimuli. If the pulp is reversibly involved, placement of a complete-coverage crown may be enough initially, but Krell and Rivera28 showed that about 20% of these teeth subsequently developed irreversible pulpitis. If the patient wishes to retain the tooth for as long as possible, it may be advisable to perform RCT in anticipation of a later need before a complete-

coverage crown is placed. There is some promising information29 about the use of bonded resin to cover the occlusal surfaces to resist further progression of infractions. To determine if an infraction has progressed to the root of the tooth, the use of a periodontal probe can provide some information. However, because the pocket that develops in the PDL adjacent to the infraction in the root is very narrow, it is usually necessary to anesthetize the area first; otherwise the procedure will be very painful for the patient. The prognosis for teeth with infractions is not good. Fuss et al30 have reported that many of these teeth are extracted within 5 years following diagnosis of infraction. However, insufficient data are available to make a statement about the expected survival time of these teeth. Clinicians can only explain to patients that once this condition develops it cannot be reversed, and that it is only possible to make an effort to prolong the inevitable. With a full understanding of the poor longterm prognosis, many patients still wish to maintain such teeth for as long as possible, and that is where RCT and complete-crown coverage may be considered. It is prudent, however, to explain to such patients that periodic radiographic evaluation is recommended so that when bone loss is evident plans can be made for extraction before a large amount of bone is lost. As the infraction progresses, the eventual result is either that the tooth splits vertically or, when the infraction involves a cusp, that the cusp fractures off, with or without exposure of the pulp. Vertical root fractures. VRFs differ from infractions in several aspects.31 With few exceptions, VRFs occur in endodontically treated teeth (Fig 2-9). The direction of fractures is more often in a faciolingual orientation, and symptoms for the most part are mild. In some patients, symptoms are absent or so mild that the patients are unaware of any problems. VRFs typically originate from the apical end of the root and progress toward the crown. The incidence of VRFs in restored endodontically treated teeth ranges between 2% and 10%.32–37

Fig 2-9 (a) VRFs (arrow) occur mostly in endodontically treated teeth and typically originate from the apical end and progress toward the crown; they usually run in a faciolingual direction in contrast to infractions, which run mesiodistally. (b) The fracture (arrow) is evident in the extracted tooth.

VRFs are sometimes mistaken for failing RCTs. This is understandable because the complaints and clinical findings often are similar. The management for these two conditions is not the same, so the correct diagnosis is essential to determination of the best treatment. A VRF can be differentiated from a failing RCT by a number of factors: the history of the tooth’s treatment, presenting signs and symptoms, radiographic information, and data from the clinical examination.31, 38–42 Typically, a VRF appears a considerable time after RCT and restoration of the tooth. The tooth may have been comfortable and fully functioning for years when suddenly it begins to feel uncomfortable during chewing; there may also be a sudden appearance of some swelling, usually on the facial aspect of the tooth. Radiographically, if a lesion has developed, it appears to be located along the length of the root; in contrast, if the lesion is the result of a failing RCT, the lesion appears more apical to the root. Because fractures associated with VRFs tend to have a faciolingual orientation, it is not unusual for fracture lines to be visible radiographically. In maxillary premolars and the mesial roots of mandibular molars, a “halo” appearance involving the apical and lateral aspects may be noted on one side or both sides of the involved roots.41, 43 As with many other dental conditions, direct observation can often provide the definitive information for arriving at a diagnosis of VRF. For instance, it is often possible to probe a fairly narrow periodontal pocket along the fracture line to the root apex. In contrast to infractions, which originate in the crown of the tooth, VRFs

originate in the apical part of the tooth and progress in a coronal direction. When a VRF is suspected, a minor surgical exploration accomplished by reflection of a small tissue flap in the area will often reveal the fracture line. Another distinct difference between an infraction and a VRF is that the former is very small (until the tooth splits), while the latter by comparison is quite wide in diameter. Treatment for a tooth with a VRF is usually extraction, which should be performed as soon as possible after the diagnosis to preserve as much of the adjacent alveolar bone as possible. Because the symptoms are often minimal, patients may want to postpone treatment, but this delay results in a very poor alveolar ridge after extraction. This problem should be carefully explained to the patient. There is one exception to the recommendation for extraction of teeth with VRF: When the involved tooth is a multirooted maxillary molar and the fracture is located in one of the facial roots (Fig 2-10), surgical resection of the affected root may leave a tooth that can still function quite well for many years, as has been demonstrated in the periodontal literature.44

Fig 2-10 (a) The mesiobuccal root of the maxillary left first molar has developed a vertical root fracture. (b) After the prosthetic crown has been removed, the mesiobuccal root is resected, leaving two roots to support the new restoration. (c) The 3-year follow-up radiograph shows a wellfunctioning tooth (which is still functioning at the time of writing).

Combined endodontic-periodontal problems A difficult diagnostic and treatment-planning problem is the combined endodontic and periodontal situation. The tooth’s pulpal and periodontal tissues are closely connected both at the apical opening of the root canal and through the many lateral connections present. This in part explains the difficulty in deciding the origin of some periradicular lesions. The unfortunate result is that in some cases, teeth receive RCT even though the pulps may be healthy, or they may be extracted when associated with lesions that are presumed to be of severe periodontal origin, and the teeth are not expected to

survive. To prevent such mistakes, clinicians must carefully arrive at the correct diagnosis based on collection of pertinent information such as the status of the dental pulp, evaluation of periradicular lesions, and consideration of other conditions such as infractions or VRFs. After the collection of adequate data, one of the following diagnoses may be applied: pulpal disease, periodontal disease, or a true combination of the two. Pulpal disease can cause periradicular lesions that radiographically appear similar to those of periodontal disease (Fig 2-11). Pulp testing to determine the status of the pulp can clarify the situation in most cases, although even necrotic pulps may have pain receptors that can be stimulated in pulps that are far from healthy. If the testing indicates pulpal disease, then RCT can result in healing of any periradicular lesion that may be present.

Fig 2-11 (a) Radiograph of the maxillary right second premolar of a patient who complained about soreness around the tooth. The tooth did not respond to cold stimuli. There was a 6-mm narrow periodontal pocket on the mesial aspect of the second premolar, and the tooth was sensitive to percussion. Based on the findings, a diagnosis of pulpal necrosis was made. (b) RCT has been completed, and the diagnosis of pulpal necrosis has been confirmed. (c) The 7-month follow-up radiograph shows the healing of the initial lesion. The tooth is comfortable, and no periodontal treatment has been necessary. (Courtesy of Dr Harold “Jay” Jacobson, El Cajon, CA.)

Periodontal disease involving a single tooth is not common, so when that occurs it is easy to suspect the presence of pulpal disease. Pulp testing, along with clinical examination, may provide enough information to decide if the condition is related to the pulp or PDL. In general, periodontal probing will reveal wider pockets when the lesion is of periodontal origin. Lesions of pulpal origin tend to be narrower, similar to those seen in teeth with infractions or VRFs. Occasionally it may be so difficult to obtain reliable information about the status of the pulp that an exploratory pulpectomy may be indicated to allow a definitive diagnosis. The bottom line, however, is that if a periradicular lesion is not of pulpal origin, RCT will not change the situation. True combined lesions of endodontic and periodontal origins do occur. If a thorough examination reveals that such a diagnosis is appropriate, RCT is likely to have some positive effect on the condition, but periodontal treatment is also needed.

Other factors may contribute to development of periradicular lesions. For instance, failing RCTs and poorly completed coronal restorations provide pathways for bacterial contamination. Linked directly with the need for adequate endodontic therapy is a good coronal restoration; coronal leakage has been well established as a major cause of endodontic treatment failure.45–47 Root perforations may be another cause of lesions of combined endodonticperiodontal origin (Fig 2-12). These perforations may result from extensive caries lesions, resorption, or from operator error during canal instrumentation or post space preparation.48

Fig 2-12 (a) A root perforation was created during post space preparation of a mandibular left second molar; a further treatment error was cementation of a post into the perforation. (b) A follow-up radiograph taken 6 months after retreatment and repair of the perforation shows that the apical lesions have healed satisfactorily; however, a furcal lesion has developed as a result of the perforation. At the time of follow-up, the lesion was not probeable yet. The repair was made with amalgam at the time; today that repair would be accomplished with mineral trioxide aggregate, a material that has been shown to be very suitable for perforation repairs.

Finally, developmental malformations can lead to unusual periradicular lesions. Radicular invaginations or grooves are one example of this situation. As long as an intact epithelial attachment remains, the periodontium is maintained in a healthy status. However, once the attachment is broken, the invagination is extremely difficult to manage and often creates a self-sustaining infrabony pocket.49 Resorption Root resorption complicates treatment of teeth; it is unpredictable both in terms of appearance of the lesion and response to treatment. For practical purposes, resorption can be classified into the following categories: eruption-related (which is resorption of primary teeth as part of succedaneous tooth eruption and will not be discussed further in this chapter); trauma-related; pressure-related; cervical

invasive; and idiopathic resorption. Trauma-related root resorption follows traumatic dental injuries and is related to damage to the root cementum and the PDL. Initial resorption after dental trauma is termed repair-related resorption and involves only cementum. It is difficult to demonstrate this type of resorption radiographically. However, it plays a role in the repair process after injury to the PDL during which new PDL fibers are inserted into the new cementum that forms as part of this process. Trauma-related resorption requires no treatment and is of concern only if it continues so that the resorption begins to involve the subjacent dentin. The resorptive process then may take one of two pathways (occasionally both can occur simultaneously): (1) infection-related (inflammatory) and (2) ankylosis-related (replacement) resorption. Infection-related root resorption has a dual etiology when it occurs following a traumatic dental injury (Fig 2-13). First there is damage to the PDL with subsequent resorption of cementum; if resorption progresses to the dentin, then the second etiologic factor arises, that is, the presence of bacteria in the pulp space. The bacteria will have a stimulating effect, through the dentinal tubules, on the osteoclasts to aggressively resorb both tooth structure and surrounding bone. If this infected necrotic pulp tissue is not removed (by RCT), the bacterial presence will stimulate continued resorption of both tooth structure and adjacent alveolar bone. This process is the basis for recommending endodontic evaluation and treatment of teeth involved in traumatic dental injuries. It has been well established that RCT in these types of trauma-related resorptions will both prevent infection-related resorption and arrest the resorption if it has already started.50

Fig 2-13 Infection-related resorption. Radiograph taken 6 months after replantation

of the mandibular central incisors, which had been avulsed in an accident. Failure to perform RCT in a timely manner (ideally within 2 weeks following replantation) allowed the pulps to become infected, which stimulated both infection-related root resorption and bone resorption. This type of resorption is the result of initial damage (from the accidental avulsion) to the cementum and PDL and the presence of bacteria in the pulp tissue. Infection-related (inflammatory) resorption can be predictably prevented with timely RCT. A variation of the resorption just described is infectionrelated resorption that takes place inside the root canal, referred to as internal resorption (Fig 2-14). This is a very rare type of resorption and is often confused radiographically with external invasive resorption (to be described in the following paragraphs).51 The mechanism is very similar to that of the external variety in that bacteria are necessary to stimulate the resorptive process, and there probably has to be some damage or disruption in the predentin layer, allowing clastic cells to resorb underlying dentin.

Fig 2-14 Internal resorption. (a) The resorptive cavity is centered in the root of the tooth. (b) RCT will successfully arrest the resorption. (Courtesy of Dr Steve Morrow, Loma Linda, CA.)

The resorptive process is in some ways self-limiting in that the resorption will stop when the pulp undergoes necrosis from the presence of the bacteria. The treatment for internal resorption is RCT—after a careful diagnosis has been established so that a case of external invasive resorption, which can initially look like internal resorption, is not mistreated. The second type of trauma-related root resorption is called ankylosis-related resorption because it occurs as a result of bony fusion (ankylosis) with dentin,

resulting in a gradual replacement of the root structure with bone (Fig 2-15). This type of resorption is related to extensive damage to the PDL, followed by resorption of cementum without subsequent repair, thus exposing the dentin to osteoclastic removal followed by replacement with bone. This process cannot be arrested once begun, and the status of the pulp in the tooth (healthy or diseased) is immaterial. In a young person who is still growing, ankylosis prevents the tooth from erupting and the adjacent alveolar process from developing.52 Fortunately, there is now a procedure —decoronation—that can be used to allow continued bone formation.52 In adults, teeth undergoing replacement resorption can last for many years even when ankylosed.

Fig 2-15 Ankylosis-related resorption. (a) The left central incisor of a 13-year-old girl has ankylosed 4 years after a traumatic intrusion. Intruded teeth in young patients (younger than 15 years) should be allowed to spontaneously reerupt. In this case, the tooth did not reerupt but became ankylosed. (b) Ankylosis-related (replacement) resorption has prevented normal eruption. The pulp is vital, illustrating that the pulp plays no role in ankylosisrelated root resorption.

Pressure-related resorption is that seen when an erupting tooth causes pressure on an adjacent tooth (Fig 2-16) or when some lesions cause pressure as they grow in size. The resorption that results from orthodontic movement is also pressure related; interruption of the orthodontic movement will arrest the resorption.

Fig 2-16 Pressure-related root resorption. (a) In this case, a third molar has exerted pressure against the distal aspect of the second molar. (b) The effect of the pressure on the second molar can be seen clearly after removal of the third molar. RCT is not indicated, but a periodontal problem may result if the bone does not fill in on the distal aspect of the tooth.

Cervical invasive resorption (Fig 2-17) is probably the most frustrating of resorptive entities. It can occur without any warning and may not always be associated with an event—trauma or otherwise—that would predict its occurrence. A history of trauma is often recognized, but other events such as orthodontic treatment and other dental procedures have been implicated.53 A lack of recognizable etiology is not uncommon. This is also a type of resorption that has no connection with the status of the pulp.

Fig 2-17 Cervical invasive resorption. (a) The resorption (arrow) may have resulted from trauma to the cervical cementum during removal of the third molar. Although the pulp is not directly affected by the resorptive process, management of this tooth would probably include RCT. (b) The radiograph of a canine with invasive resorption (arrow) illustrates the conditions sometimes observed years after a traumatic injury. Treatment options in such cases may include efforts to repair the resorbed areas from either an internal or an external approach, but

replacement with an implant is probably a more predictable approach to management.

Treatment for cervical invasive resorption is quite successful if the lesion can be restored before too much tooth structure is lost. It is often necessary to perform the restorative procedure in conjunction with a periodontal tissue flap, raised for more convenient access. Because the pulp is not usually affected by the resorptive lesion, it is not necessary to do RCT as part of the treatment. RCT is often included, though, if the lesion is close to the pulp or if pulpal symptoms are part of the clinical findings. The material of choice for restoring the lost tooth structure is glass-ionomer cement. The last type of resorption to be discussed is referred to as idiopathic resorption54 (Fig 2-18) because the etiology is obscure. It can involve a single tooth or several teeth; in the latter case, it is referred to as multiple idiopathic tooth resorption. As with resorptions in general, symptoms are mild or nonexistent. Mild soreness when the soft tissues surrounding the resorbing tooth are touched may be the only signal that something is happening to the tooth. This type of resorption can be quite aggressive, and a great amount of tooth structure can be lost. As with resorption other than infection-related resorption, the pulp plays no role, and much tooth structure can be lost before the resorptive lesions come close to the pulp cavities. The resorptive process does not seem to penetrate the predentin layer at the periphery of the pulp tissue.

Fig 2-18 Idiopathic resorption. This type of resorption, which often includes several teeth and then is termed multiple idiopathic resorption (arrows), has no known etiology. Management of such situations is very difficult. Restoration of resorbed areas, if accessible, can provide some con tinued function for the affected teeth, but eventual loss of such teeth is most likely to occur.

Treatment for idiopathic resorption has a very disappointing history. Frequently, so much tooth structure is lost that restoration of such teeth is very difficult. In addition, continued resorption may take place, further frustrating the management of these situations. If identified early, the affected tooth or teeth may be maintained for some time, making it worth the effort to treat. The practical option in many of these situations, however, is likely the replacement with dental implants. In any case, performance of RCT on a tooth with idiopathic resorption is not recommended unless the pulp is diseased.

Summary Restoration of endodontically treated teeth requires careful planning. This involves

evaluation of the endodontic treatment (preferably both before and after the treatment), an understanding of the complexities involved in RCT, and a recognition that many factors affect the outcome of the combined endodontic-prosthodontic management of patients. As in so many areas of medicine and dentistry, teamwork is often the key to success.

References 1. National Institute of Dental and Craniofacial Research. Sidebar: The 21stCentury Mouth: A Window into Our Health. 20 March 2010. http://www.nidcr.nih.gov/Research/ResearchPriorities/​ StrategicPlan/21stCenturyMouth.htm. Accessed 24 May 2012. 2. Boucher Y, Matossian L, Rilliard F, Machtou P. Radiographic evaluation of the prevalence and technical quality of root canal treatment in a French subpopulation. Int Endod J 2002;35:229–238. 3. Kirkevang LL, Hørsted-Bindslev P. Technical aspects of treatment in relation to treatment outcome. Endod Top 2002;2:89–102. 4. Sjögren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long-term results of endodontic treatment. J Endod 1990;16:498–504. 5. Setzer FC, Boyer KR, Jeppson JR, Karabucak B, Kim S. Long-term prognosis of endodontically treated teeth: A retrospective analysis of preoperative factors in molars. J Endod 2011;37:21–25. 6. Torabinejad M, Kutsenko D, Machnick TK. Levels of evidence for the outcome of nonsurgical endodontic treatment. J Endod 2005;31:637–646. 7. Friedman S, Abitbol S, Lawrence HP. Treatment outcome in endodontics: The Toronto Study. Phase 1: Initial treatment. J Endod 2003;29:787–793. 8. Cleghorn BM, Goodacre CJ, Christie WH. Morphology of teeth and their root canal systems. In: Ingle JI, Bakland LK, Baumgartner JC (eds). Endodontics, ed 6. Hamilton, ON: BC Decker, 2008:151–220. 9. Hess W. The Anatomy of the Root-Canals of the Teeth of the Permanent Dentition, Part 1. New York: William Wood, 1925. 10. Ross IF, Evanchik PA. Root fusion in molars: Incidence and sex linkage. J Periodontol 1981;52:663–667. 11. Sert S, Bayirli GS. Evaluation of the root canal configuration of the mandibular and maxillary permanent teeth by gender in the Turkish population. J Endod 2004;30:391–398. 12. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:269–296.

13. Weine FS, Healey HJ, Gerstien H, Evanson L. Canal configuration in the mesiobuccal root of the maxillary first molar and its endodontic significance. Oral Surg Oral Med Oral Pathol 1969;28:419–425. 14. Pineda F, Kuttler Y. Mesiodistal and buccolingual roentgenographic investigation of 7,275 root canals. Oral Surg Oral Med Oral Pathol 1972;33:101–110. 15. Vertucci FJ. Root canal anatomy of the human permanent teeth. Oral Surg Oral Med Oral Pathol 1984;58:589–599. 16. Gibbs JW. Cuspal fracture odontalgia. Dent Dig 1954;60:158–160. 17. Stedman’s Medical Dictionary, ed 26. Baltimore: Williams & Wilkins, 1995. 18. Cameron CE. Cracked-tooth syndrome. J Am Dent Assoc 1964; 68:405–411. 19. Ritchey B, Mendenhall R, Orban B. Pulpitis resulting from incomplete tooth fracture. Oral Surg Oral Med Oral Pathol 1957; 10:665–670. 20. Sutton PR. Greenstick fracture of the tooth crown. Br Dent J 1962;112:362– 366. 21. Cameron CE. The cracked tooth syndrome: Additional findings. J Am Dent Assoc 1976;93:971–975. 22. Caufield JB. Hairline tooth fracture: A clinical case report. J Am Dent Assoc 1981;102:501–502. 23. Luebke RG. Vertical crown-root fractures in posterior teeth. Dent Clin North Am 1984;28:883–895. 24. Kahler B, Moule A, Stenzel D. Bacterial contamination of cracks in symptomatic vital teeth. Aust Endod J 2000;26:115–118. 25. Brynjulfsen A, Fristad I, Grevstad T, Hals-Kvinnsland I. Incompletely fractured teeth associated with diffuse longstanding orofacial pain: Diagnosis and treatment outcome. Int Endod J 2002;35:461–466. 26. Walton RE, Leonard LA. Cracked tooth: An etiology for “idiopathic” internal resorption. J Endod 1986;12:167–169. 27. Bakland LK. Tooth infractions. In: Ingle JI, Bakland LK, Baumgartner JC (eds). Ingle’s Endodontics, ed 6. Hamilton, ON: BC Decker, 2008:660–675. 28. Krell KV, Rivera EM. A six year evaluation of cracked teeth diagnosed with reversible pulpitis: Treatment and prognosis. J Endod 2007;33:1405–1407. 29. Opdam NJ, Roeters JJ, Loomans BA, Bronkhorst EM. Seven-year clinical evaluation of painful cracked teeth restored with a direct composite restoration. J Endod 2008;34:808–811. 30. Fuss Z, Lustig J, Katz A, Tamse A. An evaluation of endodontically treated vertical root fractured teeth: Impact of operative procedures. J Endod 2001;27:46–48. 31. Tamse A. Vertical root fractures of endodontically treated teeth. In: Ingle JI,

Bakland LK, Baumgartner JC (eds). Ingle’s Endodontics, ed 6. Hamilton, ON: BC Decker, 2008:676–688. 32. Gher ME, Dunlap RM, Anderson MH, Huhl LV. Clinical survey of fractured teeth. J Am Dent Assoc 1987;117:174–177. 33. Bergman B, Lundquist P, Sjögren U, Sundquist G. Restorative and endodontic results after treatment with cast posts and cores. J Prosthet Dent 1989;61:10– 15. 34. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: A literature review. Part I. Success and failure data, treatment concepts. J Prosthodont 1994;3:243–250. 35. Torbjörner A, Karlsson S, Odman PA. Survival rate and failure characteristics for two post designs. J Prosthet Dent 1995;73: 439–444. 36. Fuss Z, Lustig J, Tamse A. Prevalence of vertical root fractures in extracted endodontically treated teeth. Int Endod J 1999;32:283–286. 37. Coppens CR, DeMoor RJ. Prevalence of vertical root fractures in extracted endodontically treated teeth [abstract]. Int Endod J 2003;36:926. 38. Meister F Jr, Lommel TJ, Gerstein H. Diagnosis and possible causes of vertical root fractures. Oral Surg Oral Med Oral Pathol 1980;49:243–253. 39. Tamse A. Iatrogenic vertical root fractures in endodontically treated teeth. Endod Dent Traumatol 1988;4:190–196. 40. Rud J, Omnell KA. Root fracture due to corrosion. Scand J Dent Res 1970;78:397–403. 41. Testori T, Badino M, Castagnola M. Vertical root fractures in endodontically treated teeth: A clinical survey of 36 cases. J Endod 1993;19:87–90. 42. Tamse A, Fuss Z, Lustig JP, Ganor Y, Kaffe I. Radiographic features of vertically fractured endodontically treated maxillary premolars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88:348–352. 43. Tamse A, Kaffe I, Lustig J, Ganor J, Fuss Z. Radiographic features of vertically fractured endodontically treated mesial roots of mandibular molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;101:797–802. 44. Langer B, Stein SD, Wagenberg B. An evaluation of root resections: A ten-year study. J Periodontol 1981;52:719–722. 45. Saunders WP, Saunders EM. Assessment of leakage in the restored pulp chamber of endodontically treated multirooted teeth. Int Endod J 1990;23:28– 33. 46. Saunders WP, Saunders EM. Coronal leakage as a cause of failure in root canal therapy: A review. Endod Dent Traumatol 1994;10:105–108. 47. Ray HA, Trope M. Periapical status of endodontically treated teeth in relation to the technical quality of the root filling and the coronal restoration. Int Endod

J 1995;28:12–18. 48. Seltzer S, Sinai I, August D. Periodontal effects of root perforations before and during endodontic procedures. J Dent Res 1970;49:109–114. 49. Simon JH, Dogan H, Ceresa LM, Silver GK. The radicular groove: Its potential clinical significance. J Endod 2000;26:295–298. 50. Andreasen JO, Bakland LK, Flores MT, Andreasen FM, Andersson L. Traumatic Dental Injuries: A Manual, ed 3. Chichester, England: WileyBlackwell, 2011. 51. Haapasalo M, Endal U. Internal inflammatory root resorption: The unknown resorption of the tooth. Endod Top 2006;14:60–79. 52. Malmgren B, Malmgren O, Andreasen JO. Alveolar bone development after decoronation of ankylosed teeth. Endod Top 2006;14:35–40. 53. Heithersay GS. Invasive cervical resorption following trauma. Aust Endod J 1999;25:79–85. 54. Rivera ME, Walton RE. Extensive idiopathic apical root resorption. A case report. Oral Surg Oral Med Oral Pathol 1994;78: 673–677.

Treatment Options and Materials for Endodontically Treated Teeth Various methods of restoring pulpless teeth have been reported for more than 200 years. The first authentic account of the use of artificial crowns and posts was given by Pierre Fauchard1 in 1728. The canal was filled with lead, a hole was drilled in the lead, and a post fabricated of gold or silver was held in the root canal space with a heat-softened adhesive called mastic.1, 2 The artificial crowns used were either natural crowns or crowns made of ivory. Through the years, other materials have been tried as a possible choice for the replacement of the missing crowns. Bone, ivory, animal teeth, and sound natural tooth crowns have been tried. Gradually the use of these natural substances declined, to be slowly replaced by porcelain. A pivot (what is today termed a post) was used to retain the artificial porcelain crown in a root canal, and the crown-post combination was termed a pivot crown. Porcelain pivot crowns were described in the early 1800s by a well-known dentist from Paris, Dubois de Chemant.2 Pivoting (posting) of artificial crowns to natural roots became the most common method of replacing crowns of natural teeth and was reported as the “best that can be employed” by Chapin Harris in The Dental Art in 1839.3 When first introduced, the pivot crowns used a hickory wood pin or pivot, one end of which fitted the post space and the other a hole in the center of the crown.4 Moisture would swell the wood and retain the pivot in place.2 It was found that, with time, the wooden pivot caused root decay, root fracture, and bad breath.

Surprisingly, Prothero 2 reported removing two central incisor crowns with wooden pivots that had been successfully used for 18 years. Subsequently, gold pivot crowns were fabricated using wood-metal combinations, and then more durable all-metal pivots were used. Metal pivot retention was achieved by various means such as threads, pins, surface roughening, and split designs that provided mechanical spring retention.2 Unfortunately, adequate cements, cements that would have enhanced post retention and decreased abrasion of the root caused by movement of metal posts within the canal, were not available to these early practitioners. Wood was used to hold the post in the crown, and the post was retained in the canal using fibers of cotton and silk or hickory wood. One of the best representations of a pivoted tooth appears in Dental Physiology and Surgery, written by Sir John Tomes in 1848. 5 The post length and diameter reported by Tomes conformed closely to today’s principles for post fabrication. Endodontic therapy by these dental pioneers embraced only minimal efforts to clean, shape, and obturate the canal. Frequent use of wooden posts in empty canals led to repeated episodes of swelling and pain. Wooden posts, however, did allow the escape of the so-called “morbid humors.” A groove in the post or root canal provided a pathway for continual suppuration from the periradicular tissues.1 Although many of the restorative techniques used today had their inception in the 1800s and early 1900s, proper endodontic treatment was neglected until years later. Today, the endodontic and prosthodontic aspects of treatment have advanced significantly, new materials and techniques have been developed, and a substantial body of scientific knowledge on which to base clinical treatment decisions is available.

Restoration Selection for Anterior Versus Posterior Pulpless Teeth A retrospective study6 of 1,273 teeth that had been endodontically treated 1 to 25 years previously compared the clinical success in anterior and posterior teeth. Endodontically treated teeth with restorations that encompassed the tooth (onlays, partial- or complete-coverage metal crowns, and metal-ceramic crowns) were compared with endodontically treated teeth without coronal-coverage restorations. It was determined that coronal-coverage crowns did not significantly improve the success of endodontically treated anterior teeth. This finding supports the use of a conservative restoration such as an etched resin in the access opening of otherwise

intact or minimally restored anterior teeth.6–8 Crowns are only indicated on endodontically treated anterior teeth when they are structurally weakened by the presence of large or multiple coronal restorations or when they require significant changes in form or color that cannot be effected by tooth whitening, resin bonding, or porcelain laminate veneers. Scurria et al9 collected data from 30 insurance carriers in 45 states regarding the procedures 654 general dentists performed on endodontically treated teeth. The data indicated that 67% of endodontically treated anterior teeth were restored without a crown, supporting the concept that many anterior teeth are being satisfactorily restored without the use of a crown. There is convincing evidence that coronal coverage increases the survival rate of endodontically treated posterior teeth.6–8, 10–17 When endodontically treated posterior teeth with and without coronal-coverage restorations were compared, a significant increase in the clinical success was noted when cuspal-coverage crowns were placed on maxillary and mandibular molars and premolars6, 15–17 (Fig 3-1). In a study of 116 failed and extracted endodontically treated teeth, Vire 11 reported that teeth restored with crowns had greater longevity than did those that were not. A strong association was found between crown placement and the survival of endodontically treated teeth. An analysis of data from multiple studies determined that endodontically treated teeth that were not restored with a crown following endodontic treatment were lost at a rate six times greater than teeth that were restored with a crown.13

Fig 3-1 (a) Buccal view of an endodontically treated mandibular left first molar without cuspal coverage reveals a dental fistula. (b) A narrow, isolated, deep periodontal pocket on the distal aspect of the molar is probed. (c) The extracted tooth shows a fractured cusp.

If long-term tooth survival is the primary goal, placement of a crown on an endodontically treated posterior tooth enhances survival and appears more important than the type of foundation restoration used.13 Therefore, restorations that encompass the cusps should be used on posterior teeth that have interdigitation with opposing teeth and thereby receive occlusal forces that push the cusps apart. The previously

discussed insurance data9 indicated that 37% to 40% of posterior pulpless teeth were restored without a crown, a method of treatment not supported by the long-term clinical prognosis of posterior endodontically treated teeth that do not have cuspencompassing crowns. There are, however, certain posterior teeth (not as high as 40%) that do not have substantive occlusal interdigitation or have an occlusal form that precludes interdigitation of a nature that attempts to separate the cusps (such as mandibular first premolars with small, poorly developed lingual cusps). When these teeth are intact or minimally restored (small mesio-occlusal or disto-occlusal restorations), they would be reasonable candidates for restoration of only the access opening without use of a coronal-coverage crown.18 In contrast to the aforementioned recommendations, a 3-year clinical study by Mannocci et al19 evaluated the clinical success rate of endodontically treated premolars restored with a post and direct composite resin restorations with and without complete crown coverage. They found that both had a similar success rate. Nagasiri et al,20 in a retrospective cohort study, indicated that endodontically treated molars that are completely intact except for a conservative access opening could be restored successfully with composite resin restorations. Hannig et al21 evaluated the fracture resistance of endodon tically treated maxillary premolars restored with computer-aided design/computer-assisted manufacture ceramic mesio-occlusodistal inlays. The researchers found that endodontically treated teeth restored with CEREC inlays (Sirona) displayed a significantly higher number of severe fractures than did controls (sound premolars with no fillings or decay). They concluded that restoring endodontically treated teeth with CEREC inlays did not reestablish the fracture resistance of endodontically treated maxillary premolars to their original level. On the other hand, when comparing the fracture resistance of extensive direct and indirect composite resin restorations in endodontically treated molars, Plotino et al22 concluded that cusp-replacing direct and indirect composite resin restorations presented similar resistance to fracture under simulated occlusal loads and may be a viable treatment option for endodontically treated molars with a guarded prognosis. Multiple clinical studies of fixed partial dentures (FPDs), many with long spans and cantilevers, have determined that endodontically treated abutments failed more often than vital teeth due to tooth fracture,23–28 supporting the idea that endodontically treated teeth are more fragile and indicating the need to design restorations that reduce the potential for both crown and root fractures when extensive fixed prosthodontic treatment is required. Many studies comparing the different physical properties of vital and nonvital

teeth have been published with different results. Gutmann29 reviewed the literature and presented an overview of several studies that have identified what happens when teeth are endodontically treated. Endodontically treated dog teeth were found to have 9% less moisture than vital teeth.30 However, other studies found that dehydration increases stiffness and decreases the flexibility of both vital and nonvital teeth. However, dehydration by itself does not account for the changes of physical properties in dentin.31 In contrast, Papa et al32 found that there was no significant difference in moisture content of human endodontically treated teeth when compared with contralateral vital teeth. Also, with aging, greater amounts of peritubular dentin are formed, decreasing the amount of organic materials that may contain moisture. It has been shown that endodontic procedures alone reduce tooth stiffness by 5%, attributed primarily to the access opening.33 Tidmarsh34 and Grimaldi35 described a direct relationship between tooth structure removal and tooth deformation under load. Other studies36–38 concluded that the bigger the cavity preparation, the greater the deflection between the cusps. Dentin from endodontically treated teeth has been shown to exhibit significantly lower shear strength and toughness than vital dentin,39 while other studies reported that dentin strength was not decreased.40, 41 Rivera et al42 stated that the effort required to fracture dentin may be less when teeth are endodontically treated because of more immature (potentially weaker) collagen intermolecular crosslinks. Another study found that collagen fibrils degraded over time in teeth with zinc phosphate–cemented posts. Acid demineralization can also result from bacteria and acid etching.43

Purpose of a Post for Pulpless Teeth Historically, the use of posts was based on the concept that a post reinforces the tooth. Virtually all laboratory studies 44–54 have shown that placement of a post and core either fails to increase the fracture resistance of endodontically treated extracted teeth or decreases the fracture resistance of the tooth when a force is applied via a mechanical testing machine. Lovdahl and Nicholls44 found that endodontically treated maxillary central incisors were stronger when the natural crown was intact except for the access opening than when they were restored with cast posts and cores or pin-retained amalgam restorations. Lu45 found that posts placed in intact endodontically treated central incisors did not lead to an increase in the force required to fracture the tooth or a change in the position and angulation of

the fracture line. Pontius and Hutter46 found that maxillary incisors without posts resisted higher failure loads than the other groups with posts and crowns. Gluskin et al47 found that mandibular incisors with intact natural crowns exhibited greater resistance to transverse loads than teeth with posts and cores. McDonald et al48 found no difference in the impact fracture resistance of mandibular incisors with or without posts. Eshelman and Sayegh49 reported similar results when posts were placed in extracted dog lateral incisors. Guzy and Nicholls50 determined that no significant reinforcement was achieved when a post was cemented in an endodontically treated tooth that was intact except for the access opening. Leary et al51 measured the root deflection of endodontically treated teeth before and after posts of various lengths were cemented in prepared root canals. They found no significant differences in strength between the teeth with a post and those without a post. Trope et al 52 determined that endodontically treated teeth prepared with a post space were weaker than those in which only an access opening, but no post space, was made. A potential situation where a post and core could strengthen a tooth was identified by Hunter et al,53 using photoelastic stress analysis. They determined that removal of internal tooth structure during endodontic therapy is accompanied by a proportional increase in stress. They also determined that minimal root canal enlargement for a post does not substantially weaken a tooth, but when excessive root canal enlargement has occurred, a post strengthens the tooth. Therefore, if the walls of a root canal are thin due to removal of internal root caries or overinstrumentation during post preparation, a post may strengthen the tooth. Two-dimensional finite-element analysis was used in one study54 to determine the effect of posts on dentin stress in pulpless teeth. When loaded vertically along the long axis, a post reduced maximal dentin stress by as much as 20%. However, only a small (3% to 8%) decrease in dentin stress was found when a tooth with a post was subjected to masticatory and traumatic loadings directed 45 degrees to the incisal edge. The authors concluded that the reinforcement effect of posts in anterior teeth is doubtful because they are subjected to angular forces. Not only laboratory tests but also clinical data fail to support the perception that posts enhance the survival of teeth. Sorensen and Martinoff55 clinically evaluated endodontically treated teeth with and without posts and cores. Some of the teeth were restored with single crowns while others served as FPD abutments or removable partial denture abutments. Posts and cores significantly decreased the clinical survival rate of teeth with single crowns, improved the clinical survival of removable partial denture abutment teeth, and had little influence on the clinical survival of FPD abutments.

Eckerbom and colleagues56 examined the radiographs of 200 consecutive patients and reexamined the patients radiographically 5 to 7 years later to determine the prevalence of apical periodontitis. Of the 636 endodontically treated teeth evaluated, 378 had posts, and 258 did not have posts. At both examinations, apical periodontitis was significantly more common in teeth with posts than in endodontically treated teeth without posts. Morfis57 evaluated the incidence of vertical root fracture in 460 endodontically treated teeth, 266 of which had posts. There were a total of 17 teeth with root fracture after a time period of at least 3 years. Nine of the 17 fractured teeth had posts, and 8 root fractures occurred in teeth with no posts. Morfis57 concluded that the endodontic technique could cause vertical root fracture. In an analysis of data from multiple clinical studies, Goodacre et al58 found that 3% of teeth with posts fractured. None of these clinical data provides definitive support for the concept that posts and cores strengthen endodontically treated teeth or improve their long-term prognosis. Because clinical and laboratory data indicate that teeth are not strengthened by posts, their purpose is to ensure retention of a core that will provide appropriate support for the definitive crown or prosthesis. Unfortunately, this primary purpose has not been completely recognized. Hussey and Killough59 noted that 24% of general dental practitioners believed that a post strengthens teeth. A 1994 survey60 (with responses from 1,066 practitioners and educators) revealed some interesting opinions. For example, 10% of the dentist respondents believed that every endodontically treated tooth should receive a post. It was determined that 62% of dentists older than 50 years believed that a post reinforces the tooth, whereas only 41% of the dentists younger than 41 years believed that concept. In addition, 39% of part-time faculty, 41% of full-time faculty, and 56% of nonfaculty practitioners believed that posts reinforce teeth.60 To reiterate, both laboratory and clinical data fail to provide definitive support for the concept that posts strengthen endodontically treated teeth. Therefore, the purpose of a post is to provide retention for a core.

Types of Posts and Cores Custom cast posts and cores Alloys A logical evolution from the Richmond crown (crown and post are made in one

piece) was the introduction of cast posts and cores. For many years, custom cast posts and cores have been considered to be the standard of care when endodontically treated teeth are restored, have been described as the treatment of choice, and have historically been made of metal. The simplest method for the fabrication of a post and core was direct fabrication using the lost-wax technique (Fig 3-2).

Fig 3-2 A cast post and core has been fabricated with the lost-wax technique.

Traditionally, gold alloy similar to the alloys used for complete crowns was used. However, silver-palladium and base metal alloys have been suggested as alternative alloys for cast posts and cores and are the most commonly used metals.61– 74 The hardness, the unstable chemical structure, and the manipulation of base metal alloys have been considered major disadvantages.75, 76 The degradation of base metal alloys releases substances that could be harmful to the patient.76–78 Other alloys were later introduced to overcome the problems of contouring and finishing posts and cores fabricated from base metal alloys. Silver-palladium alloys were introduced as a replacement for gold and base metal alloys. They are easier to adjust chairside and demonstrate acceptable casting accuracies, properties similar to those of gold casting alloys.79–81 Cast metal posts and cores are fabricated either directly or indirectly. Either a resin pattern of the post and core is made directly in the prepared tooth, or a final impression of the canal space and residual coronal tooth structure can be made so

that a wax pattern can be made indirectly on a gypsum cast. The wax pattern is invested and cast in a dental casting alloy with physical properties equal to or greater than those of a type IV gold alloy. Indications Custom cast metal posts can be used effectively in any location, but they are especially well suited for teeth with root dimensions and internal morphology such that additional preparation of the canal space for a prefabricated post is not advisable (eg, mandibular incisors). The clinical time required to make a cast post and core, the need for an additional appointment with the patient, the sometimes difficult provisionalization of the tooth, and the higher cost have made the prefabricated post a popular choice among practitioners for the restoration of endodontically treated teeth. A cast post and core will be needed in clinical situations (eg, anterior maxillary teeth) where it is necessary to alter the angle of the core in relation to the root. There is a limit to how much a metallic post can bend and how much buildup material a post can retain. Direct fabrication technique Cast posts and cores can be fabricated in the patient’s mouth using a direct technique; several methods have been described for the intraoral fabrication of an acrylic resin pattern for a direct post and core.64, 82–85 Prefabricated plastic patterns are commonly used and relined with autopolymerizing acrylic resin to fit the post space (Fig 3-3a). The coronal adaptation of the tooth is usually completed with the same resin, and the core is contoured intraorally to the desired form. The only disadvantage of this direct technique is the amount of chairside time required to fabricate the pattern intraorally. It also requires a second visit for the fitting and cementation of the cast post and core. Step-by-step fabrication of a direct resin pattern 1. Remove the root canal filling material to the required depth and diameter. It is neither necessary nor desirable to make the post space round. 2. Because most custom cast posts and cores will possess a slightly tapered form, prepare a flat area in remaining coronal tooth structure if one is not already present in the existing morphology. This flat area (formed perpendicular to the long axis of the post) will serve as a positive stop during cementation of the post and during subsequent application of occlusal forces, thereby helping to

minimize any tendency for the post to wedge against the tooth. 3. Select a 14-gauge solid plastic post that fits within the confines of the post preparation without binding (see Fig 3-3a). Leave the post sufficiently long that it can be easily gripped. 4. Lightly lubricate the canal with the patient’s saliva, anesthetic solution, or water. (If you use a water-soluble lubricant such as die lubricant, ensure that all lubricant can be subsequently removed so that it does not interfere with cement retention). 5. Create notches in the side of a plastic post pattern if the post is smooth and seat it to the depth of the prepared canal. 6. Use the bead-brush technique to apply pattern resin to the prepared canal as well as the body of the plastic post (Figs 3-3b to 3-3d). Seat the post to the full depth of the canal. 7. Do not allow the resin to completely harden within the canal. Wait for 30 to 45 seconds and then remove and reseat the post and attached resin several times while the resin is still in its rubbery stage so that the pattern does not inadvertently become locked into the canal. 8. Remove the polymerized pattern and inspect the resin for integrity and lack of voids. Reseat the post and test for adaptation and passivity (Fig 3-3e). 9. Add additional coronal resin to form the desired dimensions of the core (Fig 33f). Remove and reseat the pattern as previously described to prevent it from becoming locked into coronal tooth structure. Add a slight excess of core resin so that the hardened core can be prepared with a high-speed diamond and water spray to resemble a complete-crown tooth preparation (Figs 3-3g and 3-3h). Verify core reduction using a vacuum-formed template fabricated from the diagnostic wax pattern. 10. Remove the resin pattern post and core (Fig 3-3i) and then invest and cast it. 11. Try in the post and core and adjust it as necessary, then cement it. The definitive tooth preparation can then be completed.

Fig 3-3 (a) Prefabricated plastic patterns are commonly used for the direct technique of intraoral fabrication of an acrylic resin pattern for a cast post and core. (b and c) Monomer is applied to the body of the plastic post. (d) The bead-brush technique is used to apply resin to the body of the post. (e) The polymerized pattern is removed from the post space and inspected for integrity and lack of voids. (f) Coronal resin is added to form the desired dimensions of the core. (g) The resin is prepared with a high-speed diamond and water spray to resemble a complete-crown preparation. (h) Core reduction is verified with a vacuum-formed template fabricated from the diagnostic wax pattern. (i) The resin pattern post and core is removed and sent to the laboratory for investing and casting.

Indirect fabrication technique As an alternative, an indirect technique for fabrication of cast posts and cores has

been proposed.86–88 The indirect technique is used to fabricate more than three cast posts in one visit and when access is problematic for direct fabrication. The post spaces are prepared to the desired depth, and the final tooth preparations are completed with finish lines located at the desired location. This allows the dentist to conserve a lot of chair time by delegating the task of fabrication of the pattern to a dental technician. However, this procedure requires meticulous attention to a defined protocol to ensure success. The success of this technique depends on the accuracy of the impression in replicating the internal aspect of the post space and the skills of the dental technician. An elastomeric nonaqueous impression material is used to make an accurate impression of the prepared root canal. The impression material must be supported, and its distortion through bending or elongation must be prevented during removal of the impression. Several materials, such as orthodontic wire, safety pins, paper clips, or plastic pins,72, 73 have been proposed to make the impression technique easier. Prefabricated plastic dowels were introduced to facilitate the indirect fabrication technique. Metal wire such as a paper clip can be flexed on impression removal and will be permanently bent and distorted. Plastic posts can also be used to support the impression material. However, they can be flexed in slightly curved canals or if they contact coronal tooth structure. Subsequent removal of the post after the impression material sets allows the plastic post to straighten, resulting in distortion. Plastic posts should only be used when they are totally passive and do not bind on any tooth structure. Step-by-step fabrication of an indirect resin pattern 1. Select an orthodontic wire or a prefabricated plastic pin as a means of supporting the impression material. The coronal portion of the wire should be bent to form a handle and to help retain it in the impression material (Figs 3-4a and 3-4b), while the coronal portion of the plastic post should be flattened to resemble a nail head (Figs 3-4c and 3-4d). 2. If you are using a wire, notch it and coat it with adhesive (Fig 3-4e). 3. Fill the prepared canal with impression material using a slowly rotating spiral instrument accompanied by an up-and-down motion. 4. Alternatively, place an anesthetic needle to the depth of the post space (to serve as an air escape channel) and syringe impression material down the canal (Fig 34f). 5. Seat the wire or plastic post through the impression material to the full depth of the canal, syringe additional impression material around the supporting device as

well as the prepared tooth, and seat the impression tray. 6. Remove the impression (Figs 3-4g and 3-4h), evaluate it, and pour a cast. On removal of the impression from the mouth, verify the presence of the supportive pin at the apical extension of the impression material, which indicates that there was no elongation of the impression material on removal. 7. Make an interocclusal record and obtain an opposing cast and appropriately sized plastic post to be used in forming a wax pattern. Send the impression to the laboratory so that a wax pattern can be made indirectly on a gypsum cast, invested, and cast in a dental casting alloy. 8. Lightly lubricate the canal of the working cast with die lubricant. 9. Place notches on the side of a plastic post and seat it to the full depth of the canal preparation. 10. Apply a very thin layer of sticky wax to the plastic post and then add soft inlay wax in small increments, fully seating the plastic post after each increment of wax is added. 11. Ensure that the pattern is well adapted but passive. 12. After the post pattern has been fabricated, add the wax core, shape it, and then cast the pattern in metal. 13. Cement the cast post and core in the tooth and complete the definitive tooth preparation.

Fig 3-4 (a) Orthodontic wire is selected as a support for the impression material. (b) The coronal portion of the wire is bent to form a handle. (c) A prefabricated plastic post is selected as support for the impression material. (d) The coronal portion of the plastic pin is transformed to resemble a nail head. (e) Orthodontic wire is notched and coated with adhesive. (f) An anesthetic needle is placed to the depth of the post space to serve as an air escape channel during the injection of the impression material. (g) The supportive pin is located at the apical extension of the impression material in the final impression. (h) The definitive cast is poured.

Step-by step fabrication of cast posts and cores for posterior teeth with divergent roots. In this technique, a post of optimal length is inserted in the most accessible canal and a key-lock post is extended partially into less accessible canals. 1. Determine radiographically the appropriate depth of the post space required (Figs 3-5a and 3-5b). 2. Remove the gutta-percha to the desired depth in the roots to be used. 3. Using the appropriately sized shaping drill, prepare one of the canals to receive a prefabricated metal post (ParaPost, Coltène/Whaledent) (Fig 3-5c). The ParaPost drills can be used either manually with a universal hand driver or in a low-speed contra-angle handpiece. Use a continuous clockwise rotation during the entire drilling procedure with an up-and-down motion. 4. Select a ParaPost plastic impression post of the same color as the last drill used and adapt it in the post space. Adjust the length of the post to be 1 mm short of the opposing teeth in occlusion. Remove the post from the mouth and press a hot instrument on the head of the post, thereby creating a “nail head” that will help in the retention of the post in the impression material. 5. Make a final impression as described previously in the section on fabrication of an indirect resin pattern. 6. After pouring the cast, select a preformed castable plastic ParaPost to match the color of the plastic impression post. Adapt the height of the castable plastic ParaPost by cutting off the tip. Lubricate an aluminum ParaPost and fit it in the divergent canal. 7. Form an optimally contoured core by adding wax. Wax should flow only around the orifice of the canal; no wax should reline the preformed castable post. Post serrations and the cement escape channel must be preserved. When the wax cools, remove the aluminum ParaPost from the wax (Figs 3-5d and 3-5e). 8. Cast, finish, and seat the core on the die (Fig 3-5f). 9. Seat and cement the cast post and core on the tooth preparation and complete the restoration (Figs 3-5g to 3-5i).

Fig 3-5 (a)A preoperative radiograph of a mandibular left first molar reveals short posts and an apical lesion. (b) Postoperative radiograph after endodontic treatment. (c) The ParaPost kit contains color-coded drills, plastic impression posts, aluminum posts, and burnout casting posts. (d) The wax pattern of the cast post and core is in place on the trimmed die. Note the orifice of the divergent post canal, created by a red No. 5 ParaPost plastic impression post. (e) Mesial view of the die with the cast post and core pattern in place. Note the position of the aluminum post that was used to create the channel for the final divergent post in the wax pattern. Also note the amount of tooth structure left on the tooth preparation apical to the cast core to fulfill the requirements of the ferrule effect. (f) The cast post and core is shown with the prefabricated post through the casting. (g) The cast post and core is seated on the tooth preparation with the final divergent post in place. (h) A periapical radiograph, showing the seated cast post and core and metal-ceramic crown before cementation, is used to check the marginal fit and emergence profile of the restoration. (i) Final restoration. (Courtesy of Dr Tony Daher, La Verne, CA.)

Prefabricated posts Prefabricated posts have become quite popular, and a wide variety of systems are available: parallel-sided or tapered, smooth or serrated, passive (cemented/bonded) or active (threaded), or combinations of these.89–91 Threaded posts depend primarily on engaging the tooth—either through threads formed in the dentin as the post is screwed into the root or through threads previously prepared in the dentin. The

majority of these posts are metallic. Prefabricated posts typically are made either of an 18-8 stainless steel (18% chromium and 8% nickel) alloy or a titanium alloy, such as Ti6Al4V, containing 6% aluminum and 4% vanadium. Recently, in response to a need for tooth-colored posts, several nonmetallic posts such as carbon fiber–reinforced (CFR) epoxy resin, zirconia, glass fiber– reinforced (GFR) epoxy resin, and ultrahigh polyethylene fiber–reinforced (PFR) posts have become available. Carbon fiber–reinforced epoxy resin posts Composition and properties. The CFR epoxy resin post system was developed in France in 1988 by Duret et al92–94 and first introduced in Europe in the early 1990s.95–97 The matrix for this post is an epoxy resin reinforced with unidirectional carbon fibers parallel to the long axis of the post. The fibers are 8 μm in diameter and uniformly embedded in the epoxy resin matrix. By weight, the fibers constitute 64% of the post and are stretched before injection of the resin matrix to maximize the physical properties of the post92, 98, 99 (Fig 3-6).

Fig 3-6 Surface texture of a CFR epoxy resin post (original magnifi cation ×250).

The post is reported to absorb applied stresses and distribute these stresses along the entire post channel.100 The bulk of the carbon fibers is made from polyacrylonitrile, which is heated in air at 200°C to 250°C and then in an inert atmosphere at 1,200°C. This process removes hydrogen, nitrogen, and oxygen, leaving a chain of carbon atoms and forming carbon fibers.101 The CFR post has

been reported to exhibit high fatigue strength, high tensile strength, and a modulus of elasticity similar to that of dentin.95, 98, 102–105 The post was originally radiolucent; however, a radiopaque post is now available. Radiopacity is produced by placing traces of barium sulfate and/or silicate inside the post. Mannocci et al106 examined five different types of fiber posts radiographically. They found that only Composiposts (RTD) and Snowposts (Carbotech) had uniform radiopacity. Finger et al 107 examined the radiopacity of seven fiber-reinforced resin posts and compared them to a titanium post. They found that CFR posts had an acceptable radiopacity compared with other posts. The posts are available in different shapes: double cylindrical with conical stabilization ledges or conical shapes (Fig 3-7). The surface texture of the post may be smooth or serrated. Studies have indicated that serrations increase mechanical retention, although the smooth posts also bond well to adhesive dental resin.104, 108 The post has a surface roughness of 5 to 10 μm to enhance mechanical adhesion of the autopolymerizing luting material, and the post appears to be biocompatible based on cytotoxicity tests.103, 109

Fig 3-7 Available shapes of CFR epoxy resin posts.

Should fracture of CFR posts occur, a potential advantage is their purported ease of removal from the post space compared with metal posts.110–115 A removal kit has been suggested111–114 for CFR post removal, with the recommendation that it be a single-use item.115

Laboratory test results. Tests of the physical properties of CFR posts have produced contrasting results. Several studies99, 102, 116, 117 have indicated that CFR posts exhibit adequate physical properties compared with metal posts. In a retrospective study over 4 years, Ferrari et al116 indicated that the Composipost system was superior to the conventional cast post and core system. King and Setchell102 and Duret et al99 evaluated the physical properties (fracture resistance and modulus of elasticity) of CFR posts, and both groups reported that these posts are stronger than prefabricated metal posts. Contrasting results were reported by Sidoli et al118 in an in vitro study. They found that CFR posts exhibited inferior strength compared with metallic posts. Similar results were also obtained by Purton and Love119 and Asmussen et al.120 Martinez-Insua et al121 studied the fracture resistance of teeth restored with CFR posts and cast posts. They reported a significantly higher fracture threshold for cast posts and cores. A clinical evaluation 122 of CFR posts suggested that these posts did not perform as well as conventional cast posts and cores. However, the results of this study must be interpreted with care because of the relatively small sample size (27 teeth). Multiple studies123–126 have indicated that the strength of CFR posts decreases after thermocycling and cyclic loading. In addition, contact of the post with oral fluids reduces their flexural strength values.109, 126, 127 In two in vitro studies,128, 129 results showed no significant differences among CFR posts, cast posts and cores, and metal posts when mandibular incisor teeth were restored. No differences were noted in the mode or state of fracture observed. According to one study, surface treatment of the post with airborne-particle abrasion does not influence the mechanical properties of the CFR post.130 In contrast, another study showed that it improves the retention of cement to the CFR post.131 More recent studies have indicated that the use of silane without airborne-particle abrasion was more than enough treatment to improve the retention of the cemented CFR post.130, 132 Multiple studies99, 110, 118, 121, 133–137 have shown that CFR posts are less likely to cause fracture of the root at failure. The mode of failure of teeth restored with CFR posts in these studies was more favorable to the remaining tooth structure. However, despite all these advantageous properties, certain in vivo applications of the CFR post are questionable. When the ferrule is small or absent in an endodontically treated tooth restored with a CFR post, loads may cause the post to flex, causing a micromovement of the entire core. The cement seal at the margin of the crown can be compromised, accompanied by microleakage of oral bacteria and fluids. As a result, secondary caries may develop in the space and may not be easily

detected.137 Clinical outcomes. A review of the literature 138 of nonmetallic prefabricated posts identified 12 studies that have clinically evaluated CFR posts; a wide range of failure percentages have been reported (Table 3-1). Failure rates have ranged from 0% after a mean postplacement time of 2.7 years139 to a high of 35% after a mean postplacement time of 6.7 years.144 The reported causes of failure have included post debonding, periapical pathosis, root fracture, crown debonding, secondary caries, periodontitis, post fracture, tooth extraction for unspecified reasons, and unknown diagnoses (see Table 3-1).

Glass fiber–reinforced epoxy resin posts Composition and properties. The GFR epoxy resin post is made of glass or silica fibers (white or translucent) (Fig 3-8). Glass fiber posts can be made of different types of glasses: electrical glass, high-strength glass, or quartz fibers.126, 146 The commonly used fibers are silica based (50% to 70% silicon dioxide), in addition to other oxides.147

Fig 3-8 Surface texture of a GFR epoxy resin post (original magnification ×62). (Courtesy of Dr Fahad Al-Harbi, Alkhobar, Saudi Arabia.)

The GFR post is available in different shapes: cylindric, cylindroconical, or conical (Fig 3-9). An in vitro assessment of several GFR post systems indicated that parallel-sided GFR posts are more retentive than tapered GFR posts.148

Fig 3-9 Available shapes of GFR epoxy resin posts.

The composition of the glass fibers in the matrix tends to play an important role in the strength of the post. Newman et al125 compared the fracture resistance of two GFR posts containing different weight percentages of glass fibers. They found that the higher content of glass fibers in the post contributed to the greater strength displayed by the tested post. Laboratory test results. The GFR post has been reported to exhibit high fatigue strength, high tensile strength, and a modulus of elasticity closer to dentin than that of CFR posts.105, 120, 149 The GFR post is as strong as the CFR post and approximately twice as rigid.150 The flexural strength of GFR posts is not related to the type of glass fiber used. Galhano et al105 evaluated the flexural strength of carbon fiber, quartz fiber, and glass fiber posts. They found that the posts behaved similarly because the same concentration and type of the epoxy resin were used to join the fibers together. Pfeiffer at al151 evaluated, in vitro, the yield strength of GFR, titanium, and zirconia posts. They found that the yield strength was significantly higher for the zirconia and titanium posts than for GFR posts. Several studies123, 126, 152–154 have determined that there is a decrease (about 40%) in the strength of GFR posts after thermocycling and cyclic loading. In addition, contact of the posts with oral fluids (short- and long-term contact) reduced their flexural strength. Two studies 155, 156 have indicated that the tensile bond strength developed between the composite resin core material and the GFR post is weaker than that developed between composite resin and a titanium post. Other studies,155, 157, 158 however, have indicated there was a good adhesive bond between the GFR post and composite resin cements. The bonding of the core to the post can be improved by

treating the post with airborne-particle abrasion.131, 159 Similar results were obtained when the surface of the post was treated with hydrogen peroxide and silane130, 160, 161 or hydrofluoric acid and silane.162, 163 During fatigue loading, a composite resin core bonded to a GFR post provided significantly stronger crown retention than cast gold posts and cores and titanium posts with composite resin cores.164 Similarly to CFR posts, GFR posts have been found, in multiple studies,125, 165–171 to be less likely to cause fracture of the root at failure. The mode of failure of teeth restored with GFR posts in these studies was more favorable to the remaining tooth structure. However, several studies 133, 172–176 have discussed the importance of the presence of a ferrule effect in achieving a high success rate. A clinical study of 154 glass fiber posts after a mean time of 42 months compared the number of preserved coronal walls in endodontically treated premolars.176 The survival rate was higher for teeth where three or four coronal walls of tooth structure were present before the core buildup, demonstrating the importance of a crown ferrule.176 Malferrari et al168 restored 180 teeth with GFR posts and reported no post, core, or root fractures after 30 months of service. Naumann et al177 found that the survival rates of parallel-sided and tapered GFR posts were similar. Clinical outcomes. A review of the literature 138 of nonmetallic prefabricated posts identified eight studies that have clinically evaluated GFR posts; a wide range of failure percentages have been reported (Table 3-2). Reported failure rates ranged from 0% after a mean postplacement time of 2.3 years180 to a high of 11.4% after 1 to 2 years.177 The causes of failure reported in these studies included post debonding, periapical pathosis, root fracture, crown debonding, post fracture, core failure, restoration fracture, and unspecified reasons (see Table 3-2).

