Temporary Anchorage Devices in Clinical Orthodontics [1 ed.] 2019047712, 2019047713, 9781119513476, 9781119513650, 9781119513629

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Temporary Anchorage Devices in Clinical Orthodontics

Temporary Anchorage Devices in Clinical Orthodontics Edited by Jae Hyun Park, DMD, MSD, MS, PhD

Diplomate, American Board of Orthodontics Professor and Chair Postgraduate Orthodontic Program Arizona School of Dentistry & Oral Health A.T. Still University Mesa, AZ, USA; International Scholar Graduate School of Dentistry Kyung Hee University Seoul, South Korea

This edition first published 2020 © 2020 John Wiley & Sons, Inc. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. The right of Jae Hyun Park to be identified as the author of this work has been asserted in accordance with law. Registered Office John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA Editorial Office 111 River Street, Hoboken, NJ 07030, USA For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com. Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats. Limit of Liability/Disclaimer of Warranty The contents of this work are intended to further general scientific research, understanding, and discussion only and are not intended and should not be relied upon as recommending or promoting scientific method, diagnosis, or treatment by physicians for any particular patient. In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of medicines, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each medicine, equipment, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages. Library of Congress Cataloging‐in‐Publication Data Names: Park, Jae Hyun, 1963– editor. Title: Temporary anchorage devices in clinical orthodontics / edited by Jae Hyun Park. Description: Hoboken, NJ : Wiley-Blackwell, 2020. | Includes bibliographical references and index. Identifiers: LCCN 2019047712 (print) | LCCN 2019047713 (ebook) | ISBN 9781119513476 (hardback) | ISBN 9781119513650 (adobe pdf) | ISBN 9781119513629 (epub) Subjects: MESH: Orthodontic Anchorage Procedures–methods | Orthodontic Appliances | Case Reports Classification: LCC RK521 (print) | LCC RK521 (ebook) | NLM WU 400 | DDC 617.6/43–dc23 LC record available at https://lccn.loc.gov/2019047712 LC ebook record available at https://lccn.loc.gov/2019047713 Cover Design: Wiley Cover Images: (top left) Image of human teeth courtesy of Joorok Park, (bottom left) line drawing of human gum courtesy of KJ Lee, (right) Scanned image of human skeleton courtesy of Dr. Tung Nguyen Set in 9.5/12.5pt STIXTwoText by SPi Global, Pondicherry, India 10  9  8  7  6  5  4  3  2  1

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Contents List of Contributors  xi Foreword  xxi Preface  xxiii Acknowledgement  xxv About the Editor  xxvii Section I  Fundamental Perspectives on TADs  1   1 An Overview of Clinical Applications for Temporary Anchorage Devices (TADs)  3 Jae Hyun Park and Kyungsup Shin   2 Biomechanical Considerations for Controlling Target Tooth Movement with Mini-implants  17 Jung Yul Cha   3 Biomechanical Simulations for Various Clinical Scenarios Treated with TADs  27 Tai-Hsien Wu and Ching-Chang Ko   4 Histological Aspects During the Healing Process with TADs  37 Toru Deguchi   5 The Effects of TADs on the Alveolar Bone  45 Jing Chen, Karolina Kister, and Sunil Wadhwa   6 Mechanical Aspects of TADs  53 Toru Deguchi and Do-Gyoon Kim   7 Factors Affecting the Failure of TADs and Efforts to Improve the Biomechanical Stability of TADs  61 Sung-Hwan Choi and Chung-Ju Hwang   8 TADs and Successful Clinical Outcomes  69 Chung H. Kau and Terpsithea Christou   9 Clinical, Mechanical, and Diagnostic Indices for the Placement of TADs  77 Mitsuru Motoyoshi 10 Considerations for the Placement of TADs  83 Alejandro A. Romero-Delmastro, Onur Kadioglu, and G. Frans Currier 11 Understanding Implant Sites for TADs  91 Hyung Seog Yu

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12 Palatal TADs: Anatomical Considerations  99 Mohamed Bayome, Jae Hyun Park, and Yoon-Ah Kook 13 Implant Site Selection  107 Sebastian Baumgaertel Section II  Three-dimensional Correction with TADs  115 Anteroposterior Correction  117 14 Treating Skeletal Class II Hyperdivergent Patients: A Structured Decision-making Process  117 Peter H. Buschang and Larry Tadlock 15 Class II Correction with Skeletal Anchorage and Forsus  133 Min-Ho Jung 16 Distalization of Maxillary and Mandibular Molars with TADs  143 Jae Hyun Park, Mohamed Bayome, and Yoon-Ah Kook 17 Effective Treatment of Class II Malocclusion with the TAD-supported amda®  153 Moschos A. Papadopoulos 18 The Use of TADs with a Wilson Distalizing Arch  161 Tarek El‐Bialy and Budi Kusnoto 19 The Use of TADs to Correct Challenging Class II Sagittal Discrepancies  169 Goli K. Parsi and Mohamed I. Masoud 20 Dentofacial Orthopedics for Class III Corrections with Bone‐anchored Maxillary Protraction  185 Tung Nguyen 21 TAD-anchored Maxillary Protraction  191 Dong-Hwa Chung 22 Protraction Headgear with Surgical Miniplates  199 Bong‐Kuen Cha Transverse Correction  213 23 Total Arch Distalization and Control of Transverse Discrepancy with TADs  213 Ju Young Lee, Hwa Sung Chae, and Young Ho Kim 24 Maxillary Expansion in Skeletally Mature Patients with TADs  223 Won Moon 25 Maxillary Expansion with TADs in Young Adults  233 Peter Ngan and Hong He 26 TAD-assisted Naso-maxillo-pharyngeal Expansion  243 Kyung-A Kim, Su-Jung Kim, and Young-Guk Park

Contents

27 Scissor Bite Correction with TADs  259 Kyung-Min Lee, Sung-Hoon Lim, Gye-Hyeong Lee, and Jae Hyun Park Vertical Correction  271 28 Clinical Outcomes with TADs and Conventional Mechanics in Adult Skeletal Open Bite and Class II Patients  271 Toru Deguchi and Keiichiro Watanabe 29 Control of Vertical Dimension and Chin Position in Class II Malocclusion with Miniscrew Implants  285 P. Emile Rossouw, Dimitrios Michelogiannakis, and Glen Hintz 30 Anterior Open Bite Correction with One Midpalatal TAD  297 Tae-Woo Kim 31 Treatment of Open Bite with TADs: The Nature of Molar Intrusion and Relapse  309 Masato Kaku, Kazuo Tanne, and Kotaro Tanimoto 32 Double Arch Intrusion: Effective Use of TADs to Correct Vertical Excess  319 Cheol-Ho Paik and Hwee-Ho Kim

Section III  Clinical Applications of TADs  327 33 Three-dimensional Application of Orthodontic Miniscrews and Their Long-term Stability  329 Yoon Jeong Choi and Young-Chel Park 34 Tweed–Merrifield Directional Force Technology with TADs  337 Jong-Moon Chae and Jae Hyun Park 35 Non-extraction Treatment of Class II Hyperdivergent Patients with Orthodontic Mini-implants  349 Hyo-Won Ahn and Seung-Hak Baek 36 Clinical Application of Palatal TADs  359 Sung-Hoon Lim 37 Management of Missing Teeth with C-implants  369 Seong-Hun Kim, Min-Ki Noh, Kyu-Rhim Chung, and Gerald Nelson 38 Indirect Miniscrew Anchorage for Adjunctive Orthodontic Treatment: Clinical Applications and Stability  383 Kyung-Ho Kim, Yoon Jeong Choi, and Woowon Jang 39 TADs for Limited Orthodontic Treatment  393 Masamitsu Takahashi and Satoshi Uzuka 40 Uprighting Impacted Mandibular Second Molars with a Cantilever System Using TADs  405 Sang-Jin Sung 41 Orthodontic Treatment of TMD Patients with Posterior Intrusion Using TADs  415 Gye-Hyeong Lee, Sang-Mi Lee, Sun Kyong Yoo, and Jae Hyun Park

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42 Insights to Extraradicular Bone Screw Applications for Challenging Malocclusions  433 Chris H. Chang, Joshua S. Lin, Hsin-Yin Yeh, and W. Eugene Roberts 43 The Biomechanics of Extra-alveolar TADs in Orthodontics  445 Marcio Rodrigues de Almeida 44 A New and Innovative TAD System for Improved Stability and Versatility  455 Carlos Villegas and Flavio Uribe 45 Palatal and Ramal Plate Applications  467 Yoon-Ah Kook, Jae Hyun Park, and Mohamed Bayome 46 Miniscrews vs. Miniplates  477 Nour Eldin Tarraf and M. Ali Darendeliler 47 Progress of Anchorage in Lingual Orthodontic Treatment  489 Hee Moon Kyung 48 Biomechanics of Lingual Orthodontics and TADs  497 Ryoon-Ki Hong 49 TADs with a Fully Customized CAD-CAM Lingual Bracket System  513 Toru Inami 50 TAD-assisted Lingual Retractors  527 Ki-Ho Park, Hyo-Won Ahn, and Yoon-Goo Kang 51 TADs and Invisalign: Making Difficult Movement Possible  541 Joorok Park and Robert L. Boyd 52 The Use of TADs with Clear Aligners for Asymmetry Correction  555 William J. Kottemann 53 Microimplant-assisted Aligner Therapy  563 Ramon Mompell and S. Jay Bowman 54 Safe and Precise TAD Placement in the Anterior Palate with Simple and Inexpensive TAD Guides  577 Philipp Eigenwillig, Björn Ludwig, and Axel Bumann, Section IV  Esthetic Control with TADs  587 55 Correction of Occlusal Canting with TADs  589 Tae-Woo Kim 56 Treatment of Facial Asymmetry with Microimplants  603 Hyo-Sang Park 57 Facial Asymmetry: Non-surgical Orthodontic Treatment Considerations  615 Kelvin Wen-Chung Chang 58 The Application of TADs for Gummy Smile Correction  633 Kee-Joon Lee

Contents

59 Application of TADs in an Adult Gummy Smile Case with Vertical Maxillary Excess  647 Johnny J.L. Liaw 60 Facial Esthetics-oriented Treatment Planning with Dental VTOs and TADs  661 Sercan Akyalcin 61 Improved Facial Profile with Premolar Extraction and Molar Intrusion Using TADs and VTOs  675 Kiyoshi Tai and Jae Hyun Park Section V  Application of TADs in Surgical Cases  685 62 TADs vs. Orthognathic Surgery  687 Jeong‐Ho Choi 63 Advantages of Miniscrew Usage for Pre‐ and Post-operative Orthodontics in Skeletal Class III Malocclusion Patients  697 Seong Sik Kim and Sung‐Hun Kim 64 Orthodontic Biomechanics with Miniplates in the Surgery‐first Orthognathic Approach  709 Jorge Faber, Carolina Faber, and Patricia Valim Section VI  Complications with the Use of TADs  717 65 Biomechanical Mistakes Related to the Use of TADs  719 Ki Beom Kim and Guilherme Thiesen 66 Pros and Cons of Miniscrews and Miniplates for Orthodontic Treatment  731 Cheol‐Hyun Moon 67 Orthodontic Miniscrews: The Pearls and Pitfalls of TADs  739 Takashi Ono 68 Success with TADs: Evidence and Experience  747 Melih Motro and Leslie A. Will 69 Legal Considerations When Using TADs  757 Laurance Jerrold and Michael Schulte Index  765

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List of Contributors Hyo-Won Ahn, DDS, PhD Associate Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea Sercan Akyalcin, DDS, MS, PhD Associate Professor and Graduate Program Director Department of Orthodontics School of Dental Medicine Tufts University Boston, MA, USA Seung-Hak Baek, DDS, PhD Professor Department of Orthodontics School of Dentistry Seoul National University Seoul, South Korea Sebastian Baumgaertel, DMD, MSD, FRCD(C) Clinical Associate Professor Department of Orthodontics School of Dental Medicine Case Western Reserve University Cleveland, OH, USA Mohamed Bayome, BDS, MMS, PhD Assistant Professor Department of Preventive Dentistry College of Dentistry King Faisal University Al-hofuf, Saudi Arabia; and Department of Postgraduate Studies Universidad Autonóma del Paraguay Asunción, Paraguay S. Jay Bowman, DMD, MSD Adjunct Associate Professor Department of Orthodontics Center for Advanced Dental Education St. Louis University

St. Louis, MO; Instructor Department of Orthodontics School of Dentistry University of Michigan Ann Arbor, MI; and Private Practice Portage, MI, USA Robert L. Boyd, DDS, Med Professor Emeritus Department of Orthodontics Arthur A. Dugoni School of Dentistry University of the Pacific San Francisco, CA, USA Axel Bumann, DDS, PhD, Prof.Dr.Med.Dent. Associate Professor Department of Orthodontics Christian-Albrechts-University Kiel; and Private Practice Berlin, Germany Peter H. Buschang, PhD Regents Professor and Director of Orthodontic Research Department of Orthodontics Texas A&M University College of Dentistry Dallas, TX, USA Bong-Kuen Cha, DDS, MSD, Dr.Med.Dent. Professor Department of Orthodontics College of Dentistry Gangneung-Wonju National University Gangneung, South Korea Jung Yul Cha, DDS, MS, PhD Professor Department of Orthodontics

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Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea

Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea

Hwa Sung Chae, DDS, MSD, PhD Lecture Professor Department of Orthodontics Institute of Oral Health Science Ajou University School of Medicine Suwon, South Korea

Yoon Jeong Choi, DDS, MSD, PhD Associate Professor Department of Orthodontics Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea

Jong-Moon Chae, DDS, MSD, PhD Professor Department of Orthodontics School of Dentistry University of Wonkwang Wonkwang Dental Research Institute Iksan, South Korea; and Visiting Scholar Postgraduate Orthodontic Program Arizona School of Dentistry & Oral Health A.T. Still University Mesa, AZ, USA

Terpsithea Christou, DDS, MS, Cert(Ortho) Assistant Professor and Clinical Director Department of Orthodontics School of Dentistry University of Alabama at Birmingham Birmingham, AL, USA

Chris H. Chang, DDS, PhD Founder and President Beethoven Orthodontic Center Hsinchu, Taiwan Kelvin Wen-Chung Chang, DDS, MS Adjunct Clinical Instructor Division of Orthodontics and Dentofacial Orthopedics Department of Dentistry National Taiwan University Hospital Taipei, Taiwan Jing Chen, PhD, DDS Assistant Professor and Program Director Division of Orthodontics College of Dental Medicine Columbia University New York, NY, USA Jeong-Ho Choi, DDS, MSD, PhD Adjunct Associate Professor Department of Orthodontics School of Dentistry Seoul National University Seoul, South Korea Sung-Hwan Choi, DDS, MS, PhD Assistant Professor Department of Orthodontics

Dong-Hwa Chung, DDS, MS, PhD Professor and Chair Department of Orthodontics College of Dentistry Dankook University Cheonan, South Korea Kyu-Rhim Chung, DMD, MSD, PhD Clinical Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea G. Frans Currier, DDS, MSD, Med David Ross Boyd Professor and Head R.S. Nanda Endowed Chair Department of Developmental Dentistry Division of Orthodontics College of Dentistry University of Oklahoma HSC Oklahoma City, OK, USA M. Ali Darendeliler, BDS, PhD, Dip.Orth., Certif.Orth., Priv.Doc., MRACDS(Ortho), FICD Professor and Chair Discipline of Orthodontics and Pediatric Dentistry School of Dentistry Faculty of Medicine and Health University of Sydney, Sydney; and Head Department of Orthodontics Sydney Dental Hospital Sydney Local Health District Sydney, Australia

List of Contributors

Toru Deguchi, DDS, MSD, PhD Associate Professor and Graduate Program Director Division of Orthodontics College of Dentistry The Ohio State University Columbus, OH, USA Philipp Eigenwillig, Dr.Med.Dent. Private Practice Brandenburg an der Havel Germany Tarek El-Bialy, BDS, MSc, PhD, EMBA, DrMedDent Professor Division of Orthodontics Department of Biomedical Engineering Faculty of Medicine and Dentistry University of Alberta Edmonton, Canada Carolina Faber, DDS Private Practice Brasília, Brazil Jorge Faber, DDS, MS, PhD Professor Postgraduate Program in Dentistry University of Brasília, Brasília; and Private Practice Brasília, Brazil Hong He, DDS, MDS, PhD Professor Department of Orthodontics Hubei-MOST KLOS & KLOBM School & Hospital of Stomatology Wuhan University Wuhan, China Glen Hintz, MS Associate Professor Medical Illustration Program Director BFA Medical Illustration and Chairperson School of Art & School for American Crafts College of Art and Design Rochester Institute of Technology Rochester, NY, USA Ryoon-Ki Hong, DDS, PhD Adjunct Assistant Professor Department of Orthodontics College of Dentistry Seoul National University, Seoul; and

Chair Department of Orthodontics Chong-A Dental Hospital Seoul, South Korea Chung-Ju Hwang, DDS, MS, PhD Professor Department of Orthodontics Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea Toru Inami, DDS, PhD Clinical Professor Department of Orthodontics Aichi Gakuin University Nagoya; and Private Practice Kyoto, Japan Woowon Jang, DDS, MSD, PhD Clinical Assistant Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea Laurance Jerrold, DDS, JD Professor and Chair Program Director Orthodontic Residency Program NYU Langone Health Brooklyn, NY, USA Min-Ho Jung, DDS, MSD, PhD Adjunct Associate Professor Department of Orthodontics Dental Research Institute School of Dentistry Seoul National University Seoul; and Private Practice Seoul, South Korea Onur Kadioglu, DDS, MS Associate Professor and Program Director Graduate Alumni Endowed Chair Department of Developmental Dentistry Division of Orthodontics College of Dentistry University of Oklahoma HSC Oklahoma City, OK, USA

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Yoon-Goo Kang, DMD, MSD, PhD Associate professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea

Kyung-A Kim, BS, MSD, PhD Assistant Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea

Masato Kaku, DDS, PhD Professor Department of Anatomy and Functional Restorations Division of Oral Health Sciences Hiroshima University Graduate School of Biomedical Sciences Hiroshima, Japan

Kyung-Ho Kim, DDS, MSD, PhD Professor and Chair Department of Orthodontics Gangnam Severance Dental Hospital Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea

Chung H. Kau, BDS, MScD, MBA, PhD, FDSGlas, MOrthEdin, FFDIre, FAMS, FICD, FDSEdin, Cert(Ortho) Professor and Chair Department of Orthodontics School of Dentistry University of Alabama at Birmingham Birmingham, AL, USA

Seong-Hun Kim, DMD, MSD, PhD Professor and Head Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea

Do-Gyoon Kim, PhD Associate Professor Division of Orthodontics College of Dentistry The Ohio State University Columbus, OH, USA Hwee-Ho Kim, DDS, MSD Clinical Fellow Department of Orthodontics Asan Medical Center College of Medicine University of Ulsan Seoul; and Clinical Faculty Department of Orthodontics College of Dentistry Dankook University Cheonan, South Korea Ki Beom Kim, DDS, MSD, PhD Lysle E. Johnston Jr. Endowed Chair in Orthodontics Associate Professor and Program Director Department of Orthodontics Center for Advanced Dental Education Saint Louis University St. Louis, MO, USA

Seong Sik Kim, DDS, MSD, PhD Professor Department of Orthodontics School of Dentistry Pusan National University Yangsan, South Korea Su-Jung Kim, DMD, MSD, PhD Professor and Chair Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea Sung-Hun Kim, DDS, MSD, PhD Clinical Professor Department of Orthodontics School of Dentistry Pusan National University Yangsan, South Korea Tae-Woo Kim, DDS, MSD, PhD Professor Department of Orthodontics School of Dentistry Seoul National University Seoul, South Korea

List of Contributors

Young Ho Kim, DDS, MS, PhD Dean Graduate School of Clinical Dentistry Ajou University, Suwon; Director Ajou University Dental Hospital Suwon; and Professor and Chair Department of Orthodontics Institute of Oral Health Science Ajou University School of Medicine Suwon, South Korea Karolina Kister, PhD, DDS Postdoctoral Fellow Division of Orthodontics College of Dental Medicine Columbia University New York NY, USA Ching-Chang Ko, DDS, MS, PhD Distinguished Professor and Chair Division of Craniofacial and Surgical Science Adams School of Dentistry University of North Carolina NC, USA Yoon-Ah Kook, DDS, PhD Professor Department of Orthodontics Seoul St. Mary’s Hospital The Catholic University of Korea Seoul, South Korea William J. Kottemann, DDS, MS Private Practice Minneapolis, MN, USA Budi Kusnoto, DDS, MS Professor Program and Clinic Director Department of Orthodontics College of Dentistry University of Illinois at Chicago Chicago, IL, USA Hee Moon Kyung, DDS, MS, PhD Dean Emeritus and Professor Department of Orthodontics

School of Dentistry Kyungpook National University Daegu, South Korea Gye-Hyeong Lee, DDS, MSD, PhD Attending Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul; Attending Professor Department of Orthodontics School of Dentistry Chonnam National University Gwangju; and Private Practice Yeosu, South Korea Ju Young Lee, DDS, MSD, PhD Clinical Professor Department of Orthodontics Institute of Oral Health Science Ajou University School of Medicine Suwon, South Korea Kee-Joon Lee, DDS, MS, PhD Professor and Chair Department of Orthodontics Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea Kyung-Min Lee, DDS, MSD, PhD Associate Professor Department of Orthodontics School of Dentistry Chonnam National University Gwangju, South Korea Sang-Mi Lee, DDS, MSD, PhD Adjunct professor Department of Orthodontics School of Dentistry Chonnam National University Gwangju; The Catholic University of Korea Seoul; and Private Practice Goyang, South Korea

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Johnny J.L. Liaw, DDS, MS Adjunct Clinical Instructor Orthodontic Division Dental Department National Taiwan University Hospital Taipei, Taiwan Sung-Hoon Lim, DDS, MSD, PhD Professor and Chair Department of Orthodontics College of Dentistry Chosun University Gwangju, South Korea Joshua S. Lin, DDS Associate Director Beethoven Orthodontic Center Hsinchu, Taiwan Björn Ludwig, Dr.Med.Dent. Private Practice Traben Trarbach Germany Mohamed I. Masoud, BDS, DMSc Assistant Professor Director of Advanced Graduate Education in Orthodontics Department of Developmental Biology Harvard School of Dental Medicine Boston, MA, USA Dimitrios Michelogiannakis, DDS, MS Assistant Professor Division of Orthodontics and Dentofacial Orthopedics Eastman Institute for Oral Health University of Rochester Rochester, NY, USA Ramon Mompell, DDS, MS Researcher Division of Growth and Development Section of Orthodontics School of Dentistry Center for Health Science University of California Los Angeles Los Angeles, CA, USA; and Private Practice Madrid, Spain Cheol-Hyun Moon, DMD, MSD, PhD Professor and Chair Department of Orthodontics Gil Medical Center Gachon University College of Medicine Incheon, South Korea

Won Moon, DMD, MS Associate Professor and Thomas R. Bales Endowed Chair in Orthodontics Section of Orthodontics School of Dentistry University of California, Los Angeles CA, USA Mitsuru Motoyoshi, DDS, PhD Professor and Chair Department of Orthodontics Nihon University School of Dentistry Tokyo, Japan Melih Motro, DDS, PhD Clinical Associate Professor Department of Orthodontics Henry M. Goldman School of Dental Medicine Boston University Boston, MA, USA Gerald Nelson, DDS Professor Emeritus Division of Orthodontics Department of Orofacial Science University of California, San Francisco, CA, USA Peter Ngan, DMD Professor and Chair Department of Orthodontics School of Dentistry West Virginia University Morgantown, WV, USA Tung Nguyen, DMD, MS Associate Professor Division of Craniofacial and Surgical Science Adams School of Dentistry University of North Carolina NC, USA Min-Ki Noh, DMD, MSD, PhD Clinical Assistant Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea Takashi Ono, DDS, PhD Professor and Chair Department of Orthodontic Science Graduate School of Medical and Dental Sciences Tokyo Medical and Dental University Tokyo, Japan

List of Contributors

Cheol-Ho Paik, DDS, PhD Clinical Associate Professor Department of Orthodontics College of Dentistry Seoul National University Seoul; and Private Practice Seoul, South Korea Moschos A. Papadopoulos, DDS, Dr.Med.Dent. Professor Head and Program Director Department of Orthodontics School of Dentistry Aristotle University of Thessaloniki Thessaloniki, Greece Hyo-Sang Park, DDS, MSD, PhD Professor and Chair Department of Orthodontics School of Dentistry Kyungpook National University Daegu, South Korea Jae Hyun Park, DMD, MSD, MS, PhD Professor and Chair Postgraduate Orthodontic Program Arizona School of Dentistry & Oral Health A.T. Still University Mesa, AZ, USA; and International Scholar Graduate School of Dentistry Kyung Hee University Seoul, South Korea Joorok Park, DMD, MSD Assistant Professor Department of Orthodontics Arthur A. Dugoni School of Dentistry University of the Pacific San Francisco, CA, USA Ki-Ho Park, DMD, MSD, PhD Associate Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea Young-Chel Park, DDS, MSD, PhD Dean Emeritus Professor Emeritus Department of Orthodontics Institute of Craniofacial Deformity

Yonsei University College of Dentistry Seoul, South Korea Young-Guk Park, DMD, MSD, PhD, MBA, FICD Provost Kyung Hee University Seoul; and Professor Department of Orthodontics School of Dentistry Kyung Hee University Seoul, South Korea Goli K. Parsi, DDS, DScD Clinical Associate Professor Department of Orthodontics Henry M. Goldman School of Dental Medicine Boston University Boston MA, USA W. Eugene Roberts, DDS, PhD, DHC (Med) Professor Emeritus of Orthodontics and Adjunct Professor of Mechanical Engineering Indiana University – Purdue University Indianapolis, IN; Adjunct Professor of Orthodontics Loma Linda University Loma Linda, CA; and St. Louis University St. Louis, MO, USA Marcio Rodrigues de Almeida, DDS, MSc, PhD Professor Department of Orthodontics University of Northern Paraná Londrina-Paraná, Brazil Alejandro A. Romero-Delmastro, DDS, MS Clinical Assistant Professor Department of Developmental Dentistry Division of Orthodontics College of Dentistry University of Oklahoma HSC Oklahoma City, OK, USA P. Emile Rossouw, BSc, BChD (Dent), BChD (Hons-Child Dent), MChD(Ortho), PhD, FRCD(C) Professor and Chair Division of Orthodontics and Dentofacial Orthopedics Eastman Institute for Oral Health University of Rochester Rochester, NY, USA

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Michael Schulte DDS, PhD Private Practice Camdenton, MO, USA Kyungsup Shin, MS, PhD, DMD, MS Assistant Professor and Graduate Program Director Department of Orthodontics College of Dentistry and Dental Clinics University of Iowa Iowa City, IA, USA Sang-Jin Sung, DDS, MS, PhD Professor Department of Orthodontics Asan Medical Center College of Medicine University of Ulsan Seoul, South Korea Larry Tadlock, DDS, MS Clinical Associate Professor Head and Program Director Department of Orthodontics Texas A&M University College of Dentistry Dallas, TX, USA Kiyoshi Tai, DDS, PhD Visiting Adjunct Professor Postgraduate Orthodontic Program Arizona School of Dentistry & Oral Health A.T. Still University Mesa, AZ, USA; and Private Practice Okayama, Japan Masamitsu Takahashi, D.D.S., Ph.D. Part-time Lecturer Department of Orthodontics Nihon University School of Dentistry Tokyo; and Private Practice Tokyo, Japan Kazuo Tanne, DDS, PhD Professor Emeritus and Visiting Professor Department of Orthodontics and Craniofacial Developmental Biology Hiroshima University Graduate School of Biomedical and Health Sciences Hiroshima, Japan

Kotaro Tanimoto, DDS, PhD Professor and Chair Department of Orthodontics and Craniofacial Developmental Biology Hiroshima University Graduate School of Biomedical and Health Sciences Hiroshima, Japan Nour Eldin Tarraf, BDS(Hons), MDSc(Hons), MRACDs(Ortho), MOrthRCSEd PhD Candidate Discipline of Orthodontics and Pediatric Dentistry School of Dentistry Faculty of Medicine and Health University of Sydney, Sydney; and Private Practice Sydney, Australia Guilherme Thiesen, DDS, MSD, PhD Post-Doctoral Fellow Department of Orthodontics Center for Advanced Dental Education Saint Louis University St. Louis, MO, USA; and Private Practice Florianópolis, SC, Brazil Flavio Uribe, DDS, MDentSc Associate Professor Program Director and Interim Chair, Charles Burstone Professor Division of Orthodontics Department of Craniofacial Sciences School of Dental Medicine University of Connecticut Farmington, CT, USA Satoshi Uzuka, DDS, PhD Associate Professor and Chair Division of Orthodontics The Nippon Dental University Hospital Tokyo, Japan Patricia Valim, DDS, MS Private Practice Brasília, Brazil Carlos Villegas, DDS Associate Professor Department of Orthodontics, CES University Medellin, Colombia; and Visiting Professor Alexandria University Alexandria; Egypt

List of Contributors

Sunil Wadhwa, DDS, PhD Leuman M. Waugh DDS Associate Professor and Director Division of Orthodontics College of Dental Medicine Columbia University New York, NY, USA Keiichiro Watanabe, DDS, PhD Assistant Professor Department of Orthodontics and Dentofacial Orthopedics Graduate School of Biomedical Sciences Tokushima University Tokushima, Japan; and Division of Orthodontics College of Dentistry The Ohio State University Columbus, OH, USA Leslie A. Will, DMD, MSD Anthony A. Gianelly Professor and Chair Department of Orthodontics Henry M. Goldman School of Dental Medicine Boston University Boston, MA, USA

Tai-Hsien Wu, MS, PhD Postdoctoral Fellow Division of Craniofacial and Surgical Science Adams School of Dentistry University of North Carolina NC, USA Hsin-Yin Yeh, DDS, MSD Director Beethoven Orthodontic Center Hsinchu, Taiwan Hyung Seog Yu, DDS, MS, PhD Professor Department of Orthodontics Institute of Craniofacial Deformity Yonsei University College of Dentistry Seoul, South Korea Sun Kyong Yoo, DMD International Orthodontic fellow Postgraduate Orthodontic Program Arizona School of Dentistry & Oral Health A.T. Still University Mesa, AZ, USA; and Private Practice Bundang, South Korea

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Foreword It is a true pleasure to be able to write the foreword for this monumental textbook on temporary anchorage devices (TADs) because it is important and timely. Orthodontic implants have been around for about three decades now. In the early days, the potential uses for TADs in clinical orthodontics was just an intriguing idea. Since the early days, interest in implants has increased tremendously, the science surrounding implants has grown massively, and, in parallel, clinical innovations involving TADS have exploded in numbers. When TADs were initially introduced into the specialty of orthodontics, they were used primarily as a source of temporary “absolute” anchorage to perform limited types of tooth movement, design elements seemed crucial and varied tremendously, placement sites seemed limited to the interradicular and midpalatal areas, and failure rates were a significant concern. However, as time passed, practitioners started to apply TADs creatively in various ways to treat many usual and then challenging clinical situations. As a result, they have become one of the most essential tools in contemporary orthodontics because they provide solutions for conventionally difficult tooth movements, thus allowing greater orthodontic efficiency and effectiveness. During the past 20 years, there has been tremendous growth in the quantity and quality of publications that explore the basic and applied sciences attendant to TADs. This suggests that interest in TADs remains high and it is prudent and timely to take stock of what is known at the present time via a well-organized textbook. We are fortunate indeed that Dr. Jae Hyun Park has accomplished that task by producing this textbook. It is a huge book; it is a wonderful book; is a book overflowing with ideas, knowledge, and experience; and it is an ambitious book that can be used to address many problems. Dr. Park is recognized both nationally and internationally as a speaker, author, editor, clinician, and educator. With regard to TADs, he is one of the most prolific authors of articles on the topic. He is definitely a very suitable person for this task and he probably could have written a book on TADs all by himself, but he did not. Drawing upon his

wide-ranging international perspectives, affiliations, and relationships, he has amassed the thoughts and experiences of more than 100 outstanding authors from all over the world. The breadth and depth of the authors is a strong aspect of this book. The authors are knowledgeable clinicians and academics. Their names are associated with high-quality case reports and clinical research that appear in peerreviewed journals and important textbooks. They are pioneers, innovators, inventors, researchers, and masterful orthodontists. The book contains 69 chapters arranged into six sections: fundamental perspectives, three-dimensional corrections, clinical applications, esthetic control, surgery cases, and complications. You will not be able to read this textbook all at once, but that is not a drawback at all. You need time to think and consider how all this information fits nicely together and how it might be applied. The book begins strongly with information on the related biology, anatomy, biomaterials, and biomechanics among other topics. What follows contains pertinent information on diagnosis and treatment planning and then a voluminous amount of clinical material. Applications in orthodontics, orthopedics, and orthognathics are presented as applied to many types of malocclusions, many types of appliances (some of which are new), and many types of treatment strategies. It is interesting that the book also contains tips on how to deal with complications and failures as well as legal considerations. As a strength, both theoretical and practical information is supplied in balance. Similarly, a nice blend of basic and advanced clinical information exists that the contemporary orthodontist should be able to incorporate TADs into practice at any level. Successful treatment protocols and strategies are presented very well; this is particularly useful in treating difficult cases. The case reports are outstanding and the illustrations excellent. In the end, I was drawn to one whole section of the book that deals with esthetics. The reason that implants are intriguing and important to orthodontics is that they solve

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problems heretofore thought difficult, if not impossible, to correct. This section presents information on midline deviations, occlusal cants, facial asymmetry, gummy smiles, and unfavorable facial profiles. Fortunately, solutions to these problems using TADs are offered by the authors. If you could only have one book on TADs for your reference and consideration, this is the book you need. If you are a student, this should be an essential textbook. If you are a clinician this is the most up-to-date book on TADs; judiciously employing the information within will allow you to achieve more control than was possible in the past, allow you to be less reliant on patient compliance, and

achieve better, more predictable results than has been ­possible in the past. TADs are like magic and we thank Dr. Park and his team of magicians for presenting information about their magic tool box. Information contained therein is sufficient to enable practitioners to perform magic in remarkable ways that extends their abilities, the scope of their ministrations, and the quality of results that they obtain. March 2020  Rolf G. Behrents, DDS, MS, PhD, PhD (Hon) Editor-in-Chief, American Journal of Orthodontics & Dentofacial Orthopedics

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Preface shrek:  Ogres are like onions. donkey:  They stink? shrek:  Yes. No. donkey:  Oh, they make you cry. shrek:  No. donkey:  Oh, you leave em out in the sun, they get all brown, start sproutin’ little white hairs. shrek:  No. Layers. Onions have layers. Ogres have layers. Onions have layers. You get it? We both have layers. donkey:  Oh, you both have layers. Oh. You know, not everybody like onions. (From Shrek, a DreamWorks animation) There can be little argument that a phenomenal paradigm shift has occurred in the field of orthodontics with the introduction of temporary anchorage devices (TADs) over the past decade. TADs have not only allowed orthodontists to reliably control anchorage and relieve the issues of patient compliance, but they have also allowed for controlled movement of teeth in all three dimensions. Facilitation of these movements have led to the development of successful treatment protocols for various difficult cases and produced treatment results that were not considered possible with orthodontics alone in the past. In an effort to demystify this new “ogre” in the field of orthodontics, a huge number of scientific and clinical articles have been published in peer‐reviewed articles since the introduction of TADs in the late 1990s by pioneers from Asian countries. Dental students and orthodontic residents, clinicians, and educators have felt the need for a more comprehensive and up‐to‐date textbook that can be used to comprehend and apply TADs in everyday practice. This was mainly because orthodontic TADs have been one of the fastest growing areas of modern clinical orthodontics in terms of concept and technology, not to mention the sheer volume of clinical applications. Since 2012, more than 2000 scientific articles have been published with the keywords “orthodontic miniscrew implant” and various new approaches have been introduced. Moreover,

since  2008, I have personally co‐authored more than 200 peer‐reviewed articles on related subjects, including cone‐ beam computed tomography, so I have felt a strong need for a new textbook with the most current clinical guidance and background information to help educate current and future orthodontic trainees and educators as well as practitioners globally. This book is an introduction to TADs and includes information about diagnosis and treatment planning, clinical applications, new appliances, and case reports on the use of TAD systems to achieve the best clinical outcomes while minimizing clinical failures. Being a by‐product of collaboration with around 113 contributors from around the world who are professors or clinicians deeply involved in writing peer‐reviewed journals and performing clinical researches regarding TADs, this textbook will also be translated into other languages. You can consider it as an international buffet of the most up‐to‐date knowledge of and experience with TADs! Although it is certain that more layers of TADs are yet to be unfolded through continued progression in research and application of TADs by many brilliant practitioners, I hope this textbook will help demystify the fear of TADs and thereby promote a greater use of TADs in daily practice.

O ­ rganization Section I: Fundamental Perspectives on TADs: This section contains an overview and the basic principles of TAD usage in orthodontics. It includes an in‐depth discussion of f­ undamental topics such as biomaterials, biomechanics, and histological and anatomical considerations as well as clinical topics such as diagnosis, treatment planning, and site selection for greater success with TADs. Section II: Three‐dimensional Correction with TADs: This section discusses different orthodontic tooth movements in all three dimensions (sagittal, transverse, and ­vertical) that are now possible with the help of TADs.

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Preface

Section III: Clinical Applications of TADs: The integration of TADs into various types of clinical orthodontics are explained in this section. Some examples are the utilization of TADs to replace missing teeth and to support limited or adjunctive orthodontic treatment, lingual orthodontics, and clear aligner therapy. Section IV: Esthetic Control with TADs: This section describes TAD‐related techniques to enhance esthetic concerns such as midline deviation, canting of occlusal planes, facial asymmetry, gummy smiles, and unsatisfactory facial profiles. Section V: Application of TADs in Surgical Cases: This section discusses the role of TADs in surgical cases. Section VI: Complications with the Use of TADs: This section explains common complications and concerns regarding TADs that dental professionals should be aware of, including legal considerations.

­Tips for the Reader Within each section, each chapter is organized in such a way that you can capture a good overview of the topics at the beginning and then gradually gain deeper understanding as you read on. Chapters that seem to complement each

other are referenced within the text so readers can easily go back and forth between them as they wish. Therefore, if there are any unclarified questions from one chapter, you can expect to find more answers in other chapters of the same section or in correlating chapters of other sections. While many cases presented in this book may seem repetitive/redundant, it was intentionally structured to include all possible alternatives for a given clinical situation as used and researched by different experts from around the world. This will keep you covered in case one method fails. Lastly, please be advised that different writers have used different terminologies for the word “TAD,” such as ­orthodontic mini‐implant, miniscrew, miniscrew implant, microimplant, or temporary skeletal anchorage devices. Although there seems to be a good consensus among ­academicians that “temporary skeletal anchorage device” is the most correct terminology, I have chosen to use the well‐known terminology “TAD” in the book title due to its popularity. Within the text itself, however, various terminologies have been left in place in an effort to respect the individual contributor’s opinion regarding what these orthodontic devices should be called. Understand that, practically speaking, it was nearly impossible to come to a consensus on the terminology with over 100 authors.

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Acknowledgements I have had such a humbling experience working with my respected authors, the leading pioneers in contemporary orthodontics. I would like to express my sincerest appreciation to each one of them for patiently working with me to meet deadlines while striving to include all of the best state‐ of‐the‐art TAD‐related techniques. I was also blessed to have a dedicated team of eminent reviewers who have worked very hard to structure, organize, and edit the contents. Each chapter has been reviewed and revised several times by reviewers such as Xingzhong (John) Zhang (DDS, MSD, PhD), Jun Sik Kim (DDS, MS, PhD, MS), Kyungsup Shin (MS, PhD, DMD, MS) and Janet Hojung Kim (DDS). My heartfelt gratitude to all of these reviewers. I would also like to extend my sincere gratitude to Dr. Kyungsup Shin for helping me with the project’s development, Mr.  Wayne Kendall for his assistance in professional ­editing of the text, and Dr. Sun Kyong Yoo for professional editing of the images. The publisher, Wiley, has made this book possible by taking up the mission and helping me to publish it. Special

thanks to Ms. Jayadivya Saiprasad and the entire Wiley ­editorial team for their endless support and help. And last, but not least, I would like to express heartfelt thanks to my dear wife Jennifer, and to my son Steven, and my parents and sisters for the support and trust they have given me. I would also like to thank the executive administration, Dean Robert Trombly, and the entire team at A.T. Still University’s Arizona School of Dentistry & Oral Health and the marvelous folks in the Postgraduate Orthodontic Program for their endless support in the publication of this book and many other projects with which I am affiliated both internally and externally. I also would like to express my sincere gratitude to Provost Young-Guk Park, Professor Je-Won Shin, and Dean Kung-Rock Kwon at Kyung Hee University for their tireless support and help in making the publication of this book a success. I hope our endeavors will greatly benefit our readers and their patients today and for years to come.

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­About the Editor

Jae Hyun Park, DMD, MSD, MS, PhD

Dr. Jae Hyun Park is Professor and Chair of the Postgraduate Orthodontic Program at the Arizona School of Dentistry & Oral Health. He is a Diplomate of and Examiner for the American Board of Orthodontics. Dr. Park has received several awards for scientific and clinical excellence including the Charley Schultz Award (1st Place Winner in the Scientific Category at the Orthodontic Resident Scholars Program) and the Joseph E. Johnson Award (1st Place Winner at the Table Clinic Competition)

from the American Association of Orthodontists (AAO). He also serves as an editorial board member of several peer‐reviewed orthodontic and dental journals including The Angle Orthodontist, Seminars in Orthodontics, and Journal of Clinical Orthodontics (JCO) as well as associate editor of the American Journal of Orthodontics & Dentofacial Orthopedics (AJO‐DO), Orthodontics & Craniofacial Research, World Federation of Orthodontists, and Journal of Clinical Pediatric Dentistry. He was recently invited to be a guest editor of Seminars in Orthodontics. While working as a full‐time faculty member since 2008, he has published more than 230 scientific and clinical articles in peer‐reviewed orthodontic and dental journals including five cover pages in the AJO‐DO, three cover pages in the JCO, two books, and 22 book chapters. He lectures nationally and internationally and represented the AAO at the 2018 American Dental Association Annual Session where he presented a three‐ hour lecture. Dr. Park is currently Editor‐in‐Chief of the Journal of the Pacific Coast Society of Orthodontists (PCSO) Bulletin, Past President of the Arizona State Orthodontic Association, and Thesis Committee Co‐ Chair of Northern California Edward H. Angle Society of Orthodontists. He also works for the National Board Dental Examination Part II Ortho‐Pediatric Dentistry/ Advanced Dental Admission Test Construction Committee and Commission on Dental Accreditation Site Visitor. Recently, he was also appointed to the  2021 Scientific Program Chair at the College of Diplomates of the American Board of Orthodontics annual meeting. In addition, he was recently appointed to replace Dr. Steven Dugoni as the American Board of Orthodontics (ABO) Director representing the PCSO. He will be the ABO President in 2024.

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Section I Fundamental Perspectives on TADs

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1 An Overview of Clinical Applications for Temporary Anchorage Devices (TADs) Jae Hyun Park1,2 and Kyungsup Shin3 1

Postgraduate Orthodontic Program, Arizona School of Dentistry & Oral Health, A.T. Still University, Mesa, AZ, USA Graduate School of Dentistry, Kyung Hee University, Seoul, South Korea 3 Department of Orthodontics, College of Dentistry and Dental Clinics, University of Iowa, Iowa City, IA, USA 2

The advent of temporary anchorage devices (TADs) has enabled orthodontic clinicians to accomplish profound clinical solutions that were previously deemed inconceivable with traditional anchorage modalities. Orthodontic applications with TADs have come a long way since 1983 when the first clinical case demonstrated the possibility of “absolute” anchorage control in humans [1]. Various types of complex and challenging malocclusions can now be successfully treated using TADs. This chapter outlines some contemporary clinical applications for TADs to treat various orthodontic problems. The progress in TAD‐ related research and potential future directions for TADs are briefly discussed.

1.1  ­Corrections in the Anteroposterior Dimension The use of TADs is a compliance‐free alternative to traditional forms of anchorage control in orthodontic treatment. Of the three dimensions, TADs have been used most frequently to correct problems in the anteroposterior dimension. Typical treatment objectives include mesialization or distalization of a single tooth, multiple teeth, or maxillary/mandibular total arches.

1.1.1  Comparison with Conventional Methods for Anchorage Reinforcement in the Anteroposterior Dimension A number of studies have evaluated treatment outcomes with TADs and compared them to conventional methods  such as headgear, Nance appliances, reverse pull

headgear, and various distalizers [2–5]. Recently, a systematic review and meta‐analysis was reported that evaluated the treatment effectiveness of intraoral TADs and headgear for en‐masse retraction after premolar extractions [2]. In a review of 14 articles and 616 patients, TADs effectively enabled 1.86 mm more anchorage preservation by limiting mesial movement of maxillary first molars than did conventional methods using various types of headgear. A randomized clinical trial compared the effectiveness of three different methods including TADs, Nance appliances, and headgear [3]. In terms of maximum anchorage, there were no significant outcome differences in effectiveness for the three groups. The authors found, however, that patients had a superior comfort level with TADs and Nance appliances than with headgear. Patients also reported fewer problems with TADs than with either of the other two groups. A retrospective study compared orthodontic tooth movement after treating adult patients with maxillary dentoalveolar protrusion using TADs vs. headgear [4]. The authors highlighted the superior treatment outcomes with TADs compared to headgear in terms of greater maxillary ­anterior tooth retraction, less maxillary molar mesial drift, and shorter treatment time. A meta‐analysis ­compared the treatment effects of distalizers between TAD‐­supported pendulum appliances and conventional distalizers, such as pendulum appliances with Nance buttons [5]. Based on six studies, this meta‐analysis showed a higher average molar distraction using TADs (5.1 mm), which was significantly longer than that found with conventional appliances (3.3 mm). Also, premolar distalization averaged 4.0 mm with skeletal anchorage in contrast to 2.3 mm with conventional methods.

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section I  Fundamental Perspectives on TADs

1.1.2  Functional Appliances and Auxiliaries Combined with TADs The introduction of TADs into orthodontics not only enables effective anchorage reinforcement with individual TADs, but also enhances the functionality of conventional orthodontic appliances when they are combined with TADs. For example, pendulum appliances anchored to the maxillary bone with TADs have achieved a similar amount of maxillary molar distalization to that of conventional pendulum appliances without TADs, providing significant premolar distalization in potentially less total treatment time and without the problem of anchorage loss [6]. For correction of Class III malocclusion with dental midline discrepancy, TADs can be used with sliding jigs (Figure  1.1) [7]. TAD‐supported Herbst appliances have significantly reduced unfavorable adverse treatment effects such as mandibular incisor proclination [8]. Placing a miniplate on the infrazygomatic buttress and linking it to the outer bow of a facemask has allowed protraction of the maxilla without any undesirable tooth movement that might cause unwanted arch length loss [9]. As an esthetic and simplified treatment option, a double J‐hook retractor and palatal TADs can  be used to close extraction spaces by retracting the

maxillary anterior segment [10]. The use of a double J‐hook significantly reduced treatment time with the fixed appliances. Therefore, this might be a viable treatment option for patients who are reluctant to use conventional fixed appliances (Figure 1.2).

1.1.3  Miniplates Combined with TADs Orthodontic miniplate anchorage systems have been used for various clinical applications. They are attractive options since they are independent of proximity to adjacent teeth and interradicular space limitations. In addition, since miniplates can withstand heavier forces than individual TADs, they have been used for rigorous orthodontic tooth movement such as total arch distalization. Total arch distalization with a palatal anchorage plate, when combined with tooth extractions, may be a feasible treatment option to achieve better facial esthetics without orthognathic surgery. This approach has been used as a successful non‐surgical correction of Class I malocclusion with severely protrusive soft tissue profiles by extracting four first premolars and applying total arch distalization (Figure 1.3) [11]. After making a series of modifications, these palatal miniplates have demonstrated successful

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Figure 1.1  Class III correction with TADs and sliding jigs [7]. (a) Initial examination indicated full-step Class III canine and molar relationships. (b) TADs were placed and connected with a sliding jig. (c) Schematic illustration shows a miniscrew-anchored sliding jig and the direction of the force. (d) Final examination indicated Class I canine and molar relationships. Source: Tai et al. [7]. Reprinted with permission from Elsevier.

Chapter 1  An Overview of Clinical Applications for TADs

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Figure 1.2  Class II correction with a double J retractor [10]. (a) Initial examination indicated a Class II Division 1 malocclusion with anterior crowding. (b) Schematic illustration shows a double J retractor and palatal TADs: palatal TADs (1, 2); anterior lever arm hooks (3); posterior lever arm hooks (4). (c) A double J retractor was connected to the TADs with elastomeric chains to achieve bodily translation. (d) Anterior tooth tipping can be controlled by adjusting the extension line of the force. (e) Maxillary anterior teeth were retracted and the extraction spaces were completely closed. (f) Maxillary anterior teeth were retracted and slightly tipped lingually. (g) Maxillary incisors were retracted after treatment. Source: Park et al. [10]. Reprinted with permission from Elsevier.

treatment outcomes with Class II malocclusion cases treated without extraction or severe bimaxillary protrusion with maxillary first premolar extractions [12, 13]. These palatal miniplates also demonstrated advantages when controlling distal tipping of the maxillary posterior teeth during distalization. A comparison study provided quantitative evidence that the palatal anchorage plate provided greater distalization and intrusion with less distal tipping of the first molar compared to conventional buccal TADs (Figure 1.4a–c) [14]. A recent follow‐up study evaluated the relationship between the amount of maxillary arch distalization with palatal anchorage plates and changes in the airway space. Whether the cases were treated with premolar extraction (3.4 mm of the maxillary first molar distalization) or with

non‐extraction (3.2 mm of the maxillary first molar distalization), there were no significant changes in airway volume or minimum cross‐sectional area of the oropharynx after maxillary arch distalization (Figure  1.4d) [15]. Miniplates have been placed on mandibular bodies to treat Class III malocclusions [16]. More recently, ramal plates have been placed in the retromolar fossa as a novel approach for retracting mandibular teeth or distalizing the mandibular total arch (Figure  1.5) [17, 18]. A finite element analysis (FEA) study verified that mandibular arch distalization with a ramal plate leads to greater distal and extrusive displacement of the posterior teeth and changes counterclockwise rotation of the occlusal plane compared to the same tooth movement using TADs in the buccal shelf or interradicular regions (Figure 1.5c) [19].