Polyethylene fiber–reinforced posts Composition, properties, and laboratory test results. PFR posts are made of ultrahigh–molecular weight polyethylene woven fiber ribbon (Ribbond, Ribbond) (Fig 3-10). It is not a post and core in the traditional sense. It is a polyethylene woven fiber ribbon that is coated with a dentin bonding agent and packed in the canal, where it is then light polymerized in position.181–183 The Ribbond material has a three-dimensional structure that results from either a leno weave (“gauze weave”) or a triaxial architectural design. These designs are composed of a great number of nodal intersections that prevent crack propagation and provide mechanical retention for the composite resin cement.

Fig 3-10 Close-up of PFR post material in its original package.

When PFR posts were compared with metal posts in the laboratory, the fiberreinforced posts reduced the incidence of vertical root fracture. The addition of a small prefabricated post to the PFR post increased the strength of the post and core complex. However, the strength of the PFR post did not approach that of a cast metal post and core.181 When compared with other fiber-reinforced composite post systems, PFR posts were also found to protect the remaining tooth structure.125 These results may be attributed to the manufacturer’s recommendations not to enlarge the root canals, not to remove undercuts present in the root canal, and to form a 1.5- to 2.0-mm crown ferrule. The presence of a large volume of core material and a sufficient dentin bonding area coronally seems to greatly affect the mean load-to-failure value of PFR posts.125 Eskitascioglu et al184 evaluated two post and core systems using a fracture strength test and a finite-element analysis. They found that stress accumulated along the cervical region of the tooth and along the buccal bone. Minimum stress was recorded within the PFR post system. They suggested that the PFR post could be advantageous for the restoration of teeth with apical resection. Contrasting results were obtained by Kivanç et al185 when they restored endodontically treated maxillary premolars with GFR, PFR, or titanium posts. They found that the presence and type of posts did not influence the fracture load or the failure mode. Newman et al125 compared the effect of three fiberreinforced composite post

systems on the fracture resistance of endodontically treated teeth. They found that when PFR posts were placed in narrow canals, they performed better than GFR posts. They suggested that the PFR post be formed to the shape of the canal. The use of PFR posts to restore endodontically treated teeth appears to be a promising alternative to the stainless steel and zirconia dowel posts with respect to microleakage.186 Usumez et al186 compared in vitro the microleakage of three esthetic, adhesively luted dowel systems with that of a conventional dowel system. They found that the PFR posts and the GFR posts exhibited less microleakage than did zirconia posts. However, when comparing the fracture strength of metallic posts to that of GFR and PFR posts, Ozcan and Valandro 187 found that post loosening was the only cause of failure for PFR posts and that the failure type for PFR posts was less favorable compared with that of GFR or metallic posts. Clinical outcomes. Two studies188, 189 have clinically evaluated PFR dowels. Turker et al188 reported the failure rate to be 2.4% after a mean time of 2.9 years. In their study, 1 of 42 dowels loosened. Dowel loosening was reported to be the only cause of failure of the PFR dowel. Piovesan et al189 reported data on post fractures. They found that 2 of 36 posts fractured in anterior teeth, and 2 of 73 posts fractured in posterior teeth. Zirconia posts Composition and properties. The trend toward the use of all-ceramic crowns has encouraged manufacturers to explore the development of all-ceramic posts.190–193 A metal-free post avoids the discoloration of tooth structure that can occur with metal posts and produces optical properties comparable to those of all-ceramic crowns.193–197 One type of all-ceramic post is the zirconia post, composed of zirconium oxide (ZrO2), an inert material used for a range of applications. Its high fracture toughness, high flexural strength, and excellent resistance to corrosion encouraged orthopedists to use it at articulation surfaces198 (Fig 3-11). Studies have suggested that zirconia specimens transplanted in animals are very stable after longterm aging, and there is no apparent degradation of the specimens.198–202

Fig 3-11 Available shapes of zirconia posts.

Zirconia (tetragonal zirconium polycrystals [TZP]) exhibits phase transformation. Low-temperature degradation of TZP is known to occur as a result of spontaneous phase transformation of tetragonal zirconia to monoclinic phase during aging at 130°C to 300°C, possibly within a water environment. It has been reported that this degradation leads to a decrease in strength due to the formation of microcracks during the phase transformation. To inhibit this phase transformation, certain oxides (magnesium, yttrium, or calcium oxide) are added to fully or partially stabilize the tetragonal phase of zirconia at room temperature. This mechanism is known as transformation toughening. 193, 199, 203–205 The type of zirconia used for dental posts is composed of TZP with 3% mol yttrium oxide (Y2O3) and is called yttriumstabilized tetragonal polycrystalline zirconia (YTZP).193, 206 μm average diameter) that provides the post with toughness and a smooth surface204, 206, 207 (Fig 3-12).

Fig 3-12 Surface texture of a zirconia post (original magnification ×250).

The post is extremely radiopaque (Fig 3-13) and biocompatible, possesses high flexural strength and fracture toughness, and may act similar to steel.120, 199–203, 208–216 In addition, the post has a low solubility213 and is not affected by thermocycling.123 The post is available in a cylindroconical shape.

Fig 3-13 Radiograph showing the difference in radiopacity between a zirconia post (bottom) and a CFR epoxy resin post (top).

Laboratory test results. The zirconia post has a smooth surface configuration with no grooves, serrations, or roughness to enhance mechanical retention. As a result, the zirconia post does not bond well to composite resins and may not provide the best support for a brittle all-ceramic crown.165, 217–220 Dietschi et al219 found that these posts also have poor resin bonding capabilities to dentin after dynamic loading and

thermocycling due to the rigidity of the post. In a cyclic loading test performed in a wet environment, Mannocci et al135 found that the survival rate of zirconia posts was significantly lower than that of fiber posts. In vitro studies155, 158, 220, 221 have indicated that the smooth surface configuration of untreated zirconia posts leads to failure at the cement-post interface. The vast majority of the cement remained in the root and was not attached to the zirconia dowels. Wegner and Kern 222 evaluated the bond strength of composite resin cement to zirconia posts. They found that the long-term bond strength of the composite resin cement to zirconia posts is weak. Several studies222–225 found that acid etching and silanization of zirconia posts does not improve the strength of the resin bond to the zirconia-based material because there is little or no silica content in the post. However, tribochemical silica coating was found to increase the bond strength of composite resin to the zirconia post.226, 227 Oblak et al228 compared the fracture resistance of prefabricated zirconia posts after different surface treatments. They found that airborne-particle–abraded posts exhibited significantly higher resistance to fracture than did posts that had been ground with a diamond instrument. The use of heat-pressed glass to form the core instead of composite resin has been suggested.211, 212, 229 This approach may improve the physical properties of the allceramic post and core. When the mechanical properties of zirconia posts were evaluated, it was reported that these posts are very stiff and strong, with no plastic behavior. 120, 210, 211 Pfeiffer et al151 found that the zirconia post had a significantly higher yield strength than did titanium and GFR posts. Several studies110, 209, 230, 231 have indicated that many commonly used posts exhibit higher fracture resistance than zirconia posts. In addition, once zirconia posts fracture, the irretrievable posts will leave unrestorable roots.133, 231 Clinical outcomes. Two studies 232, 233 have clinically evaluated zirconia dowels. One study reported no failures after a mean time of 2.4 years.232 In the other study, the failure rate was reported to be 9% after a mean time of 4.8 years. Dowel loosening was reported to be the only cause of failure of the zirconia dowel.233 Step-by-step cementation or bonding of a prefabricated post 1. Remove the root canal filling material (Fig 3-14a) using a warm endodontic hand instrument or a small-diameter rotary instrument until the desired post length and remaining gutta-percha length are achieved (Fig 3-14b).

2. Enlarge the canal using the rotary instrument that corresponds to the final dimension of the selected post (Fig 3-14c). The post should fit passively in the post space but be sufficiently proximate that it does not exhibit substantial movement in the canal (Fig 3-14d). 3. At least the apical half of the post must possess good approximation to prepared tooth structure. The coronal half of the post may not fit as well because of root canal flaring. However, this lack of adaptation can be corrected when the core material is placed around the cemented post. 4. If the root canal cannot be prepared so that it conforms to the round shape of the post and has adequate approximation to the root canal walls, then a custom cast post may be preferable. 5. Do not remove more dentin at the apical end of the post space than is necessary. 6. When necessary, take radiographs to confirm appropriate seating and length of the post. 7. Shorten the incisal or occlusal end of the post so that it does not interfere with the opposing occlusion but extends occlusally sufficient to provide support and retention for the restorative core material (2 to 3 mm). If nonmetallic prefabricated posts are being used, do not use scissors to cut the posts; instead, shorten them with a diamond rotary instrument. 8. When metal posts are used, bend them slightly coronally, if necessary, to align them within the core material. Always remove the metal post from the tooth and bend it outside the mouth with orthodontic pliers. 9. Cement the post in the root canal using resin bonding procedures (Fig 3-14e). 10. Condense restorative material around the post or bond the restorative material to the post and remaining tooth structure, depending on the material used to form the core. Place a slight excess of material so that it can be prepared to the desired crown preparation form after hardening (Fig 3-14f). 11. Complete the definitive tooth preparation (Figs 3-14g to 3-14i) and make an impression for the crown.

Fig 3-14 (a) An endodontically treated maxillary left lateral incisor has canal filling material in the access cavity. (b) The root canal filling material is removed, and the desired post length is achieved. (c) The canal is enlarged using the rotary instrument that corresponds to the final dimension of the selected post. (d) The prefabricated post is tried in. (e) The nonmetallic prefabricated post is shortened with a diamond rotary instrument. The post is then cemented in the root canal. (f) Coronal composite resin is added to form the desired dimensions of the core. (g) The composite resin is prepared with a high-speed diamond and water spray to resemble a complete-crown tooth preparation. (h) The definitive restoration is fabricated and cemented in i place. (i) Postoperative radiograph.

Direct core materials Three basic direct core materials can be used as core buildup materials for the restoration of endodontically treated teeth: silver amalgam, composite resin, and sometimes glass-ionomer–based core materials. The desirable features of a core material have been discussed in the literature; they include: biocompatibility, adequate compressive strength to resist intraoral forces, ease of manipulation,

dimensional stability, minimal potential for water absorption, and sufficient flexural strength to resist the forces of occlusion. Amalgam Amalgam is a viable alternative for a core material. It has physical properties that are better than those of most other core materials. Amalgam has been reported to perform best as a core material under simulated clinical conditions because of its high compressive strength and rigidity. 234–237 Amalgam has a long clinical record of success,238 is strong and relatively dimensionally stable (even in the presence of water), and is easy to condense. The resistance to leakage of amalgam improves with time because of its corrosion products. Studies demonstrated that dispersed phase alloys have significantly lower initial leakage compared with spherical alloys.239 It is a relatively inexpensive material compared with composite resin or glass ionomer. The disadvantages of amalgam, when used as a core material, are its lack of bonding to dentin, the poor color under an all-ceramic crown, and the formation of amalgam tattoo during tooth preparation. At initial setting, the strength of amalgam is low. Hence, it cannot be prepared right away even when a fast-setting spherical alloy has been used. Studies have shown that the success of amalgam used as a core material depends on the amount of coronal tooth structure left and the presence of adequate depth of the pulp chamber240, 241 (Fig 3-15). Amalgam extension into the canal is recommended only when less than 2 mm of pulp chamber is available. Amalgam cores retained by the cervical one-third of the canals and the pulp chamber proved to be more retentive than cast post and core buildups242 (Fig 3-16).

Fig 3-15 (a) An endodontically treated mandibular left second molar presents with enough remaining coronal tooth structure and adequate depth of the pulp chamber. (b) The root canal filling material is removed, and amalgam is packed in the pulp chamber.

Fig 3-16 Amalgam is extended into the canal when the pulp chamber is less than 2 mm deep.

Amalgam cores under a crown have the lowest failure rate, followed by composite resin and glass ionomer. 234, 236, 237 Nayyar et al241 restored more than 400 posterior teeth with an amalgam coronal-radicular core and followed them for bout 4 years; they found that no failure was attributed to the amalgam core. Several techniques using provisional crowns or matrices have been proposed to facilitate the placement of silver amalgam core buildup material in endodontically treated teeth.243–246 Amalgam as a core material is recommended for large buildups, deep margins, and when the buildup margins are close to the crown finish lines. It is the only core material where it is acceptable to occasionally put a crown margin on amalgam. Step-by-step modification of a provisional FPD into a matrix for an amalgam core buildup 1. Finalize the tooth preparation and remove all existing restorations, weakened dentin, caries lesions, and undermined dental structure. 2. Fabricate a provisional FPD. Establish proper contours, thickness, proximal contacts, and occlusal contacts (Figs 3-17a and 3-17b). If enough tooth structure is available, use a matrix band. 3. Remove 1 to 2 mm of gutta-percha from the orifice of the canals to aid in retention of the core. This is only necessary when the pulp chamber is smaller than 3 mm in depth (Fig 3-17c).

4. Use a carbide rotary cutting instrument to make an occlusal access opening in the abutment retainer toward the center of the foundation. 5. Place the modified provisional FPD on the remaining tooth structure, and confirm adequate access to the cavity for ideal amalgam placement and condensation (Fig 3-17d). 6. Confirm proper fit and marginal adaptation of the provisional FPD. 7. Cement the modified provisional FPD with a small amount of provisional cement placed only on the margins of the provisional FPD. 8. Condense the first increments of amalgam into the prepared post spaces using a periodontal probe or an endodontic plugger. Fill the remaining pulp chamber with amalgam up to the occlusal surface of the provisional FPD to ensure an adequate seal, and make occlusal adjustments as needed (Fig 3-17e). 9. At the following appointment, carefully section the provisional FPD by using a tapered rotary cutting instrument to make a vertical groove in the buccal surface (Figs 3-17f and 3-17g). 10. Refine the amalgam foundation for the definitive tooth preparation, and take the definitive impression (Figs 3-17h and 3-17i). 11. Fabricate and cement a new provisional FPD with provisional cement.

Fig 3-17 (a and b) A provisional fixed dental prosthesis is fabricated in resin composite material. The restoration has proper contours, thickness, proximal contacts, and adequate occlusal contacts. (c) Gutta-percha is removed from the orifice of the canals to aid in retention of the core. (d) A carbide rotary cutting instrument is used to make an occlusal access opening on the provisional prosthesis, toward the center of the foundation. (e) The FPD is cemented, and the amalgam is condensed in the prepared post spaces. (f and g) A tapered rotary cutting instrument is used carefully to make a vertical groove in the lingual surface in order to section the provisional prosthesis. (h and i) The amalgam foundation is refined for the definitive tooth preparation, and a final impression is taken.

The same procedure is used when a provisional crown is used as a matrix for an amalgam core buildup (Fig 3-18).

Fig 3-18 (a) The mandibular right first molar was endodontically treated and presented with enough remaining coronal tooth structure and adequate depth of the pulpal chamber. (b) Tooth preparation is finished, and the post space is prepared in the distal canal to receive a prefabricated metallic post. (c) The provisional crown is fabricated using resin material with proper contours, thickness, proximal contact, and adequate occlusal contacts. (d) An occlusal access opening in the provisional crown is made so only a peripheral shell of resin is retained using a carbide rotary cutting instrument. The provisional crown is cemented with a luting agent. The length of the prefabricated post is adjusted to the appropriate height, and the post is cemented with zinc phosphate cement. (e) The amalgam is condensed into the prepared post space. (f and g) After the amalgam has hardened or at a subsequent appointment, the provisional crown is sectioned carefully by making a vertical groove in the labial

surface using a tapered rotary cutting instrument. (h) The amalgam foundation is refined for the definitive tooth preparation, and a final impression is taken. (Courtesy of Dr Carlos E. Sabrosa, Rio de Janeiro, Brazil.)

Composite resin Composite resin is a popular core material because it is easy to use and satisfies esthetic demands. Certain properties of composite resins are inferior to those of amalgam but superior to glass-ionomer materials.234, 247 Kovarik et al234 showed that composite resin is more flexible than amalgam. It adheres to tooth structure, may be prepared and finished immediately, and has good color under all-ceramic crowns. Composite resin appears to be an acceptable core material when substantial coronal tooth structure remains235, 248–253 but a poor choice when a significant amount of tooth structure is missing.234, 254 One disadvantage of composite resin cores is the instability of the material in oral fluids (water sorption).255, 256 Oliva and Lowe255 found that composite resin cores were not dimensionally stable when exposed to moisture. However, Vermilyea et al 257 found that the use of a well-fitting provisional restoration will provide the composite resin core with some degree of moisture protection. Hygroscopic expansion of composite resin cores and cements in layered structures with an overlying ceramic layer can generate significant stresses that have the potential to cause extensive cracking in the overlying ceramic layer. Clinically, this implies that all-ceramic crown performance may be compromised if the crowns are luted to composite cores that have undergone hygroscopic expansion.258 Another disadvantage is that composite resin is dimensionally unstable (setting shrinkage). Shrinkage during polymerization causes stress on the adhesive bond, resulting in gap formation, which may contribute to long-term bond failure.255 The less filler that is present in the composite resin, the greater the shrinkage that will occur. For this reason, it is imperative to avoid using flowable composite resins as buildup material because of their low filler content and their poor mechanical properties (flow, flexural strength, and stiffness).259 Application of composite resin is technically demanding and requires careful adherence to material-handling protocols. The core should be built up in small increments, and studies have shown that this process produces a denser core.260 It is highly recommended that a rubber dam be placed when composite resin is used as a core buildup material. Glass ionomer

Glass ionomer is a tooth-colored material used by some clinicians as a core buildup material. It adheres to tooth structure by forming a chemical bond and has a low thermal expansion coefficient and low polymerization shrinkage.261 Glass ionomer has the ability to release fluoride.261, 262 In an in vitro study, Kovarik et al 234 found that glass ionomer was the weakest core buildup material when compared with amalgam and composite resin. The lack of adequate strength (flexural and tensile) along with a sensitivity to moisture lower its resistance to fracture and makes it an inadequate direct core material.250–252, 263, 264 It is recommended that glass ionomer be used primarily to block minor undercuts in a tooth preparation. In an effort to improve the viscosity of glass ionomer, silver alloys were added to glass ionomer. 265 The addition of silver alloys resulted in a higher flexural strength and a lower modulus of elasticity. 234, 263 However, studies have shown that silver-reinforced glass ionomer could not withstand simulated masticatory forces.250– 252, 266 Therefore, even when reinforced, glass ionomer is not suitable if the core material forms a substantial portion of the retention and resistance form for the overlying restoration.

Summary Most endodontically treated posterior teeth should be restored with crowns to enhance their longevity. However, reasonably sound endodontically treated anterior teeth do not need a crown to enhance their clinical success. They can be restored with a conservative filling material unless they are weakened by previous restorations or require significant color/form change. Posts do not reinforce endodontically treated teeth. Their only purpose is to retain the core. Several prefabricated posts and direct core materials are available.

Acknowledgment The authors would like to thank People’s Medical Publishing for granting permission to reuse some of the material published in their chapter of Ingle’s Endodontics, ed 6.267

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239. Mahler DB, Engle JH. Clinical evaluation of amalgam bonding in Class I and II restorations. J Am Dent Assoc 2000;131:43–49. 240. Trabert KC, Caput AA, Abou-Rass M. Tooth fracture—A comparison of endodontic and restorative treatments. J Endod 1978; 4:341–345. 241. Nayyar A, Walton RE, Leonard LA. An amalgam coronal-radicular dowel and core technique for endodontically treated posterior teeth. J Prosthet Dent 1980;43:511–515. 242. Kane JJ, Burgess JO, Summitt JB. Fracture of amalgam coronalradicular restorations. J Prosthet Dent 1990;63:607–613. 243. Chapman KW. A matrix band technique for large amalgam cores. J Am Dent Assoc 1981;102:56–57. 244. Smidt A, Venezia E. Techniques for immediate core build-up of endodontically treated teeth. Quintessence Int 2003;34:258–268. 245. Echeto LF, Nimmo A. Using a posterior provisional crown as a matrix for an amalgam foundation. J Prosthet Dent 2010;104:56–59. 246. Erickson DM. Using a posterior provisional crown as a matrix for an amalgam foundation [comment]. J Prosthet Dent 2010; 104:352. 247. Larson TD. Core restoration for crown preparation. Northwest Dent 2004;83(5):19,22–25,28. 248. Levartovsky S, Kuyinu E, Georgescu M, Goldstein GR. A comparison of the diametral tensile strength, the flexural strength, and the compressive strength of two new core materials to a silver alloy-reinforced glass-ionomer material. J Prosthet Dent 1994;72:481–485. 249. Cohen BI, Deutsch AS, Condos S, Musikant BL, Scherer W. Compressive and diametral tensile strength of titanium reinforced composites. J Esthet Dent 1992;4(suppl):50–55. 250. Cohen BI, Condos S, Deutsch AS, Musikant BL. Fracture strength of three different core materials in combination with three different endodontic posts. Int J Prosthodont 1994;7:178–182. 251. Cohen BI, Pagnillo MK, Condos S, Deutsch AS. Four different core materials measured for fracture strength in combination with five different designs of endodontic posts. J Prosthet Dent 1996;76:487–495. 252. Cohen BI, Pagnillo MK, Newman I, Musikant BL, Deutsch AS. Cyclic fatigue testing of five endodontic post designs supported by four core materials. J Prosthet Dent 1997;78:458–464. 253. Sornkul E, Stannard JG. Strength of roots before and after endodontic treatment and restoration. J Endod 1992;18:440–443. 254. Creugers NH, Mentink AG, Fokkinga WA, Kreulen CM. 5-year follow-up of a prospective clinical study on various type of core restorations. Int J

Prosthodont 2005;18:34–39. 255. Oliva RA, Lowe JA. Dimensional stability of composite used as a core material. J Prosthet Dent 1986;56:554–561. 256. Azer SS, Drummond JL, Campbell SD, Moneim Zaki A. Influence of core buildup material on the strength of an all-ceramic crown. J Prosthet Dent 2001;86:624–631. 257. Vermilyea SG, Gardner FM, Moergell JR Jr. Composite dowels and cores: Effect of moisture on the fit of cast restorations. J Prosthet Dent 1987;58:429– 431. 258. Malament KA, Socransky S, Thompson V, Rekow D. Survival of glass-ceramic materials and involved clinical risk: Variables affecting long-term survival. Pract Proced Aesthet Dent 2003;(suppl):5–11. 259. Attar N, Tam LE, McComb D. Flow, strength, stiffness and radiopacity of flowable resin composites. J Can Dent Assoc 2003; 69:516–521. 260. Mentink AG, Meeuwissen R, Hoppenbrouwers PP, Kayser AF, Mulder J. Porosity in resin composite core restorations: The effect of manipulative techniques. Quintessence Int 1995;26:811–815. 261. Sivers JE, Johnson WT. Restoration of endodontically treated teeth. Dent Clin North Am 1992;36:631–650. 262. Basso GR, Della Bona A, Gobbi DL, Cecchetti D. Fluoride release from restorative materials. Braz Dent J 2011;22:355–358. 263. Cho GC, Kaneko LM, Donovan TE, White SN. Diametral and compressive strength of dental core materials. J Prosthet Dent 1999;82:272–276. 264. Bullard RH, Leinfelder KF, Russell CM. Effect of coefficient of thermal expansion on microleakage. J Am Dent Assoc 1998; 116:871–874. 265. McLean JW, Powis DR, Prosser HJ, Wilson AD. The use of glassionomer cements in bonding composite resins to dentin. Br Dent J 1985;158:410–414. 266. Cohen BI, Pagnillo MK, Newman I, Musikant BL, Deutsch AS. Pilot study on the cyclic fatigue characteristics of five endodontic posts with four core materials. J Oral Rehabil 2000;27:83–92. 267. Goodacre CJ, Baba NZ. Restoration of endodontically treated teeth. In: Ingle JI, Bakland LK, Baumgartner JG (eds). Ingle’s Endodontics, ed 6. Hamilton, ON: BC Decker, 2008:1431–1473.

Principles for Restoration of Endodontically Treated Teeth Several factors affect the outcome when endodontically treated teeth are restored. Guidelines have been developed for each of these factors based on scientific evidence and clinical experience.

Post Length It has been reported that the longer the post, the higher its retentive ability. 1, 2 The appropriate length for a post should be based on its potential to minimize damage to the tooth, optimize post retention, and maintain an appropriate apical seal for the root canal filling. A wide range of recommendations have been made regarding post length, including the following: (1) the post length should equal the incisocervical or occlusocervical dimension of the crown3–10; (2) the post should be longer than the crown11; (3) the post should be one and one-third times the crown length12; (4) the post should be one-half the root length13, 14; (5) the post should be two-thirds the root length15–19; (6) the post should be four-fifths the root length20; (7) the post should be terminated halfway between the crestal bone and the root apex21–23; and (8) the post should be as long as possible without disturbing the apical seal.24 A review of scientific data provides the basis for differentiating among these varied guidelines. Short posts have never been advocated; however, they have been frequently

observed during radiographic examinations (Fig 4-1). Several studies have demonstrated that short posts are associated with higher root stresses and greater tendency for root fracture to occur.25–28 In a three-dimensional finite-element analysis of post dimension on stress distribution in dentin of endodontically treated teeth, Holmes et al29 found that short posts produce higher shear stresses in dentin.

Fig 4-1 (a) A very short post has been placed in the root of a maxillary lateral incisor. The prosthesis has loosened. (b) A second premolar has been restored with a very short post; the lack of adequate retention for the core can result in loosening of the prosthesis.

Clinical studies26–28, 30 on the length of posts cemented in endodontically treated teeth have been conducted. Grieve and McAndrew28 found that only 34% of 327 posts were as long as the incisocervical length of the crown. Martin and Jedynakiewicz30 examined 217 posts and determined that only 5% of the posts were two-thirds to three-quarters the root length. Ross27 evaluated 200 endodontically treated teeth and determined that only 14% of posts were two-thirds or more the root length, and 49% of the posts were onethird or less the root length (Fig 4-2). In a retrospective clinical study of 52 posts, Turner26 radiographically compared the length of the post with the maximum length available if 3 mm of gutta-percha was retained. Posts that came loose used only 59% of the ideal length, and only 37% of the posts were longer than the proposed minimum length.

Fig 4-2 (a and b) Maxillary metal-ceramic crowns have failed because the posts were so short that the crowns loosened as a result of the forces of occlusion.

Sorensen and Martinoff31 determined that clinical success was markedly improved when the post length was equal to or greater than the crown length. Johnson and Sakumura1 determined that posts that were three-quarters or more the root length were up to 30% more retentive than posts one-half the root length or posts equal to the crown length. Leary et al32 indicated that posts with a length at least three-quarters that of the root offered the greatest rigidity and least root bending. When teeth have diminished bone support, stresses increase dramatically and are concentrated in the dentin near the post apex.33 A recent finite-element model study 34 established a relationship between post length and alveolar bone level. To minimize stress in the dentin and in the post, the post should extend more than 4 mm apical to the bone (Fig 4-3).

Fig 4-3 (a) The diminished bone support of a maxillary central incisor causes an increase in stresses concentrated in the dentin near the post apex. (b) Stresses have caused root fracture. (c) The broken crown shows the fracture line at the apex of the post.

On the other hand, excessive length of posts can cause perforation35, 36 (Fig 4-4), vertical root fracture,37 and loss of apical seal.38 In an in vitro study comparing the effect of post length on the retention of metallic and nonmetallic prefabricated posts, Borer et al39 found that longer posts were more retentive than short posts. They also concluded that the type of post and cement used had no effect on the retention of the prefabricated posts that were used. Fuss et al37 evaluated the impact of operative procedures on endodontically treated teeth that presented with root fractures. Their findings suggested that long posts are better than short ones. They concluded that some other factors might be involved, such as post design and the amount of force applied while the post is placed and cemented in the post space.

Fig 4-4 The excessive length of a post has caused root perforation.

Guidelines for post length Data indicate that, from the standpoint of post retention and resistance of the root to fracture, post length should be three-quarters the length of the root. However, some interesting results occurred when post length guidelines of two thirds to threequarters the root length were applied to teeth with average, long, and short root lengths. It was determined40 that placement of a post approaching this recommended length range is not possible without compromising the apical seal of the root canal filling material. When the root length is long, the goal is to use a post that is as long as possible while retaining 5 mm of gutta-percha apically. When a tooth has an average or short root length, placement of a post two-thirds the root length does not permit the maintenance of an adequate seal, and roots will have less than the optimal amount of gutta-percha seal. Shillingburg et al41 also indicated that selection of a post length that is equal to the clinical crown length can cause the post to encroach on the 4.0-mm safety zone required for an apical seal. Several laboratory studies have compared the amount of remaining gutta-percha and its effects on the apical seal.42, 43 It was determined that a large number of root canal specimens actually leaked when only 2.0 mm of apical gutta-percha was present,42 and most specimens leaked with 3.0 mm of gutta-percha.43 In fact, one corresponding clinical study found significantly more posttreatment periapical

radiolucencies in teeth with less than 3.0 mm of gutta-percha.44 In contrast, when 4.0 mm of gutta-percha is retained and left undisturbed, studies have shown little42, 45 or no46, 47 evidence of leakage. Based on these outcomes data, 4.0 mm may be regarded as the minimum amount of apical gutta-percha required to ensure an adequate apical endodontic seal. However, because length determinations are frequently based on radiographic images and radiographic angulations vary clinically, it is recommended that 5.0 mm of apical gutta-percha, as measured on a radiographic image, be used as the minimum obturation length. The post itself should extend directly to the point where the gutta-percha is located, leaving no space between the end of the post and the beginning of the gutta-percha. Abou-Rass et al35 proposed a post length guideline for maxillary and mandibular molars based on the incidence of lateral root perforations occurring when post preparations were made in 150 extracted teeth. They determined molar posts should not be extended more than 7 mm apical to the root canal orifice (Fig 4-5) and that length should only be used in the primary roots (distal roots of mandibular molars and palatal roots of maxillary molars).

Fig 4-5 The post in the distal canal of the mandibular molar extends to a maximal length of 7 mm.

Post Diameter Several studies2, 48–50 have demonstrated that an increase in post diameter does not increase the retention of the post in the post space. Additionally, an increase in the diameter of a post necessitates the removal of unnecessary tooth structure, in particular radicular dentin, decreasing the resistance to fracture of endodontically treated teeth25, 49, 51–53 (Fig 4-6). Deutsch et al51 determined that, when largediameter posts (1.5 mm or more) were placed, root fracture increased sixfold for every millimeter of decreased root diameter. In addition, an increase in the diameter of the post increases internal stresses within the tooth.52–54 Studies have shown that root fracture is the second most common cause of post and core failure.55–59

Fig 4-6 (a and b) The post diameter is exces sive in the root of a maxillary first premolar (a) and a maxillary canine (b).

It is highly recommended that post diameter not exceed one-third the root diameter and that post diameters be proportionally related to average root dimensions.35 To ensure that posts do not exceed one-third the root diameter, the post diameter should be between 0.6 and 1.2 mm, depending on the tooth.35, 41, 60, 61 Only post preparation instruments that match the desired diameter of the post space should be used. When a particular brand of post is used, clinicians must make sure that the matching drill belongs to the same type of post. Even proper use of rotary instruments to prepare the post space has also been proven to cause root thinning and perforations.35, 62, 63 Gates Glidden drills are considered a predictable method for initial post space preparation.64, 65 They are safer than Peeso reamers because they are not end cutting and deviate less from the center of a treated canal space.66 Abou-Rass et al35 evaluated 150 extracted maxillary and mandibular molars and proposed a post length guideline for these teeth based on the incidence of lateral root perforations when post preparations were made with No. 2, No. 3, or No. 4 Peeso reamers. They suggested that practitioners should avoid mesial roots of mandibular molars and buccal roots of maxillary molars and use only No. 2 Peeso reamers. They found that, at the apical extent of the preparation, the mean dentin thickness on the furcal side of the root was 0.92 mm or less in all samples. Raiden et al61 evaluated several instrument diameters to determine which ones

would preserve at least 1.0 mm of root wall thickness following post preparation of 106 maxillary first premolars. They found that 1.0 mm of residual dentin was only present when 0.7-mm-diameter Peeso reamer instruments were used. Another study62 found that when a Gates Glidden No. 4 bur was used to prepare the post space, there was a 7.3% incidence of perforation on the furcal side of the root. The larger the drill, the higher was the incidence of perforation. The safest technique for the preparation of a post space is the use of heated instruments with or without the use of rotary instruments.67, 68 A good understanding of dental anatomy, as well as the configuration of the roots and their variations, and use of an appropriate instrument angulation help to prevent root thinning and perforation. Instruments should be angled so that they follow the canal (Fig 4-7).

Fig 4-7 (a) Preparation of the post space with instruments not held parallel to the root canal has created a perforation in the mesial root of the mandibular right first molar. (b) The same type of perforation has occurred in a mandibular right second premolar.

Perforations and root fractures can be differentiated radiographically. The fractured root produces a diffuse radiolucency with an oval or teardrop-shaped form (Fig 4-8), while the perforated root produces a radiolucency with distinct borders and a rounder form (Fig 4-9).

Fig 4-8 Excessive post diameter has created a fracture in the root. Note the teardrop-shaped form of the radiolucent lesion, a characteristic indicative of a root fracture.

Fig 4-9 A perforation is present in the root concavity. Note the distinct border and round form of the radiolucent lesion, characteristics indicative of a root perforation.

When posts are needed in molars, they should be placed in roots that have the greatest dentin thickness. These roots, known as the primary roots, are the palatal roots of maxillary molars and the distal roots of mandibular molars. The mesial roots of mandibular molars and the facial roots of maxillary molars should be

avoided if at all possible (Fig 4-10). On all roots, instrument pressure on the root surface toward the furcation should be avoided because this surface is thinned more than the outer surface as a result of root curvature.

Fig 4-10 (a) A radiograph of a mandibular left second molar indicates that the mesial root is perforated. (b) The extracted tooth shows the perforated mesial root.

Likewise, the apical 5.0 mm of the roots should be avoided because most root curvatures occur within 5.0 mm of the root apex,69 and entrance into this area increases the risk of excessive root thinning or perforation (Fig 4-11).

Fig 4-11 Severely curved root apices should be avoided during post space preparation.

Canal Preparation

Guidelines for coronal tooth preparation The first step in fabrication of a post and core should ideally be the preparation of the coronal tooth structure for the type of definitive restoration that will be placed (all-metal crown, metal-ceramic crown, all-ceramic crown, etc). Each of these restorations requires different amounts of tooth reduction, and the form of the tooth preparation varies considerably. Prior preparation of the coronal tooth structure allows assessment of the structural integrity of remaining dentin and enamel. When the remaining peripheral tooth structure is very thin and likely would not possess sufficient strength to resist occlusal forces transmitted through the crown to the tooth, the thin structure is removed and replaced as part of the core. This order of procedure also establishes morphologic borders that can be used to guide core fabrication so that it is confluent with surrounding tooth structure and possesses the desired tooth preparation form.

Guidelines for pulp chamber preparation Treatment materials present in the pulp chamber following endodontic treatment (restorative materials sealing the coronal access and gutta-percha) are removed with rotary instruments. If a prefabricated post will be cemented in a root canal and a restorative material core will be built around the post, then morphologic undercuts present in the pulp chamber should be retained for core retention. If a custom cast post and core will be fabricated, then pulp chamber undercuts should be blocked out with a definitive cement or restorative material that is bonded to the tooth, or the undercut should be eliminated by removal of tooth structure. If removal of the undercut through tooth preparation would result in substantial removal of tooth structure that weakens the tooth, then blocking out the undercut is the treatment of choice.

Guidelines for root canal preparation The individual who completed the root canal treatment is ideally suited to prepare the post space, being the one who is most knowledgeable regarding root curvatures and areas where no further root preparation should be performed because it will result in areas of thin residual dentin. For this reason, it may be prudent to prepare the root canal for a post as a continuation of the endodontic treatment. If the canal has not been prepared for a post as part of the endodontic treatment process, it will be necessary to remove the obturation material with either a warm

endodontic hand instrument or a low-speed rotary instrument. If a warm hand instrument is to be used, rubber dam should be placed first to prevent aspiration or swallowing of the hand instrument should it be dropped. The safest technique to prepare the length of the post space is to have an exact recorded measurement of canal length relative to a known landmark. If the clinician is totally confident of the measurement (eg, he or she personally performed the endodontic treatment), he or she may remove the gutta-percha prior to axial and incisal reduction. This is possible because the working length of the canal is available and was obtained during the cleaning and shaping of the root canal. If the clinician did not perform the endodontic treatment, it is advisable to learn the working length and the landmark that the endodontist used. It is prudent not to rely solely on measurements of radiographs (because they usually have a magnification error) or someone else’s measurements (which may have been recorded in error or may have been made relative to a different landmark). Successful use of rotary instruments is related to initial use of a small-diameter instrument (one that only removes the restorative material with very little removal of dentin). This small-diameter instrument is used to remove small vertical increments (1 to 2 mm) of the root canal filling material. After each vertical increment is removed, a visual inspection should be made to verify that the endodontic filling material is centered in the post preparation. The incremental removal of the root canal obturation is continued until the appropriate length is established (leaving 4 to 5 mm of gutta-percha as an apical seal). A rubber stop is placed on the shank of the instrument and used as a guideline. The clinician should stop short of the intended final depth and confirm the amount of gutta-percha removed with a radiograph and the use of a periodontal probe. A final radiograph of the prepared post space is made when gutta-percha removal has been completed. Care should be taken not to enlarge the canal in diameter. After the length is established, any required increases to the post diameter are accomplished incrementally with larger rotary instruments or hand files. A good reference to remember to avoid unnecessary enlargement of root canals is the following: A No. 3 Peeso instrument is equal to a No. 4 Gates Glidden drill, which is also equal to a No. 110 ISO file.

Immediate versus delayed removal of gutta-percha and post space preparation Several studies45, 47, 70, 71 have indicated that there is no difference in the leakage of the root canal filling material when the post space is prepared immediately after

completion of endodontic therapy. Bourgeois and Lemon70 found no difference between immediate preparation of a post space and preparation 1 week later when 4 mm of gutta-percha was retained. Zmener45 found no difference in dye penetration between gutta-percha that was removed after 5 minutes and gutta-percha that was removed after 48 hours. Two sealers were tested, and 4 mm of gutta-percha was retained apically. When lateral condensation of gutta-percha was used, Madison and Zakariasen47 found no difference in the dye penetration between immediate removal and 48-hour removal. Using the chloropercha restoration technique, Schnell71 found no difference between immediate removal of gutta-percha and no removal of gutta-percha. By contrast, Dickey et al72 found significantly greater leakage with immediate guttapercha removal. Kwan and Harrington73 tested the effect of immediate gutta-percha removal using both warm instruments and rotary instruments. There was no significant difference between no removal and immediate removal of gutta-percha with warm pluggers and files. Compared to the controls, there was significantly less leakage after immediate removal of gutta-percha when Gates Glidden drills were used. Karapanou et al74 compared immediate and delayed removal of two sealers (a zinc oxide–eugenol–based sealer and a resin-based sealer). No difference between immediate and delayed removal was noted with the resin-based sealer, but delayed removal of the zinc oxide–eugenol sealer produced significantly greater leakage. Abramovitz et al75 compared immediate gutta-percha removal with hot pluggers and delayed gutta-percha removal (after 2 weeks) with Gates Glidden drills. They found no difference between the two methods. Portell et al43 found that delayed gutta-percha removal (after 2 weeks) caused significantly more leakage than immediate removal when only 3 mm of gutta-percha was retained apically. Fan et al76 found more leakage from delayed removal of guttapercha. Solano et al77 found a significant difference in apical leakage between teeth whose post spaces were prepared at the time of the obturation and those prepared 1 week later using warm gutta-percha condensation and AH Plus sealer (Dentsply). Adequately condensed gutta-percha can be safely removed immediately after endodontic treatment (Fig 4-12).

Fig 4-12 (a and b) The gutta-percha in these molars is adequately condensed. (Courtesy of Dr Axel Yabroudi, Phoenix, AZ.)

Instruments for removal of gutta-percha without disturbing the apical seal Three methods have been advocated for the removal of gutta-percha during preparation for a post space: chemical (oil of eucalyptus, oil of turpentine, and chloroform), thermal (electric or heated instruments), and mechanical rotary instruments. The chemical removal of gutta-percha for post space preparation is not utilized for specific reasons (resulting microleakage and inability to control removal).65, 70 However, thermal or mechanical techniques or a combination of both is routinely used. Multiple studies42, 65, 78 have determined that there is no difference in leakage regardless of whether gutta-percha is removed with hot instruments or removed with rotary instruments. Suchina and Ludington78 and Mattison et al65 found no difference between removal with hot instruments and removal with Gates Glidden burs. Camp and Todd 42 found no difference among Peeso reamers, Gates Glidden burs, and hot instruments. Hiltner et al79 compared warm plugger removal with two types of rotary instruments (GPX burs [Brasseler] and Peeso reamers). There were no significant differences in dye leakage among any of the groups. Contrasting results were found by Haddix et al,67 who measured significantly less leakage when gutta-percha was removed with a heated plugger than when either a GPX instrument or Gates Glidden drills were used. DeCleen80 found that it is desirable to remove gutta-percha first with a heated instrument and then with a small Gates Glidden drill. Using a pressure-driven radioactive tracer assay, Abramovitz et al75 found no difference in apical leakage between hot pluggers and Gates Glidden drills. Balto et al81 compared two methods of gutta-percha removal and their impact

on apical leakage. They found that removing gutta-percha with Peeso reamers resulted in less leakage than use of a hot plugger.

Time of placement of definitive restoration after post space preparation Provisional coronal access restoration Balto et al81 compared the leakage of different provisional materials used in postprepared root canals. They found that none of the provisional restorations they tested (Cavit [3M ESPE], IRM [Dentsply], and Temp Bond [Kerr]) prevented coronal leakage when left for a long period of time (30 days). Safavi et al82 evaluated the prognosis of endodontically treated teeth following delayed placement of the definitive coronal restoration. A total of 464 endodontically treated teeth were followed radiographically for up to 23 months. They found a higher success rate when the definitive restorations (amalgam, composite resin, or definitive restoration with or without posts and cores) were placed than when teeth were restored with provisional coronal access restorations (IRM or Cavit). Torabinejad et al 83 found that defective restorations could cause root canal system reinfection within 19 days. Ray and Trope 84 found that a combination of poor coronal restoration and poor endodontic treatment resulted in a high failure rate for endodontically treated teeth. In a retrospective study, Iqbal et al 85 found that a combination of good-quality endodontic treatment and coronal restoration leads to a high success rate for endodontically treated teeth. Contrasting results were reported by Tronstad et al, 86 who found that the quality of the endodontic treatment was significantly more important than the quality of the coronal restoration. One-piece provisional restoration It is well established that a deficient root canal obturation and a poor coronal restoration have the potential to allow endotoxins, bacteria, and saliva to penetrate the root canal, causing periapical inflammation.83, 87–92 Provisional restorations are mainly used to provide the patient with a functional and esthetic restoration. They also protect the hard and soft tissues prior to placement of the definitive restoration. However, provisional restorations are considered restorations with poor coronal seal. Several studies81, 82, 93–95 have indicated that there is significant coronal leakage when the tooth is restored with a

provisional restoration. To prevent contamination of the root canal system when a cast post and core is being used, the prepared tooth should be restored with a well-fitting provisional restoration (with good marginal seal and occlusion), and then the definitive cast post and core should be cemented in as short a time as possible.

Ferrule Effect According to one dictionary, a ferrule is defined as “a ring or cap of metal placed around a shaft such as the handle of a tool to strengthen the handle and prevent it from splitting.”96 This term has been adopted by dentistry to describe the characteristic in which a crown encompasses a sufficient amount of cervical tooth structure in the clinical crown to prevent tooth fracture. Ferrules can be created in two ways: First, a coronal core buildup can encompass tooth structure, and, second, the preparation for a cast restoration can extend to sound tooth structure in the cervical portion of coronal tooth structure below any core restorative material (Fig 4-13). However, several studies have shown that the first type, core ferrules, generally do not improve the resistance of a tooth to fracture if the tooth is restored with a post.97–100 On the other hand, crown ferrules were found to be effective for enhancing resistance to fracture.101–107

Fig 4-13 A ferrule will be created when the overlying crown engages tooth structure. The definitive restoration is at least 2 mm apical to the core-tooth junction.

Circumferential height The recommended amount of cervical tooth structure encompassed by the crown has been studied extensively, but the recommended guidelines range from 1.0 mm102 to 1.0 to 2.0 mm101, 102 to 1.25 to 2.5 mm104 to 1.5 to 2.0 mm108; more recently, several authors have suggested a minimum of 2.0 mm.105–107105–107 mm ferrule significantly increased a tooth’s fracture resistance compared with a 2.0-mm-high ferrule.109

Axial wall dimensions Laboratory studies One study compared extracted teeth with a uniform mm ferrule on all four axial

surfaces (facial, lingual, mesial, and distal) with teeth that had a 2.0-mm ferrule on the facial and lingual surfaces but only a 0.5-mm ferrule on the two proximal surfaces.107 The 2.0-mm uniform ferrules had significantly greater fracture resistance than did the nonuniform ferrules. While nonuniform crown ferrules were less resistant to fracture than uniform ferrules, they still presented significantly greater fracture resistance than did teeth with no ferrule. It was also interesting to note that, while a post and core do not strengthen endodontically treated teeth, they also did not weaken teeth that had a uniform 2.0-mm-high cervical ferrule.107 Another laboratory study evaluated the effects of simulated chewing on the fracture resistance of 40 extracted endodontically treated maxillary central incisors. Teeth with a uniform 2.0-mm ferrule height on all four axial surfaces were compared with three types of modified teeth where the ferrule was: (1) only present lingually, (2) only present facially, or (3) present on both the facial and lingual axial walls but absent from both proximal surfaces.110 When portions of the cervical crown ferrule were absent, variations in the failure load were greater than they were in teeth with a 2.0-mm ferrule on all the axial surfaces.110 Clinical studies A 2011 clinical study of fiber posts compared the number of preserved coronal walls in endodontically treated premolars.111 The authors determined that the tooth survival rate was greater for teeth with three or four coronal walls at the time of the core buildup, demonstrating the importance of a crown ferrule.111 A previous 3-year clinical study of 240 fiber posts also determined that teeth with one, two, or three residual coronal walls had a significantly lower risk of failure than did teeth missing all the coronal walls and, therefore, no potential to create a ferrule.112 If insufficient cervical tooth structure remains to develop a ferrule, surgical crown lengthening or orthodontic extrusion to expose more tooth structure should be considered. It may be prudent to extract a tooth and replace it with an implant and crown when one or more of the following conditions is present: a ferrule cannot be developed; crown lengthening would create an unacceptable esthetic environment or produce a furcation defect; or a short root that would not permit development of appropriate post length is present. Presence of a ferrule effect is important for achieving a high success rate regardless of the type of post being used (cast post and core, metallic prefabricated post, or nonmetallic prefabricated post). In the absence of a ferrule or when the ferrule is minimal, a rigid post (cast post and core or metallic prefabricated post) in general will have a high modulus of elasticity that will cause a high risk of radicular fracture (Fig 4-14). On the other hand, a flexible post (nonmetallic prefabricated

post) will have a low modulus of elasticity that will cause a risk of post fracture (Fig 4-15).

Fig 4-14 The presence of a ferrule with inadequate height in a maxillary premolar with a crown retained by a rigid cast post and core has resulted in a fractured root.

Fig 4-15 (a) A radiograph of a maxillary central incisor reveals that the prefabricated nonmetallic post has fractured. (b) The crown and broken post are shown. (c) Very little cervical tooth structure is available for retention of the crown.

Anatomical and Structural Limitations The practitioner who completed the endodontic treatment is ideally suited to identify characteristics of the pulp chamber, root canal anatomy, and completed endodontic restoration that should be reviewed before a post and core are placed. These

characteristics include the presence and extent of dentinal craze lines; identification of teeth where further root preparation (beyond that needed to complete endodontic instrumentation) will result in less than 1 mm of remaining dentin or a post diameter greater than one-third the root diameter area; information regarding areas where the remaining tooth structure is thin; and the point at which significant root curvature begins.

Craze lines Craze lines in dentin are areas of weakness where further crack propagation may result in root fracture and tooth loss (Fig 4-16). Obturation of the root canal system and post space preparation can cause pressure in the root canal walls113, 114 and induce craze lines.115, 116 These defects may have the potential to develop into cracks and cause vertical root fractures.117, 118 Several factors can contribute to the formation of these craze lines: tooth anatomy, 119 post cementation, root canal preparation,115, 120, 121 and the use of ultrasonics to remove broken or separated instruments.122 The patient should be informed of their presence with appropriate chart documentation of crack location. It is prudent to avoid post placement, if possible, in favor of a restorative material core. If a post is required, it should passively fit the canal, and the definitive restoration should entirely encompass the cracked area, whenever possible, by forming a ferrule.

Fig 4-16 The craze line in the pulpal floor of a mandibular left first molar could propagate and cause root fracture.

Dentin thickness after endodontic treatment Following normal and appropriate endodontic instrumentation, teeth can possess less than 1 mm of dentin, indicating that there should be no further root preparation for the post. When these teeth are encountered, it is better to fabricate a post that fits the existing morphologic form and diameter than to prepare the root further to accept a prefabricated type of post. This characteristic is one of the primary indications for use of a custom cast post and core. One study63 determined that maxillary and mandibular canines, maxillary central and lateral incisors, and the palatal root of maxillary first molars possessed more than 1 mm of dentin after endodontic cleaning and shaping. All other teeth had roots with less than 1 mm of remaining dentin following endodontic treatment. Mandibular premolars with oval or ribbon-shaped canals should not be subjected to any preparation of the root canal for a post because such treatment will result in less than 1 mm of dentin.63 It has been shown that only five teeth have more than 1 mm of dentin wall thickness remaining after conventional endodontic therapy123: (1) maxillary central incisors, (2) maxillary lateral incisors, (3) maxillary canines, (4) mandibular canines, and (5) maxillary first molars (palatal root only).96 According to Ouzounian and Schilder123 all other teeth had less than 1 mm of dentin thickness after endodontic cleaning and shaping. A study of maxillary first premolars with posts prepared to a depth equal to the clinical crown height determined that 1 mm of residual dentin thickness was only present when a 0.7-mm-diameter rotary instrument was used to prepare the post space.61 It has been shown that any amount of root canal preparation in mandibular first and second molars following endodontic treatment decreases the residual dentin thickness to less than 1 mm.124 Additionally, a study of residual dentin thickness in the distal root of 26 mandibular molars after endodontic treatment alone determined that the canal wall on the furcal side of the root was less than 1 mm thick 82% of the time and less than 0.5 mm thick 17.5% of the time.62 Preparation of the mesial root canals in mandibular molars and the facial root canals in maxillary molars can result in perforation or leave only thin areas of remaining dentin. Based on measurements of residual dentin thickness, it is recommended that posts not be placed in these roots if possible.

Root curvature When root curvature is present, post length must be limited to preserve remaining dentin, thereby helping to prevent root fracture or perforation. Root curvature occurs

most frequently in the apical 5 mm of the root. Therefore, if 5 mm of gutta-percha is retained apically, curved portions of the root are usually avoided. As discussed previously, molar posts should not exceed 7 mm in length in the primary roots because of the potential for perforation due to root curvature and developmental root depressions (Fig 4-17). Molar roots are frequently curved, and the post should terminate at the point where substantive curvature begins.

Fig 4-17 Given the curvature of the distal canal, the post space should not exceed 7 mm from the orifice of the canal. (Courtesy of Dr Axel Yabroudi, Phoenix, AZ.)

Root selection for multirooted teeth Premolars When posts and cores are needed in premolars, posts are best placed in the palatal root in the maxillary premolar and the straightest root in any other premolar that has two roots. The buccal root could be prepared to a depth of 1 to 2 mm and serve as an antirotational lock, if needed. Molars When posts and cores are needed in molars, posts are best placed in roots that have the greatest dentin thickness and the smallest developmental root depressions. The most appropriate roots (the primary roots) are the palatal roots in maxillary molars (Fig 4-18a) and the distal roots in mandibular molars (Fig 4-18b). The facial roots

of maxillary molars and the mesial roots of mandibular molars should be avoided if at all possible. If these roots must be used in addition to the primary roots, then the post length should be short (3 to 4 mm), and a small-diameter instrument should be used (no larger than a No. 2 Peeso instrument, which is 1.0 mm in diameter).

Fig 4-18 (a) The palatal canal is the only suitable canal for a post space in a maxillary molar. Note the straight and large post space of the palatal canal compared with the mesiobuccal and distobuccal canals. (b) The distal canal is the only suitable canal for a post space in a mandibular molar. Note the curved, small canals of the mesial roots with thin dentin. (Courtesy of Dr Axel Yabroudi.)

Summary Many factors affect the outcome when endodontically treated teeth are restored, including post length, post diameter, canal preparations, and ferrule effectiveness. When crowns are placed on endodontically treated teeth, they should encompass 2 mm of tooth structure apical to the core and around the entire circumference of the tooth whenever possible because crown ferrules increase the resistance of teeth to fracture. The ferrule is more effective if it is uniform and should be present regardless of the type of post used.

Acknowledgment The authors would like to thank People’s Medical Publishing for granting permission to reuse some of the material published in their chapter of Ingle’s Endodontics, ed 6.125

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associated with three obturation techniques. J Endod 1994;20:32–37. 116. Sathorn C, Palamara JE, Messer HH. A comparison of the effects of two canal preparation techniques on root fracture susceptibility and fracture pattern. J Endod 2005;31:283–287. 117. Wilcox LR, Roskelley C, Sutton T. The relationship of root canal enlargement to finger-spreader induced vertical root fracture. J Endod 1997;23:533–534. 118. Shemesh H, van Soest G, Wu MK, Wesselink PR. Diagnosis of vertical root fractures with optical coherence tomography. J Endod 2008;34:739–742. 119. Wu MK, van der Sluis LW, Wesselink PR. Comparison of mandibular premolars and canines with respect to their resistance to vertical root fracture. J Dent 2004;32:265–268. 120. Shemesh H, Bier CA, Wu MK, Tanomaru-Filfo M, Wesslink PR. The effects of canal preparation and filling on the incidence of dentinal defects. Int Endod J 2009;42:208–213. 121. Bier CA, Shemesh H, Tanomaru-Filfo M, Wesslink PR, Wu MK. The ability of different nickel-titanium rotary instruments to induce dentinal damage during canal preparation. J Endod 2009; 35:236–238. 122. Madarati AA, Qualtrough AJ, Watts DC. Vertical fracture resistance of roots after ultrasonic removal of fractured instruments. Int Endod J 2010;43:424– 429. 123. Ouzounian ZS, Schilder H. Remaining dentin thickness after endodontic cleaning and shaping before post space preparation. Oral Health 1991;81:13– 15. 124. Isom TL, Marshall JG, Baumgartner JC. Evaluation of root thickness in curved canals after flaring. J Endod 1995;21:368–371. 125. Goodacre CJ, Baba NZ. Restoration of endodontically treated teeth. In: Ingle JI, Bakland LK, Baumgartner JG (eds). Ingle’s Endodontics, ed 6. Hamilton, ON: BC Decker, 2008:1431–1473.

Cementation of Posts and Provisional Restoration Loss of retention has been reported as the most common complication of intraradicular posts.1 While post length and the presence of a ferrule2 play a primary role in ensuring retention of a post, it is also important to capitalize on the mechanical properties of the luting agent and to ensure the best cementation technique.

Selection of Luting Agents Ideally, cements should be biocompatible, offer resistance to dissolution in oral fluids, and possess favorable physical and mechanical properties. Properties such as tensile strength, compressive strength, and adhesion to dentin are important, and the potential for plastic deformation, water sorption, and microleakage are also critical factors that must be considered.3 Cements used for posts should have a relatively long working time to facilitate manipulation of the cement and a short final setting time to permit tooth preparation relatively soon after cementation of the post. Box 51 describes the desirable properties of cements for posts.

Although different types of posts require different cementation protocols, the objective remains to spread an ample amount of cement around the post space to cement the post to the dentin. Selection of the appropriate cement requires knowledge of the physical, mechanical, and handling properties of the available cements. Although most contemporary cements could be considered sufficient for cementation, differences do exist among the cements with regard to indications for their use (Table 5-1).

Zinc phosphate cement Zinc phosphate cement is manufactured as a powder (primarily zinc oxide with 10% magnesium oxide) and a liquid (phosphoric acid). This cement is the oldest among the cements currently in use, and it has a long history of success when used to cement various types of dental restorations. It is cost-effective and is still indicated for dental cementation. It can certainly be used for luting post and core restorations.3, 4 The primary disadvantages of zinc phosphate cement are its solubility in oral fluids and its lack of any true adhesion to tooth structure.3 If mixed correctly, zinc phosphate cement has a long working time and short setting time that make it favorable for cementing posts. There is adequate time for the cement to be applied to the post and for the cement to be placed in the canal without the risk of premature setting and the possibility of incomplete seating of the post. This cement should be mixed differently from other cements. Because the setting reaction of zinc phosphate cement is exothermic, this exothermic heat must be

dissipated during mixing to ensure a long working time. The cement should be mixed on a thick, cold glass slab. The powder should be divided into multiple portions and introduced incrementally into the liquid.5 When retention of posts cemented with zinc phosphate cement is compared with retention of those cemented with resin cements, studies have reported contradictory results. No difference was reported in one study. 6 Resin cement was reported to be more retentive in another study, 7 and three other studies8–10 recorded that zinc phosphate cement had significantly better retention than did resin cements.

Polycarboxylate cement The powder content of polycarboxylate cement, similar to that of zinc phosphate cement, is primarily zinc oxide, and the acid used in the liquid is polyacrylic acid. This cement was developed to allow a true chemical adhesion to tooth structure.11, 12 This cement has been reported to be weaker than glassionomer and zinc phosphate cements when used to cement posts.8 The cement also has been reported to undergo plastic deformation under cyclic loading,13 which is undesirable and could result in post dislodgment because of fatigue failure of the cement film.