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Section I  Fundamental Perspectives on TADs

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Figure 1.3  Class I correction with a palatal plate and TADs [11, 13]. (a) Initial examination indicated Class I malocclusion with the proclined maxillary incisors and protrusive lips. (b) A palatal anchorage plate was placed. (c) Retractive force direction can be controlled by engaging elastomeric chains at different levels of the hooks. (d) The mandibular arch was retracted using Class III elastics. (e) Maxillary and mandibular anterior teeth were retracted. Facial harmony and lip support were significantly improved. Source: Kook et al. [11]. Reprinted with permission from Elsevier.

1.2  ­Corrections in the Vertical Dimension 1.2.1  Treatment for Dental and Skeletal Open Bite A moderate to severe dental open bite, often in conjunction with a skeletal open bite, is regarded as one of the most challenging orthodontic problems to correct. The main applications of TADs for correcting anterior open bite are either intrusion of the posterior teeth or extrusion of the anterior teeth. For molar intrusion, TADs have been placed in various anatomical sites [20–22].

For open bite correction, TADs can be combined with a transpalatal arch (TPA) to provide efficient maxillary posterior tooth intrusion along with tongue exercise (Figure  1.6) [20]. Anterior open bite also can be corrected with TADs and miniplates (Figure  1.7) [21]. Miniplates were placed bilaterally in the zygomatic arch and the mandibular molar regions to provide absolute anchorage for bimaxillary molar intrusion. This approach can not only treat dentoskeletal open bite with positive overbite but can also achieve a counterclockwise rotation of the mandible. In lingual orthodontics, palatal

Chapter 1  An Overview of Clinical Applications for TADs

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Figure 1.4  Comparison between a palatal anchorage plate and buccal TADs [14, 15]. (a) A palatal anchorage plate was placed for maxillary total arch distalization. (b) TADs were placed on the buccal side of the posterior teeth. (c) The palatal anchorage plate group showed greater distalization and greater intrusion with less distal tipping of the maxillary first molar and more extrusion of the maxillary incisor than the buccal TAD group. (d) No significant changes were found in the airway volume or minimum cross-sectional area of the oropharynx after treatment with these two groups.

TADs can be used to retract the anterior dentition and intrude the posterior dentition to correct anterior open bite (Figure 1.8) [22]. One advantage of this modality is that the proclination and intrusion of the maxillary anterior teeth can be controlled by adjusting the length of the crimpable hooks and the vertical locations of the palatal TADs (Figure 1.8c).

1.2.2  Treatment for Dental and Skeletal Deep Bite Conventional modalities for incisal intrusion have relied on archwire mechanics. These traditional methods, however, often have the undesirable effect of labial torqueing the maxillary incisors. The introduction of TADs as an anchorage has made the complex tooth movement of

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Section I  Fundamental Perspectives on TADs

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Figure 1.5  Skeletal Class III correction with a ramal plate [17, 19]. (a) The ramal plate was located on the retromolar fossa. (b) The plate was surgically fixated with two screws and the hook extended out of the mucosa. An elastic chain was tied for mandibular total arch distalization. (c) There was greater distal and extrusive displacement of the posterior teeth with ramal plate than with buccal shelf or interradicular TADs. (d) Initial examination indicated Class III malocclusion with lateral open bite. (e) CBCT superimposition shows the magnitude of molar distalization. (f) Final examination indicated Class I canine and molar relationships. Source: Kook et al. [17]. Reprinted with permission from Elsevier.

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Figure 1.6  Anterior open bite correction with TADs and a TPA [20]. (a) Initial examination indicated Class II malocclusion with anterior open bite. (b) TADs were placed on the buccal side of the maxillary first molars. Buccoversion of the posterior teeth was prevented by placing a modified TPA. (c) Optimal overbite was achieved after the maxillary first premolars and one mandibular central incisor were extracted. (d) Facial esthetic harmony was achieved. (e) Intrusion of the maxillary posterior teeth and retraction of the maxillary anterior teeth contributed to an improved overbite. Source: Park et al. [20]. Reprinted with permission from Elsevier.

Chapter 1  An Overview of Clinical Applications for TADs

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Figure 1.7  Anterior open bite correction with TADs, miniplates, and a TPA [21]. (a) Initial examination indicated anterior open bite. (b) Extended arms from the TPA were connected to the buttons bonded on the palatal side of the maxillary premolars with elastomeric chains for intrusion. (c) Positive overbite was achieved after treatment. (d) During the treatment, miniplates were surgically placed on the infrazygomatic buttresses and mandible for intrusion of the posterior teeth. (e) Optimal overbite was achieved and the interincisal angle was increased. Source: Park et al. [21]. Reprinted with permission.

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Figure 1.8  Anterior open bite correction with TADs and maxillary lingual appliance [22]. (a) Initial examination indicated anterior open bite. (b) Lingual appliance with crimpable hooks were bonded after extraction of the maxillary first premolars. (c) Overbite was improved. (d) Torque and direction of the tooth movement were controlled by the location of TAD placement. CR, Center of resistance. Source: Park et al. [22]. Reprinted with permission.

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Section I  Fundamental Perspectives on TADs

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Figure 1.9  Deep bite correction with TADs [23]. (a) Initial examination indicated deep bite and excessive gingival display on smile (gummy smile). (b) TADs were inserted in the maxillary anterior area to intrude the maxillary incisors. (c) Maxillary molars were restricted from extrusion using a TAD-supported TPA connected to the maxillary molars with elastomeric chains. (d) Optimal overbite was achieved and gingival display on smile was significantly improved. (e) The maxillary anterior teeth were intruded, while excessive molar extrusion was prevented with a TAD-supported TPA. (f) Maxillary incisors were intruded and slightly retroclined. Source: Uzuka et al. [23]. Reprinted with permission from Elsevier.

incisal intrusion considerably simpler. For example, in patients with “gummy smile,” TADs have been inserted in the maxillary anterior and midpalatal areas to intrude the whole maxillary dentition, which results in an improved overbite and reduced excessive gingival display (Figure 1.9) [23]. Comparison studies have been performed to evaluate the effects of incisor intrusion treated with the aid of TADs or conventional utility archwires [24, 25]. These reports have commonly supported the idea that groups treated with TADs have less unfavorable tooth movements such as maxillary incisal proclination and maxillary molar tipping than do the groups treated with utility archwires alone.

1.3  ­Corrections in Transverse Dimensions 1.3.1  Palatal Expansion with Midpalatal Suture Split Although tooth‐borne rapid maxillary expanders (RMEs) have been most commonly used to treat adolescents with constricted maxillary arches, adverse effects have been reported with them such as undesirable tooth movement (e.g. buccal torque of the anchored teeth, limited skeletal expansion, the potential for root resorption, post‐expansion

Chapter 1  An Overview of Clinical Applications for TADs

Type a

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(b) Displacement after expansion

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Figure 1.10  Finite element analysis on displacement and stress distribution with different bone-borne palatal expanders [31]. (a) Occlusal views of the three types of palatal expanders: paramedian bone-borne expander (type a), palatal-slope bone-borne expander (type b), and conventional tooth-borne expander (type c). (b) Dental and skeletal displacements on the transverse plane after activation of the three different expanders. (c) Stress distributions on the maxilla and maxillary dentition after activation of the three different expanders. Source: Park et al. [31]. Reprinted with permission from Elsevier.

relapse, and unsuccessful midpalatal suture split) [26, 27]. Bone‐anchored expanders with TADs or hybrid types (i.e. tooth‐ and bone‐anchored expanders) are alternatives for applying direct force to the maxillary bone to overcome the limitations of the tooth‐borne expanders described above [28]. Many comparative studies have stated that bone‐ anchored expanders with TADs achieved outcomes that are just as good as traditional tooth‐borne expanders [28, 29]. Moreover, it is worth noting some studies have demonstrated successful treatment in adults with constricted maxillary arches, which used to be a very challenging treatment objective with traditional tooth‐borne expanders [30]. An FEA study demonstrated the displacement and the stress distribution with different types of palatal expanders: (i) paramedian bone‐borne expander, (ii) palatal‐slope bone‐ borne expander, and (iii) conventional tooth‐borne expander (Figure  1.10) [31]. Dental and skeletal displacements after the application of expansion forces widely varied with the different types of the expanders (Figure 1.10b). The magnitude and distribution of the stress after the application of the expansion forces were also determined for

each expander type (Figure  1.10c). Orthodontic clinicians can take these preclinical findings into consideration when selecting the expander type.

1.3.2  TADs for Impacted Teeth TADs have been used to treat difficult clinical problems which were previously deemed very challenging to impossible with traditional orthodontic modalities. Horizontally impacted mandibular molars are considered difficult to treat due to their limited access and limited anchorage support [32]. If areas distal to the second molars are available, horizontally impacted mandibular molars can be uprighted using retromolar TADs (Figure  1.11). Maxillary canine impaction is another challenging clinical problem that requires an adequate anchorage control. Palatally impacted canines, if transposed with adjacent teeth, can be even more complicated. Successful correction of a palatally impacted and transposed canine has been reported [33]. Once ideal direction of the forced eruption had been determined

11

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Section I  Fundamental Perspectives on TADs

(a)

(b)

(c)

(d)

(e)

Figure 1.11  Uprighting horizontally impacted mandibular second molars with TADs [32]. (a) Mandibular second molars were horizontally impacted. (b) Occlusal CBCT view of the horizontally impacted mandibular left second molar. (c) Biomechanical factors for uprighting impacted mandibular second molars: F, force; M, moment; d, distance. (d) Illustrations of biomechanical procedure for uprighting impacted mandibular second molars with retromolar TADs. (e) Treatment procedure for uprighting impacted mandibular second molars with retromolar TADs. Source: Kim et al. [32]. Reprinted with permission.

with cone‐beam computed tomography (CBCT), the impacted and transposed canine was successfully treated with palatal TADs (Figure 1.12).

1.4  ­Future Directions In a relatively short time, TADs have evolved extensively in both clinical applications and research perspectives [34]. In the 1980s and early 1990s, research topics focused primarily on the biomechanics of dental implants such as the preclinical evaluation of the bone–implant interface in terms of osseointegration, load bearing, and bone healing [34]. As the clinical application of TADs increased exponentially, the factors that account for their stability and success have been broadly classified as either the patient’s anatomical and periodontal conditions or specifications of the TADs in conjunction with their biomechanical properties. Researchers and clinicians have substantially broadened our understanding of TADs, particularly as new technologies such as CBCT and FEA have been introduced. Recently, evidence‐based clinical TAD studies have become widely available. In the past decade, an important but

limited number of systemic reviews, meta‐analyses, and randomized controlled trials on TADs have been published, focusing mainly on the stability of TADs and corrections in the anteroposterior dimension [34]. In recent years, TADs have introduced a new paradigm for orthodontic tooth movement, previously deemed inconceivable with traditional anchorage modalities. Post‐ treatment long‐term stability remains unevaluated and further long‐term follow‐up investigations are therefore needed. In order to provide stronger evidence‐based clinical guidance, many questions still need to be answered regarding TADs, with higher level hierarchy studies such as systemic reviews, meta‐analyses, and randomized controlled trials, especially for newly designed TAD‐supported appliances and their treatment outcomes. Combined treatment modalities with other approaches such as lingual fixed appliances and aligners have still not been investigated extensively. Just as the introduction of CBCT has considerably enriched our understanding and use of TADs, a series of new technologies (e.g. CAD/CAM, 3D bioprinting, regenerative medicine, AI machine learning) will ­further expand the horizon of clinical applications and research perspectives of TADs.

Chapter 1  An Overview of Clinical Applications for TADs

(a)

(b)

(d)

(c)

(e)

Figure 1.12  Forced eruption of an impacted and transposed canine [33]. Three-dimensional images were taken: (a) at the time of surgery and lingual button bonding; (b) 14 months after starting retraction of the canine; and (c) 27 months after starting retraction of the canine. (d) The maxillary left canine was well positioned with proper root parallelism and without any signs of root resorption. (e) The impacted canine was well aligned and bonded with a fixed retainer. Source: Lee et al. [33]. Reprinted with permission from Elsevier.

­References 1 Creekmore TD. The possibility of skeletal anchorage. J Clin Orthod. 1983;17:266–269. 2 Antoszewska‐Smith J, Sarul M, Łyczek J, et al. Effectiveness of orthodontic miniscrew implants in anchorage reinforcement during en‐masse retraction: a systematic review and meta‐analysis. Am J Orthod Dentofacial Orthop. 2017;151:440–455. 3 Sandler J, Murray A, Thiruvenkatachari B, et al. Effectiveness of 3 methods of anchorage reinforcement for

maximum anchorage in adolescents: a 3‐arm multicenter randomized clinical trial. Am J Orthod Dentofacial Orthop. 2014;146:10–20. 4 Yao CC, Lai EH, Chang JZ, et al. Comparison of treatment outcomes between skeletal anchorage and extraoral anchorage in adults with maxillary dentoalveolar protrusion. Am J Orthod Dentofacial Orthop. 2008;134:615–624. da Costa Grec RH, Janson G, Branco NC, et al. Intraoral 5 distalizer effects with conventional and skeletal anchorage:

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a meta‐analysis. Am J Orthod Dentofacial Orthop. 2013;143:602–615. 6 Escobar SA, Tellez PA, Moncada CA, et al. Distalization of maxillary molars with the bone‐supported pendulum: a clinical study. Am J Orthod Dentofacial Orthop. 2007;131:545–549. 7 Tai K, Park JH, Tatamiya M, Kojima Y. Distal movement of the mandibular dentition with temporary skeletal anchorage devices to correct a Class III malocclusion. Am J Orthod Dentofacial Orthop. 2013;144:715–725. 8 Manni A, Mutinelli S, Pasini M, et al. Herbst appliance anchored to miniscrews with 2 types of ligation: effectiveness in skeletal Class II treatment. Am J Orthod Dentofacial Orthop. 2016;149:871–880. 9 Cha BK, Choi DS, Ngan P, et al. Maxillary protraction with miniplates providing skeletal anchorage in a growing Class III patient. Am J Orthod Dentofacial Orthop. 2011;139:99–112. 10 Park JH, Tai K, Takagi M, et al. Esthetic orthodontic treatment with a double J retractor and temporary anchorage devices. Am J Orthod Dentofacial Orthop. 2012;141:796–805. 11 Kook YA, Park JH, Bayome M, Sa’aed NL. Correction of severe bimaxillary protrusion with first premolar extractions and total arch distalization with palatal anchorage plates. Am J Orthod Dentofacial Orthop. 2015;148:310–320. 12 Kook YA, Bayome M, Trang VTT, et al. Treatment effects of a modified palatal anchorage plate for distalization evaluated with cone‐beam computed tomography. Am J Orthod Dentofacial Orthop. 2014;146:47–54. 13 Kook YA, Park JH, Bayome M, et al. Application of palatal plate for nonextraction treatment in an adolescent boy with severe overjet. Am J Orthod Dentofacial Orthop. 2017;152:859–869. 14 Lee SK, Abbas NH, Bayome M, et al. A comparison of treatment effects of total arch distalization using modified C‐palatal plate vs buccal miniscrews. Angle Orthod. 2017;88:45–51. 15 Park JH, Kim S, Lee YJ, et al. Three‐dimensional evaluation of maxillary dentoalveolar changes and airway space after distalization in adults. Angle Orthod. 2018;88:187–194. 16 Sugawara J, Daimaruya T, Umemori M, et al. Distal movement of mandibular molars in adult patients with the skeletal anchorage system. Am J Orthod Dentofacial Orthop. 2004;125:130–138. 17 Kook YA, Park JH, Bayome M, et al. Distalization of the mandibular dentition with a ramal plate for skeletal Class III malocclusion correction. Am J Orthod Dentofacial Orthop. 2016;150:364–377.

18 Yu J, Park JH, Bayome M, et al. Treatment effects of mandibular total arch distalization using a ramal plate. Korean J Orthod. 2016;46:212–219. 19 Kim YB, Bayome M, Park JH, et al. Displacement of mandibular dentition during total arch distalization according to locations and types of TSADs: 3D Finite element analysis. Orthod Craniofac Res. 2019;22:46–52. 20 Park JH, Tai K, Ikeda M, Kim DA. Anterior open bite and Class II treatment with mandibular incisor extraction and temporary skeletal anchorage devices. J World Fed Orthod. 2012;1:e121–e131. 21 Park JH, Tai K, Takagi M. Open‐bite treatment using maxillary and mandibular miniplates. J Clin Orthod. 2015;49:398–408. 22 Park J, Tai K, Ikeda M. Anterior open‐bite correction with miniscrew anchorage and a combination of upper lingual and lower labial appliances. J Clin Orthod. 2017;51:719–727. 23 Uzuka S, Chae JM, Tai K, et al. Adult gummy smile correction with temporary skeletal anchorage devices. J World Fed Orthod. 2018;7:34–46. 24 Polat‐Özsoy Ö, Arman‐Özçırpıcı A, Veziroğlu F, Çetinşahin A. Comparison of the intrusive effects of miniscrews and utility arches. Am J Orthod Dentofacial Orthop. 2011;139:526–532. 25 Şenışık NE, Türkkahraman H. Treatment effects of intrusion arches and mini‐implant systems in deepbite patients. Am J Orthod Dentofacial Orthop. 2012;141:723–733. 26 Smalley WM, Shapiro PA, Hohl TH, et al. Osseointegrated titanium implants for maxillofacial protraction in monkeys. Am J Orthod Dentofacial Orthop. 1988;94:285–295. 27 Erverdi N, Okar I, Kücükkeles N, Arbak S. A comparison of two different rapid palatalexpansion techniques from the point of root resorption. Am J Orthod Dentofacial Orthop. 1994;106:47–51. 28 Lagravère MO, Carey J, Heo G, et al. Transverse, vertical, and anteroposterior changes from bone‐anchored maxillary expansion vs traditional rapid maxillary expansion: a randomized clinical trial. Am J Orthod Dentofacial Orthop. 2010;137:e1–e12. 29 Canan S, Şenışık NE. Comparison of the treatment effects of different rapid maxillary expansion devices on the maxilla and the mandible. Part 1: Evaluation of dentoalveolar changes. Am J Orthod Dentofacial Orthop. 2017;151:1125–1138. 30 Carlson C, Sung J, McComb RW, et al. Microimplant‐ assisted rapid palatal expansion appliance to orthopedically correct transverse maxillary deficiency in

Chapter 1  An Overview of Clinical Applications for TADs

an adult. Am J Orthod Dentofacial Orthop. 2016;149:716–728. 31 Park JH, Bayome M, Zahrowski JJ, Kook YA. Displacement and stress distribution by different bone‐ borne palatal expanders with facemask: a 3‐dimensional finite element analysis. Am J Orthod Dentofacial Orthop. 2017;151:105–117. 2 Kim KJ, Park JH, Kim MJ, et al. Posterior available space 3 for uprighting horizontally impacted mandibular second

molars using orthodontic microimplant anchorage. J Clin Pediatr Dent. 2018;43:56–63. 33 Lee MY, Park JH, Jung JG, Chae JM. Forced eruption of a palatally impacted and transposed canine with a temporary skeletal anchorage device. Am J Orthod Dentofacial Orthop. 2017;151:1148–1158. 4 Gandedkar NH, Koo CS, Sharan J, et al. The temporary 3 anchorage devices research terrain: current perspectives and future forecasts! Semin Orthod. 2018;24:191–206.

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2 Biomechanical Considerations for Controlling Target Tooth Movement with Mini-implants Jung Yul Cha Department of Orthodontics, Institute of Craniofacial Deformity, Yonsei University College of Dentistry, Seoul, South Korea

We often encounter cases where vertical control of the anterior dentition is required during retractions of anterior teeth, or where anteroposterior movement of the entire dentition is needed. In order to achieve the treatment objectives efficiently, mini‐implants can be used as skeletal anchorage and be placed in various locations within the alveolar bone. As the placement position of the mini‐ implants determines the line of force, the treating orthodontist should be able to predict the direction of tooth movement with orthodontic treatment. Thus, in order to design a goal‐driven movement of anterior or total dentition, a knowledge of the concepts around the center of resistance (CR) of the teeth is essential.

2.1  ­The CR for the Anterior Segments in Extraction Cases The clinical application of mini‐implants enables the clinician to adjust the line of force in various directions as well as the height of the maxillary and mandibular dentition. It is also possible to modify the outcome of alignment in 3D directions during anterior teeth retractions. To understand the CR, finite element analysis (FEA) using computer simulation or a direct measurement of the initial displacement of the dentition in response to the orthodontic force can be applied. Woo and Park [1] reported that the CR of the four maxillary anterior teeth was located 4.5 mm from the cementoenamel junction (CEJ) of the central incisor, and the six maxillary anterior teeth were located 6.5 mm apical to the CEJ. Vanden Bulcke et al. [2] used laser holography in a dry skull to examine the position of the CR according to the number of teeth during anterior traction. The CR of each tooth group was located at the 5 mm apical level from the

alveolar crest between the central incisors in the group of four anterior teeth and at the 7 mm level to the root apex in the group of six anterior teeth. Pedersen et  al. [3] used a strain sensor in an autopsy specimen of anterior maxillary bone. He reported that the CR was positioned 5 mm to the root apex and 13 mm posterior to the bracket position in the four‐tooth anterior segments, whereas it was was 6.5 mm to the root apex and 18 mm posterior to the bracket position of the central incisors in the six‐tooth anterior segment. Jeong et  al. [4] reported that the CR of the four maxillary anterior teeth and the six maxillary anterior teeth were located 13.5 mm apical and 12 mm posterior and 13.5 mm apical and 14 mm posterior to the incisal edge of the upper central incisor, respectively (Figure 2.1a). Yoshida et al. [5–7] used magnetic sensors and magnets to calculate the CR position of the maxillary dentition in an actual patient during anterior retraction. By measuring the initial displacement of the teeth with respect to the orthodontic force, the CR of the four anterior teeth was found to be 11.3–14.7 mm apical to the incisal edge, and the CR for the six anterior teeth was 10.5–13.7 mm from the incisor edge, which was lower than that for the four anterior teeth. Assuming an anterior bracket height of 4.5 mm, the CR is located at 6–9.7 mm from the level of the archwire, which is similar to the results of previous FEA [3, 4]. Therefore, if a lever arm of 7 mm or more in height is used for anterior teeth retraction, uncontrolled tipping of the anterior segment can be reduced and extrusion of the incisors can be controlled (Figure 2.1). Thus, the CR exists in a certain range within the alveolar bone, because it is estimated according to the definition and conditions of the model used in the FEA. It has also been reported that teeth are not completely restrained by the orthodontic wire (0.018 × 0.025‐in stainless steel) and

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section I  Fundamental Perspectives on TADs

(a)

6–10 mm

(b)

(c)

(d)

(e)

Figure 2.1  Various positions of the CR from previous studies and modifications of the line of force based on the location of mini-implants and lever arms. (a) CR positions of six anterior teeth from previous studies: Jeong et al. (gray) [4]; Vanden Bulcke et al. (orange) [2]; Pedersen et al. (red) [3]; Choy et al. (blue) [8]. (b) High position of mini-implant for anterior intrusion between first and second premolars. (c) Conventional application of mini-implant between second premolar and first molar. (d) Application of long lever arm for transitional movement of anterior teeth. (e) Application of long lever arm on palatal side for intrusion and retraction of maxillary incisors.

Chapter 2  Biomechanical Considerations

that the mechanical properties of orthodontic wires tend to move the teeth individually rather than as a single unit [9].

2.2  ­Vertical Control Using Mini-implants to Retract Anterior Teeth When vertical control is required during anterior teeth retraction in the clinic, vertical force can be applied effectively to the CR of the maxillary dentition by placing a mini‐implant in a high position. This prevents the anterior teeth from extruding as might occur during anterior teeth retraction. In order to apply a vertical force vector to the maxillary incisors, mini‐implants need to be placed between the maxillary first and second premolars (Figure  2.1b–d), and a surgical guide can be applied to ensure its success. In addition, if necessary, mini‐implants can be placed on the palatal side and a lever arm can be used to effectively apply intrusive force on the anterior teeth (Figure 2.1e).

(a)

2.3  ­Biomechanical Considerations for Total Arch Movement 2.3.1  Location of the CR in Maxillary and Mandibular Dentition Billiet et al. [10] reported that the CR of the entire dentition is at the lower edge of the zygomatic process above the first molar. There is an anatomical limitation in the classical approach when applying orthodontic force to the CR of the whole dentition. In contrast, in a study by Jeong et al. [4] the CR in the whole maxillary dentition group was reported to be 11.0 mm apical and 26.5 mm posterior to the maxillary incisor edge. This later study shows that a mini‐ implant can be placed within the alveolar bone region and orthodontic force can be applied close to the CR for distalization or intrusion of the entire dentition. In the mandible, the CR of the entire dentition was reported to be at a 3D location that was 13.5 mm apical and 25 mm posterior to the incisal edge of the maxillary central incisor, which is closer to the root apex than in the maxilla (Figure 2.2).

(c)

(e)

(d)

(f)

11 mm

26.5 mm

(b)

25 mm

13.5 mm

Figure 2.2  The position of the CR in the maxillary and mandibular dentition, and dentition change during total arch distalization. (a) The CR positions of full maxillary dentition from previous studies: Park et al. (orange) [13] Billiet et al. (red) [10]. (b) The CR position of full mandibular dentition (orange). (c) Distalization of maxillary dentition by TPA with hooks. (d) Superimposition image after total arch movement in maxilla (treatment result of c), lingual tipping and extrusion of incisors during total arch movement. (e) Intrusion of maxillary incisor by splinted wire with mini-implants on palatal slope. (f) Superimposition image after intrusion of maxillary incisors (treatment result of e).

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Section I  Fundamental Perspectives on TADs

However, the FEA model of existing studies assumed that the orthodontic archwire was a rigid body, and the location of the CR was calculated with the assumption that there was no play in the bracket. In practice, an additional torque may be needed to prevent lingual inclination of anterior teeth during distalization of the whole dentition (Figure 2.2).

2.3.2  Change of the Occlusal Plane in Total Arch Movement Lee and Kim [11] reported that during total arch distalization, the maxillary dentition moves stably toward the posterior without lingual inclination of the maxillary anterior segment. In addition, Roberts et al. [12] reported that ­intrusion of the mandibular molars and extrusion of the anterior

Case 2.1  Diagnosis A 21-year-old woman presented with the chief complaints of anterior protrusion, retrognathic profile, and crowding. She showed a convex profile with marked protrusion of her lips, lip incompetency, a retrognathic mandible, mentalis strain, and mild facial asymmetry. Her left temporomandibular joint had been treated due to osteoarthritis and a symptomatic sound. A lateral cephalogram showed severe facial and skeletal problems. Her skeletal pattern was hyperdivergent as indicated by the mandibular plane angle (SN-GoMe, 48.8°). She had a skeletal Class II pattern with steep occlusal plane angle (ANB, 6.9° and OP, 22.0°). She had an 8.0 mm overjet and 2.0 mm overbite. Her arch length discrepancies were 6.5 mm in the maxillary arch and 4.0 mm in the mandibular arch (Figure 2.3, Table 2.1).

7 mm in length; BMK, Seoul, South Korea) were placed into the buccal alveolar bone between the maxillary second premolars and the extracted first premolar area with high vertical position to control the maxillary incisor display. Then, immediately after installation of the mini-implants, elastomeric chains were placed from the maxillary mini-implants to the canine brackets for retraction of the maxillary anterior teeth (Figure  2.4). Following retraction of the maxillary anterior teeth, midline elastics and Class II elastics were used to correct the midline. Total treatment time was 23 months.

Treatment Alternatives

After treatment, the patient showed a more balanced face with improved lip profile as her lip incompetency and mentalis strain were corrected. The interference between maxillary anterior teeth and the lower lip was eliminated. After treatment her smile was improved because the maxillary anterior segment was intruded. The post-treatment lateral cephalogram showed improvement in the skeletal pattern. A  cephalometric superimposition showed controlled tipping of the maxillary anterior teeth with intrusion, uprighting of the maxillary posterior teeth, retraction with bodily movement of the mandibular anterior teeth, and uprighting of the mandibular posterior teeth (Figure 2.5).

Orthognathic surgery with bilateral sagittal split ramus osteotomy was suggested to the patient as the first treatment plan, but she did not want to undergo orthognathic surgery, so another treatment plan was needed. The second treatment option was orthodontic camouflage treatment with extraction of the maxillary first premolars, and mini-implants were proposed to achieve maximum anchorage to the maxillary arch. Treatment Progress After leveling of the maxillary arch, two tapered ­ axillary posterior mini-implants (1.5 mm in diameter, m

Treatment Results

Chapter 2  Biomechanical Considerations

Figure 2.3  Case 2.1: Pre-treatment photographs and radiographs.

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Section I  Fundamental Perspectives on TADs

Table 2.1  Case 2.1: Cephalometric measurements. Pre-treatment

Post-treatment

24-mo retention

46.2

47.6

48.1

FMA (°)

33.5

33.3

34.7

IMPA (°)

100.3

99.1

97.2

SNA (°)

77.2

76.7

76.9

SNB (°)

70.3

70.2

70.3

ANB (°)

6.9

6.5

6.6

AO–BO (mm)

2.7

0.1

0.3

FMIA (°)

Occlusal plane angle (°)

21.9

19.1

19.6

U1‐FH (°)

125.1

110.0

110.0

Z‐angle (°)

64.5

67.0

67.5

PFH (mm)

72.7

71.5

72.0

AFH (mm)

127.9

126.9

126.9

57.0

56.0

56.0

FHI (PFH/AFH) (%)

FMIA, Frankfort mandibular incisor angle; FMA, Frankfort mandibular plane angle; IMPA, incisor mandibular plane angle; SNA, sella‐ nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; AO-BO (Wits), distance between perpendicular lines drawn from A point and B point onto the occlusal plane; Occlusal plane angle, FH plane to occlusal plane; U1‐FH, long axis of maxillary central incisor to FH plane; Z angle, FH plane to Z line (line drawn from soft tissue pogonion to the most forwardly placed lip); PFH, posterior facial height, distance between sella and gonion; AFH, anterior facial height, distance between nasion and menton; FHI (PFH/AFH), posterior facial height/anterior facial height.

(a)

(b)

Figure 2.4  Case 2.1: (a) Leveling and alignment. Extraction of maxillary first premolars and regaining space for mandibular right central incisor with open coil spring. (b) Retraction of maxillary canines with elastomeric chain and high positioned maxillary miniscrews.

Chapter 2  Biomechanical Considerations

Figure 2.5  Case 2.1: Post-treatment photographs, radiographs, and superimposition of lateral cephalogram before and after treatment.

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Section I  Fundamental Perspectives on TADs

teeth occurred during total arch distalization of the mandibular dentition, resulting in counterclockwise rotation of the occlusal plane. In the FEA, less than 200 g of retraction force, 2 mm of extrusion of the mandibular incisors, and 3 mm of intrusion of the mandibular molars were generated combined with a 4° reduction of the occlusal plane in the mandibular arch. They also reported that a stress level of 1 mm away from the TAD three weeks after the placement in the maxillary bone (Figure 4.2b). We suggest that this woven bone tissue was formed in the early stage of the healing process, which maintained the thickness of the cortical bone and allowed the TAD to resist immediate loading. After three weeks, bone–implant (TAD) contact is approximately 30% (Figure 4.2b) in all regions (upper, middle, lower). After six weeks of healing, increased bone–implant contact can be observed mainly in the upper third of the TAD, whereas there is a decrease in the amount of bone–implant contact in the middle and lower regions (Figure 4.2c). Horizontally, after six weeks, an increased thickness of cortical bone can be observed >1 mm away from the TAD. After 12 weeks, healing ends with a uniform cortical bone thickness (Figure 4.2d). This indicates that as the alveolar bone surrounding the TAD heals, osseous tissue decreases in the lower region and increases in the upper region and near

Chapter 4  Histological Aspects During the Healing Process

(a)

(b)

T

(c) T

(d) T

T

L

W

Figure 4.2  (a) Microradiographs after three weeks of healing in the maxilla. Intense woven bone (W) has formed underneath the original lamellar bone (L) near the TAD (T). (b) Light microscopic photograph after three weeks of healing in the maxilla. Intense woven bone (W) has formed within 1 mm (white box) of the TAD (T) compared to >1 mm away (black box) from the TAD (T). (c) Light microscopic photograph after six weeks of healing in the maxilla. Significantly more lamellar bone is formed at the upper third (white box) of the TAD (T) compared to the lower two thirds (black box). (d) Light microscopic photograph after 12 weeks of healing in the maxilla: After 12 weeks, the healing process is mainly finished and osseous adaptation has recovered to the original cortical bone (white box).

the TAD, and thus it returns to the original form of the cortical bone before TAD placement. In contrast to the maxilla, less cortical bone is observed within 1 mm of TADs in the mandible three weeks after placement (Figure  4.3a). In the mandible, bone–implant contact shows less bone in the upper level than in the middle and lower regions (Figure 4.3a). This indicates that in (a)

the mandible, recovery of cortical bone thickness is not achieved yet after three weeks of healing. However, after six weeks, increased lamellar bone compaction can be observed, especially in the upper region (Figure  4.3b). Finally, normal cortical bone structure is present after 12 weeks (Figure 4.3c). Less bone forms around the TAD in the early stage of implant healing in the mandible, so this

(b) T

(c) T

T

Figure 4.3  (a) Light microscopic photograph after three weeks of healing in the mandible. In contrast to the maxilla, less bone is formed at the upper region (white box) of the TAD (T) compared to the middle and lower regions. (b) Light microscopic photograph after six weeks of healing in the mandible. Increased lamellar bone formation is observed in the upper region (white box) of the TAD (T). (c) Light microscopic photograph after 12 weeks of healing in the mandible. As in the case of the maxilla, after 12 weeks, the cortical bone returns to its original structure (white box).

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Section I  Fundamental Perspectives on TADs

might explain why there is a higher failure rate with TADs in the mandible than in the maxilla. This indicates that clinicians may need to avoid immediate heavy loading of TADs in the mandible.

4.3 ­Histomorphometric Parameters of Bone Surrounding TADs During Healing 4.3.1  Static Histomorphometric Parameters In the case of TADs, as little as 5% of bone–implant contact can successfully resist orthodontic force [1]. Five percent may be lower than the contact reported in other studies since we mainly used microradiographic images rather than light brightfield microscopy to measure all static parameters because microradiographs are better and more reliable [13]. Clearly, the amount of bone contact with the implant is important to the strength of the interface, but new and less mineralized (i.e. woven) bone at the interface will increase this parameter. Thus, the amount of bone–implant contact may not be the major factor as a stability indicator for TADs. 4.3.1.1  Bone Volume/Total Volume (BV/TV, %)

BV/TV represents the amount of mineralized bone expressed as a fraction of the total tissue [14]. It generally correlates directly with the bone–implant contact value. Even in the initial stage of healing (about three weeks), approximately 50% of the tissue around a TAD is bone. However, even in the later stages of healing (up to 12  weeks), BV/TV does not significantly change and remains at 50–60%. Thus, there is no significant change in the amount of bone surrounding a TAD from the initial healing to later stages of healing, but there is a significant change in the quality of the bone. 4.3.1.2  Woven Bone/Total Bone (WV/TV, %)

WV/TV represents the amount of unmineralized, immature bone and quality of bone measured with microradiographic analysis [14]. In the early stage of healing, there is approximately 50% of woven bone in the bone surrounding a TAD. This significantly decreases to 25% after six weeks of healing. Eventually it decreases to about 10–15% after 12 weeks of healing. Thus, after 12 weeks of healing, there is a significant change in the quality of bone as it is transformed from woven to lamellar bone.

4.3.2  Dynamic Histomorphometric Parameters 4.3.2.1  Mineralizing Surface/Bone Surface (MS/BS, %)

MS/BS is the proportion of a surface that is active in mineralization at a given time [14]. It is approximately 60% in the

initial stage of the healing. After six weeks, it significantly decreases to 30–40% and continues to decrease up to 12 weeks. In general, MS/BS is higher in the mandible than in the maxilla. Increased MS/BS, together with elevated values of WV/TV, indicate a dramatic increase in the overall bone turnover rate. 4.3.2.2  Mineral Appositional Rate (MAR, μm/day)

MAR is a measure of individual osteoblast activity [14]. It is approximately 3.0 μm/day after three weeks of healing, but decreases to 2.0–2.5 μm/day after 6–12 weeks of healing. 4.3.2.3  Bone Formation Rate (BFR, %/year)

BFR is the amount of bone replaced per volume of existing bone per year (BFR is derived from other histomorphometric values such as BV/TV, MS/BS, and MAR) [14]. At three weeks of healing, a significant increase in BFR (500–600%) is observed, but it decreases to 200–300% after 6–12 weeks of healing. There is an intense formation of woven bone and intense bone remodeling in the initial healing within 1 mm of the bone that surrounds a TAD in both the maxilla (Figure 4.4a) and mandible (Figure 4.4b). The BFR significantly increases in the initial stage to approximately 500%/year within 1 mm of the implant [1]. This increased bone formation during the initial healing seems to be a combined phenomenon of modeling and remodeling. In the later stage of healing, a much lower BFR is observed, but it is important to note that this value is still much higher (threefold increase) than the normal untreated level. After 12 weeks of healing, there is less remodeling and the main osseous tissue is composed of lamellar bone (Figure 4.4c,d). The continuous and accelerated remodeling process within 1 mm of a loaded TAD surface is possibly the mechanism that maintains the integrity between bone and the implant with immature woven bone. This process may prevent microdamage and microcrack accumulation at the bone–implant interface [15]. Huja et  al. [16] quantified the amount of microdamage adjacent to an implant in their studies, comparing microdamage accumulation immediately after implant placement and after a 12‐week healing period. Results showed that bone adjacent to implants after the 12‐week healing period had less microdamage than at insertion. They therefore suggested that the increased remodeling rate may prevent microdamage and repair microdamage that was caused during initial placement of the implant. Furthermore, immediate loading may cause microdamage which increases the bone remodeling rate and results in more woven bone formation that stabilizes the orthodontic loading.

Chapter 4  Histological Aspects During the Healing Process

(a)

(b)

T

(c)

T

(d)

T

T

Figure 4.4  (a) Fluorescent microscopic photograph after three weeks of healing with a maxillary TAD. Intense woven bone formation with increased bone remodeling is observed in the initial stage of healing in the surrounding alveolar bone within 1 mm (white box) of the TAD (T). (b) Fluorescent microscopic photograph after three weeks of healing with mandibular TADs. Compared to the maxilla, less bone remodeling is observed in the mandible, mainly in the lower two thirds (white box) of the TAD (T). (c) Fluorescent microscopic photograph after 12 weeks of healing with a maxillary TAD. Less bone remodeling is observed after 12 weeks of TAD (T) healing. (d) Fluorescent microscopic photograph after 12 weeks of healing with a mandibular TAD. Less bone remodeling is observed after 12 weeks of healing also with a mandibular TAD (T).

4.4  ­Histological Effects and Change of Histomorphometric Parameters After Application of Orthodontic Force on TADs In the first three weeks of healing after TAD placement in the maxilla there is a substantial woven bone formation within 1 mm of the TAD, but further away thinner cortical bone can be seen (Figure 4.5a,b). When force is applied to a TAD in the maxilla, the thickness of the cortical bone increases in all areas, with the thickest area being within 1 mm of the TAD (Figure 4.5c,d). In the mandible, however, less bone forms around a TAD three weeks after placement (Figure 4.5e,f). When force is applied to TADs in the mandible, there is an increase of cortical bone thickness in all areas, but it is less than in the maxilla (Figure 4.5g,h). In general, immediate loading on a TAD is possible because there is enough cortical bone, even in the initial stage of healing. However, an orthodontic force of 200–300 g would be too much for initial loading. Heavy loading in the early stage (three weeks) may cause less bone in the area away from the TAD.

4.4.1  Static Histomorphometric Parameters Increased bone contact has been observed in the early stage of healing with maxillary TADs (Figure 4.6a). However, application of an orthodontic force causes no significant change in the amount of bone–implant contact with maxillary TADs

(Figure 4.6b). Even after 12–16 weeks of force application, the average bone–implant contact of 30–40% remains the same (Figure 4.6c). There is a similar tendency with mandibular placed TADs, with no significant difference in the bone–implant contact between before (Figure  4.7a) and after force application (Figure 4.7b). There is also no significant difference between 3 and 12 weeks of healing with TADs (Figure  4.7c), which means that after about three weeks in dog (approximately four weeks in humans) of healing, there is no further change in the amount of bone– implant contact with a TAD. The biomechanical resistance of a rigid implant to occlusal loads is related to both the quality and quantity of the integrated interface. In the case of TADs, less than 50% of bone–implant contact seems to be sufficient to resist orthodontic force. Immediate loading does not result in any significant difference in the bone– implant contact. BV/TV does not significantly change with the application of an orthodontic force but remains approximately 40% in both jaws (Figures 4.6 and 4.7). Stable static histomorphometric values seem to be constant not only with delayed loading but also with immediate loading. Immediate loading might accelerate the bone remodeling phenomenon, resulting in maintenance of bone volume that surrounds a TAD. After the application of orthodontic loading, woven bone has been observed to be about 20% of the total bone volume. The higher percentage of load‐bearing lamellar bone might contribute to TAD stability when force is applied.

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Section I  Fundamental Perspectives on TADs

(a)

(b) T

T

L

W d (d)

(c)

e

f (e)

(g)

(f)

(h)

g Figure 4.5  (a) Light microscopic photograph three weeks after TAD placement in the maxilla. Thicker bone is observed within 1 mm (white arrows) of the TAD (T) compared to 2–3 mm (red arrows) or 3–4 mm away (blue arrows). (b) Microradiographic photograph three weeks after TAD placement in the maxilla. In contrast to the light microscopic photograph, more precise evaluation is possible with a microradiograph. (c, d) Light (c) and microradiographic photographs (d) after 12 weeks of orthodontic force application in the maxilla. Increase of cortical bone is observed in all areas: within 1 mm (white arrow), 2–3 mm from TAD (red arrow), and 3–4 mm from TAD (blue arrow). (e, f) Light microscopic (e) and microradiographic photograph (f) three weeks after TAD placement in the mandible. Less cortical bone formation is observed within 1 mm of the TAD (arrowhead). (g, h) Light microscopic (g) and microradiographic photograph (h) after 12 weeks of force application in the mandible after three weeks of healing. Increased cortical bone thickness is observed within 1 mm of the TAD (white arrow), but there is little change 2–3 mm (red arrow) or 3–4 mm (blue arrow) away from the TADs.

4.4.2  Dynamic Histomorphometric Parameters The MS/BS around TADs does not change significantly after orthodontic force application. It remains approximately 30–40%, although this is still slightly higher than the MS/BS for normal bone (20%), such as the alveolar bone around the roots.

The MAR remains approximately 2.0–2.5 μm/day. This is about the same as the normal physiological MAR in alveolar bone. The BFR remains at approximately 200%. This is still significantly higher than the BFR of normal alveolar bone (Figure  4.8a,b). The reason for this high remodeling rate

Chapter 4  Histological Aspects During the Healing Process

(a)

(c)

(b) T

T

T

Figure 4.6  (a) Light microscopic photograph three weeks after TAD placement. Even in the initial stage of healing, an average of 30–40% bone–implant contact is observed. (b) Light microscopic photograph after 12–16 weeks of orthodontic force application after three weeks of healing. No significant difference in bone–implant contact is observed after force application. (c) Light microscopic photograph after force application with 12 weeks of healing. There is no significant difference in bone–implant contact with longer healing duration.

(a)

(c)

(b) T

T

T

Figure 4.7  (a–c) Light microscopic photographs three weeks after TAD placement in the mandible (a), after three weeks of healing followed by 12 weeks of force application (b), and after 12 weeks of healing force (c). With most mandibular TADs, the upper third has less bone–implant contact than other regions.

might be the existence of a microfracture caused by continuous orthodontic loading. From histological findings and histomorphometric ­analysis, we suggest that force on TADs does not have a

negative impact on the healing process around them, but may even increase the amount of osseous tissue surrounding TADs in the maxilla. In a previous study, orthodontic force caused microdamage [16], resulting in

43

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Section I  Fundamental Perspectives on TADs

(a)

(b) T

T

increased bone remodeling that could lead to an increased amount of osseous tissue surrounding the TAD. Therefore, from a clinical standpoint, immediate loading may be preferable in the maxilla to enhance the stability of the TADs.

4.5  ­Conclusions

Figure 4.8  (a) Fluorescent microscopic photograph of force applied to maxillary TAD after three weeks of healing. Orthodontic force seems to induce bone remodeling/modeling. (b) Fluorescent microscopic photograph after force application that healed for three weeks. The same tendency is seen in the mandibular TAD where orthodontic force stimulates the bone turnover during force application.

Because TADs do not require osseointegration, but rather benefit from immediate (or early) loading, we need to acknowledge some differences in healing patterns between them and prosthetic implants. TADs also operate according to different principles because they are smaller than prosthetic implants and are placed in different locations. Root proximity and cortical bone thickness play an important role in the stability of TADs. Future histomorphometric analysis research that focuses on enhancing the TAD healing process may help to further increase the stability of TADs.

­References 1 Deguchi T, Takano‐Yamamoto T, Kanomi R, et al. The use of small titanium screws for orthodontic anchorage. J Dent Res. 2003;82:377–381. 2 Roberts WE, Turley PK, Brezniak N, Fielder PJ. Bone physiology and metabolism. J Calif Dent Assoc. 1987;15:54–61. 3 Frost HM. The Laws of Bone Structure. Springfield, IL: Charles C. Thomas, 1964. 4 Roberts WE, Orthodontics, current principle and techniques. In: Graber TM, Vanarsdall Jr RL, eds. Bone Physiology, Metabolism, and Biomechanics in Orthodontic Practice. St. Louis, MO: Mosby, 2000, p. 214. 5 Harris WH, Heaney RP. Skeletal renewal and metabolic bone disease. N Engl J Med. 1969;280:193–202. 6 Takahashi H, Norimatsu H, Watanabe G, et al. The remodeling period (sigma) in canine and human trabecular bone. In: Yoshitoshi U, Fujita T, eds. Calcium Endocrinology, Tokyo: Chugai Igaku, 1980, pp. 13–31. 7 Frost HM. The regional acceleratory phenomenon: a review. Henry Ford Hosp Med J. 1983;31:3–9. 8 Roberts EW, Poon LC, Smith RK. Interface histology of rigid endosseous implants. J Oral Implantol. 1986;12:406–416. 9 Sağirkaya E, Kucukekenci AS, Karasoy D, et al. Comparative assessments, meta‐analysis, and recommended guidelines for reporting studies on

10 11

12

13

14 15

16

histomorphometric bone‐implant contact in humans. Int J Oral Maxillofac Implants 2013;28:1243–1253. Weiner S, Traub W. Bone structure: from angstroms to microns. FASEB J. 1992;6:879–885. Miyawaki S, Koyama I, Inoue M, et al. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2003;124:373–378. Deguchi T, Nasu M, Murakami K, et al. Quantitative evaluation of cortical bone thickness with computed tomographic scanning for orthodontic implants. Am J Orthod Dentofacial Orthop. 2006;129:721.e7–12. Parr JA, Young T, Dunn‐Jena P, Garetto LP. Histomorphometrical analysis of the bone‐implant interface: comparison of microradiography and brightfield microscopy. Biomaterials 1996;17:1921–1926. Parfitt AM. Bone Histomorphometry: Techniques and Interpretations. Boca Raton, FL: CRC Press, 1983. Yadav S, Upadhyay M, Liu S, et al. Microdamage of the cortical bone during mini‐implant insertion with self‐ drilling and self‐tapping techniques: a randomized controlled trial. Am J Orthod Dentofacial Orthop. 2012;141:538–546. Huja SS, Katona TR, Burr DB, et al. Microdamage adjacent to endosseous implants. Bone 1999;25:217–222.

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5 The Effects of TADs on the Alveolar Bone Jing Chen, Karolina Kister, and Sunil Wadhwa Division of Orthodontics, College of Dental Medicine, Columbia University, New York, NY, USA

Anchorage control is one of the primary concerns when orthodontists design the biomechanics for orthodontic treatment. Temporary anchorage devices, commonly referred to as TADs, have been a well‐developed and well‐ accepted form of anchorage for the past three decades. Types of TADs include miniscrews, palatal implants, and minibone plates  [1]. Their retention and stability in the bone during orthodontic treatment are crucial to their success as anchorage devices. Retention can be obtained either by primary retention – mechanical interlocking with bone from the screw threads of the device  –  or by secondary retention from osseointegration of the device. In this chapter, we review bone biology and the factors that contribute to the stability of mechanically retained and osseointegrated TADs. We also review commonly prescribed drugs that may have effects on the retention of TADs.

5.1  ­The History of TADs The first reported attempt at skeletal anchorage with implantable dental devices was published in 1945 by Gainsforth and Higley [2]. These researchers placed Vitallium screws in the mandibles of dogs as anchors for the application of orthodontic force. The study had limited success because although the screws were retained initially, the application of orthodontic force caused the screws to be lost within four weeks. Over the next 40 years, very few studies were reported on TADs. In 1969, Linkow [3] published a report on the use of blade implants followed by immediate force application to anchor Class II elastics. Sherman [4] published a study in 1978 that looked at bone reaction to TAD placement and the application of orthodontic force. This study, using vitreous carbon screws, recommended a lag time between placement of the TAD and orthodontic force application. Branemark et al. [5, 6]

conducted studies during this same time period that showed stable osseointegration of titanium implants without any adverse tissue effects. In the 1980s, orthodontic implant anchorage became a focal point of interest for many researchers. The main goal of these animal studies was to determine the effectiveness of using dental implants for orthodontic anchorage, in addition to exploring the tissue response to varying implant materials. Gray et al. [7] examined the efficacy of two types of endosseous implants (Vitallium implants and Bioglass‐ coated implants) for orthodontic anchorage. The devices were placed into the femurs of rabbits and were loaded with constant orthodontic forces (60 g, 120 g, and 180 g) after 28 days of healing. They reported no statistically significant movement of implants for either type of implant at any of the force levels. On a histologic level, tissue samples revealed a connective tissue encapsulation with the Vitallium implant and a bone bond with the Bioglass implant. Roberts et al. [8] published results similar to those of Gray et al. with the use of titanium implants in rabbits. They placed the implants in the femurs, allowed 6–12 weeks for healing and then loaded the implants with 100 g of force for 4–8 weeks. Histological evaluation showed that there was extensive bone formation three days after implant placement, particularly at the endosteal margin of the surgical defect. By the end of six weeks of healing, a rigid bone–implant interface had been achieved. During the loading period, 19 of the 20 implants remained rigid. From this study, it was concluded that “six weeks is an adequate healing period, prior to loading, to attain rigid stability and avoid spontaneous fracture, and that titanium endosseous implants have potential as a source of firm osseous anchorage for orthodontics and dentofacial orthopedics” [8]. In addition to animal studies, some human case reports on the use of TADs for orthodontic anchorage were also published in the 1980s. Creekmore and Eklund [9]

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section I  Fundamental Perspectives on TADs

­ resented a case in which they used a Vitallium screw to p intrude an elongated maxillary incisor. Roberts et al. [10] reported that they successfully protracted two mandibular molars 10–12 mm into an atrophic edentulous ridge using a traditional two‐stage endosseous implant as anchorage. Up to this time, studies on anchorage were being conducted with traditional dental implants in an orthodontic setting. Based on the success of the research conducted in the 1980s, examiners began developing orthodontic‐specific implants of various designs. Miniscrew implants became commercially available for orthodontic anchorage. Kanomi studied the use of these small titanium miniscrew implants for orthodontic anchorage when intruding mandibular central incisors [11]. In his study, minibone screws (1–2 mm in diameter and 6 mm in length) were placed in the alveolar bone between the root apices of the mandibular incisors, and intrusive forces were loaded onto the screws. Other researchers developed more extensive implant designs specifically for orthodontic anchorage. Block and Hoffman [12] used an Onplant system which consisted of a titanium alloy disk with a hydroxyapatite coating on one side and an internal thread on the other side to provide palatal anchorage. Sugawara et al. [13, 14] introduced a new skeletal anchorage system consisting of a titanium miniplate temporarily fixed in the maxilla or mandible for molar intrusion to correct open bite malocclusions. All of these implants came with a common recommendation for use: incorporate healing time to achieve osseointegration before loading the implant with orthodontic forces. The next logical research step was to ask whether or not osseointegration is desirable and/or necessary for TADs to be successful as orthodontic anchorage devices. Therefore, the concept of mechanical retention was developed. One early published study by Freudenthaler et  al. specifically examined immediately loaded mechanically retained orthodontic TADs. In this study, orthodontic forces were applied to inserted screws without healing time. Of the 12 screws initially implanted, only one screw was removed due to looseness. Two screws were prematurely removed due to soft tissue irritation and replaced after tissue healing. The remaining nine screws remained stationary during the duration of force application. The authors concluded “the total treatment time is reduced as the screws can be loaded immediately” [15]. The absence of osseointegration also made TAD removal simple and minimally invasive. Initially, orthodontic implants were primarily inserted by a self‐tapping method. This involves tapping a screw into a predrilled hole in the bone. In 2005, Kim et al. [16] compared this method with a drill‐free application using self‐ drilling screws. In this study, 32 screws (16 self‐tapping,

16 self‐drilling) screws were inserted into the jaws of two beagle dogs. One week after insertion, forces of 200–300 g were applied using nickel–titanium coil springs. Twelve weeks after insertion, the mobility of the screws was tested. Subsequently, the screws and surrounding bone were prepared for histomorphometric evaluation. The screws in the self‐drilling group showed less mobility and more bone‐to‐ metal contact compared with the self‐tapping group. However, osseointegration was generally found with both types of screws [16]. Huja et al. [17, 18] also found that self‐ drilling titanium screws provide sufficient pull‐out strength to withstand orthodontic loads and form bone contact within six weeks of insertion.

5.2  ­Biological Response to Orthodontic TADs Cope proposed classifying orthodontic TADs into two groups: osseointegrated TADs and mechanically retained TADs [19]. The biological responses to these types are quite different. Osseointegrated TADs rely on maximum contact between the surfaces of the device and the bone to achieve osteointegration. Mechanically retained TADs have areas of direct bony contact but also have more gaps where there is minimal to no bony contact (Figure 5.1). The insertion of both types of TAD initiates a series of biological processes (Table 5.1), including the formation of a blood clot, an alteration in the nuclear morphology of the osteocytes surrounding the site of the implant, and the formation of new bone.

5.2.1  Osseointegrated Orthodontic TADs In the late twentieth century, multiple osseointegration studies involving the insertion of titanium implants were conducted. Immediately following insertion of a titanium implant, the surface comes into contact with blood, and becomes covered by a biofilm which contains fibrinogen and serine proteases of the complement and coagulation system [20]. Red blood cells and platelets attach to the biofilm which results in a blood clot that is formed between the interface of the bone and the implant [20, 21]. This blood clot contains fibrin and may also contain polygonal bone chips that are assumed to be a result of surgical preparation at the insertion site or the insertion of the screw itself [22]. ●●

Day 1 after insertion: Red blood cells and inflammatory cells, mainly consisting of neutrophils, are found between the bone and implant. Within the bone directly adjacent to the implant, the appearance of the osteocytes

Chapter 5  The Effects of TADs on the Alveolar Bone

(b)

(c)

Implant

(a)

Bone Fibrous tissue

Figure 5.1  Illustrations of the bone–implant interface. (a) No osseointegration. It was believed to have a pure mechanical retention. (b) Partial osseointegration. More recent studies indicate almost all mini‐implants have a combination of varying amounts of bone formation and fibrous tissue on the thread surface. (c) Total osseointegration, which provides bony osseointegrated retention.

Table 5.1  Comparison of the biological responses for osseointegrated TADs and mechanically retained TADs. Time

Osseointegrated TADs

Mechanically retained TADs

Immediate

Biofilm‐formation of blood clot

Direct contact with bone and microfractures within the bone

1 day

Red blood and inflammatory cells

Attachment of osteoblasts to the titanium surface

3–5 days

Appearance of osteoblasts and a decrease in inflammatory cells

Osteocyte cell death

1–4 weeks

Bone remodeling

Bone remodeling

●●

●●

●●

●●

is altered with empty osteocytic lacunae and pyknotic osteocytic nuclei extending up to 100 μm in the bone [23, 24]. Days 3–7 after insertion: Inflammatory cell infiltration gradually tends to disappear. Spindle‐shaped or flattened cells start to appear in the interface between pre‐existing bone and the orthodontic implant [23]. Two to four weeks after insertion: Cuboidal osteoblasts are clearly visible at the interface between the bone and the implant. New collagen fibers are found to run circumferentially around the anchorage device cavity, whereas the fibers of the existing bone have a direction similar to the long axis of the bone. Numerous bone modeling units containing multinucleated osteoclasts and blood vessels also appear in the cortical bone surrounding the implant [25]. Six weeks after insertion: Active bone remodeling appears to decrease and a region of empty osteocytic lacunae is still adjacent to the region of newly deposited bone [24]. Post‐healing: After six weeks of healing time and osseointegration, the device is ready to be loaded with orthodontic forces. This loading causes increased bone tissue turnover and increased bone density in the adjacent alveolar bone as compared to an unloaded control.

However, despite increased bone tissue turnover, the TAD maintains osseous integration even after 32 weeks of orthodontic loading [26, 27]. Additionally, there is no significant difference in bone remodeling around the bone–TAD surface in terms of compression, tension, or shear [27, 28].

5.2.2  Mechanically Retained TADs Mechanically retained TADs do not rely on biological response to their insertion for stability, but bony changes do occur. ●●

Day 1–7 after insertion: In the first week following mechanically retained orthodontic implant placement, there is a decrease in markers of osteoblast differentiation, a decrease in proliferation, an increase in osteocyte death, and an increase in alveolar bone microfractures around the orthodontic implant compared to the areas not directly in contact with the implant [29]. There is also no invasion of inflammatory cells during the first week, and osteoblasts are found to be firmly attached to the TAD titanium surface [30].

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Section I  Fundamental Perspectives on TADs ●●

One to two weeks after insertion: In the areas in direct contact with implants, the bone is resorbed by osteoclasts and replaced with newly formed viable bone. Despite this temporary loss of hard bone contact, the implants remained clinically stable [31].

5.2.3  Overlap Between Osseous Integrated and Mechanically Retained Orthodontic TADs Mechanically retained orthodontic TADs are associated with early or immediate loading and easy removal. In contrast, osseointegrated orthodontic TADs are associated with delayed loading, the ability to withstand higher applied orthodontic forces for longer durations, and difficulty in removal. However, these distinctions are not absolute. Recent research indicates that mechanically retained orthodontic implants do also become partially osseointegrated. The majority of studies have shown that mechanically retained orthodontic implants become partially ossseointegrated. In one study, it was shown on pigs that almost all the mini‐implant threads were surrounded by bone with some interposition of connective fibrous tissue between bone and the mini‐implant. The amount of direct bone contact with the implant after 120 days was 13–27% with no significant difference between unloaded and loaded ones with 125 g force at three time intervals (immediate, after 15 days, or after 30 days) [32]. Other studies found a higher percentage of bone–implant contact in immediately loaded orthodontic implants of 70.96% after 12 weeks in rabbits [33] and 74.48% after six months in immediately loaded mini‐implants in dogs [34]. This partial osseointegration of the mini‐implant is beneficial because it provides greater long‐term stability of the implant, but still allows for its removal. However, the optimal level of partial osseointregation remains unknown. The gold standard metric used to describe a successful implant has been osseointegration, or direct contact of the implant device and the load‐bearing bone [35]. This can be quantified using multiple parameters including: percent bone–implant contact (BIC), percent bone volume fraction within screw threads (BV/TV), and bone modeling percentage of the adjacent bone (bone formation rate/year) [35]. BIC is frequently measured in most studies that perform histological sectioning, and is a static metric of a dynamic process. However, there is still no clear consensus regarding the BIC required for both implant success and ease of removal. For example, it was demonstrated that the removal torque did not correspond to BIC values in rabbits after 1–8 weeks [36]. Furthermore, implants with enough bone contact still failed, while others with substantially less contact became successful [35]. Future studies on the

nanoscale molecular interface between implant and bone may provide clarification on this subject [37].

5.3  ­Factors that Predict Implant Stability Most current systematic reviews and meta‐analyses show that orthodontic TADs have failure rates of less than 20% [38–41], which suggests a high level of success. There seems to be very little agreement on factors that promote TAD success following orthodontic loads. It appears that the only thing the reviewers agree on is that TADs placed in the maxilla have a lower failure rate than TADs placed in the mandible [39, 42]. Factors that do not seem to play a role in orthodontic TAD failures are self‐drilling versus non‐self‐drilling [41] immediate loading versus delayed loading (more than three weeks) [42], and the gender of the patient [39, 41, 42]. Finally, the roles of implant design (i.e. length and width) and age of the patient receiving orthodontic implants are inconclusive [39, 41, 42].

5.4  ­Commonly Prescribed Drugs that May Affect the Stability of TADs There are only a few specific articles about the effects of medications on orthodontic implant stability. However, a number of studies that have examined the role of medications on dental implant survival and osseointegration might be applied to orthodontic TADs (Table 5.2).

5.4.1  Non-steroidal Anti-inflammatory Drugs (NSAIDs) NSAIDs inhibit the prostaglandin synthase pathway. Cyclooxygenase (COX) is the rate‐limiting enzyme responsible for the conversion of arachidonic acid into prostaglandins. There are two isoforms of the enzyme: COX‐1, which is constitutively expressed, and COX‐2, which is inducible. Animals studies clearly show that COX‐2 inhibition will inhibit dental implant osseointegration [43]. However, human clinical trials indicate that medications that inhibit both COX‐1 and COX‐2 do not affect dental implant stability [44–46]. In a recent meta‐analysis, it was therefore concluded that “there is a lack of consensus in the literature to explicitly conclude that there is a relationship between the use of post-operative NSAIDs and failed osseointegration; however, osseointegration does not appear to be negatively affected by NSAIDs in the human clinical studies” [47].

Chapter 5  The Effects of TADs on the Alveolar Bone

Table 5.2  The effects of various medications on osseointegration and mechanical retention. Drug

Osseointegration

Mechanical retention

NSAIDs

May have a small effect in decreasing osseointegration

No effect

Bisphosphonates

Increase

Increase by improving bone density

RANKL antibody

Increase

Increase by improving bone density

SSRIs

Decreases

Probably no effect

PPIs

Decreases

Probably decreases

NSAIDs, Non‐steroidal anti‐inflammatory drugs; SSRIs, selective serotonin reuptake inhibitors; PPIs, protein pump inhibitors.

Other recently published meta‐analyses also support the minimal effect of NSAIDs on dental implant stability [48].

5.4.2  Bone Anti-resorptive Medications The two main anti‐resorptive drugs are bisphosphonates and anti‐RANKL antibody. Both inhibit osteoclast activity and both have been reported to cause an increase in osteonecrosis of the jaw (ONJ). Bisphosphonates are a class of drugs that inhibit bone resorption by promoting osteoclast death. They may be administered orally or intravenously. There are two classes: non‐nitrogenous and nitrogenous, each having two different mechanisms of actions. The non‐nitrogenous bisphosphonates are metabolized in the cell into compounds that compete with adenosine triphosphate (ATP). The nitrogenous bisphosphonates block the enzyme farnesyl diphosphate synthase. Bisphosphonates are used in a variety of conditions that cause bone fragility, such as osteoporosis, osteitis deformans, osteogenesis imperfecta, and bone metastasis in cancer patients. In a recent study it was shown that one dose of bisphosphonate enhanced orthodontic mini‐implant stability due to increased trabecular bone that surrounded the implant in foxhounds [49]. A recent systematic review also supported that low‐dose bisphosphonate treatment for osteoporosis enhances dental implant survival [50]. However, it is also evident that there is an increase in the incidence of ONJ in patients who are taking bisphosphonates and have dental procedures. In the general population the prevalence of ONJ is less than 0.001%. For osteoporosis patients, the prevalence of ONJ in patients taking oral bisphosphonate is 0–0.04% and in patients receiving intravenous bisphosphonates is 0–0.348%. Finally, in cancer patients taking intravenous bisphosphonates, the prevalence of ONJ is 0–0.186% [51]. Taken together, the statistics suggest that orthodontic mini‐implants should be avoided in patients taking intravenous bisphosphonates, whereas it is unclear whether

orthodontic implants should be placed in patients taking oral bisphosphonates. One advantage of bisphosphonates is that orthodontic implant stability will increase, however the disadvantage is that the rate of tooth movement is slower and there is incomplete space closure in patients taking bisphosphonates [52]. These data raise the question as to whether complex orthodontic treatment should even be performed in patients taking bisphosphonates for osteoporosis. RANK ligand (RANKL) is crucial for the formation and activation of osteoclasts, therefore its antibody inhibits bone resorption. Denosumab, a RANKL antibody, is a recently approved drug for treatment of osteoporosis. Limited studies have examined the role of denosumab on dental implant stability. The results have shown that denosumab improves screw fixation in cancellous bones of rats [53]. However, the incidence of ONJ with denosumab is similar to that in patients taking bisphosphonates for osteoporosis treatment [51], and higher in patients with cancer taking bisphophonates [54]. This makes the widespread use of denosumab to promote dental implant stability unlikely.

5.4.3  Selective Serotonin Reuptake Inhibitors (SSRIs) SSRIs are some of most commonly used drugs for depression. There are no reports of SSRIs affecting orthodontic implants. In 2014, researchers in Canada found that people taking this kind of drug had about twice as many dental implant failures as people not taking the drug [55]. Similar results have now been found in a number of other studies [56, 57]. It has been shown that SSRIs inhibit bone healing in a calvarial defect model in mice [58] and negatively affects fracture healing of murine long bones [59]. However, in a recent meta‐analysis, it was shown that SSRI use was not associated with any change in bone mineral density in humans [60]. Taken together, the research suggests that the mechanism of action of SSRIs on dental implant failures

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has more to do with bone repair to injury than to defects in bone remodeling to maintain homeostasis, making it unlikely to affect the stability of mechanically retained orthodontic implants.

5.4.4  Proton Pump Inhibitors (PPIs) PPIs are commonly given to reduce stomach acid production in people with gastric ulcers. Recent studies have shown that people who take PPIs are twice as likely to have dental implant failures than people not taking the drug [61, 62]. A recent meta‐analysis concluded that patients who take PPI have an increased risk of bone fractures [63]. However, whether they affect bone density and their mechanism of action in bone remains in question [64, 65]. Taken together, these studies suggest that patients taking PPIs may have an increased risk of orthodontic implant failures.

5.5  ­Conclusions The biological response and the factors that predict stability are different in mechanically retained and osseointegrated TADs. However, recent research and the development of new types of TADs have made the distinction less clear. Despite the relative ease with which these devices are placed and removed, the failure rate of TADs appears to be 10–20%. Careful attention should be paid to the medical history of patients in order to find out whether they are taking certain drugs that may affect TAD stability. In addition, future research is needed to discover the biological mechanisms behind TAD failures.

­5.6  Acknowledgments I would like to thank Chris Ricuperio (PhD) and Christine O’Hea (DMD, MDS) for their help in preparing this chapter.

­References 1 Heymann GC, Tulloch JF. Implantable devices as orthodontic anchorage: a review of current treatment modalities. J Esthet Restor Dent. 2006;18:68–79; discussion 80. 2 Gainsforth BL, Higley LB. A study of orthodontic anchorage possibilities in basal bone. Am J Orthod. 1945;31:406–417. 3 Linkow LI. The endosseous blade implant and its use in orthodontics. Int J Orthod. 1969;7:149–154. 4 Sherman AJ. Bone reaction to orthodontic forces on vitreous carbon dental implants. Am J Orthod. 1978;74:79–87. 5 Adell R, Hansson BO, Branemark PI, Breine U. Intra‐ osseous anchorage of dental prostheses. II. Review of clinical approaches. Scand J Plast Reconstr Surg. 1970; 4:19–34. 6 Branemark PI, Adell R, Breine U, et al. Intra‐osseous anchorage of dental prostheses. I. Experimental studies. Scand J Plast Reconstr Surg. 1969;3:81–100. 7 Gray JB, Steen ME, King GJ, Clark AE. Studies on the efficacy of implants as orthodontic anchorage. Am J Orthod. 1983;83:311–317. 8 Roberts WE, Smith RK, Zilberman Y, et al. Osseous adaptation to continuous loading of rigid endosseous implants. Am J Orthod. 1984;86:95–111. 9 Creekmore TD, Eklund MK. The possibility of skeletal anchorage. J Clin Orthod. 1983;17:266–269. 10 Roberts WE, Marshall KJ, Mozsary PG. Rigid endosseous implant utilized as anchorage to protract molars and

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close an atrophic extraction site. Angle Orthod. 1990;60:135–152. Kanomi R. Mini‐implant for orthodontic anchorage. J Clin Orthod. 1997;31:763–767. Block MS, Hoffman DR. A new device for absolute anchorage for orthodontics. Am J Orthod Dentofacial Orthop. 1995;107:251–258. Sugawara J, Baik UB, Umemori M, et al. Treatment and posttreatment dentoalveolar changes following intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthodon Orthognath Surg. 2002;17:243–253. Umemori M, Sugawara J, Mitani H, et al. Skeletal anchorage system for open‐bite correction. Am J Orthod Dentofacial Orthop. 1999;115:166–174. Freudenthaler JW, Haas R, Bantleon H. Bicortical titanium screws for critical orthodontic anchorage in the mandible: a preliminary report on clinical applications. Clin Oral Implants Res. 2001;12:358–363. Kim JW, Ahn SJ, Chang YI. Histomorphometric and mechanical analyses of the drill‐free screw as orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2005;128:190–194. Huja SS, Litsky AS, Beck FM, et al. Pull‐out strength of monocortical screws placed in the maxillae and mandibles of dogs. Am J Orthod Dentofacial Orthop. 2005;127:307–313. Huja SS, Rao J, Struckhoff JA, et al. Biomechanical and histomorphometric analyses of monocortical screws at

Chapter 5  The Effects of TADs on the Alveolar Bone

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placement and 6 weeks postinsertion. J Oral Implantol. 2006;32:110–116. Cope JB. Temporary anchorage devices in orthodontics: a paradigm shift. Semin Orthod. 2005;11:3–9. Nygren H, Tengvall P, Lundström I. The initial reactions of Ti02 with blood. J Biomed Mater Res. 1997; 34:487–492. Park JY, Davies JE. Red blood cell and platelet interactions with titanium implant surfaces. Clin Oral Implants Res. 2000;11:530–539. Franchi M, Fini M, Martini D, et al. Biological fixation of endosseous implants. Micron. 2005;36:665–671. Futami T, Fujii N, Ohnishi H, et al. Tissue response to titanium implants in the rat maxilla: ultrastructural and histochemical observations of the bone‐titanium interface. J Periodontol. 2000;71:287–298. Slaets E, Carmeliet G, Naert I, Duyck J. Early cellular responses in cortical bone healing around unloaded titanium implants: an animal study. J Periodontol. 2006;77:1015–1024. Traini T, Assenza B, San Roman F, et al. Bone microvascular pattern around loaded dental implants in a canine model. Clin Oral Investig. 2006;10:151–156. Wehrbein H, Merz BR, Hämmerle CH, Lang NP. Bone‐to‐implant contact of orthodontic implants in humans subjected to horizontal loading. Clin Oral Implants Res. 1998;9:348–353. Saito S, Sugimoto N, Morohashi T, et al. Endosseous titanium implants as anchors for mesiodistal tooth movement in the beagle dog. Am J Orthod Dentofacial Orthop. 2000;118:601–607. Melsen B, Lang N. Biological reactions of alveolar bone to orthodontic loading of oral implants. Clin Oral Implants Res. 2001;12:144–152. Cha JY, Pereira MD, Smith AA, et al. Multiscale analyses of the bone‐implant interface. J Dent Res. 2015;94:482–490. Meyer U, Joos U, Mythili J, et al. Ultrastructural characterization of the implant/bone interface of immediately loaded dental implants. Biomaterials. 2004;25:1959–1967. Berglundh T, Abrahamsson I, Lang NP, Lindhe J. De novo alveolar bone formation adjacent to endosseous implants. Clin Oral Implants Res. 2003;14:251–262. Cornelis MA, Vandergugten S, Mahy P, et al. Orthodontic loading of titanium miniplates in dogs: microradiographic and histological evaluation. Clin Oral Implants Res. 2008;19:1054–1062. Serra G, Morais LS, Elias CN, et al. Sequential bone healing of immediately loaded mini‐implants: histomorphometric and fluorescence analysis. Am J Orthod Dentofacial Orthop. 2010;137:80–90.

34 Vande Vannet B, Sabzevar MM, Wehrbein H, Asscherickx K. Osseointegration of miniscrews: a histomorphometric evaluation. Eur J Orthod. 2007;29:437–442. 35 Huja SS. Bone anchors – can you hitch up your wagon? Orthod Craniofac Res. 2015;18:109–116. 36 Kim HY, Kim SC. Bone cutting capacity and osseointegration of surface‐treated orthodontic mini‐ implants. Korean J Orthod. 2016;46:386–394. 37 Kim JS, Ahn JP, Kim YH, et al. Atomic layout of an orthodontic titanium mini‐implant in human tissue: insights into the possible mechanisms during osseointegration. Angle Orthod. 2019;89:292–298. 38 Zheng X, Sun Y, Zhang Y, et al. Implants for orthodontic anchorage: an overview. Medicine (Baltimore). 2018;97:e0232. 39 Dalessandri D, Salgarello S, Dalessandri M, et al. Determinants for success rates of temporary anchorage devices in orthodontics: a meta‐analysis (n > 50). Eur J Orthod. 2014;36:303–313. 40 Mohammed H, Wafaie K, Rizk MZ, et al. Role of anatomical sites and correlated risk factors on the survival of orthodontic miniscrew implants: a systematic review and meta‐analysis. Prog Orthod. 2018;19:36. 41 Alharbi F, Almuzian M, Bearn D. Miniscrews failure rate in orthodontics: systematic review and meta‐analysis. Eur J Orthod. 2018;40:519–530. 42 Papageorgiou SN, Zogakis I, Papadopoulos MA. Failure rates and associated risk factors of orthodontic miniscrew implants: a meta‐analysis. Am J Orthod Dentofacial Orthop. 2012;142:577–595.e7. 43 Chikazu D, Tomizuka K, Ogasawara T, et al. Cyclooxygenase‐2 activity is essential for the osseointegration of dental implants. Int J Oral Maxillofac Surg. 2007;36:441–446. 44 Bölükbasi N, Ersanli S, Basegmez C, et al. Efficacy of quick‐release lornoxicam versus placebo for acute pain management after dental implant surgery: a randomised placebo‐controlled triple‐blind trial. Eur J Oral Implantol. 2012;5:165–173. 45 Alissa R, Sakka S, Oliver R, et al. Influence of ibuprofen on bone healing around dental implants: a randomised double‐blind placebo‐controlled clinical study. Eur J Oral Implantol. 2009;2:185–199. 46 Sakka S, Hanouneh SI. Investigation of the effect of ibuprofen on the healing of osseointegrated oral implants. J Investig Clin Dent. 2013;4:113–119. 47 Luo JD, Miller C, Jirjis T, et al. The effect of non‐steroidal anti‐inflammatory drugs on the osteogenic activity in osseointegration: a systematic review. Int J Implant Dent. 2018;4:30. 48 Chappuis V, Avila‐Ortiz G, Araújo MG, Monje A. Medication‐related dental implant failure: systematic

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review and meta‐analysis. Clin Oral Implants Res. 2018;29:55–68. Cuairán C, Campbell PM, Kontogiorgos E, et al. Local application of zoledronate enhances miniscrew implant stability in dogs. Am J Orthod Dentofacial Orthop. 2014;145:737–749. Gelazius R, Poskevicius L, Sakavicius D, et al. Dental implant placement in patients on bisphosphonate therapy: a systematic review. J Oral Maxillofac Res. 2018;9:e2. Khan AA, Morrison A, Hanley DA, et al. International Task Force on Osteonecrosis of the Jaw. Diagnosis and management of osteonecrosis of the jaw: a systematic review and international consensus. J Bone Miner Res. 2015;30:3–23. Krishnan S, Pandian S, Kumar SA. Effect of bisphosphonates on orthodontic tooth movement‐an update. J Clin Diagn Res. 2015;9:ZE01–5. Bernhardsson M, Sandberg O, Aspenberg P. Anti‐RANKL treatment improves screw fixation in cancellous bone in rats. Injury. 2015;46:990–995. Boquete‐Castro A, Gómez‐Moreno G, Calvo‐Guirado JL, et al. Denosumab and osteonecrosis of the jaw. A systematic analysis of events reported in clinical trials. Clin Oral Implants Res. 2016;27: 367–375. Wu X, Al‐Abedalla K, Rastikerdar E, et al. Selective serotonin reuptake inhibitors and the risk of osseointegrated implant failure: a cohort study. J Dent Res. 2014;93:1054–1061. Chrcanovic BR, Kisch J, Albrektsson T, Wennerberg A. Is the intake of selective serotonin reuptake inhibitors associated with an increased risk of dental implant failure? Int J Oral Maxillofac Surg. 2017;46:782–788.

57 Deepa, Mujawar K, Dhillon K, Jadhav P, et al. Prognostic implication of selective serotonin reuptake inhibitors in osseointegration of dental implants: a 5‐year retrospective study. J Contemp Dent Pract. 2018;19:842–846. 58 Howie RN, Herberg S, Durham E, et al. Selective serotonin re‐uptake inhibitor sertraline inhibits bone healing in a calvarial defect model. Int J Oral Sci. 2018;10:25. 59 Bradaschia‐Correa V, Josephson AM, Mehta D, et al. The selective serotonin reuptake inhibitor fluoxetine directly inhibits osteoblast differentiation and mineralization during fracture healing in mice. J Bone Miner Res. 2017;32:821–833. 60 Schweiger JU, Schweiger U, Hüppe M, et al. The use of antidepressive agents and bone mineral density in women: a meta‐analysis. Int J Environ Res Public Health. 2018;15:E1373. 61 Chrcanovic BR, Kisch J, Albrektsson T, Wennerberg A. Intake of proton pump inhibitors is associated with an increased risk of dental implant failure. Int J Oral Maxillofac Implants. 2017;32:1097–1102. 62 Wu X, Al‐Abedalla K, Abi‐Nader S, et al. Proton pump inhibitors and the risk of osseointegrated dental implant failure: a cohort study. Clin Implant Dent Relat Res. 2017;19:222–232. 63 Hussain S, Siddiqui AN, Habib A, et al. Proton pump inhibitors’ use and risk of hip fracture: a systematic review and meta‐analysis. Rheumatol Int. 2018;38:1999–2014. 64 Nassar Y, Richter S. Proton‐pump inhibitor use and fracture risk: an updated systematic review and meta‐ analysis. J Bone Metab. 2018;25:141–151. 65 Andersen BN, Johansen PB, Abrahamsen B. Proton pump inhibitors and osteoporosis. Curr Opin Rheumatol. 2016;28:420–425.

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6 Mechanical Aspects of TADs Toru Deguchi and Do-Gyoon Kim Division of Orthodontics, College of Dentistry, The Ohio State University, Columbus, OH, USA

The mechanical properties of a temporary anchorage device (TAD) system are very important in determining its stability and ability to resist orthodontic force. In the past, various methodologies were introduced as reliable tools to assess the mechanical stability of TADs in bone, including insertion torque, removal torque, and stiffness [1–3]. As other methods became available in clinical settings, Periotest® and resonance frequency analysis (RFA) were used to assess the stability of dental implant systems [4–7]. By comparing different types of TADs with these analytical tools, useful information can be generated that identifies which factors of the TAD system are important in determining its mechanical stability.

6.1  ­Mechanical Analysis of TADs in Artificial Bone Because it is difficult to control in vivo conditions (i.e. differences in the quality and quantity of bone, soft tissue conditions, etc.), placing TADs in artificial bone can be used to eliminate variables that cannot be controlled with in vivo studies. Using this method we were able to examine each factor that influenced the mechanical properties of the different types of TADs. We compared various mechanical properties including insertion and removal torque (Figure  6.1a), static and dynamic stiffness (Figure  6.1b), clinical Periotest (Figure  6.1c), and RFA (Figure  6.1d) between two different types of TADs (tomas®, 1.6 × 6 mm; Dentaurum, Newtown, PA, USA; AbsoAnchor, 1.6 × 6 mm; Dentos, Daegu, South Korea) in different thicknesses (1.5, 2.0, and 3.0 mm) of artificial bone.

6.2  ­Insertion and Removal Torque The amount of torque needed to insert a TAD into bone is dependent on the axial force, the diameter of the screw, and friction on the surface of the screw thread [1–3]. An implant placement torque in the range of 5–10 N·cm is generally recommended [8]. However, this “ideal” torque may vary depending on the type of TAD. For instance, we found that it required significantly more torque to insert tomas screws (7–19 N·cm, depending on the bone thickness) and to remove them (4–13 N·cm) than to insert or remove Abso® screws (6–13 N·cm and 3–10 N·cm, respectively) (Table 6.1) [9]. This difference in torque is a result of the tapered shape of the tomas screws compared to the cylindrical shape of the Abso screws. Also, the region below the gingival collar of the tomas TADs is not completely threaded; it includes a solid part that provides more contact surface between the screw and bone. These results suggest that, given that the ideal torque is in the range of 5–10 N, pre-drilling in thick cortical bone may be required with tomas screws and that Abso screws might not be suitable for use in thin cortical bone.

6.3  ­Stiffness Values (Static Stiffness, Dynamic Stiffness, and Energy Dissipation) The static stiffness (K), dynamic stiffness (K*), and energy dissipation (tanδ) of a TAD system can be determined by loading a screw in a tangential direction, which is a more representative loading direction for clinical settings. The static stiffness accounts for the initial mechanical stability

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section I  Fundamental Perspectives on TADs

(a)

(b)

(d)

(e)

(c)

Figure 6.1  Images of how torque value (a) was measured. Instruments include SmartPeg attached on the miniscrew head (b) and loading machine (c) to mount artificial specimen. Images also show how Periotest (d) and RFA (e) were performed. Source: Han et al. [9]. Reprinted with permission.

of a TAD system when orthodontic force is applied to the TAD. The dynamic stiffness and tanδ are indications of the degree of integration at the interface between the bone and TAD. The results of static and dynamic stiffness and energy dissipation are presented in Table  6.1. Because tomas screws have a higher K value, this could indicate that they have more contact area and their diameter results in better resistance to tangential loading than do Abso screws. Although the K values of tomas screws were higher than those of Abso screws at the same torque level in thin bone blocks, the correlation slopes of the K values with insertion and removal torque were significantly different between the TAD groups. This indicates that the shape of the TADs had more effect in determining the TAD K values than did the torque values in thin bone. As tanδ has been used to assess the time-dependent energy dissipation behavior of a material, it can also be used as one of the indications for implant stability. Tomas screws have a higher mechanical stability and also higher tanδ values than Abso screws. This result may be caused by

the interfacial gap at the incomplete thread region below the gingival collar of the tomas miniscrew.

6.4  ­Periotest Value (PTV) PTVs are derived from the average contact time to the object [10]. Although PTVs are measured in the range of −8 to 50 for osseointegrated dental implants, TAD systems are assessed between 4 and 8. For dental implant systems, PTVs from −8.0 to 0 indicate that the implant system is ready for loading, whereas PTVs from 1.0 to 9.0 indicate that most implant systems are not quite ready to be loaded, and those over 10.0 suggest that the implant should not be loaded. In contrast with the PTVs of dental implants (−8 to 50), PTVs ranged between 4 and 8 for miniscrews [11]. These results indicate that PTV can be used to assess the relatively low stability of miniscrew systems due to their much smaller dimensions than the PTVs of dental implant ­systems. The Periotest device uses low-amplitude cyclic

Table 6.1  Comparison of maximum insertion torque (MIT), removal torque (RT), PTV, ISQ, static stiffness (K), dynamic stiffness (K*), and energy dissipation ability (tanδ) values between tomas and Abso miniscrews installed in artificial bone 1.5, 2.0, and 3.0 mm thick (mean ± standard deviation). Bone thickness (mm) Miniscrew types

1.5 Tomas

Abso

2.0 P-value

Tomas

Abso

3.0 P-value

Tomas

Abso

P-value

MIT (N·cm)

6.76 ± 0.07

5.76 ± 0.04

14 years of age) to reduce the severity of surgical movement or to reduce the need for two‐jaw surgery, but more samples are needed to evaluate the effectiveness of the treatment philosophy. Initial Final

Figure 20.3  Superimposition of the initial (red) and final (white mesh, showing dark blue color with black background)) CBCTs of a patient treated with BAMP. Note the protraction of the maxilla and midface as well as retraining of anterior mandibular growth.

20.3 ­Class III Treatment Philosophy When Class III malocclusion is detected early, RPHG has been shown to be effective at reducing the need for orthognathic surgery [28]. In patients older than 10 years old, the

Chapter 20  Dentofacial Orthopedics for Class III Corrections

Initial mm

–5

5

mm

Final

Figure 20.4  Color map showing superimposition of a patient treated with BAMP. Red signifies forward displacement at time two in that region, whereas blue shows distal displacement. Note the distalization of the condyle and ramus with the accompanying remodeling of the glenoid fossa. The profile soft tissue superimposition shows initially as orange and the final version as white mesh (showing dark blue color with black background). The superimposition shows forward growth and anterior displacement of the nose and midface.

effects of RPHG are primarily dentoalveolar with a higher relapse rate. From age 11 to 14, BAMP has been shown to be effective in protracting the maxilla and restraining mandibular growth. After 15, orthognathic surgery is often the

treatment of choice, especially when the malocclusion is severe. BAMP can be used to reduce the severity of the malocclusion and reduce the amount of surgical movement needed.

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7 Kim JH, Viana MA, Graber TM, et al. The effectiveness of protraction face mask therapy: a meta‐analysis. Am J Orthod Dentofacial Orthop. 1999;115:675–685. 8 Macdonald KE, Kapust AJ, Turley PK. Cephalometric changes after the correction of class III malocclusion with maxillary expansion/facemask therapy. Am J Orthod Dentofacial Orthop. 1999;116:13–24. 9 Takada K, Petdachai S, Sakuda M. Changes in dentofacial morphology in skeletal Class III children treated by a modified maxillary protraction headgear and a chin cup: a longitudinal cephalometric appraisal. Eur J Orthod. 1993;15:211–221. 10 Baccetti T, Franchi L, McNamara JA Jr. Treatment and posttreatment craniofacial changes after rapid maxillary expansion and facemask therapy. Am J Orthod Dentofacial Orthop. 2000;118:404–413. 11 Westwood PV, McNamara JA, Jr, Baccetti T, et al. Long‐term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances. Am J Orthod Dentofacial Orthop. 2003;123:306–320. 12 Baccetti T, Franchi L, McNamara JA Jr. Cephalometric variables predicting the long‐term success or failure of combined rapid maxillary expansion and facial mask therapy. Am J Orthod Dentofacial Orthop. 2004;126:16–22. 13 Wells AP, Sarver DM, Proffit WR. Long‐term efficacy of reverse pull headgear therapy. Angle Orthod. 2006;76:915–922. 14 Singer SL, Henry PJ, Rosenberg I. Osseointegrated implants as an adjunct to facemask therapy: a case report. Angle Orthod. 2000;70:253–262. 15 Enacar A, Giray B, Pehlivanoglu M, Iplikcioglu H. Facemask therapy with rigid anchorage in a patient with maxillary hypoplasia and severe oligodontia. Am J Orthod Dentofacial Orthop. 2003;123:571–577. 16 Hong H, Ngan P, Han G, et al. Use of onplants as stable anchorage for facemask treatment: a case report. Angle Orthod. 2005;75:453–460. 17 Kircelli BH, Pektas ZO. Midfacial protraction with skeletally anchored face mask therapy: a novel approach and preliminary results. Am J Orthod Dentofacial Orthop. 2008;133:440–449. 18 Kircelli BH, Pektas ZO, Uckan S. Orthopedic protraction with skeletal anchorage in a patient with maxillary

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hypoplasia and hypodontia. Angle Orthod. 2006;76:156–163. Cornelis MA, Scheffler NR, Mahy P, et al. Modified miniplates for temporary skeletal anchorage in orthodontics: placement and removal surgeries. J Oral Maxillofac Surg. 2008;66:1439–1445. De Clerck H, Cevidanes L, Baccetti T. Dentofacial effects of bone‐anchored maxillary protraction: a controlled study on consecutively treated Class III patients. Am J Orthod Dentofacial Orthop. 2010;138:577–581. Cevidanes L, Baccetti T, Franchi L, et al. Comparison of two protocols for maxillary protraction: bone anchors versus face mask with rapid maxillary expansion. Angle Orthod. 2010;80:799–806. Nguyen T, Cevidanes LHS, Cornelius MA, et al. 3D assessment of maxillary changes associated with bone anchored maxillary protraction. Am J Orthod Dentofacial Orthop. 2011;140:790–798. Liu S, Kyung H, Buschang P. Continuous forces are more effective than intermittent forces in expanding sutures. Eur J Orthod. 2010;32:371–380. De Clerck H, Nguyen T, de Paula LK, Cevidanes L. Three‐dimensional assessment of mandibular and glenoid fossa changes after bone‐anchored Class III intermaxillary traction. Am J Orthod Dentofacial Orthop. 2012;142:25–31. Alexander AE, McNamara JA Jr, Franchi L, Baccetti T. Semilongitudinal cephalometric study of craniofacial growth in untreated Class III malocclusion. Am J Orthod Dentofacial Orthop. 2009;135:700.e1–14. Yatabe M, Faco R, Garib D, et al. BAMP therapy in unilateral complete cleft lip and palate: a 3D assessment of the maxillary effects. Am J Orthod Dentofacial Orthop. 2017;152:327–335. Yatabe M, Faco R, Garib D, et al. Mandibular and glenoid fossa changes after BAMP therapy in patients with UCLP: a 3D preliminary assessment. Angle Orthod. 2017;87:423–431. Anne Mandall N, Cousley R, DiBiase A, et al. Is early class III protraction facemask treatment effective? A multicentre, randomized, controlled trial: 3‐year follow‐up. J Orthod. 2012;39:176–185.

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21 TAD-anchored Maxillary Protraction Dong-Hwa Chung Department of Orthodontics, College of Dentistry, Dankook University, Cheonan, South Korea

21.1 ­Introduction Class III malocclusion is one of the most difficult orthodontic problems in growing patients because the amount and direction of mandibular growth is unpredictable. The nature of this malocclusion comes from heterogeneity, which makes it very complex to predict the final conditions. Outcome predictors of Class III orthopedic treatment with conventional maxillary protraction have been studied, and although posterior face height and ramus dimension are suggested as predictors [1, 2], a universal predictor for Class III orthopedic treatment is still lacking [3]. Factors contributing to the prognosis may include not only skeletal factors, but also functional factors such as airway, hyoid bone position, and alveolar housing [4]. In spite of the difficulty, orthodontists must continue to care for the patient until he or she has stopped growing. Orthodontists might then have to explain why a patient needs surgical intervention in some cases after the end of growth. If an orthodontist finishes a patient before he or she is fully grown, this would be “immature finishing” due to the remaining mandibular growth, which can substantially affect the result of treatment during the retention period. The mandible can end up being larger and worse off than it was before treatment. Some orthodontists might try to fix the ongoing problem with a fixed appliance as the patient goes through their pubertal growth change. However, solving skeletal discrepancy with only fixed appliances might frustrate the patient and his or her parents, who have already invested their time, money, and effort while the mandible keeps changing its size. Furthermore, the total treatment time will be extended. A longer treatment time is associated with more problems [5]. Maxillary protraction is usually implemented during mixed dentition or early permanent dentition since ­maxillary growth slows before the peak pubertal growth [6].

After the peak of pubertal growth, maxillary protraction with dental anchorage results in more dentoalveolar effects rather than skeletal advancement [6]. Changes in the maxilla due to maxillary protraction during peak pubertal growth was just 2.71 mm (0.59 mm in control) [7], whereas combined mandibular growth [cervical vertebral maturation stage (CVMS) 5 and 6] was 7.09 mm [8]. Some studies including randomized clinical trials on the long‐term stability of conventional maxillary protraction have revealed that the effect of this appliance will disappear when patients grow during puberty [9–11]. Sugawara et al. [10] have also shown that the final skeletal characteristics were similar in a monozygotic twin study comparing one‐phase vs. two‐phase treatment. Therefore, the effect of orthopedic treatment must be strong enough to maintain the skeletal changes through the pubertal growth stage and protraction of the maxilla should be continued until growth has decelerated.

21.2 ­TAD-anchored Maxillary Protraction The conventional tooth‐borne maxillary protraction method is an efficient way to move the maxilla downward and forward. However, conventional maxillary protraction not only tends to return to its original phenotype, it also has harmful dentoalveolar effects including proclination of the maxillary anteriors, extrusion and mesial movement of the maxillary first molars, and opening of the mandibular plane since the anchorage system is set on teeth, not on a bony structure. Conventional maxillary protraction can result in counterclockwise rotation of the posterior maxilla and maxillary molars, thus causing downward and backward rotation of the mandible. This lengthens the vertical facial height, accompanied by subsequent horizontal

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

192

Section II  Three-dimensional Correction with TADs

­ andibular growth that could cause relapse of an antem rior crossbite [12–14]. Since mandibular rotation could accelerate the open‐bite tendency of the vertical facial type, it is not recommended for Class III patients with a high angle type. To eliminate such tendencies with maxillary protraction, attempts have been made to apply force in various locations [15, 16]. However, it seems that maxillary rotation cannot be prevented by changing the point of action with intraoral devices [16]. Furthermore, using a higher extraoral traction arm as a modified design is not feasible in a clinical environment either, because it is too bulky. The introduction of temporary anchorage devices (TADs) into orthodontics has changed classical orthodontic mechanics because now orthodontists can implement a skeletal anchorage that can resist any kind of orthodontic movement or directly produce real orthopedic force on a target area. This real orthopedic mechanism helps to decrease dental side effects significantly and produces pure skeletal changes. TAD‐anchored maxillary protraction prevents proclination of maxillary anteriors and opening of the mandibular plane [17]. In several studies on skeletal‐ anchored maxillary protraction, linguoversion of the maxillary anteriors has been observed [18–21]. TAD‐anchored maxillary protraction impacts five main areas of favorable change: A‐point, orbitale, gonial angle, nasal angle, and a possible contribution to condylar change. The advancement of A‐point, orbitale, and nose comes from pure maxillary protraction. A decrease in gonial angle and posterior remodeling of articular fossa are related to the chin cap effect of TAD maxillary protraction because force is applied constantly. How much of an orthopedic effect can be achieved with conventional or TAD‐anchored maxillary protraction? A systemic review of conventional maxillary protraction has shown that average skeletal changes are: SNA, 1.79°; SNB, −1.16°; and ANB, 2.92° [22]. Meanwhile, skeletal anchorage with TADs can produce about twice as much advancement of maxillary basal bone compared to conventional maxillary protraction: SNA, 2.70°; SNB, −3.07°; and ANB, 6.07° [23]. Also, with TAD‐anchored maxillary protraction, there is a greater advancement of the orbitale, which might improve the appearance of the facial dish. We can assume that the skeletal effect on maxilla from TAD‐anchored maxillary protraction happens not only in the lower part of the maxilla (A point), but also in the upper part of the maxilla (orbitale) [20, 21]. The counterclockwise rotation of the mandibular plane after TAD‐anchored maxillary protraction has been reported in some studies [18, 19]. Koh and Chung [17] found that the high‐angle skeletal anchorage group showed significantly more closure of the mandibular plane and removed the tendency to produce an open

bite compared to the conventional maxillary protraction group. TAD‐anchored maxillary protraction causes forward movement of the maxilla while restraining advancement of the chin. De Clerck et al. [24] has stated that the large variability of chin positions can be explained by four factors: (i) the amount and direction of condylar growth, (ii) bone remodeling in the articular fossa, (iii) rotation of the mandible, and (iv) closure or opening of the gonial angle. Although orthodontists cannot control the amount or the direction of condylar growth, it seems that TAD‐anchored maxillary protraction might change the shape of the mandible by acting as a chin cup [25]. Bone remodeling of the glenoid fossa and closure of the gonial angle due to the chin‐cup effect contributes to a favorable chin position in the sagittal plane. Although the mandibular growth patterns were similar in the skeletally anchored maxillary protraction group and untreated control group, there was a 2.7 mm difference in chin position between the two groups due to the chin‐cup effect [26]. This study also reported the reduction of the gonial angle by 4.1° compared with the control group [26]. The chin position was correlated with the position of ramus. Since the sagittal change in the ramus was larger than the positional change of the condyles, the decrease of the gonial angle could be the reason for the above difference [24]. Both closure of the gonial angle and swing‐back of the ramus can prevent advancement of the chin position [27]. A 3D assessment of the articular fossa of the TAD‐ anchored maxillary protraction showed bone apposition at the anterior eminence of the temporomandibular joint and bone resorption of the posterior wall of the articular eminence [24]. Since this study did not include cone‐beam computed tomography (CBCT) data from the control group (untreated Class III), we were unable to determine whether this phenomenon was due to normal growth or TAD‐ driven maxillary traction. Additional evidence‐based studies are needed regarding this matter.

21.3  ­Types of TAD-anchored Maxillary Protraction There are four different types of TAD‐anchored maxillary protraction which depend on the location of the TADs and the traction method: TADs on the zygomatic buttress, TADs for intraoral traction (Bollard plate, face corrector: Figure 21.1a), TADs on the lateral nasal wall (Figure 21.1b), and TADs on the palate (hybrid hyrax: Figure  21.1c). Recently, palatal plates have also been introduced (Figure  21.1d) [29]. For typical extraoral traction with TADs, the apertura piriformis (lateral nasal wall of the

Chapter 21  TAD-anchored Maxillary Protraction

(a)

(b)

(c)

(d)

Figure 21.1  (a) Intraoral traction. Miniplates of the maxillary arch are located on the infrazygomatic crest. For mandibular arch, mandibular symphysial areas are an ideal location for miniplates. (b) Lateral nasal wall (apertura piriformis). This is proper location for TAD anchorage since it is located anterior to the center of the nasomaxillary complex along the line of action from the center of resistance of the maxilla with easy access for both surgical approach and elastics. (c) Hybrid hyrax. This is a hybrid type with conventional expander type attached to TADs [28]. Source: Ngan et al. [28]. Reprinted with permission. (d) Palatal plate. Main structure is a metal framework attached to TADs without expander [29]. Source: Kook et al. [29]. Reprinted with permission.

maxilla) and cortical bony surface of the zygomatic buttress can be used as a location for TAD anchors. The lateral nasal wall is a proper location for TAD anchorage since it is located anterior to the center of the nasomaxillary complex and along the line of action from the center of resistance of the maxillae. It also provides easy access for both the surgical approach and wearing of elastics. However, this lateral nasal wall location should not be used in children at early mixed dentition stage due to possibility of interrupting canine eruption. If an unerupted canine is positioned deep inside the maxilla, tooth damage may result if screws come in contact with the canine follicle. Although the zygomatic buttress can be used for children in the early mixed dentition stage, TADs applied on the zygomatic buttress might not produce as much counterclockwise rotation of the mandibular plane as would intraoral maxillary traction (Table 21.1). The intraoral maxillary traction method is convenient to use on young patients. It also produces good skeletal effects

because orthopedic force is applied continuously and patient compliance is not a factor. Table  21.1 shows not only the greater improvement of A‐point, but also a significant decrease of the gonial angle with the intraoral maxillary protraction method. The Bollard miniplate (Tita‐Link, Brussels, Belgium) and face corrector (Jeil Medical, Seoul, South Korea) are commercial product lines for this method. There are two separate TAD locations for intraoral maxillary traction: the symphysial area and the infrazygomatic crest area. TADs placed in the symphysis region are quite stable because the cortical bone is relatively thick and strong [34, 35]. In addition, visual access to this area is better than in any other area. Although the zygoma has enough bone thickness compared to the maxilla, inflammation in the paranasal sinus might influence anatomic features in the cortical bone. Furthermore, the narrow width of the attached gingival in the infrazygomatic arch area may be a critical factor since it might result in irritation, inflammation, or infection that

193

Table 21.1 Comparison of four different types of TAD-anchored maxillary protraction and conventional tooth-borne maxillary protraction. Tooth-borne Koh [17]

Sample number

24

Zygomatic buttress Lee [20]

10

Elnagar [30]

10

Lateral nasal wall Sar [18]

15

Sar [31]

17

Intraoral traction

Koh [17]

19

A Perp (mm)

1.75

3.18

4.87

2.83

3.11

2.87

SNA (°)

1.82

2.73

4.78

2.53

3.14

−1.93

SNB (°)

−1.10

−0.77

−1.21

ANB (°)

2.95

3.81

5.99

Mn pl angle (°)

1.86

1.40

2.03

−0.66

−3.20

Gonial angle (°) SNOr (°) Suppl method

1.90

2.78

1.46

Cevidanes [19]

21

10

Ngan [28]

20

Nienkemper [32]

16

Maino [33]

28

5.81

1.54

1.90

3.40

2.25

5.65

1.59

2.00

2.50

−2.44

−1.28

−0.39

−0.80

−1.40

−0.92

5.52

3.31

6.04

2.40

3.40

3.41

1.29

0.17

−0.80

−0.98

0.24

0.40

1.64

−2.60

−4.18

2.49

5.20

Elnagar [30]

Hybrid hyrax

−1.90

3.27 Alt‐ RAMEC

A Perp, Distance between A point and either S perpendicular line or N perpendicular line; SNA, sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; Mn plane angle, angle between sella‐nasion plane and mandibular plane; Gonial angle (Ar‐Go‐Me), articulare‐gonion‐menton; SNOr, sella‐nasion‐orbitale; Suppl method, supplement method other than maxillary protraction.