Glass-ionomer cement Glass-ionomer cement possesses favorable qualities such as chemical adhesion to tooth structure14 and fluoride release15–17 along with adequate compressive and tensile strengths.13 It is relatively easy to use and is cost-effective. Many dentists prefer this cement because of its ease of use. Although this cement has been reported to release fluoride, cariostatic properties in dentin as a result of this fluoride release have not been definitively proven.18 One disadvantage of glass-ionomer cement is its sensitivity to moisture in the early setting period.19 The restoration must be clear of oral fluids initially. Another disadvantage of this cement is its peculiar setting reaction. This cement requires several days20 or even several weeks21 to reach its maximal strength. Any recontouring of the core with a dental handpiece soon after cementation could result in weakening of the incompletely set cement and possibly lead to retentive failure of the post over time.3

Resin cement

Resin cement Resin cements are recommended for cementation of modern posts such as fiberreinforced resin posts. The literature does not favor the total-etch technique over the use of a selfadhesive resin cement when these posts are cemented.22 Studies have recorded different retentive values among resin cements.23, 24 These cements are costly and could be significantly more expensive to use on a routine basis.

Resin-modified glass-ionomer cement This cement is a hybrid of resin and glass-ionomer cements. Unlike conventional glass-ionomer cement, this cement pro vides improved early strength and lower solubility. This behavior is attributed to the resin polymerization that precedes the slower acid-base reaction.25 This type of cement is relatively easy to use and has become very popular among dentists for cementation of dental restorations. This cement leaches fluoride, similar to conventional glassionomer cement. Nevertheless, objective proof of any cariostatic effect from this leached fluoride is lacking.26 Earlier generations of this cement tended to undergo expansion over time as a result of imbibition of water. 27, 28 Anecdotally, it has been suggested that this expansion could cause root fracture if the cement is used to cement posts and cores.3, 4 Newer generations are less prone to expansion from water sorption but still absorb considerable amounts of water. 29 Consequently, although it has never been clearly demonstrated that this cement can lead to root fracture, it would be prudent to avoid this class of cement for cementation of posts.

Advantages and disadvantages of various classes of cement Each class of cement has advantages and disadvantages. Table 5-2 summarizes and compares the favorable and less favorable features of the available types of cement.

Recommendations based on the type of post Although various cements can be used with cast posts and cores and prefabricated metal posts (see Table 5-1), the authors recommend zinc phosphate cement for these posts. When traditional principles have been followed and a ferrule is present, this cement provides more than adequate retention. It has very favorable handling characteristics, including a long working time and relatively short setting time, unlike glass-ionomer cement. Unlike resin cement, its setting reaction is unaffected by eugenol, and it is highly cost-effective. Unlike polycarboxylate cement, zinc phosphate cement has not been reported to undergo plastic deformation. Fiber-reinforced resin posts should be cemented with resin cement, either conventional or self-adhesive. Zirconia posts can be cemented with any cement, and the authors recommend zinc phosphate cement. If adhesion to the radicular dentin is desired, a self-adhesive resin cement should be used.

Effect of Endodontic Sealer on Retention of Posts Endodontic sealers must fill the voids that exist between the gutta-percha and the canal walls and into the apex. There are three main types of sealers: zinc oxide– eugenol–based, calcium hydroxide–based, and resin-based.30 Zinc oxide–eugenol– based sealer is more biocompatible than resinbased sealer and is less biodegradable than the calcium hydroxide–containing sealer. 30 Because of these qualities, along with its long history of success, zinc oxide–eugenol sealer tends to be the sealer of choice among most endodontists. Nevertheless, there are concerns with regard to the setting reaction of luting agents, especially resin cements, placed in a canal that has been obturated previously with a eugenol-containing sealer. It is well known that eugenol causes inhibition of the polymerization reaction of

dental resins by reacting with the free radicals that initiate the polymerization of the resin.31 The literature, however, has contradictory conclusions on the topic of luting posts in canals where a zinc oxide–eugenol–containing sealer has been used for obturation. Although eugenol-containing dental materials have been known to have a negative effect on dentin bonding procedures, some studies of their effects on cementation of posts show a negative effect,7, 32–34 while others show no decrease in bond strength.9, 35 One study concluded that, regardless of the type of sealer used, any residue of sealer can decrease retention with resin cements.36

Cementation Techniques Intraradicular disinfection and surface treatment Various techniques have been advocated for intraradicular disinfection and surface treatment of the dentin, including mechanical methods, chemical methods, or a combination of both7, 37–40 (Boxes 5-2 and 5-3). The discussion on the smear layer offers further analysis of these treatment recommendations.

Smear layer The process of cleaning and shaping the root canal system results in a smear layer composed of debris that occludes the dentinal tubules.41 Irrigation with solutions that have the ability to dissolve the smear layer has been suggested as a prudent step prior to endodontic obturation; this technique is thought to lead to better sealing of the dentin.30 Nevertheless, the process of preparing the canal for the post creates a new smear layer. This new smear layer must be removed to improve bonding to dentin.42–44 Multiple methods have been described for the treatment of the smear layer. A study on self-adhesive resin cements reported that treating the smear layer with ethylenediaminetetraacetic acid (EDTA) and phosphoric acid improved retention of fiber posts.45 Sahafi and Peutzfeldt46 recommended the use of diamond-coated rotary instruments to increase the roughness of the dentin and reported that this technique resulted in better bond strength to intraradicular acid, the main constituent of polycarboxylate cement liquid, has the ability to remove the smear layer. 47 This liquid can also be used to treat the radicular dentin prior to cementation of posts. Sodium hypochlorite (NaOCl) can disinfect the canal and remove pulpal remnants, and EDTA can remove the smear layer. These two materials are traditional irrigants and have been very effective. A new product that is a mixture of 3% tetracycline (doxycycline), 4.25% citric acid, and 0.5% polysorbate-80 detergent (MTAD; BioPure, Dentsply) has been used as both an irrigant and an antibiotic. In addition, MTAD has been recommended to treat the smear layer.48

Radicular dentin and resin bonding When attempting to bond a post to radicular dentin, studies have shown that

radicular dentin can behave differently from either coronal dentin or when different regions within the post space are compared. Yoshiyama et al 49 reported that the resin-infiltrated zone (hybrid layer) formed in radicular dentin was thinner than the resin-infiltrated zone observed in coronal dentin when All-Bond 2 cement (Bisco) was used. Nevertheless, this thinner infiltration zone did not appear to affect retention of the post. Soares et al24 reported that RelyX ARC cement (3M ESPE) demonstrated significantly less bond strength to radicular dentin when measured incrementally in an apical direction. Zhang et al45 measured the retentive strengths of posts in different regions within the post space (apical and coronal) and recorded significantly different retentive strengths, depending on the location within the post preparation and the type of surface treatment of the radicular dentin. Calixto et al,50 using five different resin cements, measured the bond strength of fiberreinforced posts at different regions within the post space. Pushout tests revealed that bond strength was reduced in the apical portion of the post space for all cements. Based on the results of these studies, it appears that the process of etching and bonding to radicular dentin is more technique sensitive than etching and bonding to coronal dentin, and the quality of the hybrid layer and the resultant bond strength may be compromised, especially in the apical third of the canal.

Surface treatment of posts Cast metal posts should be airborne-particle abraded with 50-μm aluminum oxide particles. If the post is adjusted chairside, it should be airborne-particle abraded again prior to cementation. Airborne-particle abrasion with 50-μm aluminum oxide has been reported to significantly increase the retention of cemented cast metal posts.51 Different manufacturers recommend different surface regimens for fiberreinforced resin posts. Nevertheless, most manufacturers recommend surface treatment and cleaning with phosphoric acid, and some recommend silane application. There are a number of studies on surface treatment of fiber-reinforced posts, some with conflicting results. Monticelli et al52 reported no significant difference in bond strength of methacrylate resin–based fiber-reinforced posts conditioned with silane or with a combination of hydrofluoric acid and silane when compared with the bond strength of the control group (no surface treatment). One study evaluated the effect of treatment with alcohol (control group), hydrofluoric acid, phosphoric acid,

and hydrogen peroxide on the microsurface roughness of glass fiber and carbon fiber resin posts with scanning electron microscopy. 53 All experimental treatments, except treatment with phosphoric acid, increased the microroughness of the surfaces. A study by de Sousa Menezes et al54 reported improved retention for fiber-reinforced resin posts pretreated with 24% or 50% hydrogen peroxide. Amaral et al 55 reported no increase in bond strength for fiber-reinforced resin posts conditioned with either hydrofluoric acid or hydrogen peroxide. Airborne-particle abrasion of fiberreinforced posts has been reported to damage the surface.56 Zicari et al57 reported that many variables, including the type of fiber post, the resin cement used, and the surface treatment of the post, influenced the cement-post interface, making clinical guidelines difficult to define. It appears that surface treatment is a controversial topic, and perhaps any benefits of surface conditioning could become ineffective with aging. Although definitive guidelines cannot be specified based on the current state of knowledge, it is suggested that clinicians follow the manufacturer’s instructions with regard to surface treatment of the post.

Cementation process For optimal retention of the post, the cement should fill the space between the post and the dentin without voids. If cement is placed on the post only, as soon as the liquid cement contacts the orifice of the post preparation, air is trapped deeply within the post channel. As the post is seated, this entrapped air must travel through the liquid cement, producing multiple voids in the cement film that will compromise the mechanical properties of the cement58 (Fig 5-1). The literature advocates application of the cement to the post and also placement of cement in the canal with a lentulo spiral or a fine tube or pipette.59–61 Fakiha et al62 reported that the use of a pipette combined with a lentulo spiral to introduce the cement in the canal produced the best retention with zinc phosphate cement.

Fig 5-1 If cement is placed only on the post, as it is seated (large arrow) the air trapped within the post preparation travels through the liquid cement (small arrows), producing multiple voids. (Reprinted from Morgano and Brackett3 with permission.)

Some manufacturers of resin cements, such as 3M ESPE (manufacturer of RelyX Unicem cement), caution against the use of a lentulo spiral to introduce their cement into the post preparation because they claim that this procedure will accelerate the setting reaction and may lead to incomplete seating of the post.

Cementation of a cast post and core with zinc phosphate cement The armamentarium required for fitting and cementation of a cast post and core with zinc phosphate cement is shown in Fig 5-2. A step-by-step description of the fitting and cementation processes follows:

Fig 5-2 Armamentarium for fitting and cementing a cast post and core with zinc phosphate cement: cement spatula, locking dressing pliers, paper points, cotton rolls, cotton pellets, interproximal brush, polyacrylic acid liquid, zinc phosphate cement, silicone disclosing medium and wax pencil (red), glass slab, straight pipette, high- and lowspeed handpieces, lentulo spiral, and chamfer diamond rotary instrument.

1. Inspect the post under magnification to detect any positive casting defects (nodules) that may have occurred as a result of entrapment of minute air bubbles during the investing process (Figs 5-3a and 5-3b). Remove any nodules discovered.63 2. Carefully remove any provisional cement that has entered the post space. 3. Coat the post, which has been airborne-particle abraded with 50-μm aluminum oxide, with a silicone disclosing medium, and seat the post gently in the post preparation. Allow the disclosing medium to set. 4. Remove the post from the post preparation. Mark any areas where the metal shows through the silicone disclosing medium with a red pencil (Fig 5-3c). 5. Remove the silicone disclosing medium (Fig 5-3d). 6. With a diamond rotary instrument, adjust the areas of the post marked in red (Fig 5-3e). 7. Reapply the silicone disclosing medium and repeat steps one to four. After removal of the post from the post preparation, if the post is completely coated with set disclosing silicone without any portion of the post showing through, adjustments are complete. 8. After the post is adjusted and seats passively in the post preparation, repeat the airborne-particle abrasion process with 50-μm aluminum oxide. 9. Dip an interproximal brush into polyacrylic acid and apply the liquid to the post

preparation for 10 seconds to remove the smear layer (Fig 5-3f). 10. Use an irrigating syringe to rinse the walls of the post preparation with tap water for 30 seconds to remove the residual polyacrylic acid liquid (Fig 5-3g). 11. Dry the post preparation with paper points (Fig 5-3h). 12. Dispense zinc phosphate cement powder onto a thick, cold glass slab. Divide the powder into multiple portions- tions. Place 20 drops of cement liquid onto the slab. Incorporate a portion of the powder into the liquid. Mix the cement over a wide area of the glass slab for 20 seconds. Gradually incorporate additional powder into the cement mix until the cement reaches the desired consistency (Fig 5-3i). To evaluate the consistency, lift the liquid cement with the spatula from the slab; when the cement that has been lifted from the slab breaks at an inch, it is at the desired consistency (Fig 5-3j). The process of mixing the cement should be accomplished in approximately 1.5 minutes. 13. Scoop up cement into a straight pipette and occlude the large opening of the pipette with a cotton ball taken from a cotton roll (Fig 5-3k). 14. Insert the tip of the pipette to the most apical portion of the post preparation and inject cement into the canal, gradually withdrawing the pipette incisally in the canal until the post space is completely filled with cement (Fig 5-3l). 15. Insert a lentulo spiral into the liquid cement. Use a lowspeed handpiece to rotate the lentulo spiral clockwise within the cement to ensure adaptation of the cement to the walls of the post preparation (Fig 5-3m). 16. Coat the post with cement and gently seat the post into the post preparation. Allow the post to rebound and then gently reseat it. Repeat this procedure until the post seats passively without rebounding (Fig 5-3n). 17. Remove excess cement when it becomes brittle, approximately 10 minutes after the mixing has been completed (Fig 5-3o). 18. Fabricate a provisional restoration and cement it. 19. At the next visit, lightly prepare the core to blend it in with the apical tooth structure (Fig 5-3p).

Fig 5-3 (a) A nodule (arrow) is the result of a minute air bubble on the surface of the pattern during the investing process. (b) If the post is forcibly seated with the nodule (small arrow) in place, stresses can be generated in radicular dentin (large arrows); these stresses could predispose the tooth to vertical root fracture. (Reprinted from Morgano and Milot63 with permission.)

Fig 5-3 (cont) (c) Any areas where metal shows through are marked in red. (d) Silicone disclosing medium is removed. (e) Areas marked in red are adjusted with a diamond rotary instrument. (f) Polyacrylic acid is applied to the walls of the post preparation with an interproximal brush for 10 seconds. (g) Polyacrylic acid is rinsed from the post preparation with an irrigating syringe and tap water for 30 seconds. (h) The walls of the post preparation are dried with paper points. (i) Powder is gradually incorporated into liquid cement. Mixing time should be approximately 1.5 minutes. (j) When the cement string breaks at an inch, it is the desired consistency. (k) Cement is scooped into the pipette, and the large end of the pipette is occluded with cotton.

Fig 5-3 (cont) (l) The pipette is used to completely fill the post preparation with cement. (m) A lentulo spiral is used to ensure that the cement is well adapted to the walls of the post preparation. (n) The post is passively seated in the canal. (o) (p) The core has been lightly prepared with a diamond rotary instrument to blend the core with the cervical tooth structure.

Cementation of a fiber-reinforced resin post with selfadhesive resin cement Figure 5-4 displays the armamentarium required for cementation of a fiberreinforced resin post with self-adhesive resin cement and the subsequent placement of a composite resin core. The step-by-step process follows:

Fig 5-4 Armamentarium for cementing a fiber-reinforced composite resin post and fabricating a composite resin core: fiber post kit, high- and low-speed handpieces, side-cutting slow-speed drills, diamond rotary instruments, irrigation syringe, locking dressing pliers, paper points, cotton pellet and isopropyl alcohol, self-adhesive resin dualpolymerizing cement and applicator, 37% phosphate acid, dentin bonding agent, and composite resin.

1. Achieve adequate isolation by using rubber dam (preferred) or cotton rolls. 2. Remove the gutta-percha to the desired depth with a Gates Glidden drill so that the post will be as long as practical while maintaining 4 to 5 mm of apical guttapercha seal (Fig 5-5a). 3. Choose the smallest-diameter fiber post. If that size post seats to the required depth but is loose in the canal because of a mismatch in size, then select the nextlarger drill and post. Shape the post space with the selected drill (Fig 5-5b). 4. Insert the post into the prepared post space, ensuring that the post seats completely with the aid of a silicone stopper (Fig 5-5c). 5. Irrigate to disinfect the canal with 2.25% NaOCl. 6. Dry the post preparation with paper points. 7. Clean the surface of the post with a cotton pellet impregnated with alcohol (Fig 5-5d). No further surface treatment is recommended by the manufacturer. 8. Mark the length of the post to its desired length. 9. Cut the excess length of the post extraorally with a diamond disk. 10. Activate and mix the self-adhesive resin cement capsule in the mixing unit according to the manufacturer’s recommendations. 11. Connect the elongation tube to the already mixed capsule and inject the cement into the post space beginning at the full depth. Slowly withdraw the tip from the canal while injecting the cement, ensuring that the use a lentulo spiral because the

manufacturer advises against its use to avoid premature setting of the cement. 12. Coat the post with cement and insert the post into the post space with moderate pressure. 13. Stabilize the post in the post space. 14. Remove excess cement from around the post by using college pliers and a cotton pellet (Fig 5-5f). 15. Place the tip of the polymerization light on the incisal (or occlusal) surface of the post, parallel to its long axis, to ensure that the light travels through the post fibers and reaches the cement in the apical region. Apply the light for 40 seconds. Alternatively, allow 5 minutes for autopolymerization (Fig 5-5g). 16. Etch the remaining tooth structure with 37% phosphoric acid for 15 seconds (Fig 5-5h), rinse for 10 seconds, and blot dry. 17. Apply two coats of adhesive, air dry, and light polymerize for 10 seconds. 18. Incrementally add composite resin. 19. Prepare the core reconstruction with a rotary instrument to resemble a completecrown tooth preparation (Fig 5-5i).

Fig 5-5 (a) Gutta-percha is removed 4 to 5 mm short of the apex to prepare the post space. (b) A post drill is placed to its full depth. (c) A fiber post is tried in the post space to ensure that it seats passively and to the desired depth. (d) The post is wiped with alcohol. (e) Cement is injected into the post space at full depth with an elongation tip. (f) a cotton pellet. (g) The polymerization light is applied for 40 seconds. (h) The remaining tooth structure and post are acid etched. (i) Composite resin has been placed and then prepared with a diamond rotary instrument to form a core to accommodate a complete-coverage restoration.

Advantages of a ferrule Although the type of cement and the cementation technique used can affect the retention of a post, other factors also can profoundly influence the retention. The presence of an adequate ferrule plays a major role in reducing the potential for a post to become dislodged. When a ferrule is present, the crown surrounds cervical tooth structure apical to the margin of the core. Because much of the retention for a

complete crown is derived from the cervical one-third of the tooth preparation,64 when a ferrule is present the retention of the crown will not depend exclusively on the retention of the post but will rely heavily on the retentive form and surface area of the natural tooth structure apical to the core. When the margin of the crown and the margin of the core are at the same cervical level, all of the retention for the crown relies on the retention of the core, which depends on the retention of the post, and the post is more likely to become dislodged. Retention of any dental restoration is affected to a great degree by surface area. For retention of posts, length and surface area are the primary determinants of retention. Sorensen and Martinoff65 reported that the success rate of a tooth restored with a post and core is directly proportional to the length of the post. Longer posts not only are more retentive but also improve stress distribution within the radicular dentin.66, 67 Nevertheless, use of longer posts to increase retention has limitations because of root anatomy and the importance of maintaining 4 to 5 mm of apical guttapercha seal.68 A three-dimensional modeling software (SketchUp, Trimble) was used to calculate the surface area of a 1 × 10–mm parallel-sided post and a completecoverage tooth preparation on a premolar and a molar, each with a 2-mm occlusogingival height of remaining coronal tooth structure. The surface area calculations revealed that just 2 mm of height of coronal tooth structure provided the axial walls of a premolar tooth preparation with the same surface area as a 1 × 10– mm post; as expected, a molar preparation possessed more surface area, 1.5 times the surface area of the post. Although resin cements are indicated for fiber-reinforced resin posts, it has been suggested that resin cements can be used for all types of posts, including metal posts.69 Nevertheless, resin cements are expensive, and their manipulation is complex and technique sensitive. Also, a number of clinical studies have reported very high success rates for metal posts cemented with conventional cements.70–72 When posts are designed with adequate length, in the presence of an adequate ferrule, and the cementation technique prevents air entrapment in the cement film, the type of cement used is probably of limited importance. The existence of a ferrule is fundamental with any type of post or cement,70–73 and traditional principles of restoring pulpless teeth appear to be more important than the class of cement used in most situations.

Provisional Restoration of Endodontically Treated Teeth Provisional restorations maintain esthetics and occlusal function while they protect

the remaining tooth structure and soft tissues in the period leading to the delivery of the definitive restoration. These restorations should meet most standards of definitive restorations (Box 5-4); their longevity is the only difference.

Materials for provisional restorations Different materials can be used in the fabrication of provisional restorations, including acrylic and composite resins. Acrylic resins Acrylic resins are synthetic polymers containing acrylate groups. These polymers were first used in dentistry as denture base material and later were incorporated into restorative procedures. This class of resins constitutes the most commonly used material for custom-made provisional restorations.74, 75 The most commonly used acrylic resin in dentistry is polymethyl methacrylate (PMMA). Acrylic resins are supplied in the form of a powder and a liquid. The polymerization process begins with a liquid phase, converting to a thick gel, then to a putty, and finally to a rigid material. The polymerization process is exothermic and releases heat that can be uncomfortable for the patient. Because the amount of heat liberated is dependent on the amount of polymeric chains formed, more heat generation is expected in the fabrication of multiple or bulky units when the direct technique is used. This material undergoes shrinkage that accompanies the polymerization process. It is recommended that the provisional restoration be removed and reseated during the setting process to avoid its locking in place. One author suggested placing the material in room temperature water just before the final setting to slow the setting reaction and limit the amount of polymerization shrinkage.76 The liquid component has an offensive odor that can be objectionable to patients. There are reports of patients77–79 and dental professionals80 developing allergic reactions to acrylic resin monomer. Furthermore, Mickov et al 80 reported that latex

gloves are permeable to acrylic resin monomer and suggested that dental professionals who are allergic to acrylic resin monomer should use nitrile gloves instead of latex gloves. This material is easy to reline, repair, and polish. In addition, it is more costeffective than more contemporary composite resin provisional restorative materials. Composite resins Composite resins commonly used for the fabrication of provisional restorations can be bis-acryl or urethane dimethacrylate (UDMA) composite resins. Bis-acryl composite resin material is typically supplied in a two-paste form with an automixing mechanism and is either dual-polymerizing or autopolymerizing. Bisacryl composite resin provisional material usually gels in less than 1 minute and sets completely in approximately 5 minutes. UDMA materials are light polymerized, providing the clinician with more control of the setting reaction. Mechanical testing of bis-acryl composite resin provisional restorations revealed that they had higher flexural strength after mechanical aging than did PMMA provisional restorations. 81 However, these composite resin materials are more brittle82 and possess less fracture toughness than PMMA.83 Generalizing strength based on the type of material, however, is not valid because a study of 13 methacrylate and bis-acryl composite resin materials reported differences in flexural strengths based on the brand and not on the type of material.84 While there are many strength studies, strength is not the sole quality to be considered when a provisional restorative material is chosen. The marginal adaptation,85, 86 wear resistance,87 and color stability88–94 of bis-acryl composite resin and UDMA materials also are important factors that have been studied, including comparisons with acrylic resin materials. The marginal adaptation and wear resistance of composite resin provisional restorations have been shown to be comparable to those of laboratory-processed acrylic resin materials95 and superior to those of PMMA provisional restorations fabricated directly in the mouth. 96 Nevertheless, bis-acryl composite resin and UDMA materials have been reported to possess poorer color stability than PMMA.88–94 Two other disadvantages of composite resin provisional materials are difficulty in relining97 and weakening of the restoration if it is repaired.98 One major advantage of these composite resin materials over acrylic resin materials is ease of use. Also, unlike acrylic resins, these materials are odorless and do not cause patient discomfort as a result of heat generation during the setting process. Because of these properties, these materials tend to be more agreeable to patients.99

Fabrication of provisional restorations A variety of techniques can be used in the fabrication of provisional restorations. Multiple factors come into play when the technique to be used for their fabrication is selected (Table 5-3). Considerations include complexity, location in the dental arch, the patient’s parafunctional habits, and the length of service required. The most common techniques of fabrication involve the use of silicone matrixes, vacuumformed shells, and custom-prefabricated acrylic resin shells100 (Fig 5-6). Techniques also can be divided, based on the method of fabrication, into three groups: direct, indirect, and a combination of both (Table 5-4).

Fig 5-6 Methods for fabrication of provisional restorations include the use of a putty index (a), a clear plastic vacuum-formed matrix (b), and laboratory-processed crown shells that are relined in the mouth (c).

A putty index or a clear shell can be used, along with acrylic resin or composite resin, to fabricate the provisional restorations directly on the tooth preparations. Direct fabrication of provisional restorations is recommended for single units and prostheses of up to four units.101 Indirect provisional restorations can be custom made in the dental laboratory from an impression of the prepared teeth. These restorations can be made of acrylic or composite resin. The indirect technique reduces chair time, eliminates heat formation, and limits the exposure of oral tissues to monomer. In addition, because the fabrication is accomplished in the laboratory, various improvements can be achieved, such as metal reinforcement for higher strength and customized staining for enhanced esthetics.75, 102 The indirect technique can only be used after tooth preparations have been completed, limiting its use. Therefore, a combination of an indirectly fabricated provisional restoration over an approximated preparation on the cast with a subsequent relining procedure in the mouth is more practical. A common indirect/direct technique involves the fabrication of a heat-processed shell that is later relined in the mouth after tooth preparation. If long-term use of the provisional restoration is expected, this technique provides better color stability and wear resistance when compared with directly fabricated provisional restorations.100 This method can save chair time, but the primary disadvantage is the extra laboratory cost.

Computer-aided design/computer-assisted manufacture Dental milling technology of substructures was developed in the 1980s, but recent developments in complete-contour milling have sparked interest in computer-aided design/ computer-assisted manufacture (CAD/CAM) of provisional restorations.

Current commercially available materials are marketed in two forms: blocks and disks of PMMA. Blocks such as Telio-CAD (Ivoclar Vivadent) and CAD-Temp (Vita Zahnfabrik) can be used for single units and prostheses of up to seven units, while disks are indicated for completearch provisional restorations. Newer blocks have been developed with different layered shades for improved esthetics. There are limited studies on CAD/CAM provisional restorations. However, most commercially available blocks and disks are composed of PMMA, which has been extensively studied. Alt et al 103 fabricated provisional fixed partial dentures from PMMA and bis-acryl composite resin blocks and compared flexural strength to manually fabricated PMMA and bis-acryl composite resin restorations. They reported that, regardless of the type of material used, CAD/CAM fabricated restorations were stronger. CAD/CAM provisional restorations are an alternative to traditional laboratoryfabricated acrylic resin provisional restorations,104 but further advances in this technology are necessary to improve the practicality and cost-effectiveness of this approach before it can be recommended to replace conventional methods of fabrication.

Luting of provisional restorations Provisional luting agents are cements with relatively weak mechanical properties that ensure retrievability. Nevertheless, these cements must offer resistance to dissolution in oral fluids and maintain an adequate marginal seal.105 Because it is paradoxical to expect a cement to possess adequate sealing ability and resistance to dissolution while not expecting an increase in its mechanical properties that would compromise retrievability, these cements tend to be a compromise among these competing requirements. Therefore, to overcome problems that can occur with marginal leakage, especially with long-term use of a provisional restoration, these restorations should be removed frequently and recemented to prevent recurrent dental caries as a consequence of cement dissolution.100, 105 Most provisional cements are zinc oxide–based materials. Some of these formulations contain eugenol. Eugenol has been claimed to produce a sedative effect on vital pulpal tissue106 but also has been studied for possible inhibition of resin polymerization, affecting the behavior of dentin bonding agents. Contradictory conclusions have been drawn in the literature relative to the effects of eugenol on dental resin polymerization. Some studies107–111 reported no effect, while others showed a decrease in bond strength to dentin.112, 113

Regardless of the effect of eugenol, it is recommended that the dentinal surface be thoroughly cleaned of any remnants of provisional cement and residual eugenol if zinc oxide–eugenol cement has been used. Cleaning methods include the use of hand instruments,112, 113 pumice,111 airborneparticle abrasion,107 and etching with phosphoric acid.114 However, the effectiveness of these methods can be variable, and the use of hand instruments alone is the least recommended method for removal of eugenol-containing cements.112, 113

Special considerations for endodontically treated teeth Principles of provisional restoration for teeth with vital pulps apply to endodontically treated teeth also, with some differences. When a cast post and core is used, the post should be cemented as soon as possible after the post preparation to avoid the problem of coronal leakage.115 Therefore, the goal is to place a provisional restoration that will function for several days, then to cement the post and core, and then to place a second provisional restoration that can be expected to function for a duration of a number of days to as long as several months.

Technique for provisional restoration of a tooth receiving a cast post and core The armamentarium required to fabricate a provisional crown and temporary post is shown in Fig 5-7. A step-by-step description of this technique, including the use of a polycarbonate crown and autopolymerizing acrylic resin, follows:

Fig 5-7 Armamentarium for fabricating a provisional post and crown: autopolymerizing acrylic resin, silicone mixing bowls, cement spatula, preformed polycarbonate crown, paper clip, hard wire cutter, and bird beak pliers.

1. Prepare the endodontically treated tooth to receive a cast post and core and crown (Fig 5-8a). 2. Cut a paper clip with a wire cutter, ensuring that approximately 3 mm of the temporary post is protruding from the preparation. Remove the post from the tooth and create a loop using bird beak pliers. Replace the post in the post space (Fig 5-8b). 3. Select a polycarbonate crown of suitable size. Try the preformed crown on the preparation. Adjust the marginal extensions, proximal contacts, and occlusal contacts. 4. Mix autopolymerizing resin. When the material reaches the doughy state, place it in the prefabricated crown. 5. While the temporary post is secured in the post space, place the polycarbonate crown on the preparation. 6. After polymerization, remove the crown. The post should be securely attached to the crown. 7. Finish and polish the crown (Fig 5-8c). 8. Mix the temporary cement and apply it to the intaglio surface of the crown. To simplify the cleanup process when the definitive post and core is cemented, do not apply the cement on the middle and apical portions of the temporary post.

Fig 5-8 (a) Space for a cast post and core is prepared. (b) A temporary post is in place, ready to be picked up with acrylic resin. (c) A polycarbonate crown relined with autopolymerizing acrylic resin is connected to the temporary post.

Summary There is no universal material or technique that is suitable in all clinical situations. Clinicians must incorporate their knowledge of biomaterials and their clinical judgment to select the best combination of materials and techniques. Although new materials are being introduced continuously, the material requirements for mechanical, physical, and handling properties remain unchanged.

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Tooth Whitening and Management of Discolored Endodontically Treated Teeth Tooth whitening has become a popular procedure in dentistry, largely due to patients’ increasing demand for esthetic treatments. While the terms whitening and bleaching are often used interchangeably in both the literature and clinical practice, bleaching is a process involving an oxidative chemical that alters the lightabsorbing or light-reflecting nature of a material structure, increasing its perceived whiteness. Therefore, tooth bleaching, as defined by the International Organization for Standardization, is the “removal of intrinsic or acquired discolorations of natural teeth through the use of chemicals, sometimes in combination with the application of auxiliary means.”1 On the other hand, whitening is a process, regardless of the means used, that results in the material becoming similar in color to a preferred or standard white. In dental practice, mechanical approaches, such as polishing and brushing with abrasive-based prophylactic pastes and toothpastes, are used to remove surface stains, consequently providing a whitening effect. However, tooth whitening commonly involves the use of peroxide compounds, which achieve the whitening effect through bleaching mechanisms. Depending on the etiology of tooth stains, either extracoronal or intracoronal bleaching, or both, may be utilized to correct the tooth color. This chapter reviews and discusses the etiology of tooth stains as well as the materials, techniques, and management of tooth bleaching.

Etiology of Tooth Discoloration

Etiology of Tooth Discoloration Tooth discoloration is caused by stains that may be extrinsic, intrinsic, or a combination of both.2, 3 In general, tooth discoloration is the major reason that whitening treatments are considered.

Extrinsic tooth stains Extrinsic tooth stains are most commonly caused by various foods and beverages, including coffee, tea, red wine, and those with natural and artificial coloring agents. Oral hygiene products such as colored mouthrinses may also stain tooth surfaces. It is common knowledge that tooth stains are associated with the use of tobacco products. Varieties of chromogenic oral microorganisms are also capable of producing pigment molecules and consequentially responsible for tooth stains. A recent publication reported a case of blue tooth staining that was caused by Pseudomonas aeruginosa, a bacterium usually implicated in chronic pulmonary infections.4 Certain dental materials and inappropriate operating techniques can be the origin of tooth stains. An amalgam restoration not only has its inherent dark metallic color but also may produce colored corrosion products over time to stain the restored tooth. It was reported that extended tooth bleaching with a gel of 10% carbamide peroxide caused green staining of the tooth-amalgam interface.5 With composite resin restorations, the restoration itself may become discolored with time; furthermore, microleakage, if it exists, attracts extrinsic stains and consequently causes tooth discoloration. Open margins allow stains to enter the interface between the restoration and the tooth structure and discolor the underlying dentin. Another common cause of tooth discoloration is the incomplete removal of remnants of obturating materials and sealers containing metallic components in the pulp chamber during endodontic procedures, often resulting in dark discoloration of the tooth.5–7 Phenolics or iodoform-based medicaments sealed in the root canal and chamber are capable of causing internal staining of dentin. Direct contact of such a medicament with dentin, especially for a long period, allows its penetration and oxidation, resulting in discoloration of the dentin. Tissue remains left in the pulp chamber as a result of inappropriate endodontic procedures can disintegrate gradually and consequently cause tooth staining. Therefore, pulp horns must always be included in the access cavity to ensure removal of pulpal remnants and to prevent retention of sealer in future procedures.8

Intrinsic tooth stains

Intrinsic tooth stains Intrinsic tooth stains can be caused by a number of etiologic factors, including aging, calcific metamorphosis, intrapulpal hemorrhage, medications such as tetracyclines, pulpal necrosis, and certain diseases or tooth defects. Aging With increases in age, enamel becomes thinner due to wear while dentin becomes thicker because of dentin apposition; such physiologic changes in tooth structure affect the optical properties of the tooth, resulting in progressive darkening of the tooth. In addition, enamel cracking, crazing, and wear tend to increase over time, consequently increasing the risk of cumulative extrinsic staining from food and beverages. Calcific metamorphosis Calcific metamorphosis is the result of pulpal responses to trauma that is characterized by rapid deposition of hard tissue within the root canal space, and it occurs most frequently in anterior teeth.9 The traumatic injury may cause disruption of blood supply and consequently the destruction of odontoblasts. The undifferentiated mesenchymal cells in the pulp replace the dead odontoblasts and rapidly form reparative dentin, resulting in changes of tooth translucency and an increase in yellowish or yellow-brown appearance. Intrapulpal hemorrhage Traumatic injury to a tooth often causes intrapulpal hemorrhage. Products produced in the lysis of erythrocytes, primarily iron sulfides, penetrate dentinal tubules, causing discoloration of the surrounding dentin (Fig 6-1). The severity of such staining depends on the nature of the injury; if the pulp recovers, the stain may gradually dissipate, and the original tooth color may be recovered. However, in certain cases calcific metamorphosis may occur, as already discussed. If the tooth trauma is severe and pulpal necrosis occurs, the discoloration will be persistent and tends to become more severe with time.

Fig 6-1 Maxillary right central incisor with intrinsic discoloration of the surrounding dentin caused by a hemorrhage. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Pulpal necrosis Pulpal necrosis can be caused by bacterial infection, mechanical or chemical irritation, and traumatic injuries to the pulp. The disintegration process of pulpal necrosis releases chromatic by-products that penetrate the dentinal tubules, causing discoloration of the surrounding dentin. The degree of discoloration directly relates to the duration of the necrosis; the longer the chromatic compounds are present in the pulp chamber, the greater the discoloration will be (Fig 6-2).

Fig 6-2 Posttraumatic discoloration of a maxillary left central incisor caused by pulpal necrosis. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Tetracyclines Tetracyclines are a group of broad-spectrum antibiotics that includes tetracycline and doxycycline. Tetracycline Etiology of Tooth Discoloration was used extensively during the 1950s and 1960s for prophylactic protection and for the treatment of mycoplasma, rickettsial infections, and chronic obstructive pulmonary disease. It was sometimes prescribed for daily intake over an extended period of time. Doxycycline is a semisynthetic tetracycline that was invented in the early 1960s and has subsequently been used clinically for treatment of acne, chronic prostatitis, pelvic inflammatory diseases, rickettsial infections, sinusitis, and dental infections, among other conditions; it is also used for prophylactic purposes prior to certain surgical procedures. It is now well known that, when ingested during tooth formation, tetracyclines are capable of causing severe, distinctive tooth discoloration. While tetracyclines are no longer used for prolonged periods, dentists still face the challenge of dealing with tooth discoloration in individuals who took them in childhood prior to the recognition of their ability to cause severe tooth stains.10–13 Depending on the type of tetracycline, the dosage, the duration of intake, and the individual’s age at the time of use, the tooth staining can be yellow, yellow-brown, brown, blue, or dark gray (Fig 6-3).

Fig 6-3 Tetracycline-discolored maxillary and mandibular teeth. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

The teeth are usually affected bilaterally and symmetrically in both arches, and the degree of staining corresponds to the time of drug exposure and tooth development periods. The discoloration of the affected teeth may be homogenous or in bands, depending on whether the ingestion was continuous or intermittent. Tetracycline stains can be classified into three groups according to their severity. 13 First-degree discoloration is light yellow, light brown, or light gray and occurs uniformly throughout the crown without banding. Second-degree discoloration is more intense but without banding. Third-degree discoloration is of high intensity and shows horizontal banding. The mechanisms of tetracycline staining of teeth remain to be fully elucidated. The assumption is that tetracyclines are bound to calcium, which is then incorporated in the hydroxyapatite crystal of tooth structure, especially in the dentin. Teeth with tetracycline stains possess a unique photonic characteristic; they appear fluorescent when exposed to the ultraviolet spectrum, which promotes the theory that staining is the result of formation of a reddish-purple oxidation by-product that discolors the teeth. Diseases and structural tooth defects Several systemic conditions or diseases may cause intrinsic tooth stains. For example, erythroblastosis fetalis may occur in the fetus or newborn due to Rh-

incompatibility factors, causing lysis of erythrocytes and subsequently incorporation of hemosiderin pigments in the forming dentin.14 With advances in prenatal and perinatal care, this type of tooth discoloration has become rare. Thalassemia and sickle cell anemia are capable of causing intrinsic blue, brown, or green discolorations of the teeth. Porphyria, a metabolic disease, may also cause red or brownish staining of primary and permanent teeth. Amelogenesis imperfecta may result in yellow or brown discolorations, and dentinogenesis imperfecta may produce brownish-violet, yellowish, or gray staining to the teeth. High fever during tooth formation can cause enamel hypoplasia with a banding-type surface discoloration of the teeth. Structural defects may form in teeth as a result of a variety of systemic or local conditions, and they may be present prior to the eruption of the tooth because of disturbances during enamel and dentin formation or after the eruption due to enamel demineralization. Enamel hypocalcification and decalcification are visible whitish or brownish discolorations on generally intact enamel surfaces. On the other hand, enamel hypoplasia is a group of defects in which the enamel is defective and porous. Enamel hypoplasia may be hereditary, such as that associated with amelogenesis imperfecta or hereditary hypophosphatemia, or a result of environmental factors such as infections, tumors, or trauma. Dental fluorosis, or mottled tooth, is a type of enamel hypoplasia caused by excessive exposure to fluoride during tooth formation, resulting in defects in mineralized structures, particularly in the enamel matrix.15–17 The severity of subsequent staining generally depends on the degree of hypoplasia, which is directly related to the amount of fluoride exposure during odontogenesis. Teeth are usually affected bilaterally and symmetrically, and they present with various degrees of intermittent white spotting, chalky or opaque areas, yellow or brown discoloration, and, in severe cases, surface pitting of the enamel. Defects in tooth structure may alter the optical properties of the tooth, leading to its perceived discoloration. The porous and rough surface of the defective enamel also attracts extrinsic stains present in the oral cavity, aggravating the staining problem.

Tooth Bleaching with Peroxides Tooth bleaching, whether extracoronal or intracoronal, is not a new dental procedure. In-office bleaching of vital teeth has been a dental procedure for more than a century; however, at-home extracoronal tooth bleaching was not available until 1989, when it was introduced by Haywood and Heymann.18–20 With its

demonstrated efficacy, low cost compared to in-office bleaching, and the convenience of self-application by the user, at-home bleaching quickly gained popularity and has now become an integrated procedure in esthetic dentistry. 21 Intracoronal bleaching has also been a routine procedure in dental practice for more than 50 years.22–24 Nowadays, in addition to the extracoronal bleaching provided by dental professionals, over-the-counter (OTC) and infomercial at-home bleaching products are available directly to consumers, and they can be applied with a custom or preformed tray, a brush, or a strip. In recent years, tooth bleaching similar to inoffice procedures but performed in nondental settings, such as those offered at mall kiosks or spa and cruise ships, has become available.25

Materials for tooth bleaching Current tooth bleaching materials, whether for in-office or at-home use and for both extracoronal and intracoronal procedures, almost exclusively incorporate peroxide compounds as the active ingredient; carbamide peroxide and hydrogen peroxide (H2O2) are the most common compounds used for extracoronal bleaching, and sodium perborate is the most common compound for intracoronal procedures.19–25 Both carbamide peroxide and sodium perborate decompose in an aqueous medium to release hydrogen peroxide, which, therefore, is the true active ingredient of the peroxide-based bleaching materials. Attempts have been made to introduce at-home whiteners that claimed to contain no peroxide; however, such products did not gain acceptance because of the lack of evidence for their efficacy and controversy over their nonperoxide claim.20, 26 Carbamide peroxide Carbamide peroxide (CH6N2O3), also known as urea hydrogen peroxide , exists in the form of white crystals or a crystallized powder. Chemically, carbamide peroxide is composed of approximately 3.5 parts H2O2 and 6.5 parts urea, so that a bleaching material of 10% carbamide peroxide contains approximately 3.5% H2O2. It is mostly used in at-home bleaching materials with concentrations ranging from 10.0% to 30.0% (equivalent to approximately 3.5% to 10.5% H2O2); however, those containing 10.0% carbamide peroxide appear to be the most common. Bleaching materials containing carbamide peroxide usually also include glycerin or propylene glycol, sodium stannate, phosphoric or citric acid, and flavor additives. In some preparations, carbopol, a water-soluble polyacrylic acid polymer, is added as a thickening agent. Carbopol also prolongs the release of

active peroxide and improves shelf life. Sodium perborate Sodium perborate (NaBO3) is a white, odorless, watersoluble powder available as a monohydrate, trihydrate, or tetrahydrate. The monohydrate and tetrahydrate forms are commonly used, with H2O2 content theoretically at about 34% and 22%, respectively. 27–29 Sodium perborate is stable when dry; however, in the presence of acid, warm humid air, or water, it decomposes to form sodium metaborate, H 2O2, and nascent oxygen.8 In dentistry, sodium perborate is primarily used for intracoronal bleaching of teeth discolored by previous endodontic treatment. Commonly used sodium perborate preparations are alkaline, and their pH depends on the amount of H2O2 released and the residual sodium metaborate.28 Their bleaching efficacy is determined by the peroxide content of the preparation.29 Hydrogen peroxide H2O2 was identified as a chemical in 1818; since then it has been extensively investigated. It was first detected in human respiration in 1880, and in 1894 the well-known Fenton reaction was proposed. Peroxidase and catalase, which are two important enzymes in H2O2 metabolism, were found in 1898 and 1901, respectively. Shortly after the discovery of another enzyme, superoxide dismutase, in 1969, H2O2 was recognized as an important by-product in oxygen metabolism, and research efforts on the biologic properties of H2O2 have significantly increased since then.20 H2O2 is now known as a normal intermediate metabolite in the human body, with a daily production of approximately 6.48 g in the liver.20 Hydrogen peroxide is used for both in-office and at-home bleaching materials. Typically, the H2O2 concentrations of in-office bleaching products range from 25.0% to 40.0%, while at-home formulations contain 3.5% to 9.0% H2O2. However, in recent years there has been a trend of elevating the H2O2 concentration in at-home bleaching materials, and products of up to 15.0% H2O2 have now become available directly to consumers for home use. At high concentrations, such as those found in the in-office bleaching materials, H2O2 is caustic and burns tissues on contact. These materials must be handled with care to prevent contact with tissues during handling and bleaching treatment.

Biologic properties of H2O2 and safety concerns

One of the key characteristics of H2O2 is its capability of producing free radicals, including hydroxyl radicals that have been implicated in various stages of carcinogenesis. Oxidative reactions of free radicals with proteins, lipids, and nucleic acids are believed to be involved in a number of potential pathologic consequences; the damage caused by oxidative free radicals may be associated with aging, stroke, and other degenerative diseases.30, 31 The oxidative reactions and subsequent damage of cells by free radicals are believed to be the major mechanisms responsible for the observed toxicity of H2O2. Largely due to the known toxicity of oxidative free radicals, much of the safety concerns regarding tooth bleaching originates from the use of H2O2 in the materials. There have been concerns about potential systemic adverse effects if the bleaching material is ingested as well as local adverse effects on enamel, pulp, and gingiva because of the direct contact of the material with the tissues.19 The safety controversies over peroxide-based tooth bleaching have prompted not only scientific deliberations but also legal challenges to their use in dentistry.19, 20, 32, 33 With the available toxicologic data on H2O2 as well as the research on bleaching materials and the effects of exposure, safety concerns about most potential systemic toxicities associated with the use of 10% carbamide peroxide gels have largely diminished. The human body is equipped with various defensive mechanisms at the cellular and tissue levels to prevent potential damage of H2O2 to cells and to repair any damage sustained. Enzymes such as catalase, superoxide dismutase, peroxidase, and seleniumdependent glutathione peroxidase, which exist widely in body fluids, tissues, and organs, effectively metabolize H2O2.34 Human saliva also contains these enzymes. In fact, salivary peroxidase has been suggested to be the most important and effective defense in the human body against the potential adverse effects of H2O2.35 When the materials are used appropriately, the exposure to H2O2 from bleaching treatment is minimal. Intracoronal bleaching involves the use of a small amount of peroxide in the confined pulp chamber, with little direct exposure to the living tissues. During in-office bleaching, the soft tissues are adequately protected by barrier materials, and the gel is removed at the end of bleaching; little, if any, gel is left behind for possible ingestion. For at-home bleaching, the initial study estimated that the approximate dose of carbamide peroxide for each at-home application was 90 mg.18 This was confirmed in a later report in which the average amount of bleaching gel used clinically for 10 maxillary teeth (complete arch) was estimated at 502 mg per application.19 When both arches are being bleached, the average amount of gel used is approximately 1 g. For a bleaching gel containing 10% carbamide peroxide, the

exposure dose would be 100 mg per application. Dahl and Becher36 estimated that approximately 10% of the applied bleaching gel may be consumed during an application. Therefore, for an individual of 60-kg body weight who undergoes athome bleaching for both arches once daily, the exposure to the bleaching gel can be calculated at 1.67 mg/kg/d, and the exposure to carbamide peroxide through a gel containing 10% carbamide peroxide will be 0.167 mg/ kg/d. Carbamide peroxide contains approximately 35% H2O2; consequently, the estimated H2O2 exposure is 0.058 mg/kg/d, or 3.48 mg H2O2 per day for an adult of 60-kg body weight. A study of infants, juveniles, adults, and adults with impaired salivary flow found rapid decomposition of H2O2 in dentifrices.37 After 1-minute brushing with 1-g dentifrice, less than 2% of the prebrushing dose of H2O2 (30 mg) was detectable in the oral cavity of these subjects. Obviously, if the material is used appropriately, exposure to H2O2 from bleaching is minimal; furthermore, exposure is essentially limited to the oral cavity and is incapable of reaching a toxic systemic level because of the effective metabolic defensive mechanisms. It is important, however, to recognize the potential local adverse risks associated with tooth bleaching. In-office extracoronal bleaching and intracoronal bleaching both use materials of high H2O2 concentration. At-home bleaching requires continuous direct contact of the gel with the enamel surface for 30 minutes to 8 hours (overnight). The enamelgel contact may also be repeated within the same day or daily for an extended period. When applied by consumers at home, unintended direct contact of the bleaching gel with gingiva may occur; for some at-home systems, such as strips, gingival contact is inevitable. In addition, the tendency of home bleaching users to overuse the product may aggravate the tissue contact with the gel. In fact, tooth sensitivity and gingival irritation, though mostly transient and dissipating with time, are well-documented adverse effects associated with tooth bleaching. There have also been reports of enamel damage resulting from the use of OTC bleaching products.38, 39 Possible adverse effects of bleaching on the enamel, gingiva, pulp, and restorations are discussed later in the chapter.

Mechanisms of tooth bleaching using peroxide-based materials The mechanisms of tooth bleaching remain unclear at present. It is generally believed that free radicals produced by H2O2 may be responsible for the bleaching effects, and the mechanisms involved in the tooth bleaching are similar to those in textile and paper bleaching. It is hypothesized that H2O2 diffuses through the enamel

and dentin, in the process producing free radicals that react with pigment molecules, breaking their double bonds. The change in pigment molecule configuration and/or size may result in changes in the optical properties of the altered pigment molecules and, consequently, the perception of a lighter tooth color by human eyes. This assumption also helps explain the commonly observed shade rebounding shortly after the bleaching treatment, probably due to the re-formation of the double bonds. In addition to the bleaching effect, there may be nonbleaching mechanisms that help whiten the teeth during the bleaching process, including the cleansing of the tooth surface and changes in the enamel surface. Dehydration of enamel during the bleaching process may also result in a temporary whitening effect; it has been reported that enamel dehydration alone is capable of producing a significant, visible reduction in tooth shade.40 Such whitening effects dissipate with the rehydration of the enamel. The efficacy of bleaching can be influenced by a number of factors, including those relating to the patient (eg, age, sex, and initial tooth color), the bleaching material used (eg, type of peroxide compound, peroxide concentration, and other ingredients), and the application method (eg, contact time, application frequency, and enamel prophylaxis prior to bleaching treatment). These factors not only contribute to the bleaching efficacy but also affect the subsequent stability of the achieved bleaching.41, 42 Among these factors, the contact time of the bleaching material with the enamel surface appears to be more influential than the others.42

Intracoronal Bleaching Intracoronal bleaching, or nonvital tooth bleaching, is a conservative approach for correcting discoloration of endodontically treated teeth. While sodium perborate, which was initially used for intracoronal bleaching, remains the primary choice of peroxide material, H2O2 and carbamide peroxide have also been used for this treatment.43, 44 The treatment can be successful even for the tooth that received root canal treatment and was discolored many years previously. However, careful examination of the tooth and surrounding tissues is necessary for the success of intracoronal bleaching because the outcome depends on the identification of etiology, correct diagnosis, and proper selection of bleaching technique; the success of the bleaching also requires healthy periodontal tissues and properly obturated root canals to prevent the leakage of the bleaching agent into the periapical tissues.8, 44

Various techniques and procedures have been introduced for intracoronal bleaching; these methods may use the peroxide materials alone or with a

combination of heat or photonic means in an attempt to accelerate the bleaching reaction and enhance efficacy. The methods most commonly employed for intracoronal bleaching are the walking bleach and the thermocatalytic technique. Walking bleach is preferred because it requires less chair time and is safer and more comfortable for the patient.43–46

Walking bleach Walking bleach refers to the bleaching treatment occurring between the patient’s office visits; the term was first used by Nutting and Poe in 1963.47 The technique has been modified by eliminating the use of 30% aqueous solution of H2O2, making it a very popular and safe technique.8, 23, 48 It has been recommended that the walking bleach technique be attempted first in all cases requiring intra coronal bleaching, using the following typical procedure8: 1. Discuss the procedure with the patient so that he or she is familiar with the possible causes of discoloration, the procedure to be followed, the expected outcome, and the possibility of future rediscoloration. 2. Assess the status of the periapical tissues and the quality of the endodontic obturation radiographically. Teeth with signs of endodontic failure or questionable obturation should always be re-treated prior to bleaching. 3. Assess the quality and shade of any restoration present and replace the restoration if it is defective. Tooth discoloration is frequently the result of leaking or discolored restorations. In such cases, cleaning the pulp chamber and replacing the defective restoration will usually be sufficient. 4. Evaluate the tooth color with a shade guide and take clinical photographs at the beginning of and throughout the procedure. These provide a point of reference for future comparison (Figs 6-4a and 6-4b). 5. Isolate the tooth with rubber dam. The dam must fit tightly at the cervical margin of the tooth to prevent possible leakage of the bleaching agent on the gingival tissue. Interproximal wedges and ligatures may also be used to ensure adequate isolation. 6. Remove all restorative material from the access cavity, expose the dentin, and refine the access; verify that the pulp horns and other areas containing pulp tissue are clean (Fig 6-4c). 7. Remove all materials to a level just below the labialgingival margin. Orange solvent, chloroform, or xylene on a cotton pellet may be used to dissolve sealer remnants. There is no need to etch the dentin with phosphoric acid because it

may not improve the prognosis. 8. Apply a sufficiently thick layer, at least 2 mm, of a protective white cement barrier (eg, polycarboxylate cement, zinc phosphate cement, or glass-ionomer cement) to cover the endodontic obturation. The coronal height of the barrier should protect the dentinal tubules and conform to the external epithelial attachment (Fig 6-4d). 9. Prepare the walking bleach paste by mixing sodium perborate and an inert liquid, such as water, saline, or anesthetic solution, to a thick consistency of paste (Fig 6-4e). 10. With a plastic instrument, pack the pulp chamber with the paste; remove excess liquid by tamping with a cotton pellet. This also compresses and pushes the paste into all areas of the pulp chamber (Fig 6-4f). 11. Remove excess bleaching paste from undercuts in the pulp horn and gingival area and apply a thick, wellsealed provisional restoration (preferably an intermediate restorative material) directly against the paste and into the undercuts; carefully pack the intermediate restorative material to at least 3 mm thick to ensure a good seal (Fig 6-4g). 12. Remove the rubber dam and inform the patient that the bleaching agent works slowly and that significant lightening may not be evident for several days. 13. Evaluate the patient 2 weeks after the procedure. If necessary, repeat the procedure several times using the same steps. 14. As an alternative, if initial bleaching is not satisfactory, strengthen the walking bleach paste by mixing the sodium perborate with gradually increasing concentrations of H2O2 solutions, from 3% to 30%, instead of water. The more potent oxidizers may have an enhanced bleaching effect but are not recommended for routine use because the peroxide may permeate the tubules, allowing these more caustic agents to cause damage to the cervical periodontium. In such cases, a protective cream, such as Orabase (Colgate) or petroleum jelly, must be applied to the surrounding gingival tissues prior to placement of rubber dam. 15. In most cases, discoloration will improve after one or two treatments (Fig 6-4h). If no significant improvement is observed after three attempts, the tooth should be reassessed to confirm the etiology of discoloration and the suitability of the treatment plan.

Fig 6-4 (a) Preoperative view of teeth in occlusion. (b) Occlusal preoperative view showing an inappropriate access preparation and cemented prefabricated metal post. (c) Adjustment of the access preparation and removal of the existing restoration, gutta-percha, sealer, and dentin prior to bleaching. (d) Application of a protective layer of cement barrier to cover the endodontic obturation. (e) Sodium perborate powder mixed with water to a thick consistency of wet sand. (f) Packing of walking bleach paste in the pulp chamber. (g) Application of a provisional restoration and occlusal adjustment. (h) Bleaching results after two treatments. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

The same step-by-step procedures can be followed when hydrogen peroxide is used in the walking bleach technique (Fig 6-5).

Fig 6-5 (a) Preoperative view of teeth. (b) Adjustment of the access preparation and placement of a protective layer of cement barrier to cover the endodontic obturation. (c) Thick consistency of the hydrogen peroxide gel. (d) Whitening gel injected in the pulp chamber with a mini tip. Application of a provisional restoration and occlusal adjustment. (Courtesy of Dr Nadim Z. Baba, Loma (e) Whitening gel packed in place. (f) Linda, CA.)

Thermocatalytic method Thermocatalytic procedures are performed in the dental office; the technique involves the placement of the bleaching material (30% to 35% H2O2) in the pulp chamber and subsequent application of heat either by electric heating devices or specially designed lamps.8, 48 When such heating devices are used, it is imperative that overheating of the teeth and surrounding tissues be avoided. The surrounding soft tissues should be protected with petroleum jelly, Orabase, or cocoa butter during treatment to avoid heat damage. During treatment, the settings should be checked periodically, with adequate frequency; intermittent treatment with cooling breaks is preferred over a continuous session.

Ultraviolet photo-oxidation In the ultraviolet photo-oxidation technique, an ultraviolet light is applied to the labial surface of the tooth to be bleached while a cotton pellet of 30% to 35% H2O2 solution is placed in the pulp chamber. The duration of the exposure to the ultraviolet light is 2 minutes, which supposedly promotes oxygen release, a theoretic mechanism similar to that of the thermocatalytic bleaching technique.8, 49

Risks associated with intracoronal bleaching Intracoronal bleaching in general is an effective and safe procedure. However, the procedure has been associated with certain risks, including soft tissue burns, cervical root resorption, and adverse effects on resin-based materials.8, 44 A 30% concentration of H2O2 is highly caustic and causes chemical burns on contact with soft tissues. The heating devices used in the thermocatalytic technique may increase the risk of burns. However, this is a totally avoidable, iatrogenic risk. The soft tissues should always be adequately protected with petroleum jelly, Orabase, or cocoa butter whenever a material with a high H2O2 concentration is used. Cervical root resorption, an inflammatory-mediated external resorption of the root, has been reported following intracoronal bleaching in both clinical and histologic studies.50–56 The incidence in general appears low; in a review of four clinical studies, three studies with a total of 455 teeth in 137 patients who were followed for 3 to 15 years found no evidence of cervical root resorption, while the other study reported a 6.9% incidence of resorption (4 of 58 teeth in 48 patients who were followed for 1 to 8 years).44 The mechanism of cervical root resorption after intracoronal bleaching is not yet fully understood. It has been speculated that the bleaching agent diffuses through dentinal tubules, reaching periodontal tissues and causing necrosis of the cementum, inflammation of the periodontal ligament, and eventually cervical root resorption.55– 58 It has also been suggested that the peroxide-based bleaching material denatures the dentin when it diffuses through the dentinal tubules; the denatured dentin becomes a foreign body that is attacked by immunologic systems.58 Clinical observations indicate that previous traumatic injury, the patient’s age, and a high concentration of H2O2 in combination with heating appear to be risk factors that promote cervical root resorption.48, 49, 56–58 Therefore, the use of highly concentrated H2O2 with heat for intracoronal bleaching is questionable and should not be considered routinely. The residual oxygen produced during bleaching procedures has an inhibitory effect on the polymerization of resin-based materials such as bonding agents and composite resins. This potential adverse effect exists regardless of whether intracoronal or extracoronal bleaching is used. However, for intracoronal bleaching, it is necessary to seal the access to the pulp chamber immediately after the placement of the bleaching material. It is imperative to totally eliminate the residual oxygen prior to the placement of resin-based materials. It has been recommended that the access cavity be treated with catalase for 3 minutes to completely remove the residual oxygen; however, the effectiveness of this procedure is yet to be confirmed.8, 59

Extracoronal Bleaching Extracoronal bleaching may be used for vital or nonvital teeth as well as for a single tooth or whole arch. There has been a dramatic advancement in both the materials and application techniques since at-home extracoronal bleaching was first introduced in the literature in 1989.18–20 Extracoronal tooth bleaching has now become a popular procedure and an integrated part of dental practice.