Chapter 21  TAD-anchored Maxillary Protraction

age is a critical factor. TAD failures are reportedly more common in younger patients [36, 37]. The hybrid hyrax is a new maxillary protraction method using a modified TAD‐anchored rapid palatal expander. It has been suggested that it has similar skeletal effects to that of other TAD‐anchored maxillary protraction with lower surgical invasiveness [14]. Skeletal effects from the hybrid hyrax are less than those with other TAD maxillary protraction methods unless they are used with the Alt‐RAMEC technique (Table  21.1). The difference may be due to the fact that other TAD appliances use the TADs directly as the traction point to which an elastic is applied, but the distance from the traction hook to the implant site is quite long with the hybrid hyrax since the traction arms are long stainless wires that start from the maxillary first molar and are soldered to the rapid maxillary expansion appliance. Figure 21.2  CBCT image of infrazygomatic crest with miniplate. The CBCT image shows that the bony support in that area is not sufficient to support the miniplate. Due to the short posterior alveolar height during late mixed dentition, the miniplate screws might contact the root of maxillary molars. The location of the dental follicle of the maxillary second molar makes the quality of the cortical bone below the infrazygomatic crest weaker than in other places.

in turn can result in failure of the TAD screws. Especially before the eruption of maxillary second molars, the roots are located right below in the infrazygomatic crest (Figure  21.2). Therefore, the cortical bone in that area becomes thinner and is weaker than the lateral nasal wall [34, 35]. Although TAD success rates are quite high, patient

21.4 ­Conclusion The overall skeletal effects of four TAD‐anchored maxillary traction methods are clearly superior to results obtained with conventional tooth‐borne maxillary traction. Among them, the intraoral maxillary traction method reported more favorable skeletal changes, including a greater advancement of both A point and orbitale and a greater reduction in the gonial angle. However, the placement of miniplates for intraoral traction needs great care, especially in the infrazygomatic crest area. Although TAD‐ anchored maxillary traction has a stronger skeletal effect than conventional treatment, protraction of the maxilla should be continued until the deceleration stage of growth due to late mandibular growth.

Case 21.1  Skeletal Class III with Severe Maxillary Hypoplasia and High Angle Type Diagnosis

Treatment Alternatives

An 11-year-old boy presented with a chief complaint of anterior crossbite. There were a couple of contributing factors such as allergic rhinitis and mouth breathing with a constricted maxillary dental arch. However, premature contact on his anteriors was not a dental fractional factor. Although his skeletal age was before the growth acceleration stage, his panoramic x-ray image showed late mixed dentition. He showed severe maxillary retrusion with a hyperdivergent skeletal pattern. All anteriors on his maxilla were in an upright position whereas all anteriors on his mandible were retroclined lingually, indicating a true skeletal Class III pattern (Figure 21.3).

The original treatment option was two-jaw surgery after the patient has reached his full growth potential. Camouflage treatment was not considered to be a viable option due to his severe skeletal Class III pattern, but his parents requested this alternative and chose a camouflage treatment plan with TAD-anchored maxillary protraction. We warned them that because their son already exhabited typical features of skeletal Class III there was no guarantee that the treatment would be successful. Treatment Progress Two TADs with surgical miniplates (Jeil Medical, Seoul, South Korea) were installed on each side of the lateral (Continued )

195

(a)

(b)

(c)

(d)

Figure 21.3  Case 21.1: (a) Pre-treatment photographs. (b) Photographs after six months of maxillary protraction. (c) Photographs after 12 months of maxillary protraction. (d) Post-treatment photographs.

(a)

(b)

nasal wall of the maxilla. Maxillary protraction was implemented for 18 months with a Delair type facemask which was worn full-time. Although the patient still exhibited a negative overjet, his facial profile showed some improvement after six months of treatment. After 12 months of TAD-driven maxillary protrac-

Figure 21.4  Case 21.1: Lateral cephalograms. (a) Pre-treatment; (b) Post-treatment.

tion, he displayed a positive overjet with a normal profile. Upon completion of the maxillary protraction after 18 months of treatment, his profile even showed a typical Class II skeletal pattern. Total treatment time was 36 months, including fixed appliance treatment (Figures 21.3 and 21.4).

Chapter 21  TAD-anchored Maxillary Protraction

Pre-treatment Post-treatment

Table 21.2  Case 21.1: Cephalometric measurements. Pretreatment

Posttreatment

Difference

71.5

71.7

0.2

C

Body length (mm) E

B

A D

Figure 21.5  Case 21.1: Cephalometric superimposition. Five main areas of favorable change from TAD-anchored maxillary protraction: A point (A), orbitale (B), nasal angle (C), gonial angle (D), and possible contribution of condylar change (E). The advancement of A point and orbitale and nose comes from pure maxillary protraction. Decrease of gonial angle and possible posterior remodeling of articular fossa are related to the chin-cup effect of TAD maxillary protraction because the force is applied full-time.

Treatment Results After treatment, the patient had a positive overjet with Class I canine and molar relationship and a decent profile. The superimposition of treatment changes showed posterior displacement of his condyle, a swing-back of his ramus with a downward movement of his palate, closure

Ramus height (mm)

43.2

50.8

7.6

A‐Nperp (mm)

−4.8

−2.4

2.4

SNOr (°)

57.1

61.3

4.2

SNA (°)

70.2

72.5

2.3

SNB (°)

76.8

74.1

−2.7

ANB (°)

−5.9

−1.6

4.3

Gonial angle (°)

137.1

131.0

−6.1

Mandibular plane angle (°)

42.6

43.0

0.4

Nasal angle (°)

85.9

82.2

−3.7

SN‐Pog (°)

77.4

73.6

−3.8

Body length, Distance between menton and gonion; Ramus height, distance between articulare and gonion; A‐Nperp, distance between A point and N perpendicular line; SNOr, sella‐nasion‐orbitale; SNA, sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐ nasion‐B point; Gonial angle (Ar‐Go‐Me), articulare‐gonion‐ menton; Mandibular plane angle, angle between sella‐nasion plane and mandibular plane; Nasal angle, S‐N‐N1 (the most anterior and inferior point of the nasal bone); SN‐Pog, sella‐nasion‐pogonion.

of the gonial angle, anterior displacement of the A point, advancement of his orbitale, and an increase in nasal angle. The skeletal effect of TAD-anchored maxillary protraction came from anterior displacement of his maxillary body and a favorable change in the shape of his mandibular body to maintain the anteroposterior position of his chin (Figure 21.5, Table 21.2).

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5 Pinskaya YB, Hsieh TJ, Roberts WE, Hartsfield JK. Comprehensive clinical evaluation as an outcome assessment for a graduate orthodontics program. Am J Orthod Dentofacial Orthop. 2004;126:533–543. 6 Cha KS. Skeletal changes of maxillary protraction in patients exhibiting skeletal class III malocclusion: a comparison of three skeletal maturation groups. Angle Orthod. 2003;73:26–35. 7 Pangrazio‐Kulbersh V, Berger JL, Janisse FN, Bayirli B. Long‐term stability of Class III treatment: rapid palatal expansion and protraction facemask vs LeFort I maxillary advancement osteotomy. Am J Orthod Dentofacial Orthop. 2007;131:7.e9–7.19. 8 Ball G, Woodside D, Tompson B, et al. Relationship between cervical vertebral maturation and mandibular growth. Am J Orthod Dentofacial Orthop. 2011;139:e455–e461.

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Section II  Three-dimensional Correction with TADs

9 Mandall N, Cousley R, DiBiase A, et al. Early class III protraction facemask treatment reduces the need for orthognathic surgery: a multi‐centre, two‐arm parallel randomized, controlled trial. J Orthod. 2016;43:164–175. 10 Sugawara J, Aymach Z, Hin H, Nanda R. One‐phase vs 2‐phase treatment for developing Class III malocclusion: a comparison of identical twins. Am J Orthod Dentofacial Orthop. 2012;141:e11–22. 11 Westwood PV, McNamara JA Jr., Baccetti T, et al. Long‐term effects of Class III treatment with rapid maxillary expansion and facemask therapy followed by fixed appliances. Am J Orthod Dentofacial Orthop. 2003;123:306–320. 12 Lee DY, Kim ES, Lim YK, Ahn SJ. Skeletal changes of maxillary protraction without rapid maxillary expansion. Angle Orthod. 2010;80:504–510. 13 Wellsa AP, Sarverb DM, Proffit WR. Long‐term efficacy of reverse pull headgear therapy. Angle Orthod. 2006;76:915–922. 14 Ngan PW, Hagg U, Yiu C, Wei SH. Treatment response and long‐term dentofacial adaptations to maxillary expansion and protraction. Semin Orthod. 1997;3:255–264. 15 Kokich VG, Shapiro PA, Oswald R, et al. Ankylosed teeth as abutments for maxillary protraction: a case report. Am J Orthod. 1985;88:303–307 16 Spolyar JL. The design, fabrication and use of full‐ coverage bonded rapid maxillary expansion appliance. Am J Orthod. 1984;86:136–145. 17 Koh SD, Chung DH. Comparison of skeletal anchored facemask and tooth‐borne facemask according to vertical skeletal pattern and growth stage. Angle Orthod. 2014;84:628–633. 18 Sar C, Arman‐Özçırpıcı A, Uçkan S, Yazıcı AC. Comparative evaluation of maxillary protraction with or without skeletal anchorage. Am J Orthod Dentofacial Orthop. 2011;139:636–49. 19 Cevidanes L, Baccetti T, Franchi L, et al. Comparison of two protocols for maxillary protraction: bone anchors versus face mask with rapid maxillary expansion. Angle Orthod. 2010;80:799–806. 20 Lee NK, Yang IH, Baek SH. The short‐term treatment effects of face mask therapy in Class III patients based on the anchorage device: miniplates vs rapid maxillary expansion. Angle Orthod. 2012;82:846–852. 21 Cha BK, Lee NK, Choi DS. Maxillary protraction treatment of skeletal Class III children using miniplate anchorage. Korean J Orthod. 2007;37:73–84. 22 Lin Y, Guo R, Hou L, Fu Z, Li W. Stability of maxillary protraction therapy in children with Class III malocclusion: a systematic review and meta‐analysis. Clin Oral Investig. 2018;22:2639–2652. 23 Rodriguez de Guzman‐Barrera J, Saez Martinez C, Boronat‐Catala M, et al. Effectiveness of interceptive treatment of class III malocclusions with skeletal anchorage: a systematic review and meta‐analysis. PLoS One 2017;12:e0173875.

24 De Clerck H, Nguyen T, de Paula LK, Cevidanes L. Three‐dimensional assessment of mandibular and glenoid fossa changes after bone‐anchored Class III intermaxillary traction. Am J Orthod Dentofacial Orthop. 2012;142:25–31. 25 Mimura H, Deguchi T. Morphologic adaptation of temporomandibular joint after chincup therapy. Am J Orthod Dentofacial Orthop. 1996; 110:541–546. 26 De Clerck H, Cevidanes L, Baccetti T. Dentofacial effects of bone‐anchored maxillary protraction: a controlled study of consecutively treated Class III patients. Am J Orthod Dentofacial Orthop. 2010; 138:577–581. 27 Nguyen T, Cevidanes L, Paniagua B, et al. Use of shape correspondence analysis to quantify skeletal changes associated with bone‐anchored Class III correction. Angle Orthod. 2014;84:329–336. 28 Ngan P, Wilmes B, Drescher D, et al. Comparison of two maxillary protraction protocols: tooth‐borne versus bone‐ anchored protraction facemask treatment. Prog Orthod. 2015;16:26. 29 Kook YA, Bayome M, Park JH, et al. New approach of maxillary protraction using modified C‐palatal plates in Class III patients. Korean J Orthod. 2015;45:209–214. 30 Elnagar MH, Elshourbagy E, Ghobashy S, et al. Comparative evaluation of 2 skeletally anchored maxillary protraction protocols. Am J Orthod Dentofacial Orthop. 2016;150:751–762. 31 Sar C, Sahinoğlu Z, Özçirpici AA, Uçkan S. Dentofacial effects of skeletal anchored treatment modalities for the correction of maxillary retrognathia. Am J Orthod Dentofacial Orthop. 2014;145:41–54. 32 Nienkemper M, Wilmes B, Franchi L, Drescher D. Effectiveness of maxillary protraction using a hybrid hyrax‐facemask combination: a controlled clinical study. Angle Orthod. 2015;85:764–770. 33 Maino G, Turci Y, Arreghini A, et al. Skeletal and dentoalveolar effects of hybrid rapid palatal expansion and facemask treatment in growing skeletal Class III patients. Am J Orthod Dentofacial Orthop. 2018;153:262–268. 34 Chung DH, Dechow PC. Elastic anisotropy and off‐axis ultrasonic velocity distribution in human cortical bone. J Anat. 2011;218:26–39. 35 Peterson J, Wang Q, Dechow PC. Material properties of the dentate maxilla. Anat Rec A Discov Mol Cell Evol Biol. 2006;288:962–972. 36 De Clerck EE, Swennen GR. Success rate of miniplate anchorage for bone anchored maxillary protraction. Angle Orthod. 2011;81:1010–1013. 3 7 Cornelis MA, Scheffler NR, Nyssen‐Behets C, et al. Patients’ and orthodontists’ perceptions of miniplates used for temporary skeletal anchorage: a prospective study. Am J Orthod Dentofacial Orthop. 2008;133:18–24.

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22 Protraction Headgear with Surgical Miniplates Bong‐Kuen Cha Department of Orthodontics, College of Dentistry, Gangneung‐Wonju National University, Gangneung, South Korea

22.1 ­Introduction Class III malocclusion is one of the most difficult dysgnathia to diagnose properly and treat effectively. Because of its diverse individual phenotype, the traditional categorization, “maxillary deficiency or mandibular prognathism,” does not portray the detail of this malocclusion. Previously, orthognathic surgery was the only option for true mandibular prognathism or midface deficiency. However, if it was performed without considering etiology, relapse could be a problem [1]. In addition, the surgical option imposed a psychological and financial burden on the patient. Why was orthognathic surgery inevitable for skeletal Class III malocclusion? It is well known that genetics influences temporomandibular joint (TMJ) development and growth. Genetic factors such as Runx2, Sox9, and members of the TGF‐β/BMP family are thought to be critical drivers of chondrogenesis during condylar cartilage morphogenesis [2]. Such theories or classical hypotheses have certainly exerted a tremendous influence on the clinical decision‐making for treatment of Class III malocclusion. In the 1960s, Moss proposed a functional matrix theory against genetic influence [3]. It asserts that the growth of bone is always a secondary and compensatory response to a prior event in non‐skeletal tissue. More recently, an interesting study [4] has suggested that mechanical stress applied to the spheno‐occipital synchondrosis (SOS) may elicit Cbfa1 and VEGF expression. This could play a role in the growth of the SOS. Such research could have considerable clinical implications if it is found possible to control bone growth by changing the environment surrounding the bone in a growing patient. This chapter attempts to fill in some gaps in recent scholarly exploration and clinical practice by briefly outlining the treatment results for one growing patient with Class III malocclusion.

When surgical miniplates are used as anchorage for the protraction force, the maxillary complex moves forward without apparent mesial movement of the maxillary incisors and molars. Such an effect can be much more pronounced when protraction is used together with distalizing appliances such as a pendulum appliance. It is even possible to distalize the entire maxillary dentition in conjunction with such appliances. The maxillary molars are able to extrude more with RME protraction than with SAS protraction. However, it is quite difficult to differentiate buccal cusps from palatal cusps of maxillary molars bilaterally in a lateral cephalogram. To measure the amount of extrusion of the palatal cusps of maxillary molars as functional cusps more accurately, 3D digital model superimposition technology as introduced by our team can be used [25, 26]. Slavicek [27] made an important statement that the growth of the lower face is guided by the function of the occlusal plane. In other words, the pattern of mandibular growth is closely related to changes in the spatial ­position and inclination of the maxillary occlusal plane, which again is strongly influenced by extrusion of the maxillary molars. If this is true, it means that the decreased maxillary molar extrusion with SAS protraction might be an effective means to induce favorable mandibular growth. Fränkel and Fränkel [28] have suggested that in the presence of a diminished lingual volume, there might be a tendency for the tongue to change its postural position lower, leading to protective reflex altering the mandibular postural position anteriorly. It should be pointed out that in treatment of mandibular protrusion, it is a serious mistake to use appliances that diminish lingual volume. Normal tongue posture is pivotal to midface growth. As reported in an animal study by Petrovic et  al. [29], the stimulating effect of an intact tongue on the forward growth of the upper jaw should be considered. The lack

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

Section II  Three-dimensional Correction with TADs

Case 22.1  Pre-treatment (9Y 0M) CVMS 3

15 Height Increase (cm/year)

200

10

9.7 8.2

5

6.6

7.3

1.0

0 8

9

10

11

12

0.7

13

Age (years)

Figure 22.1  Case 22.1: Somatogram and CVMS of the patient at pre-treatment.

Figure 22.2  Case 22.1: Pre-treatment photographs.

A nine‐year‐old female presented to Gangneung‐Wonju National University Orthodontic Clinic with the chief complaint of an anterior crossbite. Based on her cervical vertebral maturation stage (CVMS) and a somatogram, it was estimated that she was in a pubertal growth spurt (Figure 22.1). Clinically, she had a concave profile with a marked midface deficiency (Figure 22.2). Her nasolabial angle was obtuse and her upper lip was a bit short compared with the commissure line. Lateral cephalometic radiograph showed a skeletal malocclusion with mandibular prognathism (ANB, −1.6°) but she had a normal mandibular plane angle and her SNA or A‐N perpendicular was within the normal range. Her maxillary incisor was slightly proclined (U1–FH, 118.2°) whereas her mandibular incisor was slightly proclined (IMPA, 83°) (Table 22.1).

Chapter 22  Protraction Headgear with Surgical Miniplates

Table 22.1  Pre-treatment, post‐SAS protraction, and post‐treatment cephalometric analysis. Pre-treatment

Protraction

Post‐treatment

(9 yr 0 mo)

(10 yr 2 mo)

(14 yr 3 mo)

SNA (°)

83.4

86.6

87.1

SNB (°)

85.0

83.9

84.0

ANB (°)

−1.6

2.7

3.1

SNO (°)

67.0

72.0

71.5

A-N perpendicular line (mm)

1.7

5.5

4.2

116.2

120.0

126.2

Midfacial length (mm)

84.6

88.7

92.0

Mandibular plane angle (°)

27.9

29.9

31.3

U1‐FH (°)

118.2

118.3

114.6

IMPA (°)

83.0

82.7

88.8

AB‐MP (°)

57.4

63.0

63.6

Mandibular length (mm)

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; SNO, sella‐ nasion‐orbitale; A-N perpendibular line, distance of A point to nasion perpendicular line; Mandibular length, condylion to pogonion; Midfacial length, condylion to A point; Mandibular plane angle, FH plane to mandibular plane; U1‐FH, maxillary central incisor to FH plane; IMPA, incisor mandibular plane angle; AB‐MP, AB line to mandibular plane.

The treatment plan consisted of a Phase 1 ­orthopedic protraction of the maxilla with a surgical miniplate [5, 6]. Some argue that protracting the maxilla might emerge from the contradiction between the normal measurement of SNA and the clinical impression. This point will be examined further in the case discussion section. Treatment Procedure Placement of miniplates and surgical screws is important to the success of orthopedic protraction. Detailed surgical procedures have been well documented in the literature [5, 6]. Maxillary protraction was started one week after the placement of miniplates. The patient wore protraction headgear (300–400 g per side) for about 12–14 hours per day. After 12 months of treatment, a Class II end‐on molar relationship was established with good patient compliance (Figure 22.3). Figure 22.4 shows the superimposition of cephalometric and 3D cone‐beam computed tomography (CBCT) images before and after treatment. After the active treatment, she wore protraction headgear just at nighttime, but it was hard to get patient cooperation. Sometime later, a follow‐up examination was done to evaluate whether her malocclusion could be camouflaged by orthodontic treatment. Progress records showed favorable growth between the maxilla

and mandible so the orthodontic camouflage treatment was decided. She was treated with fixed appliances for 18 months to establish a good molar relationship (Figure 22.5). Results and Case Discussion There is some controversy about using protraction headgear with miniplates when the SNA measurements are normal in pre-treatment lateral cephalometric analysis. With respect to this argument, Moyers gives a convincing answer [7]. His ideas about requisites for individual measurements in lateral cephalometric analysis can be summarized as follows: ●● ●●

●●

●●

Ideals are neither norm nor mean. One should know how the value changes with age, sex, and ethnic group. Measurements that are esthetic objectives should be explained as to their origins and clinical application. The norm is properly constructed as a range, not a single value. A point measurement is consistently misleading, especially during the maxillary incisor eruption and position.

We need to compensate for the weakness of the SNA interpretation. More elaborate parameters, such as midface (Continued)

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Figure 22.3  Case 22.1: Progress photographs after 12 months of treatment with protraction headgear.

length and length of the anterior or posterior cranial base, are useful, but I would like to simply focus on the extraoral appearance of the patient. In many Class III patients, deficient malar and midfacial projection leaves soft tissues poorly supported, resulting in premature lower lid and cheek descent as well as visible bags [8]. Although orthodontic treatment does not directly alter malar global relationship, the balance between dentoalveolar and malar support has significant influence on the nasal base–lip contour.

Despite keen insight by the great orthodontic teacher and researcher, another key question still remains, “Should we protract the maxilla during growth period or just wait till the end of the growth and do surgery?” Considering the stronger advancing effect of the infraorbital region by a skeletal anchorage system (SAS) protraction headgear compared to conventional protraction headgear [5] and considering that the orthodontic treatment goal is not only to achieve occlusal rehabilitation, but also to improve patient facial esthetics and thus

Chapter 22  Protraction Headgear with Surgical Miniplates

(a)

(b)

Pre-treatment

Pre-treatment

Post-treatment

Post-treatment

Figure 22.4  Case 22.1: Superimposed pre-treatment (black) and post‐treatment (red). (a) Lateral cephalometric and (b) CBCT images. The arrows indicate the growth in the midface including the orbitale.

their self‐esteem, I hope that these findings will transform our role as orthodontists when we treat growing Class III patients. According to our clinical experience, not only the anteroposterior position, but also the size of the maxilla are important when treating Class III patients with protraction headgear. In most Class III patients, their dental arch form is round [9]. This means that the maxillary dentition is compensated for the small apical base. Small apical bases can be expanded transversely and sagittally without orthognathic surgery. Typical treatment methods related to this goal are rapid maxillary expanders (RMEs) transversely and protraction headgear sagittally. We developed the SAS protraction headgear system 20 years ago. During that time in Korea, temporary anchorage devices (TADs) were already used widely, but not as an orthopedic device. They were only used for

orthodontic anchorage. In young, growing patients who need maxillary protraction, conventional intraoral anchorage such as RMEs or lingual arches can be used without serious dentoalveolar side effects. However, in older groups, we faced disappointing results with slight maxillary advancing and severe dentoalveolar protrusion of the maxillary dentition. The treatment system introduced in this chapter was developed through a long process of trial and error to prevent dentoalveolar side effects and maximize the orthopedic effects. Recently, many authors have used skeletal anchorage for orthopedic effects on their own terms [10, 11]. Each system produces its own effect respectively. For example, an orthopedic system recently introduced by De Clerck et al. [11] is able to do a good job of advancing the maxilla in the same way as our system. Class III elastics can be fixed between Bollard anchors on the (Continued)

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Figure 22.5  Case 22.1: Post‐treatment photographs after phase 2 fixed orthodontic treatment.

buttress of the maxilla and in the canine region of the mandible in young growing patients, but their system minimizes the possibility of clockwise rotation of the mandible. Orthodontists should choose appliance systems based on their ability to obtain the desired results. Since the upper miniplates are fixed in the infrazygomatic area, distant from the dental arch, they can also be used to distalize the complete upper dental arch. Based on our experience, at least three or four screws are needed to resist the protraction force of approximately 300–400 g per side. The end of the miniplate

should be exposed between the canine and first premolar area located over the keratinized attached gingiva to prevent gingival irritation. The surgeon should place the miniplate carefully to avoid touching the developing tooth germ. According to our previous study [12], the bone was the thickest (5.0 mm) in the zygomatic bone and thinnest (1.1 mm) in the anterior wall of the maxillary sinus in skeletal Class III growing patients. In conclusion, the infrazygomatic crest area and the superior lateral area of the zygomatic process of the maxilla have the most appropriate thickness for placement of a miniplate

Chapter 22  Protraction Headgear with Surgical Miniplates

Too deep

Asymmetry

Offset

Root contact

Figure 22.6  Typical surgical failures.

in growing skeletal Class III children. Figure 22.6 shows typical surgical errors when placing a miniplate. Factors Contributing to the Prognosis Superimposition of pre-treatment and post‐treatment radiographs with SAS protraction showed a 3.8 mm forward movement of the A point (A‐N perpendicular) and the SNA angle was increased from 83.4° to 86.6° with counterclockwise tipping of the palatal plane (Table 22.1). The ANB angle was changed from −1.6 to 2.7°. The SNO or the angle between the anterior cranial base and the orbitale changed from 67 to 72°. This showed that SAS protraction advanced the midface including the orbitale, unlike conventional protraction (Figure 22.4b). Sometimes we have experienced different amounts of maxillary advancement in patients of the same or similar ages (Figure  22.7a,b). Why this difference? Did it come from a difference in the skeletal age of the patients? It is well known that the best treatment effects with Class II functional appliances can be achieved during a pubertal growth spurt [13–16]. If so, what is the best time to protract maxilla, primary, or permanent dentition? With regard to the optimal age for protraction headgear, disagreement and controversy still exist [17,

18]. However, many studies have supported early treatment to maximize the skeletal effect. Despite our extensive clinical experience, these arguments are still not fully solved. However, we propose the following temporary conclusions: ●● ●●

●●

●●

Early prepubertal treatment is more effective. Skeletal age plays a more important role than chronological age. A study is needed to determine the upper limit of chronological or skeletal age when protraction headgear is still effective. The field of this study is still relatively young. Based on our experience, it is very difficult to protract the maxilla of a patient with a hand–wrist skeletal age past the MP3 G stage with a conventional headgear system. More specifically, we offer additional data such as growth stage of circum‐maxillary sutures and SOS as prognosis aids.

It was difficult to estimate a patient’s skeletal age without hand–wrist data. Even though our patient’s chronological and dental age was relatively young, we assessed her as being in the “pubertal growth spurt” stage based on her CVMS and a somatogram (Figure 22.1). In other words, this was not the optimal time to protract (Continued)

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Section II  Three-dimensional Correction with TADs

(a)

(c)

(b)

(d)

Figure 22.7  Case 22.1: (a) Superimposed pre-treatment (black) and post‐treatment (red) cephalometric tracings of this patient. (b) Superimposed pre-treatment (black) and post‐treatment (red) cephalometric tracings of other patients of a similar age to that of our patient. Note the greater advancement of the maxilla. (c) Zygomaticomaxillary suture of this patient: the density ratio of the radiolucent suture area compared with the surrounded cortical bone is greater than that of the patient in part (b). (d) Zygomaticomaxillary suture of the patient in part (b).

her maxilla if we were using conventional protraction headgear. It was a bit late. It would have been better if the patient had visited the clinic earlier. Although there is general agreement about the relationship between

physical stature and mandibular growth [19], opinions are divergent on the growth mechanism of the nasomaxillary complex, including the cranial base [20]. It might be concluded that the nasal septal cartilage, like the

Chapter 22  Protraction Headgear with Surgical Miniplates

(a) AB to MP angle 93.3% accuracy

Good 65° FHB; So, MA > MB. CR indicates center of resistance; FVA and FVB, vertical force; FHA and FHB, horizontal force; FVA+HA and FVB+HB, resultant force; DV, the perpendicular distance of the line of action of the vertical force to the CR; DH, the perpendicular distance of the line of action of the horizontal force to the CR; MA and MB, moment.

Case 48.4  Total Distalization A 24-year-old Korean female presented with the chief complaint of crowding (Figure  48.9a,b). To correct crowding, non-extraction orthodontic treatment was planned. Anboini lingual brackets and preformed straight archwires were used in both arches. Standard edgewise appliances were placed on the buccal surfaces of the maxillary first and second molars because the clinical crown length of the maxillary second molar was short. After alignment, large overjet was observed with midline discrepancy and anterior open bite on the right side (Figure  48.9c,d).

Therefore, a MAAS was constructed to distalize the maxillary dentition bodily, in which distalization force was parallel to the occlusal plane and applied through the CR of the maxillary dentition (Figure 48.10). A power arm fabricated with 0.032 × 0.032-in TMA wire was fixed into the head of the SMS microimplant with ligature wire. Crimpable hooks were attached to the archwire between the canine and first premolar. Nine months after the total distalization, the large overjet, midline discrepancy, and anterior open bite were corrected (Figure 48.9e,f).

Chapter 48  Biomechanics of Lingual Orthodontics and TADs

(a)

(b)

(c)

(d)

(e)

(f)

Figure 48.9  Case 48.4: Total distalization. (a, b) Pre-treatment. (c, d) Before total distalization of the maxillary arch. (e, f) Post-treatment.

(Continued )

505

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Section III  Clinical Applications of TADs

(a)

(b)

SMS

PA

(c)

(d)

Figure 48.10  (a) MAAS for total distalization of the maxillary arch. (b) For bodily distalization of maxillary entire dentition, the positioning of the hooks and the form of the power arm were determined on a lateral cephalogram so that a distalizing force was applied through the CR of the maxillary dentition and parallel to the occlusal plane. (c, d) Close-up view. Note the SMS microimplant (SMS); power arm (PA); line of action of distalizing force (LADF); CR of maxillary dentition from second molar to second molar (CR); and occlusal plane (OP).

Case 48.5  Total Intrusion A 27-year-old Korean female was concerned about her gummy smile (Figure 48.11a–c). The treatment plan was to move the maxillary dentition posteriorly and superiorly with a MAAS and a modified lingual arch. A MAAS in conjunction with a modified lingual arch was designed to achieve posterosuperior movement of the maxillary dentition (Figure 48.12). A modified lingual arch appliance, with hooks on canines and first molars, was bonded from second molar to second molar in the maxillary arch and the appropriate 0.032 × 0.032-in stainless steel power arm placed into the SMS microimplant (Figure  48.12a–c). Both the positioning of the hooks and the form of the power arm were determined with the aid of a lateral cephalogram, so that the applied anterior and posterior forces with respect to the CR of the maxillary dentition would move the maxillary arch posteriorly and superiorly at the same time (Figure 48.12c). It was assumed that the CR for the maxillary dentition (second molar to second molar) is located

between the roots of second premolar and first molar [8]. During intrusion for seven months, it occurred more in posterior than in anterior teeth (Figure  48.11d–f). Intrusive force was applied only to anterior teeth for another two months. After total intrusion, Fujita lingual brackets were bonded indirectly from first molar to first molar and 0.018-in slot standard edgewise appliances were placed on the buccal surfaces of the first and second molars, and alignment proceeded (Figure 48.11g–i) [9, 10]. Before debonding, crown lengthening of maxillary incisors was performed because there was a disproportion in height–width relationship of the maxillary incisors. Posterosuperior movement of the maxillary dentition and crown lengthening of the maxillary incisors improved the gummy smile (Figure  48.11j–o). The superimpositions of lateral cephalometric tracings between posttreatment and 3.5 years post-treatment showed stable results (Figure 48.11p–t).

Chapter 48  Biomechanics of Lingual Orthodontics and TADs

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

(l)

(m)

(n)

(o)

Figure 48.11  Case 48.5: Total intrusion of the maxillary dentition. (a–c) Pre-treatment. (d–f) After total intrusion for seven months. Note the posterior open bite. (g–i) After anterior intrusion only for another two months, posterior open bite was improved. (j–l) Post-treatment. (m–o) Close-up smile photos before treatment (m), after total intrusion (n), and after crown lengthening (o). (p–r) At 3.5 years post-treatment. (s, t) Superimpositions of cephalometric tracings of pre-treatment (black) and post-treatment (red), and of post-treatment (red) and 3.5-year post-treatment (green).

(Continued )

507

(r)

(q)

(p)

Parallelize S-N at sella

Parallelize S-N at sella

Parallelize ANS-PNS at ANS

(s)

Parallelize ANS-PNS at ANS

(t)

Parallelize Go-Me at Me

Parallelize Go-Me at Me

07/15/2013 (29Y 0M) 04/14/2017 (32Y 9M)

09/09/2011 (27Y 2M) 07/15/2013 (29Y 0M)

Figure 48.11  (Continued)

(a)

(b) M-LA PA SMS

(c)

(d) LAIF1 CR

LAIF2

Figure 48.12  (a, b) MAAS and modified lingual arch for total intrusion of the maxillary arch. (c, d) Lateral cephalograms before (c) and after (d) total intrusion. Both the positioning of the hooks and the form of the power arm were determined on a lateral cephalogram, so that the applied anterior and posterior forces with respect to the CR of the maxillary dentition would move the maxillary arch posteriorly and superiorly. The decreased distance between hook of the power arm and spur of the modified lingual arch is seen. Note the SMS microimplant (SMS); power arm (PA); modified lingual arch (M-LA); CR of maxillary dentition from second molar to second molar (CR); line of action of intrusion force posterior to the CR (LAIF1); and line of action of intrusion force anterior to the CR (LAIF2).

Case 48.6  Unilateral Constriction A 21-year-old male visited the orthodontic office with chief complaints of prognathic mandible and crowding (Figure 48.13a–c). Combined surgical and lingual orthodontic treatment was planned with no extraction. In both arches, Fujita lingual brackets were bonded indirectly from first molar to first molar and 0.018-in slot standard edgewise appliances were placed on the buccal surfaces of the first and second molars, and alignment proceeded [9, 10]. After alignment (Figure  48.13d–f),

­ re-surgical dental casts showed large buccal overjet of p ­posterior teeth in the right side (Figure  48.14a,b). To ­correct the large overjet, a MAAS was established (Figure  48.14c,d). The appropriate form of power arm fabricated with 0.032 × 0.032-in TMA was tied to the maxillary right posterior brackets and activated. Mandibular prognathism and crowding were corrected and good arch coordination was obtained (Figure 48.13g–j).

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

Figure 48.13  Case 48.6: Unilateral constriction of the maxillary arch. (a–c) Pre-treatment. (d–f) Before surgery. (g–i) Posttreatment. (j) Overall superimposition of cephalometric tracings of pre-treatment (black) and post-treatment (red).

(Continued )

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Section III  Clinical Applications of TADs

(a)

(b)

(c)

(d)

SMS

PA

Figure 48.14  (a, b) Study models for checking arch coordination before surgery. Before (a) and after (b) the unilateral constriction of maxillary right posterior teeth. (c, d) MAAS for the unilateral constriction of maxillary right posterior teeth. Before (c) and after (d) activation of power arm. Note the SMS microimplant (SMS); power arm (PA).

48.3  ­Discussion Recently, miniscrews have been widely used for palatal skeletal anchorage because they are relatively easy to insert and remove, and force can be applied to them almost immediately [11–14]. In 2003, Kyung et al. [11] successfully used a miniscrew in the median zone of the palate for distalization of the maxillary molars. And in 2004, Lee at al. [12] used miniscrews in the midpalate for intrusion of maxillary molars. In 2006, Park [13] used a palatal miniscrew to move the whole frontal group back in lingual orthodontic treatment. Kircelli et  al. [14] modified a pendulum for molar distalization with a miniscrew placed palatally in the premaxilla region, obtaining rapid distalization without loss of anchorage. However, these palatal skeletal anchorage systems served as only one form of absolute anchorage. The hexagonal head of the SMS microimplant with two cross‐shaped 0.032 × 0.032‐in slots provides easy placement and removal of the power arms, fabricated with either 0.032 × 0.032‐in stainless steel or TMA. Diverse configurations of

the power arm can be affixed to the head of the SMS microimplant with ligature wire. The MAAS is designed to meet the necessary anchorage force levels. In this chapter, various clinical applications using MAAS in lingual orthodontic treatment have been described and illustrated by a number of clinical cases. MAAS plays a role not only in direct skeletal anchorage (e.g. anterior retraction, posterior intrusion, total distalization, total intrusion, and unilateral constriction), but also as indirect skeletal anchorage (e.g. unilateral molar distalization). MAAS also plays two roles at once in skeletal anchorage (e.g. unilateral posterior distalization in tandem with anterior retraction, and posterior intrusion in tandem with anterior retraction). In addition, MAAS drives orthodontic forces not only with respect to individual tooth movements, but also to move entire dental arches in any direction with the assistance of a diverse array of power arm configurations and modified lingual arches. MAAS is versatile enough to provide orthodontic forces in any required direction and can be effectively used as an absolute anchorage device in lingual orthodontic treatment.

Chapter 48  Biomechanics of Lingual Orthodontics and TADs

48.4 ­Conclusions MAAS can be effectively used as an absolute anchorage device in lingual orthodontic treatment for the following reasons: ●●

MAAS plays a role not only in direct skeletal anchorage, but also as indirect skeletal anchorage.

●●

●●

●●

MAAS also plays two roles at once in skeletal anchorage. MAAS drives orthodontic forces not only with respect to individual tooth movements, but can also move entire dental arches. MAAS provides for orthodontic forces in any required direction.

­References 1 Kyung SH. A study on the bone thickness of midpalatal suture area for miniscrew insertion. Korean J Orthod. 2004;34:63–70. 2 Gracco A, Lombardo L, Cozzani M, Siciliani G. Quantitative cone‐beam computed tomography evaluation of palatal bone for orthodontic miniscrew placement. Am J Orthod Dentofacial Orthop. 2008;134:361–369. 3 Moon SH, Park SH, Lim WH, Chun YS. Palatal bone density in adult subjects: Implications for mini‐implant placement. Angle Orthod. 2010;80:137–144. 4 Kim HJ, Yun, HS, Park HD, et al. Soft‐tissue and cortical‐ bone thickness at orthodontic implant sites. Am J Orthod Dentofacial Orthop. 2006;130:177–182. 5 Hong RK, Lim SM, Heo JM, Baik SH. Lingual applications of the midpalatal absolute anchorage system. J Clin Orthod. 2012;46:344–353. 6 Vanden Bulcke MM, Burstone CJ, Sachdeva RCL, Dermaut LR. Location of the centers of resistance for anterior teeth during retraction using the laser reflection technique. Am J Orthod Dentofacial Orthop. 1987;91:375–384. 7 Hong RK, Heo JM, Ha YK. Lever‐arm and mini‐implant system for anterior torque control during retraction in

lingual orthodontic treatment. Angle Orthod. 2004;75:129–141. 8 Billiet T, De Pauw G, Dermaut L. Location of the centre of resistance of the upper dentition and the nasomaxillary complex. An experimental study. Eur J Orthod. 2001;23:263–273. 9 Hong RK, Sohn HW. Update on the Fujita lingual bracket. J Clin Orthod. 1999;33:136–142. 10 Hong RK, Kim YH, Park JY. A new customized lingual indirect bonding system. J Clin Orthod. 2000;34:456–460. 11 Kyung SH, Hong SG, Park YC. Distalization of maxillary molars with a midpalatal miniscrew. J Clin Orthod. 2003;37:22–26. 12 Lee JS, Kim DH, Park YC, et al. The efficient use of midpalatal miniscrew implants. Angle Orthod. 2004;74:711–714. 13 Park HS. A miniscrew‐assisted transpalatal arch for use in lingual orthodontics. J Clin Orthod. 2006;40:12–16. 14 Kircelli BH, Pektas Z, Kircelli C. Maxillary molar distalization with a bone‐anchored pendulum appliance. Angle Orthod. 2006;76:650–659.

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49 TADs with a Fully Customized CAD-CAM Lingual Bracket System Toru Inami1,2 1

Department of Orthodontics, Aichi Gakuin University, Nagoya, Japan Private Practice, Kyoto, Japan

2

49.1  ­Features of a Fully Customized CAD-CAM Lingual Bracket System With conventional lingual bracket systems, patients frequently have discomfort, difficulty in speaking and eating, and sore tongues due to the large size and high profile of the brackets. They are also challenging for orthodontists due to difficulty with torque control on the anterior teeth, especially in extraction cases, because of the biomechanics inherent in lingual treatment with horizontal slots. There is increased risk of rabbiting (uncontrolled tipping) of the maxillary anterior teeth due to the vertical bowing effect. In addition, it is difficult to achieve accurate rebonding, detailing, and finishing. Furthermore, attempts to incorporate straight wire mechanics and self‐ligation technology into conventional lingual bracket systems have caused a thickening of brackets and resin bases which result in a narrowing of the oral cavity. Many of the problems with conventional lingual bracket systems have been overcome with the recently developed Incognito lingual bracket appliance. The use of digital technology has made customization possible and has created a positive cycle of enhanced production efficiency, improved precision, comfort of the final products, and increased accuracy of treatment. The Incognito lingual bracket appliance offers the following features [1]: ●●

●●

●●

Multiple treatment plans that can be studied efficiently on virtual digital setups. Close communication between the clinic and the laboratory, resulting in better exchange of digital information (treatment management portal, TMP) and shorter manufacturing and delivery times. Accurate bracket positioning and higher product quality.

●● ●●

Precise and reproducible custom archwires. A ribbon vertical and horizontal type bracket design with slots for flat archwires and vertical slots for the anterior teeth and horizontal slots for the posterior teeth, and with archwires that pass extremely close to the lingual surfaces of the teeth, enhancing patient comfort.

49.2  ­Vertical and Horizontal Bowing Effects in Lingual Orthodontic Treatment The following evidence is presented in support of the benefits of a fully customized CAD‐CAM lingual orthodontic appliance (Incognito).

49.2.1  Rigidity of Ribbon (Flat) Archwires An 0.025 × 0.017‐in ribbonwise archwire placed in Incognito lingual brackets during en‐masse retraction in the maxillary arch is approximately 1.8 times as rigid as a 0.017 × 0.025‐in edgewise archwire for conventional lingual brackets.

49.2.2  Accuracy of Treatment Grauer and Proffit [2] conducted a study on the accuracy of treatment in patients treated with Incognito lingual bracket appliances by superimposing the maxillary setup and final models. The mean linear and rotational errors in tooth alignment were less than 1 mm and 4°, respectively, for all teeth except the second molars. They concluded that the Incognito lingual bracket appliance provided highly accurate tooth movements as planned on setup models.

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section III  Clinical Applications of TADs

49.2.3  Comparison of Vertical Bowing Effects in the Incognito and Conventional Lingual Bracket Systems

49.2.4  Pilot Study on the Horizontal Bowing Effect with the Incognito Lingual Bracket Appliance

A comparative study was conducted with 33 adult female patients who had had four premolars extracted in our clinic. Ten were treated using the Incognito lingual bracket appliance (Incognito group) and 23 were treated using a conventional lingual bracket system (Conventional group). Pre-treatment and post‐treatment lateral cephalometric tracings were analyzed for 25 items using Wilcoxon rank sum test. Favorable treatment results were obtained with significant SNA and ANB reductions in both groups. However, some patients in the Conventional group showed a large amount of retraction and lingual tipping of the anterior teeth. In the Incognito group, on the other hand, the anterior teeth were retracted with good torque control (Figure  49.1). The results suggest that the Incognito lingual bracket appliance effectively counteracts the vertical bowing effect, one of the side effects associated with conventional lingual treatment (Figures 49.1 and 49.2) [3].

Ribbonwise archwires are approximately half as rigid as edgewise archwires in the horizontal dimension. This increases the susceptibility of ribbonwise archwires to the horizontal bowing effect and resultant shortening of the distance between the second molars during retraction of the anterior teeth with heavy traction force. A study was conducted to examine how teeth would move with different anchor screw positions and different points of force application using the Incognito lingual bracket appliance. The survey included two groups of patients treated with the extraction of four first premolars in two orthodontic offices. The maxillary anterior teeth were retracted with direct force application from orthodontic miniscrews palatally placed in the alveolar bone to the canine on each side of the arch in one group, and from palatal miniscrews to lever arms soldered between the central and lateral incisors with the help of a palatal bar in the other group. The results showed 2.7 mm of narrowing of the inter‐arch distance in

Pre-treatment vs. post-treatment (mm) 14

U1 to NA (mm)

***

12 8

30

6

20

4 0

(mm) 14

0 PRE

POST

PRE

U1 to NA (mm)

(°) 50

***

40

12 10

FCR-VH

8

30

6

20

4

POST

U1 to NA (degree)

**

10

2 0 –2

***

10

2 –2

U1 to NA (degree)

40

10

Conventional

(°) 50

0 PRE

POST

PRE

POST

Figure 49.1  Comparison between conventional and Incognito lingual orthodontic appliances. Changes in U1-NA before and after treatment are less variable in the maintenance of proper torque. FCR-VH, Fully customized ribbonwise wires and lingual brackets system with anterior vertical and posterior horizontal slots

Chapter 49  TADs with a Fully Customized CAD-CAM Lingual Bracket System

MI

LA

CR

Horizontal slot

MI

CR LA

0.016 × 0.024-in SS Retraction from midpalatal miniscrew

Vertical slot

Figure 49.2  Horizontal slots with edgewise wire are susceptible to a vertical bowing effect and lingual inclination of the maxillary anterior teeth, while the anterior vertical slots with ribbonwise wire facilitate bodily retraction of the anterior teeth with minimum extrusion and lingual inclination.

(a)

Alveolar bone miniscrew

(b)

Midpalatal miniscrew, lever arm, and palatal bar Midpalatal miniscrew with lever arm and palatal bar

Alveolar bone miniscrew

Maxilla

Set up

Finish

Difference

Maxilla

Set up

Finish

Difference

C

35.9

35.4

–0.5

C

36.9

37.3

0.4

P2

43.7

43.4

–0.3

P2

44.3

45.3

1.0

M1

43.4

42.5

–1.1

M1

44.7

45.3

0.6

M2

49.4

46.7

–2.7

M2

50.4

49.8

–0.6

(mm)

(mm)

Figure 49.3  Miniscrew position in relation to Incognito lingual bracket appliances. (a) A study was conducted to examine differences in tooth movement with different miniscrew positions (alveolar vs. midpalatal) and different points of force application (with and without lever arms). (b) With direct force application from alveolar bone miniscrews, the inter-arch distances in the first and second molar areas became narrower (left table). In contrast, no narrowing of the posterior arch widths was observed when traction forces were applied from the midpalatal miniscrew to the lever arms (right table). C, Canine; P2, second premolar; M1, first molar; M2, second molar.

the second molar region and lingual crown tipping of the molars with the lingual cusps hanging down when traction force was applied directly from the alveolar bone miniscrews. No arch narrowing was noted when force was applied

from the tips of the lever arms toward the center of the palate with the support of a palatal bar (Figures 49.3a,b). This may be explained by the increased susceptibility of the maxillary anterior teeth to rabbiting and difficulty in controlling

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Section III  Clinical Applications of TADs

the posterior teeth with direct force from more occlusally placed miniscrews. In contrast, the maxillary anterior teeth may be retracted more bodily when force is applied from a higher position to lever arms, decreasing the risk of losing control in the posterior area. These results indicate that a combination of a midpalatal miniscrew, lever arms, and a palatal bar may be an effective approach to reducing the horizontal bowing effect, which is a drawback with the Incognito lingual bracket appliance [4, 5].

49.3  ­Summary of Insertion Sites for TADs with Fully Customized CAD-CAM Lingual Bracket Appliances When treating high‐angle maxillary protrusion cases it is important to achieve anterior retraction and A‐point reduction while preventing clockwise rotation of the

Mechanics Pattern of En-Masse Retraction (a)

Power chains TADs to TPA No transverse anti-bowing curve

Light transverse anti-bowing curve

Light transverse anti-bowing curve

Light transverse anti-bowing curve

Double cables

TPA (recommended)

Eight tiesTADs to U5s

Medium power hooks

TPA (recommended)

Power chains U3s to U7s

Power chains U3s to U7s

Power chains U3s to U6s

Power chains PHs to TADs

Power chains U3s to U7s

Eight tie UR3-UL3

Conventional Mechanics

TADs TPA

Light transverse anti-bowing curve

Eight ties: UR3-UL3, UR6-UR7, and UL6-UL7 Anti-tipping bend 7°: UR2, UR3, UL2, and UL3

TPA with no TADs Two palatal slope TADs

PHs with 2 palatal slope TADs

TPA with 2 palatal slope TADs

TAD (alveolar)

None

None

TAD (alveolar)

TAD (alveolar)

None

TPA

None

None

TPA

Transverse Anchorage Vertical Anchorage

Minimum

Moderate

Minimum

Minimum

Moderate

Minimum

Moderate

Moderate

Moderate

Maximum

A-P Anchorage

Minimum

Moderate

Maximum

Maximum

Maximum

TADs, Temporary anchorage devices; TPA, Transpalatal arch; PHs, Power hooks

Mechanics Pattern of En-Masse Retraction

(b)

Long power hooks

Long power hooks

Light transverse anti-bowing curve

Light transverse anti-bowing curve

TPA (recommended)

i - Station

i - Station (multi)

AGUPB

Power chains: PHs to TAD

Power chains: PHs to TAD

Power chains: PHs to TAD-LA

Power chains U3s to U7s

Power chains AGUPB to TAD

Eight tie: UR3-UL3

Short power hooks Light transverse anti-bowing curve

Light transverse anti-bowing curve

Light transverse anti-bowing curve

Anti-tipping bend 7°: UR2, UR3, UL2, and UL3

PHs with an i-Station (multi) with a AGUPB with a midpalatal i-Station and midpalatal midpalatal TADs TAD TADs

PHs with a midpalatal TAD

PHs with a TPA and midpalatal TAD

TADs

TAD (palatal)

TAD (palatal)

TADs (palatal)

TADs (palatal)

TPA

None

TPA

i-Station

i-Station (multi)

AGUPB

Transverse Anchorage Vertical Anchorage

Moderate

Maximum

Minimum

Maximum

Maximum

Moderate

Maximum

Minimum

Maximum

Maximum

Maximum

Maximum

Maximum + Distal mvt.

Maximum + Distal mvt.

Maximum + Distal mvt.

A-P Anchorage

TAD (palatal)

TADs, Temporary anchorage devices; TPA, Transpalatal arch; PHs, Power hooks; TAD-LA, Lingual arch fixed by TAD; AGUPB, Aichi Gakuin University palatal bar (Improved transpalatal arch)

Figure 49.4  (a, b) Summary of the treatment protocol for extraction cases with and without TADs in alveolar or midpalatal bone. PHs, Power hooks; TPA, transpalatal arch; AGUPB, Aichi Gakuin University palatal bar (improved TPA).

Chapter 49  TADs with a Fully Customized CAD-CAM Lingual Bracket System

mandible through good vertical control. The treatment goal is to improve not only occlusal relationship but also facial profile in high‐angle maxillary protrusion cases with protruded lips. However, conventional lingual brackets cannot achieve adequate A‐point reduction when a bowing effect occurs due to the loss of torque during anterior retraction, something that may hinder facial improvement [6–8]. In this chapter we present a case of skeletal maxillary protrusion with the chief complaint of protruded lips that was treated with  a combination of an Incognito lingual bracket

appliance and an orthodontic anchor screw to illustrate some of the points to be considered when resolving this sort of patient complaint. In Japan, orthodontists see many high‐angle and bimaxillary protrusion patients with severe crowding. More than 60% of them end up being extraction cases. In response to this a group of Japanese Incognito appliance instructors have developed a guidebook called Treatment Protocols for Extraction Cases. It provides a summary of insertion sites for TADs along with the Incognito lingual bracket appliance (Figure 49.4a,b) [9].

Case 49.1  Use of TADs and Incognito Lingual Brackets in an Open Bite Case A female patient aged 22 years and 5 months presented with open bite and high-angle Class II Division 2 malocclusion (Figure 49.5a,b).

Treatment Plan Treating cases of open bite with high mandibular angles without extracting any teeth requires inducing a

(a)

Figure 49.5  Case 49.1: (a) Pre-treatment facial and intraoral photographs. (b) Pre-treatment radiographs and tracing.

(Continued )

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Section III  Clinical Applications of TADs

(b)

Figure 49.5  (Continued)

c­ounterclockwise rotation of the mandible through intrusion of the upper and lower molars after providing sufficient torque control of the anterior teeth. To achieve this, we established a treatment strategy for our patient based on the following three points: ●●

Providing torque control of the maxillary and mandibular anterior teeth: For the maxillary anterior teeth, SNA can be improved by retraction of the anterior teeth through bodily movement while maintaining the preexisting torque. For the mandibular anterior teeth, ANB angles are improved in cases with backward rotation of the mandible (as in the present case). Posterior movement of the B point should be avoided during treatment [4]. In the mandibular anterior region, the tooth axis showed mild lingual inclination and deep curve of Spee was observed. So, the anterior mandibular teeth should be moved labially by 0.5 mm through a tipping movement and straightened up

●●

●●

fully in the alveolar bone. These can be performed without ­extracting any teeth because the third molars had already been extracted at the previous hospital. Providing vertical control: In this case, we developed a treatment plan to intrude the maxillary and mandibular molars and rotate the mandible as much as possible in a counterclockwise direction. Along with the plan, we intruded the molars as much as possible with a miniscrew and miniplates, while minimizing the use of vertical elastic bands which tend to induce extrusion of the maxillary and mandibular anterior teeth (Figure 49.6) [10]. Prevention of the bowing effect: Biomechanically, transverse and vertical bowing effects can occur in orthodontic treatments with conventional lingual brackets [8]. In this case, we used ribbonwise archwires and Incognito brackets with a vertical slot in the anterior region and horizontal slots in the molar region. This arrangement made the present case relatively resistant to any vertical bowing effect; nevertheless, we had to pay attention to

Chapter 49  TADs with a Fully Customized CAD-CAM Lingual Bracket System

A B D

C E

A

A E

B

E

C

Figure 49.6  Case 49.1: Retraction method for fully customized lingual orthodontic treatment with midpalatal miniscrew and a modified transpalatal arch. A, Miniplates; B, midpalatal miniscrew; C, transpalatal arch; D, center of resistance; E, elastomeric chains.

the transverse bowing effect [2]. We thought that a transverse bowing effect was unlikely because no teeth had been extracted in this case, and lateral expansion of the arch form was possible due to maxillary molar intrusion by the miniplates placed on the buccal side. We planned to prevent such side effects by using a palatal bar.

Course of Treatment ●●

●●

●●

Step 1: Leveling, alignment, and establishment of anterior torque (Figure 49.7a) Step 2: Intrude maxillary and mandibular molar region (Figure 49.7b) Step 3: Detailing and finishing (Figure 49.7c)

(a)

(b)

(c)

Figure 49.7  Case 49.1: Progress intraoral photographs (treatment steps). (a) Step I: leveling and alignment, torque establishment. (b) Step II: midpalatal miniscrew and miniplates were placed and intruded the molar region. (c) Step III: detailing and finishing.

(Continued )

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Section III  Clinical Applications of TADs

Treatment Results ●●

●●

●●

●●

Changes in facial appearance: In frontal view, the tension of the mentalis when the lips were closed was gone. In profile view, because of improvements of the high mandibular plane angle, the opening and closing of the patient’s lips were no longer stressful (Figures 49.8a,b). Intraoral changes: Maxillary tooth crowding and severe anterior open bite were improved significantly. In addition, the dental midline was corrected, and the periodontal tissue was in a good condition with no gingival recession. Skeletal changes: On lateral cephalogram, SNA was unchanged; SNB was improved from 76.5° to 77.0°; ANB was improved from 5.5° to 5.0°; FMA decreased from 37.0° to 36.0°; and SN-MP decreased from 41.0° to 40.0° (Figure 49.8, Table 49.1). Dental changes: The molar relationships improved to Angle Class I. Overjet and overbite improved from 5.0 to 2.5 mm and from −6.0 to 1.0 mm, respectively. From

panoramic radiographic findings, root parallelism was observed. Despite the mild and careful retraction of teeth, mild root resorption was observed throughout the maxillary and mandibular teeth. Two Years Retention All-day use of soft retainers was started in both jaws on the day the lingual appliances were removed, and night-time use of tooth positioners was started six months later. Then, at eight months after orthodontic treatment, the use of a Hawley retainer and a spring retainer began in the maxilla and mandible, respectively. For at least two years and four months after active treatment, anterior coupling, periodontal tissue, profile facial view, and  occlusion remained stable except for the molar relationship. In observing the dental model, the patient’s occlusion remained stable with no change in the arch width for at

(a)

Figure 49.8  Case 49.1: (a) Post-treatment facial and intraoral photographs. (b) Post-treatment radiographs and tracing.

Chapter 49  TADs with a Fully Customized CAD-CAM Lingual Bracket System

(b)

Figure 49.8  (Continued) Table 49.1  Case 49.1: Lateral cephalometric measurements. Norm

Pre-treatment

Post-treatment

Two-year retention

SNA (°)

82.0

82.0

82.0

82.0

SNB (°)

80.0

76.5

77.0

77.0

ANB (°)

2.0

5.5

5.0

5.0

Wits (mm)

0.0

0.0

−0.5

0.0

SN‐MP (°)

32.0

41.0

40.0

40.0

FH‐MP (°)

25.0

37.0

36.0

36.0

LFH (ANS‐Me/N‐Me) (%) U1‐SN (°)

55.0

59.3

58.2

58.2

104.0

97.5

93.5

92.5

U1‐NA (°)

22.0

14.5

12.5

10.0

IMPA (°)

90.0

83.0

88.0

91.0

L1‐NB (°)

25.0

21.0

25.5

28.0

(Continued )

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Section III  Clinical Applications of TADs

Table 49.1  (Continued) Norm

Pre-treatment

Post-treatment

Two-year retention

U1/L1 (°)

131.0

139.0

137.0

137.0

Upper lip‐E line (mm)

−4.0

−2.5

−2.5

−3.5

Lower lip‐E line (mm)

−2.0

−2.5

−1.0

−3.0

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; Wits, distance between perpendiculars drawn from point A and point B onto the occlusal plane; SN‐MP, sella‐nasion plane to mandibular plane; FH‐MP, FH plane to mandibular plane; LFH (ANS‐Me/N‐Me), lower facial height, ratio between anterior nasal spine‐menton and nasion‐menton; U1‐SN, long axis of maxillary central incisor to sella‐nasion plane; U1‐NA, long axis of maxillary central incisor to nasion‐A point line; IMPA, incisor mandibular plane angle; L1‐NB, lower incisor to nasion‐B point line; U1/L1, angle formed by long axes of maxillary and mandibular central incisors; Upper lip‐E Line, distance between upper lip anterior point and E line (esthetic plane of Ricketts; line that passes through the tip of the nose and soft tissue pogonion); Lower Lip‐E line, distance between lower lip anterior point and E line.

least three years after treatment. These findings suggest that the molars were well controlled in this severe open bite patient [11]. Currently, the patient has no signs or symptoms caused by temporomandibular disorders (Figure 49.9a,b).

Evaluation of the Treatment Superimposition of lateral cephalometric tracings revealed that the patient’s maxillary anterior teeth moved posteriorly and extruded while maintaining

(a)

Figure 49.9  Case 49.1: (a) Two-year retention facial and intraoral photographs. (b) Two-year retention radiographs and tracing.

Chapter 49  TADs with a Fully Customized CAD-CAM Lingual Bracket System

(b)

Figure 49.9  (Continued)

torque, whereas her mandibular anterior teeth extruded while tipping slight labially, resulting in a tight occlusion in the anterior region. In the molar region, her maxillary second molar attained 2 mm of intrusion and moved 1 mm distally, whereas her mandibular second molar attained 1 mm of extrusion and moved 1 mm mesially. A Class I dental relationship was obtained (Figure 49.10a–d). Case Summary When attempting to improve open bite by orthodontic treatment alone without extracting any teeth, it is important to focus on three points –  torque control, vertical control, and anchorage control – throughout treatment in the same way as in a maxillary protrusion case with high angle. First, to manage torque control, we selected a lingual orthodontic appliance intended to provide adequate

torque control of the anterior teeth and to manage tongue thrust [12]. Second, for vertical control, we planned to intrude maxillary molars actively by applying an Incognito system in combination with a miniscrew and miniplates (Figure  49.6). In this case, the overbite depth indicator (ODI) value at initial examination was 74.0°, which was almost the normal value (74.5°) (Table  49.1) [13]. Therefore, we assumed the alveolar factor was the major contributor and caused overeruption of the second molar. Lastly, to manage anchorage control, a palatal bar was used throughout the treatment to control the dental arch width in order to correct and stabilize the dental arch form and to provide maximum prevention against a horizontal bowing effect. In order to manage these three points, the aim of the treatment was to improve the ANB angle from 5.5° to 5.0°, U1-NA distance from 2.5 mm to 1.0 mm, and L1-NB distance from 5.0 mm to 5.5 mm on the level anchorage system (LAS) chart [14]. (Continued )

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As these results show, we were able to improve the corresponding values to 5.0°, 2.0 mm, and 7.0 mm, respectively, and relieved maxillary anterior crowding and leveled the curve of Spee in the mandible while providing satisfactory anterior torque control (Figures  49.8 and 49.9). Superimposition of lateral cephalometric tracings revealed that the combined use of the Incognito system, a minis-

crew, and miniplates led to adequate molar intrusion in the maxilla, resulting in ­counterclockwise (forward) rotation of the mandible and Class I molar relationships. At present, more than two years post-retention, proper anterior coupling is observed with no molar extrusion, suggesting that adequate molar control was provided by the Incognito system in combination with TADs (Figure 49.10).

(a)

(b)

(c)

(d)

Figure 49.10  Case 49.1: (a, b) Cephalometric tracings: pre-treatment (black), post-treatment (red). (c, d) Cephalometric tracings: pre-treatment (black), post-treatment (red); retention (green).

R ­ eferences 1 Wiechmann D, Rummel V, Thalheim A, et al. Customized brackets and archwires for lingual orthodontic treatment. Am J Orthod Dentofacial Orthop. 2003;124:593–599. 2 Grauer D, Proffit WR. Accuracy in tooth positioning with fully customized lingual orthodontic appliances. Am J Orthod Dentofacial Orthop. 2011;140:433–443.

3 Inami T, Nakano Y, Miyazawa K, et al. Adult skeletal Class II high‐angle case treated with a fully customized lingual bracket appliance. Am J Orthod Dentofacial Orthop. 2016;150:679–691. 4 Hong RK, Heo JM, Ha YK. Lever‐arm and mini‐implant system for anterior torque control during retraction in

Chapter 49  TADs with a Fully Customized CAD-CAM Lingual Bracket System

lingual orthodontic treatment. Angle Orthod. 2005;75:129–141. 5 Mujagic M, Fouquet C, Galletti C, et al. Digital design and manufacturing of the Lingualcare bracket system. J Clin Orthod. 2005; 39:375–382. 6 Inami T. Clinical considerations for the establishment of facial balance and harmony. In: Romano R, ed. Lingual and Esthetic Orthodontics. New Malden, UK: Quintessence Publishing, 2011, pp. 563–580. 7 Kawakami M, Miyawaki S, Noguchi H, Kirita T. Screw‐type implants used as anchorage for lingual orthodontic mechanics: a case of bimaxillary protrusion with second premolar extraction. Angle Orthod. 2004;74:715–719. 8 Inami T, Yoshizawa Y, Aizawa I, et al. Lingual Bracket Orthodontic Technique. Tokyo: Ishiyaku Publishers, 2009. 9 Sugiyama S, Hirose K, Inami T. Chapter 10. Protocol of the extraction cases. In: Full Custom Digitally Manufactured

Lingual Appliance System. Tokyo: Ishiyaku Publishers, 2017, pp. 95–128. 10 Proffit WR. Special aspects of orthodontic therapy for adults – intrusion of posterior teeth to close anterior open bite. In: Contemporary Orthodontics, 5th edn. St. Louis, MO: Mosby, 2013, pp. 679–684. 11 Baek MS, Choi YJ, Yu HS, et al. Long‐term stability of anterior open‐bite treatment by intrusion of maxillary posterior teeth. Am J Orthod Dentofacial Orthop. 2010;138:396.e1–396.e9. 12 Geron S, Wasserstein A, Geron Z. Stability of anterior open bite correction of adults treated with lingual appliances. Eur J Orthod. 2013;35:599–603. 13 Kim YH. Overbite depth indicator with particular reference to anterior open‐bite. Am J Orthod. 1974;65:586–611. 14 Root TL. The level anchorage system for correction of orthodontic malocclusions. Am J Orthod. 1981;80:395–410.

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50 TAD-assisted Lingual Retractors Ki-Ho Park, Hyo-Won Ahn, and Yoon-Goo Kang Department of Orthodontics, School of Dentistry, Kyung Hee University, Seoul, South Korea

50.1 ­Introduction Successful orthodontic resolution of bimaxillary dentoalveolar protrusion depends on successful retraction of anterior dentition, which consists of acquiring proper buccolingual inclination and proper vertical position of anterior teeth. To fulfill these requirements, clinicians have devised numerous biomechanical and surgical orthodontic options. A palatal retractor for retraction of maxillary anterior dentition is one of the fruits of clinician’s long-time endeavors and an evolution of the biomechanical design. A palatal retractor splints the maxillary anterior dentition on the lingual side with bonded mesh plates connected by a supporting wire. Two long palatally extended arms are soldered to the supporting wire in order to provide a point at which to apply adequate retraction force. Palatal retractors have several advantages over conventional bracket/wire systems. The two most prominent ones are biomechanical superiority and esthetic invisibility. As the palatal retractor is positioned on the lingual surface of the maxillary anterior dentition, it is not visible from the frontal view, which is a distinct esthetic advantage. Moreover, anterior dentition retraction constitutes a significant portion of the total treatment time in extraction orthodontic treatment, so this invisibility feature affords a benefit to the patients. It is not an easy task to control the torque of anterior dentition during retraction with a conventional bracket/wire system. This is due not only to the long distance between the point of force application and the center of resistance of the anterior dentition, but also because of the innate ineffectiveness of the torque control biomechanics of a bracket/wire system [1]. The center of resistance of the anterior dentition is commonly reported to be positioned in a high position, far from the brackets [2–4]. To address

this limitation, high torque values have often been prescribed on the anterior brackets, the curve of Spee has been expressed on the main working archwire, an additional spring or loops have been added, and other methods have been proposed in everyday orthodontic practice [1, 5] but even with these strategies, some cases still lose torque control and fail to finish in a proper buccolingual inclination [6]. Vertical control is even more difficult with conventional bracket/wire systems. The best option is to maintain the vertical position during retraction while intruding the anterior dentition in bialveolar/bimaxillary protrusion cases. Extrusion of the anterior dentition can be useful in anterior open bite cases but is harmful in deep bite cases and may impair smile esthetics in gummy smile cases. The palatal arms on the retractors can extend to the center of resistance of the anterior dentition [3, 7–10]. By adjusting the length of the palatal arm and the point of force origin, the line of force can be controlled. As a result, bodily retraction and an increase or decrease in torque can be achieved [7, 10]. Both torque and vertical position of the anterior dentition can be controlled with palatal retractors. Kim et al. [10] reported a severe Class II anterior deep bite case treated with a C-lingual retractor. They showed successful simultaneous intrusion and retraction of maxillary anterior dentition with this type of palatal retractor. Nahm et al. [11] also showed a gummy smile case treated by intrusion of the maxillary anterior segment with a palatal retractor. Since the advent of temporary anchorage devices (TADs) in orthodontics, anchorage management has been much simpler than before, and anterior dentition can be retracted to planned positions with higher predictability. A combination of TADs and palatal retractors provides the possibility of maximizing control of both the torque and vertical position [7, 8, 10, 12, 13]. Furthermore, palatal bone quality is

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section III  Clinical Applications of TADs

good and there are a wide range of possible TAD placement sites with lower failure rates [14–17]. Clinicians can choose palatal TAD placement sites based on the planned direction of the retraction of the maxillary anterior dentition with fewer anatomic limitations than on the buccal side of the alveolar bone, and with a lower failure rate. By changing the position of the palatal TADs and length of the palatal retractor arm, anterior dentition can be displaced to the desired retraction in three dimensions. The design of the palatal retractor has evolved over the past two decades, and many designs have been proposed, such as the C‐lingual retractor, lingual lever arm, double‐J retractor, anteroposterior lingual retractor, etc. [3, 8, 12, 18]. Although different names have been given to these appliances by their inventors, all these palatal retractors share common major components, such as palatal arms and splinting of the maxillary anterior dentition on the palatal side. This chapter will describe clinical considerations, applications, and results of palatal retractor use in clinical cases (Figure 50.1).

50.2 ­The C-lingual Retractor System with a C-palatal Plate 50.2.1 Design The C‐lingual retractor was introduced and developed by Chung and coworkers [19, 20] and Kim et al. [21, 22] have reported on several cases treated with them. To fabricate

the C‐lingual retractor, a lingual arch and two lever arms made of a 0.032‐in stainless steel (SS) wire are soldered to anterior mesh pads. After the retractor is fabricated, it is bonded to the lingual surface of the anterior teeth. Two nickel–titanium (NiTi) closed coil springs are used as a power source. They are stretched palatally from the retractor to the soldered hook of the transpalatal arch (TPA). A  TPA, also made of 0.032‐in SS wire, is needed for the intra‐arch anchorage unit and to control the desired ­direction of force (Figure 50.2).

50.2.2  C-palatal Plate When maximum anchorage is required during retraction of the anteriors, TADs are inserted in the midpalatal area. In the early days, a miniscrew was placed when retracting an anterior portion using a C‐lingual retractor. However, as orthodontic treatment progresses, the miniscrew is often buried in the soft palatal tissue. In patients with thick soft tissue, shallow placement of the miniscrew in order to expose the screw head can decrease the stability of the miniscrew. On the other hand, when the miniscrew is inserted deeply to increase the primary stability of the screw, the screw head is often not exposed. Based on this experience, it is now common to use a C‐palatal plate (Jin Biomed, Bucheon, South Korea) instead of a miniscrew. Chung et al. [12, 23] and Kim et al. [10] reported on several cases treated by combining a C‐lingual retractor and a C‐palatal plate (Figure 50.1b).

(a)

(b)

(c)

(d)

Figure 50.1  Retraction of anterior teeth using a lingual system and TADs. (a) Conventional lingual brackets. (b) C-lingual retractor. (c) Double J retractor. (d) Anteroposterior lingual retractor.

Chapter 50  TAD-assisted Lingual Retractors

Figure 50.2  Design of the C-lingual retractor without TADs.

50.2.3  Advantages of C-lingual Retractors In general orthodontic treatment, the anterior teeth are retracted after they have been aligned. However, when a C‐lingual retractor is used to treat patients with lip protrusion, their chief complaint can be addressed early because the anterior teeth are retracted before they are aligned. In addition, the design of the C‐­l ingual retractor is very simple and easy to manufacture, so orthodontists can apply this very economical device

without paying expensive material and laboratory costs.

50.2.4 Biomechanics A combination of TADs and C‐lingual retractors maximizes the ability to control torque and vertical position of anterior teeth. By changing the position of the palatal TADs and length of the power arm of the lingual retractor, anterior dentition can be retracted as needed [7].

Case 50.1  Patient A 15-year-old female patient came to the orthodontic clinic with the chief complaint of anterior protrusion. She had a convex profile, incompetent lips and lip protrusion. Intraoral examination revealed a Class I malocclusion with a large overjet, mild anterior crowding on upper arch, and deep curve of Spee in the lower arch. Lateral cephalometric analysis showed skeletal Class II with a retrognathic mandible, normovergent pattern, and labioversion of the maxillary and mandibular incisors. A panoramic radiograph showed root canal treatment on the maxillary left first premolar and mandibular left second premolar. The maxillary right second premolar had a short root and periapical radiolucency (Figure 50.3 and Table 50.1). Diagnosis and Treatment Planning The patient was diagnosed as skeletal Class II and dental Class I with a normovergent pattern, large overjet, and anterior proclination. Since she wanted to resolve her lip protrusion, four premolar extraction treatment was suggested. Even though the plan had been to extract the first premolars on the upper arch and second premolars on the lower arch, her upper right second premolar was

extracted instead of the first premolar because the upper right second premolar had a short root and periapical radiolucency. The patient wanted early improvement of her lip protrusion and an invisible appliance on her upper arch, so a C-lingual retractor was selected for retraction. Treatment Progress The lingual retractor was applied to the incisors, canines, and the right first premolar, and lever arms were connected on the lateral incisors. A C-palatal plate was inserted in the midpalatal area. After delivery of the retractor, two NiTi closed coil springs are used as a power source. They were stretched from the lever arm to the C-palatal plate. On the lower arch, conventional treatment using full fixed appliances (QuicKlear, Roth prescription, 0.022-in) were performed. A C-tube was implanted between the mandibular central incisors to intrude the mandibular anterior teeth and reduce the curve of Spee. After using a C-lingual retractor for seven months, the maxillary incisors were retracted by 4 mm from their initial position and exhibited controlled tipping. There was 1 mm of anchor loss in the maxillary molars, but there was no significant vertical movement of the maxillary incisors or molars. After nine months (Continued )

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Figure 50.3  Case 50.1: Initial records.

Chapter 50  TAD-assisted Lingual Retractors

Table 50.1  Case 50.1: Cephalometric measurements. Mean

Initial

Progress (7 mo)

Final

Maxilla–mandible relation ANB (°)

2.8

3.8

3.7

4.6

APDI (°)

85.8

78.0

78.0

74.7

81.7

81.0

80.7

81.9

2.0

0.6

‐0.5

1.0

Maxilla SNA (°) N perp‐Pt.A (mm) Mandible SNB (°)

79.0

77.2

77.0

77.3

N perp‐Pog (mm)

−0.3

−8.2

−8.2

−7.8

395.7

398.0

397.9

397.0

Divergency SUM (°) PFH/AFH (%)

70.0

64.4

64.2

65.5

FH‐OP (°)

5.9

10.2

12.8

11.8

FH‐MP (°)

25.4

28.5

29.0

28.1

Interincisal angle (°)

128.3

111.9

122.4

131.0

U1‐FH (°)

116.6

119.4

112.3

108.4

IMPA (°)

90.1

100.2

96.4

92.5

U6‐PP (mm)

25.0

31.6

31.4

32.7

Denture

U1 exposure (mm) L1‐APog (°) L1‐APog (mm)

4.0

4.6

3.6

4.3

23.3

30.2

28.2

21.5

4.5

7.9

6.6

2.7

ANB, A point‐nasion‐B point; APDI, anteroposterior dysplasia indicator, sum of facial angle (FH‐NPog), palatal plane angle (PP‐FH), and AB plane angle (AB‐NPog); SNA, sella‐nasion‐A point; N perp‐Pt.A, distance between A point and nasion perpendicular line (a line extending through nasion, perpendicular to the FH plane); SNB, sellanasion‐B point; N perp‐Pog, distance between pogonion and nasion perpendicular line; SUM, sum of saddle angle (N‐S‐Ar), articular angle (S‐Ar‐Go), and gonial angle (Ar‐Go‐Me); PFH/AFH, posterior facial height(S‐Go)/anterior facial height (N‐Me); FH‐OP, FH plane to occlusal plane; FH‐MP, FH plane to mandibular plane; Interincisal angle, angle formed by long axes of maxillary to mandibular central incisors; U1‐FH, long axis of maxillary central incisor to FH line; IMPA, incisor mandibular plane angle; U6‐PP, distance between mesiobuccal cusp of maxillary first molar to palatal plane; U1, maxillary central incisor; L1‐APog (°), long axis of mandibular central incisor to A‐Pog line; L1‐APog (mm), distance between mandibular central incisal edge and A‐Pog line.

retraction, the C-lingual retractor was removed and brackets were bonded to close the remaining space and perform the finishing stage (Figure 50.4). Treatment Results The total treatment duration was 22 months. Class I malocclusion and normal overbite and overjet were ­ obtained. Using superimposition to compare the initial and final condition, there was 4.5 mm of retraction of the

upper incisors with controlled tipping and 3.5 mm of retraction of the lower incisors, while there was 2 mm of anchor loss in the upper molars and 3 mm of anchor loss in the lower molars. There was 1 mm extrusion of the upper incisors and 2 mm of intrusion of the lower incisors. There was no vertical movement both in the upper and lower molars. The protrusive lip was resolved and a favorable profile was achieved (Figure  50.5 and Table 50.1). (Continued )

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Section III  Clinical Applications of TADs

(a)

(e)

(b)

(c)

(d)

(f) Initial Progress 7M

Figure 50.4  Case 50.1: Treatment progress. Delivery of C-lingual retractor and bonding on the mandibular arch at two months (a), five months (b), nine months (c), and after lingual retractor was removed (d). (e) Lateral cephalogram. (f) Superimposition of initial (black) cephalometric tracings and after seven months of retraction using a C-lingual retractor (blue).

Chapter 50  TAD-assisted Lingual Retractors

Figure 50.5  Case 50.1: Final records and superimposition of lateral cephalogram tracings (pre-treatment, black; post-treatment, red).

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Section III  Clinical Applications of TADs

50.3 ­Anteroposterior Lingual Retractor The use of an anteroposterior lingual retractor (APLR) has been proposed to compensate for the limitations of the conventional lingual retractor. The main difference between the APLR and the C‐retractor is that the APLR is attached to the posterior segment. The teeth are grouped into three segments, so the orthodontic force is not concentrated on any individual tooth. Moreover, friction is minimal compared to that of conventional lingual brackets because the only site of friction during the sliding movement is between the posterior extension wire and the tube from the first molar.

50.3.1 Design The APLR includes an anterior and two posterior segments, which are connected to the TADs on the palate (Figure 50.6). 50.3.1.1  Anterior Segment

The anterior segment is similar to the C‐lingual retractor. Additionally, a 0.036‐in SS guidewire is soldered to the retraction hooks and extends distally through the tube of the posterior parts. 50.3.1.2  Posterior Segments

The second premolar, the first molar, and the second molar are splinted together into a single unit with a soldered

extension arm from the mesh of the first molar, which ends in a short tube (diameter 1 mm). The tube is generally parallel to the occlusal plane and functions as a sliding yoke. The guidewire from the anterior segment passes through the tube hole. The play between the posterior extension wire and the tube is 0.1 mm. 50.3.1.3  Accessory Parts

The TPA can be soldered to the extension arm from the mesh of the first molar. For intrusion or torque control of the posterior teeth, additional hooks can be attached to the TPA.

50.3.2 Biomechanics The APLR produces bodily movement with significant intrusion of the anterior teeth. The posterior extension wires give vertical stabilization to the anterior teeth, preventing an unwanted clockwise bowing effect of the anterior segment [18, 24, 25]. The APLRs can control torque and angulation of the anterior segments effectively and prevent unwanted canine tipping [25]. On the aspects of posterior segment, when the intrusive retraction force is applied, the kinetic energy from the guide bar also causes molar intrusion. Typically, the amount of intrusion of the posterior teeth is less than the anterior teeth, which results in flattening of the occlusal plane. In summary, the APLR exhibits good vertical control ability to incorporate the entire upper dentition, it can be advantageously applied in treatment of skeletal Class II hyperdivergent with gummy smile [24].

Path hole

Guide wire

Lever arm

TADs Posterior splint

Figure 50.6  Design of the APLR system.

Anterior splint

Chapter 50  TAD-assisted Lingual Retractors

Case 50.2  Patient A 22-year-old female patient came to the orthodontic clinic with the chief complaint of anterior protrusion. She had a convex profile, hypermentalis strain, gummy smile, and lip protrusion. Intraoral examination exhibited Class I malocclusion with a large overjet, deep bite, moderate anterior crowding on her mandibular arch, and deep curve of Spee. Her mandibular anterior teeth were in contact with the palatal mucosa. Cephalometric analysis revealed skeletal Class II with a retrognathic mandible, normovergent pattern, and slight labioversion of the maxillary and mandibular incisors. She had temporomandibular joint (TMJ) pain on the right side, and a history of TMJ dislocation. She was referred to a TMJ specialist and underwent splint treatment for one year. Upon completion of the splint therapy, there were no symptoms of temporomandibular disorder. Therefore, she decided to start orthodontic treatment (Figure 50.7 and Table 50.2). Diagnosis and Treatment Planning The patient was diagnosed as skeletal Class II, facial asymmetry and dental Class I with normovergent pattern, large overjet, deep bite, and anterior crowding. Since she wanted to resolve her lip protrusion and gummy smile, extraction of both maxillary and mandibular arches and intrusion of the maxillary anterior teeth were suggested. Although extraction of the first premolars in the maxillary arch and the second premolars in the mandibular arch was the first treatment option, the patient wanted to have the second premolar on the maxillary arch extracted because root canal treatment was planned on the maxillary left second premolar. She had short roots on her anterior teeth and since significant intrusion and bodily movement of maxillary anterior teeth was necessary, an APLR was planned for retraction. Treatment Progress The anterior section of the APLR was applied to the incisors, canines, and first premolars, while the posterior segment was applied to the first and second molars. Two lever arms of different lengths were connected between

the central incisor and lateral incisor. The guidewires started from the canine mesh and ran to the posterior tube hole. To reinforce the anchorage, a TPA was soldered to the posterior segments. Two TADs were inserted in the paramedian area of the palate. The APLR was bonded using transfer jigs with chemical cure adhesive. The anterior section was bonded first and the posterior sections were then slipped onto the guidewires. After delivery of the retractor, the second premolars were extracted and a retraction force of 300 g was applied on each side with elastic chains connected from the anterior retraction hooks to the TADs. At three months and six months after retraction, bonding failure occurred at the incisors but they were rebonded. The anterior segment also functioned as an anterior bite plane; therefore, deep bite correction was easily achieved. No significant anchorage loss was expected during the enmasse retraction of the first premolars, and the extraction spaces were closed gradually. After 11 months of retraction, the APLR was removed and brackets were bonded to close the remaining space and complete the finishing stage. In the mandibular arch, conventional treatment using full fixed appliances was performed (Figure 50.8). Treatment Results Total treatment time was 23 months. Class I ­malocclusion and normal overbite and overjet were obtained. Using superimposition to compare the initial condition with the changes after the APLR was removed 4.5 mm of retraction and 5 mm of intrusion of the upper incisors was observed without any torque loss, and the upper molars were intruded by 2 mm without significant anchor loss which resulted in flattening of occlusal plane up to 3.2°. Superimposition of the initial and final images showed protraction of the upper molars while the position of the upper incisors was maintained. As a result of intrusion of the entire maxillary arch, counterclockwise rotation of the mandible occurred, which contributed to the patient’s relaxed lip closure. Her gummy smile and protrusive lip were resolved, and she had a favorable profile (Figure 50.9 and Table 50.2). (Continued )

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Section III  Clinical Applications of TADs

Right

Left

Figure 50.7  Case 50.2: Initial records.

Chapter 50  TAD-assisted Lingual Retractors

Table 50.2  Case 50.2: Cephalometric measurements. Mean

Initial

Progress (11 mo)

Final

Maxilla–mandible relation ANB (°)

2.8

6.2

5.2

5.5

APDI (°)

85.8

66.0

70.0

68.0

81.7

81.0

81.0

80.5

2.0

3.0

3.0

2.5

Maxilla SNA (°) N perp‐Pt.A (mm) Mandible SNB (°)

79.0

74.8

75.8

75.0

N perp‐Pog (mm)

−0.3

−4.5

−3.0

−3.0

395.7

396.0

395.0

394.0

Divergency SUM (°) PFH/AFH (%)

70.0

65.8

66.7

61.4

FH‐OP (°)

5.9

10.0

8.0

9.5

FH‐MP (°)

25.4

24.5

23.0

23.5

Interincisal angle (°)

128.3

118.0

112.0

126.2

U1‐FH (°)

116.6

120.0

119.3

112.0

IMPA (°)

90.1

98.0

106.5

98.8

U6‐PP (mm)

25.0

25.0

24.0

24.0

Denture

U1 exposure (mm) L1‐APog (°) L1‐APog (mm)

4.0

7.0

3.7

4.3

23.3

24.2

33.5

25.5

4.5

3.4

6.0

2.5

ANB, A point‐nasion‐B point; APDI, anteroposterior dysplasia indicator, sum of facial angle (FH‐NPog), palatal plane angle (PP‐FH), and AB plane angle (AB‐NPog); SNA, sella‐nasion‐A point; N perp‐Pt.A, distance between A point and nasion perpendicular line (a line extending through nasion, perpendicular to the FH plane); SNB, sellanasion‐B point; N perp‐Pog, distance between pogonion and nasion perpendicular line; SNB, sella‐nasion‐B point; SUM, sum of saddle angle (N‐S‐Ar), articular angle (S‐Ar‐Go), and gonial angle (Ar‐Go‐Me); PFH/AFH, posterior facial height(S‐Go)/anterior facial height (N‐Me); FH‐OP, FH plane to occlusal plane; FH‐MP, FH plane to mandibular plane; Interincisal angle, angle formed by long axes of maxillary to mandibular central incisors; U1‐FH, long axis of maxillary central incisor to FH line; IMPA, incisor mandibular plane angle; U6‐PP, distance between mesiobuccal cusp of maxillary first molar to palatal plane; U1, maxillary central incisor; L1‐APog (°), long axis of mandibular central incisor to A‐Pog line; L1‐APog (mm), distance between mandibular central incisal edge and A‐Pog line.

(Continued )

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Section III  Clinical Applications of TADs

(e)

(a)

(b)

(c)

(d)

(f) -Initial -APLR removal 11M

Figure 50.8  Case 50.2: Treatment progress. (a, b) The APLR on the day of its delivery and at six months of retraction. (c) APLR removal at 11 months of retraction. (d) The distal end of guidewire indicates the amount of space closure. (e) Lateral cephalogram at APLR removal. (f) Superimposition of pre-treatment cephalometric tracings (black) and at APLR removal (blue).

Chapter 50  TAD-assisted Lingual Retractors

Figure 50.9  Case 50.2: Final records and superimposition of pre-treatment (black) and post-treatment (red) cephalometric tracings.

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Section III  Clinical Applications of TADs

50.4 ­Conclusion For treatment of lip protrusion, a lingual retractor combined with TADs offers effective vertical and torque control

of the anterior teeth by simple biomechanics with an esthetic advantage. In particular, the APLR results in significant intrusion and bodily retraction of anterior teeth concurrent with intrusion of the posterior teeth.

R ­ eferences 1 Roth RH. Treatment concepts using the fully preadjusted three‐dimensional appliance. In: Graber TM, Vanarsdall, R.L Jr., eds. Orthodontics: Current Principles and Techniques, 3rd edn. St. Louis, MO: Mosby, 2000, pp. 709–720. 2 Melsen B, Fotis V, Burstone CJ. Vertical force considerations in differential space closure. J Clin Orthod. 1990;24:678–683. 3 Jang HJ, Roh WJ, Joo BH, et al. Locating the center of resistance of maxillary anterior teeth retracted by Double J Retractor with palatal miniscrews. Angle Orthod. 2010;80:1023–1028. 4 Chung GM SS, Lee KJ, Chun YS, Mo SS. Finite element investigation of the center of resistance of the maxillary dentition in relation to alveolar bone loss. Korean J Orthod. 2009;39:83–94. 5 Pancherz H, Loffler A, Obijou C. Efficiency of root torquing auxiliaries. Clin Orthod Res. 2001;4:28–34. 6 Liang W, Rong Q, Lin J, Xu B. Torque control of the maxillary incisors in lingual and labial orthodontics: a 3‐dimensional finite element analysis. Am J Orthod Dentofacial Orthop. 2009;135:316–322. 7 Hong RK, Heo JM, Ha YK. Lever‐arm and mini‐implant system for anterior torque control during retraction in lingual orthodontic treatment. Angle Orthod. 2005;75:129–141. 8 Park YC, Choi YJ, Choi NC, Lee JS. Esthetic segmental retraction of maxillary anterior teeth with a palatal appliance and orthodontic mini‐implants. Am J Orthod Dentofacial Orthop. 2007;131:537–544. 9 Sung SJ, Jang GW, Chun YS, Moon YS. Effective en‐masse retraction design with orthodontic mini‐implant anchorage: a finite element analysis. Am J Orthod Dentofacial Orthop. 2010;137:648–657. 10 Kim JS, Kim SH, Kook YA, et al. Analysis of lingual en masse retraction combining a C‐lingual retractor and a palatal plate. Angle Orthod. 2011;81:662–669. 11 Nahm KY, Shin SY, Ahn HW, et al. Gummy smile correction using lingual orthodontics and augmented corticotomy in extremely thin alveolar housing. J Craniofac Surg. 2017;28:e599–e603. 12 Chung KR, Kook YA, Kim SH, et al. Class II malocclusion treated by combining a lingual retractor and a palatal plate. Am J Orthod Dentofacial Orthop. 2008;133:112–123.

13 Park JH, Tai K, Takagi M, et al. Esthetic orthodontic treatment with a double J retractor and temporary anchorage devices. Am J Orthod Dentofacial Orthop. 2012;141:796–805. 14 Park J, Cho HJ. Three‐dimensional evaluation of interradicular spaces and cortical bone thickness for the placement and initial stability of microimplants in adults. Am J Orthod Dentofacial Orthop. 2009;136:314.e1–12. 15 Kang S, Lee SJ, Ahn SJ, et al. Bone thickness of the palate for orthodontic mini‐implant anchorage in adults. Am J Orthod Dentofacial Orthop. 2007;131:S74–81. 16 Kang YG, Kim JY, Nam JH. Control of maxillary dentition with 2 midpalatal orthodontic miniscrews. Am J Orthod Dentofacial Orthop. 2011;140:879–885. 17 Asscherickx K, Vannet BV, Bottenberg P, et al. Clinical observations and success rates of palatal implants. Am J Orthod Dentofacial Orthop. 2010;137:114–122. 18 Seo KW, Kwon SY, Kim KA, et al. Displacement pattern of the anterior segment using antero‐posterior lingual retractor combined with a palatal plate. Korean J Orthod. 2015;45:289–298. 19 Chung KR. Lingual mechanotherapy by lingual bonded edgewise appliance. J Kyung Hee Univ Med Cent. 1986;2:87–106. 20 Chung KR, Oh MY, Ko SJ. Corticotomy‐assisted orthodontics. J Clin Orthod. 2001;35:331–339. 21 Kim SH, Park YG, Chung KR. Severe anterior openbite malocclusion with multiple odontoma treated by C‐lingual retractor and horseshoe mechanics. Angle Orthod. 2003;73:206–212. 22 Kim SH, Park YG, Chung KR. Severe Class II anterior deep bite malocclusion treated with C‐lingual retractor. Angle Orthod. 2004;74:280–285. 23 Chung KR, Kim SH, Lee BS. Speedy surgical‐orthodontic treatment with temporary anchorage devices as an alternative to orthognathic surgery. Am J Orthod Dentofacial Orthop. 2009;135:787–798. 24 Kwon SY, Ahn HW, Kim SH, et al. Antero‐posterior lingual sliding retraction system for orthodontic correction of hyperdivergent Class II protrusion. Head Face Med. 2014;10:22. 25 Hwang M, Ahn HW, Kwon SY, et al. Control of anterior segment using an antero‐posterior lingual sliding retraction system: a preliminary cone‐beam CT study. Prog Orthod. 2018;19:2.

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51 TADs and Invisalign: Making Difficult Movement Possible Joorok Park and Robert L. Boyd Department of Orthodontics, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA, USA

51.1 ­Introduction Clear aligners have become an increasingly popular appliance of choice for orthodontic treatment since the Invisalign® appliance was introduced by Align Technology in 1998. The clear aligner system has a clear esthetic advantage over other types of orthodontic appliance systems. In the early developmental stage of the Invisalign appliance, Boyd et  al. [1, 2] demonstrated successful clinical outcomes in orthodontic cases with mild to moderate crowding or spacing. The Invisalign system was shown to provide good clinical outcomes for cases with mild to moderately severe malocclusion [3–6]. More recently, clinicians have started to adopt the Invisalign appliance in more biomechanically demanding cases such as anterior open bite, four premolar extraction, and orthognathic surgery cases  [7–12]. Over the past two decades, the Invisalign appliance has evolved to deliver an improved biomechanical force system for challenging tooth movements. Depending on the degree and type of tooth movement, various features have been added to Invisalign aligners. These include optimized attachments, power ridges, precision bite ramps, and precision wings. Numerous designs of optimized attachments are available for different types of tooth movement and anchorage situations. There are a few indications where temporary anchorage devices (TADs) can aid in very challenging tooth movement together with Invisalign aligners.

51.1.1  Maximum Anchorage Retraction of both maxillary and mandibular anterior teeth with maximum anchorage requires TADs when using the Invisalign system. Unlike conventional fixed appliance systems, the Invisalign system cannot employ headgear, TPA, or Nance appliances for anchorage; however, TADs can provide the necessary absolute anchorage.

51.1.2  Deep Bite Control Correction of severe overbite is difficult with Invisalign appliances. A mild to moderate overbite can be well treated with help of a lingual bite ramp, but in brachycephalic patients who present with severe overbite, intrusion of incisors can be accomplished by using TADs.

51.1.3  Distalization of Mandibular Molars It has been shown that distalization of maxillary molars for correction of Class II malocclusion is predictable up to end-on Class II molar relationship [13]. Distalization of maxillary molars is usually accomplished with Class II elastics, but distalization of mandibular molars can be very difficult without the help of TADs.

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section III  Clinical Applications of TADs

Case 51.1  Absolute Anchorage Case Diagnosis A 30-year-old female presented with the chief complaints of crowding and lip protrusion (Figure 51.1). She presented with a convex profile and protrusion of both upper and lower lips. Skeletally, she showed mild Class II relationship (ANB, 4.1°) with a slightly high mandibular plane angle (FMA, 29.5°) (Table 51.1). Dentally, she exhibited mild crowding of upper and lower anterior teeth with excessive proclination of lower anterior teeth (L1NB, 38.4° and IMPA, 102°), which resulted in an acute

interincisal angle (U1-L1, 113°). Her molars and canines were in Class I relationship with normal overbite and overjet. Treatment Options One apparent treatment option was to extract the four first or second bicuspids in order to relieve crowding and reduce proclination of the anterior teeth. However, the patient preferred the non-extraction treatment option with Invisalign. Interproximal reduction (IPR) can create

Figure 51.1  Case 51.1: Pre-treatment photographs and radiographs.

Chapter 51  TADs and Invisalign: Making Difficult Movement Possible

Table 51.1  Case 51.1: Cephalometric measurements. Pre-treatment Post-treatment

SNA (°)

83.7

83.8

SNB (°)

79.6

78.7

ANB (°)

4.1

4.5

FMA (FH-MP) (°)

29.5

30.7

U1‐SN (°)

108.1

100.5

U1‐NA (°)

24.4

16.7

6.8

2.9

L1‐NB (°)

38.4

29.2

L1‐NB (mm)

10.0

7.1

U1‐NA (mm)

IMPA (L1‐MP) (°)

102.0

92.9

Interincisal angle (U1‐L1) (°)

113.1

129.0

Upper lip‐E plane (mm)

2.0

0.6

Lower lip‐E plane (mm)

6.2

3.7

SNA, Sella‐nasion‐A point; SNB, Sella‐nasion‐B point; ANB, A point‐nasion‐B point; FMA, Frankfort mandibular plane angle; U1‐SN, long axis of maxillary central incisor to sella‐nasion plane; U1 ‐ NA, maxillary central incisor to nasion‐A point line; L1 ‐ NB, mandibular central incisor to nasion‐B point line; IMPA, incisor mandibular plane angle; Interincisal angle angle formed by long axes of maxillary to mandibular central incisors; Upper lip‐E plane, distance between upper lip anterior point and E line (esthetic plane of Ricketts; line that passes through the tip of the nose and soft tissue pogonion); Lower lip‐E plane, distance between lower lip anterior point and E line.

a few millimeters of space, however, this would not be enough to relieve crowding and significantly retract the anterior teeth at the same time. A tooth setup with 0.5 mm IPR between the right first premolar to the left first premolar in the ClinCheck software revealed that only 1–2 mm of incisor retraction was possible, even with maximum anchorage (Figure  51.2c,d). More retraction of  the incisors was necessary to reduce lip fullness. Therefore, TADs were proposed for maximum retraction as well as total arch distalization to maximize incisor retraction. Treatment Progress The tooth setup in ClinCheck consisted of alignment of rotated teeth and 0.5 mm of IPR between mesial of the right first premolar to mesial of the left first premolar in maxillary and mandibular arches (Figure  51.2). Up to 0.5 mm of IPR was assessed to be reasonable on this patient’s incisors due to their large enamel thickness. Using the IPR spaces, both maxillary and mandibular

anterior teeth were uprighted and retracted with maximum anchorage. Posterior TADs (1.3–1.2 mm diameter, 6 mm length; AbsoAnchor® SH1312-06, Dentos, Daegu, South Korea) were placed into the buccal alveolar bone between the second premolars and first molars in the maxilla and mandible. Clear buttons were bonded close to the gingival margin on the labial surfaces of maxillary and mandibular canines. Class I elastics (3/16-in, 4.5 oz) were used from the TADs to the clear buttons on the canines full-time for total arch distalization (Figure 51.3). The first set of aligners consisted of 18 aligners. After the first set of aligners were completed, further reduction of lip fullness was deemed to be necessary. In the first case refinement, additional IPR (0.3 mm) was prescribed in between the premolars, and total arch distalization was continued by using the TADs as anchorage. Sixteen aligners were fabricated for the case refinement. Treatment Results After treatment, the patient showed less fullness of her lips. The crowded anterior teeth were aligned and uprighted. Good interdigitation of posterior teeth was achieved and the initial overjet and overbite relationships were maintained (Figure 51.4). Post-treatment lateral cephalometric analysis showed that the upper and lower lips were retracted by 1.4 mm and 2.5 mm, ­respectively, from the E-plane (Table  51.1). U1-NA showed significant reduction by 7.7° and 3.9 mm and L1-NB showed similar reduction by 9.2° and 2.9 mm. The interincisal angle was decreased by 15.9°, achieving an ideal angle of 129°. The lateral cephalometric superimposition showed retraction of the lips and incisors (Figure  51.5). Both maxillary and mandibular molars were distalized approximately 1–2 mm while their vertical positions were maintained. Due to the limited space available in the interradicular area, more than 2 mm of distalization requires the TADs to be repositioned. Instead of placing the TADs on the buccal alveolar bone between the roots, infrazygomatic crest and mandibular buccal shelf TADs may be used to further distalize the posterior teeth [14]. The biomechanics of total arch distalization with TADs results in extrusion of incisors. This extrusive side effect was compensated for by prescribing intrusion of incisors in ClinCheck. In the cephalometric superimposition, the vertical positions of the anterior teeth were well maintained during their retraction. (Continued )

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(a)

(b)

(c)

(d)

Figure 51.2  Invisalign ClinCheck simulation. (a) Pre-treatment. (b) Treatment simulation with 0.5 mm of IPR across the anterior teeth of the maxilla and mandible. (c, d) Superimposition of pre-treatment (blue) and post-treatment (white) simulation shows that the anterior teeth can be retracted by 1–2 mm when maximum anchorage was used.

Figure 51.3  Case 51.1: Class I elastics were worn from the posterior TADs to buttons bonded on the canines for maximum retraction of anterior teeth and total arch distalization.

Chapter 51  TADs and Invisalign: Making Difficult Movement Possible

Figure 51.4  Case 51.1: Post-treatment photographs and radiographs.

(Continued )

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Figure 51.5  Case 51.1: Lateral cephalometric superimposition: pre-treatment (black), post-treatment (red).