In-office extracoronal bleaching As indicated by the term, in-office extracoronal bleaching is performed in the clinic by a dental professional. The procedure had been practiced for many years without much change in materials and methods. During the last two decades, however, the quest for whiter teeth from the public has promoted research efforts that have revolutionized in-office extracoronal bleaching technology. Various materials and clinical procedures are now available for in-office extracoronal bleaching, which is also called chairside bleaching or power bleaching. Current commercial in-office bleaching materials are almost exclusively available in the form of a gel, containing 25% to 40% H2O2. It is not advisable to use high concentrations of aqueous H2O2 solutions directly for tooth bleaching, as was practiced in early years. Besides a higher risk of tissue contact because of their lack of proper viscosity, the high concentrations of aqueous H2O2 solutions are thermodynamically unstable and may explode unless properly stored in a dark container and kept refrigerated. In early years, in-office bleaching often used highly concentrated H2O2 solution along with heat, electric current, and other chemicals such as ether in an attempt to enhance the bleaching efficacy. 20 While these approaches are no longer used in current practice, various lights have been used during the in-office bleaching process; the light may be specialized for such procedures, or it can be a regular curing light used for composite resins (Fig 6-6). A variety of light sources are available, including lasers (eg, argon or carbon dioxide), halogen lights, plasma arc lights, or light-emitting diodes. The wavelength may range from the high–ultraviolet light spectra to the low–visible blue light spectra to the invisible infrared spectra, such as the carbon dioxide laser. 40, 48, 60–62 Studies have found no significant advantages of using laser lights for bleaching; consequently, laser bleaching has become less popular than other light systems.48

Fig 6-6(a) Soft tissue protection and teeth isolation using blockout resin. (b) Light activation of bleaching gel material. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

The light exposure is intended to enhance the bleaching efficacy by activating the bleaching gel, through either a specific catalyst or the heat, to promote the decomposition process of H2O2. However, so far research on the efficacy of using light for in-office bleaching has been limited, and the results have been controversial; several studies reported an enhancing effect, while others detected no differences between teeth bleached with and without a light.40, 62, 63 In general, light exposure may have a short-term effect, depending on the in-office bleaching and light system. However, currently available data are insufficient regarding the long-term benefits of light-activated bleaching.

Chairside tooth bleaching without involvement of dental professionals More recently, tooth bleaching has become available at mall kiosks, salons, spas, and even cruise ships. These sites usually simulate in-office bleaching settings, often involving the use of a light, but are performed by individuals with no formal dental training and no license to practice dentistry. This phenomenon has come under scrutiny in several states and jurisdictions, resulting in actions to reserve the delivery of this service to dentists or appropriately supervised allied dental personnel.25 So far there has been no scientific research on this type of tooth bleaching.

At-home bleaching

A large variety of at-home tooth bleaching products are available, and all the current at-home bleaching products are gel formulations. In addition to those offered by dental professionals, various OTC bleaching products are available directly to consumers. As implied by the term, at-home tooth bleaching is intended to be applied by the users themselves at home, regardless of the source of the product. Most home bleaching offered by dentists, or professional at-home bleaching, involves the use of custom trays fabricated by dental professionals. The bleaching gel is loaded in the tray, and the patient wears the tray at home for several hours or overnight daily for 2 weeks or until a satisfactory tooth whitening effect has been achieved. There is also a professional at-home bleaching system offering prefabricated trays with preloaded bleaching gel. For professional at-home bleaching, the bleaching gels are available only from dentists. Both H2O2 and carbamide peroxide are used as active ingredients for professional at-home bleaching products, with most containing 3% to 7.5% H2O2 or 10% to 22% carbamide peroxide. Overall data accumulated so far support the efficacy and safety of at-home bleaching with 10% carbamide peroxide.19, 20 An H2O2-based professional bleaching strip is also available for at-home bleaching. Because the application technique may vary, it is advisable that the clinician instruct patients to follow the manufacturer’s instructions for using such a treatment modality. While the majority of the OTC at-home bleaching materials are also gels, their application methods vary, including trays, strips, or brushes. In addition to the bleaching gel, some products offer prebleaching rinses and afterbleaching rub-on powders. The range of the peroxide content in OTC bleaching products is comparable to that for the professional at-home bleaching materials; however, the quality of the OTC products may vary greatly. Their peroxide content may not be consistent and stable, and some products, including the prebleaching rinses, may come with an excessively low pH.

Risks associated with extracoronal bleaching Little dispute exists in regard to the efficacy of extracoronal tooth bleaching.64–66 However, there have been concerns about its safety, especially since the introduction of the athome bleaching materials.19, 20, 67–69 The safety concerns are mainly associated with potential toxicologic effects of free radicals produced by the peroxides used in the bleaching materials. The accumulated data over the last two decades have shown no significant long-term oral or systemic health risks associated with professional at-home tooth bleaching using materials of 10% carbamide peroxide. However, adverse effects may occur, depending on the quality of the

bleaching material, the techniques used, and the individual’s response to the bleaching treatment. The risks commonly associated with tooth bleaching are primarily local, including tooth sensitivity, gingival irritation, and potential adverse effects on enamel and restorative materials. Tooth sensitivity Tooth sensitivity to temperature changes is a commonly observed clinical side effect during or after the extracoronal bleaching of vital teeth, with an incidence of up to 50%.70 The sensitivity often occurs during the early stages of treatment, usually persists for 2 to 3 days, and is usually mild to moderate and transient.70–72 The development of tooth sensitivity does not appear to be related to the patient’s age or sex, defective restorations, enamel-cementum abrasion, or the dental arch treated; however, the risk increases in patients who change the bleaching gel more than once a day. 70 If the patient develops significant sensitivity, a shorter bleaching period is recommended. Topical fluoride applications and desensitizing toothpastes may also be used to alleviate the symptoms. While the mechanisms of tooth sensitivity are not fully understood, it has been proposed that the sensation is an indication of possible pulpal response.8, 26 The assumption is based on studies, most of which used in vitro models, showing that H2O2 in bleaching gel applied on the enamel surface is capable of penetrating enamel and dentin and reaching the pulp chamber. 73–77 Overall data show that less than 30 μg of H2O2 may reach dental pulp after gels of up to 12% H2O2 are applied to the enamel surface for up to 7 hours. The amount of H2O2 detected in the pulp chamber tends to increase with the time and H2O2 concentration in the gel, but not proportionally. It has been suggested that 50,000 μg of H2O2 is needed to inhibit pulpal enzymes, so the amount of H2O2 detected in the pulp chamber from the athome whiteners appears unlikely to cause significant damage to the pulp tissues. However, in vivo studies on this topic are lacking, and the long-term effects of exposure of the pulp to H2O2 are yet to be determined. Therefore, it is advisable to take adequate precautions, and extracoronal bleaching should not be performed on teeth with caries or exposed dentin or in close proximity to pulp horns. Defective restorations must be replaced prior to bleaching, and extra caution should be exercised for children and adolescents.78 Gingival irritation Gingival irritation is also a commonly observed clinical side effect of extracoronal bleaching; it may or may not occur with tooth sensitivity, and sometimes the patient

may not be able to differentiate gingival irritation from tooth sensitivity. 70, 79–82 The reported incidence of gingival irritation ranges from 5% to 50% in most studies. It is usually mild to moderate, occurring after 2 to 3 days’ use of the bleaching gel and then dissipating, and for most patients it is tolerable enough to complete the treatment. When tray systems are used, an ill-fitted tray is usually the primary reason for the irritation, and the problem usually resolves after proper trimming of the tray. For athome bleaching, the risk of gingival irritation appears to be related to the H2O2 concentration in the gel and the contact of the gel with the gingiva. Gingival irritation associated with in-office bleaching is mostly caused by leaky or failed gingival barrier protection. Care must be taken to check the barrier for signs of leakage, usually indicated by air bubbles, and the patient should be questioned about any discomfort during the bleaching treatment. When tissue burn is detected, the surface should be extensively rinsed with water until the whiteness is reduced. In more severe cases, a topical anesthetic, limited movements, and good oral hygiene aid healing. Application of protective cream such as petroleum jelly or cocoa butter can prevent most of these complications. Potential adverse effects on enamel The effect of extracoronal bleaching on enamel has been examined primarily in three aspects: (1) mineral loss, (2) surface morphologic changes, and (3) alteration of surface microhardness; most of these studies have been conducted using in vitro systems.83–91 In general, there is a loss of minerals during bleaching treatment; however, this loss does not appear to constitute a significant risk because of the effective remineralization mechanisms readily available in the oral cavity. Most scanning electron microscopy and surface microhardness studies showed little or no changes in the bleached enamel surface.20, 83, 86–91 On the other hand, several investigators reported alteration of enamel surfaces associated with bleaching treatments, including shallow depression, increased porosity, and slight erosion. 20, 84, 85 In most cases, however, the observed alterations of enamel surface morphology varied among different products and were associated with products using acidic prerinses or gels of low pH. In addition, studies have demonstrated that some soft drinks and fruit juices (eg, orange, lemon, and apple) cause demineralization and alteration of enamel surface morphology comparable to or greater than those reported for bleaching treatment. A 6-month clinical study reported that long-term use of a bleaching gel containing 10% carbamide peroxide did not adversely affect the surface morphology of human enamel.83

To date, there is no clinical evidence of adverse effects of the dentist-monitored at-home whiteners on enamel. However, two clinical cases of significant damage to enamel associated with the use of OTC tooth whitening products have been reported.38, 39 Potential adverse effects on restorations A relevant safety concern is the mercury release from amalgam restorations during and after bleaching.92–94 While not much debate exists regarding whether bleaching causes mercury release, the reported amount of mercury release associated with bleaching varies greatly. The potential health implications of the mercury released remain controversial and are yet to be determined. Because of the known toxicity of mercury, as a general rule it is not advisable to perform bleaching for patients whose teeth are restored extensively with amalgam. While the adverse effects of tooth bleaching on resinbased materials are not considered to be direct health risks, the consequences can be significant to the quality and longevity of such restorations. Numerous studies have reported that tooth bleaching may adversely affect the physical and/or chemical properties of restorative materials; effects include increased surface roughness, crack development, marginal breakdown, release of metallic ions, and decreases in toothto-restoration bond strength.95–98 The potential adverse effects of bleaching on bond strength have been well recognized. A plausible mechanism is the inhibition of adequate polymerization of the bond ing agent by residual oxygen formed during the bleach ing. Similar effects are also applicable to other resin-based restorative materials that require in situ polymerization. The postbleaching inhibitory effects on polymerization dissipate with time, and an interval of 2 weeks is found to be adequate to avoid such adverse effects.20

Role of dental professionals in extracoronal bleaching treatment The direct major outcome of tooth bleaching is the lightening of tooth shade or color, and it may thus be perceived as a simple cosmetic or esthetic procedure. However, this can be a misconception because a tooth of darker color or discoloration, particularly with stains of an intrinsic nature, may not simply be an esthetic problem, and bleaching may not be the appropriate or the best choice for treatment.3, 20, 26 An initial evaluation and examination of the tooth discoloration are necessary for proper

diagnosis and treatment. Bleaching can affect restorative materials and may result in color mismatch of teeth with existing restorations or crowns. These are just examples of the aspects of tooth bleaching that cannot be performed or determined by consumers themselves or nondental individuals. For athome bleaching using trays, professionally fabricated, custom-fit trays help reduce the amount of gel needed for maximal efficacy while minimizing the gel contact with gingiva. In addition, periodic evaluation of bleaching progress by the dentist allows early detection of any possible side effects and reduces the patient’s risk of using inferior bleaching materials and inappropriate application procedures as well as any temptation to overuse or abuse the product. A recent case report illustrates the importance of the role of dental professionals in tooth bleaching treatment.99 The authors performed comprehensive clinical examinations of the dentition and gingiva, custom designed an athome bleaching regimen, provided detailed instructions, and monitored the bleaching progress and made adjustments accordingly; this careful planning and conduct of the bleaching helped maximize efficacy while minimizing potential risks, which was the key to ensuring the success of this difficult case. Therefore, it is highly recommended that tooth bleaching involve dental professionals. The American Dental Association encourages all patients interested in tooth bleaching to seek advice from a dental professional.25, 100

Summary In-office procedures for intracoronal and extracoronal bleaching have been a part of dental practice for many years. With the data accumulated over the last two decades, at-home bleaching has also become an accepted and integrated procedure in dentistry. Clinical research has demonstrated no significant long-term oral or systemic health risks associated with professional at-home tooth bleaching using 10% carbamide peroxide gels, which is equivalent to 3.5% H2O2. Therefore, when used appropriately, tooth bleaching is safe and effective. Like any dental procedure, bleaching involves risks. Tooth sensitivity and gingival irritation can occur in a significant portion of patients, although in most cases the effects are mild to moderate and transient. When gels with high H2O2 concentrations, such as those used for in-office bleaching, are used without adequate gingival protection, severe mucosal damage can occur. Although rare, potential adverse effects are possible with inappropriate application or abuse or with the use of inappropriate at-home bleaching products. H2O2 is capable of producing various toxicologic effects, so potential risks must be recognized. So far few data are

available on the safety of OTC at-home bleaching that simulates the intended application mode of such products. The safety of bleaching performed at mall kiosks, salons, and spas and on cruise ships is of particular concern because the procedures are similar to those of in-office bleaching but performed by individuals with no dental training. Effective and safe tooth bleaching requires correct diagnosis of the problems associated with tooth discoloration or stains. Furthermore, side effects such as tooth sensitivity and gingival irritation may occur during the course of bleaching treatment. The involvement of dental professionals in bleaching treatment is necessary to minimize the risks and maximize the benefits.

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81. Gerlach RW, Zhou X. Comparative clinical efficacy of two professional bleaching systems. Compend Contin Educ Dent 2002; 23:35–41. 82. Gerlach RW, Sagel PA, Jeffers ME, Zhou X. Effect of peroxide concentration and brushing on whitening clinical response. Compend Contin Educ Dent 2002;23:16–21. 83. Haywood VB, Leonard RH, Dickinson GL. Efficacy of six-months nightguard vital bleaching of tetracycline-stained teeth. J Esthet Dent 1997;9:13–19. 84. Bitter NC. A scanning electron microscope study of the long-term effect of bleaching agents on the enamel surface in vivo. Gen Dent 1998;46:84–88. 85. Potocnik I, Kosec L, Gaspersic D. Effect of 10% carbamide peroxide bleaching gel on enamel microhardness, microstructure, and mineral content. J Endod 2000;26:203–206. 86. White DJ, Kozak KM, Zoladz JR, Duschner H, Götz H. Peroxide interactions with hard tissues: Effects on surface hardness and surface/subsurface ultrastructural properties. Compend Contin Educ Dent 2002;23:42–48. 87. Lopes GC, Bonissoni L, Baratieri LN, Vieira LC, Monteiro S Jr. Effect of bleaching agents on the hardness and morphology of enamel. J Esthet Restor Dent 2002;14:24–30. 88. Attin T, Schmidlin PR, Wegehaupt F, Wiegand A. Influence of study design on the impact of bleaching agents on dental enamel microhardness: A review. Dent Mater 2009;25:143–157. 89. Berger SB, Cavalli V, Martin AA, et al. Effects of combined use of light irradiation and 35% hydrogen peroxide for dental bleaching on human enamel mineral content. Photomed Laser Surg 2010;28:533–538. 90. Li Q, Xu BT, Li R, Yu H, Wang YN. Quantitative evaluation of color regression and mineral content change of bleached teeth. J Dent 2010;38:253– 260. 91. Sun L, Liang S, Wang YSZ, Jiang T, Wang Y. Surface alteration of human tooth enamel subjected to acidic and neutral 30% hydrogen peroxide. J Dent 2011;39:686–692. 92. Rotstein I, Dogan H, Avron Y, Shemesh H, Steinberg D. Mercury release from dental amalgam following treatment with 10% carbamide peroxide in vitro. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:216–219. 93. Rotstein I, Avron Y, Shemesh H Dogan H, Mor C, Steinberg D. Factors affecting mercury release from dental amalgam exposed to carbamide peroxide bleaching agent. Am J Dent 2004;17: 347–350. 94. Al-Salehi SK. Effects of bleaching on mercury ion release from dental amalgam. J Dent Res 2009;88:239–243. 95. Attin T, Hannig C, Wiegand A, Attin R. Effect of bleaching on restorative

materials and restorations—A systematic review. Dent Mater 2004;20:852– 861. 96. Swift EJ, Perdigao J. Effects of bleaching on teeth and restorations. Compend Contin Educ Dent 1998;19:815–820. 97. Breschi L, Cadenaro M, Antoniolli F, Visintini E, Toledano M, Di Lenarda R. Extent of polymerization of dental bonding systems on bleached enamel. Am J Dent 2007;20:275–280. 98. Lima AF, Fonseca FM, Cavalcanti AN, Aguiar FH, Marchi GM. Effect of the diffusion of bleaching agents through enamel on dentin bonding at different depths. Am J Dent 2010;23:113–115. 99. Li Y. Commentary. Successful bleaching of teeth with dentinogenesis imperfecta discoloration: A case report. J Esthet Restor Dent 2011;23:11. 100. American Dental Association. For the dental patient: Tooth whitening—What you should know. J Am Dent Assoc 2009; 40:384.

Crown Lengthening Dentists are often faced with treating endodontically treated teeth affected with extensive caries or fractures in the subgingival area (Fig 7-1). The choice between extraction and restoration of the existing tooth is often influenced by the patient’s finances, the clinical circumstances, and the experience of the treating dentist. Although new treatment alternatives such as dental implants are readily available, dentists should not disregard the option of preserving the natural dentition. Furthermore, if the patient wishes to retain part or all of the dentition, the dentist should consider honoring those desires, provided that the outcomes of these treatment options are predictable.

Fig 7-1 (a and b) Endodontically treated maxillary anterior teeth in two patients exhibit caries and inadequate ferrules. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Surgical crown lengthening is a routinely performed dental treatment.1–5 Crown

lengthening involves the surgical removal of hard and soft periodontal tissues to gain supracrestal tooth length, allowing longer clinical crowns and reestablishment of the biologic width.2, 6 The indications for crown lengthening surgery include esthetic enhancement, creation of a clinical crown in the presence of excessive occlusal wear, exposure of subgingival caries, exposure of a fracture, or some combination of these. Crown lengthening surgery has been categorized as esthetic or functional.7 The term functional relates to exposure of subgingival caries, exposure of a fracture, or exposure of cervical tooth structure in endodontically treated teeth to establish a crown ferrule. Crown lengthening is probably one of the most common reasons for referral of patients to a periodontist. Crown lengthening is one of the most complicated oral surgical procedures, not only from a technical viewpoint but also because of the complexity of factors that may influence the success of the procedure and overall treatment outcomes.

Esthetic Concerns Surgical crown lengthening in the anterior areas gives rise to discussion about esthetics. Passive eruption in the anterior sextants often results in short clinical crowns and esthetically unpleasant excessive gingival display. This, often accompanied by a medium or high smile line, contributes to unfavorable esthetics for the patient. If the patient desires an anterior dentition that is more normal in tooth length, resective treatment that exposes the anatomical crowns may be warranted8, 9 (Fig 7-2). In such cases, surgical crown lengthening is the most obvious choice of procedure. Sometimes functional and esthetic therapy can come together in the esthetic zone when subgingival caries does not extend greatly or at all to the root. In these cases, the surgeon may need a surgical stent as a guide to determine the position of the new crown margins.10

Fig 7-2 Altered passive eruption in a young female patient has resulted in short teeth and an esthetically unpleasant excessive gingival display. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Frequently, the interdental gingival tissues have to be altered during crown lengthening procedures, resulting in widened embrasure areas and an esthetically unpleasing display. In such cases, tremendous communication between the surgeon and the restorative dentist must be established to reduce or eliminate esthetic concerns involving adequate prosthetic crown contours. The dentist can help to alleviate this problem by lengthening and widening the crown contact areas to accommodate the new morphology of the interproximal papilla.2 Sometimes crown lengthening procedures are indicated in esthetically important teeth free of caries and/or fractures. In such cases, even if complete-coverage restorations are not planned, crown lengthening can be predictably performed as long as the interdental tissues are not involved in the process of resection11 (Fig 73). Special attention needs to be paid to the position of the bone and free gingival margin in relation to the cementoenamel junction. Resective therapy may result in pronounced recession if the free gingival margin already approximates the cementoenamel junction of the tooth in question. Black triangles may develop if the postoperative dimension between the contact area and the interdental osseous crest is greater than 5 mm.12 The esthetic concerns should be extensively discussed with the patient before this surgical procedure is undertaken.

Fig 7-3 (a) The preoperative smile shows excessive gingival display. (b) Postoperative view reveals enhanced esthetics after orthodontic treatment and a crown lengthening procedure. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Biologic Width When crown lengthening is planned to increase the length of available tooth, the biologic width has to be considered; it must not be encroached on, as this may lead

to periodontal breakdown.13 The issue of the dimensions of the biologic width has been debated heavily among dentists for a long time. Gargiulo et al14 reported the average length of the dentogingival junction to be 2.04 mm. They identified the subcomponents of the dentogingival junction as the connective tissue attachment (mean value, 1.07 mm) and the epithelial attachment (mean value, 0.97 mm). Others reported mean values of 0.77 mm for the connective tissue attachment and 1.14 mm for the epithelial attachment.15 Ingber et al2 suggested that the term biologic width be used to describe the average value of the dentogingival junction, approximately 2 mm. They suggested that an additional 1 mm be added coronal to the 2-mm dentogingival junction as an optimal distance between the bone crest and the restorative margin. The authors reasoned that “adding the 1 mm to the average 2 mm of the biologic width establishes a minimum dimension of 3 mm coronal to the alveolar crest that is necessary to permit healing and proper restoration of the tooth.”2 Nevins and Skurow16 also described the significance of establishing a 3-mm biologic distance between the osseous crest and plaque-associated crown margins. Other recommendations range between 3.50 and 5.25 mm.17, 18 Dibart et al6 retrospectively evaluated the outcome of crown lengthening surgery prior to final crown placement on mandibular molars. The results indicated that 40% of the molars with initial margin-to-bone distance of less than 4 mm developed a furcation lesion at 5 years after crown placement. Although the mesial and distal alveolar crests were not evaluated, none of the molars that had more than 4 mm of margin-tobone distance developed a furcation lesion. Moreover, placement of a restoration in close proximity to the osseous crest has been demonstrated in a human clinical study to induce chronic inflammation.19 Despite conflicting opinions, it is generally accepted that a minimum of a 3-mm distance between the osseous crest and the margin of the dental restoration significantly reduces the risk of periodontal attachment loss induced by subgingival restorative margins.7 Where the root length and anatomy permit, it may be safer to allow at least 4 mm of distance between the osseous crest and the restoration margin.

Ferrule Effect Because the ultimate goal of treatment is an effective, longterm dental restoration, the concept of ferrule must be considered during treatment planning for crown lengthening procedures. Different lengths and forms of the ferrule have been

studied.20–23 The length and form are essential factors for the success of the “ferrule effect.” Ferrule effectiveness is enhanced by grasping larger amounts of tooth structure. When possible, maintenance of 1.5 to 2.0 mm of intact tooth structure around the entire circumference of a core creates an optimally effective crown ferrule. The amount of tooth structure engaged by the overlying crown appears to be more important than the length of the post in increasing a tooth’s resistance to fracture. In cases of extensive tooth structure loss, the dentist often creates a foundation restoration prior to preparing the tooth for complete-coverage restoration. Moreover, in some cases, endodontic treatment and core buildup may be necessary because of the extensive tooth breakdown and pulp proximity. The foundation restoration helps the restorative dentist to increase the surface area of the preparation, thereby increasing the retention and resistance form of the future restoration. However, the challenge of the positioning of the margin remains. The greatest amount of retention and resistance to dislodgment of the restoration occurs at the apical one-third of the preparation.7 If the supragingival crown preparation results in a margin that is partially or entirely seated on foundation restorative material, the forces of occlusion may be transmitted to the foundation restoration and in the case of a post and core, between the internal aspect of the root and the post.7 Because this area is usually filled with cement, the fatigue of the cement under occlusal stress could result in dislodgment of the post and core or, worse, fracture of the tooth.7 In such clinical scenarios, “creation” of additional tooth structure helps build up the ferrule, providing better clinical outcomes for the restorative dentist. The solid tooth structure that becomes engaged by the restoration may provide dispersion of the occlusal forces into the periodontium rather than on the post-core–tooth interface. However, the need for ferrule has been disputed by some authors, 24, 25 who argue that closer attention should be paid to the length of the post, as well as the type of cement used, rather than solely to the existence of a ferrule. Nevertheless, the majority of those who have written on the subject agree on the need for a ferrule. The data from survival studies support the concept that ferrules that grasp larger amounts of tooth structure (1.5 to 2.0 mm) are more effective than those engaging only a small amount of tooth structure.21–23, 26, 27 In the majority of these cases, surgical crown lengthening is used to create the necessary ferrule length, as well as to prevent violation of the biologic width.

Other Considerations

Multiple factors weigh heavily on the outcomes of the surgical crown lengthening procedure, and they all need to be to be taken into account when a patient is being assessed for surgery. These factors include but are not limited to the crown-root ratio, the occlusion, the position of the lip, the length and shape of the roots, the position of the furcations, the width and anatomy of the surrounding bone, the adjacent teeth, the muscle insertions, the soft tissue anatomy, the amount of attached gingiva, the patient’s gingival biotype, the patient’s expectations, the skills and expectations of the dentist, and any treatment alternatives.13 The surgeon must determine the postsurgical level of bone to ensure that a favorable crown-root ratio will still exist after treatment. Failure to do so may result in an unfavorable clinical situation, increased tooth mobility, and poor prognosis. Occlusion has to be taken into account because excessive occlusal forces may put additional stress on the reduced periodontium, leading to increased mobility and ultimately a poor prognosis. Furthermore, the tooth anatomy must be evaluated because if the tooth narrows significantly apically, there is a potential risk of both pulp exposure during preparation as well as overcontouring of the restoration due to insufficient space. Close adjacent roots will cause technical difficulty during the surgical treatment because they may make it virtually impossible to remove the interdental bone without damaging the roots.13 Incomplete removal of the bone will inevitably diminish clinical success because of the limited apical repositioning of the gingival tissues and limited crown exposure. Other treatment alternatives, such as orthodontic extrusion, may be considered when the periodontal condition of the affected tooth does not allow for surgical removal of bone. The furcations must be analyzed from several aspects to avoid furcation exposure. One is the potential to encroach on the furcation and create a furcation defect and a potential periodontal problem in the future. The other aspect is the divergence of the roots coming from the trunk because it may mislead the surgeon into damaging the roots during the process of bone removal. As mentioned, the position of the smile line will have an effect on the esthetic outcome. Therefore, the examination of the patient’s lip position is important because it will determine the amount of tooth and gingiva that should be on display to achieve an acceptable outcome.28 A high muscle insertion may affect the apical repositioning of the flap. A shallow vestibule or a pronounced external oblique ridge also may limit the location of the flap.13 Finally, the amount of attached gingiva present must be evaluated because it has been shown that, to maintain periodontal health, there should be at least 2 to 3 mm of attached gingiva.29 If the amount of attached gingiva is limited, the surgical technique

should be modified to accommodate this factor and to prevent creation of a mucogingival defect.

Surgical Technique The surgical lengthening of the clinical crown should always be performed only following success in the initial periodontal phase of treatment and always in the context of a comprehensive restorative treatment plan.30 The patient should have an acceptable level of oral hygiene and no active periodontal disease, including but not limited to the absence of deep periodontal pockets and bleeding on probing. The following situations may be considered indications for surgical crown lengthening: deep subgingivally located preparation margins (to facilitate impressions) (Fig 7-4); deep subgingivally located caries lesions; root fractures or resorptions in the cervical third of the root; perforations of parapulpal posts in the cervical third of the root; insufficient retention for crowns; existing deep subgingivally located margins (to restore the violated biologic width), leading to inflammatory responses that cannot be controlled otherwise; in combination with root sectioning, amputations, and separations; extremely abraded dentitions prior to reconstruction; and anterior teeth with short clinical crowns and high smile lines (to improve the esthetic appearance).30

Fig 7-4 (a) The remaining supragingival tooth structure on a mandibular left first molar is inadequate for restorative procedures. (b) A subgingival initial incision is made. (c) Osseous resective therapy is performed.

Adequate tooth structure around the tooth is exposed to allow proper preparation without impinging on the dimension needed for the postoperative formation of a healthy attachment apparatus. (d) The 4-week postoperative result is shown.

Depending on the extent of the tissue removal that is needed, surgical crown lengthening can be divided into two main categories: (1) soft tissue crown lengthening procedures and (2) soft tissue and bone tissue crown lengthening. Soft tissue crown lengthening is a fancy term to simply describe a gingivectomy that is usually done only where the clinical crown is shorter than the anatomical crown and the bone is at an appropriate level. In patients with thin tissue biotypes, the gingivectomy will expose more of the crown and improve esthetics. An external or internal bevel incision is used, depending on the amount of attached gingiva, presence or absence of pigmentations, and esthetic concerns.13 This procedure can be done with a scalpel, an electrosurge, or a laser. In all other cases, where the biologic width and ferrule concepts apply, some removal of bone is necessary in addition to soft tissue removal (Fig 7-5).The surgical procedure in such cases always involves raising of a flap and bone removal. If the amount of attached gingiva is sufficient, an inverse bevel incision in a scalloped fashion usually made at a distance of 2 to 3 mm from the gingival margin.13 Special attention is paid on the palatal side due to the thickness of mucosa in this area. A second intrasulcular incision is placed in the sulcus. Most surgeons extend the incision to the gingival sulcus of the surrounding teeth by the length of one to two teeth to blend better and to achieve a more effective surgical field. A third incision is then placed interproximally to release the interdental papilla.12 A full-thickness flap is raised, and the bone is recontoured.

Fig 7-5 (a) A tooth fracture causing a violation of the biologic width leaves insufficient tooth structure for an adequate restoration. (b) A fullthickness flap is raised. (c) Bone is recontoured using rotary and hand instruments. (d) After 6 to 8 weeks of healing, a final impression is taken, and a definitive crown is fabricated and cemented.

Sometimes, in cases of inadequate attached gingiva, vertical releasing incisions should be made, and the flap should be repositioned apically to preserve the keratinized tissues and avoid creation of a mucogingival defect. Also, vertical releasing incisions may be needed in cases of limited visibility. The flaps are then sutured, and dressing may be placed if needed. As with any surgical procedure, there may be some complications. Complications associated with crown lengthening include esthetic concerns, root sensitivity, root resorption, and tooth mobility.13

Restorative Procedures

After a crown lengthening procedure, patients and restorative dentists alike want to know how long they must wait before placement of the definitive restoration. Factors that the surgeon must consider before answering this important question are the type of surgical procedure, the extent of bone removal, and, above all, the esthetics. Gingival margins do not stabilize completely until at least 5 months after surgery.31 In esthetic areas, provisional restorations should be used until the healing period is finished. They should be highly polished to prevent plaque accumulation and avoid unnecessary tissue inflammation, a main cause of gingival recession.32, 33 In areas of no esthetic concern, it is this author’s opinion that restorative treatment can be commenced after at least a 6- to 8-week healing period without aberrant healing issues.

Lasers and Crown Lengthening The use of lasers in dentistry, especially in periodontal surgical procedures, has been a controversial topic in the dental scientific literature. To date, there is no solid scientific evidence regarding the use of lasers for surgical crown lengthening procedures. Although there is potential for the use of lasers in soft tissue crown lengthening, it seems that cutting soft tissue with lasers is no faster than conventional cutting with a blade or an electrosurgical instrument.34 According to Christensen, 34 lasers are no easier to use than conventional instruments, the issue of whether they are a better tool is highly controversial, and they certainly are not less expensive. He also reported that use of lasers for hard tissue cutting is still in its infancy, but some dentists are optimistic about this use, and some dentists report success.34 Some references to laser-mediated flapless crown lengthening have been made in the published literature.35, 36 Most of these references are noncontrolled case reports or technique-focused articles, and prospective, randomized con trolled studies are absent.37 These flapless crown lengthening procedures are essentially gingivectomies or variances of gingivectomy procedures in which parts of the gingiva are removed by the use of the laser. Except for the low-energy lasers, the practical concern about the use of most common dental lasers is possible severe thermal damage of the surrounding tissues.38, 39 Although still controversial, the low-level laser therapy can possibly offer therapeutic benefits to patients, such as accelerated wound healing and pain relief.40 Some positive effects on postsurgical healing of dental lasers were reported in the literature. In an in vitro study, soft tissue incisions produced by the erbiumchromium–doped yttrium scandium gallium garnet (Er,Cr:YSGG) laser showed

equal histologic repair to those produced by the scalpel.41 In the same study, bone defects produced by the laser showed more new bone formation than did one produced by a bur. There are no solid research data in the literature to support the application of lasers for surgical crown lengthening. It is this author’s opinion that although dental lasers may potentially be utilized for manipulation of soft tissues and stimulation of wound healing, they cannot be effectively used for a typical crown lengthening surgery, where bone removal and osteoplasty are necessary. In most clinical cases, standard surgical instruments must be utilized to perform a quick, clean procedure with predictable clinical outcomes.

Summary Surgical crown lengthening has an important role in restorative dentistry. The clinician must thoroughly understand the concepts of biologic width, ferrule, esthetics, and other contributing factors in order to achieve a satisfactory clinical outcome from a crown lengthening procedure. For patients who require crown lengthening, the general dentist should consider the following recommendations: • • • •

Perform clinically acceptable root canal treatment before the referral. Remove all caries lesions Prepare the tooth with a margin that is as close to the final margin as possible. Complete the foundation restoration and post and core before the referral. Preferably, use a material for buildup that contrasts with the tooth structure, to help the surgeon. • Place a clinically acceptable provisional restoration. Its contours should be ideal, with no open margins. The provisional restoration must be produced of highly polished acrylic resin, and it should be easy to remove. The occlusion obtained on the provisional restoration must be good, without premature contact or traumatic occlusion. • Do not take impressions before 6 to 8 weeks after the surgical procedure in nonesthetic areas. • Do not take impressions before 8 to 12 weeks after the surgical procedure in esthetic areas.

References

1. Deas DE, Moritz AJ, McDonnell HT, Powell CA, Mealey B. Osseous surgery for crown lengthening: A 6-month clinical study. J Periodontol 2004;75:1288– 1294. 2. Ingber FJS, Rose LF, Coslet JG. The “biologic width”: A concept in periodontics and restorative dentistry. Alpha Omegan 1977; 70:62–65. 3. Oakley E, Rhyu I, Karatzas S, Gandini-Santiago L, Nevins M, Caton J. Formations of the biologic width following crown lengthening in nonhuman primates. Int J Periodontics Restorative Dent 1999;19:529–541. 4. Pontoriero R, Carnevale G. Surgical crown lengthening: A 12-month clinical wound healing study. J Periodontol 2001;72:841–848. 5. Smukler H, Chaibi M. Periodontal and dental considerations in clinical crown extension: A rational basis for treatment. Int J Periodontics Restorative Dent 1997;17:465–477. 6. Dibart S, Capri D, Kachouh I, Van Dyke T, Nun ME. Crown lengthening in mandibular molars: A 5-year retrospective radiographic analysis. J Periodontol 2003;74:815–821. 7. Hempton TJ, Dominici JT. Contemporary crown-lengthening therapy: A review. J Am Dent Assoc 2010;141:647–655. 8. Allen EP. Surgical crown lengthening for function and esthetics. Dent Clin North Am 1993;37:163–179. 9. McGuire MK. Periodontal plastic surgery. Dent Clin North Am 1998;42:411– 465. 10. Scutella F, Landi L, Stellino G, Morgano SM. Surgical template for crown lengthening: A clinical report. J Prosthet Dent 1999; 82:253–256. 11. Hempton TJ, Esrason F. Crown lengthening to facilitate restorative treatment in the presence of incomplete passive eruption. J Calif Dent Assoc 2000;28:290– 298. 12. Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla. J Periodontol 1992; 63:995–996. 13. Cunliffe J, Grey N. Crown lengthening surgery—Indications and techniques. Dent Update 2008;35:29–35. 14. Gargiulo A, Wentz F, Orban B. Dimensions and relations of the dentogingival junction in humans. J Periodontol 1961;32:261–267. 15. Vacek JS, Gher ME, Assad DA, Richardson AC, Giambarresi LI. The dimensions of the human dentogingival junction. Int J Periodontics Restorative Dent 1994;14:154–165. 16. Nevins M, Skurow HM. The intracrevicular restorative margin, the biologic width, and the maintenance of the gingival margin. Int J Periodontics

Restorative Dent 1984;4:30–49. 17. Rosenberg ES, Garber DA, Evian C. Tooth lengthening procedures. Compend Contin Educ Dent 1980;1:161–172. 18. Wagenberg BD, Eskow RN, Langer B. Exposing adequate tooth structure for restorative dentistry. Int J Periodontics Restorative Dent 1989;9:322–333. 19. Günay H, Seeger A, Tschernitschek H, Geurtsen W. Placement of the preparation line and periodontal health: A prospective 2-year clinical study. Int J Periodontics Restorative Dent 2000;20:171–181. 20. Libman WJ, Nicholls JI. Load fatigue of teeth restored with cast posts and cores and complete crowns. Int J Prosthodont 1995;8: 155–161. 21. Pereira JR, de Ornelas F, Conti PC, do Valle AL. Effect of a crown ferrule on the fracture resistance of endodontically treated teeth restored with prefabricated posts. J Prosthet Dent 2006;95:50–54. 22. Ng CCH, Dumbrigue HB, Al-Bayat MI, Griggs JA, Wakefield CW. Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth. J Prosthet Dent 2006;95:290–296. 23. Zhi-Yue L, Yu-Xing Z. Effects of post-core design and ferrule on fracture resistance of endodontically treated maxillary central incisors. J Prosthet Dent 2003;89:368–373. 24. Al-Hazaimah H, Gutteridge DL. An in vitro study into the effect of the ferrule preparation on the fracture resistance of crowned teeth incorporating prefabricated post and composite core restoration. Int Endod J 2001;34:40–46. 25. Meng Q-F, Chen Y-M, Guang H-B, Yip KH-K, Smales RJ. Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core Systems. Oper Dent 2007;32:595–601. 26. Isidor F, Brondum K, Ravnholt G. The influence of post length and crown ferrule on the resistance to cyclic loading of bovine teeth with prefabricated titanium. Int J Prosthodont 1999;12:78–82. 27. Morgano SM, Brackett SE. Foundation restorations in fixed prosthodontics: Current knowledge and future needs. J Prosthet Dent 1999;82:643–657. 28. Tjan AHL, Miller GD, The JG. Some esthetic factors in a smile. J Prosthet Dent 1984;51:24–28. 29. Maynard JG Jr, Wilson RDK. Physiological dimensions of the periodontium significant to the restorative dentist. J Periodontol 1979;50:170–177. 30. Lang NP. Periodontal considerations in prosthetic dentistry. Periodontol 2000 1995;9:118–131. 31. Wise MD. Stability of the gingival crest after surgery and before anterior crown placement. J Prosthet Dent 1985;53:20–23.

32. McEntee MI, Bartlett SO, Loadholt CB. A histologic evaluation of tissue response to three currently used temporary acrylic resin crowns. J Prosthet Dent 1978;39:42–46. 33. Waerhaug J. Temporary restorations: Advantages and disadvantages. Dent Clin North Am 1980;24:305–316. 34. Christensen GJ. Is the current generation of technology facilitating better dentistry? J Am Dent Assoc 2011;142:959–963. 35. Adams TC, Pang PK. Lasers in aesthetic dentistry. Dent Clin North Am 2004;48:833–860. 36. Lee EA. Laser-assisted gingival tissue procedures in esthetic dentistry. Pract Proced Aesthet Dent 2006;18(9):suppl 2–6. 37. McGuire MK, Scheyer ET. Laser-assisted flapless crown lengthening: A case series. Int J Periodontics Restorative Dent 2011;31: 357–364. 38. Kreisler M, Al Haj H, Daublander M, Gotz H, Duschner H, Willershausen B, d’Hoedt B. Effect of diode laser irradiation on root surfaces in vitro. J Clin Laser Med Surg 2002;20:63–69. 39. Kreisler M, Al-Haj H, d’Hoedt B. Intrapulpal temperature changes during root surface irradiation with an 809-nm GaAlAs laser. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002:93: 730–735. 40. Sun G, Tunér J. Low-level laser therapy in dentistry. Dent Clin North Am 2004;48:1061–1066. 41. Perussi LR, Pavone C, de Oliveira GJ, Cerri PS, Marcantonio RA. Effects of the Er,Cr:YSGG laser on bone and soft tissue in a rat model. Lasers Med Sci 2012;27:95–102.

Preprosthetic Orthodontic Tooth Eruption Orthodontic forced eruption is a common procedure used in preparation for tooth restoration, often referred to in the context of “adjunctive orthodontics.” It is a method designed to improve both the osseous and gingival anatomy of a crown or an implant-receiving site when a tooth and/or its periodontal housing are compromised by pathologic or traumatic conditions. While the discussion in this chapter is focused on isolated teeth that require extrusion because of loss of tooth structure (eg, crown and in various extents coronal root substance), the principle applies to groups of teeth during orthodontic treatment in both the maxillary and mandibular arches, still with the purpose of ameliorating the biologic environment for later restorative rehabilitation. Also, forced eruption is considered before both crown restoration and tooth replacement by implant. Certain multidisciplinary treatments include forced eruption as a separate adjunctive orthodontic procedure, but in many instances it is combined with complementary periodontal procedures such as crown lengthening or bone and soft tissue grafting, depending on the end result: tooth restoration or implant placement.

Progression of the Forced Eruption Concept The recorded development of orthodontic tooth eruption1 started with the concept of “artificial elongation.”2 Ingber3–5 further promoted the idea, possibly in combination with periodontal surgery, to level isolated one- and two-wall infrabony osseous defects through generation of bone from orthodontic tension, enabling the restoration

of a clinical crown that otherwise would not be built up optimally. Thus, orthodontic movement could cosmetically alter the location of the free gingival margin. The advances in the concept materialized with another series of findings: Only alveolar bone attached to the root by the periodontal ligament (PDL) moves with the tooth, and controlled supracrestal fiberotomy has the potential to affect the morphology of the alveolar crest.1, 6–8 The ultimate progression of the concept concerned the utilization of eruption to augment bone in future implant sites; this approach could be achieved in a predictable way based on a classification of extraction sockets according to their morphology.9

Causes and Implications of Loss of Tooth Structure Partial or total loss of clinical crowns results primarily from subgingival tooth fracture at or beyond the level of the osseous crest, whether it develops gradually from extensive caries or arises suddenly from trauma, pathologic conditions (eg, internal root resorption), or iatrogenic causes (eg, endodontic perforation).10, 11 Crown fracture is the most common effect of trauma.12 Other indications for orthodontic forced eruption are treatment of isolated periodontal vertical defects and management of lateral perforation of the tooth during endodontic treatment.13 Also reported as potential reasons for the procedure are root resorption, abrasion, occlusal wear, and harmful habits.11 Trauma is the most likely of these indications to cause loss of structure and consequently necessitate forced eruption. The types of tooth fracture are described in the prevalent plane of space: horizontal (transverse), vertical (least common), and oblique. Horizontal breaks affect mostly the permanent maxillary incisors. The experience of orthodontists with conditions such as greater-than-normal overjet enhances their exposure to maxillary incisor trauma and favors their potential contribution to the treatment of these situations. A systematic review revealed that an increased (more than 3-mm) overjet is associated with nearly double the risk of trauma.14 The cutoff for determining severe overjet remains arbitrary, although it is practically accepted at a value of 6 mm or more, which occurs in nearly 7% of American children aged 6 to 11 years.15, 16 The success of the orthodontic extrusion is related to the level of fracture beyond the cementoenamel junction. The smaller this level (1 to 2 mm), the more favorable the residual crown-root ratio after extrusion. This ratio remains acceptable at 1:1, when root and crown heights are nearly equal. No evidence is available on predictable successful management or outcome as the fracture reaches midroot

level.17, 18 When extrusion for crown restoration is not feasible or indicated, “orthodontic extraction” is recommended; this excessive extrusion brings bone occlusally to achieve healthier bone thickness and associated gingival tissue for implant placement. This approach may still be achievable in deeper root fractures but is hard to achieve if the fracture level is beyond 3 mm from the alveolar crest or beyond the coronal third of the root (mostly monoradicular). Critical to the success of extrusion is the state of health of the root, which in most instances has had endodontic treatment. In this context, the age of the tooth warrants special consideration if the patient is young and the apex is not closed.

Goals of Orthodontic Eruption Coronal restoration Forced eruption of individual teeth suggests a simple process; yet three important goals and concepts underline the procedure: (1) bone leveling, (2) obtaining an optimal position of usable tooth substance to facilitate technical work, and (3) restoring an optimal crown-root ratio after the carious disease, prior dental work, or trauma near the alveolar bone has undermined the original proportions. This restitution obviously aims at recapturing the biologic relationships of the tooth within its periodontium and promoting function that protects the reconstructed anatomy. Anatomical considerations Often the need is for minor to moderate eruption to move sound dental tissue to a level compatible with the tooth’s biologic width (normally 2.04 mm) that the prosthetic restoration must respect (Fig 8-1). The biologic width is located between the cementoenamel junction and the alveolar bone crest and includes nearly equal amounts (about 1 mm) of epithelial (junctional epithelium) and connective tissue attachments.19 Because of the variability in restoring a crown to the coronal level of the junctional epithelium, the sulcular depth (nearly 1 mm) is sometimes included in the definition of biologic width.

Fig 8-1 Components of the biologic width (~ 2.04 mm): EA—epithelial attachment (~ 1.00 mm); CTA— connective tissue attachment (~ 1.00 mm). S—sulcus (~ 0.75 mm).

This width is actually a biologic necessity that may not be violated; its restoration should be considered when periodontal surgery (such as gingivectomy) will impinge on the periodontal attachment. In this instance, bone loss may occur as the crestal bone resorbs apically to accommodate the new biologic width at approximately its original dimension (nearly 2 mm). These anatomical considerations exclude the following situations from orthodontic tooth eruption: posterior teeth where the furcation would be exposed on tooth extrusion, and teeth with moderate to severe bone loss from periodontal disease where the procedure would also compromise the optimal crown-root ratio. Prosthetic and orthodontic criteria

The anatomical considerations are translated in practical considerations for treatment, namely, the usability and restorability of the tooth and the esthetic outcome. The first level of clinical judgment concerns the long-term viability of the restored tooth and cost-effectiveness of saving it, given the multidisciplinary involvement of an orthodontist, a restorative dentist, and likely a periodontist. The clinicians must determine whether the primary goal is functional and/or esthetic and if that goal would be met by the contemplated alternative. In this vein, the endodontic and periodontal prognoses occupy a primacy in deciding on the value and choice of orthodontic therapy. Specifically for esthetic outcome, the pertinent evaluation cuts across all concerned dental specialties and focuses essentially on the relationship among the teeth, particularly maxillary anterior teeth, and between teeth and lips at rest and in function, including smile and speech. These relationships include various components: tooth morphology (shape, size, texture, and color); inclination, alignment, and gradation of teeth; symmetry; bone architecture; gingival constitution and architecture; and relationship of the lip line to the gingiva and teeth. However, a prevailing component relates to the transition between restoration (whether restored crown or implant) and gingival tissues. In general, this relationship is better maintained in patients with a high lip line during smile (or “gummy smile”). Crowns and pontics that do not match the adjacent and contralateral counterparts or that have unnatural relationships with the gingiva and periodontium are likely to taint the esthetic balance. While a 1:1 crown-root ratio is acceptable, the necessity to restore biologic width and the need for coronal tooth structure for added resistance of the tooth/restoration complex (ferrule effect) require the presence of 4 mm of tooth substance coronal to the crestal bone. The amount of extrusion is calculated accordingly on an individual basis depending on the location of sound tooth structure and may approximate at least 4 mm in most instances (actual statistics are not available in the literature). Besides the presence of fracture, the caries level, and the root length, another factor that may influence the outcome of or even the decision for forced eruption is the form of the root. Thin and tapered roots in general present poor emergence (because the new cementoenamel junction is thinner and more coronal when the tooth is erupted), leading to asymmetry with the contralateral tooth and esthetic compromise.20

Replacement by implant

An alternative goal is the “extraction” of teeth through orthodontic extrusion for the purpose of implant site enhancement; the aim is to bring the bone to the crestal level prior to the placement of implants.1 This type of extrusion may involve different mechanical considerations related to anchorage preparation. Of major impact on prosthetic restoration is the fact that the presence of a healthy attachment apparatus even in a minimal zone occupied by the PDL fibers can facilitate socket fill through orthodontic extrusion and concomitantly gingival augmentation.1 Circumstances requiring implant replacement obviously are different from those allowing crown restoration. A tooth is to be extracted because the pathologic or traumatic defect has proceeded beyond the possibility of restoring a crown to the generally acceptable crown-root ratio of 1:1 (although in individual situations, teeth restored to less than a 1:1 ratio have been maintained). A summary of conditions and treatment possibilities is shown in Fig 8-2.

Fig 8-2 Hypothetical spectrum of root defects, treatment options, and predictability of outcome, including orthodontic extrusion.

Mechanics of Forced Eruption Basic principles Effect of forces Every tooth movement follows basic mechanical principles, simplified by considering the effect of force application on the tooth. A force is defined by its amount and direction, and its effect is a factor of these elements. A light continuous force has been determined to be optimal in orthodontics, causing remodeling of the alveolar bone; in contrast, a heavy and intermittent force, which is often labeled as a n orthopedic force, has a greater modeling effect on the skeletal supporting structures.21, 22 Force direction is defined in reference to the center of resistance of the tooth, which is located approximately in the middle of a single-rooted tooth and at the furcation area of multirooted teeth. To achieve bodily movement, in which the tooth moves in a direction parallel to its axis, the force should be applied at a level through the center of resistance of the tooth. However, such movement is not practical because forces are directed through brackets and wires placed on the crown away from this center. Thus, a moment that causes rotation of the tooth is generated; the moment is equal to the force multiplied by the distance between its point of application and the center of resistance (Fig 8-3).

Fig 8-3 (a) A force applied through the center of resistance of a tooth (arrow) engenders bodily movement. The center of rotation is estimated at infinity. (b) Tipping (curved arrow) is the simplest form of orthodontic tooth movement and is produced when a single force (straight arrow) is applied against the crown of the tooth away from its center of resistance. A moment (M) is created equal to the force amount (F) multiplied by the distance (d) between the point of application on the tooth and the center of resistance (M = F× d).

This principle applies in all planes of space. In forced eruption, and to avoid rotation of the tooth during extrusion, the direction of the force through the center of resistance would require a pulling force from the occlusal edge of the tooth. Such traction is possible when the crown is broken, and the force is applied on a post placed through the central axis of the tooth (Fig 8-4). If the extrusive force is applied on a provisional crown, it causes a lingual rotation of the tooth that must be counteracted by a compensatory labializing force in the anchorage setting.

Fig 8-4 The principles shown in Fig 8-3 apply in all planes of space, including extrusion. (a) For the tooth to move bodily, the force is applied through the tooth axis (arrow), a principle applicable when the crown is broken, and the anchoring post is cemented to a post in the devitalized root. (b) Force exerted on the labial surface of the tooth (straight arrows) creates a moment that will tip the tooth palatally (curved arrow). The distance between the force axis and the center of resistance is small compared to a distal force, as represented in Fig 8-3; accordingly, with a light to moderate force, the moment is lower and the tipping more controllable. The palatal rotation of the tooth may be counteracted by a compensatory labial force in the anchorage setting.

Anchorage

Anchorage involves the apparatus of teeth and wires involved in stabilizing the teeth, supporting tooth movement that would normally react to the active extruding force by shifting away from their original position. The number of anchoring teeth depends on the size and position of the tooth being moved as well as the distance it is being moved. The side effect of tooth extrusion is intrusion and rotation of the adjacent teeth. The addition of secondary archwires, inserted in brackets or bonded, buttresses these teeth and nearly eliminates the unwanted movements. Anchorage is set up differently for anterior and posterior teeth. In general, the incorporation of two adjacent teeth on either side of the affected tooth is the optimal approach, particularly for the more posterior multirooted teeth compared with the anterior single-rooted teeth. A heavy (rectangular) anchoring archwire that consolidates the supporting teeth minimizes side-effect tipping.

Application The type of attachment and force application depend on various factors, including the force direction, anchorage requirements, and esthetic needs. Once anchorage preparation ensures stabilization of the anchoring teeth, the mode of application of the extruding force is determined according to the appliance system used. The appliance usually consists of brackets and wires bent to extrude a tooth that has enough substance for bracket positioning. In this instance, different possibilities exist (Table 8-1):

• The tooth has most of its substance, and extrusion is intended to level the bone with that of the adjacent teeth. As the tooth is erupted, its occlusal edge is trimmed to allow further extrusion without occlusal interference by the overerupted tooth. This scheme may be applied to anterior and posterior teeth. • The tooth has enough substance labially for a bracket attachment without the existence of or need for a provisional crown. Often a provisional crown is needed for esthetic reasons, particularly in the anterior region (mostly incisors). • No coronal structure is available. If a provisional crown is not placed, the force may be applied directly to a post (often of round 0.036-inch wire but also possibly rectangular stainless steel wire) centered in the devitalized root. The anchoring unit may be bonded to allow force application through an elastomeric thread. Variable designs are illustrated in Figs 8-5 and 8-6. Such assemblies are more applicable to posterior teeth, if only for esthetic considerations.

Fig 8-5 Forced eruption of a maxillary right lateral incisor. (a and b) The fractured crown is shown before treatment. (c) The pretreatment periapical radiograph shows the metallic hook cemented in the pulp chamber. (d)

Anchorage is provided through a round archwire stepped down to provide greater distance to the tooth to allow force activation. A helix bent in the step-down section helps to stabilize the elastomeric tie supplying the force. (e and f) As the tooth extrudes and comes closer to the archwire, additional force is provided through a hole made at a higher level of the tooth (near the cementoenamel junction). This approach allows further eruption without having to replace the canal-retained hook at a more apical level. The rectangular archwire ensures more rigid anchorage. (g) A provisional crown has been placed and bracketed for final tooth movement and proper root angulation. (h) Another temporary crown has been placed immediately after debonding. (i) The posttreatment periapical radiograph shows the shortened root of the lateral incisor, a proper crown-root ratio, and the parallel roots of the incisors. (Courtesy of Dr Felipe Rezk-Lega, American University of Beirut Medical Center.)

Fig 8-6 Various anchorage settings and modes of orthodontic eruption have been described. (a) The simplest form of support is provided by heavy, round stainless steel wire bonded occlusally between the maxillary canine and the second premolar to extrude the first premolar and between the mandibular first molar and the first premolar to move the second premolar. (b) The occlusal view of the assembly in the maxillary arch shows that the level of force through the tooth canal lines up with the anchoring wire, providing for translatory vertical movement of the first premolar. (c) The head of the hook is bent parallel to the axis of the anchoring wire. The hook is made with a rectangular wire but may also be made with round wire. (Courtesy of Dr Nadim Abou Jaoude, American University of Beirut Medical Center.)

Table 8-2 presents general practical guidelines for mechanical application of orthodontic extrusion.

Biology of Forced Eruption Basic concepts The normal process of tooth eruption during development depends on metabolic events within the PDL, the mostly collagenous supporting structure of the tooth. The response to orthodontic force is a function of force magnitude; heavy forces normally lead to necrosis of cellular elements within the PDL and rapidly developing pain, while lighter forces are more compatible with the survival of cells and less pain. The optimal force for orthodontic tooth movement should be high enough to stimulate cellular activity without total occlusion of the PDL blood vessels. Optimal forces for orthodontic extrusion are estimated at 35 to 60 g, depending on the size of the tooth; incisors require smaller values than multirooted posterior teeth.22 The classic theory of orthodontic tooth movement is based on the generation of areas of compression and tension within the PDL. Sustained pressure causes the tooth to shift within the PDL space, compressing the ligament in areas and stretching it in others. These areas are defined by the type of movement, that is, whether the tooth moves bodily, tips, or rotates. Extrusion is singled out as a special consideration in orthodontic tooth movement because ideally, under controlled movement with no tipping, the movement would produce only areas of tension and no areas of compression within the PDL. However, it is expected that in practice at least a small amount of tipping occurs. Even in pure tension, heavy forces are usually undesirable, although claimed to be efficient when the intention is not to bring the alveolar bone along with the tooth.