Case 51.2  Deep Bite Case Diagnosis A 32-year-old male presented with the chief complaints of deep bite and the need to restore anterior teeth. He reported a habit of bruxism which resulted in severe enamel wear on incisal edges, the lingual surface of his maxillary incisors and the occlusal surfaces of his posterior teeth. The patient presented with a straight and brachycephalic profile and 3 mm of maxillary incisor display with lips at rest (Figure 51.6). Skeletally, he showed Class I relationship (ANB, 2.1°) and an extremely low mandibular plane angle (FMA, 8.2°) (Table 51.2). Dentally, he had a slightly Class II molar and canine relationship on the right side and 100% deep overbite. Maxillary and mandibular anterior teeth had an upright inclination (U1-NA, 16.2°; L1-NB, 8.1°; IMPA, 87.4°) which resulted in an obtuse interincisal angle (U1-L1, 153.6°). Treatment Options The restorative dentist planned to restore both the maxillary and mandibular anterior teeth with crowns which would increase the length of the clinical crown by 1–2 mm. Intrusion of both maxillary and mandibular incisors was planned in order to create vertical clearance between

the maxillary and mandibular incisors. Slight interproximal spacing between the incisors was also planned to facilitate fabrication of crowns with adequate widths. An Invisalign appliance was recommended because of its potentially protective effect against further wear on the incisal edges and occlusal surfaces. Incisor intrusion (3 mm on the maxillary incisors and 4 mm on the mandible) was planned for the anterior teeth which would provide 1–2 mm of anterior open bite and sufficient clearance for the future restorations. The biggest challenge of the treatment plan was intruding his incisors because of his brachycephalic profile with low mandibular plane angle. A bite ramp is automatically added to the Invisalign on the lingual side of the maxillary incisors when a significant amount of intrusion is planned. We anticipated that 7 mm of intrusion would not be achieved in this case with the bite ramp alone. Therefore, anterior TADs were recommended to facilitate intrusion of the incisors. Treatment Progress The tooth setup in the ClinCheck consisted of alignment of rotated teeth and 3 mm of intrusion of maxillary ­incisors and 4 mm intrusion of mandibular incisors.

Chapter 51  TADs and Invisalign: Making Difficult Movement Possible

Figure 51.6  Case 51.2: Pre-treatment photographs and radiographs.

The  ­incisors were proclined and displaced anteriorly while 0.5 mm of interdental space was created between the incisors (Figure 51.7). The first set of aligners consisted of 18 aligners which were used to intrude the incisors simply with just the bite ramp. After the first set of aligners were completed, the overbite improved only by 1 mm, so at this point it was determined that TADs would be necessary to intrude the incisors (Figure 51.8a). In the first case refinement, four anterior TADs (1.3– 1.2 mm diameter, 6 mm length; AbsoAnchor SH1312-

06) were placed into the buccal alveolar bone between the lateral incisors and canines of the maxilla and mandible (Figure  51.8b). Clear buttons were bonded close to the gingival margin on the labial surface of the maxillary incisors. Elastics (1/4-in, 4.5 oz) were used from each TAD to the four buttons on the incisors full-time to intrude the incisors as a unit. The mandibular incisors were intruded by having elastics (3/16-in, 4.5 oz) worn from the elastic cuts on the lingual side of the aligners around the lateral incisors to the TADs on the labial side. (Continued )

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Table 51.2 

Case 51.2: Cephalometric measurements. Pre-treatment

SNA (°)

84.8

SNB (°)

82.8

ANB (°)

2.1

FMA (FH‐MP) (°)

8.2

AFH (N‐Me) (mm)

114.9

U1‐SN (°)

101.1

U1‐NA (°)

16.2

U1‐NA (mm)

0.0

L1‐NB (°)

8.1

L1‐NB (mm)

−0.8

IMPA (L1‐MP) (°)

87.4

Interincisal angle (U1‐L1) (°) Stm‐U1 (mm)

153.6 3.1

Upper lip‐E plane (mm)

−7.9

Lower lip‐E plane (mm)

−5.0

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐ nasion‐B point; FMA, Frankfort mandibular plane angle; AFH (N‐Me), anterior facial height, distance between nasion to menton; U1‐SN, long axis of maxillary central incisor to sella‐nasion plane; U1‐NA, maxillary central incisor to nasion‐A point line; L1‐NB, mandibular central incisor to nasion‐B point line; IMPA, incisor mandibular plane angle; Interincisal angle angle formed by long axes of maxillary to mandibular central incisors; Stm‐U1, stomion superius to lower central incisor; Upper lip‐E plane, distance between upper lip anterior point and E line (esthetic plane of Ricketts; line that passes through the tip of the nose and soft tissue pogonion); Lower lip-E plane, distance between lower lip anterior point and E line.

Figure 51.7  Case 51.2: ClinCheck simulation demonstrating the planned intrusion of incisors to create clearance for future crown restorations for the incisors.

Treatment Results After the first case refinement was completed, the maxillary incisors were intruded successfully by 2–3 mm (Figure  51.8c). More intrusion was observed on the maxillary lateral incisors than on the central incisors because the TADs were closer to the lateral incisors, which resulted in a greater intrusive force on the lateral incisors than on the central incisors. Another potential location for TAD placement would be between the lateral and central incisors if there is sufficient interradicular space. The patient still needed another 3–4 mm of intrusion of his mandibular anterior teeth. Successful intrusion of maxillary incisors provided adequate clearance to bond labial buttons on the mandibular anterior teeth from which elastics could be worn or an elastomeric chain

(a)

(b)

(c) Figure 51.8  Case 51.2: (a) Finish of the first set of clear aligners: incisors were not intruded effectively with the bite ramp alone. (b) Case refinement no. 1 (start): anterior TADs were placed to facilitate the intrusion of incisors. (c) Case refinement no. 1 (finish): maxillary incisors were intruded as well.

Chapter 51  TADs and Invisalign: Making Difficult Movement Possible

could be tied to the mandibular TADs for more effective intrusive mechanics. The second case refinement included leveling of the maxillary incisors and additional intrusion of the mandibular anterior teeth after bonding buttons for elastics

or elastomeric chain. The desired overbite is to create 1–2 mm of anterior open bite. Interproximal space was created as planned, and larger spaces were prepared distal to the narrow maxillary lateral incisors.

Case 51.3  Distalization of Mandibular Molars Diagnosis A 41-year-old male presented with the chief complaints of “underbite and open bite.” The patient had a history of previous orthodontic treatment with orthognathic surgery (maxillary advancement and genioplasty) which

improved his anterior crossbite at the time of the surgery in his late adolescent age. It appeared that either there was a relapse after the orthognathic surgery or there was a late mandibular growth. The patient presented with a straight profile (Figure  51.9). Skeletally, he showed mild Class III

Figure 51.9  Case 51.3: Pre-treatment photographs and radiographs.

(Continued )

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r­ elationship (ANB, −0.4°) with a large chin projection (Pog-NB, 7 mm) (Table  51.3). Dentally, the molar and canine relationship was end-on Class III on the right side and more than end-on Class III on the left side. Bilateral posterior lingual crossbite and anterior crossbite were present. He showed 2 mm of anterior open bite and −2 mm of overjet. The mandibular dental midline was deviated to the right by 2 mm. Maxillary incisors were slightly proclined (U1-NA, 29°) while mandibular incisors showed adequate inclination (L1-NB, 27.5°; IMPA, 97.2°). Mild crowding was observed on the maxillary and mandibular anterior teeth. When smiling, 100% of the maxillary incisors were displayed. There was a noticeable discoloration of the mandibular canine crowns; however, the teeth were vital and caused no pain or discomfort. There was no history of trauma to the canines. Treatment Options A surgical option was recommended by other orthodontists; however, the patient preferred a non-surgical treatment option. His main desire was to improve his anterior crossbite and open bite. The Invisalign appliance was recommended to address his chief complaint. Clear aligners not only provide good vertical control but also can effectively correct an anterior open bite [10]. Mandibular posterior TADs were also recommended for total arch distalization of the mandibular dentition to improve the anterior crossbite and Class III malocclusion. Extensive use of Class III elastics alone was not ­considered because this would result in excessive proclination of the maxillary incisors and negatively affect the smile esthetics. The non-surgical treatment option had two potential limitations: (i) the Class III malocclusion might not be completely corrected, especially on the left side, due to the large degree of distalization of the mandibular teeth required to correct the Class III molar relationship and (ii) the posterior crossbite might not be fully corrected. The patient was informed of the limitations. Treatment Progress The following was planned in the Invisalign Clincheck software (Figure 51.10): ●●

●●

Two millimeters of maxillary arch expansion was planned on each side of the posterior teeth. Class III correction was requested by employing the sequential distalization protocol of the mandibular posterior teeth. One millimeter of Class III correction was planned with anterior displacement of the maxillary arch with Class III elastics.

Table 51.3  Case 51.3: Cephalometric measurements. Pre-treatment

Post-treatment

SNA (°)

72.8

72.8

SNB (°)

73.2

73.5

ANB (°)

−0.4

−0.7

FMA (FH‐MP) (°)

18.8

18.8

Pog‐NB (mm)

7.0

6.4

29.0

29.0

7.6

8.2

27.5

24.5

7.6

5.9

IMPA (L1‐MP) (°)

97.2

93.9

Interincisal angle (U1‐L1) (°)

124.0

127.2

U1‐NA (°) U1‐NA (mm) L1‐NB (°) L1‐NB (mm)

Upper lip‐E plane (mm)

−9.6

−9.7

Lower lip‐E plane (mm)

−6.8

−6.9

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; FMA, Frankfort mandibular plane angle; Pog ‐ NB, pogonion to nasion ‐ B point; U1 ‐ NA (°), long axis of maxillary central incisor to nasion‐A point line; U1‐NA (mm), distance between incisal tip of maxillary central incisor and nasion‐A point line; L1‐NB (°), long axis of mandibular central incisor to nasion‐B point line; L1‐NB (mm), distance between incisal tip of mandibular central incisor and nasion‐A point line; IMPA, incisor mandibular plane angle; Interincisal angle angle formed by long axes of maxillary to mandibular central incisors; Upper lip‐E plane, distance between upper lip anterior point and E line (esthetic plane of Ricketts; line that passes through the tip of the nose and soft tissue pogonion); Lower lip‐E plane, distance between lower lip anterior point and E line.

●●

Closure of the anterior open bite was planned by 1 mm of extrusion of the mandibular incisors and 0.5 mm of intrusion on each maxillary and mandibular posterior tooth. It was planned to maintain the initial vertical position of the maxillary incisors.

Posterior TADs (1.4 mm diameter, 6 mm length; VectorTAS, Orange, CA, USA) were placed into the buccal alveolar bone between the second premolars and first molars of the mandible. Buttons were bonded close to the gingival margin on the labial surface of the mandibular canines. NiTi coil springs from the TADs to the buttons on the canines delivered 250 g of retraction force on each side. Light Class III elastics (1/4-in, 4.5 oz) were used on both sides simultaneously (Figure 51.11a,b). The first set of aligners consisted of 32 aligners. After the mandibular posterior teeth were sequentially distalized, spaces mesial to the mandibular canines were observed when the first set of aligners was completed.

Chapter 51  TADs and Invisalign: Making Difficult Movement Possible

The mandibular canines showed excessive distal-in rotation, more so on the right canine. At the incisors, positive overjet and overbite were achieved, but the posterior crossbite was not yet corrected (Figure 51.11c,d). On the case refinement, the following was planned in the Invisalign ClinCheck software:

1)  Close spaces mesial to the mandibular canines and derotate the canines. 2)  Add power ridges on the mandibular incisors to increase labial crown inclination (or add more positive crown torque) to prevent lingual tipping during retraction.

(a)

(b)

Figure 51.10  (a) Pre-treatment. (b) Simulation of orthodontic treatment in Invisalign’s ClinCheck software shows total arch distalization of mandibular arch.

(a)

(b)

(c)

(d)

Figure 51.11  (a) The setup for the total arch distalization of the mandibular dentition included NiTi coil springs attached from the posterior TADs to buttons on mandibular canines and Class III elastics. (b) Progress after three months shows slight interdental spaces opening in the mandibular incisors. (c) Progress after six months shows more interdental spaces opened, distalization of the mandibular arch, and anterior teeth are in contact. (d) Finished results of first set of aligners show positive overjet and overbite, improved molar and canine relationship. Spaces mesial to mandibular canines can be used to aid in derotation of the canines and retract the incisors further.

(Continued )

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3)  Expand the maxillary posterior teeth further. 4)  Continue Class III correction mostly on the left side by using precision hooks on the mandibular first premolar. Twenty-nine aligners were fabricated for the case refinement. Treatment Results The patient’s main concern  –  anterior open bite and crossbite  –  have been addressed successfully (Figure  51.12). The soft tissue profile does not display

any appreciable change. Positive overbite and overjet have been obtained. The Class III molar and canine relationship has improved significantly; however, 2 mm of Class III molar and canine relationship still remains on the left side. The mandibular dental midline has not been fully corrected. Cephalometrically, the mandibular incisors were retracted and slightly uprighted (L1-NB, 5.9 mm/24.5°; IMPA, 93.9°), while the maxillary incisors were protracted slightly (U1-NA, 8.2 mm) (Table 51.3). Skeletal cephalometric measurements were maintained. Lateral

Figure 51.12  Case 51.3: Post-treatment photographs and radiographs.

Chapter 51  TADs and Invisalign: Making Difficult Movement Possible

c­ephalometric superimposition showed that extrusion and retraction of the mandibular incisors were the main mode of improving anterior open bite and crossbite (Figure  51.13). Mandibular molars were distalized by approximately 3 mm with good vertical control. Biomechanics of total arch distalization with TADs tend to extrude incisors and intrude the molars [15]. In this case, extrusion of the incisors and controlling the

v­ ertical positions of the molars helped to improve the anterior open bite. Due to the limited interradicular space available, additional distalization of the left side was difficult without repositioning the TAD. Instead of placing the TADs on the buccal alveolar bone between the roots, buccal shelf TADs could have been used to further distalize the left side [15].

Figure 51.13  Case 51.3: Cephalometric superimposition: pre-treatment (black), post-treatment (red).

51.2 ­Conclusions By utilizing TADs, Invisalign clear aligners can be used as an effective appliance to treat a variety of challenging malocclusions. TADs can provide absolute anchorage

for maximum retraction of incisors to reduce bimaxillary protrusion, to intrude incisors in severe deep bite cases, and to distalize the entire mandibular dentition in severe Class III malocclusions with good vertical control.

R ­ eferences 1 Boyd RL, Miller RJ, Vlaskalic V. The Invisalign system in adult orthodontics: mild crowding and space closure. J Clin Orthod. 2000;34:203–213. 2 Boyd RL, Vlaskalic V. Three‐dimensional diagnosis and orthodontic treatment of complex malocclusions with the Invisalign appliance. Semin Orthod. 2001;7:274–293. 3 Kamatovic M. A Retrospective Evaluation of the Effectiveness of the Invisalign Appliance Using the PAR and Irregularity Indices. Toronto, Canada: University of Toronto, 2004.

4 Lagravère MO, Flores‐Mir C. The treatment effects of Invisalign orthodontic aligners: a systematic review. J Am Dent Assoc. 2005;136:1724–1729. 5 Rossini G, Parrini S, Castroflorio T, et al. Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod. 2015;85:881–889. 6 Papadimitriou A, Mousoulea S, Gkantidis N, Kloukos D. Clinical effectiveness of Invisalign® orthodontic treatment: a systematic review. Prog Orthod. 2018; 19:37.

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7 Boyd RL. Complex orthodontic treatment using a new protocol for the Invisalign appliance. J Clin Orthod. 2007;42:525–547. 8 Boyd RL. Surgical‐orthodontic treatment of two skeletal Class III patients with Invisalign and fixed appliances. J Clin Orthod. 2005;39:245–258. 9 Boyd RL. Esthetic orthodontic treatment using the invisalign appliance for moderate to complex malocclusions. J Dent Educ. 2008;72:948–967. 10 Garnett BS, Mahood K, Nguyen M, et al. Cephalometric comparison of adult anterior open bite treatment using clear aligners and fixed appliances. Angle Orthod. 2019;89:3–9. 11 Bowman SJ, Celenza F, Sparaga J, et al. Creative adjuncts for clear aligners: part 3: extraction and interdisciplinary treatment. J Clin Orthod. 2015;49:249–262.

12 Khosravi R, Cohanim B, Hujoel P, et al. Management of overbite with the Invisalign appliance. Am J Orthod Dentofacial Orthop. 2017;151:691–699.e2. 13 Ravera S, Castroflorio T, Garino F, et al. Maxillary molar distalization with aligners in adult patients: a multicenter retrospective study. Prog Orthod. 2016;17:12. 14 Chang CH, Lin JS, Roberts WE. Failure rates for stainless steel versus titanium alloy infrazygomatic crest bone screws: a single‐center, randomized double‐blind clinical trial. Angle Orthod. 2019;89:40–46. 15 Roberts WE, Viecilli RF, Chang C, et al. Biology of biomechanics: finite element analysis of a statically determinate system to rotate the occlusal plane for correction of a skeletal Class III open‐bite malocclusion. Am J Orthod Dentofacial Orthop. 2015;148:943–955.

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52 The Use of TADs with Clear Aligners for Asymmetry Correction William J. Kottemann Private Practice, Minneapolis, MN, USA

52.1 ­Introduction The need to intrude posterior teeth in clinical practice is a frequently encountered challenge. Individual teeth may have over-erupted due to missing opposing teeth in an older adult, while full segments of posterior teeth may need to be intruded to close an anterior open bite. The use of temporary anchorage devices (TADs) to intrude posterior teeth has become the treatment of choice over the last several years. Park et al. [1] described intruding posterior teeth with TADs as early as 2003. Other researchers also reported similar treatments [2–6]. Kravitz et al. [7] reviewed the studies published at the time, outlining the application, placement, and biological response of orthodontic TADs specific to molar intrusion. TAD usage with clear aligners described their use with the Invisalign® system (Align Technology, Inc, Santa Clara, CA, USA) to aid in anchorage for extractions cases [8]. Later, authors began describing their experience with using TADs and clear aligners to intrude teeth, both in the posterior regions to close anterior open bites and in the anterior region, to level deep bite cases [9–13].

The purpose of the chapter is to show specifically how to intrude or extrude teeth with TADs and clear aligners to level the occlusal plane in cases of skeletal asymmetry due to growth imbalances or iatrogenic causes. Essentially, a  subdivision of anterior open bite correction with clear aligners and TADs will be examined.

52.2 ­Case Studies Two cases with different types of asymmetries that were effectively treated with intrusion and extrusion of groups of teeth will be reviewed. Tooth movement was accomplished either through direct application of force from the TAD to the tooth via orthodontic elastics to a button or hook bonded to the tooth, or from application of force to the aligner itself, to provide a more widely distributed force, intruding several teeth at once. These unilateral or asymmetric techniques have been previously reported for treating cases to intrude blocks of teeth for restorative ­reasons [14, 15].

Case 52.1  Patient was a 37-year-old female. Her chief complaint was crooked front teeth and a slant to her smile. Findings: Class I malocclusion, moderate crowding, narrow arches, both maxilla and mandible canted downward on right side, producing increased gingival display of the maxillary right quadrant (Figure 52.1). The treatment plan was to expand the arches and use interproximal reduction as needed in the anterior region to alleviate the crowding. The leveling of the cant of the occlusal plane would be corrected by the placement of a TAD on the right side, between the roots of the maxillary

first and second premolars. Elastic traction from the TAD to the teeth or the aligner would then be applied. The following special instructions were added to the patient’s ClinCheck®: Broad arch form. Note the uneven smile. Patient will have maxillary right posterior teeth intruded with use of a TAD and elastics. Maxillary arch overcorrection: Rotate 2,1|1,2 distal-out 5°. Move 1| lingual 0.2 mm. Mandibular arch overcorrection: Move 3,1|2 labial. Thank you. (Continued )

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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The treatment plan assumed that as the maxillary posterior teeth were being intruded, the mandibular teeth would be extruded. Therefore, the ClinCheck for the case was set up without regard to the vertical movement of the posterior teeth. It was not necessary to precisely determine the amount of intrusion of the maxillary teeth or the amount of extrusion of the mandibular teeth in the ClinCheck because the amount of overall movement would be determined by the results of the traction from the TAD. This is analogous to holding study models by hand, with teeth in occlusion. Tilting the models upward on one side has no effect on the individual fit or orientation of the teeth with one another. After treatment was initiated, the patient declined to have the TAD placed due concerns of discomfort. It was explained to the patient that without the use of a TAD, the teeth would all be straightened, but the “slant” to her smile would remain unchanged. As the treatment neared completion, the patient was satisfied with her tooth alignment, but now decided that she wanted her cant to be corrected after all. A TAD was then placed as originally planned. However, it would now primarily be applied to her Vivera® retainers, because she only had four aligners left in her remaining active treatment. It was anticipated that an additional 12–15 months would be required to level the cant. The TAD was a typical size for posterior placement, self-tapping and 8 mm in length [1, 16]. It was placed using topical anesthetic. A 3/16-in, 61/2 oz

elastic was stretched from the TAD over the occlusal surface of the aligner, secured by a small notch cut into the aligner with a crown and bridge scissors (Figure 52.2a). The patient wore the retainers and her elastics fulltime initially for a few months and switched to evening and then bedtime wear after that. After six months of elastic wear into the retention period, a posterior open bite was produced as a result of good intrusion of the maxillary right side (Figure 52.2b). Once it was confirmed that good intrusion of the maxillary arch had taken place, traction was then applied to the lower arch with a 5/16-in, 4½ oz elastic from the TAD directly to the mandibular teeth, rather than attaching to the retainer. By pulling directly on the teeth, it was believed that extrusion would be more effective. Pulling on the aligners would run the risk of merely dislodging the aligners. Buttons were bonded to the mandibular right first molar and first premolar (Figure 52.2c). After 12 months, the posterior open bite was closed as a result of the extrusion of the mandibular right posterior teeth (Figure 52.2d). From 12 to 18 months, elastic traction was alternated between the maxillary arch and mandibular arch, to level the cant a little more. At this point the patient’s wear time was only while sleeping. After 18 months of bedtime wear with retainers, the patient decided to discontinue elastics wear. The patient was satisfied with the esthetic changes at this point and

Figure 52.1  Case 52.1: Pre-treatment photographs and radiographs.

Chapter 52  The Use of TADs with Clear Aligners for Asymmetry Correction

(a)

(b)

(c)

(d)

Figure 52.2  Case 52.1: (a) TAD and elastics in place on upper retainer. (b) Open bite created by elastic traction to maxillary right posterior teeth. (c) Elastic traction applied from TAD to mandibular right posterior teeth. (d) Bite closed after extrusion of mandibular right posterior teeth.

(Continued )

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(a)

(b)

Figure 52.3  Case 52.1: (a) Final photographs at TAD removal. (b) Comparison of pre- and post-treatment.

elected to have the TAD removed. A reasonable improvement in the cant of the occlusal plane was achieved. A noticeable decrease in the maxillary posterior gingival display on the right side also occurred (Figure 52.3). Case Synopsis Eight months of active treatment, 17 aligners changed every two weeks, TAD placed at time of retainer placement;

Vivera retainers made at stage 15; elastics worn primarily at bedtime for 18 months. Summary Although there was a significant correction in the cant, it is believed that perhaps more correction could have been achieved with full-time wear of elastics to the TAD during the active treatment phase, when the patient was more highly motivated.

Case 52.2  Patient was a 60-year-old female, with a chief complaint that her teeth no longer touched each other in the front or on the left side. Findings: Class II malocclusion, previous orthodontics with four premolars removed, severe anterior open bite and left posterior open bite due to a shortened right condyle and over-eruption of the maxillary right posterior teeth. The patient reported that over the previous 10 years, her smile had become “more and more slanted downward” on her right side. It was discovered that she had an osteochondroma within her right condyle. She consulted with an oral surgeon, who performed an aggressive surgical removal of the tumor, roughly 18 months prior to the acquisition of her initial orthodontic records. The surgical result produced a shortened overall ramus height on the right side, causing the anterior open bite (Figure 52.4). In contrast to the previous case, this patient’s treatment plan did call for the intrusion of both the maxillary and mandibular right posterior teeth. It was apparent that there had been a compensatory over-eruption of the posterior maxillary and mandibular teeth, as the right condyle grew in length, due to the osteochondroma.

Therefore, it was planned to intrude the teeth back towards their original positions. The posterior needed to be intruded to allow the bite to close in the anterior and left posterior segments, through autorotation of the mandible [16]. Skeletal anchorage was planned for by the placement of TADs in both upper and lower right posterior segments. The patient was cautioned that anterior vertical elastic wear or even the possibility of a surgical revision to lengthen the right ramus could still be required, if intrusion of the teeth did not occur. The Invisalign ClinCheck setup included 2 mm of intrusion on the right side, in both arches. No “Special Instructions” other than for overcorrections of rotations and labiolingual movement of the teeth were included in the case submission. The ClinCheck showed a “bite jump” that is intended to mimic the autorotation of the mandible. However, the software currently can only show a vertical movement when there is a “bite jump.” There is no provision to show any anteroposterior change that would occur in the mouth, due to rotation around the condylar axis. In other words, the ClinCheck does not show the forward positioning of the mandible that is produced by counterclockwise rotation of the mandible as it closes.

Chapter 52  The Use of TADs with Clear Aligners for Asymmetry Correction

Figure 52.4  Case 52.2: Pre-treatment photographs and radiographs.

As in the previous patient, elastic traction was applied from the TAD, over the occlusal surface of the aligner, secured by a notch on the lingual gingival margin of the aligner. The 3/16-in, 6½ oz elastic was changed twice daily and worn full-time. Placement of the TADs did not occur until stage 13, because good intrusion of the teeth was occurring on its own as programmed by the ClinCheck software (Figure 52.5a). After the initial set of aligners had been worn, it was decided to order an additional set of aligners to allow for more intrusion of the posterior teeth and retraction of the maxillary anterior teeth. Interproximal reduction between all the maxillary teeth was also performed to allow for retraction of the maxillary anterior teeth, to reduce the overjet. At the appointment prior to placing the Vivera retainers, it was determined that the lower TAD was becoming loose. A decision was made to remove it, rather than replace it, because there was no additional intrusion of posterior teeth planned in the mandibular arch beyond this stage of aligners. The upper TAD remained in place during part of the initial retention period to allow for continued intrusion of the maxillary posterior teeth (Figure 52.5b). After two months of additional elastic wear, the TAD was removed. Case Synopsis Fifteen months of active treatment, 21 initial aligners changed every two weeks, TADs placed at stage 13. Five additional aligners changed every two weeks.

Equilibration performed at retainer placement. TADs removed after two months of Vivera retainer wear. Summary A more aggressive treatment approach would have called for placement of the TADs at the beginning of the treatment. It is likely that the treatment time would have been reduced with such an approach. As noted by the comparison of the initial and final photos, a significant improvement was made in the cant of the occlusal plane by the intrusion of the maxillary right posterior teeth (Figure 52.6). An alternative treatment plan would be to have individual tooth intrusion take place throughout the treatment, using adjacent teeth for anchorage. This technique has been shown to produce good results without the use of TADs. However, a longer treatment time is required to accommodate the individual tooth movements and anchorage requirements. The patient returned for follow-up 21 months posttreatment. As can be seen from the post-treatment records, the treatment results appear to be stable. A positive remodeling of the right condyle also appears to be taking place. The mandibular plane angle closed by slightly over 3° when compared to her initial cephalogram. The superimposition of the initial cephalometric tracing and the follow-up tracing indicate that the mandibular plane angle closed as a result of the posterior teeth intrusion and the overjet was significantly reduced (Figure 52.7). (Continued )

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Figure 52.5  Case 52.2: (a) Elastic attachment to upper and lower right TADs on aligners. (b) Elastic attachment to upper retainer with broad insertion to retainer.

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Figure 52.6  Case 52.2: (a) Final photographs. (b) Comparison of pre- and post-treatment.

Chapter 52  The Use of TADs with Clear Aligners for Asymmetry Correction

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Figure 52.7  Case 52.2: (a) Retention (21 months post-treatment) photographs. (b) Panoramic radiograph showing positive remodeling in right condyle. (c) Lateral cephalogram showing decrease in mandibular plane angle compared to pre-treatment radiograph. (d) Lateral cephalometric superimposition: pre-treatment (black) and retention (green).

52.3 ­Conclusions A common thread in these case reports was the continuation of TAD and elastic wear well into the retention period. This is a clear advantage over fixed appliances, where the patient is usually quite anxious to have their appliances removed towards the end of treatment. With clear aligners, the patient can decide how long to continue with the esthetic correction during the retention phase. As was demonstrated with the first case report, it is possible to achieve good results with only bedtime wear of clear aligners/retainers and elastics.

The use of TADs in these cases provided an efficient means to level the arches. Treatment times for both cases were 15 months or less. Earlier application of the TADs will shorten the overall length of active treatment time required for leveling the arches. The evolution of TAD usage in orthodontics has been a rapid one, starting first with fixed appliances and carrying over to clear aligner appliances. The evolution of TADs with clear aligners has perhaps been even quicker. The correction of skeletal asymmetries has always been challenging due to anchorage concerns because of the unilateral nature of the problem. TADs give the practitioner the

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ability to apply forces to a specific area of the mouth to address the asymmetry directly, avoiding unwanted reciprocal forces. As clear aligner therapy is becoming more

common in private practice, the use of TADs for treating asymmetrical problems is an important option to have available.

R ­ eferences 1 Park YC, Lee SY, Kim DH, Jee SH. Intrusion of posterior teeth using mini-screw implants. Am J Orthod Dentofacial Orthop. 2003;123:690–694. 2 Bowman SJ. Thinking outside the box with miniscrews in microimplants as temporary anchorage in orthodontics. Craniofacial Growth Series 2008;45:327–390. 3 Lin JCY, Liou EJW, Yeh CL. Intrusion of over-erupted maxillary molars with miniscrew anchorage. J Clin Orthod. 2006;40:378–383. 4 Lin JCY, Yeh CL, Liou EJW, Bowman SJ. Treatment of skeletal-origin gummy smiles with miniscrew anchorage. J Clin Orthod. 2008;42:285–296. 5 Papadopoulos MA, Papageorgiou SN, Zogakis IP. Clinical effectiveness of orthodontic miniscrew implants: a meta-analysis. J Dent Res. 2011;90:969–976. 6 Hakami Z. Molar intrusion techniques in orthodontics: a review. J Int Oral Health 2016;6. 8:302–306. 7 Kravitz ND, Kusnoto B, Tsay P, Hohlt WF. The use of temporary anchorage devices for molar intrusion. J Am Dent Assoc. 2007;138:56–64. 8 Boyd RL. Complex orthodontic treatment using a new protocol for the invisalign appliance. J Clin Orthod. 2007;41:525–547.

  9 Park YC, Chu JH, Jo YM, Lee KJ. Extraction space closure with vacuum-formed splints and miniscrew anchorage. J Clin Orthod. 2005;39:76–79. 10 Paquette D. Temporary anchorage devices in combination with aligners. www.aligntechinstitute.com. November 2009. 11 Giancotti A, Germano F, Muzzi F, Greco M. A miniscrewsupported intrusion auxiliary for open-bite treatment with Invisalign. J Clin Orthod. 2014;48:348–358. 12 Sparaga J. Invisalign and TADs. Ortho Products 2009;16:18–21. 13 Ludwig B, Baumgaertels S, Bowman SJ. Mini-Implants in Orthodontics: Innovative Anchorage Concepts. Chicago, IL: Quintessence Publishing, 2008. 14 Bowman SJ, Celenza F, Sparaga J, et al. Creative adjuncts for clear aligners, part 2 intrusion, rotation and extrusion. J Clin Orthod. 2015;49:162–172. 15 Carano A, Velo S, Leone P, Siciliani G. Clinical applications of the miniscrew anchorage system. J Clin Orthod. 2005;39:9–24. 16 Guarneri MP, Oliverio T, Silvestre I, et al. Open bite treatment using clear aligners. Angle Orthod. 2013;83:913–919.

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53 Microimplant-assisted Aligner Therapy Ramon Mompell1,2 and S. Jay Bowman3,4,5 1

Division of Growth and Development Section of Orthodontics, School of Dentistry, Center for Health Science, University of California Los Angeles, Los Angeles, CA, USA Private Practice, Madrid, Spain 3 Department of Orthodontics, Center for Advanced Dental Education, St. Louis University, St. Louis, MO, USA 4 Department of Orthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI, USA 5 Private Practice, Portage, MI, USA 2

53.1 ­Improving Clear Aligner Predictability with Microimplants Since the introduction of the use of a series of clear aligners to move teeth in 1999, their use and the number of different applications have grown dramatically. Initial steps with aligners were sometimes problematic and early adopters quickly became aware of limitations and a lack of consistent predictability [1–11], but they persistently pursued improvements and innovations. The popularity of “clear” orthodontics has driven advancements, many based on  adjuncts such as enhancements with microimplant anchorage, thereby improving the predictability of aligners [12–26]. This chapter discusses a variety of aligner treatment mechanics assisted by skeletal anchorage.

53.2 ­Transverse Corrections and Airway Considerations Traditionally, rapid palatal expanders (RPE) have been used to correct maxillary transverse deficiency in growing patients. However, conventional RPE appliances have undesirable side effects, such as limited skeletal movement, dentoalveolar tipping, root resorption, detrimental periodontal consequences, and a lack of long-term stability [27]. To moderate these effects, clinicians in recent years developed the miniscrew-supported hybrid hyrax [28] and microimplant-assisted rapid palatal expander (MARPE) [29]. The maxillary skeletal expander (MSE) is a particular type of MARPE appliance that differs from the others because it promotes application of more posterior and superior force application. The MSE uses bicortical engagement of four

microimplants, inserted into the cortical bone of the palate and nasal floor between the maxillary molars, medial to the zygomatic buttress bones, thus enabling more parallel split of the midpalatal suture. This unique configuration allows the MSE to achieve skeletal expansion, not only in growing patients, but potentially in non-growing patients [30]. This concept is a possible alternative to surgically assisted rapid palatal expansion (SARPE), which has been considered the treatment of choice for adult patients requiring expansion. It should be noted that the effects of the MSE are also exhibited within the entire midface, not just the lower third of the maxillary bone as found with an RPE. Due to this midfacial expansion, airway improvement may also be achieved [31]. Perhaps some caution may be warranted with MSE expansion as there could be some potential side effects such as fractures at the vomer, increased nasal base width, sinus infections, etc. A meta-analysis comparing benefits of bone-borne expansion vs. tooth-borne concluded that there was limited evidence of (i) increased sutural opening; (ii) reduced tooth tipping; and (iii) lower nasal airway resistance [32]. However, limitations of the trials included in that systematic review (i.e. moderate evidence quality, limited sample sizes, potential biases) “preclude drawing definite conclusions.” Subsequently, the following advice was offered in the 2019 American Association of Orthodontists “White Paper” on obstructive sleep apnea (OSA) and orthodontics [33]: There is growing evidence, although of low level, that in mixed dentition patients who are properly diagnosed with OSA, rapid maxillary expansion can decrease the apnea–hypopnea index (AHI) in the short and long-term [34]. Unfortunately, untreated

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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control groups generally were not used in the studies considered. Regardless of the presence of OSA, it is recommended the orthodontist use these devices only when there is an appropriate underlying skeletal condition. There is no indication in the literature that prophylactic application of maxillary expansion prevents the future development of OSA. Questions remain if early use of MSE is warranted and will provide any differing results.

53.2.1  MSE in Combination with Aligners Although rapid palatal expansion can be performed before aligner therapy as a separate first-phase treatment, simultaneous use of MSE during aligner treatment might produce several positive effects for not only growing patients, but also in adults (Figure  53.1). In adolescent and adult patients, this combination of therapies permits the clinician to perform the orthopedic phase of treatment simultaneously with orthodontic tooth movement [35], effectively shortening the total treatment time. During expansion, maxillary teeth may be moved with favorable control while minimizing undesired dentoalveolar effects, and mandibular dental movements such as decompensation can also be carried out simultaneously. Patient motivation and compliance may also be significantly improved in this scenario as the diastema that develops immediately following effective expansion might be reduced more quickly. In addition, protraction of the maxilla may possibly be performed, if indicated, in combination with alignment of teeth with aligners and MSE due to the disarticulation of the midpalatal and pterygopalatine sutures [36]. This protraction of the maxilla, along with the expansion of the nasal cavity, may potentially improve the airway as well. Another interesting type of MSE that may have more favorable simultaneous application with aligners for adolescent patients is the Brolex; it features no plastic on the palate or bands on the teeth to interfere with seating of aligners (Figure 53.2) [37].

53.3 ­Sagittal Corrections Patients with a Class II malocclusion might be treated either by distalization of the maxillary arch or mesialization or “advancement” of the mandibular arch. If, on the other hand, a patient presents a dental Class III malocclusion with no skeletal implications, either distalization of the mandibular arch or mesialization of the maxillary dental arch are options. In situations of Class I bimaxillary protrusion, extraction or total arch distalization of both arches may be considered.

Achieving skeletal and dental Class I are often primary orthodontic treatment goals. However, they are not always achievable due to common limitations, including lack of remaining growth, limits of poor compliance, and unhealthy gingival conditions. It may be that microimplants combined with aligner therapy could be a viable alternative to conventional treatments using fixed appliances and complex orthopedic devices for some situations, although the spectrum of cooperation issues still exists with aligners. Specific dental movements in an anteroposterior plane are also possibilities for sagittal correction. Therefore, a Class I molar and/or buccal segment correction might be obtained by some mechanism designed specifically for maxillary “distalization” prior to or during the aligner treatment (e.g. fixed functional, “distalizer,” Class II elastics). Alternately, total arch distalization of the maxillary arch could also be considered. Any of these options might make use of miniscrews to enhance anchorage support, diminish reliance upon patient compliance, and, thereby, improve the effectiveness and efficiency of the Class II correction [12, 38–40].

53.3.1  Sequential Distalization of the Maxillary Dentition Molar distalization has risen as a popular alternative for the initial stages of Class II malocclusion correction. It is interesting to note that for growing individuals, the Class II correction is primarily derived from interruption of dentoalveolar compensation, not from the task of just moving molars posteriorly. In fact, there is very little difference in the results among any methods chosen for Class II correction (e.g. headgear, elastics, distalizer, fixed functionals, etc.), especially when considering that the difference in the amount of mandibular change is negligible whether the upper or lower arch is the focus [38, 41]. Although some limited amounts of molar distalization have been demonstrated with clear aligners (when supported only with Class II elastics), this implies that only mild corrections are likely [42]. Another option is to support the maxillary buccal segment distalization using an adjunct (e.g. Carriere “distalizer” [43]) as a prelude to aligners. The addition of miniscrew anchorage with an elastic chain, applied from the skeletal anchor unit to this sectional “bar,” provides an additional, more horizontal vector of force for distal movement of the buccal posterior segments (Figures  53.3 and 53.4) [12]. This combination increases the predictability of the mechanism and reduces some of the noted side effects of Class II elastics. Other types of molar distalizers, including the Horseshoe Jet [12, 40], have also been incorporated into pre-treatment

Chapter 53  Microimplant-assisted Aligner Therapy

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Figure 53.1  Maxillary skeletal expansion using MSE combined with aligner therapy. The left column shows the illustrations of skeletal expansion (a, c, e, g); the right column shows the clinical progress (b, d, f, h). (a,b) Before expansion. MSE in place combined with aligners. Aligners need to be cut between the maxillary central incisors to allow the maxillary bone to split through the midpalatal suture. (c, d) Immediately after expansion. Occlusal views right after expansion but before closing the anterior diastema that formed as a result of sutural expansion. (e, f) After retention period. Expansion unit of the MSE can be locked at this point to avoid any relapse. (g, h) After closing the anterior diastema with aligner therapy.

or concurrent molar movement with aligners (Figure 53.5). No matter the method chosen for sectional or molar distalization, it is critical that subsequent “holding the anchorage (teeth that have been moved posteriorly)” is followed to prevent relapse of the gains. This may be as simple as continuing Class I and/or II elastics during “retraction” of the

rest of the maxillary dentition [12]. A series of orthodontic instruments were introduced to specifically facilitate the application of these elastic forces by providing clearance for bonded buttons and to cut elastic hooks into the aligners (Clear Collection, Hu-Friedy, https://www.hu-friedy. com/Clear-collection) (Figure 53.6) [25, 26].

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53.3.2  Total Distalization of Maxillary and/ or Mandibular Dental Arches

Figure 53.2  The Brolex is a small MSE, typically for use with adolescents, supported by two miniscrews (without any supporting molar bands or palatal plastic).

(a)

Total distalization of maxillary or mandibular dental arches might provide a treatment solution for the correction of a Class II and Class III malocclusions, respectively [44], especially if patients decline a surgical approach to resolve their malocclusions. When using aligners, direct anchorage to a microimplant is recommended, perhaps using both intra-alveolar and extra-alveolar microimplants. Depending on whether microimplants are attached directly to notches in the aligner plastic or to hooks bonded to teeth, different effects on the occlusal plane and vertical control can be achieved by controlling the torque of the anterior teeth [45]. In situations of mild Class II, simple direct anchorage from microimplants placed in either the buccal or lingual alveolus between maxillary molars or between first molars and second premolars are used to

(b)

Figure 53.3  Pre-aligner distalization with a miniscrew-supported Carriere distalizer. Adult female patient with unilateral Class II malocclusion. Miniscrew inserted in the maxillary buccal alveolus between second premolar and first molar. Elastomeric chain stretched between the miniscrew and the hook of the distalizer at the canine. A mandibular lingual arch was used to support the Class II elastics to the distalizer as well. Upon completion of posterior movement of the right segment, the fixed appliances were removed and clear aligner treatment was initiated, supported by Class II elastics. (a) Initial. (b) Final. Source: Bowman et al. [12]. Reprinted with permission from the Journal of Clinical Orthodontics.

Chapter 53  Microimplant-assisted Aligner Therapy

Figure 53.4  An adolescent male with a Class II division 2 malocclusion with deep overbite, crowding, and peg-shaped laterals. A Carriere distalizer is applied along with a lower lingual arch. Miniscrews are inserted in the buccal alveolus between first molars and second premolars and elastic chain is stretched from the miniscrew to the hook at the canine on the distalizer. In addition, Class II elastics are also used. Upon production of a “super-Class I” molar relationship, the fixed appliances are removed and clear aligner treatment is initiated. Class I intramaxillary and Class II intermaxillary elastics are used to support retraction of remaining teeth. Some anterior bite opening remains to be resolved in refinement.

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Figure 53.5  (a, b) Horseshoe jet maxillary molar distalization supported by miniscrews inserted into the palatal alveolus between first molars and second premolars. (c, d) Upon completion of molar distal movement, the appliance was removed and clear aligner treatment was initiated. Class II elastics were attached to the aligners for support of the subsequent retraction of the remaining maxillary teeth. Source: Bowman et al. [12]. Reprinted with permission from the Journal of Clinical Orthodontics.

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Figure 53.6  Clear Collection instruments designed to enhance clear aligner treatments. Pictured are the hole punch pliers used to cut half-moon shape at the edge of aligners to provide relief for buttons bonded on teeth for the application of elastics [25, 26]. Source: Courtesy of Hu-Friedy Manufacturing Co., Chicago.

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Figure 53.7  Class II correction with clear aligners, supported by miniscrew anchorage and elastics. Adult female with Class II malocclusion with deep overbite and crowding. Two miniscrews were inserted between the maxillary second premolars and first molars and used to support “Class I” horizontal elastics combined with Class II elastics. Resolution of the Class II relationship was achieved. (a) Initial. (b) Final.

s­ upport Class I horizontal intramaxillary elastics applied to hooks cut in the aligners mesial to canines or to bonded buttons or “power arms” (Figures 53.7 and 53.8). In these situations, occlusal plane modifications could occur as the center of resistance of the full arch is apical to the applied force vector. For this reason, these locations may not be indicated for distalization of the segments alone [46].

53.3.3  Protraction of Maxillary and/or Mandibular Posterior Teeth In cases where protraction of posterior teeth is needed, while maintaining the anterior anchorage, microimplants can be used on the mesial half of the space between the roots of the teeth, adjacent to the space to be closed. This

Chapter 53  Microimplant-assisted Aligner Therapy

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Figure 53.8  Class II unilateral distalization with aligners supported by miniscrew anchorage. (a) Adult male with anterior crowding and Class II dental relationship on left side. (b) Miniscrew inserted between the maxillary first and second molars with a closed coil retraction spring stretched from the miniscrew to a “power arm” bonded on the lingual of the maxillary first premolar, which later was replaced with a bonded aligner hook on the canine. (c) Class I correction and resolution of crowding was achieved in 18 months. Source: Bowman et al. [12]. Reprinted with permission from the Journal of Clinical Orthodontics.

Figure 53.9  Protraction of maxillary posterior teeth. In this case, microimplants should be positioned as close as possible to canines to allow maximum mesial movement of the posterior segments. Determination of the center of rotation becomes very important in order to avoid other side effects and increase in treatment time. Long-arm hooks were bonded on maxillary first molars and covered by attachments.

type of microimplant application can also be used in conjunction with the aligner therapy when maximum protraction of posterior teeth or improved efficiency of such movement is anticipated (Figure 53.9). Careful consideration for the direction of the force vector in relation to the

center of rotation is essential in this type of microimplant application. In Figure 53.9, note that “hooks” were bonded to the first molars, embedded into the “aligner attachments,” to facilitate mesial movement of posterior teeth while using clear aligner trays on both maxillary and

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­ andibular arches. Elastic chains were then stretched m from these hooks to the microimplants that were placed at the edentulous site, slightly distal to the maxillary canines. In this case, long-arm or “power arm” hooks were used to direct force vectors to pass through centers of resistance, allowing bodily movement of premolars and molars while minimizing unfavorable tipping or vertical movements.

53.4 ­Vertical Correction

53.3.4  Retraction of Maxillary and/or Mandibular Anterior Teeth

53.4.1  Open Bite

There has been an increase in the popularity of microimplants for efficient retraction of anterior segments for both mandibular and maxillary arches in both non-extraction and extraction scenarios with clear aligners [14, 47–49]. Aligner therapy, along with well-designed use of microimplants, allows clinicians to retract six anterior teeth simultaneously, free from concern about loss of posterior anchorage (just as in the fixed appliance therapy). Depending on the location of the microimplants and the length of the hooks, different effects in the anterior teeth can be generated. By using these mechanisms, torque control of the anterior teeth can be managed satisfactorily while correcting deep bites or anterior open bites [14]. Another option involves the addition of a modified TPA (Figure  53.10) that permits the application of elastic chains to palatal miniscrews [40]. As a result, the TPA enhances anchorage support during the retraction of the maxillary dentition after extraction and/or reinforces typical Class II mechanics.

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In order to apply the proper mechanics to improve vertical issues, it is very important to analyze the origin of the vertical problem. Depending on the cause(s) of the vertical problem, anterior open bite and deep bite malocclusions can be resolved either by anterior or posterior intrusion and/or extrusion.

For patients who have intruded incisors or inadequate incisor display, extrusion of anterior teeth may be planned (Figure  53.11a) [15]. One simple method to achieve this objective is to place microimplants in the interradicular spaces between laterals and canines of the opposite arch and to have the patient wear elastics from buttons bonded on the buccal surfaces of canines to those microimplants (Figure 53.11b). When the open bite is caused by maxillary vertical excess or hyper-erupted posterior teeth, aligners can be used in conjunction with elastics that are stretched over the aligners from buccal and palatal microimplants, placed between the posterior teeth (Figures 53.12 and 53.13) [13].

53.4.2  Anterior Intrusion (Deep Bite) In cases of deep bite with a “gummy smile,” but a favorable lower facial third, intrusion of maxillary incisors will eliminate the deep overbite and create an improved smile ­display [50]. Altered passive eruption, short upper lip, and hypermobility of upper lip need to be considered when

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Figure 53.10  TPA−. (a) The TPA− is a modification of the transpalatal arch concept designed for anchorage to support both nonextraction and extraction Class II malocclusions. Miniscrews are inserted in the palatal alveolus between the maxillary first molars and second premolars (QC Orthodontics Lab, Inc., Fuqua-Varina, NC, USA). The TPA- permits the application of elastic chain from hooks on the framework in the anterior palate to the miniscrews to provide distally directed force to the molars. A second hook at the mesial of the first molar also allows for the addition of elastic chain to create intrusive forces from the same miniscrews for simultaneous vertical control. (b) A similar type of TPA− can be used for extraction situations to provide (continuous force) anchorage support to molars and/or for some simultaneous molar distal movement. No patient compliance is required, forces are applied close to the center of resistance of the molars, and the appliance can be used with braces and/or aligners (it may be fabricated to bond to molars instead of molar bands). Source: Bowman [40]. Reprinted with permission from Elsevier.

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Figure 53.11  (a) Adult female with a Class III relationship, inadequate maxillary incisor display, anterior crossbite, and anterior open bite. Maxillary anterior extrusion was planned using clear aligners, bonded buttons at the gingival of the incisors, and a miniscrew inserted at the midline of the symphysis. An elastic was connected from the buttons to the miniscrew with the aligners acting as an eruption guide. After one year, a positive overjet/overbite were created along with spaces for final esthetic restoration of the upper anterior teeth. Source: Lin et al. [15]. Reprinted with permission from the Journal of Clinical Orthodontics. (b) Elastics can also be worn bilaterally from microimplants in the interradicular spaces between mandibular laterals and canines to buttons bonded on the labial surfaces of maxillary canines.

c­ reating a treatment plan for deep bite resolution. Figure 53.14 shows an example of how deep bite was corrected with anterior microimplants and aligners.

53.5 ­Orthopedic Treatment with Aligners and Mini-implants 53.5.1  Maxillary Anterior Protraction in Young and Adult Patients If the patient presents a skeletal Class III malocclusion due to retrognathic maxilla, protraction may be considered. These patients often present a sagittal discrepancy in combination with a transverse deficiency. Therefore, a combination of MSE and facemask is an option to be considered. If patients need heavier forces (e.g. adult patients, or those who refuse to wear a facemask), Class III elastics could be used with aligners by placing two miniplates in the mandibular anterior area (Figure  53.15) [51]. Vectors of the

applied forces should be analyzed in detail prior to initiating this type of mechanics. Correction with this type of mechanism is more likely to occur when the pterygoid plates are disarticulated, at least in the lower two thirds of their connection with the vertical process of the palatine bone. This disarticulation may be achieved by following a proper expansion procedure [52]. Another option for mild Class IIIs is the introduction of adjunctive appliances such as the TPA+, a modification of the standard TPA designed to use elastic chains to produce anteriorly directed forces on the maxillary dentition (Figure  53.16) [40]. This miniscrew-supported appliance directs forces close to the center of resistance of the molars. It is a simple mechanism that can be used with molar bands or bonded to the lingual of the molars and may be employed during aligner treatment to augment the Class III elastics. Intrusive forces can also be added for vertical control by adding elastic chains from hooks located between the first molars and second premolars, apically to the miniscrews.