Theories and state of evidence Compatible with the premise that heavy extrusive forces would cause rapid displacement of a tooth out of its socket— not to be confused with the concept of slower orthodontic extraction to move the alveolar bone occlusally prior to implant placement—an increased rate of extrusion, with or without supracrestal fiberotomy, was advanced as a factor that would help forego the need for a periodontal root lengthening procedure. The latter is a periodontal minor surgery that would be indicated when the bone is extruded with the tooth, requiring its removal for two reasons: bone leveling with the adjacent teeth and exposure of sufficient tooth substance for crown restoration. However, definitive evidence is not yet on hand, prompting the consideration of the advocated approaches: • Increased force magnitude. Heavy or “unphysiologically high”23 force and rapid movement would extrude the tooth without its remodeling alveolar bone. While higherlevel evidence is not available, findings on “tooth distraction” demonstrate the possibility of fast displacement, but the level of discomfort (or pain) and the applicability to extrusion need investigation. Practice demonstrates that even heavy extrusive forces may be accompanied by corresponding movement of bone and gingiva. • Fiberotomy in combination with forced eruption. Repeated intrasulcular incision during tooth extrusion through the junctional epithelium and the supracrestal connective tissue attachment has been reported to prevent coronal displacement of the attachment apparatus, bone, and gingiva, achieving “clinical crown lengthening” and overcoming the need for osseous surgery.23, 24 Originally, fiberotomy was described as a “selective surgical technique intended to reduce relapse of rotated teeth significantly but not to damage the periodontium.”7 It consists of inserting a surgical blade to the depth of the gingival sulcus and severing all fibrous attachments around the tooth to a depth of nearly 3 mm apical to the alveolar crest, after which a periodontal probe would show increased probing (nearly 6 mm) of “sulcular extension” (Fig 8-7). The procedure is performed under local infiltration of anesthetics without the excision of attached or marginal gingiva. Probing depth should revert to normal after healing.

Fig 8-7 Fiberotomy. The surgical blade (blue) is inserted to the depth of the gingival sulcus, through the biologic width (BW), and severs all fibrous attachments around the tooth, almost beyond the supracrestal fibers (SF), to a depth of nearly 2 to 3 mm apical to the alveolar crest (dashed line). (Adapted from Edwards7 with permission.)

Further guidelines need exploration, particularly for individual requirements that must be considered. In most situations the treatment plan may be to avoid bone extrusion with the root, but in others at least partial bone extrusion may be needed.

Scope of Forced Eruption: From Crown Restoration to Tissue Engineering The ability to reduce or generate bone volume through orthodontic treatment validates the qualification of such treatment as orthopedic. Moreover, the potential for tooth movement to improve periodontal health, enhance bone formation within

existing bony defects, and reduce probing depth has long been established, even in the basic setting of uprighting tipped molars.25 Further, experimental studies have confirmed that the entire periodontal attachment apparatus, including the osseous structure, PDL, and soft tissue components, move together with the tooth.26 These findings reflect a basic form of tissue engineering. The concept of forced tooth eruption has developed in its goal and process from the narrow definition of extrusion, to restore a crown under conditions of favorable crown-root ratio and appropriate biologic width, to include an extended physiologic process of tissue engineering, providing a healthier bony housing and associated gingival coverage for implants. A major adjunct procedure to periodontalprosthetic reconstruction, this concept falls within what is commonly known as orthodontic implant site preservation or development, when implant placement after tooth extraction would not be indicated because of inadequate bone volume. Other contraindications to conventional immediate implant placement include the presence of periapical infection, residual growth in a growing patient, and expected compromised implant primary stability.

Periodontal and orthodontic considerations Indication for the procedure is essentially periodontal restoration to allow optimal prosthetic reconstruction: • To avoid ridge caving that would result from the extraction of a tooth. 27, 28 Loss in area 5 years after the extraction of anterior teeth or decrease in alveolar ridge 6 years after ablation of mandibular primary molars equals nearly one-third of the original dimension.29–32 • To reverse bone loss associated with periodontal disease, thus improving the amount and quality of bone available for implant placement and altering the soft tissue architecture of the periodontium (Fig 8-8).

Fig 8-8 (a) Maxillary incisors extruded for the purpose of orthodontic extraction. Significant extrusion is demonstrated by the position of the brackets above the cementoenamel junction on dentin. New nonkeratinized

gingiva is visible (Atherton red patch on the left central incisor33). (b) The radiograph reveals bone formation and socket fill beyond the alveolar crest. (c) Newly formed alveolar bone is present 4 months after extraction (at stage-one implant surgery). The osseous architecture has been reversed compared with the compromised anatomy that was present before extrusion. This series illustrates the potential of the method for engineering new bone. (Reprinted from Celenza1 with permission.)

In this context, orthodontic eruption becomes a component of enhancing facial esthetics, more specifically smile esthetics in the anterior oral region. Presumably, by allowing the placement of an implant head nearly 3 mm apical to the level of the cementoenamel junction of the adjacent natural tooth, the increased gingival depth generated by the procedure facilitates the positioning of an appropriate emergence profile.34 Known as orthodontic extraction to denote the actual removal of the tooth,11, 35 the method has also been termed orthodontic extrusive remodeling, 9 more appropriately referring to tissue generation. Not only alveolar osseous movement but also gingival margin movement is concomitant with tooth movement. The width of the attached gingiva is reported to increase, while the mucogingival junction remains stable.9, 36, 37 In addition, as a tooth is extruded, a smaller diameter of the root and alveolus moves occlusally. Thus, a greater bone volume should result at the end of stabilization, possibly yielding enhanced initial implant stability and osseointegration over a large surface area.9 Other periodontal advantages have been cited. In the presence of periodontal pockets, extruded teeth displace coronally ahead of the gingival margin, allowing the reduction of probing depth and the creation of an immature (Atherton) “red patch” coronal to the original gingival margin33, 36 (see Fig 8-8). More specifically, gingival augmentation is reported to result from outward eversion of the nonkeratinized sulcular epithelium that later keratinizes (apparently within 28 days) following exposure to the oral cavity. 33, 36 The new gingival tissue aids primary flap closure on implant placement. Orthodontic extrusion may also yield more successful implant placement and even better outcome predictability when combined with bone grafting and guided tissue regeneration in buccal sites with deficient bone.1, 9, 36, 37 As with all preprosthetic orthodontic preparations, care must be taken to position the tooth appropriately mesiodistally and labiolingually for optimal implant placement relative to the adjacent natural teeth and for better emergence profile, tissue depth from alveolar crest to implant seating surface, and definitive restoration in the esthetic zone.38 Unlike tooth extrusion to improve crown-root ratio, which may be achieved in as little as 2 months, orthodontic extraction takes longer, over the course of several

months, and is followed by 4 to 10 weeks of stabilization. Different protocols have been published,9, 36, 37 but comparative research is still needed. One such approach to developing hard and soft tissue volumes (including interproximal papillae) lost to periodontal disease in the maxillary incisor area involved tipping the tooth in the direction of the alveolar defect and slowly displacing the attachment apparatus.39 This method reflects an attempt at optimizing the local anatomical structure, as the mere extrusion of a tooth does not guarantee proper periodontal restoration, particularly of the gingival architecture. A most challenging task is maintaining or re-forming the interproximal papillae between teeth, between implants and teeth, and between adjacent implants. The basic question in relation to periodontal-prosthetic restoration is how much gingival tissue can be maintained over the interproximal bone predictably. 40 Assuming a normal gingival embrasure size, the average amount of papillary gingival height over the interproximal bone is 4.0 to 4.5 mm, when adjacent teeth are present.41 Aware of the variability in the distance from contact point to bony crest between implants because restorative dentists may establish the contact point of the crowns at any distance from the gingival margin (Fig 8-9), Tarnow et al 42 measured the height of the soft tissue to the osseous crest between adjacent implants, irrespective of the location of the contact point. They determined that “only 2, 3, or 4 mm of soft tissue height (average 3.4 mm) can be expected to form over the interimplant crest of bone.” This average reflects a deficiency of nearly 1 to 2 mm of tissue available to duplicate the interproximal papillae between natural teeth, possibly resulting in an esthetic compromise or failure.

Fig 8-9 The biologic width is located subcrestally in relation to the implant (a), while it forms supracrestally around a natural tooth (b). The interdental tissue on an implant does not receive the same level of support as the

interdental tissue on a tooth. (Reprinted from Tarnow et al42 with permission.)

When acute periodontal disease is involved, tooth extrusion should proceed after the condition has been stabilized. After tooth consolidation and subsequent extraction, immediate replacement by implant has been recommended, concomitant with the placement of healing abutments to prevent gingival collapse around the implant.35 The abutments may be replaced with cover screws 3 months later. When a root is fractured at a level where orthodontic extrusion is not practicable yet surgical ablation may lead to unrecoverable bone loss, the root may be left submerged under certain conditions, if an infection does not exist.43 Surrounding tissues may be preserved without crestal bone resorption and thus reduction of the height of the interdental papillae and width of the edentulous ridge. However, the restoration would be a pontic rather than an implant. In growing patients, implant placement must be deferred because continuous eruption of adjacent teeth leaves the implant in infraocclusion44 (Fig 8-10). In these instances, the ideal situation is the restoration of the tooth and delay of the extraction as long as possible when the tooth is asympto matic. If not, bone volume may be lost before implant placement. Various orthodontic options have been advanced to avoid such loss, including moving adjacent teeth into the extraction site.45

Fig 8-10 (a) The implant anchoring the crown of the maxillary lateral incisor was placed when the patient was approximately 15½ years old. The occlusal level of the incisor (red line) lined up with that of the adjacent teeth. Three years later, concomitant with an increase in body height of 18 cm, the incisor was in an infraclusion of 1.6 mm. (b) By age 25 years 2 months, the vertical discrepancy was measured at 2.3 mm. Note the difference in both the gingival (yellow lines) and occlusal (red line) levels of the lateral incisor crown relative to the adjacent teeth. (Adapted from Thilander et al44 with permission.)

Research considerations

The hypothesis advanced regarding the disparity of attachment between implants and teeth has been that the biologic width around an implant is subcrestal, apical to the implant abutment connection, because the implant stands below the interimplant bone crest. In contrast, the biologic width of a healthy tooth always forms supracrestally. Thus, the interdental tissue lacks the crestal support (including connective tissue attachment and epithelial attachment) that exists between an implant and a tooth or two adjacent teeth (see Fig 8-9). This discussion underscores the fact that orthodontic extrusion should bring adequate bone height and thickness to the occlusal level. In areas with periodontal bone loss, orthodontic extrusion helps create the underlying bone support for the papilla that is necessary for more predictable results.43 Research is needed to explore these parameters to establish proper guidelines for adequate amount and shape of recaptured bone volume and gingival thickness through forced extrusion. In a systematic review of implant site development by orthodontic extrusion of nonrestorable teeth, most of the selected articles (n = 18) were case reports or case series describing orthodontic extrusion of periodontally hopeless maxillary anterior teeth.46 Clinically significant gains in alveolar bone and gingival tissue were reported in all cases, with quantitative and qualitative improvements in the implant sites. However, the authors could not draw conclusions on efficacy of the method relative to any other methods because comparisons were not available.

Summary Teeth with significant caries lesions or fractures lack sound root structure that could support an adequate restoration. Periodontal defects alter the crown-root ratio and disturb proper alignment of the alveolar bone of adjacent teeth. Orthodontic forced eruption is a conservative alternative to crown lengthening through periodontal surgery that removes supporting alveolar bone, potentially challenging smile and facial esthetics. Adjunctive orthodontic eruption of teeth in preparation for prosthodontic restoration offers various advantages: • Forced eruption results in more physiologic and esthetic relationships with the adjacent teeth compared with crown lengthening, bone grafting, and guided tissue regeneration, particularly when soft tissue is not sufficient for the use of grafts or membranes. • Orthodontic extrusion provides more predictable results by improving the periodontal parameters: bone, soft tissue, and crown-root ratio.

• Forced eruption enhances the attachment apparatus for an optimal relationship between the crown restoration or implant and the gingiva. This protocol is particularly advantageous in maxillary esthetic areas. • The introduction of osseointegrated implants has allowed maximization of the method of orthodontic extrusion to further develop bone and associated soft tissues that enhance implant success. Orthodontic movement can improve an implant site for more biologically compatible restorative results.9 Cited advantages include the improvement of primary implant anchorage, preservation of the interdental bone heights, and an increase in the amount of attached gingiva. Forced eruption is essentially a process of periodontal as well as prosthodontic restoration. In this context, the procedure ultimately represents a prime example of multidisciplinary treatment, bringing together the concepts and expertise within prosthodontics, orthodontics, and periodontics. Preprosthetic adjunctive tooth movement must be an integral part of prosthetic treatment, not only for tooth alignment but also because it represents a periodontal enhancement through tooth extrusion, improvement of the crown-root ratio, distribution of space within the arch and between roots for adequate implant space, and correction of mucogingival and osseous defects.

References 1. Celenza F. The development of forced eruption as a modality for implant site enhancement. Alpha Omegan 1997;90:40–43. 2. Oppenheim A. Artificial elongation of the teeth. Am J Orthod Oral Surg 1940;26:931–940. 3. Ingber JS. Forced eruption. 1. A method of treating isolated one and two wall infrabony osseous defects. J Periodontol 1974;45: 199–206. 4. Ingber JS. Forced eruption. 2. A method of treating unrestorable teeth. J Periodontol 1976;47:203–216. 5. Ingber JS. Forced eruption: Alteration of soft tissue cosmetic deformities. Int J Periodontics Restorative Dent 1989;9:416–425. 6. Polson A, Caton J, Polson AP, et al. Periodontal response after tooth movement in intrabony defects. J Periodontol 1984;55:197–202. 7. Edwards JG. A surgical procedure to eliminate rotational relapse. Am J Orthod 1970;57:35–46. 8. Pontoriero R, Celenza F, Ricci G, Carnevale G. Rapid extrusion with fiber resection: A combined orthodontic-periodontic treatment modality. Int J

Periodontics Restorative Dent 1987;7(5):30–43. 9. Salama H, Salama M. The role of orthodontic extrusive remodeling in the enhancement of soft and hard tissue profiles prior to implant placement: A systematic approach to the management of extraction site defects. Int J Periodontics Restorative Dent 1993; 13:312–333. 10. Garrett GB. Forced eruption in the treatment of transverse root fractures. J Am Dent Assoc 1985;111:270–272. 11. Uddin M, Mosheshvili N, Segelnick SL. A new appliance for forced eruption. N Y State Dent J 2006;72:46–50. 12. Flores MT, Andreasen JO, Bakland LK. Guidelines for the evaluation and management of traumatic dental injuries. Dent Traumatol 2001;17:193–196. 13. Rosenberg ES, Cho SC, Garber DA. Crown lengthening revisited. Compend Contin Educ Dent 1999;20:527–542. 14. Nguyen QV, Bezemer PD, Habets L, Prahl-Andersen B. A systematic review of the relationship between overjet size and traumatic dental injuries. Eur J Orthod 1999;21:503–515. 15. Kelly JE, Sanchex M, Van Kirk LE. An assessment of the occlusion of the teeth of children 6–11 years. USDHEW publication No. (HRA) 74-1612. Vital and Health Statistics; series 11, No. 130. Washington, DC: National Center for Health Statistics, Public Health Service, 1973. 16. Ghafari J. The role of developmental and occlusal conditions in timing orthodontic treatment. Alpha Omegan 1999;92:28–35. 17. Camp JH. Management of sports-related root fractures. Dent Clin North Am 2000;44:95–109. 18. Zachrisson BU, Jacobsen I. Long-term prognosis of 66 permanent anterior teeth with root fractures. Scand J Dent Res 1975;83:345–354. 19. Ingber JS, Rose LF, Coslet JG. The ‘biologic width’—A concept in periodontics and restorative dentistry. Alpha Omegan 1977;70: 62–65. 20. Kokich, VG. Adjunctive role of orthodontic therapy. In: Newman MG, Takei HH, Klokkevold PR, Carranza FA (eds). Clinical Periodontology, ed 10. St Louis: Saunders Elsevier, 2006:856–870. 21. Burstone CJ. Applications of bioengineering to clinical orthodontics. In: Graber TM, Vanarsdall RL (eds). Orthodontics: Current Principles and Techniques, ed 4. St Louis: Mosby, 2005:293–330. 22. Proffit WR, Fields HW, Sarver D. Biomechanics, mechanics, and contemporary orthodontic appliances. In: Contemporary Orthodontics, ed 4. St Louis: Mosby Elsevier, 2007. 23. Wehr C, Roth A, Gustav M, Diedrich P. Forced eruption for preservation of a deeply fractured molar. J Orofac Orthop 2004; 65:343–354.

24. Kozlovsky A, Tal H, Lieberman M. Forced eruption combined with gingival fiberotomy. A technique for clinical crown lengthening. J Clin Periodontol 1988;15:534–538. 25. Brown IS. The effect of orthodontic therapy on certain types of periodontal defects. 1. Clinical findings. J Periodontol 1973;44: 742–756. 26. Berglundh T, Marinello CP, Lindhe J, Thilander B, Liljenberg B. Periodontal tissue reactions to orthodontic extrusion: An experimental study in the dog. J Clin Periodontol 1991;18:330–336. 27. Abrams H, Kopczyk RA, Kaplan AL. Incidence of anterior ridge deformities in partially edentulous patients. J Prosthet Dent 1987; 57:191–194. 28. Hawkins CH, Sterrett JD, Murphy HJ, Thomas JC. Ridge contour related to esthetics and function. J Prosthet Dent 1991;66:165–168. 29. Carlsson G, Bergman B, Hedegård B. Changes in contour of the maxillary alveolar process under immediate dentures. A longitudinal clinical and x-ray cephalometric study covering 5 years. Acta Odontol Scand 1967;25:45–75. 30. Ostler MS, Kokich VG. Alveolar ridge changes in patients congenitally missing mandibular second premolars. J Prosthet Dent 1994;71:144–149. 31. Schropp L, Wenzel A, Kostopoulos L, Karring T. Bone healing and soft-tissue contour changes following single-tooth extraction: A clinical and radiographic 12-month prospective study. Int J Periodontics Restorative Dent 2003;23:313– 323. 32. Araujo MG, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol 2005;32:212–218. 33. Atherton JD. The gingival response to orthodontic tooth movement. Am J Orthod 1970;58:179–186. 34. Palmer RM, Palmer PJ, Newton JT. Dealing with esthetic demands in the anterior maxilla. Periodontol 2000 2003;33:105–118. 35. Mantzikos T, Shamus I. Case report: Forced eruption and implant site development. Angle Orthod 1998;68:179–186. 36. Mantzikos T, Shamus I. Forced eruption and implant site development: Soft tissue response. Am J Orthod Dentofacial Orthop 1997;112:596–606. 37. Nozawa T, Sugiyama T, Yamaguchi S, et al. Buccal and coronal bone augmentation using forced eruption and buccal root torque: A case report. Int J Periodontics Restorative Dent 2003;23:585–591. 38. Garber DA. The esthetic dental implant: Letting restoration be the guide. J Am Dent Assoc 1995;126:319–325. 39. Uribe F, Taylor T, Shafer D, Nanda R. A novel approach for implant site development through root tipping. Am J Orthod Dentofacial Orthop 2010;138:649–655.

40. Spear FM, Kokich VG, Matthews DP. The esthetic management of a severe isolated periodontal defect in the maxillary anterior. Compend Contin Educ Dent 2008;29:281–287. 41. Tarnow DP, Magner AW, Fletcher P. The effect of the distance from the contact point to the crest of bone on the presence or absence of the interproximal dental papilla, J Periodontol 1992; 63:995–996. 42. Tarnow D, Elian N, Fletcher P, et al. Vertical distance from the crest of bone to the height of the interproximal papilla between adjacent implants. J Periodontol 2003;74:1785–1788. 43. Salama M, Ishikawa T, Salama H, Funato A, Garber D. Advantages of the root submergence technique for pontic site development in esthetic implant therapy. Int J Periodontics Restorative Dent 2007;27:521–527. 44. Thilander B, Odman J, Lekholm U. Orthodontic aspects of the use of oral implants in adolescents: A 10-year follow-up study. Eur J Orthod 2001;23:715–731. 45. Kokich V. Maxillary lateral incisor implants: The orthodontic perspective. Adv Esthet Interdisc Dent 2006;2(2):2–7. 46. Korayem M, Flores-Mir C, Nassar U, Olfert K. Implant site development by orthodontic extrusion. A systematic review. Angle Orthod 2008;78:752–760.

Intra-alveolar Transplantation Invasion of the biologic width by extensive caries, dental traumatic injuries, endodontic perforations, or subgingival prosthetic preparations can lead to serious consequences for the marginal periodontium and its homeostasis. The concept of the biologic width is mostly based on the work of Gargiulo et al,1 who observed healthy periodontium (cadaver study) and found the following average vertical dimensions: a connective tissue attachment of 1.07 mm, an epithelial attachment of 0.97 mm, and a sulcular depth of 0.69 mm. Similarly, Vacek et al 2 noted an average vertical distance of approximately 2.00 mm between the alveolar bone crest and the bottom of the gingival sulcus; they reported biologic widths as narrow as 0.75 mm in some individuals and 4.30 mm in others. Tal et al 3 and Günay et al4 revealed that the placement of restoration margins closer than 2 mm toward the alveolar bone level resulted in gingival inflammation and subsequent loss of connective tissue and alveolar bone height, clinically visible as periodontal recessions or deepened periodontal pockets. As a consequence, Ingber et al5 and Padbury et al6 concluded that a minimum vertical distance of 3 mm should be provided between restoration margins and the alveolar bone crest. Various treatment modalities to maintain the biologic width in teeth affected by crownroot fractures and to develop the adequate ferrule design7 have been described in the literature. Traditional treatment of complicated crown-root fractures has been crown lengthening by resective osseous surgery. 8 Additional therapeutic options have been orthodontic forced eruption,9–11 extraction of the affected tooth and replacement by a fixed partial denture or an endosseous implant,12, 13 and surgical

extrusion of the root fragment.14, 15 In 1978, Tegsjö et al 14 first developed the intra-alveolar dental transplantation, also referred to as surgical extrusion of teeth fractured by trauma . The surgical procedure was based on the biologic behavior of dental replantation after avulsion. This method allowed the direct observation of the root, favoring a better therapeutic orientation and rotation of the root fragment. The basic principle behind tooth extrusion is to move the affected area to a supragingival position, providing room for the reestablishment of the biologic width. It is a one-step procedure, safe, simple, and less time-consuming for teeth with horizontal and oblique cervical root fractures. It maintains an intact dental arch, preserving the esthetic and mastica tory efficiency of the dentition.

Diagnosis and Clinical Examination The diagnostic techniques available for evaluating pulpal and periodontal healing subsequent to trauma are inadequate.16 Pulp testing and imaging (periapical radiographs and cone beam computed tomography [CBCT]) assess only limited parameters of healing. Diagnosis is critical immediately after the injury, when there is active healing in pulp and periodontium and when complications such as pulpal necrosis and root resorption might be anticipated.16 A steep occlusal exposure of the injured anterior region (using a size 2 film, such as DF 58 [Ultra-Speed, Kodak], EP 21 [Ekta-Speed Plus, Kodak], or a similarly sized sensor for digital radiography) will provide a clear depiction of most apical and midroot fractures, lateral luxations, and alveolar fractures.17 An exposure of each traumatized tooth, taken at the standard periapical bisecting angle (using a size 1 film, such as DF 56 [UltraSpeed] or EP 11 [Ekta-Speed Plus], or similar sensor), will reveal cervical root fractures and other tooth displacements.17 Intrusive luxation injury and late root development predispose to pulpal necrosis. Studies have shown a direct relationship between pulpal necrosis and the apical diameter of the intruded tooth.18, 19 Typical clinical signs of the presence of a crown-root fracture are pain during chewing and a variably expressed mobility of the coronal tooth fragment. The oral extension of the fracture line is often difficult to assess radiographically because of its mostly perpendicular position to the central beam, the close proximity of the fragments, and the overlap of the fracture line with the alveolar bone. The direction and extension of crown-root fractures are mostly determined by the direction of the

traumatic force afflicting the tooth. In anterior teeth, the fracture line typically originates somewhat coronal to the gingival margin on the vestibular aspect of the crown and ends subgingivally close to the alveolar bone crest on the lingual aspect of the tooth20 (Fig 9-1). Subgingival fracture lines in close proximity to the alveolar bone, however, imply considerable challenges for subsequent restorative interventions, including the potential for violation of the biologic width.20

Fig 9-1 Thirty-three possible lines of crown and crown-root fractures. (Reprinted from Andreasen et al20 with permission.)

Surgical Techniques and Adjunctive Procedures Intra-alveolar transplantation (surgical extrusion technique) can be a successful procedure in properly selected cases. Several short- and long-term studies have demonstrated the clinical success rate of this technique and suggested that this method is much more economical than implant or fixed partial denture treatment.15, 21, 22

The surgical extrusion technique was first described by Tegsjö et al. 14 A full-

thickness flap was reflected on both the buccal and lingual sides of the tooth and vertical releasing incisions were made buccally. The tooth repositioning was carried out by manipulation of the root apex, which was previously exposed by apical ostectomy. Following tooth extrusion, an autologous bone graft was placed apical to the root to achieve positional stability and prevent relapse. Because no splinting was recommended, the grafting procedure was considered critical for maintaining immediate tooth stability.14, 21 Years later, Kahnberg 21, 22, 23 simplified the surgical extrusion technique by eliminating both the ostectomy and the autologous bone graft on the root apical area. He performed a gentle and careful luxation only until the desired tooth extrusion was achieved. In one publication he described the surgical extrusion of teeth with cervical root fractures, totaling 58 single roots in 53 patients.22 Two different approaches were used. In group I, the procedure involved flap operation with apical exposure and bone transplant above the extruded root. In group II, the roots were extruded by careful marginal luxation, and interdental sutures and surgical dressing were used for retention. The mean observation times were 5.5 years in group I and 2.4 years in group II. Apical root shortening caused by surface resorption was seen in 17 roots, although no case was progressive in nature. Proportionally, apical resorption occurred more frequently in group I than in group II. The results encouraged further use of the method, especially with the simplified surgical approach used in group II, and a favorable overall tooth survival rate was reported.22 Different instruments have been used to perform surgical extrusion: periotomes,24 forceps, elevators,20 carvers,22 crown removal hammers,10 Fedi chisels, pedodontic levers, and pedodontic forceps.25 Immobilization is usually achieved with interdental interrupted sutures and surgical dressing.17, 20 In a clinical report, Kim et al25 outlined the application of the modified surgical extrusion technique to solve difficult clinical cases resulting from invasion of the biologic width and endodontic compromise. Intra-alveolar transplantation with 180degree rotation has been recently illustrated by Chung et al.26 At the 1-year followup, the replanted tooth had normal function, and radiographic examination revealed no obvious inflammatory root resorption.26 Splinting has been broadly accepted as a necessary procedure for replanted or luxated teeth. Regardless of the duration of the extra-alveolar period, splinting does not improve the periodontal healing following replantation and also can have an adverse effect by increasing the replacement resorption (ankylosis). Few studies show that functional stimulus can prevent or eliminate root resorption by replacement.27, 28 A possible explanation is that functional stimulus decreases

osteogenesis and increases fibrous healing, a process known to occur in bone fractures because of improper splinting.10 In particular, this notion was supported by a laboratory animal study in monkeys, where ankylosis was significantly less extensive in teeth without splinting than in splinted teeth.27

Case Report The maxillary left central incisor of a 75-year-old man presented a horizontal crown-root fracture and loss of the metal-ceramic crown that had been retained for longer than 30 years. Clinical evaluation showed a necrotic, equigingival root fragment, no detectable caries, and very little cervical crown ferrule. Bone sounding measurements were used to calculate the amount of supra-alveolar structure needed to obtain an adequate crown ferrule (Fig 9-2a). The radiographic examination revealed no previous endodontic treatment or periapical lesion and no periodontal breakdown (Fig 9-2b). A CBCT diagnostic image identified the relationship of the root fragment to the buccal plate to be a Class I sagittal root position29 (Fig 9-2c). After the administration of local anesthetic and antibiotics, extremely conservative surgical extrusion was performed with the use of a Powertome 100s periotome (Westport Medical), which initiated the root luxation by reciprocating motion (Fig 9-2d). Then a pedodontic forceps was used to reposition the tooth coronally at the desired level (Fig 9-2e). Immobilization was obtained by simple interrupted interproximal sutures and relied on the blood clot formation in the alveolus immediately after the extrusion (Fig 9-2f). No splinting was necessary. The patient was instructed to rinse with 0.12% chlorhexidine gluconate solution twice a day for 2 weeks and follow a liquid diet for 2 weeks. The immediate postoperative radiograph revealed a radiolucent gap around the periapical area (Fig 9-2g). A prompt reduction in mobility over the first month suggested the initial healing of the periodontal ligament. Endodontic treatment with absolute isolation was performed approximately 5 weeks postoperatively (Fig 9-2h). Clinical examination at 13 weeks revealed nearly normal tooth mobility, and radiographic analysis revealed no endodontic problems. It was decided that the restorative phase could begin (Figs 9-2i to 9-2l). A circumferential chamfer with rounded internal line angles was prepared. Medium and coarse diamond burs were used for gross tooth preparation, and preparation was finished with a fine diamond bur. The width of the chamfer was 0.7 mm. Cervical margins were placed 0.5 mm subgingivally for esthetic requirements. Sharp edges and irregularities were corrected to minimize stress concentration.

Fig 9-2 (a) Bone sounding of the root fragment. (b) Initial periapical radiograph. (c) Initial CBCT analysis of cross section 9. (d) Atraumatic extraction with a Powertome. (e) Arrested extraction. (f) Interproximal interrupted sutures. (g) Postoperative radiograph. (h) Completed endodontic treatment at 5 weeks. (i) Periapical radiograph at 13 weeks. (j) Core buildup and tooth preparation. (k) Anterior view of the tooth preparation. (l) Occlusal view of the tooth preparation.

Retraction cord was used to isolate the subgingival finish line. Complete-arch impressions were made with a silicone impression material. A provisional crown

was provided during prosthetic treatment (Fig 9-2m). A metal-ceramic crown was fabricated and, at the first try-in, complete seating, marginal adaptation, esthetic appearance, and occlusion were assessed. The permanent crown was cemented with self-adhesive resin cement (Figs 9-2n to 9-2r). A periapical radiograph was taken after 6 months of healing (Fig 9-2s). The CBCT analysis identified a slight collapse of the buccal plate and an apical socket gap filled with bone (Fig 9-2t).

Fig 9-2 (cont) (m) Provisional restoration. (n) Try-in of the metal-ceramic crown. (o) Cemented metal-ceramic crown. (p) Occlusal view of the metal-ceramic crown. (q) Lingual view of the metal-ceramic crown. (r) Periapical radiograph at the time of cementation. (s) Periapical radiograph at 6 months. (t) CBCT cross section at 6 months postsurgery.

Periodontal Healing and Histologic Evaluation of Surgical Outcome

Evaluation of the periodontal repair on transplanted or surgically extruded teeth usually shows surface root resorption and slight remodeling of the marginal bone.30 There are two possible explanations for this phenomenon: (1) surgical trauma during luxation of the root and (2) dehydration of the exposed periodontal ligament cells. Previous studies have shown that the viability of the cementoblasts along the root surface can be reduced, depending on the extraalveolar period.31–33 Fixation of the extruded tooth is usually accomplished only by means of sutures and periodontal dressing. This method seems to allow for some mobility and functional stimulation throughout the healing period, eliciting the reorientation of the periodontal ligament fibers and favoring the prognosis by preventing the ankylosis.28, 34 Clinically stable mobility of the extruded teeth can be achieved within a few weeks and maintained during the observation period of transplanted teeth through the use of the nonrigid fixation technique.35, 36 Kim et al37 monitored histologic changes in the periodontal ligament after surgical extrusion at 7, 14, 45, 90, 120, and 180 days. The functional requisites of the periodontal ligament are dependent on the Sharpey fibers, which are normally oriented between the root and the alveolar bone. Although the ruptured periodontal ligament fibers joined together soon after surgery, it was only at 45 days after surgical extrusion that most of the area around the root presented a dense and functional periodontal ligament, also called restitutio ad integrum.38 This functional observation at 45 days coincided with reduced dental mobility after the clinical procedure. On the other hand, the nonstandard positioning of the root within the socket may lead to uneven formation and distribution of the new periodontal ligament. Factors such as surface resorption, replacement resorption, ankylosis, and active inflammatory resorption may have contributed to variations in histologic events in the different root thirds. The different repairs and degrees of resorption were not uniform; nevertheless, root resorption was seen in all root segments.37 Andreasen38 suggested that root resorption could be related to the extent of damage to the periodontal ligament and/or the root surface as a result of the luxation period and nonstandard levels of physical trauma applied during extraction. Rotating movements during extraction create high compression and tensile forces in the infrabony parts of the periodontal ligament because of the irregular shape of the root.

Indications and Contraindications Clinical studies have demonstrated that intra-alveolar transplantation is successful in the management of complicated crown-root fractures to improve the ferrule effect,7,

39, 40

for unerupted teeth,41, 42 for intruded teeth,43, 44 between two implants, or where tooth extraction and implant placement would compromise the soft tissue esthetics. Caliskan et al40, 43 reported that the surgical extrusion technique might be an alternative to orthodontic forced eruption. The contraindications to this procedure are short root trunks and primary dentition.20 The incidence of crown-root fractures has been reported to be 5% in the permanent dentition.45 The most frequent causes are injuries inflicted by falls, blows, and sports, bicycle, or car accidents; fractures most often involve the anterior teeth, especially the maxillary central incisors and less commonly the mandibular central incisors and maxillary lateral incisors.46–48 Frontal and horizontal impacts can result in a crown fracture that extends longitudinally (with or without pulpal involvement) to the subgingival area.20, 49 Fractures of the crown may be restored with composite resin restoration or a complete-coverage restoration. Fractures of the middle or apical third of the root may heal spontaneously after root canal treatment.20 Intrusive luxation is an uncommon type of dental injury in the permanent dentition and usually involves maxillary teeth. Intrusion is the most complicated and severe luxation injury and, not surprisingly, yields the poorest prognosis. Complications include pulpal necrosis, external root resorp tion, and loss of marginal bone support.20 The optimal treatment for intruded permanent teeth has not been determined because of the small number of published studies and the complicated nature of the injury. Techniques suggested include no treatment (to allow reeruption) and surgical or orthodontic tooth repositioning.20 Surgical repositioning might be indicated only when the tooth is displaced into the vestibule or through the floor of the nose.50 Andreasen et al20 and Jacobsen and Modéer50 reported that immature teeth will normally reerupt spontaneously, whereas teeth with closed apices should benefit from orthodontic treatment.

Advantages and Disadvantages The major advantage of intra-alveolar transplantation over orthodontic extrusion is the reduction of the operative time. The procedure also allows rotation of the extruded fragment and leads to a stable root position. Compared with surgical crown lengthening, the intra-alveolar transplantation technique is very conservative. It maintains the supportive and protective periodontal tissue and its architecture. A limitation of this technique is the need for a minimum 1:1 crown-root ratio, which is not always possible, especially when horizontal fractures or caries have

occurred beyond the level of the alveolar bone crest.51 In addition, when the tooth fracture has been established too apical within the alveolus or when the remnant root remains structurally weak, the risk of root fracture is high. In such cases, orthodontic forced eruption with endodontic treatment remains the treatment of choice. Like orthodontic forced eruption,9 intra-alveolar transplantation may compromise esthetics by decreasing cervical root diameter, reducing the cervical volume of dentin, and initiating buccal plate collapse. The last outcome will affect the emergence profile, leading to overcontoured restorations.15 On the other hand, bonding to root surface always represents a critical interface because the composition and morphology of these complex tissues are impossible to standardize. Therefore, bonding to dentin and cementum is not yet as predictable as is bonding to enamel.52

Complications Surface root resorption, cervical resorption, and ankylosis should be regarded as risk factors to the success of intraalveolar transplantation. Experimental findings53–55 suggest that preservation of the periodontal ligament and cementoblastic layer vitality are critical factors for prevention of resorption and ankylosis. Kahnberg,22 after an observation time of 5.5 years, reported root resorption located in the apical area of the teeth, resulting in a certain shortening of the roots in 17 of 58 roots. However, all teeth functioned with normal or nearly normal mobility. Marginal bone loss occurred in only one instance, and clinically pathologic pockets were not found in any of the patients.

Prognosis and Clinical Outcomes The prognosis of teeth managed with intra-alveolar transplantation is related to the periodontal ligament healing, gingival and periapical healing, the type and duration of splinting, and the completion of endodontic therapy. 14, 20, 23 Splinting that allows tooth movement during healing and is maintained for a minimal time period decreases the risk of ankylosis. One week of splinting is usually sufficient to create periodontal support to maintain the avulsed tooth in position.20 However, Berude et al53 found no significant difference in the periodontal healing patterns of physiologically splinted, rigidly splinted, and nonsplinted replanted teeth. Caliskan and Tekin41 presented a case report of an incompletely erupted maxillary central incisor with crown dilaceration in a 12-year-old boy. The tooth

was repositioned with surgical extrusion and endodontically treated through the use of calcium hydroxide paste. Clinical and radiographic examination 2 years after completion of the combined surgical and endodontic treatment revealed periapical healing and no signs of root resorption. Caliskan et al40 reported a clinical study where a combined surgical and endodontic treatment was performed in 20 cases of crown-root fracture. At the follow-up examinations, which varied between 6 and 36 (mean 14.5) months, in all but one case, they found no radiographic or clinical signs of progressive root resorption, marginal bone loss, or periapical disease. Kirzioglu and Karayılmaz56 presented the successful results of the surgical extrusion of a complicated crownroot fracture affecting an immature permanent incisor in a 9-year-old boy. Examination 36 months after the trauma indicated that the treatment had provided functional and esthetic results. In a 10-year follow-up study of intra-alveolar transplantation, Kahnberg15 found that only 1 of 19 teeth subjected to surgical extrusion was extracted because of cervical resorption 8 years after the surgery. A remodeling process was observed at the level of marginal bone and alveolar spaces between the cortical bone wall and the root after the surgical extrusion. In addition, a slight alteration, not exceeding 0.5 mm, was noted at the apical portion in five roots, but the finding had no clinical implications. All extruded teeth received different types of restorations, and no clinical or radiographic signs of pathologic alterations were observed. The long-term results of surgical extrusion of anterior teeth with crown-root fractures are presented in Table 9-1.20, 22, 40, 57

Summary Experience suggests that intra-alveolar transplantation is an effective treatment

option for crown-root fractures. Although the indications for dental implant therapy, including single-tooth replacement, have been broadened dramatically, the decision whether to conserve the natural tooth or to place an implant should be based on a number of criteria, including systematic factors, esthetic considerations, prosthetic restorability, cost, and patient preference. Careful planning is most important for the success of a replanted tooth. Further studies, including CBCT analyses, are needed to evaluate surgical techniques that incorporate minimally traumatic devices and to assess the longevity and preservation of the buccal plate.

References 1. Gargiulo AW, Wentz FM, Orban B. Dimensions and relations of the dentogingival junction in humans. J Periodontol 1961;32: 261–267. 2. Vacek JS, Gher ME, Assad DA, Richardson AC, Giambarresi LI. The dimensions of the human dentogingival junction. Int J Periodontics Restorative Dent 1994;14:154–165. 3. Tal H, Soldinger M, Dreiangel A, Pitaru S. Periodontal response to long-term abuse of the gingival attachment by supracrestal amalgam restorations. J Clin Periodontol 1989;16:654–659. 4. Günay H, Seeger A, Tschernitschek H, Geurtsen W. Placement of the preparation line and periodontal health—A prospective 2-year clinical study. Int J Periodontics Restorative Dent 2000;20: 171–181. 5. Ingber JS, Rose LF, Coslet JG. The “biologic width”—A concept in periodontics and restorative dentistry. Alpha Omegan 1977;70: 62–65. 6. Padbury A Jr, Eber R, Wang HL. Interactions between the gingiva and the margin of restorations. J Clin Periodontol 2003;30:379–385. 7. Juloski J, Radovic I, Goracci C, Vulicevic ZR, Ferrari M. Ferrule effect: A literature review. J Endod 2012;38:11–19. 8. Pontoniero R, Carnevale G. Surgical crown lengthening: A 12-month clinical wound healing study. J Periodontol 2001;72: 841–848. 9. Ingber JS. Forced eruption. 2. A method of treating nonrestorable teethperiodontal and restorative considerations. J Periodontol 1976;47:203–216. 10. Heithersay GS. Combined endodontic-orthodontic treatment of transverse root fractures in region of the alveolar crest. Oral Surg Oral Med Oral Pathol 1973;36:404–4l5. 11. Goldson L, Malmgren O. Orthodontic treatment of traumatized teeth. In: Andreasen JO (ed). Traumatic Injuries of the Teeth, ed 2. Copenhagen: Munksgaard, 1981:385–411.

12. Villat C, Machtou P, Naulin-Ifi C. Multidisciplinary approach to the immediate esthetic repair and long-term treatment of an oblique crown-root fracture. Dent Traumatol 2004;20:56–60. 13. Leroy RL, Aps JK, Raes FM, Martens LC, De Boever JA. A multidisciplinary treatment approach to a complicated maxillary dental trauma: A case report. Endod Dent Traumatol 2000;16:138–142. 14. Tegsjö U, Valerius-Olsson H, Olgart K. Intra-alveolar transplantation of teeth with cervical root fractures. Swed Dent J 1978;2:73–82. 15. Kahnberg KE. Intra-alveolar transplantation. 1. A 10-year followup of a method for surgical extrusion of root fractured teeth. Swed Dent J 1996;20:165–172. 16. Andreasen FM. Transient apical breakdown and its relation to color and sensibility changes. Endod Dent Traumatol 1986;2:9–19. 17. Andreasen JO, Bakland LK, Flores MT, Andreasen FM, Andersson L. Traumatic Dental Injuries: A Manual, ed 3. Chichester, England: WileyBlackwell, 2011. 18. Andreasen FM, Vesterqaard PB. Prognosis of luxated permanent teeth: The development of pulp necrosis. Endod Dent Traumatol 1985;1:207–220. 19. Andreasen FM, Zhijle Y, Thomson BL. Relationship between pulp dimensions and development of pulp necrosis after luxation injuries in the permanent dentition. Endod Dent Traumatol 1986; 2:90–96. 20. Andreasen JO, Andreasen FM, Tsukiboshi M. Crown-root fractures. In: Andreasen JO, Andreasen FM, Andersson L (eds). Textbook and Color Atlas of Traumatic Injuries to the Teeth, ed 4. Oxford, England: Blackwell, 2007:314–334. 21. Kahnberg KE. Intraalveolar transplantation of teeth with crownroot fractures. J Oral Maxillofac Surg 1985;43:38–42. 22. Kahnberg KE. Surgical extrusion of root-fractured teeth: A followup study of two surgical methods. Endod Dent Traumatol 1988; 4:85–89. 23. Warfvinge J, Kahnberg KE. Intraalveolar transplantation of teeth. 4. Endodontic considerations. Swed Dent J 1989;13:229–233. 24. Kim CS, Choi SH, Chai JK, Kim CK, Cho KS. Surgical extrusion technique for clinical crown lengthening: Report of three cases. Int J Periodontics Restorative Dent 2004;24:412–421. 25. Kim HS, Tramontina VA, Passanezi E. A new approach using the surgical extrusion procedure as an alternative for the reestablishment of biologic width. Int J Periodontics Restorative Dent 2004; 24:39–45. 26. Chung MP, Wang SS, Chen CP, Shieh YS. Management of crown-root fracture tooth by intra-alveolar transplantation with 180-degree rotation and suture

fixation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010;109:e126– e130. 27. Andreasen JO. The effect of splinting upon periodontal healing after replantation of permanent incisors in monkeys. Acta Odontol Scand 1975;33:313–323. 28. Kristersen L, Andreasen JO. The effect of splinting upon periodontal and pulpal healing after autotransplantation of mature and immature permanent incisors in monkeys. Int J Oral Surg 1983; 12:239–249. 29. Kan JKJ, Roe P, Rungcharassaeng K, et al. Classification of sagittal root position in relation to the anterior maxillary osseous housing for immediate implant placement: A cone beam computer tomography study. Int J Oral Maxillofac Implants 2011;26:873–876. 30. Andreasen JO. Luxation of permanent teeth due to trauma. A clinical and radiographic follow-up study of a 189 injured teeth. Scand J Dent Res 1970;78:273–286. 31. Andreasen JO, Kristerson L. The effect of extra-alveolar root filling with calcium hydroxide on periodontal healing after replantation of permanent incisors in monkeys. J Endod 1981;7:349–354. 32. Pogrel MA. Evaluation of over 400 autogenous tooth transplants. J Oral Maxillofac Surg 1987;45:205–211. 33. Söder PO, Otteskog P, Andreasen JO, Modéer T. Effect of drying on viability of periodontal membrane. Scand J Dent Res 1977; 85:164–168. 34. Oikarinen K. Tooth splinting: A review of the literature and consideration of the versatility of a wire-composite splint. Endod Dent Traumatol 1990;6:237– 250. 35. Tsukiboshi M. Autogenous tooth transplantation: A reevaluation. Int J Periodontics Restorative Dent 1993;13:120–149. 36. Magheri P, Grandini R, Cambi S. Autogenous dental transplants: Description of a clinical case. Int J Periodontics Restorative Dent 2001;21:36–71. 37. Kim SH, Tramontina VA, Ramos CA, Prado AM, Passanezi E, Greghi SL. Experimental surgical and orthodontic extrusion of teeth in dogs. Int J Periodontics Restorative Dent 2009;29:435–443. 38. Andreasen JO. Analysis of topography of surface and inflammatory root resorption after replantation of mature permanent incisors in monkeys. Swed Dent J 1980;4:135–144. 39. Caliskan MK. Surgical extrusion of a cervically root-fractured tooth after apexification treatment. J Endod 1999;25:509–513. 40. Caliskan MK, Turkum M, Gomel M. Surgical extrusion of crownroot-fractured teeth: A clinical review. Int Endod J 1999;32:146–151.

41. Caliskan MK, Tekin U. Surgical extrusion of a partially erupted and crown dilacerated incisor: Case report. Dent Traumatol 2008;24:228–230. 42. Saad AY, Abdellatief EM. Surgical repositioning of unerupted anterior teeth. J Endod 1996;22:376–379. 43. Caliskan MK. Surgical extrusion of a completely intruded permanent incisor. J Endod 1998;24:381–384. 44. Caliskan MK, Gomel M, Turkum M. Surgical extrusion of intruded immature incisors. Case report and review of the literature. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998; 86:461–464. 45. Andreasen JO. Etiology and pathogenesis of traumatic dental injuries. A clinical study of 1,298 cases. Scand J Dent Res 1970; 78:329–342. 46. Forsberg CM, Tedestam G. Etiological and predisposing factors related to traumatic injuries to permanent teeth. Swed Dent J 1993;17:183–190. 47. Shulman JD, Peterson J. The association between incisor trauma and occlusal characteristics in individuals 8–50 years of age. Dent Traumatol 2004;20:67– 74. 48. Kaste LM, Gift HC, Bhat M, Swango PA. Prevalence of incisor trauma in persons 6–50 years of age: United States, 1988–1991. J Dent Res 1996;75(spec No.):696–705. 49. Fariniuk LF, Ferreira EL, Soresini GC, Cavali AE, Baratto Filho F. Intentional replantation with 180 degrees rotation of a crownroot fracture: A case report. Dent Traumatol 2003;19:321–325. 50. Jacobsen I, Modéer T. Traumatic injuries to the teeth. In: Magnusson BO, Koch G, Poulsen S (eds). Pedodontics: A Systematic Approach. Copenhagen: Munksgaard, 1981:chap 14. 51. Grossmann Y, Sadan A. The prosthodontic concept of crown-toroot ratio: A review of the literature. J Prosthet Dent 2005;93:559–562. 52. Grobler SR, Rossouw JR, Tygerberg TJ. In vitro, relative microleakage of five restorative systems. Int Dent J 1999;49:47–52. 53. Berude JA, Hicks ML, Sauber JJ, Li SH. Resorption after physiological and rigid splinting of replanted permanent incisors in monkeys. J Endod 1988;14:592–600. 54. Andreasen JO. Relationship between cell damage in the periodontal ligament after replantation and subsequent development of root resorption. A time related study in monkeys. Acta Odontol Scand 1981;39:15–25. 55. Andreasen JO. Effect of extra-alveolar period and storage media upon periodontal and pulpal healing after replantation of mature permanent incisors in monkeys. Int J Oral Surg 1981;10:43–53. 56. Kirzioglu Z, Karayılmaz H. Surgical extrusion of a crown-root fractured

immature permanent incisor: 36 month follow-up. Dent Traumatol 2007;23:380–385. 57. Tegsjö U, Valerius-Olsson H, Frykholm A, Olgart K. Clinical evaluation of intra-alveolar transplantation of teeth with cervical root fractures. Swed Dent J 1987;11:235–250.

Autotransplantation and Replantation Teeth can be lost for a variety of reasons: extensive caries, trauma, and problems such as cracks and fractures. In addition, aplasia (congenital absence) of the teeth occurs in a small number of individuals. Management of such situations requires careful evaluation of the various options available. The purpose of this chapter is to describe options that can be considered in these complex treatment planning situations. The procedures described are typically performed by dental specialists—endodontists and oral and maxillofacial surgeons —as well as general dentists with an interest in these treatment options. However, prosthodontists and restorative general dentists should find it useful to consider how the procedures covered in this chapter can be incorporated in complex treatment planning situations. The focus of this chapter is less on the surgical technical procedures themselves and more on descriptions of the clinical situations in which autotransplantation and replantation can be of benefit to patients. Usually performed in young patients, autotransplantation is a surgical procedure in which a tooth (graft) is removed from one part of the dental arch and implanted in a different part of the arch.1 One example is the removal of developing premolars and their subsequent transplantation to areas of the maxillary anterior region where teeth are missing because of trauma, extensive caries, or aplasia. Another common example is the transplantation of developing third molars to areas where nonrestorable molars have been lost to extensive caries (Fig 10-1) or where premolar teeth are congenitally missing beneath retained primary teeth (aplasia). These two examples illustrate a common concept—that of moving a tooth surgically (autotransplantation) from one position to another. There are, however, some

significant differences between molar transplantation and transplantation involving premolars to anterior tooth locations. These differences are described in more detail later in the chapter.

Fig 10-1 When a first or second molar is nonrestorable, a third molar may be available to replace the tooth through the process of autotransplantation. The more apical the donor tooth is, the less distal bone will be available when the donor tooth is placed in its new position. (Reprinted from Tsukiboshi2 with permission.)

Replantation of teeth can be placed in two distinct categories. The most common type of replantation is replanting of an avulsed tooth. It is a procedure that is well recognized worldwide and has probably saved thousands of teeth since it first became recognized as a predictable procedure3 (Fig 10-2).

Fig 10-2 Traumatic tooth avulsion can have a successful outcome if the replantation is performed in a timely manner. (a) The radiograph shows the alveolar socket from which the tooth has been avulsed. (b) The avulsed tooth has been replanted, and a minimal splint has been placed to stabilize the tooth during healing of the periodontal ligament. The soft tissue is also sutured tightly around the replanted tooth.

The second type of replantation is performed when conventional endodontic treatment cannot accomplish the desired result, and apical surgery is not practical for some reason. The tooth may then be extracted and the problem corrected, by placement of an apical filling, for example, and the tooth can be replanted in its original alveolar socket. This is often referred to as intentional replantation but should probably more accurately be referred to as extraction/replantation4 (Fig 103).

Fig 10-3 (a) Typical situation in which a mandibular second molar is situated so that an apical surgical approach is difficult. (b) Extraction/ replantation has been done; the procedure has the added advantage of allowing the tooth to be examined for possible cracks in the root. The 1-year follow-up radiograph shows apical healing.

General Principles In the complex treatment of missing teeth, a number of factors affect the decision to consider transplantation or replantation.

Age For some procedures such as tooth transplantation, the stage of root development of the graft tooth must be carefully evaluated. The optimal time for transplantation is usually when the developing tooth to be transplanted has reached a stage where the root is two-thirds to three-quarters completed. This allows revascularization of the pulp after the tooth has been placed in its new alveolar socket and often leads to

some continued root formation (1.0 to 2.5 mm).5 Fully formed teeth may also be grafted but will require root canal therapy, while those undergoing revascularization will usually not need any endodontic therapy. The outcome for transplanted mature teeth is less successful than that for immature teeth.6 With respect to replantation, age is a less important factor. Traumatically avulsed teeth, if replanted in a timely fashion—preferably within 15 minutes of dry time—can recover successfully but will need root canal therapy. Endodontic treatment is absolutely necessary and should be initiated within the first 2 weeks postreplantation. The only exception to routine root canal therapy is if the avulsed tooth is very immature and has a wide apical opening (usually observed within the first year of eruption). In such a case, it is reasonable to allow an attempt at revascularization, but these teeth require active monitoring.7

General health Usually transplantation and replantation are not contraindicated unless the patient has a very debilitating disease. Bisphosphonate use may prevent use of these procedures.8 Diabetes, if under control, should not be a contraindication, but careful monitoring is advised.9

Use of antibiotics The use of antibiotics has become fairly routine in both transplantations and replantations, although the dental literature does not contain extensive data to support its use.10, 11 However, it is very likely that the periodontal ligament (PDL) attached to the root surfaces of avulsed teeth will contain numerous microorganisms. For that reason, avulsed teeth should be vigorously rinsed prior to replantation. However, the clinician should expect all teeth, transplant or replant candidates, to be contaminated to a lesser or greater degree prior to implantation. The presence of bacteria and other contaminants will generate an inflammatory response in the alveolar socket, and the immune system will be activated to deal with the contaminants. Systemic antibiotics will aid the immune system in battling the bacteria and for that reason may be indicated. More important than the systemic antibacterial effort is the local control of bacteria, namely the application of disinfectants such as chlorhexidine to the tissues around the implanted tooth and the general cleanliness of the wound site. The latter is ensured by the patient’s use of a soft-bristle toothbrush to clean the teeth and surrounding tissues.12

One source of bacterial contamination that is not often recognized is the use of rough wire splints, heavy bars (eg, Erich arch bar), or big masses of resin to stabilize the implanted teeth. Supporting splints should be flexible, thin, and located away from the gingival tissues so that necessary hygiene can be maintained.13

Diet Healing of the PDL following transplantation or replantation appears to be aided by moderate function of the involved teeth. That is one reason for the use of flexible splints and also supports the notion that gentle chewing or biting should be encouraged.14, 15

Root resorption Many dentists have been hesitant to consider transplantation or replantation because of concern about possible root resorption. The concern is not misplaced because root resorption can occur, sometimes even under the most favorable circumstances. The etiology of resorption, however, is much better understood today than it was even a few decades ago. The three principal causes of the resorptive process are necrotic tissue, the presence of bacteria, and direct trauma to the cementum covering the root.16–18 The necrotic tissue may be dead PDL, cementum, pulp, or all three. Bacteria may be present on the root surface and the necrotic pulp tissue. Both necrotic tissue and bacteria will stimulate inflammation, which plays a role in both the initiation and the continuation of resorption.19 Minimizing the effect that necrotic tissue and bacteria have on the healing forms the biologic basis for these transplantation or replantation procedures, along with the exercise of great care when teeth are extracted for transplantation or replantation. The issue of removing necrotic tissue points to the importance of extirpating necrotic pulp tissue in a timely fashion, optimally about 2 weeks postreplantation of avulsed teeth, followed by completion of root canal treatment.12 In the case of extraction/replantation, no necrotic pulp tissue is present if root canal treatment has been performed prior to the surgery. In the case of transplantation of developing teeth, pulpal revascularization is anticipated. The external root surface is another place for accumulation of necrotic tissue that can easily be contaminated with bacteria. Extensive drying of the PDL tissue prevents healing and often leads to both infection-related and ankylosisrelated resorption.18

In addition to the role of bacteria and necrotic tissue, resorption can also occur following trauma to the cementum layer covering the root. Loss of cementum exposes the dentin to ankylosis-related resorption.20, 21 The two types of resorption mentioned—infection-related (Fig 10-4) and ankylosis-related (Fig 10-5)—are the main types associated with transplantation and replantation (and luxation injuries). Infection-related (inflammatory) resorption follows an initial surface resorption after implantation of a tooth; this will continue under the stimulus of any bacteria present in the root canal. Endodontic therapy that eliminates that bacterial influence will prevent infectionrelated resorption or arrest such resorption if it has already begun12 (Fig 10-6).

Fig 10-4 Infection-related (inflammatory) root resorption has resulted from infected pulpal necrosis in a replanted avulsed tooth. This type of root resorption is preventable and treatable with careful root canal therapy.

Fig 10-5 (a) Ankylosis of a traumatized tooth prevents normal eruption. (b) The radiograph reveals ankylosisrelated (replacement) resorption in which bone has gradually replaced the root. No treatment is available to either prevent or arrest ankylosis-related resorption, which happens in the absence of healing of the PDL in replanted teeth and other luxation injuries.

Fig 10-6 (a) A replanted avulsed tooth has infection-related root resorption resulting from failure to perform root canal therapy in a timely fashion. (b) A radiograph taken 4 years after root canal therapy shows the arrested resorption and bony healing.

Ankylosis-related (replacement) resorption does not depend on the presence of bacteria but is associated with exposure of root dentin (loss of cementum coverage) to adjacent bone and the normal turnover of bone that will affect any uncovered, exposed dentin. Minor areas of ankylosis can sometimes undergo repair with cementum, but usually once ankylosis-related resorption begins, it will continue until the root is replaced with bone. There is currently no known treatment to arrest ankylosis-related resorption.22

Prognosis Autotransplantation has a high rate of long-term success.6, 23–29 Outcomes of replanted avulsed teeth depend to a great degree on (1) the duration of the extra-alveolar drying time and (2) whether root canal therapy was performed in a timely fashion (before infection-related resorption can destroy the root).30–36 Extraction/replantation has a long history of successful outcomes.4, 37

Application The surgical procedures are technique sensitive and require careful attention to numerous details. Excellent descriptions of the technical steps have been provided by Andreasen38 and Tsukiboshi. 2 The emphasis in this chapter is to discuss the factors that influence case selection and the monitoring of outcomes prior to initiation of restorative or prosthodontic treatment planning.

Autotransplantation The procedure referred to as autotransplantation has a long history in dentistry. 39, 40 It usually involves transplanting a molar tooth from one area in the arch to another molar area or transplanting a premolar tooth to an anterior tooth position.

Molar transplantation The indications for this procedure include replacement of an extensively carious nonrestorable first or second molar, a fractured molar, an ankylosed molar, or a congenitally missing second premolar (aplasia). In general, molar transplantation is most suitable for a young patient in whom a still-developing graft tooth can be

transplanted (Fig 10-7). The ideal stage of root development is two-thirds to threequarters complete.41 Transplantation of fully formed teeth is also possible, but such transplanted teeth must also be treated endodontically (Fig 10-8).

Fig 10-7 (a) A maxillary third molar has been transplanted to the area of a first molar that had to be extracted. The patient is a 16-year-old girl, and the third molar is about two-thirds formed, allowing the possibility of revascularization following transplantation. (b) Continued root development can be observed in a radiograph taken 3 months posttransplantation.(c) Continued root formation is evident 19 months after transplantation. (Reprinted from Tsukiboshi2 with permission.)

Fig 10-8 (a) The preoperative radiograph of a 33-year-old woman with a vertical root fracture of the maxillary left second molar reveals an impacted maxillary right third molar that is available for transplantation. (b) Clinical view of the failing tooth. (c) The site is ready to receive the transplant, 45 days after extraction of the fractured molar. (d) Clinical view of the donor tooth, the right third molar. (e) Radiographic evaluation of the implanted donor tooth. (f) The donor tooth is placed with a splint, and the soft tissue is sutured tightly around the graft. (g) Because the donor tooth is fully developed, root canal therapy is done 2 to 3 weeks after the surgery. (h) Clinical appearance 2 years posttreatment. (i) The radiograph reveals good healing and no sign of resorption. (Reprinted from Tsukiboshi2 with permission.)

Radiographic analysis In preparation for the surgical procedure, careful radiographic evaluation of both the donor tooth and the projected graft site must be performed. Cone beam computed

tomography (CBCT) is rapidly becoming a much desired radiologic modality when autotransplantation is considered. It provides important information about all the dimensions of the teeth, the amount of bone (in terms of both remaining bone as well as bone that must be removed), and the location of adjacent important anatomical structures. In the absence of CBCT, a number of preoperative radiographs are needed. For general overview, a panoramic radiograph will provide good information. Then, in addition to conventional periapical radiographs, occlusal views can provide useful information about the horizontal dimensions of the graft teeth. Procedure and monitoring The surgical procedures—extraction of the diseased tooth, socket preparation, and surgical harvesting of the donor tooth—should be done as described in the textbooks referenced earlier.2, 4 Follow-up monitoring involves evaluation of the tissue response around the graft. It is essential that the patient follow prescribed oral hygiene recommendations: The patient should be instructed to brush the site twice daily with a soft toothbrush and swab the site with chlorhexidine for at least 2 weeks. Depending on the amount of new bone needed to support the graft, splinting times can vary between 2 to 4 weeks. Radiographic control includes the first examination after 3 to 4 weeks and a second radiograph taken after another month. Six-month radiographic examinations thereafter for 2 years will provide good information about the treatment outcomes.29 Because the transplantation described would involve an immature tooth graft, it is expected that the pulp will revascularize in its new location in the dental arch. Evidence for such healing includes response to electric pulp testing, typically after 6 months, and accelerated pulp canal obliteration. Unfavorable outcomes such as resorption are usually associated with damage to the PDL attached to the root or with infected pulpal necrosis. Evidence of resorption can usually be diagnosed within 1 to 6 months. Further evidence of a favorable outcome will be continued root growth and eruption of the tooth into normal occlusal contact.28 The prognosis for transplanted immature molars performed in recent decades is very impressive, with success rates in the range of 80% to 100%.6, 7, 23, 24, 26, 27, 29, 42 When a donor tooth has already reached the stage of apical closure, root canal treatment must be performed either prior to replantation or 2 weeks posttransplantation. The graft tooth does not need to be placed in normal occlusal contact at the time of implantation; it will gradually erupt into a normal position. Nor does it have to be in normal proximal contact with adjacent teeth; small

interproximal spaces will close gradually as the teeth under function will move adequately for close contact with adjacent teeth. Because the mature transplanted tooth requires root canal therapy, the question of proper coronal restoration must be addressed. Is it necessary to protect the transplanted tooth with a complete-coverage crown, as is typically recommended for a molar treated endodontically because of carious pulpal involvement? The two situations are quite dissimilar. Cariously involved teeth have usually lost considerable coronal tooth structure in addition to having developed compromised pulpal health. Further, tooth structure not directly lost to caries is often unsupported and provides weak resistance to occlusal impact. Complete-coverage restorations (prosthetic crowns) are clearly indicated for such endodontically treated teeth.43 In contrast, a fully formed intact molar transplanted from the third molar site to the first or second molar location will, after root canal therapy, have a minimal occlusal access opening, leaving all cusps well supported. A conservative occlusal restoration should suffice, but data are not available to definitively decide the issue one way or the other.

Premolar transplantation The indications for this procedure include aplasia (congenitally missing teeth) and accidental loss of premolar or anterior teeth. A fairly common example is the harvesting of a premolar from the maxillary arch, where crowding may exist, and its transplantation to the mandibular arch, where a premolar may be congenitally missing (Fig 10-9). Another good application of the concept of transplantation is in the child or adolescent who has lost an anterior tooth due to a traumatic accident.

Fig 10-9 (a) A maxillary premolar has been transplanted to the site of a congenitally missing mandibular second premolar in a 16-year-old girl. The donor tooth is about two-thirds developed, and revascularization can be expected. (b) Continued root formation is observed 8 months after transplantation. (c) The root canal is obliterated, and the root is fully developed 2 years after transplantation. (Reprinted from Tsukiboshi2 with permission.)

Radiographic analysis As with molar transplantation, information about both the donor tooth and the recipient site must be carefully analyzed and measured. CBCT is a useful method for acquiring all the needed information: the donor tooth’s stage of maturation and root development as well as its dimensions, both vertical and horizontal. The amount of bone present at the recipient site and the condition of the recipient socket can also be assessed. These pieces of information can also be gathered with a number of conventional radiographic views: periapical views with one or two additional horizontal angulations and some occlusal views. These can provide adequate information in the absence of CBCT. Procedure and monitoring The surgical procedures for harvesting the donor tooth and preparing the recipient site are well described in textbooks.2, 38 Suffice it to say here that the dental surgeon must carefully observe the biologic principles that have been developed to protect supporting bone, manage the extraction without damage to the donor tooth PDL and root cementum, and properly place the graft to promote favorable healing. The immediate postoperative appearance should be that of a transplanted tooth hygienically splinted to allow for meticulous oral hygiene: brushing with a soft toothbrush and swabbing with a cotton swab soaked in chlorhexidine. The type of splint should also allow slight movement of the grafted tooth. Rigid splinting does not promote good periodontal healing.13, 44 The soft tissues around the graft should be well adapted and sutured to prevent the tissues from moving away from the graft and further to prevent debris from being pushed into the tissue flap. Antibiotics are usually prescribed. The postoperative follow-up is similar to that observed for molar transplantation; sutures can be removed after 1 week and the splint in about 4 weeks. The progress of healing can be monitored by observation of PDL healing, pulpal sensibility responses, pulp canal obliteration, tooth eruption, and root growth.26 PDL healing can be observed by bony healing, development of an intact lamina dura, and presence of a normal PDL space. A failure to form supporting bone and the appearance of root resorption may be related to bacterial invasion of the pulp during the transplant procedure (infection-related resorption) or damage to the PDL that has resulted in ankylosis-related resorption. The former can be addressed by extirpation of the infected necrotic pulp, while the latter will lead to eventual failure of the graft. Pulpal healing is also readily monitored with electric pulp testing. The pulp

usually begins to respond within 4 to 6 months. Pulp canal obliteration may, however, occur before any response to electric pulp testing.26 If the pulp fails to survive the transplant procedure, bacterial contamination will be the cause and it will be manifested by a lack of pulp canal obliteration. The appearance of an apical lesion along with infection-related root resorption may also be expected. Tenderness to percussion will also be a sign of infection. To save the tooth, endodontic procedures must be initiated immediately. These procedures may include pulp extirpation and root canal filling, or the clinician may attempt to induce ingrowth of reparative tissue into a cleaned and disinfected pulp space (also referred to as pulp regeneration). A major consideration when premolars are transplanted to maxillary incisor locations will be the necessity for careful restorative applications. After the transplanted premolar has erupted into a position near its final destination, it is time to begin reshaping the crown to more closely resemble the tooth it is replacing. The definitive reshaping of the crown can be postponed until the tooth is in a normal position with respect to the adjacent teeth. Proper reshaping, whether it is with resin materials or porcelain, provides the opportunity for creating superior esthetic results. The prognosis for transplanted premolars is good, as has been reported in several studies.26 The positive value of providing a young patient the opportunity to have an esthetic, functional dentition following dental trauma or aplasia cannot be overemphasized.

Replantation There are two situations in which replantation of a tooth may be considered: After a tooth has been traumatically avulsed or accidentally extracted, and when a tooth is purposely extracted to allow close examination for cracks, reshaping of the roots, or placement of a root-end filling.

Replantation of avulsed or accidentally extracted teeth Accidentally extracted teeth are included in this section because such accidents do occur (eg, extraction of the wrong premolar in preparation for orthodontic treatment). These teeth can be replanted and have the additional advantage of being in an aseptic environment that favors healing after replantation, unlike traumatically avulsed teeth that usually are contaminated. The description for management of avulsed teeth therefore also applies to accidentally extracted teeth (Fig 10-10).

Fig 10-10 (a) A 9-year-old boy has an avulsed left central incisor following an accident. (b) The tooth is rinsed and placed in saline while the al veolar socket is examined. (c) The tooth is replanted and splinted, and the tissues around the adjacent tooth are sutured because of some soft tissue trauma. (d) Radiograph of the replanted incisor. (e) Root canal treatment should be initiated, ideally within 2 weeks of the replantation. (f) Successful healing can be expected when the avulsed tooth can be replanted within a few minutes after avulsion (or kept in milk or saline until replantation) and the root canal therapy is initiated within 2 weeks.

Some clinicians still question whether avulsed teeth should be replanted. Successful outcomes from replantation support the notion that in almost all circumstances (with the possible exception of medically compromised patients) avulsed teeth can and should be replanted if possible.45 The components of successful replantations are well recognized and are described briefly here. Urgent care The sooner an avulsed tooth can be replanted, the better the outcome. On-site rinsing of the tooth followed by replantation into its socket is the optimal procedure. If this cannot be accomplished on site, the tooth must be kept moist during transport to a dental facility. In order of preference, acceptable transport media are Hanks’ balanced salt solution (such as in various emergency tooth-saver kits), cold milk, saliva, and finally water, if nothing else is available. When the patient arrives, the dental staff can rinse the tooth and place it in saline while preparing the patient for the replantation (radiographs to examine the socket and clinical examination to see if

the socket is intact with no bone spicules present). The tooth can then be replanted, the soft tissues adapted (and sutured if need be), and a nonrigid hygienic splint placed.12 Follow-up Endodontic treatment is routinely required following replantation of an avulsed tooth. Failure to treat the tooth in a timely fashion, that is, 2 weeks after replantation, will invariably lead to infection-related resorption. What frequently goes unrecognized is that this type of resorptive activity is painless, and the patient is unaware of the loss of tooth structure, sometimes until it is too late to save the tooth. Endodontic treatment can be followed by internal bleaching of the crown if it has discolored, after which the coronal access opening is restored. Unless there has been other damage to the crown, no other treatment is necessary. Another type of root resorption associated with replanted avulsed teeth is ankylosis-related root resorption. The root will gradually be replaced with bone, and the tooth will be ankylosed. This outcome occurs when the root surface was severely damaged in the accident or the tooth was left to dry too long before replantation. It is outside the scope of this chapter to discuss all the variations in treatment and outcomes following avulsions; excellent textbooks are available,46, 47 and a very good (and free) website contains up-to-date information: www.dentaltraumaguide.org.

Extraction/Replantation Dentists have performed extraction/replantation for many years, often with excellent results4, 37 (Figs 10-11 and 10-12). The notion of extracting a tooth, performing apical resection, and filling the apical opening of the root canal is often considered to be a last attempt to save a tooth that otherwise would be extracted and discarded. However, when properly planned in carefully selected situations, this procedure can provide the patient with a treatment option that has many advantages.

Fig 10-11 (a) Radiograph taken 4 years after a motorcycle accident. Root canal treatment was completed 3 months previously because of longstanding pain on biting. The patient continued to experience pain, particularly to lingual pressure. (b) Because of the concern about possible vertical root fracture, the patient agreed to extraction to examine the tooth. The tooth had two roots, and the second canal was missed during initial endodontic treatment. No cracks were found. (c) Apical fillings were placed in the two canal openings, and the tooth was replanted. The 6-year followup shows normal periradicular bone, and the tooth is asymptomatic.

Fig 10-12 (a) After retreatment of an inadequate root canal procedure in the mandibular second molar, the

patient continued to complain of symptoms and agreed to an extraction to allow the tooth to be examined for any cracks. (b) No cracks were found. Apical fillings were placed, and the tooth was replanted. (c) A panoramic radiograph taken 23 years later shows an excellent outcome. (Courtesy of Dr Steve Morrow, Loma Linda, CA.)

Indications Some teeth have very complicated root canal systems. When such teeth need root canal treatment, the outcomes may be compromised by a lack of access for thorough cleaning and disinfection of the root canals, resulting in treatment failures. Other times, instruments may break inside the roots during endodontic treatment, and it may not be possible to retrieve them by the usual methods for retrieval of broken instruments (see chapter 14). It is also not uncommon, after placement of a post and core and cementation of a prosthetic crown, to find that the apical root canal space has been inadequately cleaned and that there is evidence of a developing apical lesion. In these and similar situations, the common treatment approach is endodontic surgery, a procedure with considerable success when properly performed. In a few of these situations, however, the usual approach of apical surgery is complicated by the location of the tooth in the mouth (eg, when an extensive amount of bone covers the root apex) or the proximity of the root tip to an anatomically risky area, such as the mandibular neurovascular tissues. At times there may be a question about the etiology of the apical lesion that may necessitate a close examination of the entire root (eg, possible beginning vertical root fracture). Therefore, when the conventional apical surgery approach is not feasible or would pose excessive risks, an extraction/replantation procedure may be the best choice.

Radiographic analysis For the purpose of determining the etiology and for planning the surgical procedure, CBCT is of great value in cases of extraction/replantation. When that technology is not available, several angulated radiographs should be exposed in addition to the conventional periapical radiograph. While vertical root fractures of endodontically treated teeth often run in the faciolingual direction, which makes them discernible on radiographs, some may be located between the mesiodistal and the faciolingual directions, making detection difficult. Off-angle exposures of films can sometimes show these variations in vertical root fractures. The configurations of the root or roots of the tooth to be treated must be examined carefully. Teeth with divergent roots are difficult to extract intact, as are

teeth with excessive root curvatures. The teeth that are most suitable for this procedure have closely positioned roots (or single straight roots). Short roots are preferable to long roots in these situations.

Procedure and monitoring If the problem tooth has a prosthetic crown, or if a new crown is planned, the extraction may benefit from the removal of the present crown before surgery if it is possible. The extraction must be done with utmost care to protect the root surface cementum and PDL and to prevent fracture of the supporting alveolar bone. Loosening the tooth carefully before it is extracted from its socket will help prevent damage to the root and bone. The loosening may be done with such instruments as the periotome. If the PDL is severed prior to extraction, the surrounding tissue is subjected to less traumatic injury. Following the use of the periotome, the tooth can be extracted with elevators and/or forceps. When the tooth has been removed from its socket, it is placed in saline while the socket is irrigated and examined for any damage to the bone. The socket is protected with moist gauze, on which the patient can bite for the remainder of the extraoral procedure on the tooth. The tooth is examined carefully for any indications of vertical root fracture. Absent a fracture, the root can now be prepared for the root-end filling. Severe apical root curvatures can be removed via resection of the root tip before the apical filling cavity is prepared. The cavity should have a minimum depth into the canal of 3 to 4 mm. Mineral trioxide aggregate is the preferred material for apical fillings.48 When the tooth is ready for replantation, the socket is irrigated vigorously to remove any blood clots that have developed during the time the tooth was out of the socket. The tooth should be replanted without any undue pressure that can cause damage to the PDL and the cementum. It is important to readapt the soft tissue around the tooth; often sutures are beneficial to allow good adaptation of the periodontal tissues. Stabilization of the replanted tooth is not always necessary if the replanted tooth fits snugly back in the socket. If there is room, the tooth can be stabilized by a suture over the crown if the tooth is to receive a prosthetic crown later. If sutures are used for tissue adaptation or for stabilization of the tooth, they can be removed within a week. It is important, as with all dental surgical procedures, to show the patients how to maintain meticulous oral hygiene by using soft toothbrushes and chlorhexidine during the critical period of healing of the periodontal support. Because replanted extracted teeth fit accurately if they have been replanted in the same position as they were preoperatively, healing of the PDL will progress rapidly.

As soon as the PDL has healed completely—usually within 4 to 6 weeks—necessary prosthetic procedures may be performed. The prognosis for extracted/replanted teeth has not been very well assessed, but it may be assumed that they have the same chance to survive as other replanted or transplanted teeth.

Summary When careful surgical procedures are followed, transplantations and replantations may provide patients with quite predictable options in selected situations. Successful healing is related to the care with which the PDL and the root surface cementum are handled. When indicated, root canal therapy is necessary to eliminate intracanal bacterial infection.

References 1. Andreasen JO, Schwartz O, Kofoed T, Daugaard-Jensen J. Transplantation of premolars as an approach for replacing avulsed teeth. Pediatr Dent 2009;31:129–132. 2. Tsukiboshi M. Autotransplantation of Teeth. Chicago: Quintessence, 2001. 3. Hammarström L, Pierce AM, Blomlöf L, Feiglin B, Lindskog S. Tooth avulsion and replantation—A review. Endod Dent Traumatol 1986;2:1–9. 4. Koenig KH, Nguyen NT, Barkhordar RA. Intentional replantation: A report of 192 cases. Gen Dent 1988;36:327–331. 5. Czochrowska EM, Stenvik A, Zachrisson BU. The esthetic outcome of autotransplanted premolars replacing maxillary incisors. Dent Traumatol 2002;18:237–245. 6. Czochrowska EM, Stenvik A, Bjercke B, Zachrisson BU. Outcome of tooth transplantation: Survival and success rates 17–41 years posttreatment. Am J Orthod Dentofacial Orthop 2002;121:110–119. 7. Johnson WT, Goodrich JL, James GA. Replantation of avulsed teeth with immature root development. Oral Surg Oral Med Oral Pathol 1985;60:420– 427. 8. Khan AA, Sándor GK, Dore E, et al. Guidelines for bisphosphonate-associated osteonecrosis of the jaw. J Rheumatol 2008;35: 1391–1397 [errata 2008;35:2084 and 2008;35:1688]. 9. Preshaw PM, Alba AL, Herrera D, et al. Periodontitis and diabetes: A two-way

relationship. Diabetologia 2012;55:21–31. 10. Hammarström L, Blomlöf L, Feiglin B, Andersson L, Lindskog S. Replantation of teeth and antibiotic treatment. Endod Dent Traumatol 1986;2:51–56. 11. Andreasen JO, Storgård Jensen S, Sae-Lim V. The role of antibiotics in preventing healing complications after traumatic dental injuries: A literature review. Endod Top 2006:14:80–92. 12. Flores MT, Andersson L, Andreasen JO, et al. Guidelines for the management of traumatic dental injuries. 2. Avulsion of permanent teeth. Dent Traumatol 2007;23:130–136. 13. Kahler B, Heithersay GS. An evidence-based appraisal of splinting luxated, avulsed and root-fractured teeth. Dent Traumatol 2008;24:2–10. 14. Kaneko S, Ohashi K, Soma K, Yanagishita M. Occlusal hypofunction causes changes of proteoglycan content in the rat periodontal ligament. J Periodontal Res 2001;36:9–17. 15. Mine K, Kanno Z, Muramoto T, Soma K. Occlusal forces promote periodontal healing of transplanted teeth and prevent dentoalveolar ankylosis: An experimental study in rats. Angle Orthod 2005;75:637–644. 16. Andreasen JO. External root resorption: Its implication in dental traumatology, paedodontics, periodontics, orthodontics and endodontics. Int Endod J 1985;18:109–118. 17. Donaldson M, Kinirons MJ. Factors affecting the time of onset of resorption in avulsed and replanted incisor teeth in children. Dent Traumatol 2001;17:205– 209. 18. Andersson L, Bodin I, Sörensen S. Progression of root resorption following replantation of human teeth after extended extraoral storage. Endod Dent Traumatol 1989;5:38–47. 19. Ahangari Z, Nasser M, Mahdian M, Fedorowicz Z, Marchesan MA. Interventions for the management of external root resorption. Cochrane Database Syst Rev 2010;6:CD008003. 20. Andersson L, Blomlöf L, Lindskog S, Feiglin B, Hammarström L. Tooth ankylosis. Clinical, radiographic and histological assessments. Int J Oral Surg 1984;13:423–431. 21. Hammarström L, Blomlöf L, Lindskog S. Dynamics of dentoalveolar ankylosis and associated root resorption. Endod Dent Traumatol 1989;5:163–175. 22. Panzarini SG, Gulinelli JL, Poi WR, Sonoda CK, Pedrini D, Brandini DA. Treatment of root surface in delayed tooth replantation: A review of the literature. Dent Traumatol 2008;24:277–282. 23. Andreasen JO, Hjørting-Hansen E, Joist O. A clinical and radiographic study of 76 autotransplanted third-molars. Scand J Dent Res 1978;78:512–523.

24. Pogrel MA. Evaluation of over 400 autogenous tooth transplants. J Oral Maxillofac Surg 1987;45:205–211. 25. Schwartz O, Bergmann P, Klausen B. Resorption of autotransplanted human teeth: A retrospective study of 291 transplantations over a period of 25 years. Int Endod J 1985;18:119–131. 26. Andreasen JO, Paulsen HU, Yu Z, Bayer T, Schwartz O. A longterm study of 370 autotransplanted premolars. 2. Tooth survival and pulp healing subsequent to transplantation. Eur J Orthod 1990;12:14–24. 27. Akiyama Y, Fukuda H, Hashimoto K. A clinical and radiographic study of 25 autotransplanted third molars. J Oral Rehabil 1998; 25:640–644. 28. Czochrowska EM, Stenvik A, Album B, Zachrisson BU. Autotransplantation of premolars to replace maxillary incisors: A comparison with natural incisors. Am J Orthod Dentofacial Orthop 2000; 118:592–600. 29. Tsukiboshi M. Autotransplantation of teeth: Requirements for predictable success. Dent Traumatol 2002;18:157–180. 30. Andreasen JO, Borum M, Jacobsen HL, Andreasen FM. Replantation of 400 traumatically avulsed permanent incisors. 1. Diagnosis of healing complications. Endod Dent Traumatol 1995;11:51–58. 31. Andreasen JO, Borum M, Jacobsen HL, Andreasen FM. Replantation of 400 traumatically avulsed permanent incisors. 2. Factors related to pulp healing. Endod Dent Traumatol 1995;11:59–68. 32. Andreasen JO, Borum M, Jacobsen HL, Andreasen FM. Replantation of 400 traumatically avulsed permanent incisors. 3. Factors related to root growth after replantation. Endod Dent Traumatol 1995;11:69–75. 33. Andreasen JO, Borum M, Jacobsen HL, Andreasen FM. Replantation of 400 traumatically avulsed permanent incisors. 4. Factors related to periodontal ligament healing. Endod Dent Traumatol 1995;11:76–89. 34. Kinirons MJ, Boyd DH, Gregg TA. Inflammatory and replacement resorption in reimplanted permanent incisor teeth: A study of the characteristics of 84 teeth. Endod Dent Traumatol 1999;15:269–272. 35. Boyd DH, Kinirons MJ, Gregg TA. A prospective study of factors affecting survival of replanted permanent incisors in children. Int J Paediatr Dent 2000;10:200–205. 36. Chappuis V, von Arx T. Replantation of 45 avulsed permanent teeth: A 1-year follow-up study. Dent Traumatol 2005;21:289–296. 37. Grossman LI. Intentional replantation of teeth. J Am Dent Assoc 1966;72:1111– 1118. 38. Andreasen JO. Atlas of Replantation and Transplantation of Teeth. Fribourg, Switzerland: Mediglobe SA, 1992.

39. Apfel H. Autoplasty of enucleated prefunctional third molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1950;8:289–296. 40. Apfel H. Preliminary work in transplanting the third molar to the first molar position. J Am Dent Assoc 1954;48:143–150. 41. Moorees CFA, Fanning FA, Hunt A. Age variation formation stages for 10 permanent teeth. J Dent Res 1963;42:1490–1502. 42. Mendes R, Rocha G. Mandibular third molar transplantation— Literature review with clinical cases. J Can Dent Assoc 2004; 70:761–766. 43. Baba NZ, Goodacre CJ, Daher T. Restoration of endodontically treated teeth: The seven keys to success. Gen Dent 2009;57:596–603. 44. Oikarinen K. Functional fixation for traumatically luxated teeth. Endod Dent Traumatol 1987;3:224–228. 45. Andreasen JO, Malmgren M, Bakland LK. Tooth avulsion in children: To replant or not. Endod Top 2006;14:28–34. 46. Andreasen JO, Andreasen FM, Andersson L. Textbook and Color Atlas of Traumatic Injuries to the Teeth, ed 4. Oxford, England: Blackwell, 2007. 47. Andreasen JO, Bakland LK, Flores MT, Andreasen FM, Andersson L. Traumatic Dental Injuries: A Manual, ed 3. Oxford, England: Wiley-Blackwell, 2011. 48. Chong BS, Pitt Ford TR, Hudson MB. A prospective clinical study of mineral trioxide aggregate and IRM when used as root-end filling materials in endodontic surgery. Int Endod J 2003;36:520–526.

Osseointegrated Dental Implants Age and trauma seem to be directly correlated to the incidence of tooth loss.1 The increase in life expectancy in developed countries has dramatically augmented the demand for tooth replacement therapies. The most prevalent causes for the absence of teeth appear to be caries, anodontia, and trauma. In 1991, approximately 70% of the US population was missing at least one tooth, an objective reflection of society increasing demands for tooth replacement therapies.2 The replacement of a failing single tooth has become one of the most challenging and controversial treatments in modern dentistry. If a tooth is severely compromised and is expected to have a poor prognosis even with the aid of endodontic treatment, crown lengthening, and/or root extrusion, tooth extraction may be the most biologically favorable management option. Traditionally, single-tooth replacement has involved two different prosthetic modalities: a removable or a fixed dental prosthesis. In the last few decades, these two approaches have been presented as the gold standard for the treatment of either a single tooth or multiple missing teeth. In 1990, more than 4 million fixed dental prostheses were placed in the United States.3 Fixed dental prostheses have been associated with complications and limitations. The most important disadvantage of a fixed dental prosthesis is that sound adjacent teeth have to be prepared to create enough space to accommodate the restorative materials. Compared with conventional prosthodontics, osseointegrated dental implants preserve teeth adjacent to the edentulous space and provide the patient with a minimally invasive treatment. In a review of the literature, Goodacre et al4 found that

the success rate for single-tooth implants is about 97%; other studies report rates ranging from 94% to 100% after follow-up periods of up to 15 years.5–8 In comparison, failure rates for fixed partial dentures may reach values that are higher than 20% at 10 years. Single-tooth replacement by means of a dental implant has several advantages over alternative treatments: improved esthetics, decreased risk of caries in adjacent teeth, elimination of the need for endodontic treatment in adjacent teeth, less risk of abutment loss, and improved maintenance of bone in the edentulous site.9 Thus, dental implant therapy should be considered as a treatment modality to replace severely compromised single teeth that cannot be treated predictably with conventional modalities.

Postextraction Physiology and Ridge Preservation Postextraction events Tooth extraction is usually followed by modeling and remodeling of the residual alveolar ridge. Approximately 0.34 to 7.70 mm of horizontal ridge resorption takes place during the initial 3 months,10 while 0.20 to 3.25 mm of vertical ridge resorption occurs in the initial 6- to 12-month period following extraction. The healing process following tooth removal apparently results in more pronounced resorption on the buccal than on the lingual or palatal aspect of the ridge.11, 12 Using stone casts, Pietrokovski and Massler13 studied the amount of tissue that was lost after unilateral tooth extraction. They concluded that the buccal bone plates in both the maxilla and the mandible were resorbed considerably more than the corresponding palatal or lingual bone walls. They also found that the center of the ridge was shifted palatally or lingually. Most of the buccal remodeling in the postextraction socket is related to the histologic characteristics of the buccal alveolar bone (bundle bone). This cortical bone has an average thickness of 0.8 mm and is highly associated with or dependent on the vascularization provided by the periodontal ligament, a feature that will be lost after exodontia.14, 15 Amler16 described the physiologic healing process that occurs in the extraction alveolus. He observed six different histologic stages leading to soft tissue healing and presence of mature bone 2 months postextraction (Fig 11-1).

Fig 11-1 Six histologic phases of healing in the alveolus following tooth extraction. RBC, red blood cell; WBC, white blood cell. (Adapted from Amler16 with permission.)

Postextraction resorption compromises the clinician’s ability to place an implant in an anatomically appropriate location to achieve a satisfactory esthetic outcome and long-term functional stability of the implant-supported restoration.17 In such a case, preservation of the alveolar ridge may be needed to optimize the esthetic and functional success of implant placement.

Ridge preservation Treatment aiming for the reduction of the physiologic changes related to alveolar healing has been generally referred to as ridge preservation. Particulate autografts,18, 19 allografts,20–25 alloplasts,26–30 and xenografts20, 30–36 in conjunction with barrier membranes, resorbable31, 32, 34–38 or nonresorbable,19, 21, 22, 39–42 have been used to minimize ridge resorption. Utilization of a ridge preservation technique that involves positioning of a membrane barrier to cover the socket and placement of a biomaterial or bone graft can partially preserve the horizontal and vertical dimensions.30, 36, 43 The question is whether the healing that takes place in the presence of these biomaterials really represents new bone. Histomorphometric analysis that allows the assessment of bone turnover and bone quality is the most common way to interpret and answer whether bone can be formed in the presence of biomaterials44 (Fig 11-2).

Fig 11-2 Histomorphometric analysis and histologic sections indicating bone formation in the presence of a xenograft. (a) Control group. No bone substitute material was utilized to preserve the alveolus. (b) Test group.

Section repre senting ridge preserved with xenograft. Note that buccal contour resorption is minimized. B, buccal bone wall; L, lingual bone wall; BM, bone marrow. (Reprinted from Araújo and Lindhe44 with permission.)

Whenever a socket is filled with any type of biomaterial, retention of nonvital bone graft particles may happen.37, 45 The amount and type of bone formed have been the main focus of histologic ridge preservation studies. This may vary depending on when the samples are harvested and the maturation of the harvested bone at that time point. Depending on the depth and morphology of the socket, the quality and quantity of bone formation may be different because the regeneration is initiated from the apical region,12, 15 which has been observed to have a significantly higher rate of new bone formation than the coronal region. Ridge preservation procedures may present different degrees of bone formation and residual bone graft particles in the socket. Results in the literature are not homogenous, and material selection may depend on the preference of the surgeon.46 One of the most important predictors of success may be the status of the periodontal and alveolar structures of the tooth to be replaced. A non-ideal architecture will result in poor esthetics related to the lack of proper gingival contours.47, 48 Therefore, the preservation of the alveolar structures and the recreation of these missing structures are of utmost importance.49

Scientific Validation for Single-Tooth Implant Replacement Osseointegration process The osseointegration concept was first described by Brånemark in 1969 and published by Albrektsson et al 50 in 1981. These researchers referred to the result of their technique as “a direct functional and structural connection between living bone and the surface of a load carrying implant.”50 In animal studies, Abrahamsson et al 51 and Berghlund et al52 explained the dynamics of implant integration in healed sites. They took biopsies starting 2 hours after insertion and sequentially up to 12 weeks after implant placement. They schematically divided the process into six different phases: 1. At 2 hours: The peripheral portions of the pitch are in contact with invaginations of the track prepared by the tap in cortical bone. The wound chambers are occupied with a blood clot and a network of fibrin. Leukocytes are apparently

engaged in the wound-cleansing process. 2. At 4 days: The coagulum starts to be replaced by granulation tissue, and new angiogenesis is observed. 3. At 1 week: Provisional connective tissue and mesenchymal cells are present. There is a decrease in inflammatory cells. Woven (immature) bone starts to appear in the mesenchymal tissues. 4. At 2 weeks: Woven bone formation increases, surrounding the implant. 5. At 4 weeks: Newly mineralized bone extends from the preparation site to the titanium surface of the implant. 6. At 6 to 12 weeks: The remodeling process begins, and the woven bone is replaced with mature bone.

Indications and contraindications Single-tooth implant treatments are often indicated for the replacement of a missing tooth and to partially reconstruct patients’ missing dentition, to improve the chewing capacity by replacing a lost tooth in posterior or anterior areas of the mouth, and to enhance esthetics. A thorough examination of the patient’s dental history for the history of tooth loss, caries risk assessment, food impaction, and susceptibility to periodontal disease can determine the risk and future outcomes for single implant placement. The medical history and expectations of the patient should also be taken into consideration whenever a dental implant is considered as a treatment option. The assessment is not complete without the patient’s medical history. The impact of some systemic conditions on treatment can determine success or failure. Many conditions have been widely described in the literature as possible healing modifiers. Situations such as uncontrolled diabetes,53–57 heavy smoking history,55, 58, 59 chemotherapy and radiation therapy in cancer patients,60–62 bisphosphonate therapy in osteoporosis patients,63–66 heavy alcohol consumption,67 and bleeding disorders68 can jeopardize treatment outcomes and put the patient’s life at risk. Most of these situations can be categorized as relative contraindications to implant placement. Communication with the patient’s physician should always be considered because alternative therapies are often available. The patient’s desires and expectations should be clearly understood. Some preexisting site problems (local problems) may prevent the surgeon from satisfying the patient’s expectations. An esthetic outcome assessment in the anterior sextant of the mouth should be made and explained to the patient. Local factors such as insufficient bone quantity and poor bone quality have to be

considered. Surgical procedures such as bone augmentation, bone regeneration, and/or bone compaction make the above-mentioned factors a relative contraindication for implant placement. In the scenario of a single failing tooth, two main implant placement approaches can be utilized: a delayed approach (extraction and implant placement are not part of the same surgical exercise) or an immediate approach (extraction and implant placement are performed simultaneously).

Single-Implant Placement in Healed Sites (Delayed Approach) Surgical protocols and armamentarium The healing of dental implants in the jawbone is based on the principle of osseointegration,69–73 the establishment of a direct bone-to-implant contact that had to be proved by means of histologic analysis. The original Brånemark implant protocol called for a stress-free submerged healing time of 3 to 6 months to ensure osseointegration.74 It was thought that the prolonged undisturbed healing time was necessary to avoid the development of fibrous tissue encapsulation around the implants instead of osseointegration50, 75, 76; however, later clinical and experimental evidence revealed that implants could osseointegrate even when left exposed to the oral cavity during healing.77–82 Traditionally, during this healing period patients were asked to wear a removable prosthesis; however, provisional prostheses are often uncomfortable because of a lack of stability and retention. Therefore, it was thought that it would be beneficial if the healing period could be shortened without jeopardizing implant success. With the high clinical success rates obtained with the original implant protocol, clinicians and researchers have now focused on further development and refinement of implant therapy with new implant designs and treatment concepts.83–85 Broadly, three different protocols for placing single dental implants in healed sites have been suggested: a submerged technique, a nonsubmerged technique, and an immediate provisionalization technique.

Submerged technique (two-stage approach)50, 69–86 A mucoperiosteal flap is elevated to allow placement of the implant, and a low-

profile cover screw is placed on the implant. Primary closure is obtained during the surgical exercise. During the healing period, there is no contact between the oral fluids and the implant site; therefore, the healing is not disturbed and is less dependent on the patient’s habits, both functional and hygienic, which can potentially induce an undesirable environment for implant integration. The implant does not receive loads during the healing time. After a healing period that may vary from 2 to 6 months, an additional surgical procedure is required. The implant site is reentered for prosthetic reconstruction. A secondstage surgery is performed to expose the implant and connect a healing abutment to it. The healing abutment will help the development of an initial emergence profile and create a soft tissue seal around the implant-abutment interface (Fig 11-3).

Fig 11-3 Two-stage implant placement in a healed site (submerged technique). (a) A surgical template is used to prepare the recipient site. (b) The implant is positioned in the prepared site, and a cover screw is secured in place. (c) The surgical site is sutured.

Nonsubmerged technique (one-stage approach)77–82 A higher-profile stock healing abutment or a chairsidemodified abutment (custom healing abutment) is connected to the implant during the implant placement surgery and left exposed to the oral cavity during healing. The healing abutment usually extends above the soft tissues to allow healing around the abutment and to prevent soft tissues from migrating over it and covering the implant platform. Because of the greater height of the abutment, the implant is more susceptible to receiving loads during healing time. Primary stability is important to achieve after implant placement because mastication may exert involuntary, slight lateral and oblique occlusal forces on the abutment. However, the healing abutment should not have occlusal contacts from the opposing teeth. This approach does not require an additional secondstage surgery. The literature has demonstrated that there is no difference in marginal bone loss when the onestage and two-stage protocols are compared87 (Fig 11-4).

Fig 11-4 One-stage implant placement in a healed site (nonsubmerged technique). (a) A surgical template is used to position an implant in the mandibular left area. (b) The interim abutment is secured in place. (c) The surgical site is sutured around the interim abutment.

Immediate provisionalization88 and immediate loading A provisional restoration is delivered immediately after the placement of the dental implant. The provisional restoration is left out of occlusion to avoid possible interferences during the healing period. However, forces from the perioral musculature as well as the load exerted by the tongue can affect implant healing. Therefore, a higher primary stability is required during implant insertion. An insertion torque of 30 to 35 Ncm has been recommended89 as the minimum necessary to obtain a predictable outcome; however, that value is dependent on the implant system used because some manufacturers recommend a lower insertion torque for their implants. The main advantages of this technique are the reduction in treatment time, the elimination of second-stage surgery to uncover the implant, and the increase in patient satisfaction.90 Recent studies90–95 on immediate loading for single-tooth replacement recognized the importance of the type of loading, whether functional or nonfunctional. While some authors96–98 reported lower success rates with full functional loading, others achieved high success rates when the prosthesis was in full-functional controlled loading in immediately loaded single-tooth implants.92, 93, 99 The role of immediate functional occlusion in clinical situations is yet to be determined conclusively.100 Immediate implant restorations with controlled loading provide better patient comfort, offer good esthetics,90 and eliminate the inconvenience of a second surgery for the placement of healing abutments. This often leads to early soft tissue healing and results in early stabilization of the peri-implant mucosa,101 thereby ensuring a higher rate of implant survival.90 Several experimental studies have shown that proper and controlled immediate loading of implants does not necessarily lead to fibrous tissue healing102–104; instead, the bone-to-implant contact develops over time and is comparable to that of implants that are loaded conventionally, 105–108 provided

that the functional loading is within the physiologic limits (Fig 11-5).

Fig 11-5 Immediate provisionalization in an anterior healed site. (a) Preoperative view. (b) Provisional restorations at the time of surgery. (c) Provisional restorations 2 weeks postsurgery at suture removal. (d) Soft tissue adaptation and maturation around the provisional restorations. (e) Definitive restorations 3 years after delivery. Note the stable and pleasing esthetics.

As a rule, the delayed healing approach is the most predictable for osseointegration. It depends less on patient cooperation with respect to diet, maintenance, and parafunctional habits. Therefore, if the patient is able to wear a removable restoration and is not concerned about the delayed treatment approach, it is prudent to use the longestablished protocols of delayed loading. However, these two options (submerged and nonsubmerged) delay the fabrication of the definitive restoration by 3 to 6 months.

Immediate Implant Placement Scientific validation for immediate implant placement Immediate implant placement is defined as the placement of a dental implant in an extraction socket at the time of extraction. It was first described in 1976 by Schulte and Heimke109 as a technique that could presumably shorten the treatment time, reduce the surgical interventions, and preserve the alveolar architecture. Several studies110, 111 have since evaluated the performance of this technique and observed results comparable to those achieved by implants placed in healed sites.

Apart from reducing the treatment period and the number of surgeries,112 other advantages of immediate implant placement in the extraction socket have been suggested. Better implant survival rates, better esthetics, maintenance of the hard and soft tissues at the extraction site,113, 114 and higher patient satisfaction compared with delayed implant placement have been cited.90 On the other hand, because of the nature of this treatment method, a higher risk of complications and failures may be expected.115 A recent controversy has been raised as to whether or not immediate placement can really preserve the gingival architecture.115 In a histologic study in beagle dogs, Araújo et al116 observed that, despite the placement of the implant at the time of extraction, the alveolar buccal plate remodeled, leaving the buccal aspect of the dental implant in contact with the facial soft tissue. The loss of the alveolar buccal bone can potentially create future esthetic problems. This observation has been validated in animal14, 117 and in human studies,11, 118–120 which have observed a higher tendency to facial gingival recession around implants placed immediately in areas with thin buccal plates (Fig 11-6).

Fig 11-6 (a and b) Postrestorative recession of the labial gingiva at an implant site.

More recent studies121, 122 have challenged these previous observations by showing that when the gap between the outer contour of the dental implant and the inner aspect of the buccal plate is grafted, and the implant diameter selection is appropriate, the preservation of the alveolar architecture can be predictably achieved.

Indications and contraindications

Assessment of extraoral parameters such as smile line and intraoral parameters such as gingival levels is fundamental to implant treatment.123, 124 Like several other authors, Kois124 has proposed diagnostic factors that are utilized to replace failing or missing teeth in the esthetic zone: Tooth position relative to the free gingival margin Form of the periodontium Biotype of the periodontium Tooth shape Position of the osseous crest before tooth extraction When immediate implant placement is being considered, a careful analysis of these factors is critical for determining if the patient has the right diagnostic determinants to allow for a predictable treatment. Immediate implant placement generally is considered challenging because of unpredictable hard and soft tissue healing.11, 118–120 Careful case selection is necessary to avoid treatment failures and esthetic complications. Hence, discussion of the risks, benefits, and limitations of immediate implant placement with patients is important to avoid any future disagreement. Funato et al125 developed a classification for the suitability of immediate placement based on the status of the buccal plate and the surrounding soft tissue characteristics. This classification provided guidelines for immediate implant placement and the timing between extraction and implant placement: A class 1 site has intact buccal bone with a thick gingival biotype and is expected to have optimal results with immediate implant placement without flap reflection. A class 2 site has intact buccal bone with a thin gingival biotype and is expected to have good results with immediate implant placement in conjunction with a connective tissue graft procedure. A class 3 site has deficient buccal bone within the alveolar housing and is expected to have limited but acceptable results with immediate implant placement in conjunction with guided bone regeneration plus connective tissue graft procedures. A class 4 site has deficient buccal bone deviating from the alveolar housing and is not indicated for immediate implant placement; a delayed approach is recommended. It is imperative that the clinician understand the hard and soft tissues surrounding the surgical area in order to appropriately select cases for which immediate implant placement would be successful.

Surgical protocols In general, the protocols for the implant placement and the restorative timings are the same for immediate implants as they are for implants placed in healed sites. However, immediate provisionalization without occlusal loading in the esthetic zone appears to increase in clinical relevance because the immediate interproximal tissue support provided by the provisional restoration may help to prevent the papilla from collapsing after tooth extraction90, 120 (Fig 11-7). The collapse of the papilla is one of the most common anterior esthetic problems in implant dentistry. It causes the appearance of “black triangles” because of the inadequate gingival architecture in the proximal areas.126, 127

Fig 11-7 (a) Hopeless maxillary left canine with a vertical root fracture. (b) Extraction of the tooth, preserving the intact bony walls of the socket. (c) Provisional abutment fixed to the implant. (d) Provisional crown in place the day of implant placement. (e) Definitive restoration in place several months following osseointegration.

Factors affecting success of immediate implant placement Several factors have been observed to impact the outcomes when immediate implant placement is performed. Tooth position The relative position in the arch of the tooth to be replaced determines the feasibility of the immediate implant placement technique. Individual variables such as root

length, root position, and the status of the architecture of the alveolar housing also have a critical role in the outcomes of this technique. A minimum implant apical extension of 4 to 5 mm beyond the tooth apex has been recommended to achieve primary stability. 90 In certain scenarios (eg, the replacement of a maxillary canine), the length of the root may preclude the stabilization of the implant. In such a case, an alternative technique may be utilized. Implant tridimensional position Several studies have analyzed the impact of the tridimensional position of the dental implant in relation to the preservation of the dentogingival structures. Both the facial and the interproximal aspects of the peri-implant mucosa have been observed to be affected by the position of the dental implant.118 A 1.5- to 2.0-mm mesiodistal distance from the implant to the adjacent tooth has been recommended to avoid impairing the normal physiology of the adjacent natural tooth.128 In a retrospective study, Esposito et al 128 observed radiographically that, whenever the distance between the dental implant and the adjacent tooth exceeded 1.8 mm, there was no bone loss on the proximal tooth surfaces (Fig 11-8).

Fig 11-8 Proper mesiodistal positioning of an implant. (a) Less than 1.5 mm will lead to bone loss on the adjacent tooth surface. (b) Optimal mediodistal position with a minimum of 1.5 mm allowed.

In the buccolingual dimension, the implant position has a direct relationship to the behavior of the buccal gingiva of the anterior tooth to be replaced. Chen et al118 observed that recession of the buccal gingiva appeared more frequently when the

implant position was buccal to the line connecting the incisal edges of the immediate adjacent teeth than when the implant was located palatal to that line. Recent reports have observed that a palatal positioning of the anterior implant that allows a minimum of 2 mm from the external diameter of the implant to the outer aspect of the buccal plate may be needed to prevent vertical bone loss and minimize esthetic complications resulting from buccal bone modeling after extraction that could result in subsequent soft tissue defects and gingival asymmetries121–130 (Fig 11-9).

Fig 11-9 Proper buccolingual positioning of an implant. (a) Incorrect position. (b) Insufficient labial bone. (c) Optimal bone level postion. Implant position is always determined by the tooth position, not the bone.

In the coronoapical aspect, a distance of 3 mm from the margin of the predetermined restoration to the facial aspect of the implant has been proposed. It has been repeatedly observed that the biologic width of the peri-implant mucosa in a healthy situation is within this range123 (Fig 11-10).

Fig 11-10 Proper coronoapical positioning of an implant.

A distance of 5 mm from the alveolar crest to the future prosthesis contact point can ensure the appearance of dental implant papillae131 (Fig 11-11).

Fig 11-11 Correct distance between the mesial and distal contact points on the definitive implant restoration to the crest of the ridge.

Primary stability The stability of the implant during placement has been observed to be directly correlated to the success of the implant over time.132 The stabilization landmarks will markedly vary depending on the position of the tooth that needs to be replaced.

Maxillary posterior area. The primary area of stabilization is usually located along the long axis of the tooth and apical to the septa of the extraction socket. Usually, because of the presence of the maxillary sinus, the available bone is very limited and precludes the stabilization of the dental implant, especially if the pneumatization is severe. Maxillary anterior area. In the anterior dentition, this situation is even more challenging because of the necessity to engage the palatal aspect of the socket to obtain stability. In a recent study conducted at Loma Linda University, researchers observed that the root of anterior maxillary teeth tends to be buccally positioned in about 81% of cases.133 Mandibular posterior area. In this region, the stabilization of the implant is highly dependent on the frontal section of the mandible (to avoid a possible perforation of the lingual cortical plate, which could lead to a life-threatening hemorrhage of the floor of the mouth) and the relative position of the inferior alveolar nerve. A safety distance of 2 mm coronal to the inferior alveolar nerve has been recommended to avoid possible neurosensory disturbances.134 Mandibular anterior area. The anatomical variability of the symphyseal area appears to be high. In this area, the authors recommend that the implant position be evaluated on an individual basis. Gap between the implant and surrounding alveolar walls Because of the discrepancy between the diameters of the dental implant and the extracted root, there is frequently a gap between the outer contour of the dental implant and the inner walls of the extraction socket. This gap is usually widest at the coronal aspect of the socket (Fig 11-12).

Fig 11-12 A gap is present between the implant and the surrounding inner walls of the extraction socket.

Schulte and Heimke109 emphasized that the entire cross section of the socket in the cervical region must be occupied by the implant. Other studies14, 116, 117 observed that the placement of implants in contact with the inner aspect of the buccal plate failed to preserve the architecture of the socket. It was hypothesized that the extraction of the tooth could lead to the loss of the most coronal aspect of the buccal plate, the bundle bone, which is a poorly vascularized bone that receives its supply mostly from the periodontal ligament, a feature that will be lost after the extraction of the tooth. A paradigm shift has been recently observed in the dental implant literature. A study published in 2011 showed that the selection of a narrower-diameter implant in conjunction with the addition of a xenogeneic bovine bone graft material would compensate for the loss of the bundle bone and preserve the gingival harmony.121 The authors believe that a narrower implant should be used to allow a minimum 2-mm buccal gap and thereby predictably preserve the buccal architecture. Various techniques and materials have been used to encourage bone growth within tooth sockets at the time of implant placement, including barrier membranes,135–137 autogenous bone grafts,138 demineralized or mineralized freezedried bone allografts,139–141 hydroxyapatite,142, 143 and xenografts.101, 120, 144, 145 Presence of dehiscences and/or fenestrations Extraction sockets may be accompanied by defects in the structure of the adjacent bony envelope (Fig 11-13). One of the most important prerequisites for an esthetically successful implant is the presence of an intact or minimally damaged postextraction alveolus.146 There is a lack of solid evidence analyzing the effects of

bone dehiscences in fresh extraction sockets; however, some reports suggest that the immediate placement of implants in sites with bony dehiscences may lead to future mucosal recessions147; in those scenarios, delaying the placement of the dental implant may render better esthetic outcomes.11, 14, 101, 115–148

Fig 11-13 (a and b) Extraction defects that may lead to unpredictable esthetic results and may require a separate regeneration procedure and delayed implant placement.

Presence of periapical pathosis Pulpal pathosis and failed endodontic treatment is one of the most common reasons for tooth extraction. It is very common to encounter periapical lesions at the time of implant placement. These lesions occupy areas that are usually predetermined to be part of the implant osteotomy. The implant literature regarding placement of implants in infected sockets is still inconclusive. Earlier studies149 on that matter showed lower success rates when implants were placed in infected sockets. However, more recent literature 150–154 indicates that effective debridement in addition to pharmacologic means, such as systemic amoxicillin152, 155 or clindamycin151 and local control (eg, tetracycline150), may render success rates comparable to implants placed in pathosis-free sites. In the event that symptomatic infection (acute infection) is found to be present at the time of implant surgery, the procedure may be postponed and the infection pharmacologically treated by means of a broad-spectrum antibiotic (Fig 11-14). The authors believe that the intrinsic nature of the infection may be the deciding factor to determine whether implants can be placed immediately after extraction when pathosis is present. A chronic infection may render a better prognosis than an acute one; therefore, the authors recommend that the nature of the infection be systematically evaluated prior to dental implant placement.

Fig 11-14 (a) Infected site prior to local and systemic treatment with antibiotics. (b) Site following local and systemic antibiotic treatment. The active infection has subsided temporarily, and no purulent exudate is noted.

Complications Several complications are associated with implant procedures; these can be multiple and categorized according to different causes: surgical, prosthetic, or both. Surgical complications are usually related to the surgical protocol. In a literature review, Goodacre et al156 found that hemorrhage, neurosensory problems, and mandibular fracture are the most common complications. Hemorrhage accounts for 24% of implant placement complications. It is often associated with blood vessel dissection during soft tissue manipulation, osteotomy, or lateral window preparation for sinus elevation procedures. Knowledge of local anatomy and its variations, as well as a radiologic assessment of the area, is mandatory. Management of hemorrhagic complications in these areas of the mouth consists of compression, application of vasoconstrictive agents, cauterization, utilization of bone wax, and ligation of arteries in extreme cases.157 Nerve injury, especially in the mandible, accounts for 7% of implant placement complications. It is worth mentioning once again the importance of the pretreatment evaluations and the identification of anatomical landmarks in the mandible, such as the inferior alveolar nerve and the mental foramen. Neurosensory disturbances are commonly associated with an erroneous flap design that may include some branches of the nerve in the incision, trauma during flap elevation, intranerve anesthesia, perforation of the nerve during implant site preparation, and compression of the nerve by the implant.158 Worthington159 suggested the concept of a safety zone encompassing the 2-mm distance the surgeon should allow as free space from the apex of the drill to the inferior alveolar nerve. Periapical radiographs should be taken during the drilling sequence to confirm this safety distance.

Injuries inflicted on the nerves can be transitory or permanent. Transitory injuries vary in healing time (from days to months). Permanent injuries are often the result of direct dissection or direct trauma to the nerve fibers and may be diagnosed with the aid of imaging modalities and clinical findings. Therapy in case of neurosensory disturbances consists of steroidal and nonsteroidal anti-inflammatory drugs and vitamins B2 and B12.160 Neurosurgical procedures to repair nerve injury can also be considered. Although mandibular fractures are reported as the most frequent type of fracture involving the face, fractures caused by implant placement are very rare (0.3%).161 Impacts from bone expansion, excessive pressure during improper implant placement, osteomalacia, and osteoporosis have been associated with reports of mandibular fractures. Management of fractures consists of reduction whenever needed and the use of screws and miniplates to stabilize the fracture.162 Another complication is placement of the implant in an improper position or angulation, which may lead to prosthetic complications, the devitalization of adjacent teeth, sinus membrane perforation, and lack of stability at the time of implant placement.

Summary The replacement of a failing or missing tooth appears to be a predictable therapy that can overcome most of the complications associated with classic alternatives. Several parameters need to be evaluated in order to obtain an accurate diagnosis that will lead to a properly designed treatment plan. Multiple approaches and techniques are available, and the adequate selection of these will determine the outcomes of the implant restoration.

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86. Astrand P, Ahlqvist J, Gunne J, Nilson H. Implant treatment of patients with edentulous jaws: A 20-year follow-up. Clin Implant Dent Relat Res 2008;10:207–217. 87. Cecchinato D, Olsson C, Lindhe J. Submerged or non-submerged healing of endosseous implants to be used in the rehabilitation of partially dentate patients. J Clin Periodontol 2004;31:299–308. 88. Wohrle PS. Single-tooth replacement in the aesthetic zone with immediate provisionalization: Fourteen consecutive case reports. Pract Proced Aesthet Dent 1998;10:1107–1114. 89. Ottoni JM, Oliveira ZF, Mansini R, Cabral AM. Correlation between placement torque and survival of single-tooth implants. Int J Oral Maxillofac Implants 2005;20:769–776. 90. Kan JYK, Rungcharassaeng K, Lozada JL. Immediate placement and provisionalization of maxillary single anterior implants: 1-year prospective study. Int J Oral and Maxillofac Implants 2003;18:31–39. 91. Ericsson I, Nilson H, Lindh T, Nilner K, Randow K. Immediate functional loading of Brånemark single tooth implants. An 18 months’ clinical pilot follow-up study. Clin Oral Implants Res 2000;11:26–33. 92. Calandriello R, Tomatis M, Vallone R, Rangert B, Gottlow J. Immediate occlusal loading of single lower molars using Brånemark System WidePlatform TiUnite implants: An interim report of a prospective open-ended clinical multicenter study. Clin Implant Dent Relat Res 2003;5:74–80. 93. Cannizzaro G, Leone M. Restoration of partially edentulous patients using dental implants with a microtextured surface: A prospective comparison of delayed and immediate full occlusal loading. Int J Oral Maxillofac Implants 2003;18:512–522. 94. Glauser R, Lundgren AK, Gottlow J, et al. Immediate occlusal loading of Brånemark TiUnite implants placed predominantly in soft bone: 1-year results of a prospective clinical study. Clin Implant Dent Relat Res 2003;5:47–56. 95. Abboud M, Koeck B, Stark H, Wahl G, Paillon R. Immediate loading of singletooth implants in the posterior region. Int J Oral Maxillofac Implants 2005;20:61–68. 96. Chaushu G, Chaushu S, Tzohar A, Dayan D. Immediate loading of single-tooth implants: Immediate versus non-immediate implantation. A clinical report. Int J Oral Maxillofac Implants 2001;16:267–272. 97. Glauser R, Rée A, Lundgren A, Gottlow J, Hämmerle CH, Schärer P. Immediate occlusal loading of Brånemark implants applied in various jawbone regions: A prospective, 1-year clinical study. Clin Implant Dent Relat Res 2001;3:204–213.

98. Rocci A, Martignoni M, Gottlow J. Immediate loading of Brånemark System TiUnite and machined-surface. Clin Implant Dent Relat Res 2003;5:57–63. 99. Cornelini R, Cangini F, Covani U, Barone A, Buser D. Immediate restoration of single-tooth implants in mandibular molar sites: A 12-month preliminary report. Int J Oral Maxillofac Implants 2004;19:855–860. 100. Degidi M, Iezzi G, Perrotti V, Piattelli A. Comparative analysis of immediate functional loading and immediate nonfunctional loading to traditional healing periods: A 5-year follow-up of 550 dental implants. Clin Implant Dent Relat Res 2009;11:257–266. 101. Tsuda H, Rungcharassaeng K, Kan JY, Roe P, Lozada JL, Zimmerman G. Periimplant tissue response following connective tissue and bone grafting in conjunction with immediate single-tooth replacement in the esthetic zone: A case series. Int J Oral Maxillofac Implants 2011;26:427–436. 102. Piattelli A, Corigliano M, Scarano A, Costigliola G, Paolantonio M. Immediate loading of titanium plasma-sprayed implants: An histologic analysis in monkeys. J Periodontol 1998;69:321–327. 103. Romanos GE, Toh CG, Siar CH, Swaminathan D. Histologic and histomorphometric evaluation of peri-implant bone subjected to immediate loading: An experimental study with Macaca fascicularis. Int J Oral Maxillofac Implants 2002;17:44–51. 104. Nkenke E, Lehner B, Weinzierl K, et al. Bone contact, growth, and density around immediately loaded implants in the mandible of mini pigs. Clin Oral Implants Res 2003;14:312–321. 105. Ghanavati F, Shayegh SS, Rahimi H, et al. The effects of loading time on osseointegration and new bone formation around dental implants: A histologic and histomorphometric study in dogs. J Periodontol 2006;77:1701–1707. 106. Bousdras VA, Walboomers F, Jansen JA, et al. Immediate functional loading of single-tooth TiO2 grit-blasted implant restoration. A controlled prospective study in a porcine model. 2. Histology and histomorphometry. Clin Implant Dent Relat Res 2007;9:207–216. 107. Traini T, Neugebauer J, Thams U, Zöller JE, Caputi S, Piattelli A. Peri-implant bone organization under immediate loading conditions: Collagen fiber orientation and mineral density analyses in the minipig model. Clin Implant Dent Relat Res 2009;11:41–51. 108. Meyer U, Wiesmann HP, Fillies T, Joos U. Early tissue reaction at the interface of immediately loaded dental implants. Int J Oral Maxillofac Implants 2003;18:489–499. 109. Schulte W, Heimke G. The Tübingen immediate implant [in German]. Quintessenz 1976;27(6):17–23.