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Figure 53.12  Posterior intrusion for anterior open bite correction. (a) Illustration of intrusion of maxillary posterior teeth using three microimplants on each side for correction of an open bite. (b) An adult female with a significant anterior open bite was treated with a combination of clear aligners and miniscrew-supported elastics. Two miniscrews were inserted in the palatal alveolus between the molars and two also inserted in the buccal alveolus between the same molars. An elastic was stretched from one miniscrew to the other, over the aligner in a “sling” or “bootstrap” arrangement. Two miniscrews were also inserted in the mandibular buccal alveolus between the second premolars and first molars. Elastics were then stretched from buttons bonded on the lingual of the mandibular first molars, over the aligners, down to the mandibular miniscrews. The elastics provided support for clear aligner-directed posterior intrusion. Once the anterior open bite was resolved, then intermaxillary elastics were added from bonded buttons to improve the posterior occlusion, guided by the aligners.

53.5.2  Mandibular Advancement in Growing Patients Any functional appliance for correction of skeletal Class II may produce some retraction of maxillary incisors, distalization of maxillary molars, but may also induce untoward proclination of mandibular anterior teeth. Two microimplants in the mandible and two microimplants in the maxilla could

be placed to help avoid unwanted dental effects during functional protraction treatment using aligners. For example, mandibular microimplants may be located distal to first or second premolars and connected by stainless steel ligatures to buttons bonded on canines. Another option is to use Class  I intramandibular horizontal elastics stretched from the miniscrews to notches or hooks cut into the aligners

Chapter 53  Microimplant-assisted Aligner Therapy

(a)

(b)

(c)

Figure 53.13  Posterior intrusion for an anterior open bite. An adolescent male with a narrow maxillary arch, anterior open bite, and crowding was treated using a combination of clear aligners and miniscrews. “Sling” or “bootstrap” elastics were extended from miniscrews inserted in both the buccal and lingual maxillary alveolus across the clear aligners. As intrusion of the posterior teeth was achieved, then bonded buttons were added for intermaxillary elastics to seat the posterior occlusion as directed by the aligners. (a) Pre-treatment; (b) progress; (c) post-treatment.

mesial to the mandibular canines. These options may prevent the adverse flaring of the mandibular anterior segment that accompanies functional appliances (Figure 53.17) [53].

53.6 ­Conclusion Aligner therapy, enhanced with microimplants, permits complex orthodontic and orthopedic problems to be

treated successfully while also potentially reducing treatment times that aligner therapy alone requires. Therefore, the addition of microimplants and associated microimplant-supported devices has expanded the scope of applications for clear aligners, while also improving their predictability. However, specific considerations related to biomechanics certainly need to be carefully analyzed when microimplants are selected for combination with aligners.

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Figure 53.14  Anterior intrusion (deep bite). Modified intrusion using two microimplants. These biomechanics are used when only one or two teeth need to be intruded.

(a)

(b)

(c)

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(e)

Figure 53.15  Maxillary anterior protraction in young and adult patients. (a) Before treatment of the combination of MSE with aligners and miniplates. (b) After treatment. (c–e) Intraoral photographs showing hooks for anterior protraction with facemask and miniplates.

(a)

(b)

Figure 53.16  TPA+. (a) The TPA+ is a modification of the transpalatal arch concept designed for anchorage to support both nonextraction and extraction mild Class III malocclusions. Miniscrews are inserted in the palatal alveolus between the maxillary first molars and second premolars (QC Orthodontics Lab, Inc.). The framework of the TPA+ allows for the application of elastic chain from hooks posterior to the molars forward to the miniscrews to produce anteriorly directed force to the maxillary dentition. (b) A second hook at the mesial of the first molars also allows for the addition of elastic chain to create intrusive forces from the same miniscrews for simultaneous vertical control. No patient compliance is required, forces are applied close to the center of resistance of the molars, and the appliance can be used with braces and/or aligners (it may be fabricated to bond to molars instead of molar bands.). Source: Bowman [40]. Reprinted with permission from Elsevier.

Chapter 53  Microimplant-assisted Aligner Therapy

(a)

(b)

(c)

Figure 53.17  Reducing the side effects of labial tipping of mandibular incisors during treatment to promote “mandibular advancement” in growing patients. (a) Skeletal Class II before treatment with two miniscrews connected by elastics to the aligner in the anterior portion of the clear aligners. (b) “Twin block” style plastic wings molded as part of the aligners designed for mandibular advancement and promoting an intended overcorrection of the Class II. (c) At the end of treatment.

­References 1 Javidi H, Graham E. Clear aligners for orthodontic treatment? Evid Based Dent. 2015;16:111. 2 Clements KM, Bollen AM, Huang G, et al. Activation time and material stiffness of sequential removable orthodontic appliances. Part 2: dental improvements. Am J Orthod Dentofacial Orthop. 2003;124:502–508. 3 Djeu G, Shelton C, Maganzini A. Outcome assessment of Invisalign and traditional orthodontic treatment compared with the American Board of Orthodontics objective grading system. Am J Orthod Dentofacial Orthop. 2005;128:292–298. 4 Phan X, Ling PH. Clinical limitations of Invisalign. J Can Dent Assoc. 2007;73:263–266. 5 Tuncay O. The Invisalign System. London: Quintessence Publishing, 2007. 6 Rossini G, Parrini S, Castroflorio T, et al. Efficacy of clear aligners in controlling orthodontic tooth movement: a systematic review. Angle Orthod. 2015;85:881–889. 7 Lagravère MO, Flores-Mir C. The treatment effects of Invisalign orthodontic aligners: a systematic review. J Am Dent Assoc. 2005;136:1724–1729. 8 Buschang PH, Ross M, Shaw SG, et al. Predicted and actual end-of-treatment occlusion produced with aligner therapy. Angle Orthod. 2015;85:723–727. 9 Kravitz ND, Kusnoto B, Begole E, et al. How well does Invisalign work? A prospective clinical study evaluating the efficacy of tooth movement with Invisalign. Am J Orthod Dentofacial Orthop. 2009;135:27–35. 10 Krieger E, Seiferth J, Marinello I, et al. Invisalign® treatment in the anterior region: were the predicted tooth movements achieved? J Orofac Orthop. 2012;73:365–376. 11 Chisari JR, McGorray SP, Nair M, Wheeler TT. Variables affecting orthodontic tooth movement with clear aligners. Am J Orthod Dentofacial Orthop. 2014; 145:S82–91. 12 Bowman SJ, Celenza F, Sparaga J, et al. Creative adjuncts for clear aligners. Part 1: Class II treatments. J Clin Orthod. 2015;49:83–94.

13 Bowman SJ, Celenza F, Sparaga J, et al. Creative adjuncts for clear aligners. Part 2: intrusion, rotation, and extrusion. J Clin Orthod. 2015;49:162–174. 14 Bowman SJ, Celenza F, Sparaga J, et al. Creative adjuncts for clear aligners. Part 3: extraction and interdisciplinary treatment. J Clin Orthod. 2015;49:249–262. 15 Lin JC, Tsai SJ, Liou EJ, Bowman SJ. Treatment of challenging malocclusions with Invisalign and miniscrew anchorage. J Clin Orthod. 2014;48:23–36. 16 Giancotti A, Germano F, Muzzi F. Greco M. A miniscrewsupported intrusion auxiliary for open-bite treatment with Invisalign. J Clin Orthod. 2014;48:348–358. 17 Ludwig B, Baumgaertel S, Bowman SJ. Mini-Implants in Orthodontics: Innovative Anchorage Concepts. London: Quintessence Publishing, 2008. 18 Simon M, Keilig L, Schwarze J, et al. Forces and moments generated by removable thermoplastic aligners: incisor torque, premolar derotation, and molar distalization. Am J Orthod Dentofacial Orthop. 2014;145:728–736. 19 Duong T, Kuo E. Finishing with invisalign. Prog Orthod. 2006;7:44–55. 20 Bollen AM, Huang G, King G, et al. Activation time and material stiffness of sequential removable orthodontic appliances. Part 1: ability to complete treatment. Am J Orthod Dentofacial Orthop. 2003;124:496–501. 21 Kamatovic M. A retrospective evaluation of the effectiveness of the Invisalign appliance using the PAR and irregularity indices. Dissertation, University of Toronto, Ontario, 2004. 22 Gomez JP, Peña FM, Martínez V, et al. Initial force systems during bodily tooth movement with plastic aligners and composite attachments: a three-dimensional finite element analysis. Angle Orthod. 2015;85:454–460. 23 Dasy H, Dasy A, Asatrian G, et al. Effects of variable attachment shapes and aligner material on aligner retention. Angle Orthod. 2015;85:934–940.

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2 4 Bowman SJ. Improving the predictability of clear aligners. Semin Orthod. 2017;23:65–75. 25 Bowman SJ. Clear Collection instruments for clear aligner treatments. Part I. Orthod Practice US. 2015;6:74–78. 26 Bowman SJ. Clear Collection instruments for clear aligner treatments. Part 2. Orthod Practice US. 2015;6:48–52. 27 Gurel HG, Memili B, Erkan M, Sukurica Y. Long-term effects of rapid maxillary expansion followed by fixed appliances. Angle Orthod. 2010;80:5–9. 28 Ludwig B, Glasl B, Bowman SJ, et al. Miniscrewsupported Class III treatment with the hybrid RPE advancer. J Clin Orthod. 2010;44:1–7. 29 Lagravère M, Carey J, Heo G, et al. Transverse, vertical, and anteroposterior changes from bone-anchored maxillary expansion vs traditional rapid maxillary expansion: a randomized clinical trial. Am J Orthod Dentofacial Orthop. 2010;137:304–312. 30 Carlson C, Sung J, McComb RW, et al. Microimplantassisted rapid palatal expansion appliance to orthopedically correct transverse maxillary deficiency in an adult. Am J Orthod Dentofacial Orthop. 2016;149:716–728. 31 MacGinnis M, Chu H, Youssef G, et al. The effects of micro-implant assisted rapid palatal expansion (MARPE) on the nasomaxillary complex:a finite element method (FEM) analysis. Prog Orthod. 2014;15:52. 32 Krüsi M, Eliades T, Papageorgiou S. Are there benefits from using bone-borne maxillary expansion instead of tooth-borne maxillary expansion? A systematic review with meta-analysis. Prog Orthod. 2019;20:9. 33 American Association of Orthodontists White Paper: Obstructive Sleep Apnea and Orthodontics. https://www. neso.org/wp-content/uploads/2019/03/ACallahan-AOWhite-Paper-Obstructive-Sleep-Apnea-and-OrthodonticsFinal-with-Appendixes.pdf (accessed 1 April 2019). 34 Pirelli P, Saponara M, Guilleminault C. Rapid maxillary expansion (RME) for pediatric obstructive sleep apnea: a 12-year follow-up. Sleep Med. 2015;16:933–35. 35 Cantarella D, Dominguez-Mompell R, Moschik C, et al. Midfacial changes in the coronal plane induced by microimplant-supported skeletal expander, studied with cone-beam computed tomography images. Am J Orthod Dentofacial Orthop. 2018;154:337–345. 36 Cantarella D, Dominguez-Mompell R, Mallya SM, et al. Changes in the midpalatal and pterygopalatine sutures induced by micro-implant-supported skeletal expander, analyzed with a novel 3D method based on CBCT imaging. Prog Orthod. 2017;18:34. 37 Di Leonardo B, Ludwig B, Glasl B, et al. BRÖLEX – Eine rein knochengetragene Expansionsapparatur Vorstellung und erste klinische Erfahrungen. TECHNOBYTES. Kieferorthopädie 2016;30:149–152.

38 Bowman SJ. Settling the score with Class IIs using miniscrews. In: Kim KB, ed. Temporary Skeletal Anchorage Devices – A Guide to Design and EvidenceBased Solutions. Berlin: Springer, 2014, pp. 57–69. 39 Bowman SJ. The horseshoe jet for miniscrew-supported molar distalization. J Clin Orthod. 2018;51:196–218. 40 Bowman SJ. Uno, dos, tres: one concept for three Angle Classes. Semin Orthod. 2018;24:3–16. 41 Tsourakis AK, Johnston LE Jr. Class II malocclusion: the aftermath of a “perfect storm.” Semin Orthod. 2014;20:59–73. 42 Klein BM. A cephalometric study of adult mild Class II nonextraction treatment with the Invisalign System. Master’s thesis, Center for Advanced Dental Education, St. Louis University, St. Louis, MO, 2013. 43 Sandifer CL, English JD, Colville CD, et al. Treatment effects of the Carrière distalizer using lingual arch and full fixed appliances. J World Fed Orthod. 2014;3:e49–e54. 44 Sung SJ, Jang GW, Chun YS, Moon YS. Effective en-masse retraction design with orthodontic mini-implant anchorage: a finite element analysis. Am J Orthod Dentofacial Orthop. 2010;137:648–657. 45 Thakkar S, Puri N, Singh H. Long-term stability of maxillary group distalization with interradicular miniscrews. Am J Orthod Dentofacial Orthop. 2016;150:558–559. 46 Choi NC, Park YC, Jo YM, Lee KJ. Combined use of miniscrews and clear appliances for the treatment of bialveolar protrusion without conventional brackets. Am J Orthod Dentofacial Orthop. 2009;135:671–681. 47 Park YC, Chu JH, Choi YJ, Choi NC. Extraction space closure with vacuum-formed splints and miniscrew anchorage. J Clin Orthod. 2005;39:76–79. 48 Li W, Wang S, Zhang Y. The effectiveness of the Invisalign appliance in extraction cases using the the ABO model grading system: a multicenter randomized controlled trial. Int J Clin Exp Med. 2015;8:8276–8282. 49 Baldwin DK, King G, Ramsay DS, et al. Activation time and material stiffness of sequential removable orthodontic appliances. Part 3: premolar extraction patients. Am J Orthod Dentofacial Orthop. 2008;133:837–845. 50 Lin JC, Chen S, Liou EJW, et al. Interdisciplinary aligner treatment of short-face patients, J Clin Orthod. 2017;51:382–405. 51 De Clerck H, Cevidanes L, Baccetti T. Dentofacial effects of bone-anchored maxillary protraction: a controlled study of consecutively treated Class III patients. Am J Orthod Dentofacial Orthop. 2010;138:577–581. 52 Cantarella D, Dominguez-Mompell R, Moschik C, et al. Zygomaticomaxillary modifications in the horizontal plane induced by micro-implant-supported skeletal expander, analyzed with CBCT images. Prog Orthod. 2018;19:41. 53 Luzi C, Luzi V, Melsen B. Mini-implants and the efficiency of Herbst treatment: a preliminary study. Prog Orthod. 2013;14:21.

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54 Safe and Precise TAD Placement in the Anterior Palate with Simple and Inexpensive TAD Guides Philipp Eigenwillig1, Björn Ludwig2, and Axel Bumann3,4 1

Private Practice, Brandenburg an der Havel, Germany Private Practice, Traben Trarbach, Germany 3 Department of Orthodontics, Christian-Albrechts-University, Kiel, Germany 4 Private Practice, Berlin, Germany 2

54.1 ­Introduction Skeletal anchorage via temporary anchorage devices (TADs) is a fast growing technique used in orthodontic treatment. According to Newton’s third law, in every interaction between two teeth, there is always a pair of forces. To avoid unwanted side effects during treatment, the orthodontist has to take these forces and anchorage into account [1]. A benefit of TADs is that they provide absolute anchorage and do not require patient compliance. According to Kanomi [2], TADs are a minimally invasive treatment option and they offer a wide spectrum of usability. There are many different TAD-supported devices for specific orthodontic treatment goals, such as mesialization [3], distalization [4, 5], and transversal expansion and intrusion. Alveolar bone has been frequently used for TAD placement; however the anterior palate is also a suitable region [6, 7]. The bone density in the anterior palate provides a good condition for primary stability of the orthodontic miniscrew. There is enough bone height with an appropriate mucosa condition [8–10]. Miniscrews are either placed directly into the midpalatal suture or parasutural area at the level of the third ruga [8]. This region is considered safe due to the absence of dental roots. However, the bone height can vary between patients [11, 12], so evaluation of the bone height using cone-beam computed tomography (CBCT) is recommended for precise placement of miniscrews [13]. Because of the amount of radiation emitted during scanning, a CBCT scan should not be considered as standard diagnosis protocol [14]. Rather, a 2D panoramic and a lateral cephalometric radiograph are standard protocol. A 2D lateral cephalogram contains superimposed information of 3D landmarks of real skeletal structures and allows reliable

analysis in the sagittal and vertical dimensions. However, there are certain limitations in the transverse dimension. Kim et al. [15] showed similar bone height in the parasutural region (5 mm) to the midsagittal suture using a lateral cephalogram and a CBCT scan. An intraoral scan and a lateral cephalogram can therefore be used to create a combined model for planning miniscrew placement either into the midpalatal suture or parasutural.

54.2 ­Virtual TAD Placement with TADmatch™ The diagnostic Onyx Ceph3™ Software (Image Instruments, Chemnitz, Germany) with the module extension TADmatch™ offers all the tools to combine 2D images and 3D models to create a fusion model. The TADs can be placed virtually into the anterior palate. Their position and insertion depth can be reviewed and, if necessary, the TADs can be repositioned. After virtual TAD placement, two different models are made. The first model is for creating an insertion guide while the second model allows an orthodontic appliance to be manufactured. With this protocol, clinicians are able to insert the TADs and place an appliance in a single visit for the patient.

54.3  ­Registration of 2D Lateral Cephalographs and 3D Models The correct registration of different 2D and 3D objects is the starting point for TAD placement planning. In order to create the fusion model, it is necessary to use the “Register 3D” module. The virtual 3D model of the upper and lower

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jaws is loaded into this module. Although a digitized plaster model could be used, an intraoral 3D scan is more accurate since intraoral scans are completely contactless while scanning, so there is no compression of soft tissue. The actual size of the 3D model is defined by the calibration protocol of the 3D scanner. The Register 3D module has four viewports: frontal, lateral, upper jaw, and lower jaw. Subsequently, the lateral cephalometric radiograph is loaded into this module. Because of the difference in magnification from various x-ray machines, the lateral cephalogram must be calibrated by using the nose tip ruler and user-preferred standard measurements. The lateral cephalogram is positioned with the center of the image at the y–z-axis of the coordinate system of the 3D model. Normally, it is adjusted at the midsagittal plane of the palate, but if necessary, it is possible to correct the adjustment afterwards. In order to register both objects correctly, corresponding landmark points have to be selected on each object. It is recommended that points with the greatest possible distance between each other be used to avoid geometrical errors. The incisor point and the posterior point of the occlusal plane, either the mesiolingual cusp of the maxillary first or second molar if fully erupted, are typically used for this procedure. The generated fusion model contains 2D and 3D data, therefore mapping of the corresponding points must take effect on the sagittal plane or the y–z-axis. After initial mapping, the clinician should review the results and can correct the positioning of the cephalogram

using the 3D navigator if necessary. It is possible to add cutting planes in all three dimensions to get a better view on the generated fusion model. At this point, it is possible to correct the midline, the overlapping of the lateral cephalogram, and the midpalatal suture if necessary (Figure 54.1).

54.4  ­Registration of CBCT Scans If a CBCT or CT scan of the patient is available, the clinician has the opportunity to register them with their intraoral surface scan or the lateral cephalogram. The Digital Imaging and Communications in Medicine (DICOM) dataset has to be converted into a surface rendering model prior to adding it to the object list. To create a surface rendering of a CBCT scan, it is necessary to define the threshold for hard tissue or the rendering will not represent real conditions at the implant side. After adding CBCT surface rendering, the clinician should define corresponding surface points between the intraoral scan and CBCT scan. In order to receive better registration results, it is recommended to define as many corresponding surface points as possible. The software calculates the fusion model using a best-match algorithm. The result is a 3D model containing soft tissue and hard tissue surfaces. The clinician can evaluate thickness of the soft tissue and the bone height at the preferred location prior to TAD placement. This new combined model can be saved in the patient’s records (Figure 54.2).

Figure 54.1  Register 3D module matching intraoral scan and lateral cephalogram.

Chapter 54  Safe and Precise TAD Placement in the Anterior Palate

Figure 54.2  Combined model of intraoral scan, CBCT scan, and lateral cephalogram.

54.5  ­Workflow with TADmatch Module The newly created fusion model is loaded into the TADmatch module. This module contains the same four viewports as the Register 3D module. For TAD placement, a single lateral view of the maxilla has turned out to be very effective during placement and reviewing. The clinician can choose from a library of various TADs for treatment planning. Since this software is an open system, it includes miniscrews from various manufacturers such as Ortholox System (Promedia, Germany), Benefit System (PSM, Germany), Ortho Easy (Forestadent, Germany), and tomas® System (Dentaurum, Germany). Depending on the treatment plan and the type of appliance, there may be the need for a single miniscrew or pairs of miniscrews. Most appliances require two completely parallel, synchronized miniscrews to avoid problems with the direction of insertion. The miniscrew library contains two miniscrews with separation distances of 6, 8, or 10 mm. The anatomy of the palate and the desired appliance are the main factors used to choose the right pair of miniscrews. The average maxilla has a ­sufficient transversal width to provide enough space for parasutural insertion. Respectively, a pair of miniscrews

with 8 mm distance is the most common configuration for a parasutural TAD-supported distalizing appliance. For a bone-borne rapid maxillary expander, the parasutural inserted miniscrews should be positioned closer to the midpalatal raphe because of the limited space in a narrow maxilla. A good clinical outcome can be achieved with as little as 6 mm between two miniscrews. The mounted abutments on the miniscrews have a good fit when attached to a standard hyrax expansion screw. The abutments can be attached directly to the miniscrew using a pulsed micro arc dental welding or a laser welding unit (Figure 54.3). After choosing the desired TAD or TAD pair, they can be added to the object list. The TADs are immediately visible in the viewport. The pair of parallel TADs are treated as one single object. Therefore, moving the object on all three axes (x, y, and z) is quite intuitive, and each axis can be treated separately using a navigator. The miniscrews are placed according to the guidelines for inserting palatal miniscrews (Figure  54.4) [8]. The endosseous part of the miniscrews should be fully covered by palatal bone. The mucosa thickness in this region is 3–4 mm. Orthodontic miniscrews are inserted transgingival, usually without special preparation, so most palatal miniscrews have a 3–4 mm long neck and shoulder. In addition, when positioning miniscrews, there should be enough space between the implant head and mucosa to avoid pressure on the mucosa from the appliance. As described previously, a safe insertion area is around the third rugae on the line between upper first premolars. When the final position of the miniscrews has been verified, the positioning model for the surgical guide and the laboratory model for the final appliance are made. When performing the positioning model processing, a cylinder is added to the head of the miniscrew along the longitudinal axis. The diameter is exactly the same as the implant neck and shoulder. The result is a virtual positioning model with two cylinders that represent the future miniscrew location. This virtual model can be printed in-house using a 3D printer or can be sent to an external laboratory to produce the model. Based on the authors’ experience, a stereolithography (SLA) or a digital

Figure 54.3  Implant-supported rapid palatal expander at insertion and after one week of treatment.

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Figure 54.4  TADmatch module: virtual implant placement with library of supported mini-implants.

light processing (DLP) printer is better for the positioning model due to higher precision and print resolution than the fused deposition modeling (FDM) printers currently available. However, the accuracy of FDM printers is acceptable with lab models for the appliance (Figure 54.5).

54.6  ­Conventional Surgical Guides There are different ways to fabricate the surgical guide based on the 3D-printed positioning model. The guide normally contains two parts: the splint itself and a metal insert for high accuracy during the drilling process. The

metal insert is a machine-polished and autoclavable drill sleeve. It is placed over the parallel cylinders of the positioning model. The guide can be vacuum-formed using relatively stiff and hard material, such as duran. However, this thermoplastic method for guide production has disadvantages, such as the fact that the guide cannot be autoclaved, and can be only disinfected using chemical agents. A polyvinylsiloxane (PVS) material might be an alternative for producing the guide. The PVS material comes with automix tips; therefore it is user-friendly while processing. The stiffness of the guide is regulated by the amount and thickness of the PVS material. PVS has a short hardening

Chapter 54  Safe and Precise TAD Placement in the Anterior Palate

Figure 54.5  Positioning model and laboratory model: virtual and 3D-printed.

time and then the guide is ready for finishing. The major advantage of this method is the ability to sterilize the guide using a class B autoclave. The flexibility of PVS material works best in clinical situations with severe malocclusion and lots of undercuts due to different tooth positions and angulations. In cases where a hard material is necessary, orthodontic acrylic material is good for creating the splint. An acrylic splint would work great for cases with appliances supported by four miniscrews, such as completely bone-borne rapid palatal expanders.

54.7 ­Three-dimensional Printed Surgical Guides Instead of 3D printing the model and manufacturing the surgical guide with it, it is possible to design the guide within the software and print it directly without using an actual printed model. After final positioning of the mini-implants into the palate, the positioning model is calculated by the software. After adding a virtual drill sleeve object, the virtual model is used to calculate a shell with a specific thickness of 1.5–2 mm on the model surface. The shell is added as a completely separate object. The result is a virtual surgical guide with a placeholder for the metal sleeve for the insertion drill.

The shell can be 3D-printed using a DLP resin printer such as the MoonRay S (Sprintray Inc., Los Angeles, CA, USA) with a special Class I biocompatible high-strength resin designed specifically for the creation of surgical guides. It can be sterilized in a Class B autoclave without compromising its strength. After printing, the guide needs to be fully washed and post-cured following the manufacturer’s instructions to ensure its biocompatibility (Figure 54.6).

54.8  ­Laboratory Model Aside from the positioning model for the surgical guide, there is an option to create a lab model for the orthodontic appliance. Based on the planned miniscrew position, it is necessary to calculate a model with holes for the laboratory miniscrew analogs. Technically, the mesh of the virtual miniscrews is subtracted from the mesh of the upper jaw using a Boolean operation. After 3D printing the lab model, the real laboratory miniscrew analogs have to be inserted and fixed with composite (Figure 54.5). Using this lab model, the technician can manufacture the appliance following the instructions for the specific miniscrew system. Fabricating the appliance prior to the insertion of the miniscrews is possible due to an optimized workflow (Figure 54.7).

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Figure 54.6  Conventional vacuum-formed and PVS material surgical guides. Three-dimensional printed surgical guide using Class I autoclavable biocompatible resin with metal drill sleeve.

54.9 ­Conclusions Surgical guides for insertion of palatal miniscrews offer various advantages for orthodontists. Precisely planned positioning of implants can significantly reduce the risk of implant failure and damaging anatomical structures such as dental roots. The insertion direction of multiple implants can also be synchronized with a surgical guide. This is very important for orthodontic appliances such as rapid palatal expanders, which cannot tolerate any placement discrepancies. Knowing the exact position of the palatal miniscrews allows a miniscrew-supported appliance to be constructed prior to the miniscrew insertion. Thus, the insertion of the miniscrew and incorporation of the appliance can be done in a single patient visit. Since all needed software, tools, and hardware are available, a complete in-house fabrication is possible or the scan data can be sent to an external lab to produce the surgical guide and appliance.

Figure 54.7  Finished appliance on laboratory model.

Chapter 54  Safe and Precise TAD Placement in the Anterior Palate

Case 54.1  An 18-year-old female visited our office because of pain in her temporomandibular joints (TMJs). Initial diagnosis after intraoral inspection was a circular open bite with solitaire contact on the second molars. She showed a slight Class III malocclusion with mild crowding in the maxillary arch and severe crowding in the mandibular arch (Figure 54.8). Inspection, manual structure analysis and instrumental functional analysis of the TMJs showed an unphysiological force on both joints. A panoramic radiograph showed a full dentition with retention of the mandibular left third molar. The lateral cephalogram showed skeletal class I relationship according the ANB angle. But Wits appraisal was −6.4 mm. The intermaxillary angle (ML-NL) was increased with a value of 31.5°. The treatment plan was to remove the stress on the TMJs and reduce pain. The patient received a centric relation splint and manual therapy. After a painless period of nine months, she started orthodontic treatment. Since the first and second molars over-erupted, it was not suit-

able to extrude the incisors and premolars to close her open bite in this case. Therefore, the treatment plan was to intrude the over-erupted molars using palatal TADs. Using the TADmatch module in Onyx Ceph3 Software, the implant position was planned with two Ortholox miniscrews 2.2 mm in diameter and 12 mm long from the Ortholox System (Promedia, Germany). A surgical guide was manufactured using the direct print method with the insertion guide and a biocompatible resin. After intraoral anesthesia, the surgical guide was placed into the patient’s mouth. Due to the steep curvature of her palatal bone, it was necessary to make two 1.3 mm diameter pilot holes to prevent the miniscrews from slipping. Once prepared, the two miniscrews were inserted using an optimized insertion tool for guided implantation with a depth stop. The intrusion mechanic appliance was incorporated at the same visit as the miniscrew implantation. A lateral cephalogram made after miniscrew implantation and insertion of the intrusion appliance showed a good ­parallel position of both miniscrews.

Figure 54.8  Case 54.1: Initial records.

(Continued )

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Figure 54.8  (Continued)

Figure 54.9  Case 54.1: Treatment progress records.

A fixed appliance was bonded four months after starting the molar intrusion. The bracket position was digitally planned based on an intraoral scan. Although the intrusion appliance stayed in situ, brackets were bonded using a digitally designed indirect bonding tray. During treatment, the maxillary first and second molars were intruded approximately 1.5–2 mm, and her anterior open bite was

closed by counterclockwise autorotation of the mandible (Figure 54.9). No extrusion mechanics or anterior elastics were used at any time during treatment. The fixed appliance was removed after 13 months of treatment. Fixed retainers were bonded, and the patient received retention aligners. Her open bite was closed, and she showed a skeletal Class I relationship (Figure 54.10).

Chapter 54  Safe and Precise TAD Placement in the Anterior Palate

Figure 54.10  Case 54.1: Final records.

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R ­ eferences 1 Feldmann I, Bondemark L. Orthodontic anchorage: a systematic review. Angle Orthod. 2006;76:493–501. 2 Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod. 1997;31:763–767. 3 Wilmes B, Beykirch S, Ludwig B, et al. The B-Mesialslider for non-compliance space closure in cases with missing upper laterals. Semin Orthod. 2018;24:66–82. 4 Wilmes B, Nienkemper M, Ludwig B, et al. Esthetic Class II treatment with the Beneslider and aligners. J Clin Orthod. 2012;46:390–398; quiz 437. 5 Ludwig B, Glasl B, Kinzinger GS, et al. The skeletal frog appliance for maxillary molar distalization. J Clin Orthod. 2011;45:77–84; quiz 91. 6 Poggio PM, Incorvati C, Velo S, Carano A. “Safe zones”: a guide for miniscrew positioning in the maxillary and mandibular arch. Angle Orthod. 2006;76:191–197. 7 Chaimanee P, Suzuki B, Suzuki EY. “Safe zones” for miniscrew implant placement in different dentoskeletal patterns. Angle Orthod. 2011;81:397–403. 8 Ludwig B, Glasl B, Bowman SJ, et al. Anatomical guidelines for miniscrew insertion: palatal sites. J Clin Orthod. 2011;45:433–441; quiz 467. 9 Kim HJ, Yun HS, Park HD, et al. Soft-tissue and corticalbone thickness at orthodontic implant sites. Am J Orthod Dentofacial Orthop. 2006;130:177–182.

10 Ryu JH, Park JH, Vu Thi Thu T, et al. Palatal bone thickness compared with cone-beam computed tomography in adolescents and adults for mini-implant placement. Am J Orthod Dentofacial Orthop. 2012;142:207–212. 11 Gracco A, Lombardo L, Cozzani M, Siciliani G. Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement. Am J Orthod Dentofacial Orthop. 2008;134:361–369. 12 Winsauer H, Vlachojannis C, Bumann A, et al. Paramedian vertical palatal bone height for mini-implant insertion: a systematic review. Eur J Orthod. 2014;36:541–549. 13 King KS, Lam EW, Faulkner MG, et al. Vertical bone volume in the paramedian palate of adolescents: a computed tomography study. Am J Orthod Dentofacial Orthop. 2007;132:783–788. 14 Eastman TR. ALARA and digital imaging systems. Radiol Technol. 2013;84:297–298. 15 Kim YJ, Lim SH, Gang SN. Comparison of cephalometric measurements and cone-beam computed tomography-based measurements of palatal bone thickness. Am J Orthod Dentofacial Orthop. 2014;145:165–172.

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55 Correction of Occlusal Canting with TADs Tae-Woo Kim Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, South Korea

55.1 ­Introduction Occlusal canting can successfully influence smile esthetics, depending on the amount of gingival display, buccal corridor, and upper to lower dental midline discrepancy [1]. Springer et al. [1] reported that looking at a full-face view, people prefer less maximum gingival display, less buccal corridor, less upper to lower midline discrepancy, and less cant of the occlusal plane. Significant interaction has been observed between occlusal cant and the amount of gingival display [2]. An increase in both occlusal plane cant and gingival display negatively influences smile attractiveness, but it is interesting that the occlusal plane cant has less influence when gingival display increases, and vice versa [2]. Padwa et  al. [3] found that both untrained and trained observers could detect occlusal cants with 90% accuracy when they were greater than 4° in frontal view photos [3]. The maximum acceptable cant of the occlusion was 2.75°, given smile widths from 50 to 70 mm, while the vertical measure of the cant could be from 2.5 to 3.3 mm [1]. For patients who refuse two-jaw surgery, temporary anchorage devices (TADs) may be a good treatment alternative, although the occlusal cant might not be perfectly addressed. With the advent of TADs over the past 10 years, orthodontic molar intrusion and occlusal plane canting correction have been reported [4–10]. Occlusal canting problems include maxillary occlusal cant, mandibular occlusal cant, and occlusal cant due to skeletal facial asymmetry. Typically, occlusal canting correction has not meant correction of skeletal facial asymmetry, but smile esthetics can be improved. The four cases

presented in this chapter will demonstrate the mechanics of occlusal canting correction with TADs.

55.2  ­Categorization of Maxillary Occlusal Canting and Overview of the Cases Maxillary occlusal canting can be divided into two types. Type 1 has a wavy occlusal plane, but clinically, the crowns are in good angulation and inclination (Figure 55.1a). Type 2 has total maxillary skeletal canting (Figure 55.1b). With Type 1, when a plain archwire is applied, the angulations and inclinations of the affected teeth will be in the wrong directions, resulting in tilting of incisors and a worsening of buccolingual inclination of the posterior teeth (Figure 55.2a). With Type 1, a segmental surgery is the preferred choice for intrusion (Figure  55.2b). This option offers benefits such as reduced treatment time and good control of the buccolingual inclinations of the affected teeth. Another option is to place two TADs, one on the buccal side and one on the palatal, to unilaterally intrude the posterior teeth. This non-surgical approach can achieve similar control of the inclinations as with segmental surgery (Figure 55.2c). Case  55.1 is an example of the correction of a Type 1 occlusal cant (Figures  55.3 and 55.4). The correction was started at the leveling stage to minimize the unwanted tilting of the anterior teeth during unilateral intrusion of the left maxillary posterior teeth. In treating Type 2 cases (Figures 55.5 and 55.6), Le Fort I maxillary surgery is the first choice for unilateral ­impaction

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(a)

(b)

Figure 55.1  Two types of occlusal canting. (a) Type 1 has good clinical crown angulations and inclinations, with a wavy occlusal plane. (b) Type 2 has total maxillary skeletal canting.

(a)

(b)

(c)

Figure 55.2  Correction of Type 1 occlusal canting. (a) When a plain archwire is applied, the angulations and inclinations of unwanted teeth will be moved in the wrong direction. (b) For canting correction of Type 1, a segmental surgery was the first choice. (c) Another option is to place two TADs, one on buccal and one on palatal, to control the buccolingual inclination during intrusion.

Chapter 55  Correction of Occlusal Canting with TADs

(a)

Before

(b)

During

(c)

After

Figure 55.3  Case 55.1: Example of correction of Type 1 occlusal canting. At the initial leveling stage, unilateral intrusion was started at the initial leveling stage with Type 1. While intruding the left maxillary posterior teeth, a lateral open bite developed. To correct the mouth protrusion and mandibular asymmetry, two-jaw orthognathic surgery was carried out.

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0.022″ SWA brackets + 0.016″ × 0.022″ NiTi

0.018″ standard brackets + 0.016″ NiTi

1.6 mm (D) × 8 mm (L)

1.6 mm (D) × 6 mm (L)

0.016″ NiTi

0.016″ × 0.022″ NiTi

Buccal view

Palatal view

Figure 55.4  Biomechanics applied in Case 55.1.

(a)

Before

(b)

During

(c)

After

Figure 55.5  Case 55.2: Example of how a Type 2 occlusal cant was corrected. In Type 2, unilateral intrusion was started after leveling. After intruding the right maxillary posterior teeth, the lateral open bite that developed during treatment was corrected with box elastics (1/4-in, 6 oz).

Chapter 55  Correction of Occlusal Canting with TADs

0.022″ SWA brackets + 0.019″ × 0.025″ SS

0.018″ standard brackets + 0.018″ SS

1.6 mm (D) × 6 mm (L)

1.6 mm (D) × 8 mm (L)

0.018″ SS

0.019″ × 0.025″ SS

Buccal view

Palatal view

Figure 55.6  Biomechanics applied in Case 55.2.

as it reduces treatment time and helps to control inclination. When non-surgical orthodontic treatment is necessary, it is suggested that intrusion of the maxillary posterior teeth be started after the leveling stage. Case  55.2 is an example of correction of Type 2 occlusal cant. A heavy archwire of 0.019 × 0.025-in stainless steel (SS) and two TADs, one on the buccal side and the other on the palatal side, were used to minimize the unwanted inclination of the right maxillary posterior teeth (Figure 55.6). Case 55.3 shows an indication of a buccal plate, in which the buccal interradicular TAD loosened as the posterior teeth were being intruded (Figures 55.7 and 55.8). Case 55.4 shows an example of how the mechanics of combining a modified intrusion transpalatal arch (TPA) and a midpala-

tal TAD can be used to treat a patient with anterior and lateral open bite successfully (Figures 55.9 and 55.10).

55.3  ­Conclusions Maxillary canting can be divided into two types which were explained and demonstrated with case reports. Four occlusal canting cases treated with different modalities were presented. Although facial asymmetry cannot be corrected perfectly without orthognathic surgery, occlusal canting was improved with TADs. Occlusal canting correction with TADs is still challenging but the cases presented in this chapter show it is a viable treatment option.

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(a)

Before

(b)

During

(c)

After

Figure 55.7  Case 55.3: Buccal interradicular TAD failed and was replaced by a miniplate. Maxillary dental midline deviation and occlusal canting was corrected by unilateral retraction and intrusion.

Chapter 55  Correction of Occlusal Canting with TADs

Anchor plate AP-YL-013

0.019″ × 0.025″ SS

Buccal view 1.6 mm (D) × 8 mm (L)

0.016″ × 0.022″ SS

Palatal view Figure 55.8  Biomechanics applied in Case 55.3.

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(a)

Before

(b)

During

(c)

After

Figure 55.9  Case 55.4: One midpalatal TAD and a unilateral intrusion TPA were used to correct maxillary canting and open bite. One buccal TAD and a Burstone precision lingual arch were used to correct mandibular canting and open bite.

Chapter 55  Correction of Occlusal Canting with TADs

Unilateral intrusion TPA

Palatal sheath

1.6 mm (D) × 6.0 mm (L)

Figure 55.10  Biomechanics applied in Case 55.4.

Case 55.1  Skeletal Class II with Facial Asymmetry and Wavy Occlusal Canting (Type 1) Diagnosis A 22-year-old female presented with the chief complaint of facial asymmetry. On smiling, there were discrepancies in the height of her eyes, corners of her mouth, and gonial angles. Her canine and molar relationships showed Class II tendency. Her maxillary incisors had normal angulation while her maxillary left posterior teeth were extruded (Figure 55.3a). In her magnetic resonance imaging scans, the right temporomandibular joint (TMJ) showed anterior disc displacement without reduction and a degenerated condyle. Her left TMJ showed anterior disc displacement with reduction. Treatment Progress On the labial and buccal surfaces, SmartClip brackets with 0.022-in slots (3M, St. Paul, MN, USA) were bonded, while on the palatal surfaces of her maxillary left first first premolar to second molar, 0.018-in standard brackets and a buccal tube were used. Two JA-type TADs (Jeil Medical, Seoul, South Korea) were applied buccally and

palatally. On the buccal side, one TAD (1.6 mm in length and 6 mm in diameter) was placed in the interradicular area between the left maxillary second premolar and first molar; on the palatal side, one TAD (1.6 mm in length and 8 mm in diameter) was placed in the interradicular area between the left maxillary first and second molars (Figure  55.4). Intrusion was started at the leveling stage with elastomeric chains, the labial arch wire was upgraded to a 0.016 × 0.022-in nickel–titanium (NiTi) wire. The palatal segmental wire was a 0.016-in NiTi. The labial arch wire was continuously increased to a 0.019 × 0.025-in SS and the palatal segmental wire was increased to 0.018-in SS. After intruding the left posterior teeth for two months, the maxillary occlusal canting was somewhat improved and a unilateral open bite was achieved (Figure 55.3b). After seven months of intrusion, lower occlusal canting and mandibular asymmetry were corrected by intraoral vertical ramus osteotomy, genioplasty, and angle reduction. Before the orthognathic surgery, the patient also complained of upper anterior protrusion, so a maxillary posterior impaction (Continued )

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procedure was added into her surgical treatment plan. If total maxillary dentition distalization had been done before orthognathic surgery, the Le Fort I surgery could have been avoided. Treatment Results Total treatment time was one year and eight months. The patient showed a nicely balanced and harmonious

smile with resolution of occlusal canting and facial asymmetry (Figure 55.3c). Fixed retainers with 0.8 mm twisted wire (TwistFlex, REF 260-0321; 3M, St. Paul, MN, USA) were bonded from canine to canine in the maxilla and mandible. During treatment, she experienced no TMJ discomfort. A good interdigitation of her teeth and an acceptable overjet and overbite relationship were achieved.

Case 55.2  Skeletal Class II with Facial Asymmetry and Straight Occlusal Canting (Type 2) Diagnosis A 27-year-old female presented with the chief complaints of open bite and facial asymmetry. She had splint therapy for two years before visiting Department of Orthodontics, Seoul National University Dental Hospital. On her panoramic radiograph, the left condyle showed severe flattening and remodeling, which had aggravated her mandibular shift to the left side. On MRIs, both TMJs showed anterior disc displacement without reduction and the left condylar head showed degeneration. On smiling, there were discrepancies in the height of her lip commissures and gonial angles. Maxillary and mandibular occlusal planes were tilted but straight, not wavy as in the first case. Canine and molar relationships were end-on Class II. Her maxillary first premolars and mandibular central incisors showed gingival recession. She exhibited tongue thrusting when swallowing and there were spaces between her mandibular anterior teeth which were considered to be related to the tongue habit (Figure 55.5a).

(Jeil Medical) were inserted buccally and palatally (Figure 55.5b and Figure 55.6). On the buccal side, one 1.6 × 6 mm JA-type TAD was placed in the interradicular area between the right maxillary second premolar and first molar. On the palatal side, one 1.6 × 8 mm JA-type TAD was placed in the interradicular area between the right maxillary first molar and second molar. Intrusion was started with elastomeric chains and the maxillary labial arch wire was upgraded to 0.019 × 0.025-in SS and the palatal segmental wire was 0.018-in SS. After two weeks of intrusion, the right maxillary posterior teeth were intruded significantly and a lateral open bite developed in this area (Figure 55.5b). At this stage, a 0.018 × 0.022-in SS mandibular multiple edgewise archwire (MEAW) was placed in the mandibular arch. A 1/4-in 6 oz box elastic band was applied to the right posterior teeth to extrude the mandibular posterior teeth. Up-and-down elastic bands (3/16-in, 6 oz) were applied to extrude the anterior teeth. After seven months, all of the brackets and wires were removed (Figure 55.5c).

Treatment Progress

Treatment Results

Orthognathic surgery was suggested for her treatment plan. After leveling to 0.019 × 0.025-in SS wire but before orthognathic surgery, the open bite was decreased (Figure 55.5b). The patient asked whether her open bite could be treated without surgery. Although her skeletal facial asymmetry was severe, she did not look that bad. After a discussion, we decided to finish without orthognathic surgery, but the patient was advised that her facial asymmetry could not be resolved without surgery. Clarity™ SL straight-wire brackets with 0.022-in slots (3M, St. Paul, MN, USA) were bonded on the labial and buccal surfaces, while 0.018-in standard brackets and a buccal tube were used on the palatal surfaces of her right maxillary first premolar to second molar. After eight months of leveling and space closing, two JA-type TADs

Total treatment time was 15 months. The patient showed a nicely balanced and harmonious smile with improvement of occlusal canting and facial asymmetry (Figure  55.5c). Fixed retainers (0.8 mm TwistFlex wire, REF 260-0321) were bonded from the first premolar to first premolar in the maxilla and the mandible. Throughout the treatment, she experienced no TMJ discomfort. A good interdigitation of her teeth and an acceptable overjet and overbite relationship were achieved. TAD intrusion of the right maxillary posterior teeth with extrusion of the right mandibular posterior teeth by elastics improved the canted occlusal plane. Gingival recession was progressive during treatment. The tongue thrust habit disappeared. The treatment results were stable more than four years after debonding.

Chapter 55  Correction of Occlusal Canting with TADs

Case 55.3  Complicated Case with Occlusal Canting, Midline Discrepancy, Impacted Molars, and Degenerative Joint Disease Diagnosis A 14-year-old female and her parents presented with the chief complaint of multiple impacted teeth (Figure 55.7a). Her problems can be summarized as follows: ●● ●● ●● ●●

●● ●● ●● ●●

●● ●●

Lip and occlusal canting Chin deviation to her right side Lower lip protrusion Maxillary incisors tiled to her right side and the maxillary dental midline was shifted to her right side Crowding of anterior teeth Impacted molars (UR6, UR7, LR7, and LR8) Congenital missing (UR5 and UL5) Right and left TMJs: anterior disc displacement without reduction, degenerative joint disease Skeletal Class II with a steep mandibular plane Facial asymmetry.

The patient and her parents did not want orthognathic surgery to correct the facial asymmetry for financial reasons. In MRIs, both TMJs showed anterior disc displacement without reduction and degenerated condyles. Treatment Progress One year after the first window opening of her right maxillary first molar and mandibular second molar, they erupted spontaneously. A second window opening was made for the impacted right maxillary second molar. It was uprighted with a segmental spring and partially bonded brackets. After all of the impacted molars had erupted, the left maxillary second deciduous molar and two mandibular second premolars were extracted. On the labial and buccal surfaces, SmartClip straight-wire brackets with 0.022in slots were bonded, while on the palatal surfaces of maxillary first and second molars, a standard bracket with 0.018-in slots and a buccal tube were used

(Figure  55.7b). Two JA-type TADs (Jeil Medical) were placed buccally and palatally. On the buccal side, one 1.6 × 6 mm JA-type TAD was placed in the interradicular area between the left maxillary second premolar and first molar. On the palatal side, one 1.6 × 8 mm JA-type TAD was placed in the interradicular area between the left maxillary second premolar and first molar. As the left maxillary posterior teeth were intruded, the buccal TAD came closer to the alveolar crest. Later, this TAD loosened and was replaced by a miniplate (anchor plate, IAP-YL-013; Jeil Medical). The plate was placed surgically by an oral surgeon and a hook was exposed between the left maxillary first and second molars. The palatal screw was stable. When the labial archwire reached 0.019 × 0.025-in SS and the palatal segmental wire was up to 0.016 × 0.022-in SS, unilateral intrusion and retraction was started with elastomeric chains. The tilted maxillary incisors and midline shift were corrected by unilateral retraction of the maxillary anterior teeth. Occlusal canting and open bite were resolved by unilateral intrusion of the maxillary left posterior teeth (Figure  55.8). After one year of unilateral retraction and intrusion, mandibular occlusal canting and asymmetry was improved without orthognathic surgery and at that point, all brackets and wires were removed (Figure  55.7c). Fixed retainers (0.8 mm TwistFlex) were bonded from first premolar to first premolar in the maxilla and mandible.  Treatment Results Total treatment time with a full fixed appliance was three years. The patient showed a nicely balanced and harmonious smile with improved occlusal canting (Figure  55.7c). During treatment she experienced no TMJ discomfort. A good interdigitation of her teeth and an acceptable overjet and overbite relationship were achieved.

Case 55.4  Skeletal Class II with Anterior and Lateral Posterior Open Bite, Facial Asymmetry, and Occlusal Canting Diagnosis A 17-year-old female presented with the chief complaint of “inability to chew anything.” On smiling, she showed maxillary occlusal canting and tongue thrusting (Figure 55.9a). She could bite only with her right molars because her other teeth showed severe open bite. Her

maxillary occlusal plane was sloped to the left while her mandibular occlusal plane sloped to the right. Canine and molar relationships were Class I. Her right maxillary and mandibular posterior teeth were extruded. In her MRIs, the right TMJ showed anterior disc displacement without reduction and a degenerated condyle. Her left (Continued )

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TMJ showed partial anterior disc displacement with reduction. On a panoramic radiograph, her right condyle was very small. On a posteroanterior cephalometic radiogram, her chin was deviated to the right. Because of her chubby cheek, her facial asymmetry did not look so severe in a frontal photograph. She and her parents did not complain about the facial asymmetry. Treatment Progress All maxillary and mandibular teeth were bonded/ banded except for the maxillary second molars (Figure 55.9b) and 0.022-in slot straight-wire brackets (SmartClip) were used on the labial and buccal surfaces. Palatal sheaths (Lingual Sheath Hook Distal; Tomy, Iwaki-city, Japan) were welded on the maxillary first molar bands for an intrusion TPA. Burstone lingual sheaths (Precision Lingual Hinge Cap; Ormco, Glendora, CA, USA) were welded on the lingual surfaces of the mandibular first molar bands for the Precision lingual arch. Her maxillary second molars and mandibular third molars were extracted. After leveling to 0.019 × 0.025-in NiTi, one TAD (JA-type, 1.6 mm in length and 6 mm in diameter; Jeil Medical) was placed in the midpalatal area distal to the maxillary first molars. To facilitate unilateral intrusion, an intrusion TPA was modified with one hook located very near to the midpalatal TAD because no intrusion was needed on the left side. The elastomeric chain on this hook acts as anchorage to resist the palatal force vector from the right elastomeric chain of the TPA (Figures 55.9b and 55.10). When the maxillary occlusal canting was corrected and the anterior open bite was resolved, mandibular unilateral intrusion was started. On the buccal side, one TAD (JA-type, 1.6 mm in length and 6 mm in diameter; Jeil Medical) was placed in the interradicular area between the right mandibular second premolar and first molar. An elastomeric chain was applied for intrusion (Figures 55.9b and 55.10). On the mandibular first molars, a precision lingual arch made of 0.032 × 0.032-in titanium molybdenum alloy (TMA lingual, Burstone, Lower, 233-0010; Ormco) was inserted. On the right side, crown lingual torque was applied to the precision lingual arch to counteract the buccal tipping force from the elastic power chain, then 0.019 × 0.025-in SS archwires were ligated on the maxilla and mandible.