110. Malchiodi L, Ghensi P, Cucchi A, Corrocher G. A comparative retrospective study of immediately loaded implants in postextraction sites versus healed sites: Results after 6 to 7 years in the maxilla. Int J Oral Maxillofac Implants 2011;26:373–384. 111. Cooper LF, Raes F, Reside GJ, et al. Comparison of radiographic and clinical outcomes following immediate provisionalization of single-tooth dental implants placed in healed alveolar ridges and extraction sockets. Int J Oral Maxillofac Implants 2010; 25:1222–1223. 112. Esposito M, Grusovin MG, Polyzos IP, Felice P, Worthington HV. Timing of implant placement after tooth extraction: Immediate, immediate-delayed or delayed implants: A Cochrane systematic review. Eur J Oral Implantol 2010;3:189–205. 113. Werbitt MJ, Goldberg PV. The immediate implant: Bone preservation and bone regeneration. Int J Periodontics Restorative Dent 1992;3:206–217. 114. Paolantonio M, Dolci M, Scarano A, et al. Immediate implantation in fresh extraction sockets. A controlled clinical and histological study in man. J Periodontol 2001;11:1560–1571. 115. Chen ST, Buser D. Clinical and esthetic outcomes of implants placed in postextraction sites. Int J Oral Maxillofac Implants 2009;24:186–217. 116. Araújo MG, Sukekava F, Wennström JL, Lindhe J. Ridge alterations following implant placement in fresh extraction sockets: An experimental study in the dog. J Clin Periodontol 2005;32:645–652. 117. Botticelli D, Persson LG, Lindhe J, Berglundh T. Bone tissue formation to implants placed in fresh extraction sockets: An experimental study in dogs. Clin Oral Implants Res 2006;17:351–358. 118. Chen ST, Darby IB, Reynolds EC. A prospective clinical study of nonsubmerged immediate implants: Clinical outcomes and esthetic results. Clin Oral Implants Res 2007;18:552–562. 119. Sanz M, Cecchinato D, Ferrus J, Pjetursson EB, Lang NP, Lindhe J. A prospective, randomized-controlled clinical trial to evaluate bone preservation using implants with different geometry placed into extraction sockets in the maxilla. Clin Oral Implants Res 2010;21:13–21. 120. Kan JY, Rungcharassaeng K, Lozada JL, Zimmerman G. Facial gingival tissue stability following immediate placement and provisionalization of maxillary anterior single implants: A 2- to 8-year follow-up. Int J Oral Maxillofac Implants 2011;26:179–187. 121. Araújo MG, Linder E, Lindhe J. Bio-Oss Collagen in the buccal gap at immediate implants: A 6-month study in the dog. Clin Oral Implants Res 2011;22:1–8.

122. Roe P, Kan JY, Rungcharassaeng K, Caruso JM, Zimmerman G, Mesquida J. Horizontal and vertical dimensional changes of peri-implant facial bone following immediate placement and provisionalization of maxillary anterior single implants: A 1-year cone beam computed tomography study. Int J Oral Maxillofac Implants 2012:27:393–400. 123. Kan JY, Rungcharassaeng K, Umezu K, Kois JC. Dimensions of peri-implant mucosa: An evaluation of maxillary anterior single implants in humans. J Periodontol 2003;74:557–562. 124. Kois JC. Predictable single-tooth peri-implant esthetics: Five diagnostic keys. Compend Contin Educ Dent 2004;25:895–896. 125. Funato A, Salama MA, Ishikawa T, Garber DA, Salama H. Timing, positioning, and sequential staging in esthetic implant therapy: A four dimensional perspective. Int J Periodontics Restorative Dent 2007;27:313–323. 126. Chang M, Wennström JL, Odman P, Andersson B. Implant supported singletooth replacements compared to contralateral natural teeth. Crown and soft tissue dimensions. Clin Oral Implants Res 1999;10:185–194. 127. Gotfredsen K. A 5-year prospective study of single-tooth replacements supported by the Astra Tech implant: A pilot study. Clin Implant Dent Relat Res 2004;6:1–8. 128. Esposito M, Ekestubbe A, Grondahl K. Radiographic evaluation of marginal bone loss at tooth surfaces facing single Brånemark implants. Clin Oral Implant Res 1993;4:151–157. 129. Spray JR, Black CG, Morris HF, Ochi S. The influence of bone thickness on facial marginal bone response: Stage I placement through stage II uncovering. Ann Periodontol 2000;5:119–128. 130. Qahash M, Susin C, Polimeni G, Hall J, Wikesjö UM. Bone healing dynamics at buccal peri-implant sites. Clin Oral Implants Res 2008;19:166–172. 131. Choquet V, Hermans M, Adriaenssens P, Daelemans P, Tarnow DP, Malevez C. Clinical and radiographical evaluation of the papilla level adjacent to singletooth dental implants. A retrospective study in the maxillary anterior region. J Periodontol 2001;72;1364–1371. 132. Javed F, Romanos G. The role of primary stability for successful immediate loading of dental implants. J Dent 2010;38:612–620. 133. Kan JY, Roe P, Rungcharassaeng K, et al. Classification of sagittal root position in relation to the anterior maxillary osseous housing for immediate implant placement. A cone beam computed tomography study. Int J Oral Maxillofac Implants 2011; 26:873–876. 134. Misch CE, Crawford EA. Predictable mandibular nerve location— A clinical zone of safety. Dent Today 1990;9:32–35.

135. Brägger U, Hämmerle CH, Lang NP. Immediate transmucosal implants using the principle of guided tissue regeneration. 2. A cross-sectional study comparing the clinical outcome 1 year after immediate to standard implant placement. Clin Oral Implants Res 1996;7:268–276. 136. Lang NP, Brägger U, Hämmerle CH, Sutter F. Immediate transmucosal implants using the principle of guided tissue regeneration. 1. Rationale, clinical procedures and 30- month results. Clin Oral Implants Res 1994;5:154–163. 137. Augthun M, Yildirim M, Spiekermann H, Biesterfeld S. Healing of bone defects in combination with immediate implants using the membrane technique. Int J Oral Maxillofac Implants 1995; 10:421–428. 138. Becker W, Becker BE, Polizzi G, Bergström C. Autogenous bone grafting of bone defects adjacent to implants placed into immediate extraction sockets in patients: A prospective study. Int J Oral Maxillofac Implants 1994;9:389–396. 139. Gher ME, Quintero G, Assad D, Monaco E, Richardson AC. Bone grafting and guided bone regeneration for immediate dental implants in humans. J Periodontol 1994;65:881–891. 140. Shanaman RH. A retrospective study of 237 sites treated consecutively with guided tissue regeneration. Int J Periodontics Restorative Dent 1994;14:292– 301. 141. Gelb DA. Immediate implant surgery: Three-year retrospective evaluation of 50 consecutive cases. Int J Oral Maxillofac Implants 1993;8:388–399. 142. Watzek G, Haider R, Mensdorff-Pouilly N, Haas R. Immediate and delayed implantation for complete restoration of the jaw following extraction of all residual teeth: A retrospective study comparing different types of serial immediate implantation. Int J Oral Maxillofac Implants 1995;10:561–567. 143. Block MS, Kent JN. Placement of endosseous implants into tooth extraction sites. J Oral Maxillofac Surg 1991;49:1269–1276. 144. Chung S, Rungcharassaeng K, Kan JY, Roe P, Lozada JL. Immediate single tooth replacement with subepithelial connective tissue graft using platform switching implants: A case series. J Oral Implantol 2011;37:559–569. 145. Kan JY, Rungcharassaeng K, Morimoto T, Lozada J. Facial gingival tissue stability after connective tissue graft with single immediate tooth replacement in the esthetic zone: Consecutive case report. J Oral Maxillofac Surg 2009;67:40–48. 146. Kan JY, Rungcharassaeng K. Immediate placement and provisionalization of maxillary anterior single implant: A surgical and prosthodontics rationale. Pract Periodontics Aesthet Dent 2000; 12:817–824. 147. Belser UC, Grütter L, Vailati F, Bornstein MM, Weber HP, Buser D. Outcome evaluation of early placed maxillary anterior singletooth implants using

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Repair of Perforations in Endodontically Treated Teeth “It is as well not to be in too great a hurry to extract a root that has been perforated. It should be studied carefully, and if it can be saved the dentist has not only rendered his patient a great service, but he has the feeling of satisfaction and pride which comes from having overcome a serious obstacle and which more than repays him for his trouble.” —F. A. Peeso1

Perforations are iatrogenic or pathologic communications between the root canal system and the oral cavity or periodontium.2 Perforations can be caused by caries or resorptive defects; they can also be created accidentally during endodontic or restorative procedures.3–5 This chapter focuses primarily on iatrogenically generated perforations. These procedural mishaps are a common complication of root canal treatment during access, instrumentation, and debridement procedures or as a result of misguided post space preparation or core placement4–8 (Fig 12-1). Canal instrumentation procedures can induce perforations by stripping, transportation, or

violation of the apical foramen.

Fig 12-1 (a) Maxillary left second premolar with distal midroot perforation and failed gutta-percha repair. The tooth was subsequently extracted. (b) Mandibular right first molar with a stainless steel post perforating the mesial root and concomitant furcation bone loss. (c) Mandibular right second molar with an amalgam core buildup, a mesial root perforation, and substantial osseous pathosis. (d) Maxillary right first molar with a misdirected screw post perforating the floor of the maxillary sinus and present for 10 years. The patient was asymptomatic.

The incidence of iatrogenic root perforations resulting in failed endodontic treatment varies from 2% to 12%.6, 9–11 These procedural accidents are responsible for a large proportion of endodontic failures and are a significant factor in long-term successful treatment outcomes.6, 7, 9, 12 The majority of perforations are the direct result of procedural errors that occur during conventional root canal treatment.13–16 Maxillary teeth may have a three times greater incidence of perforation during treatment than mandibular teeth, the most common sites being the midroot areas of the mesial and buccal root surfaces.16 Untreated accidental perforations of the pulpal floor or root canals are detrimental to tooth retention; they lead to chronic inflammation, formation of granulation tissue, and loss of the attachment apparatus.7, 17–20 Although perforations do not inevitably result in tooth loss, exposure to oral microorganisms and repair with nonbiocompatible restorative materials result in persistent irritation at the injury site.10, 17 This can lead to a proliferation of granulation tissue, pocket formation, and bone resorption with eventual bone necrosis (Fig 12-2). If the

inflammation is persistent, and an osseous defect that communicates with the oral environment is formed, repair of the defect will be compromised, and heroic endodontic surgical procedures or tooth extraction may be indicated.

Fig 12-2 Maxillary left lateral incisor with post perforation apically on the buccal aspect of the root 1 year after treatment. The large osseous defect has resulted in peri-implantitis of the adjacent titanium fixture.

Diagnosis and Classification Diagnosis of perforations is dependent on radiographic, clinical, and observational factors. The most obvious indication that a perforation has occurred is sudden or uncontrolled bleeding that occurs within the pulp-canal perimeter during instrumentation of the root canal, creation of a post space, or preparation of the remaining coronal structure as a core. Pulpal floor perforations can be easily visualized under magnification and illumination, while perforations in curved canals can best be diagnosed with paper point exploration or with an electronic apex locator.21

Prognostic factors

Favorable treatment outcomes for iatrogenic root perforations depend on the ability of the material and technique to effectively eliminate the egress of oral microorganisms from the canal system into surrounding tissues.22, 23 Several factors impact the control of infection at the perforation site. These include the time between the perforation and its repair, its anatomical location, the size of the perforation, and the ability of the repair material to effectively provide a permanent seal.4, 7, 10, 11, 14 Time It has been conclusively demonstrated that the longer a perforation remains untreated, the greater the likelihood that infection will be established in the supporting tissues.7, 22 However, the prognosis for healing is generally favorable if the perforation is repaired immediately. 18 Investigations using dog and nonhuman primate models found that perforations sealed immediately showed favorable healing responses, whereas untreated or delayed repair resulted in progressive damage and tissue destruction.7, 24–26 The findings support the practice of immediate perforation repair and the advantages of precluding bacterial challenges. If the accidental perforation cannot be definitively treated when initially generated, then the placement of a provisional aseptic seal and prompt referral to a specialist is recommended.3, 22, 27 Location The location of the perforation on the root or crown surface is the most critical factor influencing prognosis. Perforations of the root are often categorized into three locations: the coronal or cervical third, the middle third, and the apical third.10 If the perforation occurs in close proximity to the epithelial attachment and the crestal bone, communication with the oral environment through the gingival sulcus can promote bacterial contamination and a subsequent inflammatory response.17, 24, 25, 28, 29 Furcation perforations and crestal perforations are at high risk for apical migration of the gingival epithelium if not repaired immediately. 7, 17, 22, 30 Furthermore, root perforations in the furcation area have a poorer prognosis than do those that occur more apically on the root surface.31 The critical aspects in the management of furcation perforations include prompt intervention, proper isolation, debridement, and delivery of a bacteria-tight seal at the defect site.32 Supracrestal perforations coronal to the attachment apparatus without supporting tissue involvement have an excellent overall prognosis when the access to the area is not challenging and the remaining tooth structure can be effectively restored.11 In some cases, crown lengthening procedures or orthodontic extrusion of the tooth may

be indicated to facilitate repair with conventional restorative materials.14, 33 Other treatment strategies may involve surgical extraction and intentional replantation of the tooth after extraoral repair of the defect or surgical extrusion. These procedures can make repairs at the coronal third more predictable. The preservation of the biologic width, which is crucial to the health of the periodontium, is the primary goal34–37 (Fig 12-3).

Fig 12-3 (a) Preoperative radiograph of symptomatic maxillary right second premolar with screw post perforating the distal aspect. A 7-mm periodontal pocket is present. (b) Tooth after post removal. (c) Perforation repair with mineral trioxide aggregate (MTA) after sodium hypochlorite hemostasis. Note the extrusion of the repair material. (d) Radiograph after root canal retreatment and placement of a bonded post and core. (e) One-month recall after placement of a new metal-ceramic crown, revealing increased pocket formation. Surgical removal of extruded MTA is to be initiated. (f) Recall radiograph 6 months after removal of the extruded repair material. The normal probing depth of 3 mm shows complete epithelial reattachment.

Apical perforations have a good treatment prognosis when sustained in a sterile environment.24 Root perforations that occur in the midradicular area or the apical third have a favorable prognosis if no communication is present with the oral cavity and the main canal is easily accessible. The most challenging perforations to repair are those at crestal bone level involving the epithelial attachment. These are assigned a questionable prognosis (Table 12-1). However, the selection of repair materials and the isolation and delivery of biocompatible materials that prevent coronal leakage and demonstrate superior sealing ability at the defect site can provide an advantage in the overall prognosis for the involved tooth.38–42

Size In general, the larger the perforation, the more challenging the treatment and the lower the likelihood of repair and tissue healing. It has been understood for decades that small perforations that typically occur during endodontic procedures under aseptic conditions have a favorable prognosis.15 File sizes ISO 10 to 20 produce pinpoint perforations that result in minor tissue damage, and therefore extrusion of materials is minimized during repair procedures. Larger perforations that may occur during canal access or prosthetic procedures produce the greatest trauma to the supporting tissues.11 Larger perforations create a greater surface area that may make it more challenging to seal the perforation and to maintain control of the sealing material.28 Experimentally created pulpal floor perforations in dogs have shown better healing responses in larger teeth with proportionally smaller perforations.43 Classification Factors affecting the prognosis and outcome of perforation repair are classified in order to assist in basic strategy decisions (Box 12-1).

Prevention An important aspect of preventing mechanical perforations includes a thorough knowledge of root canal morphology and its variations. Before treatment, the clinician should carefully assess the tooth alignment in relation to the maxilla or mandible and adjacent teeth, the radiographic depth and position of the pulp chamber, and the presence of calcifications. 11, 44, 45 Moreover, anatomical features such as canal curvature and direction, root width and length, canal diameter, dentin wall thickness, and the type and extent of previous restorations all require consideration before access and treatment are initiated. The following points serve as general guidelines for endodontic and prosthetic treatment (adapted from Tsesis and Fuss11): Use a dental operating microscope (DOM) and illumination to obtain the best visualization.46, 47 Delay dental dam placement until access is completed in teeth with: –Narrow and calcified pulp chambers48 –Complete-coverage restorations when root alignment is unclear Recognize that the pulp chamber is located centrally in the clinical crown at the

level of the cementoenamel junction.49 Use large, tapered nickel-titanium instruments with caution. Maintain conservative post space preparations with Peeso reamers, ParaPost drills (Coltène/Whaledent), or Gates Glidden drills by using the DOM.50–52 Care must be taken not to misdirect post space placement when endodontically treated teeth are restored (Fig 12-4). Deviation from the central canal during parallel post space preparations is a common problem, particularly in premolars.53, 54 A smaller-diameter post space can generally be safely placed in the palatal canals of maxillary molars, the distal canals of mandibular molars, and the longest and straightest canals of premolars.55, 56 Operators should exercise caution to avoid overheating the tooth during preparation,57, 58 to ensure that adequate obturation material remains apically, and to use the DOM with illumination to decrease the risk of perforation.59–61

Fig 12-4 (a) Maxillary left second premolar with two posts misplaced outside the main canal. (b) Mandibular right first molar with a misguided post in the furcation. (c) Maxillary right second premolar with a misaligned stainless steel post perforating the buccal aspect (arrow). Note the periradicular pathosis associated with failing endodontic treatment and possible post perforation of the first molar.

Perforation Repair Materials The selection of a suitable material for perforation repair is paramount to successful treatment outcomes, and the material should be carefully matched to the type of perforation. An ideal material should be biocompatible, nonabsorbable, nontoxic, dimensionally stable, able to provide a permanent seal against bacterial leakage, and should offer easy application and adequate radiopacity.11 A multitude of materials have been used historically; these include amalgam, Cavit (3M ESPE), zinc oxide cements, calcium hydroxide, gutta-percha, demineralized freezedried bone, tricalcium phosphate, hydroxyapatite, Intermediate Restorative Material (IRM, Dentsply), resin-modified glass-ionomer cements,

composite resins, and tricalcium silicate cements such as mineral trioxide aggregate (MTA; eg, ProRoot MTA, Dentsply Tulsa Dental).14, 30, 38, 62–66 The choice of material will be dictated mainly by the location of the perforation. Perforations above crestal bone level can be predictably repaired with permanent coronal restorative materials, which resist dissolution by oral fluids, mastication, or dentifrices. Properly isolated, supracrestal perforations repaired with amalgam, composite resins, resin-ionomers, or compomers all have a good prognosis. Crestal perforations have a questionable prognosis because of their proximity to the epithelial attachment. These present complex problems and may require surgical reflection for isolation of the defect. Nonabsorbable materials are recommended for these areas and include hybrid resinionomer cements, in particular, Geristore (DenMat).67–69 This material has been shown to promote epithelial attachment and repair of damaged tissues when placed in subgingival defects and cavities. The placement of the material is technique sensitive and requires the use of the DOM and illumination. Placement must be carried out in a sterile and isolated field. The greatest advance in the management of subcrestal perforations has come with the introduction of MTA. 39, 62–65, 70 MTA is a hydraulic tricalcium silicate material derived from Portland cement that contains bismuth oxide as a radiopacifier. The material is a hydrophilic powder and, when mixed with water, forms a colloidal gel that solidifies in 3 to 4 hours, exhibits an alkaline pH of 12.5, and sets in blood and serum.71, 72 The cement is antibacterial, has minor cytoxicity, is not mutagenic, shows exceptional sealing ability, and induces the formation of mineralized tissue73–81 (Fig 12-5).

Fig 12-5 (a) Mandibular left first molar of 42-year-old man with longstanding strip perforation and furcation defect. (b) Six-week recall after MTA perforation repair and bonded core buildup. (c) Ten-year recall after completion of conventional treatment of the symptomatic second molar.

The bioactive and physicochemical properties of MTA encourage osteoblast cell differentiation and resultant bone deposition, stimulate repair by cementum, and promote periodontal ligament re-formation.77, 82–88 MTA has been shown to perform

better as a perforation repair material than AH Plus (Dentsply), Vitremer (3M ESPE), IRM, Cavit, amalgam, composite resins, glass-ionomer cements, and guttapercha.82, 89–94 Studies of the use of MTA to repair apical perforations demonstrate remarkable healing rates in challenging cases because of its cementogenic and osteoinductive properties.62, 63, 76, 82, 95–100 Perforation repairs with MTA can be completed without the use of an internal matrix because the material, when extruded, will induce cementum repair and regeneration of the periodontal ligament (Fig 12-6). However, a modified matrix concept has shown excellent results in case studies.101 The material of choice for management of subcrestal perforations is MTA and other related tricalcium silicate cements.

Fig 12-6 (a) Mandibular right first molar in a 51-year-old woman with a post perforation at the distal midroot “danger zone.” The patient is symptomatic. (b) Radiograph after retreatment of both the first and second molars with apical and midroot obturation and repair of the distal root with gray MTA. (c) Complete remineralization of the perforation defect 6 years after retreatment. The second molar has a vertical root fracture and will be extracted.

Management of Perforations The treatment of perforations appears in the early dental literature, and its importance in tooth retention was recognized before the 19th century. 1, 102, 103 Peeso1 recommended anatomically based treatments for coronal, middle (crestal), and apical locations of teeth in 1903. The importance of avoiding overfills and the indications for root resection were also established. The management of the perforation defect must first be assessed through a complete clinical and radiographic examination, including determination of the defect’s size, location, and age. For teeth with longstanding perforations, treatment options should only be considered if there is clear evidence of pathosis.104, 105 Clinical strategy is dependent on factors such as the operator’s skill and the sealing properties of the materials selected.3, 6, 14, 25, 106 Treatment should be managed nonsurgically if at all possible, thus avoiding potential damage to adjacent

anatomical structures106 (Fig 12-7).

Fig 12-7 (a) Mandibular second premolar in a 62-year-old man 2.5 years after root canal therapy and midroot post perforation. (b) Midplate sinus tract. Periodontal probings reveal intact crestal bone. (c) File placement to identify the location and size of the perforation. (d) Appearance 2 weeks after MTA perforation repair, conventional gutta-percha retreatment, and bonded core buildup. The sinus tract has healed. (e) Radiograph 1 year posttreatment. (f) Eleven-year radiographic review. The patient is asymptomatic and the tooth firm and in full function.

Orthograde management of perforations An intracoronal approach to repair iatrogenic perforations, with the aid of the DOM, is the preferred method. The aim is to avoid bacterial contamination and control hemorrhage at the perforation site or to disinfect and repair the area if previously infected.11 The selection of sealing material is dependent on the type and location of the perforation. The presence of a communication between the perforation defect and the oral environment compromises the prognosis. Supracrestal perforations Mechanical exposures coronal to the cementoenamel junction not involving the epithelial attachment can generally be repaired nonsurgically, and choice of material may be determined by esthetics. Traditional materials such as amalgam, cast metal restorations (defect coronal to the restoration margin), and bonded composite restorations fulfill the requirements to provide coronal seal and prevent bacterial ingress. Isolation is critical, and in some cases surgical visualization of the defect

may require flap reflection, orthodontic extrusion, or intentional replantation.14, 34, 107– 110

Crestal perforations Iatrogenically induced perforations penetrating the crestal zone are particularly challenging to repair because of the proximity of the attachment apparatus and the vulnerability to epithelial migration and pocket formation. The prognosis for these wounds is questionable, and they are broadly classified into furcation perforations, strip perforations, exploratory perforations, and perforations related to external inflammatory cervical root resorption. These defects require a biocompatible sealing material in order to regenerate the periodontium.111 Some crestal perforations on single-rooted teeth can be managed by external repair after orthodontic extrusion.112 Large furcation perforations and strip perforations should be managed nonsurgically, but limiting and controlling the extrusion of the repair material are challenging. Internal matrix techniques may aid the placement of repair materials; these include resorbable collagen, calcium sulfate, hydroxyapatite, and demineralized freeze-dried bone.17, 30, 83, 113–116 However, large furcation defects can be treated successfully without using an internal matrix barrier when the repair is performed immediately, MTA is placed in the defect, and sodium hypochlorite (NaOCl) is used to achieve hemostasis.63, 117–124 Both gray MTA and white MTA perform well as repair materials in furcation perforations125–127 (Fig 12-8).

Fig 12-8 (a) Mandibular left first molar with a mesial root periapical radiolucency in a 13-year-old asymptomatic

girl. The molar exhibits both strip and apical perforations from previous root canal treatment. (b) Strip perforation visible under the DOM at the furcal side of the mesial root (arrow). (c) Working length determination after removal of previous obturation material. (d) White MTA canal obturation to the level of the pulpal floor. (e) Final radiograph of obturation and the fiber post and bonded core. (f) Radiograph at 7 years, showing the completecoverage restoration and complete periradicular healing. The patient is asymptomatic with the molar in full function. (Courtesy of Dr Marga Ree, Amsterdam.)

Subcrestal perforations Perforations in the midroot and apical area are the most predictable to treat and can be considered as extra openings originating from the main canal.3, 14, 50 These defects can be created during canal instrumentation, the exploration of calcified canals, post space preparation, bypass procedures to remove separated instruments, or resorptive processes. Current data support the effectiveness of perforation repair together with MTA canal obturation or MTA repair in combination with conventional obturation materials (Fig 12-9). This avoids the need for long-term disinfection with calcium hydroxide followed by placement of gutta-percha as a perforation repair and filling technique.5, 128–132 MTA can be placed with or without a matrix barrier; however, root-end resection may be indicated if the original canal is not accessible after the repair.11 Where apical surgery is not an option, advanced techniques can also provide dedicated channels for conventional obturation after MTA placement and hardening.

Fig 12-9 (a) Maxillary left second premolar in a symptomatic 24-year-old man with a suspected post perforation to the mesiobuccal root aspect. Note the well-circumscribed periradicular radiolucency adjacent to the perforation. (b) Completed access through the metal-ceramic crown. The coronal aspect of the post has been uncovered. (c)

Post following removal. (d) Chamber after debridement of the perforation site and preparation for MTA placement. (e) Immediate postoperative radiograph following MTA perforation repair and subsequent completion of nonsurgical endodontic retreatment. (f) Ten-month radiographic review showing complete resolution of the periradicular pathosis. The patient is asymptomatic. (Courtesy of Dr Ryan M. Jack, Colorado Springs, CO.)

Hemorrhage at the perforation site can be challenging when nonobservable subcrestal perforations are being prepared apically or beyond the view of the DOM. Once the perforation is identified, 1.25% to 6.0% NaOCl provides an environment that removes inflammatory tissue, controls hemorrhage, disinfects the perforation site, and conditions the surrounding dentin.133–137 However, the solution must not be propelled into perforation areas because this can often cause severe tissue damage and paresthesia.138–143 Sodium hypochlorite should always be delivered passively, using pipette carriers or cotton pellets, or placed in the pulp chamber and gently transported along the main canal using hand files, avoiding penetration at the wound site. The solution may also be delivered by inserting a small suction cannula into the canal beyond the perforation and then placing the liquid in the chamber to be passively drawn into the canal to beyond the defect. If the perforation does not include the main canal, then NaOCl is gently brought to the limit of the defect interface and frequently replenished until hemostasis is achieved.

Retrograde management of perforations The goal of surgical repair of root perforations is to provide a reliable seal so that bacteria and their by-products are prevented from entering the periodontium through the root canal system. This procedure should encourage an environment that promotes regeneration of the damaged periodontal tissues and maintains immune cell surveillance. The indications for surgical treatment include excessive extrusion of the repair material, combination (orthograde and retrograde) therapies, perforations inaccessible by nonsurgical means, and failure of nonsurgical repairs3, 5, 15, 23, 106 ( Fig 12-10). The location of the perforation is the prime determinant in the strategy and material used in the surgical approach.144

Fig 12-10 Fig 12-10 (a) Mandibular left first molar in a symptomatic 32-year-old man. Note the presence of a separated file at the mesial root apex and concomitant transportation and perforation of the mesial root canal during previous treatment. (b) Identification of the perforation site. (c) Canal obturation with gray MTA. (d) Surgical resection of the mesial roots, removal of the separated file, and MTA retrofill. (e) Nine-month radiographic review. (f) Three-year recall radiograph showing complete remineralization of the osteotomy site.

According to Gutmann and Harrison,106 certain aspects of the case must be considered before surgical treatment can be initiated: The amount of remaining bone and any surrounding osseous defects The overall periodontal status The duration and size of the defect The surgical accessibility The soft tissue attachment level The patient’s oral hygiene and medical status The surgeon’s soft tissue management expertise Management must take into account soft tissues, muscle and frenal attachments, bony eminences, and defect location. Many of the principles of root-end surgery apply to hard and soft tissue management during perforation repair surgery. 145 To compensate for osseous defects that may extend interproximally, horizontal releasing incisions should include the entire papilla.14, 106 Vertical incisions limit the severing of blood vessels, improve access, and reduce hemorrhaging. Diseased tissues and foreign materials are removed to improve visibility, hemostatic agents are applied, and repair materials are placed following completion of a Class I cavity preparation.11, 14, 106, 146

Materials and methods employed to achieve hemostasis during surgery include anesthetic infiltration using 2% lidocaine with 1:50,000 epinephrine, epinephrinesaturated cotton pellets or collagen sponges, trichloroacetic acid, calcium sulfate, lasers, and electrosurgery/cautery.11, 106, 147–150 Root surface conditioning agents have been recommended to remove the smear layer and create a surface favorable for cell adhesion and growth and repair of the periodontium before placement of repair materials.14 The choice of conditioning agents is case specific and typically includes citric acid, tetracycline, or ethylenediamine tetraacetic acid used to demineralize dentin without injuring adjacent tissues. However, pretreatment of the root surface is contraindicated when MTA is used as the repair material. 151 Although guided tissue regeneration has shown benefits when used in endodontic surgery for large periapical lesions and through-and-through defects, its value in perforation repair surgery has not been established.152–156

Intentional replantation Intentional replantation is an alternative surgical procedure performed when orthograde and retrograde procedures have failed or are not practicable. Proper case selection and careful execution of protocols have resulted in success rates of 80% to 95%.157–161 The procedure is indicated for conical-rooted teeth with large perforation defects or perforations inaccessible without extensive bone removal. Surgically extruded teeth have also shown success rates as high as 95%.162 Replanted teeth with furcation defects or vertical root fractures or in patients with advanced periodontal disease will have an unfavorable prognosis.11,158,159 The treatment requires atraumatic tooth removal that minimizes damage to the cementum and periodontal ligament, and the procedures can be technique sensitive.163–165 The tooth is held in forceps, and moisture is maintained throughout the procedure with a physiologic salt solution. Extraoral time must be minimized (20 minutes or less) to prevent potential ankylosis or external inflammatory root resorption. The root and perforation site are inspected with the DOM before the appropriate repair material is used to seal the defect. Replantation surgery should be considered as a last resort when all other strategies have been exhausted.161

Summary Perforations arising during mechanical efforts to complete root canal therapy or

during the restoration of the endodontically treated tooth have a substantial negative impact on long-term tooth retention. More general dentists are attempting root canal treatment, and increasing numbers of compromised teeth are being restored as patient expectations grow. 11 While the treatment strategy for mechanically induced perforations has remained essentially unchanged for more than a century, technical advances including the DOM, illumination, advanced surgical approaches, and the introduction of bioactive repair materials have improved healing rates and allow for the ultimate goal of regenerating the injured periodontium.

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the granulocyte-macrophage progenitor cells. Int Endod J 2006;39:40–47. 88. Wang L, Yin SH, Zhong SL, Jie YQ. Cytotoxicity evaluation of three kinds of perforation repair materials on human periodontal ligament fibroblasts in vitro [in Chinese]. Hua Xi Kou Qiang Yi Xue Za Zhi 2009;27:479–482. 89. Vanni JR, Della-Bona A, Figueiredo JA, Pedro G, Voss D, Kopper PM. Radiographic evaluation of furcal perforations sealed with different materials in dogs’ teeth. J Appl Oral Sci 2011;19:421–425. 90. Lodiene G, Kleivmyr M, Bruzell E, Ørstavik D. Sealing ability of mineral trioxide aggregate, glass ionomer cement and composite resin when repairing large furcal perforations. Br Dent J 2011;210(5):E7. 91. Tsatsas DV, Meliou HA, Kerezoudis NP. Sealing effectiveness of materials used in furcation perforation in vitro. Int Dent J 2005;55:133–141. 92. Nakata TT, Bae KS, Baumgartner JC. Perforation repair comparing mineral trioxide aggregate and amalgam using an anaerobic bacterial leakage model. J Endod 1998;24:184–186. 93. Hashem AA, Hassanien EE. ProRoot MTA, MTA-Angelus and IRM used to repair large furcation perforations: Sealability study. J Endod 2008;34:59–61. 94. Weldon JK Jr, Pashley DH, Loushine RJ, Weller RN, Kimbrough WF. Sealing ability of mineral trioxide aggregate and SuperEBA when used as furcation repair materials: A longitudinal study. J Endod 2002;28:467–470. 95. Holland R, de Souza V, Nery MJ, Otoboni Filho JA, Bernabé PF, Dezan Júnior E. Reaction of dogs’ teeth to root canal filling with mineral trioxide aggregate or a glass ionomer sealer. J Endod 1999;25:728–730. 96. Regan JD, Gutmann JL, Witherspoon DE. Comparison of Diaket and MTA when used as root-end filling materials to support regeneration of the periradicular tissues. Int Endod J 2002;35:840–847. 97. Mente J, Hage N, Pfefferle T, et al. Treatment outcome of mineral trioxide aggregate: Repair of root perforations. J Endod 2010; 36:208–213. 98. Juárez Broon N, Bramante CM, de Assis GF, et al. Healing of root perforations treated with mineral trioxide aggregate (MTA) and Portland cement. J Appl Oral Sci 2006;14:305–311. 99. Miranda RB, Fidel SR, Boller MA. L929 cell response to root perforation repair cements: An in vitro cytotoxicity assay. Braz Dent J 2009;20:22–26. 100. Roberts HW, Toth JM, Berzins DW, Charlton DG. Mineral trioxide aggregate material use in endodontic treatment: A review of the literature. Dent Mater 2008;24:149–164. 101. Bargholz C. Perforation repair with mineral trioxide aggregate: A modified matrix concept. Int Endod J 2005;38:59–69. 102. Evans G. A Practical Treatise on Artificial Crown and Bridge Work, ed 3.

Philadelphia: S. S. White, 1893. 103. Smale M, Colyer J. Diseases and Injuries of the Teeth. New York: Longmans, Green, 1893. 104. Roda RS. Root perforation repair: Surgical and nonsurgical manage ment. Pract Proced Aesthet Dent 2001;13:467–472. 105. Roda RS, Gettleman BH. Nonsurgical retreatment. In: Hargreaves KH, Cohen S (eds). Cohen’s Pathways of the Pulp, ed 10. St Louis: Mosby Elsevier, 2011:890–952. 106. Gutmann JL, Harrison JW. Periradicular surgery. In: Surgical Endo dontics. Boston: Blackwell Scientific, 1991:151–384. 107. Ivey DW, Calhoun RL, Kemp WB, Dorfman HS, Wheless JE. Orthodontic extrusion: Its use in restorative dentistry. J Prosthet Dent 1980;43:401–407. 108. Smidt A, Lachish-Tandlich M, Venezia E. Orthodontic extrusion of an extensively broken down anterior tooth: A clinical report. Quintessence Int 2005;36:89–95. 109. Menezes R, da Silva Neto UX, Carneiro E, Letra A, Bramante CM, Bernadinelli N. MTA repair of a supracrestal perforation: A case report. J Endod 2005;31:212–214. 110. Tsukiboshi M. Autotransplantation of teeth: Requirements for predictable success. Dent Traumatol 2002;18:157–180. 111. Rankow HJ, Krasner PR. Endodontic applications of guided tissue regeneration in endodontic surgery. J Endod 1996;22:34–43. 112. Smidt A, Nuni E, Keinan D. Invasive cervical root resorption: Treatment rationale with an interdisciplinary approach. J Endod 2007;33:1383–1387. 113. Alhadainy HA, Himel VT. Evaluation of the sealing ability of amalgam, Cavit, and glass ionomer cement in the repair of furcation perforations. Oral Surg Oral Med Oral Pathol 1993; 75:362–366. 114. Alhadainy HA, Himel VT. An in vitro evaluation of plaster of Paris barriers used under amalgam and glass ionomer to repair furcation perforations. J Endod 1994;20:449–452. 115. Bogaerts P. Treatment of root perforations with calcium hydroxide and SuperEBA cement: A clinical report. Int Endod J 1997; 30:210–219. 116. Lemon RR. Nonsurgical repair of perforation defects. Internal matrix concept. Dent Clin North Am 1992;36:439–457. 117. Zou L, Liu J, Yin S, Li W, Xie J. In vitro evaluation of the sealing ability of MTA used for the repair of furcation perforations with and without the use of an internal matrix. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;105:e61–e65. 118. Ibarrola JL, Biggs SG, Beeson TJ. Repair of a large furcation perforation: A

four-year follow-up. J Endod 2008;34:617–619. 119. Reyes-Carmona JF, Felippe MS, Felippe WT. The biomineralization ability of mineral trioxide aggregate and Portland cement on dentin enhances the push-out strength. J Endod 2010;36:286–291. 120. Uyanik MO, Nagas E, Sahin C, Dagli F, Cehreli ZC. Effects of different irrigation regimens on the sealing properties of repaired furcal perforations. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009;107:e91–e95. 121. Tsai YL, Lan WH, Jeng JH. Treatment of pulp floor and stripping perforation by mineral trioxide aggregate. J Formos Med Assoc 2006;105:522–526. 122. Unal GC, Maden M, Isidan T. Repair of furcal iatrogenic perforation with Mineral Trioxide Aggregate: Two years follow-up of two cases. Eur J Dent 2010;4:475–481. 123. Vajrabhaya LO, Korsuwannawong S, Jantarat J, Korre S. Biocompatibility of furcal perforation repair material using cell culture technique: Ketac Molar versus ProRoot MTA. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:48–50. 124. Zairi A, Lambrianidis T, Pantelidou O, Papadimitriou S, Tziafas D. Periradicular tissue responses to biologically active molecules or MTA when applied in furcal perforation of dogs’ teeth. Int J Dent 2012;2012:257832. 125. Hamad HA, Tordik PA, McClanahan SB. Furcation perforation repair comparing gray and white MTA: A dye extraction study. J Endod 2006;32:337– 340. 126. Shahi S, Rahimi S, Hasan M, Shiezadeh V, Abdolrahimi M. Sealing ability of mineral trioxide aggregate and Portland cement for furcal perforation repair: A protein leakage study. J Oral Sci 2009;51:601–606. 127. Ferris DM, Baumgartner JC. Perforation repair comparing two types of mineral trioxide aggregate. J Endod 2004;30:422–424. 128. Adiga S, Ataide I, Fernandes M, Adiga S. Nonsurgical approach for strip perforation repair using mineral trioxide aggregate. J Conserv Dent 2010;13:97–101. 129. Aziz S, Ali AK, Moeen F. Two successful cases of root perforation repair using mineral trioxide aggregate. Pak Oral Dent J 2008;28:103–106. 130. Castellucci A. The use of mineral trioxide aggregate to repair iatrogenic perforations. Dent Today 2008;27:74,76,78–80. 131. Witherspoon DE, Small JC, Regan JD, Nunn M. Retrospective analysis of open apex teeth obturated with mineral trioxide aggregate. J Endod 2008;34:1171– 1176. 132. Bogen G, Kuttler S. Mineral trioxide aggregate obturation: A review and case series. J Endod 2009;35:777–790.

133. Shih M, Marshall FJ, Rosen S. The bactericidal efficiency of sodium hypochlorite as an endodontic irrigant. Oral Surg Oral Med Oral Pathol 1970;29:613–619. 134. Harrison JW, Hand RE. The effect of dilution and organic matter on the antibacterial property of 5.25% sodium hypochlorite. J Endod 1981;7:128–132. 135. Hafez AA, Cox CF, Tarim B, Otsuki M, Akimoto N. An in vivo evaluation of hemorrhage control using sodium hypochlorite and direct capping with a oneor two-component adhesive system in exposed nonhuman primate pulps. Quintessence Int 2002;33:261–272. 136. Poggio C, Arciola CR, Dagna A, Chiesa M, Sforza D, Visai L. Antimicrobial activity of sodium hypochlorite-based irrigating solutions. Int J Artif Organs 2010;33:654–659. 137. Zou L, Shen Y, Li W, Haapasalo M. Penetration of sodium hypochlorite into dentin. J Endod 2010;36:793–796. 138. Gatot A, Arbelle J, Leiberman A, Yanai-Inbar I. Effects of sodium hypochlorite on soft tissues after its inadvertent injection beyond the root apex. J Endod 1991;17:573–574. 139. Reeh ES, Messer HH. Long-term paresthesia following inadvertent forcing of sodium hypochlorite through perforation in maxillary incisor. Endod Dent Traumatol 1989;5:200–203. 140. Kerbl FM, Devilliers P, Litaker M, Eleazer PD. Physical effects of sodium hypochlorite on bone: An ex vivo study. J Endod 2012; 38:357–359. 141. Mitchell RP, Baumgartner JC, Sedgley CM. Apical extrusion of sodium hypochlorite using different root canal irrigation systems. J Endod 2011;37:1677–1681. 142. Hulsmann M, Hahn W. Complications during root canal irrigation—Literature review and case reports. Int Endod J 2000;33:186–193. 143. Kleier DJ, Averbach RE, Mehdipour O. The sodium hypochlorite accident: Experience of diplomates of the American Board of Endodontics. J Endod 2008;34:1346–1350. 144. Rud J, Rud V, Munksgaard EC. Retrograde sealing of accidental root perforations with dentin-bonded composite resin. J Endod 1998;24:671–677. 145. Johnson BR, Fayad MI, Witherspoon DE. Periradicular surgery. In: Hargreaves KH, Cohen S (eds). Cohen’s Pathways of the Pulp, ed 10. St Louis: Mosby Elsevier, 2011:720–776. 146. Lin LM, Gaengler P, Langeland K. Periradicular curettage. Int Endod J 1996;29:220–227. 147. Kim S, Rethnam S. Hemostasis in endodontic microsurgery. Dent Clin North Am 1997;41:499–511.

148. Makkawy HA, Koka S, Lavin MT, Ewoldsen NO. Cytotoxicity of root perforation repair materials. J Endod 1998;24:477–479. 149. Nanami T, Shiba H, Ikeuchi S, Nagai T, Asanami S, Shibata T. Clinical applications and basic studies of laser in dentistry and oral surgery. Keio J Med 1993;42:199–201. 150. Deppe H, Horch HH. Laser applications in oral surgery and implant dentistry. Lasers Med Sci 2007;22:217–221. 151. Abedi HR, Torabinejad M, McMillan P. The effect of demineralization of resected root ends on cementogenesis [abstract]. J Endod 1997;23:258. 152. Tsesis I, Rosen E, Tamse A, Taschieri S, Del Fabbro M. Effect of guided tissue regeneration on the outcome of surgical endodontic treatment: A systematic review and meta-analysis. J Endod 2011;37:1039–1045. 153. Needleman IG, Worthington HV, Giedrys-Leeper E, Tucker RJ. Guided tissue regeneration for periodontal infra-bony defects. Cochrane Database Syst Rev 2006;2:CD001724. 154. Dietrich T, Zunker P, Dietrich D, Bernimoulin J-P. Periapical and periodontal healing after osseous grafting and guided tissue regeneration treatment of apicomarginal defects in periradicular surgery: Results after 12 months. Oral Surg Oral Med Oral Pathol Endod 2003;95;474–482. 155. Duggins LD, Clay JR, Himel VT, Dean JW. A combined endodontic retrofill and periodontal guided tissue regeneration technique for the repair of molar endodontic furcation perforations: Report of a case. Quintessence Int 1994;25:109–114. 156. Salman MA, Quinn F, Dermody J, Hussey D, Claffey N. Histological evaluation of repair using a bioresorbable membrane beneath a resin-modified glass ionomer after mechanical furcation perforation in dogs’ teeth. J Endod 1999;25:181–186. 157. Grossman LI. Intentional replantation of teeth. J Am Dent Assoc 1966;72:1111– 1118. 158. Bender IB, Rossman LE. Intentional replantation of endodontically treated teeth. Oral Surg Oral Med Oral Pathol Endod 1993;76:623–630. 159. Kratchman S. Intentional replantation. Dent Clin North Am 1997;41:603–617. 160. Raghoebar GM, Vissink A. Results of intentional replantation of molars. J Oral Maxillofac Surg 1999;57:240–244. 161. Rouhani A, Javidi B, Habibi M, Jafarzadeh H. Intentional replantation: A procedure as a last resort. J Contemp Dent Pract 2011;12:486–492. 162. Tsukiboshi M. Autotransplantation of Teeth. Chicago: Quintessence, 2001:158. 163. Panzarini SR, Holland R, de Souza V, Poi WR, Sonoda CK, Pedrini D. Mineral trioxide aggregate as a root canal filling material in reimplanted teeth.

Microscopic analysis in monkeys. Dent Traumatol 2007;23:265–272. 164. Andreasen JO, Borum MK, Jacobsen HL, Andreasen FM. Replantation of 400 avulsed permanent incisors 4. Factors related to periodontal healing. Endod Dent Traumatol 1995;11:76–89. 165. Paulsen HU, Andreasen JO, Schwartz O. Pulp and periodontal healing, root development and root resorption subsequent to transplantation and orthodontic rotation: A long-term study of autotransplanted premolars. Am J Orthod Dentofacial Orthop 1995;108:630–640.

Removal of Posts Canals of endodontically treated teeth referred to endodontists for retreatment often contain broken instruments (separated endodontic instruments, silver points, Gates Glidden tips, lentulo spirals, broken posts, etc). The ability to remove these broken instruments from within the root system will in part define the success of the root canal treatment.1 Abbott2 showed that 9.4% of patients in an endodontic practice require the removal of endodontic posts. Many factors influence post removal, such as the dentist’s clinical experience and judgment and the choice of technique. 3, 4 Other factors include the clinician’s knowledge of tooth morphology, 5–7 the type of cement used to cement the post,8–10 and the shape (active or passive) and type of post used (prefabricated or cast). When a solid object must be removed from a root canal, most general dentists will refer the procedure to an endodontist.2 Of special concern is the removal of intact or broken posts because previously treated teeth have already been weakened by the loss of tooth structure.2 Because dentists may have had little or no training in post removal, they are often concerned about the potential for root fracture during attempts to retrieve the post, or they may not have the appropriate post removal equipment in their clinics. Many endodontists also fear the potential for root fracture during removal of cemented posts, or they may believe that post removal devices cannot be depended on to work.11 According to Stamos and Gutmann,11 other reasons for choosing a surgical approach include the failure to remove or loosen the post after a reasonable effort has been made and instances in which the post is large, long, or threaded, and the

crown and post appear to be intact. Quite often, the surgical approach carries its own challenges (eg, treatment of the palatal root of a maxillary molar). Overall, periapical surgery has a lower success rate than post removal.12 Should it be decided that the endodontically treated tooth is restorable, the dentist must be aware of the options available for removal of the foreign object within the canal and make a decision concerning the best solution for that particular situation. In reality, there is no true best method for all situations, and therefore a post removal device or technique must be selected and adapted according to the tooth presentation at hand. The goal always will be to preserve the entire remaining tooth structure so that the best foundation will remain for the planned tooth restoration. This factor is crucial when working with a tooth where much of the radicular dentin has already been removed by the initial placement of the post, and the crown has been compromised by its previous history.13

Risks of Post Removal Procedures Post removal devices to manage endodontic retreatment have been in use for a long time. These can be divided into three different categories: mechanical post removal devices, high-speed rotary instruments, and ultrasonic devices. It has been believed, and still generally is, that post removal devices increase the risk of root fracture, although a study by Castrisos and Abbott14 did not support this idea. The attempted removal of posts or other foreign objects from the canal of a tooth may cause cracks, vertical root fracture, or perforation15–19 as a result of direct mechanical action from the transfer of ultrasonic energy into the tooth. When any kind of fracture does occur, it may be from new crack formation or from the activation of a previously existing weakness, located either internally or externally in the root. Even the act of obturating root canals has been shown to create intradentin cracks (initiating at the canal surface) or other incomplete cracks.20 A study by Altshul et al 19 found that the removal of posts from roots by ultrasonic energy resulted in more cracks in roots (in the cementoenamel junction region) than endodontically treated teeth without posts. So the association between post removal and root cracks has been clearly established in the literature. In the very rare instance when a complete vertical root fracture does occur, it is quite possible that it was due to a previously existing defect. When the length of a dowel post exceeds two-thirds the length of the root, the increased stress levels in the apical portion of the root increase the likelihood of a fracture, especially in the thin root form.21 The type of post and the location in the arch (anterior versus posterior) play a role in the success of its removal from the canal. Nonmetallic prefabricated posts

have a modulus of elasticity close to that of dentin,22–26 and they have been associated with fewer root fractures.24, 27–32 A proposed advantage of fractured nonmetallic posts is their purported ease of removal.13, 28, 33–36 Root fractures are not generally associated with the removal of silver points.37 Although the fracture of a tooth or its root is a common concern for dentists, evidence indicates that fewer than 0.002% of roots do break when posts are removed.14 Abbott13 examined the records of 1,600 patients who had posts removed from teeth, either mechanically or with ultrasonics, and found only one tooth that had fractured during the procedure. A small number of fractured posts were removed by a combination of ultrasonics and the Masserann Kit (Micro-Mega). Stamos and Gutmann11 showed that the most common post removal device (used by 45% of endodontists in Australia) was the Eggler post remover (Automaton Vertriebs). This device was far more likely to be used than the Gonon (or Thomas) post removal system (FFDM Pneumat) or the Ruddle Post Removal System (SybronEndo), even when all three were available for use. The Eggler post remover is considered to be the easiest of these three devices to use because the others require that the post (or a core) be trephined to a predetermined size before it is grasped by a mandrel-like device for removal. These devices are reviewed later in this chapter.

Mechanical Devices All mechanical post removal devices require some degree of direct contact with the intraradicular post and sufficient remaining tooth structure to provide a fulcrum or reciprocal surface to support the removal instrument. Because posts are available in a range of diameters, from a variety of manufacturers, not all post removal devices easily adapt to the cemented post, requiring that some modification of the coronal end be done. Should more of the post diameter be removed than required, there is an added chance that the end of the post may break under removal force. This will necessitate the removal of more tooth structure or the abandonment of the procedure. Most mechanical devices do have limited success in removing threaded posts from the canals. Threaded posts are best removed by grasping the exposed and flattened head of the post and gently turning it, usually in a clockwise direction (usually in a counterclockwise direction). While this procedure is performed, all efforts must be made to avoid angling the instrument, which would place lateral pressure on the root.

S. S. White Post Extractor The S. S. White Post Extractor (S. S. White) is a grasp-andpull device. Its use requires sufficient troughing around the coronal end of the post. This is done to provide access to enough of the post to allow creation of a threaded surface on the post by which the post puller may be secured. Removal of tooth structure by any method further weakens the tooth, and the effort of threading the instrument securely on the post may increase the likelihood of root fracture.

Little Giant Post Puller The Little Giant Post Puller (LGPP; Yamazoe Dental) claims to be more conservative of remaining tooth structure while reducing the risk of fracture from torquing forces or from root perforation ( Fig 13-1). Because reciprocal forces are placed on a level occlusal face of the root, forces are theoretically distributed evenly on the root. This procedure requires, as do many others, that a flat surface be created on the root before the extraction of the post is attempted. The shape of the LGPP limits its usefulness mostly to anterior teeth, and the post may have to be reduced in diameter so that it may be accommodated within the jaws of the Post Puller (Fig 13-2).

Fig 13-1 Little Giant Post Puller. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Fig 13-2 (a) The maxillary right lateral and central incisors have been restored with cast posts and cores that require removal for endodontic retreatment. (b) The mesial and lingual surfaces of the cast post are flattened in the same plane with a rotary instrument to allow the jaws of the device to firmly grasp the core. (c) The legs of the device are positioned firmly on the mesial and distal tooth preparation surfaces. (d) The knurled knob of the LGPP is turned to move the jaws coronally, unseating the cast post. It is important that the post be removed in line with the long axis of the tooth. (e) The post and core have been successfully removed. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Gonon post removal system The Gonon post removal system, also known as the Thomas Extracteur de Pivots, was first introduced by Dr Gonon in 1955 and was later modified by Dr P. Machtou. This sytem can be used for the removal of parallel or tapered passive posts (cast or prefabricated), casts posts, or threaded posts. It requires that enough of the post be accessible for shaping; this is often accomplished by exposing the head of the post with a bur (Figs 13-3 and 13-4). Once enough of the post has been exposed, then an accompanying endcutting hollow bur is employed to shape the proximal end of the post (reducing its diameter). This trephine bur will also thread the post for a few millimeters so that the included specially made mandrel may be screwed on the post.

Fig 13-3 (a) Schematic of a cast post and core that requires removal for endodontic retreatment. (b) A rotary instrument is used to reduce the diameter of the core. (c) The core is further reduced with a Gonon bur. (d) The core is threaded with a Gonon trephine bur. (e) A mandrel with a washer and cushions in place is threaded on the post, and then the knurled knob is turned to remove the post. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Fig 13-4 Gonon post puller device.

At any point before the trephine is used, ultrasonic vibration and long shank round burs (such as the Munce Discovery Burs [Fig 13-5]) may be employed in an attempt to loosen the cementing medium in the canal. Often the cement will be weakened sufficiently at this point to preclude or to enhance the use of the mandrel. If still necessary, the mandrel may then be grasped with extraction pliers supplied in the kit after a series of washers are positioned around the post to protect the tooth from the lifting action of the pliers (Fig 13-6). Should the post be successfully removed at this point, the retreatment of the tooth may proceed following inspection of the root to verify its integrity.

Fig 13-5 Munce Discovery Burs (CJM Engineering).

Fig 13-6 (a) Radiograph of a maxillary right lateral incisor with an apical lesion requiring the removal of a cast post and core and endodontic retreatment. (b) The cast post and core is isolated with rubber dam. (c) The cast post and core is shaped into a roughly cylindric shape. (d) A Munce Discovery Shallow Troughers (CJM Engineering) is used to remove the cement around the post. (e) A special bur is used to thread the head of the cast post and core. (f) Application of counterclockwise rotational force using the wrench. (g) Gonon post in place and ready to be used. (h) The screw is turned to open the jaws and create an extraction force. (i) Removal of post and preservation of the tooth structure. (j) Postoperative radiograph showing the endodontically retreated root canal and the definitive restoration. (Courtesy of Dr Marga Ree, Amsterdam.)

The Gonon post removal system is less invasive then the Masserann Kit and the LGPP and requires less removal of tooth structure.11, 38

Masserann Kit

The Masserann Kit is specially designed for the removal of broken metallic files, posts, and silver points from a root canal.39 It has been used for more than four decades, and success rates of 44% to 73% have been reported with the use of this technique.40–42 The system consists of a series of color-coded trephine burs and two sizes of tubular extractors. The trephine burs are end-cutting, hollow burs of increasing size. The bestfitting bur is positioned over the involved canal and advanced over the broken object with a counterclockwise movement. It is advanced along the canal and around the post until 2 mm of the post is freestanding within the canal. The next smaller–sized trephine then replaces the first bur, ensuring a firm grip on the free end of the post, whereon the post can be retrieved from the canal. The trephine burs were formerly turned manually but can now be driven in a low-speed dental handpiece. The extractor is tubelike and has a plunger rod, which, when screwed inside the extractor, locks the exposed coronal end of the fragment against internal embossment just short of the end of the extractor. The post can now be removed by a counterclockwise rotation. Several clinical reports have discussed the effectiveness of the Masserann Kit43– 45 (Fig 13-7). However, the application of this technique has limitations. When this kit is used, a direct line of access to the post is needed because the entire extraction assembly is rather large and rigid. Another drawback may be the need to remove sufficient tooth structure to access the coronal end of the post. The Masserann Kit is limited in usefulness to straight canals or portions of the canal, and this may be one reason why perforations of the root are more frequent with this instrument when it is used deeper in curved canals.46 The Masserann Kit is also considered to be inferior to ultrasonics.47

Fig 13-7 (a) Radiograph of a maxillary right first molar requiring endodontic retreatment and containing three prefabricated metallic posts that need removal. (b) Access cavity preparation prior to removal of prefabricated posts. Minimal dentin is removed with this system. (c) Prefabricated metallic posts removed with the use of a Masserann Kit. (d) Access cavity is cleaned of cements and other debris. (e) Recall postoperative radiograph after completion of conventional endodontic retreat ment. (Courtesy of Dr Terrell F. Pannkuk, Santa Barbara, CA.)

Eggler post remover The Eggler device is best applied to the treatment of anterior teeth and is of lesser effectiveness posterior to the first premolar. This is due to its large size. For the forceps end of the Eggler device to grip the post and/or any associated core, the post and core must be approximately 2 mm in diameter, so reshaping with a bur may be necessary. No trephine burs or extraction mandrels are used. Also, it is imperative that at least 1 mm of tooth structure be maintained around the apical end of the post; therefore, radiographs of the tooth and its roots must be taken from at least two different angles. As with all mechanical post removal devices, the pulling forces must be applied along an axial direction, and any deviation from this direction increases the risk of a root fracture. Castrisos et al15 determined that removing posts at an angle of as little as 10 degrees increases the risk of fracture of the tooth. A recent survey found that the Eggler post remover was the most commonly used device among endodontists in Australia and New Zealand, followed by the Masserann Kit.14

WAM’X post removal device The WAM’X post removal device is a simple device that looks like a forceps. The kit also includes three pairs of assorted prongs, which allows free rotation of the prongs when they are in function. Three pairs of color-coded silicone slices are also included and used to stabilize the prongs in place. This device could be used in both arches anteriorly and posteriorly. The action is along the vertical axis of the root and posts, minimizing the risk of root fracture (Fig 13-8).

Fig 13-8 (a) Radiograph of a mandibular right second premolar requiring the removal of a cast post and core and endodontic retreatment. (b) Mandibular right second premolar restored with a cast post and core. (c) A U-shaped platform is created around the post using a rotary carbide instrument. The roof of this space should be the post material, and the floor should be the tooth structure. This U-shaped space should be large enough for the prongs of the WAM’X post removal device (Wam) to fit. (d) The three pairs of prongs are tried, and the best size is chosen. Ultrasonic vibration is applied all around the prepared post at full power using water spray alternatively with dry vibration. (e) An appropriate silicone slice is inserted around the post to create an interface between the tooth structure and the prongs of the WAM’X forceps. (f) The silicone slice should stabilize the prongs in place without holding them. (g) The prongs are gently inserted over the silicone slice between the tooth structure and the cast post and core. The device is then activated by turning the screw. (h) The cast post and core is removed with minimal opening of the prongs. Finger pressure should be applied on the top of the post and core to avoid its possible expulsion upon removal. (i) Recall postoperative radiograph after completion of conventional endodontic retreatment. (Courtesy of Dr Chaniotis Antonis, Athens, Greece.)

Perforated tube post removal method This method for post removal was introduced by Dr C. John Munce for the removal of prefabricated metallic posts. The first step when using this method is to expose the prefabricated post by removal of any buildup material and the dissection of the cement line around the post. A perforated tube is then charged with composite autopolymerizing resin and inserted along with a previously fitted Hedström file over the notched post. The Hedström file is immediately rotated clockwise to lodge it securely between the post and the wall of the tube while engaging the prepared notches on the post. The Hedström file’s taper and aggressive flutes will enhance the union of the file with the composite resin as it is augered between the lumen of the tube and the notched post prior to polymerization. Light-cured composite resin perhaps could work, but light would not reliably cure resin in the tube, so it is recommended that autopolymerizing composite be used for this procedure. Similar to the grasp and pull type post removers that rely on the grabbing feature being more retentive than the cementing/ bonding agent holding the post in place, the perforated tube post removal method uses the perforations in the tube in combination with the composite resin, the notches on the post, and the Hedström file to achieve the objective of making the tube very retentive on the post such that, when the Ruddle Post extraction plier is inserted and activated, it overcomes the retentive capacity of the cementing/bonding agent that holds the post in the root. After confirmation of the polymerization of the composite resin, a stout needle holder and a curved hemostat are locked onto the tube, and the Ruddle Post remover is inserted between the protected porcelain crown or tooth structure and the needle holder and activated (Fig 13-9).

Fig 13-9 (a) Radiograph showing a very long titanium post that needs to be removed prior to endodontic retreatment. (b) The cement line is dissected from around the post with #½ and #¼ Munce Discovery Bur Deep Troughers (CJM Engineering). (c and d) The exposed post is then notched at various levels with a high-speed wheel bur. (e) A metal tube that will fit over the prepared post is selected and perforated through and through three times with a #½ round high-speed bur. (f) The tube is then rotated 90 degrees on its long axis and perforated three more times. (g) The prepared tube is charged with autopolymerizing composite resin and then inserted over the notched post. (h) A previously fitted Hedström file is immediately inserted through the open end of the tube and rotated clockwise, lodging it securely between the post and the wall of the tube while engaging the prepared notches on the post. (i) Upon confirmation of polymerization of the composite resin, a stout needle holder and a curved hemostat are both locked onto the tube, and the Ruddle Post Remover is inserted between the protected porcelain crown and the needle holder. (j) The post remover is activated to separate the beaks and launch the post. (k) The removed post. (l) Postoperative radiograph showing the endodontically retreated root canals. (Courtesy of Dr C. John Munce, Santa Barbara, CA.)

Rotary Instruments When rotary instruments are used to remove posts or to remove tooth structure in order to access the post, the tooth is further weakened and compromised. In 1978, Tylman and Malone 48 stated that posts should be entirely drilled out of a canal, even though this incurred a high risk of root perforation, destructive heat production, and severe weakening of tooth structure. A study by Stamos and Gutmann 11 found that 62% of American endodontists drilled out posts. The inherent risk of this approach is the almost inevitable loss of tooth substance, even to the extent of root perforation, and the weakening of the tooth, leading to future root fracture. Special rotary instruments provided by several manufacturers of posts can be used to remove their own posts. Clinical experience suggests that care must be taken not to enlarge the canal beyond the diameter of the post, which further weakens the tooth. When the removal of tooth structure is necessary to gain access to the post, it is most important that sufficient tooth structure remain to prepare a circumferential ferrule of a minimum height of 1.5 to 2.0 mm.49–51 A consensus among clinicians is that the removal of nonmetallic prefabricated posts is less time-consuming than the removal of prefabricated metal posts.34 A recent study by Frazer et al52 determined the time for removal was less than 12 minutes, while other studies have reported nonmetallic post removal times of 1.4 to 7 minutes.28, 33, 53 The nature of the nonmetallic post can contribute to the time needed for complete removal. For example, carbon fiber–reinforced epoxy resin posts are usually easier to remove than glass fiber–reinforced epoxy resin posts. Removal kits for nonmetallic post removal have been suggested33–36; it is recommended that they be a single-use item34 (Fig 13-10). The editor also recommends the use of pointed diamonds, long shank round burs, and ultrasonics as possible instruments for the removal of these posts (Fig 13-11). Special burs can also be used to remove or loosen cemented posts. The Roto-Pro TM (Ellman International) carbide bur is a noncutting tapered bur with six sides used with a highspeed handpiece. When used in a high-speed handpiece rotating at 200,000 rpm, the six flat sides of the bur create a vibratory frequency of 1.2 million cycles per minute (or 20,000 cycles per second), making this device a powerful rotating ultrasonic instrument. The bur is available in four different shapes. When it comes in contact with the post, the bur creates vibrations that cause the post to loosen.

Fig 13-10 D.T. light-post removal kit for glass fiber–reinforced epoxy resin post (Bisco). (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Fig 13-11 D.T. (a) Radiograph showing a maxillary left second premolar with a glass fiber–reinforced post and apical lesion. (b) A pilot hole is prepared in the middle of the post using a high-speed diamond rotary instrument. (c) Munce Discovery Burs are used to remove the glass fiber–reinforced post as long as visibility is not a problem. (d) The Munce burs are used until the root canal filling is reached. (e) The root canal treatment for both

buccal and palatal canals is finalized. (f) The roots are obturated with warm gutta-percha. (g) Postoperative radiograph showing the endodontically re-treated root canals and the definitive restoration. (Courtesy of Dr Marga Ree, Amsterdam.)

A sufficient number of radiographs should be taken to ensure that the clinician has not perforated the canal (Fig 13-12). Radiographic monitoring is required in all retrieval situations.4 This is particularly true if the post is the same shade as the dentin, making it difficult to differentiate between materials.

Fig 13-12 (a) A broken glass fiber–reinforced epoxy resin post is present in a maxillary left central incisor. (b) The buccal view reveals a short post that is inadequate for the retention of the core material. (c) The occlusal view shows the close proximity in shade between the nonmetallic prefabricated post and dentin. (d) The post has been removed, and margins of the tooth have been prepared to obtain a ferrule effect. (e) A final radiograph showing the post space preparation. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Ultrasonic Devices The challenge of post removal from the endodontically treated root canal has most recently been addressed by the use of ultrasonic energy. Ultrasonic energy is considered practical and safe for removing posts from the canal and is noted for its better preservation of the remaining dentin. This energy is used not so much to

remove the post and other objects from the root canal but rather to loosen the cement, thereby facilitating the removal exercise. Hence, these techniques reduce the force needed to remove a post, thereby reducing the possibility of root fracture and perforation.5, 13, 14, 19, 46, 53–58 Buoncristiani et al54 demonstrated the efficacy of ultrasonic vibration over the use of sonic energy. They found that it takes 6.0 to 8.3 minutes for ultrasonics to remove a parallel-sided post cemented 4 mm into an extracted tooth with zinc phosphate cement, while traction was applied. Ultrasonic frequencies usually range from 20,000 to 40,000 Hz. Several authors have studied the combination of ultrasound alone or as an adjunct to traction forces. They concluded that, with the use of ultrasonic energy, most posts can be removed successfully within 10 minutes.19, 59–61 The effectiveness of ultrasonic energy in post removal appears to be dependent on two factors: the nature and volume of the post material and the cementing medium. Ultrasonic removal techniques are generally applied to parallel-sided posts, while threaded posts are more likely to be unscrewed. The length of the post (or remaining section of a post) more positively affects its retention than the diameter of the post.21, 62 Robbins63 suggested that a 2-mm increase in post length can directly increase post retention by as much as 30%. Bergeron et al64 found that up to 4.5 times more force is needed to remove a parallel-sided post than a conical post. The deeper a post is embedded within a root canal, the more resistant it may be to vibration energy at a given power output of the ultrasonic unit. Smith5 affirmed the direct relationship between ultrasonic vibration time and the length of the post or portion of the post, while the diameter of the post was found to be irrelevant. He also suggested that loosening requires approximately 1 minute or less of vibration time for each millimeter of post (or fragment) length. The mechanics of post loosening involve the characteristics of the post itself. A post will conduct vibration energy according to the square root of its modulus of elasticity.54 A material with a higher modulus of elasticity will transmit oscillations better than one with a lower modulus. Because titanium has a lower modulus of elasticity, it would transmit vibratory energy to the binding cement less efficiently than would a steel post.65 Therefore, a shorter working time should be expected for removal of a steel post than for removal of a titanium post of similar length and width. Titanium has a low modulus of elasticity when compared with stainless steel parts. A low modulus of elasticity decreases the ultrasonic vibration, hence reducing the effectiveness of the ultrasonic device. However, in one controlled in vitro study of the ultrasonic forces required to remove stainless steel and titanium posts, no statistically significant difference was found.66

Effect of the cement on ultrasonic removal Cements commonly used in studies of the removal of solid objects from within the root canal are zinc phosphate and composite resin cements. Gomes et al67 found that retention values were higher with composite resin cements than other cements, and this may work against the dentist attempting to extract such a cemented post by a post-pulling approach. They also noted that ultrasonic vibration is less effective for removal of a titanium post cemented with a composite resin cement than it is for removal of titanium posts cemented with other types of cement. This may suggest that resin has a dampening effect on the applied vibration energy. Zinc phosphate cement was statistically more resistant than glass-ionomer cement to traction forces on root posts.68 There is greater likelihood that glassionomer cements will fracture under ultrasonic vibrations; composite resin cements are less likely to do so because of their more viscoelastic properties.67 Posts cemented with composite resin cements may therefore require a longer time with ultrasonic contact to loosen than would posts cemented with zinc phosphate or glass-ionomer cements.66, 67, 69 Johnson et al70 found that 16 minutes of ultrasonic vibration was required to loosen and remove a 9-mm ParaPost (Coltène/Whaledent) from the canals of teeth when cemented with zinc phosphate cement. In contrast, Chandler et al69 found that neither ultrasonic vibration nor the Masserann Kit was effective for parallel-sided posts cemented with composite resin cement. This supports the findings of Satterthwaite et al55 concerning the dislodging of posts cemented with composite resin cement (ceramic and stainless steel). Yoshida et al 71 have reported that, for silver-palladium alloy posts, non– composite resin cements most often fracture cohesively, followed by failure of the metal-cement bond and, lastly, the dentin-cement bond. A study by Silva et al72 found that ultrasonic vibration proved to be effective in the removal of 10-mm-long metal posts cemented with glass-ionomer cement. There was no difference between prefabricated metal and cast posts, and the researchers were unable to relate cement thickness to the efficiency of ultrasonic vibration. Following the removal of posts and foreign objects from the root canal, careful cleaning of the canal must be performed to remove all remaining cement and cement residue from the canal walls.

Ultrasonic techniques for post removal Use of ultrasonic energy to loosen and remove cemented posts can preserve tooth structure, decrease the risk of root perforation, and potentially shorten the procedure

time. When ultrasonic instruments are being used, all persons in the immediate vicinity should be protected from possible damage to the auditory system caused by airborne subharmonics. In addition, aerosols generated have been shown to carry microorganisms, including those that are pathogenic. These airborne hazards may be minimized by the use of appropriate protective gear, adequate application of suction to the treatment field, and rinsing the patient’s oral cavity with an antiseptic mouthwash prior to beginning the treatment session, which has been shown to reduce the amount of airborne microorganisms. To effect the loosening of the post, it is necessary that the post be in contact with the tip of the ultrasonic device. A recent study 73 found that positioning the tip of the ultrasonic device perpendicular to the core surface of a cast post and core, and specifically close to the core-dentin junction, reduces the retention of the cast post in the root canal. Thus, the energy within the tip is transmitted to the post itself, then outward into the cement layer. The destruction of the cement integrity begins nearest to the ultrasonic tip and moves in the direction of the root apex. As the cement breaks down, the post begins its initial loosening. With alternating application of vibrations and flushing of loosened cement with water, the fulcrum point on the post moves toward the apex, resulting in greater movement of the post. Another approach is to grasp the end of the post with a hemostat and apply the tip of the ultrasonic unit to the hemostat (Fig 13-13). Alternatively, the introduction of a Hedström file (size 20 or larger), at least 2 to 4 mm deep between the post and the canal, followed by the application of vibration forces is another way of compromising the cement bond. The file must be wedged snugly in place to avoid loss of transmitted forces. Should the file become loose, it should be removed and replaced with the nextlarger size.

Fig 13-13 A cemented prefabricated post is vibrated through the application of the ultrasonic tip to a mosquito hemostat holding the post. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

After the cement layer has been broken, removal of the post is usually successful, depending on the extent to which it can be grasped for removal. It is important that a rubber dam be positioned to protect the patient from endodontic files that may be ejected from the tooth under ultrasonic vibration. Braga et al74 showed that, when clinically feasible, the use of two ultrasonic tips applied simultaneously at opposite sides of a cemented post shortens the period of time needed to loosen the post compared with a single-tip approach. They alternated the positioning of the tips for 30-second time periods, that is, with mesiodistal placement followed by buccolingual pairing in a continued alternating process. Increasing the time to 60-second intervals resulted in only a small decrease in overall time needed to loosen the posts. To further maximize the transfer of energy to the cement layer, alternating application of the instrument tip to the occlusal surface of the post intermittently with lateral positioning would undoubtedly shorten the procedure time. Some authors75 suggest the use of solvents in conjunction with ultrasonic devices. The ultrasonic energy will help the solvent penetrate into the canal space and interrupt the integrity of the cement.

Following successful post removal, the remaining tooth structure must be examined carefully to verify its integrity, particularly the absence of any root fracture. The existence of fractures will doom the tooth for any further restorative efforts, and the tooth must be removed. Overall, the successful use of ultrasonic energy to remove cemented posts is related to the following factors: the nature of the post material in terms of the modulus of elasticity; the length of the post fragment; the cement type and thickness and the percentage of the post actually contacting cement; and the nature of the external post surface (smooth versus threaded). Any combination of these factors may play a significant role in the effectiveness and efficiency of this procedure. Existing leakage within the canal may make an additional difference in the ease of removal of the post because the process may then be less time-consuming.

Effects of ultrasonic vibration on tissues Energy transmitted to a cemented object within the root canal structure ripples beyond the object itself, possibly affecting the overall root structure, the periodontium, and the surrounding bone. Fractures may be created in the root, or existing fracture lines may be enlarged, leading to failure. The periodontal fibers may be irreversibly heated, creating histologic changes. Yoshida et al 71 found temporary inflammation of the gingival connective tissue apical to the junctional epithelium. However, when the vibration time was less than 10 minutes, subsequent histologic studies indicated that the connective tissues and the periodontium were normal within 1 week. When a metal post must be cut with a bur, the bur should be applied to the metal slowly and intermittently to minimize the generation of heat. Cooling by continuous water spray will help to minimize temperature increases. Trenter and Walmsley 76 recommended that usage of the ultrasonic scaler be avoided if the irrigant water flow is less than 20 mL/min. Satterthwaite et al55 found that the surface temperature of roots increased by a mean value of 18.7°C after 30 minutes of ultrasonic vibration against both stainless steel posts and ceramic posts. Because of the nature of fiber posts, the creation and transfer of heat is usually not a concern.

Summary Planning for the restoration of teeth often includes the use of posts to assist in the distribution of forces placed on the coronal aspect of teeth. The process requires that

a careful evaluation be made of the tooth, including the remaining tooth structure coronal to the CEJ, the ability to create a ferrule effect, the size and shape of the root that will host the post, as well as the integrity of the remaining root structure. Careful attention should be paid in selecting the appropriate size of the post, followed by shaping and placement of the post, while considering the anatomy of the root and minimizing forces that may create stress points or initial crack formation. Even when all of this is done appropriately, fracture of the post may still occur. If this happens, the general dentist can either attempt to remove the post or refer the patient to an endodontic specialist for post removal. Experience has shown that the use of ultrasonic energy alone or in conjunction with mechanical approaches generally meets with success. The greatest risk in the removal process is the application of forces not aligned with the long axis of the root. While different kinds of cements can shorten or lengthen the removal time, the technical approach remains the same: grasping the coronal end of the post (after exposing it if necessary) and carefully loosening it, with or without applied ultrasonic energy. For nonmetallic posts, specially designed drills should be used according to the manufacturer’s instructions. Following post removal, a careful inspection of the root should be carried out in order to evaluate the integrity of the remaining root structure relative to its continued use in supporting the proposed restoration of the tooth and oral function.

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prefabricated post developed for the restoration of pulpless teeth. J Oral Rehabil 1990;17:599–609. 25. Malquarti G, Berruet RG, Bois D. Prosthetic use of carbon fiberreinforced epoxy resin for esthetic crowns and fixed partial dentures. J Prosthet Dent 1990;63:251–257. 26. Purton DE, Payne JA. Comparison of carbon fiber and stainless steel root canal posts. Quintessence Int 1996;27:93–97. 27. Sidoli GE, King PA, Setchell DJ. An in vitro evaluation of carbon fiber-based post and core system. J Prosthet Dent 1997;78:5–9. 28. Cormier CJ, Burns DR, Moon P. In vitro comparison of the fracture resistance and failure mode of fiber, ceramic and conventional post systems at various stages of restoration. J Prosthodont 2001; 10:16–36. 29. Martinez-Insua A, da Silva L, Rilo B, Santana U. Comparison of the fracture resistance of pulpless teeth restored with a cast post and core or carbon-fiber post with a composite core. J Prosthet Dent 1998;80:527–532. 30. Akkayan B. An in vitro study evaluating the effect of ferrule length on facture resistance of endodontically treated teeth restored with fiber-reinforced and zirconia dowel systems. Int J Prosthodont 2004;92:155–162. 31. Dean JP, Jeansonne BG, Sarkar N. In vitro evaluation of a carbon fiber post. J Endod 1998;24:807–810. 32. Fokkinga WA, Kreulen CM, Vallittu PK, Creugers NH. A structured analysis of in vitro failure loads and failure modes of fiber, metal, and ceramic post-andcore systems. Int J Prosthodont 2004;17:476–482. 33. Gesi A, Magnolfi S, Goracci C, Ferrari M. Comparison of two techniques for removing fiber posts. J Endod 2003;29:580–582. 34. De Rijk WG. Removal of fiber posts from endodontically treated teeth. Am J Dent 2000;13(spec No.):19B–21B. 35. Sakkal S. Carbon-fiber post removal technique. Compend Contin Educ Dent 1966;20:S86. 36. Peters SB, Canby FL, Miller DA. Removal of a carbon fiber post system [abstract]. J Endod 1996;22:215. 37. Suter B. A new method for retrieving silver points and separated instruments from root canals. J Endod 1998;24:446–448. 38. Machtou P, Sarfati P, Cohen AG. Post removal prior to retreatment. J Endod 1989;15:552–554. 39. Masserann J. Removal of metallic fragments from the root canal. J Br Endod Soc 1971;5:55–59. 40. Hülsmann M. Methods for removing metal obstruction from the root canal. Endod Dent Traumatol 1993;9:223–237.

41. Gencoglu N, Helvacioglu D. Comparisons of the different techniques to remove fractured endodontic instruments from root canal systems. Eur J Dent 2009;3:90–95. 42. Okiji T. Modified usage of the Masserann Kit for removing intracanal broken instruments. J Endod 2003;29:466–467. 43. Feldman G, Solomon C, Notaro P, Moskowitz E. Retrieving broken endodontic instruments. J Am Dent Assoc 1974;88:588–591. 44. Thirumalai AK, Sekar M, Mylswamy S. Retrieval of a separated instrument using a Masserann technique. J Conserv Dent 2008; 11:42–45. 45. Pai AR, Kamath MP, Basnet P. Retrieval of a separated file using Masserann technique: A case report. Kathmandu Univ Med J 2006;4:238–242. 46. Yoldas O, Oztunc H, Tinaz C, Alparslan N. Perforation risks associated with the use of Masserann endodontic kit drills in mandibular molars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2004;97:513–517. 47. Friedman S, Stabholz A, Tamse A. Endodontic retreatment—Case selection and technique. 3. Retreatment techniques. J Endod 1990;16:543–549. 48. Tylman SD, Malone WFP (eds). Tylman’s Theory and Practice of Fixed Prosthodontics, ed 7. St Louis: Mosby, 1978:534–535. 49. Hoag EP, Dwyer TG. A comparative evaluation of three post and core techniques. J Prosthet Dent 1982;47:177–181. 50. Tan PLB, Aquilino SA, Gratton DG, et al. In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations. J Prosthet Dent 2005;93:331–336. 51. Baba NZ, Goodacre CJ, Daher T. Restoration of endodontically treated teeth: The seven keys to success. Gen Dent 2009;57:596–579. 52. Frazer RQ, Kovarik RE, Chance KB, Mitchell RJ. Removal time of fiber posts versus titanium posts. Am J Dent 2008;21:175–178. 53. Lindemann M, Yaman P, Dennison JB, Herrero AA. Comparison of the efficiency and effectiveness of various techniques for removal of fiber posts. J Endod 2005;31:520–522. 54. Buoncristiani J, Seto BG, Caputo AA. Evaluation of ultrasonic and sonic instruments for intraradicular post removal. J Endod 1994;20:486–489. 55. Satterthwaite JD, Stokes AN, Frankel NT. Potential for temperature change during application of ultrasonic vibration to intraradicular posts. Eur J Prosthodont Restor Dent 2003;11:51–56. 56. Berbert A, Filho MT, Ueno AH, Bramante CM, Ishikiriama A. The influence of ultrasound in removing intraradicular posts. Int Endod J 1995;28:100–102. 57. Krell KV, Neo J. The use of ultrasonic endodontic instrumentation in the retreatment of a paste-filled endodontic tooth. Oral Surg Oral Med Oral Pathol

1985;60:100–102. 58. Dixon EB, Kaczkowski PJ, Nicholls JI, Harrington GW. Comparison of two ultrasonic instruments for post removal. J Endod 2002; 28:111–115. 59. Gaffney JL, Lehman JW, Miles MJ. Expanded use of the ultrasonic scaler. J Endod 1981;5:228–229. 60. Chalfin H, Weseley P, Solomon C. Removal of restorative posts for the purpose of nonsurgical endodontic retreatment: Report of cases. J Am Dent Assoc 1990;120:169–172. 61. Garrido AD, Fonseca TS, Alfredo E, Silva-Sousa YT, Sousa-Neto MD. Influence of ultrasound, with and without water spray cooling, on removal of posts cemented with resin or zinc phosphate cements. J Endod 2004;30:173– 176. 62. Nergiz I, Schmage P, Ozcan M, Platzer U. Effect of length and diameter of tapered posts on the retention. J Oral Rehabil 2002; 29:28–34. 63. Robbins JW. Guidelines for the restoration of endodontically treated teeth. J Am Dent Assoc 1990;120:558–564. 64. Bergeron BE, Murchison DF, Schindler WG, Walker WA 3rd. Effect of ultrasonic vibration and various sealer and cement combinations on titanium post removal. J Endod 2001;27:13–17. 65. O’Brien J. Dental Materials: Properties and Selections. Chicago: Quintessence, 1989:549–551. 66. Hauman CH, Chandler NP, Purton DG. Factors influencing the removal of posts. Int Endod J 2003;36:687–690. 67. Gomes AP, Kubo CH, Santos RA, Santos DR, Padilha RQ. The influence of ultrasound on the retention of cast posts cemented with different agents. Int Endod J 2001;34:93–99. 68. Soares JA, Brito-Júnior M, Fonseca DR, et al. Influence of luting agents on time required for cast post removal by ultrasound: An in vitro study. J Appl Oral Sci 2009;17:145–149. 69. Chandler NP, Qualtrough AJ, Purton DG. Comparison of two methods for the removal of root canal posts. Quintessence Int 2003;34:534–536. 70. Johnson WT, Leary JM, Boyer DB. Effect of ultrasonic vibration on post removal in extracted human premolar teeth. J Endod 1996; 20:487–488. 71. Yoshida T, Shunji G, Tomomi I, Shibata T, Sekine I. An experimental study of the removal of cemented dowel-retained cast cores by ultrasonic vibration. J Endod 1997;23:239–241. 72. Silva MR, Biffi JCG, Mota AS, Fernandes Neto AJ, Neves FD. Evaluation of intracanal post removal using ultrasound. Braz Dent J 2004;15:119–126. 73. Braga NM, Silva JM, Carvalho-Júnior JR, Ferreira RC, Saquy PC, Brito-

Júnior M. Comparison of different ultrasonic vibration modes for post removal. Braz Dent J 2012;23:49–53. 74. Braga NM, Alfredo E, Vansan LP, Fonseca TS, Ferraz JA, SousaNeto MD. Efficacy of ultrasound in removal of intraradicular posts using different techniques. J Oral Sci 2005;47:117–121. 75. Glick DH, Frankp AI. Removal of silver points and fractured posts by ultrasonics. J Prosthet Dent 1986;55:212–215. 76. Trenter SD, Walmsley AD. Ultrasonic dental scaler: Associated hazards. J Clin Periodontol 2003;30:95–101.

Removal of Broken Instruments from the Root Canal System A major goal in endodontics is the removal of infected pulp tissue from the root canal system.1 Byström and Sundqvist2 demonstrated that cleaning and shaping can reduce the bacterial load in root canals. This can be accomplished by the use of endodontic files and other instruments. For many years, stainless steel K-files, Hedström files, and various types of instruments have been used for this purpose. Roane et al3 made a dramatic change in the design of endodontic files by developing the noncutting tip, leading to a new concept in root canal preparation called the balanced forces technique. The noncutting tip prevents ledging and apical transportation of the root canal; the balanced force motion allows the file to follow the canal path, thus preventing it from locking into the dentin. In the late 1980s, another revolutionary concept was introduced in endodontics: files made of nickel-titanium alloy with incredible new properties such as high flexibility and memory. These new properties opened a whole new frontier regarding root canal preparation, allowing better control to avoid ledging of the canal wall and root canal transportation; they also improved the handling of root canal curvatures.4 Subsequently, various rotary instrumentation systems were developed to facilitate cleaning and shaping of root canals. Another new concept was introduced to endodontics: files that could be rotated 360 degrees inside the root canal using the LightSpeed rotary system (SybronEndo), supposedly with less risk of instrument fracture.5 A different rotary file design (ProFile NiTi Rotary Instruments, Dentsply

Maillefer), with possibly improved effectiveness, was also developed, introducing the tapered and safe-landed concept in rotary files.6 Although nickel-titanium files are more flexible than those made of stainless steel, 360-degree rotation of a file inside a root canal may cause the file to get locked into dentin and break. Fracture of root canal instruments is one of the most troublesome incidents that can occur during rotary root canal preparation (Fig 14-1). Clinicians must be prepared to respond to and correct any problems that arise during root canal treatment and, even more importantly, should attempt to prevent problems from happening.7

Fig 14-1 (a) A separated Hedström file is located within the root canal of a mandibular molar. (b) The separated instrument is bypassed, but a small fragment remains inside. (c) The broken instrument has been successfully bypassed, and the root canal has been obturated. The instrument is now part of the filling material. (Courtesy of Dr Freddy Belliard, Madrid, Spain.)

The prevalence of broken instruments ranges from 0.5% to 5.0%.8–11 Small, narrow, and calcified canals, blockages, and curvatures contribute to the occurrence of file separation. The main causes of rotary file breakage, however, are cyclic fatigue and torsional stress. These can be prevented by creating a straight-line access, preflaring the coronal portion, and using hand files initially (glide path) before rotary files to reduce the tendency of files to lock in dentin and break.

Management Considerations: Bypass Versus Removal The location of broken instruments in the root canal system is important for the success of their removal. Typically, the most coronal location and the straightest canals improve the chances for removal. A clinical study 12 reported on the efforts to remove or bypass broken instruments. The most commonly broken instruments were Hedström files, followed by reamers, lentulo spirals, and Gates Glidden drills. The success rate for bypassing instruments was 19.4%, and the success rate for complete removal was 48.7%. The researchers also found that they had a 91% success rate in removing the instrument fragment when it was located coronal to the curvature.

When the broken piece was within the root canal curvature, the failure rate was 77%. The failure rate was 78% failure when the separated piece was located beyond the root canal curvature (Fig 14-2). The degree of root curvature also had an effect on the removal rate. The success rate was highest in roots with a curvature between 0 and 10 degrees. In roots with a curvature greater than 30 degrees, the success rate was very low.12

Fig 14-2 A separated instrument is located beyond the root canal apical foramen. (Courtesy of Dr Nadim Z. Baba, Loma Linda, CA.)

Another clinical study13 emphasized the importance of the preoperative condition of the tooth for its prognosis in cases of broken instruments. The prognosis was favorable for teeth with vital pulp tissue. In teeth with periapical lesions, healing occurred in only 50% of the cases. These results were supported by those of another clinical study, where the success rate for teeth with vital or nonvital pulps and no periapical lesion exceeded 96%, while that for teeth with pulpal necrosis and periapical lesions was only 86%.14 Several systems have been introduced for removal of broken instruments: the Masserann Micro Kit (Micro-Mega),15 the Canal Finder System (Endotechnic),16 and systems that use ultrasonic instruments.17 The choice of a system is influenced by several factors: the type of instrument broken, the stage of canal preparation, the location of a broken instrument (or file) within the canal, and the pulpal diagnosis (necrotic or vital). All these factors are important and need to be carefully evaluated. If a file is broken at the beginning of the instrumentation stage, it is likely

that some pulp tissue remains in the canal around the file and beyond. The location is also very important when the clinician is deciding whether to bypass or remove the instrument. If the broken segment of the file is located in the straight portion of the root canal, the chances for its removal will be higher. The closer to the apical third of the root canal or beyond its curvature, the harder to remove (Figs 14-3 to 14-5). This is one of the conditions that dictate which technique should be chosen for removal of the broken instrument.

Fig 14-3 (a) A separated instrument is located in the apical part of the mesial root of a mandibular left first molar. The instrument will be bypassed to avoid weakening of the already thin roots. (b) No. 15 files are inserted in all existing roots. (c) The initial gutta-percha cones are fitted. (d) The final radiograph shows the results of endodontic retreatment. (Courtesy of Dr Axel Yabroudi, Phoenix, AZ.)

Fig 14-4 (a) A separated instrument is in a favorable location in a mesial root of a maxillary right first molar. (b) The separated instrument has been removed, and endodontic retreatment is successful. (Courtesy of Dr Axel Yabroudi, Phoenix, AZ.)

Fig 14-5 (a and b) During root canal instrumentation by the patient’s general dentist, a Pro-Taper S1 rotary file (Dentsply) was separated inside the mesiobuccal canal of the second molar. It is important to plan the access and root canal treatment to consider possible accidents like this. The reason for the file separation was the lack of a straight-line access into the root canal and the coronal and buccolingual curvatures of the mesial root. The tortuous way of the bypassing file is shown in b. (c) For this particular case, it was possible to bypass the broken instrument and reach an adequate working length. Once the root canal was cleaned and shaped, it was possible to

take a titanium ultrasonic file to vibrate out the broken file (arrows). (d) Final obturation, with acceptable results.

In a meta-analysis review18 on the impact of a retained instrument on treatment outcome, a healing rate of 92.4% was found when a periapical lesion was not present versus an 80.7% success healing rate when a periapical lesion was present before treatment was initiated. Finally, the removal of fractured rotary nickeltitanium endodontic instruments was more successful in teeth with less curved canals and a longer radius of curvature (greater than 4.4 mm).19 More recently, microscopes and specially designed tips for ultrasonic units have become popular and successful aids to the removal of broken files.20–25 In a clinical study26 in which specialists attempted to remove broken instruments in a total of 170 consecutive situations, 162 instruments could be removed without perforation of the root canal, corresponding to a success rate of 95%. The failure rate of 5% represented eight instruments that could not be removed; root wall perforation occurred in one case. The lowest success rate, 93%, was found in maxillary molars, while the highest success rate, 100%, was achieved in maxillary premolars and maxillary and mandibular anterior and canine teeth. All removal failures occurred in cases where the fractured instruments were located apically or in the middle and apical part of the root. Regarding the angle of root canal curvature, the lowest success rates were found between 21 degrees and 50 degrees. The position of the instrument within the root canal, the angle of the curvature of the root canal, and the location of the fractured instrument in relation to the root canal curvature were the decisive factors that had a negative influence on the treatment outcome.26 The removal method tested represents a highly effective technique for the retrieval of fractured instruments. A consideration of no small importance is whether the efforts to retrieve or bypass a broken instrument will result in significant loss of tooth structure or root perforation.27 Alternatives to heroic efforts to save a compromised tooth must be discussed with the patient.

Removal Techniques Two common techniques for removal of broken instruments will be described. Regardless of which method is used, preparation for engagement of the broken instrument begins with use of dental dam to ensure proper isolation of the tooth. The access cavity must allow a straight-line approach to the canal, the orifice of which can be enlarged with Gates Glidden burs to create a funnel-shaped coronal canal

preparation; this process will allow visualization of the broken instrument, which is enhanced with the use of an operating microscope. A tapered diamond bur is used to modify the tip of a No. 3 Gates Glidden drill; the largest diameter of the active portion of the drill is sectioned to create the so-called staging platform. It is of paramount importance that the clinician be aware of the danger zone, which is often the thin distal wall of the mesial root of mandibular molars; this area is prone to perforation if the canal preparation is excessive. Fine ultrasonic tips (eg, zirconium nitride–coated ProUltra Endo tip 4 or 5, Dentsply) are used to trephine around the obstruction to unlock it and free it from the dentin. The ultrasonic intensity should be set no higher than 4 or 5. Special attention must be paid to keeping the canal wet and the ultrasonic tip cool. When the broken file is free from the surrounding dentin, a titanium ProUltra Endo tip 6 is used in a counterclockwise motion to help loosen the broken piece. During the use of this titanium ultrasonic tip, the power setting should be increased to three-quarters of the maximum power setting of the ultrasonic unit. If the broken instrument cannot be visualized after the coronal aspects of the canal are prepared, it is recommended that no further attempts be made to remove it. A broken piece that is located beyond the canal curvature is almost impossible to remove via this technique because ultrasonic tips will allow only straight-down cutting inside the root canal. The risk of perforation is increased in these situations.28 Removal of more apically located instrument fragments may be attempted with the Instrument Removal System (iRS, Dentsply), a new two-component system designed to mechanically engage broken instruments (Fig 14-6). Each microtube has a small plastic handle to enhance vision during placement, a side window to improve mechanics, and a 45-degree beveled end to “scoop up” the coronal end of a broken instrument. Each screw wedge has a knurled metal handle, a left-handed screw mechanism, and a solid cylinder that tapers toward its distal end to facilitate engagement of an obstruction.

Fig 14-6 (a) A fractured rotary instrument is located in the mesiobuccal canal of a mandibular right molar. (b) The hollow cannula iRS system is fitted on the fractured fragment of the file. (c) The root canal is free of the broken instrument. (d) Endodontic treatment has been completed. (e) The hollow cannula holds the removed in strument fragment. (Courtesy of Dr Carlos Saucedo, Monterrey, Mexico.)

Summary Removal of fractured instruments from inside the root canals truly represents a great challenge. We need to carefully study the case for better planning and better prognosis. As reviewed in this chapter, the location is key for attempting their removal. The chances of success and the technique most suitable for the case depend on the location of the fractured instrument within the root canal. Because of the difficulty, it is necessary to refer the patient to a specialist for removal. Endodontists are usually equipped with a microscope, ultrasonic unit, and the appropriate tips. This will usually facilitate the task, but we will never have the certainty of being able to remove instruments left in the root canal.

References 1. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am 1974;18:269–296. 2. Byström A, Sundqvist G. Bacteriologic evaluation of the efficacy of mechanical root canal instrumentation in endodontic therapy. Scand J Dent Res 1981;89:321–328. 3. Roane JB, Sabala CL, Duncanson MG Jr. The “balanced force” concept for

instrumentation of curved canals. J Endod 1985;11: 203–211. 4. Walia HM, Brantley WA, Gerstein H. An initial investigation of the bending and torsional properties of Nitinol root canal files. J Endod 1988;14:346–351. 5. Wildey WL, Senia ES. A new root canal instrument and instrumentation technique: A preliminary report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1989;67:198–207. 6. Blum JY, Cohen A, Machtou P, Micallef JP. Analysis of forces developed during mechanical preparation of extracted teeth using Profile NiTi rotary instruments. Int Endod J 1999;32:24–31. 7. Bahcall JK, Carp S, Miner M, Skidmore L. The causes, prevention and clinical management of broken endodontic rotary files. Dent Today 2005;24:74,76,78– 80. 8. Spili P, Parashos P, Messer HH. The impact of instrument fracture on outcome of endodontic treatment. J Endod 2005;31:845–850. 9. Knowles KI, Hammond NB, Biggs SG, Ibarrola JL. Incidence of instrument separation using LightSpeed rotary instruments. J Endod 2006;32:14–16. 10. Wolcott S, Wolcott J, Ishley D, et al. Separation incidence of Protaper rotary instruments: A large cohort clinical evaluation. J Endod 2006;32:1139–1141. 11. Iqbal MK, Kohli MR, Kim JS. A retrospective clinical study of incidence of root canal instrument separation in an endodontics graduate program: A PennEndo database study. J Endod 2006; 32:1048–1052. 12. Hülsmann M, Schinkel I. Influence of several factors on the success or failure of fracture instruments from the root canal. Endod Dent Traumatol 1999;15:252–258. 13. Crump MC, Natkin E. Relationship of broken root canal instruments to endodontic case prognosis: A clinical investigation. J Am Dent Assoc 1970;80:1341–1347. 14. Sjögren U, Hagglund B, Sundqvist G, Wing K. Factors affecting the long term results of endodontic Treatment. J Endod 1990; 16:498–504. 15. Masserann J. L’extraction des fragments de tenons intraradiculaires. Actual Odontostomatol 1966;75:392–402. 16. Hülsmann M. Removal of fractured root canal instruments using the Canal Finder System. Dtsch Zahnarztl Z 1990;45:229–232. 17. Souyave LC, Inglis AT, Alcalay M. Removal of fractured instruments using ultrasonic. Br Dent J 1985;159:521–523. 18. Panitvisai P, Parunnit P, Sathorn C, Messer HH. Impact of a retained instrument on treatment outcome: A systematic review and meta-analysis. J Endod 2010;36:775–780. 19. Alomairy KH. Evaluating two techniques on removal of fractured rotary nickel-

titanium endodontic instruments from root canals: An in vitro study. J Endod 2009;35:559–562. 20. Fu M, Zhang Z, Hou B. Removal of broken files from root canals by using ultrasonic techniques combined with dental microscope: A retrospective analysis of treatment outcome. J Endod 2011; 37:619–622. 21. Ward JR, Parashos P, Messer HH. Evaluation of an ultrasonic technique to remove fractured rotary nickel-titanium endodontic instruments from root canals: An experimental study. J Endod 2003;29:756–763. 22. Gencoglu N, Helvacioglu D. Comparison of the different techniques to remove fractured endodontic instruments from root canal systems. Eur J Dent 2009;3:90–95. 23. Suter B, Lussi A, Sequeira P. Probability of removing fractured instruments from root canals. Int Endod J 2005;38:112–113. 24. Fu M, Zhang Z, Hou B. Removal of broken files from root canals by using ultrasonic techniques combined with dental microscope: A retrospective analysis of treatment outcome. J Endod 2011; 37:619–622. 25. Ruddle CJ. Nonsurgical retreatment. J Endod 2004;30:827–845. 26. Cujé J, Bargholz C, Hülsmann M. The outcome of retained instrument removal in a specialist practice. Int Endod J 2010;43:545–554. 27. Pettiette MT, Conner D, Trope M. Procedural errors with the use of nickeltitanium rotary instruments in undergraduate endodontics [abstract PR 24]. J Endod 2002;28:259. 28. Ruddle CJ. Removal of broken instruments. Endod Prac 2003;6: 13–22.

Endodontic Treatment of a Tooth with a Prosthetic Crown While the restoration of endodontically treated teeth is widely researched and reported,1–4 the preferred method for management of an endodontic situation in a tooth that already has a crown is not clearly defined in the literature. This could be due to the relatively low incidence of pulpal involvement in teeth with complete crowns. It has been reported that only about 2% to 15% of teeth restored with complete crowns reveal signs of pulpal involvement necessitating endodontic treatment.5 In a long-term clinical study, 6 the condition of extensive fixed partial dentures was investigated 10 years after cementation. Endodontic treatment of the abutment teeth after cementation was required in only 1% of the population studied. The need for endodontic treatment in a tooth that already has an artificial crown is an interesting dilemma, although the clinician is left with only two treatment options. One option is to remove the existing crown, evaluate the restorability of the remaining tooth structure, and restore the tooth with a new crown. The second option is to create an access preparation through the occlusal surface to gain access for endodontic treatment, removing carious tooth structure, and then subsequently to repair the access cavity. Preparation of a proper and convenient access cavity is critical to the success of endodontic therapy. Rankow and Krasner, 7 in their access cavity preparation guidelines, emphasize the importance of adequate access cavity preparation to ensure that the clinician can successfully locate all pulpal orifices. Hence, where an

artificial restoration such as a crown exists, a considerable amount of restorative material has to be removed to create an adequate access cavity preparation for appropriate visibility. This chapter discusses the keys to successful management of teeth that have prosthetic crowns and require endodontic treatment.

Indications and Contraindications If the crown has been recently placed, endodontic access preparation through the crown can be considered because there is a limited probability that carious tooth structure will have to be removed. The clinician can gain access to the pulp chamber and focus on performing a root canal procedure without simultaneously attempting to blindly excavate carious tooth structure. Similarly, when endodontic treatment is needed for reasons such as trauma and endodontic-periodontal lesions and no marginal leakage or caries is detected, then endodontic access through the existing crown is indicated. On the other hand, when a root canal treatment is required, and the tooth has a crown that has been in place for multiple years, the etiology of the problem must be carefully evaluated. If the etiology is caries and marginal leakage is detected, it is advisable that the clinician remove the crown and evaluate the restorability of the tooth before proceeding with an endodontic procedure.

Literature Review The main concerns regarding preparation of an endodontic access cavity through a crown are the potential loss of retention for the crown, poor visibility, difficulty in gaining proper access, and the potential to weaken the restoration and the underlying tooth structure. Numerous studies have reported on the effect of endodontic access cavity preparation and subsequent restorative procedures on the retention of crowns. While one study8 reported that the preparation of endodontic access cavities through existing crowns caused a significant decrease in the retention of crowns in maxillary anterior teeth, other studies have reported that the difference, if any, is not clinically significant.5, 9, 10 To alleviate these concerns, placement of secondary intention posts after endodontic treatment through existing crowns has been recommended to increase the retention of these crowns.11, 12 Yu and Abbott, 5 in an in vitro investigation, found that endodontic access

cavities reduced the retention of crowns fabricated on incisors. However, subsequent restoration with amalgam or a post with an amalgam core restored the original retention prior to access preparation. In this study, crowns retained with secondary intention posts showed significantly higher resistance to dislodgment forces than did those retained with just amalgam restorations. However, because of the wide range in standard deviation seen in post-retained crowns, the authors suggested that the higher retention observed with post-retained crowns might not always be clinically predictable. The preparation of a tooth for a secondary intention post necessitates the removal of a considerably greater amount of tooth structure to accommodate the post, decreasing the thickness of the dentinal walls; this can decrease the tooth’s resistance to root fracture.13 Mulvay and Abbott10 reported on the effect of endodontic access cavity preparation and resulting restorative procedures on molar crowns. This in vitro study reported that access preparations did reduce the resistance of molar crowns to displacement, and the reduction was related to the size of the access cavities. However, the authors reported that the retention of the crown was regained or even surpassed if the access cavity was restored with amalgam or glass ionomer; amalgam produced significant increases in retention.

Management Considerations Once it has been determined that a tooth with a prosthetic crown needs endodontic treatment, the following criteria must be assessed. Etiology of the need for endodontic treatment, which could be multifactorial: In recently placed crowns, the etiology could be microscopic exposure of the pulp during caries excavation; irreversible pulpitis resulting from thermal injury caused by inadequate cooling of the rotary instrument; trauma (parafunctional or direct injury); or marginal leakage resulting in caries lesions and subsequent pulpal necrosis. Periodontal status: The periodontal condition of the tooth must be assessed. If the periodontal status is poor, endodontic treatment is not a good option. In teeth with obvious marginal leakage or recurrent caries, it is prudent to remove the crown and assess the restorability of the tooth after thorough excavation of the caries and removal of the unsupported tooth structure all before beginning endodontic therapy. For all other etiologies, a conservative approach of accessing the root through the crown can be considered. Traumatic occlusal contacts that led to

pulpal necrosis have to be eliminated before endodontic treatment is begun. Creating enough access preparations for endodontic treatment is challenging in teeth without restorations and even more so when the clinician is navigating through an existing crown. The clinician is also at a disadvantage because the original anatomy of the tooth crown could have been altered by the crown and hence the crownroot angulation can be changed, resulting in removal of excess tooth structure during access cavity preparation. Also, restorative materials can impede visibility during preparation of the access cavity. Significant findings such as fracture lines in the pulp chamber and carious tooth structure can be overlooked because of the reduced visibility. The type of material used for the crown that has to be prepared with an access cavity must be considered as well. Metal-ceramic crowns are initially prepared with round diamond burs to remove the porcelain, and then the metal surfaces are prepared with carbide burs. Copious irrigation is advisable during access cavity preparation, especially for metal-ceramic crowns, to minimize the potential for fracture of the porcelain. However, despite the best precautions, the fracture of porcelain can occur during access cavity preparation, and patients must be warned about this possibility. The patient’s understanding of the possible need for a new crown, consent for treatment, and acknowledgment of possible complications should be confirmed in writing before proceeding. An advantage of access cavity preparation in all-metal crowns is the fact that the clinician does not have to be concerned about fracture of the restorative material (Fig 15-1) . Crowns made with base metal alloys offer an additional advantage in radiographic examination; the underlying tooth structure can be studied because base metal crowns are more transparent in radiographs than are crowns fabricated from noble alloys.

Fig 15-1 An access cavity has been prepared through a full-gold crown. (Courtesy of Dr Yeow Teh Tee, Loma Linda, CA.)

Restorative Materials Once the access cavity preparation and subsequent endodontic treatment have been completed, a determination has to be made regarding the use of a post as well as the restorative material that will be used to fill the access cavity. Although it has been reported in the literature that the addition of a post can increase retention of the crown, the author prefers the simple placement of a restorative material such as amalgam to restore the access cavity. A composite resin restoration can also be considered, especially when esthetics is a concern for the patient (Fig 15-2). Additional restorative materials to be considered are gold foil restorations, especially if the crown is metallic with high noble content, and ceramic plugs in the case of metal-ceramic and ceramic restorations.

Fig 15-2 (a) The access cavity is sealed temporarily after endodontic treatment through a metal ceramic crown. (b) The access cavity is prepared prior to restoration. (c) Dentin is etched with 35% phosphoric acid. (d) Porcelain is etched with buffered hydrofluoric acid. (e) Primer and bonding agent are applied. (f) Flowable composite resin is used to seal access to the root canals. (g) Composite resin is layered and polymerized in increments. (h) The access cavity is restored with composite resin. (Courtesy of Dr Joshua Cartter, Loma Linda, CA.)

A post is usually considered if the crown dislodges due to lack of retention. This would be an appropriate time to place a post conservatively without removing excessive tooth structure because the dislodgment of the crown improves visibility.

A post that fits the canal preparation should be considered; the post must be extended apical to the crest of the bone to avoid fractures.

Summary Preparation of an endodontic access cavity though an existing crown should be considered with caution because replacement of the existing crown has multiple advantages. The main advantage of an endodontic access cavity preparation though an existing crown is to offset costs associated with remaking a prosthetic crown. However, this decision must be compared with the advantages of better visibility, the ability to confirm restorability, and the overall better prognosis associated with a more conventional approach.

References 1. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: A literature review. 1. Success and failure data, treatment concepts. J Prosthodont 1994;3:243–250. 2. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: A literature review. 2. Maintaining the apical seal. J Prosthodont 1995;4:51–53. 3. Goodacre CJ, Spolnik KJ. The prosthodontic management of endodontically treated teeth: A literature review. 3. Tooth preparation considerations. J Prosthodont 1995;4:122–128. 4. Aquilino SA, Caplan DJ. Relationship between crown placement and the survival of endodontically treated teeth. J Prosthet Dent 2002;87:256–263. 5. Yu YC, Abbott PV. The effect of endodontic access cavity preparation and subsequent restorative procedures on incisor crown retention. Aust Dent J 1994;39:247–251. 6. Karlsson S. A clinical evaluation of fixed bridges, 10 years following insertion. J Oral Rehabil 1986;13:423–432. 7. Rankow HJ, Krasner PR. The access box: An ah-ha phenomenon. J Endod 1995;21:212–214. 8. McMullen AF 3rd, Himel VT, Sarkar NK. An in vitro study of the effect endodontic access preparation has upon the retention of porcelain fused to metal crowns of maxillary central incisors. J Endod 1989;15:154–156. 9. McMullen AF 3rd, Himel VT, Sarkar NK. An in vitro study of the effect

endodontic access preparation and amalgam restoration have upon incisor crown retention. J Endod 1990;16:269–272. 10. Mulvay PG, Abbott PV. The effect of endodontic access cavity preparation and subsequent restorative procedures on molar crown retention. Aust Dent J 1996;41:134–139. 11. Federick DR, Serene TP. Secondary intention dowel and core. J Prosthet Dent 1975;34:41–47. 12. Henry PJ, Bower RC. Secondary intention post and core. Aust Dent J 1977;22:128–131. 13. Tjan AHL, Whang SB. Resistance to root fracture of dowel channels with various thicknesses of buccal dentin walls. J Prosthet Dent 1985;53:496–500.

Retrofitting a Post to an Existing Crown The two most common types of postoperative complications associated with post and core have been found to be post loosening and root fracture.1 As a result, the dental clinician is sometimes faced with the failure of a post and core assembly under an existing crown or fixed dental prosthesis that can still provide satisfactory service because the integrity of the tooth-crown margin remains intact. Regardless of the cause of failure, retrofitting a cast post and core to an existing crown is a challenging and time-consuming procedure. Different techniques for retrofitting a cast post and core to an existing crown have been described in the literature.2–12 A one-stage technique 2–9 is used most often; however, a two-stage technique 8 has been proposed. In the first appointment, the radicular part is fabricated and cast, and in the second appointment, the existing crown is used to attach the resin core to the cast post. With the introduction of prefabricated posts, composite resin is commonly used as a core buildup material for retrofitting a post to an existing crown.10–12

Indications Retrofitting of a post to an existing crown could be indicated in the following situations: When the abutment of a recently placed crown requires endodontic therapy, and a post is needed. One prerequisite for such treatment is that the margins of the

existing crown are intact with an adequate ferrule of 1.5 to 2.0 mm. The occlusion and the proximal contacts must be appropriate, and the contours of the crown and the esthetics must be acceptable. In addition to all these prosthetic requirements, the root canal treatment needs to be adequate. The tooth should be evaluated for the presence of craze lines, fractures, perforations, or leakage around the gutta-percha. Microscopic examination may be required, and should this instrumentation not be available, then referral to an endodontist may be needed to rule out the presence of some possible defects. When a tooth has fractured after cementation of a crown, and there is a need for endodontic treatment and fabrication of a foundation restoration under the existing crown. When a cast post and core or a prefabricated post has fractured, leaving an intact ferrule and an existing crown with intact margins. When a post and core with its overlying crown has come loose, and the post length could be extended to provide better retention.

Advantages and Disadvantages Retrofitting a post to an existing crown saves the patient money by reusing an existing crown with adequate marginal fit. In addition, there will be no change to the occlusion or the esthetics of the restoration, and the clinician can restore the crown to its original condition in two appointments. This technique has two disadvantages, however. First, any inaccuracy in the fabrication or cementation of the cast post and core can lead to incomplete seating of the crown after cementation and the presence of open margins. Second, the material use is very critical because the accuracy in retrofitting the post to the existing crown is required at all stages of the fabrication.

Step-by-Step Retrofitting Procedure 1. Assess the crown to ensure that the marginal integrity of the existing crown is satisfactory (Fig 16-1). When there is a broken post segment present in the root, refer the patient to an endodontist for removal of the fragment (Figs 16-2 and 16-3). 2. Prepare the root canal by removing the obturation material to the required depth. 3. Select a 14-gauge solid plastic post that fits within the confines of the post preparation without binding (Fig 16-4). Adjust the length of the post, but leave

the post long enough so that it can be easily gripped (Fig 16-5). 4. Lightly lubricate the canal with the patient’s saliva, anesthetic solution, or water. (If using a water-soluble lubricant such as die lubricant, ensure that all lubricant can be subsequently removed, to prevent interference with cement retention.) 5. Use the bead-brush technique to apply pattern resin to the prepared canal as well as the body of the plastic post (Fig 16-6). Seat the post to the full depth of the canal (Fig 16-7). 6. Do not allow the resin to completely harden within the canal. Wait 30 to 45 seconds, and then remove and reseat the post and attached resin several times while the resin is still in its rubbery stage so that the pattern does not inadvertently become locked into the canal. 7. Remove the polymerized pattern, and inspect the resin for integrity and to ensure the absence of voids (Fig 16-8). Reseat the post and test it for adaptation and passivity. 8. Create mechanical retention on the coronal projection to engage the core (Fig 16-9). 9. Try in the crown to ensure that the post pattern created does not interfere with the seating of the crown (Fig 16-10). 10. Lubricate the internal surface of the crown with petroleum jelly or a watersoluble lubricant such as die lubricant. 11. Fill the crown with autopolymerizing acrylic resin (Fig 16-11). Seat the crown intraorally over the fitted post, firmly and precisely. 12. When the resin is polymerized, remove the crown and remove the excess core resin with a high-speed diamond and water spray; take care not to alter or reduce the coronal part of the resin pattern (Fig 16-12). 13. Remove, invest, and cast the resin pattern (Fig 16-13). 14. Reseat the crown over the polymerized core and evaluate the occlusion to be sure that the crown was completely seated over the resin core and is not in hyperocclusion. A minor amount of heavy contact can be adjusted, but large discrepancies require removal of the core resin and fabrication of a new core. 15. After casting, try in the post and core intraorally. Evaluate the fit and adjust the assembly as needed. 16. Prior to final cementation, subject the cast post and core to airborne-particle abrasion. 17. Cement the cast post and core (Fig 16-14). 18. Cement the crown (Fig 16-15).

Fig 16-1 A cast post has broken, and the core remains inside of the intaglio surface of the crown.

Fig 16-2 The patient has been referred to an endodontist for removal of the broken post in the maxillary left lateral incisor.

Fig 16-3 The broken post has been successfully removed from the root canal.

Fig 16-4 A prefabricated plastic pattern is tried in the post space.

Fig 16-5 The length of the post is adjusted but left long enough that it can be easily gripped.

Fig 16-6 (a) Monomer is applied to the body of the plastic post. (b) Resin is applied to the body of the post using the bead-brush technique.

Fig 16-7 The plastic post and resin are fully seated in the post space.

Fig 16-8 The polymerized pattern is removed from the post space and inspected for integrity and to confirm the lack of voids.

Fig 16-9 Mechanical retention is created on the coronal projection to engage the core.

Fig 16-10 The crown is tried in the mouth to ensure that the post pattern does not interfere with the seating of the crown.

Fig 16-11 The internal surface of the crown is lubricated and filled with autopolymerizing resin.

Fig 16-12 Excess resin has been removed with a high-speed diamond and water spray.

Fig 16-13 (a) The resin pattern post and core is removed and sent to the laboratory for investing and casting. (b) The cast post and core is ready for cementation.

Fig 16-14 The post and core is tried intraorally to evaluate the fit, adjusted if necessary, and cemented with permanent cement.

Fig 16-15 The crown is cemented.

Summary The failure of a post and core assembly under an existing crown or fixed dental prosthesis is a potential problem. If the restoration still provides satisfactory service because the integrity of the tooth-crown margin remains intact, the dentist can retrofit a post and core to the existing crown using the step-by-step procedure described in this chapter. The technique can be challenging and time-consuming, but it saves the patient money and avoids the need for fabrication of a new restoration.

References 1. Goodacre CJ, Bernal G, Rungcharassaeng K, Kan JYK. Clinical complications in fixed prosthodontics. J Prosthet Dent 2003;90: 31–41. 2. Jahangiri L, Feng J. A simple technique for the retrofitting of post and core to a crown. J Prosthet Dent 2002;88:234–235. 3. Shirdel K, Azarmehr P, Raoufi M. Construction of a post and core to fit a completed restoration. J Prosthet Dent 1977;38:229–231. 4. Tebrock OC. Technique for post-core removal from a crown and a new postcore fabrication. J Prosthet Dent 1980;43:463–466. 5. Brady WF. Restoration of a tooth to accommodate a preexisting cast crown. J

Prosthet Dent 1982;48:268–270. 6. Gardner FM, Robinson FG. Retrofitting a dowel and core to an existing crown. J Prosthet Dent 1977;77:636–637. 7. Priest G, Goerig A. Post and core fabrication beneath an existing crown. J Prosthet Dent 1979;42:645–648. 8. Hashem A, Gordon SR. Technique for two-stage retrofitted cast post and core. J Prosthet Dent 1992;68:386–387. 9. Rosen H. Dissolution of cement, root caries, fracture, and retrofit of post and cores. J Prosthet Dent 1998;80:511–513. 10. Chan DCN. Technique for repair of multiple abutment teeth under preexisting crowns. J Prosthet Dent 2003;89:91–92. 11. Berksun S. Rebuilding core foundations for existing crowns using a custommade template. J Prosthet Dent 2005;93:201–203. 12. Signore A, Benedicenti S, Kaitsas V, Barone M. Simplified technique for rebuilding a post and core foundation with a preexisting crown: A case report. Quintessence Int 2010;41:205–207.

Nadim Z. Baba, DMD, MSD, currently serves as a professor of restorative dentistry and the director of the Hugh Love Center for Research and Education in Technology at Loma Linda University School of Dentistry in California. He is a Diplomate of the American Board of Prosthodontics and a Fellow of the American College of Prosthodontists, as well as an active member of various professional organizations, including the Academy of Prosthodontics, the American Academy of Fixed Prosthodontics (AAFP), the International College of Prosthodontists, and the International College of Dentists. Dr Baba has received several honors and awards during his career, including the David J. Baraban Award from Boston University, the Claude R. Baker Faculty Award for Excellence in Teaching Predoctoral Fixed Prosthodontics in 2009 from the AAFP, and the California Dental Association Arthur A. Dugoni Faculty Award in 2010. He is also the associate editor for the esthetics/prosthetics/restorative section of the Journal of Dental Traumatology and a reviewer for the Journal of Prosthodontics.

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