Treatment Results The total treatment time of four years and 11 months was much longer than expected. This was because the patient did not cooperate enough and the progress at the finishing stage was therefore much slower. Fixed retainers (0.8 mm TwistFlex) were bonded canine-tocanine in the maxilla and the mandible. The patient did not experience any TMJ discomfort during treatment. She showed a nicely balanced and harmonious smile with resolution of the open bite, occlusal canting, and facial asymmetry (Figure  55.9c). Without orthognathic surgery, a good interdigitation of her teeth and an acceptable overjet and overbite relationship were achieved. Her maxillary third molar erupted as planned into the second molar position. The patient benefited from this lengthy orthodontic treatment and no further orthodontic treatment will be necessary. In a lateral cephalometric superimposition of before and after treatment, the patient’s maxillary posterior teeth showed intrusion and her mandible rotated counterclockwise. Lower anterior facial height decreased and her retruded chin was considerably improved (Figure 55.11).

Figure 55.11  Case 55.4: Lateral cephalometric superimposition: pre-treatment (black) and post-treatment (red).

Chapter 55  Correction of Occlusal Canting with TADs

­References 1 Springer NC, Chang C, Fields HW, et al. Smile esthetics from the layperson’s perspective. Am J Orthod Dentofacial Orthop. 2011;139:e91–e101. 2 Kaya B, Uyar R. The impact of occlusal plane cant along with gingival display on smile attractiveness. Orthod Craniofac Res. 2016;19:93–101. 3 Padwa BL, Kaiser MO, Kaban LB. Occlusal cant in the frontal plane as a reflection of facial asymmetry. J Oral Maxillofac Surg. 1997;55:811–816. 4 Jeon YJ, Kim YH, Son WS, Hans MG. Correction of a canted occlusal plane with miniscrews in a patient with facial asymmetry. Am J Orthod Dentofacial Orthop. 2006;130:244–252. 5 Ko DI, Lim SH, Kim KW. Treatment of occlusal plane canting using miniscrew anchorage. World J Orthod. 2006;7:269–278. 6 Takano-Yamamoto T, Kuroda S. Titanium screw anchorage for correction of canted occlusal plane in patients with

facial asymmetry. Am J Orthod Dentofacial Orthop. 2007;132:237–242. 7 Hashimoto T, Fukunaga T, Kuroda S, et al. Mandibular deviation and canted maxillary occlusal plane treated with miniscrews and intraoral vertical ramus osteotomy: functional and morphologic changes. Am J Orthod Dentofacial Orthop. 2009;136:868–877. 8 Kang YG, Nam JH, Park YG. Use of rhythmic wire system with miniscrews to correct occlusal-plane canting. Am J Orthod Dentofacial Orthop. 2010;137:540–547. 9 Ahn HW, Seo DH, Kim SH, et al. Correction of facial asymmetry and maxillary canting with corticotomy and 1-jaw orthognathic surgery. Am J Orthod Dentofacial Orthop. 2014;146:795–805. 10 Yanez-Vico RM, Iglesias-Linares A, Cadenas de LlanoPerula M, et al. Management of occlusal canting with miniscrews. Angle Orthod. 2014;84:737–747.

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56 Treatment of Facial Asymmetry with Microimplants Hyo-Sang Park Department of Orthodontics, School of Dentistry, Kyungpook National University, Daegu, South Korea

56.1 ­Introduction Microimplants have been used in many areas of orthodontics since their inception. My first experience with microimplants was for the retraction of anterior teeth to the close premolar extraction space [1, 2]. The treatment results showed that they were well able to provide absolute anchorage for tooth movement. The next application that I focused on was the distalization of whole dentitions using microimplant anchorage [3, 4]. Thanks to the ­absolute nature of microimplant anchorage, the whole ­dentition could be distalized by applying force from microimplants to the teeth. Another popular application for microimplants was open bite treatment with intrusion of the posterior teeth [5–8]. With conventional treatment, intrusion of the posterior teeth was one of the most difficult tooth movements, but it has become a routine treatment since the introduction of microimplants. In addition, microimplants can be used to correct mesially tipped molars [9], to manage impacted canines [10], and to correct scissor bite [11]. Microimplants allow clinicians to move teeth precisely in three dimensions according to the treatment plan, which was difficult to impossible with conventional methods. Facial symmetry is a disharmony of the facial features in which there is a difference between the right and left sides of the face relative to the midsagittal plane or facial midline [12]. Correction of facial asymmetry is difficult and therefore is frequently not done. Treatment options include growth modification, correction of dental transverse occlusal cant in growing young patients, and orthognathic surgery in adult patients. In growing patients, asymmetric functional appliances can alleviate facial asymmetry by growth modification; however, the tooth movement initiated by the appliance may block further correction of the facial asymmetry. This undesirable tooth movement can be

prevented by using microimplants. In addition, asymmetry can be corrected by applying force to the jaw bone with elastics and microimplants. Similarly, transverse maxillary occlusal cant is corrected by intruding the canted-down side and/or extruding the canted-up side with microimplants. Sometimes, the results of orthognathic surgery are not ­satisfactory or are less than expected. One reason for this is  insufficient dental decompensation, which can result in insufficient movement of the jaw bone during surgery. In order to avoid this, it is very important to position the teeth precisely in three dimensions before surgery, and microimplants can help to accomplish this. In this chapter, I will illustrate the usage of microimplants to treat facial asymmetry for growing young patients and for dental decompensation with orthognathic surgery in adult patients.

56.2  ­Growth Modification for Facial Asymmetry in Growing Young Patients Posterior crossbite in growing children can cause lateral deviation of the mandible which can result in facial asymmetry with growth [13] or asymmetrical growth of the mandible or distortion of the mandible by unilateral mastication. The first step in preventing these problems is to correct posterior crossbite and to prevent future deviation of the mandible which might normalize the growth of the mandible [14]. However, if facial asymmetry exists after posterior crossbite has been corrected, an asymmetric appliance can be used to modify growth and reduce the amount of facial asymmetry [15]. Another approach for facial asymmetry in growing young patients suggested by the author is to correct the transverse occlusal cant of the maxillary arch with microimplants. In other words, a skewed maxillary arch needs to be made symmetric and to have same amount of inclination and vertical position of

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Case 56.1  A nine-year-old male presented with facial asymmetry and menton deviation to the left by 5 mm (Figure 56.1). He had a lateral functional deviation. The shape of his mandible was asymmetric, especially in the anterior portion. A lateral cephalogram of the mandibular border showed a large difference between the right and left sides. Treatment consisted of expansion of the maxillary dental arch with a bonded rapid palatal expander to correct the posterior crossbite (Figure 56.2a). Even after the functional lateral deviation had been corrected by expansion of the maxillary arch, the menton deviation and facial asymmetry were still present. Therefore, an asymmetric appliance was delivered to improve his facial asymmetry (Figure  56.2b). The maxillary left molars showed buccal tipping and were positioned buccally compared to those on the right side, a condition that was

Figure 56.1  Pre-treatment photographs and radiographs.

aggravated during expansion. Unilateral constriction of the dental arch was not feasible with just a transpalatal arch (TPA); therefore, lingual force was added to the left molar with a microimplant (SH1312-07, AbsoAnchor®; Dentos Inc., Daegu, South Korea) placed in the palate while constriction force was applied to the molars on both sides with a TPA (Figure 56.2c). Arch symmetry was obtained after unilateral constriction and alignment of the teeth. The maxillary right and left teeth were positioned at the same level, vertically. This gradual movement produced light, uneven occlusal contacts on the right and left sides and reduced the degree of facial asymmetry, especially on the mandible. Initially, the left and right mandibular borders at gonion were different (Figure  56.3a) but were similar after treatment (Figure  56.3b,c). The menton deviation

Chapter 56  Treatment of Facial Asymmetry with Microimplants

(a)

(b)

(c)

Figure 56.2  Case 56.1: Treatment appliances for facial asymmetry. (a) Bonded expander to correct posterior crossbite. (b) Asymmetric appliance. (c) Lingual movement of maxillary left first molar to guide mandible to the right.

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

(i)

(j)

(k)

Figure 56.3  Case 56.1: Treatment progress. Lateral cephalometric radiographs at one year of treatment (a), four years (b), eight years (c). Posteroanterior cephalometric radiographs at one year of treatment (d), four years (e), eight years (f). (g) Three-dimensional constructed image of CBCT. Frontal facial photographs at one year of treatment (h), four years (i), six years (j), eight years (k).

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and asymmetry of the mandibular anterior border were also reduced with treatment (Figure 56.3d–g). A series of facial photographs show gradual improvement of facial asymmetry (Figure 56.3h–k). Even though orthognathic surgery was required to correct the patient’s skeletal Class III malocclusion and the posterior teeth on the right and left sides. This correction of the occlusal plane produces uneven occlusal contacts between the deviated and non-deviated sides, and consequently produces a force that relieves the facial asymmetry. Unfortunately, it is hard to achieve and retain this sort of tooth movement with conventional orthodontic methods. Therefore, microimplants play an essential role in the treatment of facially asymmetric patients.

56.3  ­Improvement of Facial Asymmetry During Fixed Orthodontic Treatment Mild facial asymmetry is frequently observed in dental clinics. Unfortunately, the only solution for facial asymmetry in adults is orthognathic surgery, but because it is expensive and poses some risk, patients hesitate to go the surgery route. For this reason, orthodontists often ignore the facial asymmetry when it is not severe (i.e. less than 2 mm of menton deviation), but some patients request that

(a)

improve dental interdigitation and facial harmony in this patient, better treatment results might be expected by surgery because of alleviated mandibular asymmetry by growth modification. But if the patient has no anteroposterior skeletal discrepancy, the facial asymmetry might be corrected during growth without orthognathic surgery. their facial asymmetry be corrected even though it is mild. In such cases, the orthodontist can reduce the transverse cant of the maxillary occlusal plane and guide the mandible to the non-deviated side to improve facial asymmetry with microimplants. Even with severe facial asymmetry, when patients are unwilling to accept orthognathic surgery, orthodontists can reduce the degree of facial asymmetry with microimplants. Treatment includes intrusion of the maxillary posterior teeth on the non-deviated side (Figure 56.4a,c) and extrusion of the maxillary posterior teeth on the deviated side (Figure 56.4a,b). The intrusion is more necessary in hyperdivergent patients to reduce vertical divergency, and extrusion is a better choice for hypodivergent patients. In order to guide the mandible to the non-deviated side, elastics and a resin guide should be applied on the posterior teeth (Figure  56.4d,e). Elastic force can be applied from the microimplant or the maxillary posterior teeth connected to the microimplant to the microimplant placed into the mandibular anterior tooth area (Figure 56.4e).

(b)

(c)

(d)

(e)

Figure 56.4  Treatment methods to improve facial asymmetry without orthognathic surgery. (a) Extrusion of the maxillary posterior teeth with a microimplant and extrusion spring on the deviated side and intrusion of the posterior teeth with microimplants on the non-deviated side can move the mandible to the non-deviated side. (b) Extrusion spring with a microimplant for extrusion of the maxillary right teeth. (c) Intrusion of the posterior teeth on the non-deviated side. (d) Guide resin to guide the mandible to the nondeviated side. (e) Elastics between the maxillary molar and a microimplant on the mandible, so it can move the mandible to the non-deviated side.

Chapter 56  Treatment of Facial Asymmetry with Microimplants

Case 56.2  A 13-year-old patient presented with anterior crowding, facial asymmetry with menton deviation to the right by 5.3 mm (Figure  56.5) and a lip cant with the left side down. Cone-beam computed tomography (CBCT) and a panoramic radiograph showed shorter ramal height on the right. Orthognathic surgery was proposed to the patient as the ideal treatment, but they declined it for financial reasons, so the treatment plan was compromised to just level and align the teeth. The molar relationships were end-on Class II on the right and end-on Class III on the left. In order to relieve the maxillary anterior crowding, the maxillary first premolars were extracted and alignment was started. During alignment, Class II and Class III elastics were used on both sides in a direction that would help reduce facial asymmetry. The facial asymmetry was re-evaluated and a resin build-up was placed on the buccal cusp of the maxillary right first molar to guide the mandible to the left (Figure 56.4d), and a microimplant (SH1312-07,

AbsoAnchor) was placed between the ­maxillary left second premolar and first molar to apply intrusion force to the maxillary left posterior teeth (Figure  56.4c,e). The intrusion of the maxillary left posterior teeth helped to correct the facial asymmetry, but it did not improve the patient’s vertical facial dimensions, considering their low FMA angle (20°). Extrusion of the maxillary right posterior teeth might be a better option, so another ­ microimplant (SH1312-07, AbsoAnchor) was placed later between the maxillary right second premolar and first molar, and an extrusion spring was delivered to extrude the maxillary right posterior teeth and tip their lingual crowns (Figure 56.4c).The resin guide on the buccal cusp of the  maxillary right first molar was  adjusted to guide  the  mandible to the left. Brackets on the maxillary  right  ­second premolar and second molar  were removed to allow extrusion and settling (Figure 56.4d). This  ­extrusion helped to retain the new position of  the  mandible. An  elastic was used between the

Figure 56.5  Case 56.2: Pre-treatment photographs, panoramic radiograph, and 3D constructed CBCT image.

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­ axillary left first molar and microimplant that had been m placed between the mandibular left canine and first premolar to directly apply a force to the mandibular bone to correct the facial asymmetry (Figure 56.4e). After five years of treatment, the patient’s facial asymmetry was corrected with resolution of the lip cant. Good interdigitation with Class I canine and Class II molar

relationships was achieved (Figure 56.6). The initial variation in ramal height was corrected and there was a similar length in the two sides after treatment. Gradual changes in occlusion, occlusal functional force from the resin guide, and light elastic force to the mandible might induce bone formation on the right and resorption on the left condyles which helped to correct the facial asymmetry.

Figure 56.6  Case 56.2: Post-treatment photographs, panoramic radiograph, and 3D constructed CBCT image.

56.4  ­The Use of Microimplants in Surgical Correction of Facial Asymmetry The treatment of facial asymmetry after the completion of growth requires orthognathic surgery in most cases. However, soft tissue outcomes are not always satisfactory even after orthognathic surgery. Insufficient dental decompensation is one of main reasons for this [16]. Since the final position of the mandibular jaw bone is determined by the position of the teeth, inappropriate or insufficient ­dental

decompensation will result in insufficient correction of the mandibular position and unsatisfactory outcomes. The dental compensation in facial asymmetry patients consists of a transverse cant of the occlusal plane and a variation in the inclination of the teeth. In the maxillary arch, there is extrusion and slight linguoversion of the posterior teeth on the non-deviated side, buccal inclination of the posterior teeth on the deviated side, and a shift of the dental midline to the deviated side. In the mandibular arch, there is lingual tipping of the posterior teeth on the

Chapter 56  Treatment of Facial Asymmetry with Microimplants

deviated side, a slight buccal tipping of the posterior teeth on the non-deviated side, and a shift of the mandibular dental midline to the deviated side but tipped mandibular incisors toward the non-deviated side [17]. The two-jaw orthognathic surgery for facial asymmetry treatment includes maxillary surgery to correct the transverse occlusal cant. With this surgery, the transverse occlusal cant is corrected by adding more impaction on the down-canted side or more downward movement of the jaw bone on the up-canted side; however, the difference in inclination of the posterior teeth on the deviated vs. nondeviated side will not become parallel just by maxillary jaw movement. Therefore, decompensation of the dentition is necessary before surgery in the combination surgery/ orthodontic treatment options to correct facial asymmetry. Conventionally, elastics have been used to remove dental compensation, and a cross elastic is helpful to correct dental compensation on the deviated side by causing a buccal tipping movement of the mandibular posterior teeth and a lingual tipping movement of the maxillary posterior teeth. The midline elastics move the maxillary dental midline to the non-deviated side and the mandibular midline to the deviated side. However, elastics do not produce a precise movement and it is reciprocal always. When teeth are incorrectly positioned in just one arch, correction is required only in that arch. Elastics cannot be used in this situation due to the reciprocal charateristics they have on other teeth. Furthermore, it is very difficult to correct a transverse cant of the occlusal plane with conventional appliances. In order to position the teeth accurately in three dimensions, microimplants are necessary. They can be used to correct the vertical position of the posterior teeth which corrects the transverse cant of the occlusal plane, the inclination of

Figure 56.7  Decompensation as pre-surgical orthodontic treatment with microimplants and mandibular-only surgery (green arrow) for facial asymmetry treatment. Intrusion of the maxillary posterior teeth on the non-deviated side and lingual tipping of the maxillary posterior teeth on the deviated side, and buccal tipping of the mandibular posterior teeth on the deviated side can be done with microimplant anchorage and mandibularonly surgery to effectively correct facial asymmetry.

the posterior teeth on the maxillary and mandibular arches, and the dental midline relative to the skeletal midline (Figure 56.7).

Case 56.3  A 21-year-old male had severe facial asymmetry with 12 mm menton deviation to the left. Full Class III molar relationship was evident on the right side with anterior open bite on his right side. Skeletally, he had a skeletal Class III pattern with severe facial asymmetry (Figure 56.8). CBCT analysis showed that the vertical and horizontal position of the patient’s maxillary jaw bone was normal relative to the FH and midsagittal planes. However, his maxillary right first molar was positioned 4.2 mm lower than the left. Horizontally the maxillary left first molar and canine were positioned buccally by 7.1 mm and 5.5 mm, respectively, as compared to those on the right. The right ramus and mandibular body were longer than those on the left by 9 mm and 9.4 mm, respectively. The difference in inclination of the maxillary pos-

terior teeth between right and left sides were 10.4° and 11°, respectively. The treatment plan included dental decompensation by orthodontic treatment with microimplants and onejaw mandibular surgery. In order to intrude the maxillary right posterior teeth, one microimplant (SH1312-07, AbsoAnchor) was placed into buccal alveolar bone between the first and second molars (Figure 56.9a). For lingual tipping and lingual movement of the maxillary left posterior teeth, another microimplant (SH1312-10, AbsoAnchor) was placed palatally (Figure 56.9b). To apply intrusion force to the canine and first premolar, the microimplant (SH1312-07, AbsoAnchor) was placed between the maxillary right canine and first premolar (Figure 56.9c). In order to move mandibular midline and (Continued )

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Figure 56.8  Case 56.3: Pre-treatment photographs, lateral cephalogram, and 3D constructed CBCT image.

to correct angulation of the mandibular anterior teeth, protraction force was applied to the mandibular left first molar from the microimplant (SH1413-06, AbsoAnchor) that was placed between the mandibular right canine and first premolar (Figure 56.9d). After 13 months of dental decompensation, the buccal crossbite on the left side was worse and there was no evidence of occlusal contact on the right side (Figure  56.9e–g). The maxillary transverse occlusal plane was parallel relative to the interpupillary line, while the inclination of the maxillary posterior teeth were parallel to each other on both sides. The mandibular dental midline was moved to the left and was now

coincident with menton. The one-jaw mandibular surgery and bilateral sagittal split osteotomy were performed at 13 months of treatment. In addition, paranasal allograft augmentation was performed. The treatment was completed at 16 months of treatment. Facial asymmetry was improved and there was good interdigitation with Class I canine and molar relationships (Figure 56.10). Menton deviation was corrected to 1 mm from the initial 12 mm and there was less than 1 mm of difference in the vertical and horizontal position of the right and left maxillary first molars relative to the FH and midsagittal plane. The difference in axial inclination of the right and left maxillary first molars was 2.4°.

Chapter 56  Treatment of Facial Asymmetry with Microimplants

(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

Figure 56.9  Case 56.3: (a) Intrusion of the maxillary molars with a microimplant on the non-deviated side. (b) Intrusion of the maxillary molars from a palatal microimplant on the deviated side. (c) Intrusion of the buccal teeth with microimplants on the non-deviated side. (d) Protraction of the mandibular right posterior teeth to shift the mandibular dental midline to the left. (e–h) After decompensation, intraoral photographs and 3D constructed CBCT image.

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Figure 56.10  Case 56.3: Post-treatment photographs, lateral cephalogram, and 3D constructed CBCT image.

56.5 ­Discussion When treating facial asymmetry with growth modification, the condylar position and occlusion are modified during treatment [18]. The gradual changes in condylar position might not produce temporomandibular disorder, but changes in condylar growth and glenoid fossa remodeling can improve facial asymmetry. This kind of condylar growth and glenoid fossa remodeling were observed even in young adults who were treated with Herbst appliances [19]. In Case 56.2, there was a big improvement in facial asymmetry. The ramal height was shorter on the right side than on the left side at pre-treatment, but it became similar to that of the left side after treatment with bone apposition on the right condyle and bone resorption or less growth of the left condyle. The patient did not experience any discomfort, pain, or clicking sounds of her temporomandibular joint (TMJ). In order to prevent TMJ

problems, this treatment should be done gradually over a relatively long treatment time. The surgical option for facial asymmetry is usually twojaw surgery. Maxillary surgery is necessary to correct the transverse cant of the occlusal plane, but the accuracy of two-jaw surgery is inferior to that of mandibular one-jaw surgery [20, 21]. Inaccurate movement of the maxillary bone during surgery may produce large errors in the mandibular bone position. Furthermore, while the maxillary bone position is not critical to facial asymmetry, the menton deviation ultimately influences facial asymmetry [22]. The important thing in the maxilla is a symmetric position of the teeth vertically and horizontally. So, the maxillary teeth can act as a guide to orient the mandibular bone through occlusal contacts with the mandibular teeth. With microimplant anchorage, transverse occlusal cant and axial inclination of posterior teeth can be corrected by orthodontic treatment to achieve parallelism between the

Chapter 56  Treatment of Facial Asymmetry with Microimplants

deviated and non-deviated sides. And facial asymmetry can be improved with mandibular one-jaw surgery. Microimplants as anchorage have brought big changes in facial asymmetry treatment.

56.6  ­Summary In early treatment of facial asymmetry, attempts were made to correct posterior crossbite by expanding the maxillary arch after asymmetric appliance treatment. However, correction of the mandibular position was limited in many patients because the transverse and vertical position of their maxillary posterior teeth was not the same on both sides. Today, microimplants can be used in such cases to equalize the vertical and anteroposterior positions and to hold the corrected positions. In camouflage treatment of mild facial asymmetry with transverse cant of the occlusal plane, microimplants can be

utilized to apply intrusion force to the maxillary posterior teeth on the non-deviated side and extrusion force to the maxillary posterior teeth on the deviated side. A gradual change in occlusal contact may shift the mandible to the non-deviated side and thus improve facial asymmetry. In orthognathic surgical treatment of facial asymmetry, microimplants can be used for dental decompensation such as intrusion of the maxillary posterior teeth on the non-deviated side and lingual tipping of the maxillary posterior teeth on the deviated side, and to shift the mandibular anterior teeth to the deviated side. These decompensation movements with microimplants can eliminate the need for maxillary surgery to correct a transverse occlusal cant and provide more predictable results with one-jaw mandibular surgery. The precise positioning of teeth during decompensation with microimplants provides sufficient space for movement of the mandibular jaw during surgery, thus improving the accuracy of the surgery. Therefore, microimplants are finding an increased importance in the treatment of facial asymmetry.

R ­ eferences 1 Park HS. The skeletal cortical anchorage using titanium microscrew implants. Korean J Orthod. 1999;29:699–706. 2 Park HS, Bae SM, Kyung HM, Sung JH. Micro-implant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin Othod. 2001;35:417–22. 3 Park HS, Bae SM, Kyung HM, Sung JH. Simultaneous incisor retraction and distal molar movement with microimplant anchorage. World J Orthod. 2004;5:164–171. 4 Park HS, Kwon TG, Sung JH. Nonextraction treatment with microscrew implants. Angle Orthod. 2004;74:539–549. 5 Park YC, Lee SY, Kim DH, Jee SH. Intrusion of posterior teeth using mini-screw implants. Am J Orthod Dentofacial Orthop. 2003;123:690–694. 6 Park HS, Jang BK, Kyung HM. Molar intrusion with micro-implant anchorage. Aust J Orthod. 2005;21:129–135. 7 Park HS. Kwon OW. Sung JH. Nonextraction treatment of an anterior openbite with microscrew implant anchorage. Am J Orthod Dentofacial Orthop. 2006;130:391–402. 8 Park HS, Kwon TG, Kwon OW. Treatment of openbite with microscrew implant anchorage. Am J Orthod Dentofacial Orthop. 2004;126:627–636. 9 Park HS, Kyung HM, Sung JH. A simple method of molar uprighting with micro-implant anchorage. J Clin Orthod. 2002:36: 592–596. 10 Park HS, Kwon OW, Sung JH, Micro-implant anchorage for forced eruption of impacted canine, J Clin Orthod. 2004;38:297–302.

11 Park HS, Kwon OW, Sung JH, Uprighting second molars with micro-implant anchorage, J Clin Orthod. 2004;38:100–103. 12 Peck H, Peck S. A concept of facial esthetics. Angle Orthod. 1970;40:284–318. 13 Schmid W, Mongini F, Felisio A. A computer-based assessment of structural and displacement asymmetries of the mandible. Am J Orthod Dentofacial Orthop. 1991;100:19–34. 14 Kecik D, Kocadereli I, Saatci I. Evaluation of treatment changes of functional posterior crossbite in the mixed dentition. Am J Orthod Dentofacial Orthop. 2007;131:302–315. 15 Sidiropoulou S, Antoniades K, Kolokithas G. Orthopedically induced condylar growth in a patient with hemifacial microsomia. Cleft Palate Craniofac J. 2003;40:645–650. 16 Sekiya T, Nakamura Y, Oikawa T, et al. Elimination of transverse dental compensation is critical for treatment of patients with severe facial asymmetry. Am J Orthod Dentofacial Orthop. 2010;137:552–562. 17 Park HS. Microimplants in Orthognathic Surgical Orthodontics. Daegu, South Korea: Dentos, 2015, pp. 8–18. 18 Hesse KL, Artun J, Joondeph DR, Kennedy DB. Changes in condylar position and occlusion associated with maxillary expansion for correction of functional unilateral posterior crossbite. Am J Orthod Dentofacial Orthop. 1997;111:410–418.

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1 9 Ruf S, Pancherz H. Temporomandibular joint remodeling in adolescents and young adults during Herbst treatment: a prospective longitudinal magnetic resonance imaging and cephalometric radiographic investigation. Am J Orthod Dentofacial Orthop. 1999;115:607–618. 20 Jacobson R, Sarver DM. The predictability of maxillary repositioning in LeFort I orthognathic surgery. Am J Orthod Dentofacial Orthop. 2002;122:142–154.

21 Gerbo LR, Poulton DR, Covell DA, Russell CA. A comparison of a computer-based orthognathic surgery prediction system to postsurgical results. Int J Adult Orthodon Orthognath Surg. 1997;12:55–63. 22 Severt TR, Proffit WR. The prevalence of facial asymmetry in the dentofacial deformities population at the University of North Carolina. Int J Adult Orthodon Orthognath Surg. 1997;12:171–176.

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57 Facial Asymmetry: Non-surgical Orthodontic Treatment Considerations Kelvin Wen-Chung Chang Division of Orthodontics and Dentofacial Orthopedics, Department of Dentistry, National Taiwan University Hospital, Taipei, Taiwan

57.1 ­Introduction Perfect bilateral symmetry is rarely found in human bodies and facial asymmetry is common in the general population, often presenting subclinically [1–3]. A mild degree of asymmetry is relatively normal and is easily ignored by the patient. Surgical intervention is usually not the first treatment option. Nowadays, patient expectations from orthodontic treatment are not just straight teeth, but a harmonious face and beautiful smile as well [4, 5]. Because of this, on occasion we are required to fix the malocclusion of a deviated jaw base without surgery. The purpose of this chapter is to first classify facial asymmetry through an easy clinical examination. In addition to the traditional Angle classifications, the rotational descriptors of roll and yaw from the field of aeronautics are helpful in describing 3D spatial orientation. Dentoalveolar compensations or dental characteristics associated with the different skeletal asymmetries that can provide some clues to possible solutions are then introduced. Camouflage treatment can be used to correct transverse occlusal cant (i.e. to level the anterior occlusal plane as much as possible). Lastly, the selection of an effective treatment modality using temporary anchorage devices (TADs) will be discussed. This chapter will show that versatile applications of TADs can be advantageous in treating facial asymmetry non-surgically.

57.2  ­Etiology and Classification The literature highlights several factors that contribute to the development of facial asymmetries. Chia et  al. [6] suggested that asymmetries could have pathological, traumatic, functional, or developmental factors. Cheong and Lo [7] reported that the causes of facial asymmetry can be grouped into three main categories: congenital,

acquired, and developmental. As for the classification of craniofacial asymmetries, Bishara et al. [8] suggested that asymmetries could be classified as dental, skeletal, muscular, or functional. Hwang [9] developed a classification system for facial asymmetries according to their main morphological features. Four types of asymmetry were recognized based on the skeletal analysis of deviation of the chin and the bilateral difference between mandibular rami lengths. These studies gave us the whole picture of the complexity of the craniofacial skeleton; however, the majority of skeletal facial asymmetries are of mild to moderate degrees, so the main concern is how to treat them without surgery. Many of the classifications were developed for the purpose of surgery [10–12]. That is why they usually focused on the position of the chin. But this is not an appropriate landmark for diagnosing facial asymmetry. If the facial asymmetry is judged by whether there is chin deviation or not, some underlying skeletal discrepancies might be overlooked. Therefore, an easy and practical classification system is needed to fit the requirements of clinical application.

57.3  ­New Classification In 1969, Ackerman and Proffit [13] proposed that Angle’s classification should be systematically strengthened by evaluating dental and skeletal relationships in all three planes of space, not merely in the anteroposterior dimension. In 2007, Ackerman et al. [14] proceeded with the use of three aeronautical rotational descriptors (roll, yaw, and pitch) to supplement the planar terms (sagittal, transverse, and vertical) in describing the orientation of the line of occlusion and the esthetic line of dentition (Figure  57.1a). With these three new descriptors, the dentofacial traits could be analyzed in three dimensions and a more comprehensive understanding

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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(a)

(b)

Aircraft rotations

Sagittal plane

Coronal plane

Pitch axis Center of gravity

Pitch

Pitch

Horizontal plane

Roll axis

Roll

Yaw axis

Yaw

Roll

Yaw

Figure 57.1  (a) Three rotational movements: roll, yaw, and pitch. The concept from aeronautics fully describes an object’s orientation in space in addition to its linear movement. (b) Three-dimensional analysis of orientation of the head, jaw, and dentition is incomplete without considering these three rotational movements: roll, yaw, and pitch on the coronal, horizontal, and sagittal planes, respectively.

of the relation between hard tissues and soft tissues could be obtained (Figure 57.1b). This is an easy and practical way to analyze and describe facial asymmetry clinically. From the frontal view of facial photographs (Figure  57.2a), the relative vertical position (on the coronal plane) of the bilateral gonial angles and chin button (with or without lateral deviation) can be observed. If there is a roll rotation of the mandible, the chin will be deviated to the side with a higher positioned gonial angle. Then the maxillary occlusal plane and the mandibular occlusal plane, respectively, can be examined (Figure 57.2b) to identify their relationships with the horizontal plane or the interpupillary line (parallel or diverted). Usually there will be an associated maxillary cant combined with the roll rotation of the mandible in the same direction. This maxillary cant could be regarded as a compensation of the mandible deviation during growth and development. It then can be characterized as skeletal, dentoalveolar, or a combination thereof. From the submental view of facial photos (Figure 57.2c), the relative positions of bilateral gonial angles and the mouth angles on the horizontal plane can be observed. If one side is more upward and the other side is more downward, there is a yaw rotation of the maxilla (mouth angle) or the mandible (gonial angle). Yaw rotation is the forward/backward movement on the horizontal plane which cannot be detected from the frontal view. It becomes an upward/downward movement from the submental view. Pitch rotation is movement on the sagittal plane that correlates with Angle’s classification in the anteroposterior direction. It does not contribute to facial asymmetry when

we inspect patients from the front. Therefore, we can ­classify facial asymmetry with the two rotational descriptors  –  roll and yaw  –  and the linear descriptor  –  sideshift – to describe the spatial orientation of the maxilla and mandible, respectively. After this sequential analysis, a 3D spatial orientation of the facial skeleton can be constructed (Table 57.1). The above mentioned clinical examinations can easily qualify the facial asymmetry systematically. To further quantify the asymmetry, we can get exact measurements of the bilateral difference by using 3D computed tomography.

57.4  ­Dentoalveolar Compensation A “dentoalveolar compensatory mechanism” is a system that attempts to maintain normal inter-arch relations under varying jaw relationships. We are familiar with the dental compensation of skeletal discrepancy on the sagittal plane; however, dental compensation for facial asymmetry is less discussed in the literature. In order to reach the ultimate treatment results, a comprehensive analysis of the correlation between the dental and skeletal portions should be established, irrespective of whether the therapy is surgical or non-surgical. In some clinical situations facial asymmetry is hardly noticeable, such as when normal occlusal function is still maintained in an asymmetric jaw base or the front teeth illustrate a harmonious smile. We can categorize these special clinical findings as dentoalveolar compensation for facial skeletal asymmetry.

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

(a)

(b)

(c)

Figure 57.2  An easy way to observe occlusal cant and facial asymmetry. (a) From front view facial photographs we can observe the relative position (coronal plane) of bilateral gonial angles and the chin button to identify the direction of roll rotation of the mandible. (b) With the addition of a retractor, it is much easier to detect the cant of a transverse occlusal plane and its relationship with the interpupillary line. (c) In submental view we can observe the relative position (on the horizontal plane) of bilateral gonial angles and mouth angles to identify the direction of yaw rotation of the maxilla and mandible. Table 57.1  Classification of facial asymmetry and its subsequent effects. Effect Mx/Md

Roll

Yaw

Facial asymmetry

+

+ a

Chin deviation

+

+/−

Dental characteristics

Uneven vertical position and/ or inclination of canine

Uneven molar relationship or canine angulation

Occlusal cant

+

−

Pitch

Side-shift

−

+

−

+ Uneven buccal overjet, maxillary posteriors tilt toward ipsilateral side and mandibular posteriors tilt toward contralateral side of mandible deviation

−

−

a

 It depends on the location of the rotation center of yaw. There will be more effects on the dental midline and chin position if the rotation center is located more posterior. In contrast, it will produce more bilateral differences of gonial angles if the rotation center is located more anterior.

57.4.1  Type 1: Mandible Deviation (Roll Rotation) with Maxillary Compensatory Cant This is the most common dental appearance in patients with facial asymmetry and is characterized by mandible roll rotation. This type of mandible deviation usually combines with the same direction of maxilla roll rotation [15] and/or

the compensatory vertical growth of dentoalveolar process in both jaws on the opposite side of the chin deviation (Figure 57.3). There is no straight facial midline but a curve which bends gradually to the side of the deviated chin. Occasionally, a transverse cant develops in the orbital/cranial portion and then the interpupillary line cannot be used

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Figure 57.3  These three patients all presented with chin deviation to the right. Compared with UR3, UL3 demonstrated more tooth display.

Figure 57.4  The patient’s mandible presented with a roll rotation to the right plus a maxillary compensatory cant (left-side down). But the axes of four maxillary incisors and UR3 were all parallel with the vertical line of the face. The incisal edges of the maxillary anterior teeth were coincident with the lower lip curvature. This caused her asymmetry to be almost unnoticeable.

as the reference for the horizontal plane. Therefore, it is important to determine the “natural head position” to identify the true vertical line [16, 17]. Then the asymmetry can be qualified and quantified according to this vertical line.

57.4.2  Type 2: Maxillary Incisors May Be Parallel to the Vertical Line in Asymmetrical Faces This is an illusion to mask the underlying skeletal problems (Figure 57.4). Usually not all of the six anterior teeth are coincident; one or two canines may present with a different inclination or angulation.

57.4.3  Type 3: Twisted Occlusal Plane There is no canting in the anterior part of the occlusal plane. The posterior part of the occlusal plane is curved upward on one side and downward on the other side (Figure 57.5). It is something like when you twist a towel to dry it. We call this type of occlusal plane a “twisted occlusal plane.” This particular condition can be found in some patients with symmetrical faces as well. It might be derived from the different eruption and placement of the posterior teeth. For example, the maxillary right and mandibular left first molars erupt earlier than their antagonists. Therefore,

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

(a)

(b)

Figure 57.5  “Twisted occlusal plane.” (a) The upper and lower archwires are almost parallel with each other from the frontal and lateral views in occlusion. (b) Both maxillary and mandibular occlusal planes are curved consistently in the same pattern when they are inspected from the front separately.

they are longer than their antagonists. The occlusal heights are even and a normal occlusal function is maintained. This type of occlusal cant is subclinical and usually overlooked by the patients themselves because their anterior teeth are level and their occlusal function is not impaired. Consequently, it is a normal situation and no further treatment is necessary in patients with symmetrical faces. Likewise, it can be regarded as a kind of dental compensation in patients with asymmetrical faces.

Categorizing different types of transverse occlusal cants and their associated dentoalveolar compensations can better identify which dental compensation should be maintained and hence aid in the selection of the most effective camouflage treatment modality. There are three types of transverse occlusal cants (Table 57.2). ●●

57.5  ­Camouflage Treatment Most facial asymmetries are too mild to be detected by patients themselves. Even with a higher degree of asymmetry, patients usually prefer conservative orthodontic treatment over orthognathic surgery. However, they still expect orthodontic treatment to improve their smile. Ideally, the skeletal problem should be solved by surgery. It is impossible to get a symmetrical face and well-aligned dentition without surgery in patients with asymmetrical jaws. The purpose of conservative non-surgical orthodontic treatment is not to correct the jaw problems but to create a harmonious smile and maintain a stable (not ideal) occlusion – the dental midline may not be coincident and the buccal overjet may not be even. When the anterior occlusal plane is leveled and parallel with the interpupillary line or perpendicular to the true vertical line, an optical illusion is created to mask the problem of facial asymmetry.

●●

●●

Type 1: The posterior segment is even while the anterior segment is canted. This is the simplest cant to treat because the posterior segment can be used as anchorage to level the canted anterior segment (Figure  57.6). It is sometimes caused by a difference in eruption and placement of the anterior teeth during facial growth and development. Type 2: Both anterior and posterior segments are canted. This can be regarded as a “normal” situation in facial asymmetry patients diagnosed with a roll rotation of both jaws – a canted occlusal plane in an asymmetrical jaw base. Type 3: The anterior segment is leveled, but posterior segment is canted. One should be very cautious when treating a malocclusion in patients having this type of facial asymmetry because an iatrogenic transverse occlusal cant might develop. The level anterior occlusal plane would be destroyed easily by a continuous archwire (Figure 57.7), and the occlusal cant would become worse if more asymmetric mechanics were to be applied. In contrast, this could be a possible solution for Type 2 occlusal cant. We can imitate the natural dental compensation “twisted occlusal plane” as an applicable solution to clinical situations: level the front teeth only while

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Table 57.2  Classification of transverse occlusal cant. Type 1

Anterior: Canted

Type 2

Posterior: Even

Anterior: Canted

Type 3

Posterior: Canted

Anterior: Even

Posterior: Canted

Type 1: Only anterior segment is canted. Type 2: Both anterior and posterior segments are canted. Type 3: Anterior segment is leveled but posterior segment is canted.

(a)

(b)

(c)

(d)

Figure 57.6  (a) Pre-treatment, the posterior segment could be used as anchorage to level the canted anterior segment with simple mechanics – stepwise changing of the archwires from 0.014-in CuNiTi to 0.016 × 0.025-in CuNiTi in five months (b to c), (d) Post-treatment.

Figure 57.7  Iatrogenic occlusal cant. The maxillary canines were at a different vertical height, inclination, and angulation. A light wire (0.014-in CuNiTi) makes the occlusal cant worse and more noticeable.

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

maintaining the posterior cant or at least do not expect to have a significant improvement. Most importantly, do not forget to inform the patient in advance. The aim of this camouflage treatment is to establish a harmonious smile, not a symmetrical face.

57.6  ­Clinical Applications of TADs There are three main concerns with the clinical application of TADs: implant site selection, design of the screw head, and the mechanics design (direct or indirect). For direct application, the force direction is limited to the screw site, whereas indirect application is more versatile. An extension arm or a cantilever spring can be connected to the screw head, hence the point of application and force direction can be applied precisely. This allows the miniscrews to be placed near incisors, premolars, or molars without restriction. It all depends on the specific clinical situation and the mechanics design (Figures 57.8–57.11).

57.7  ­Clinical Considerations 57.7.1  Pure Roll Rotation This is the most noticeable type of facial asymmetry and is manifest as a prominent chin deviation combined with transverse occlusal plane canting. It is not always limited to

(a)

(b)

only one or both jaws; the orbital portion (cranial base) can be affected as well. Under this circumstance, the facial midline will not be a straight line but a curve from the top down. When evaluating this type of patient, first find out what the “natural head position” is. The difficulty in treating this type of asymmetry is that the correction in one plane often leads to a new asymmetry in another plane. We can correct it vertically, but this will cause a worse problem in the transverse and anteroposterior directions. For non-surgical treatment, some dentoalveolar compensations should be maintained due to the true jaw discrepancy (Figures 57.12–57.15; Case 57.1).

57.7.2  Roll and Yaw Rotation This type of facial asymmetry often goes unnoticed by the orthodontist and patient. The patient’s face is not asymmetrical nor is there a prominent chin deviation when they are viewed just from the front, and usually their intraoral findings do not support their “normal” facial appearance. With a 3D analysis of the dentofacial traits using these logical classifications, we can reconnect the real relationship between the intraoral findings and the facial appearance. Roll rotation of the mandible can be diagnosed by the uneven gonial angles and transverse occlusal cant from the frontal view. The yaw rotation can be diagnosed from the submental view. Eventually, the deviated chin produced by a roll rotation of mandible will swing back to the center because of the further yaw rotation. That is why the real

(c)

Figure 57.8  (a) A miniscrew (Quattro, 2.0 × 9 mm, square slot 0.018 × 0.025-in; Mondeal) was inserted vertically in the molar area. The intrusive force was delivered by a 0.017 × 0.025-in TMA cantilever spring. A pure intrusive force could be created through this indirect application design. (b) Before intrusion, a right-side down occlusal cant was noted. (c) After intrusion, the incisors were even bilaterally and the interocclusal gap in the premolar area represented the amount of maxillary premolar intrusion.

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(a)

(b)

(c)

Figure 57.9  (a) A miniscrew (SH2018-08, AbsoAnchor®; Dentos Inc., Daegu, South Korea) was inserted horizontally in the premolar area. A 0.013-in CuNiTi was applied to connect between the hole in the screw head and the auxiliary horizontal slot in the brackets (Damon Q; Ormco, Glendora, CA, USA). An intrusive force was delivered. It was determined by the flexibility of the wire and direction of screw hole. (b) Before intrusion. (c) After intrusion. The direction of screw hole could be adjusted to apply more intrusive force if necessary.

(a)

(b)

(c)

Figure 57.10  (a) Two miniscrews (SH1615-06, AbsoAnchor) were inserted beside UL3 in the interradicular areas. An elastomeric chain was applied directly from the miniscrews to the UL3 and UL4. (b) Before intrusion. (c) After intrusion. In this direct application design, a lateral force component was delivered as well. This “side-effect” helped to solve the problem of the buccal overjet deficiency. Conversely, the miniscrew could be inserted on the palatal side if more palatal force component is needed.

(a)

(b)

(c)

Figure 57.11  (a) Before intrusion. Both the maxillary and mandibular occlusal planes were canted because UL3 ankylosis and improper mechanics. (b) The transverse occlusal cant was diagnosed as an insufficient display of the maxillary left dentition. A single miniscrew (SH1615-06, AbsoAnchor) was inserted between LL2 and LL3 to intrude the mandibular left dentition by elastomeric chain. Then, extrude the maxillary left dentition subsequently by elastics. (c) After intrusion.

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

Figure 57.12  Case 57.1: Pre-treatment records. Angle Class I malocclusion with a high mandibular plane angle. Significant chin deviation to the right. Patient’s facial asymmetry was diagnosed as a mandible roll rotation to the right with a maxillary compensatory cant.

(a)

(b)

(c)

Figure 57.13  Case 57.1: Treatment progress. (a) A miniscrew (SH1615-06, AbsoAnchor) was inserted between UL5 and UL6 for intrusion and retraction of the maxillary left dentition directly by elastomeric chain. Then an elastic was applied to extrude and retract the mandibular left dentition indirectly. (b) An excessive buccal overjet was noted after the anterior occlusal plane (vertical) improved. (c) Dentoalveolar compensation should have been maintained in this type of facial asymmetry. An 0.019 × 0.025-in TMA in the maxillary arch to provide better torque control and an 0.016 × 0.025-in CuNiTi in the mandibular arch (the wire size was reduced in LL3 and LL4 area) to allow for the flaring of the mandibular dentition to reduce the excessive buccal overjet.

facial asymmetry is not very easily detectable. This type of  facial asymmetry has the best prognosis. If a skeletal ­discrepancy in the transverse and sagittal direction is not very severe, a harmonious smile and an acceptable stable occlusion can be established after the vertical problem (produced by roll rotation) is improved (Figures  57.16– 57.21; Case 57.2).

57.7.3  Side-shift Patients usually present with a prominent facial asymmetry and lateral chin deviation without any transverse occlusal cant. Because the pattern of the deviation is a lateral sideshift, the eyes, mouth angles, and gonial angles are all at the same level, respectively. Intraorally, the posterior dentition

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Figure 57.14  Case 57.1: Post-treatment records.

Figure 57.15  Case 57.1: Post-treatment occlusion. Twisted occlusal planes were the solution for facial asymmetry due to roll rotation.

Figure 57.16  Case 57.2: Pre-treatment records. He presented with severe mandibular anterior crowding and mild facial asymmetry.

(b)

(c)

(a)

Figure 57.17  Case 57.2: (a) Both the maxillary and mandibular arches presented with a transverse occlusal cant. (b) Frontal view. There was no prominent chin deviation but the gonial angles were not even: right side was higher than the left side on the coronal plane. The mandible had a roll rotation to the right. (c) Submental view. Both the mouth and gonial angles on the left side were more posterior on the horizontal plane. Both the maxilla and the mandible presented as a yaw rotation to the left. The chin was deviated to the right first because of the roll rotation of the mandible, then swung back toward the left because of the yaw rotation. Eventually, the chin was back in the center, therefore there was no significant chin deviation with this type of facial asymmetry.

Figure 57.18  Case 57.2: Asymmetric mechanics. This patient presented with a 4 mm dental midline deviation to the left and skewed arch form in the maxillary arch due to missing UL3 and UL4. There was only one tooth space left in the edentulous area. Therefore, the treatment plan was UR4 and LL4 extraction for midline correction and to alleviate crowding. The molar relationship will be finished in Class II on the right and Class I on the left.

Figure 57.19  Case 57.2: The transverse occlusal cant became more prominent after the initial leveling.

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(a)

(b)

(c) Figure 57.20  Case 57.2: Versatile application of TADs. An interradicular miniscrew (SH1615-06, AbsoAnchor) was inserted between LR3 and LR4. (a) Initial mandibular dentition intrusion. (b) Maxillary dentition extrusion and buccal movement with a cross elastic applied from the button on UR3 palatal side to the miniscrew on the buccal side.

Figure 57.21  Case 57.2: Post-treatment records. The facial traits did not change significantly, but a stable and well-aligned dentition was obtained.

has a different inclination (third order) while the anterior dentition presents with a different angulation (second order). Molar relationships would be equal on both sides if there was no yaw rotation or dental crowding. Only roll rotation will lead to transverse occlusal cant. This patient (Case 57.3) was diagnosed as having yaw rotation of the maxilla and side-shift of the mandible in the classification of facial asymmetry. Therefore, there was no occlusal cant in this type of facial asymmetry. It is not usually necessary to insert a miniscrew to apply a vertical force to treat this kind of problem. However, there are still other problems in the sagittal or  transverse direction to be solved because of the yaw ­rotation and side-shift deviation. The miniscrew will be efficient and effective to solve these problems, but the mechanics need to be designed carefully to avoid the ­vertical component. This vertical force may give rise to an iatrogenic transverse occlusal cant (Figures 57.22–57.25).

57.7.4  Functional Shift When mandible deviation is caused by a dental interference (i.e. when there is a functional shift), the deviated mandible can be repositioned to the center after elimination of the interference. Therefore, a test can be performed in the ­pre-treatment examination: instruct the patient to not bite in the posterior occlusion position (maximum intercuspation), and guide their mandible to the centered position and observe any changes in their facial appearance. If the asymmetry is improved, this might be a clue that non-surgical treatment will be successful. If there is some dental interference from a constricted maxilla or maxillary arch, maxillary arch expansion can be used to improve the facial asymmetry due to the mandible deviation. Sometimes with true mandibular asymmetry, a difference in shape and volume between the two sides exists even when there is a functional shift. The functional shift

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

Figure 57.22  Case 57.3: Pre-treatment records. Mandible was deviated to the right. (The gonial angles were even from the frontal and submental views.) Maxilla was presented with a yaw rotation to the left which could be recognized by the unequal anteroposterior position of canines and molars, and the mouth angle on the left side was more posterior.

(b)

(a)

Figure 57.23  Case 57.3: (a) UR4, UL4, LL4, and LR5 extraction. LR5 extraction was simply due to its deep caries, not for facial asymmetry. (b) Two miniscrews on the right side were used for anchorage in anteroposterior direction, not in vertical.

should not be considered a guarantee that non-surgical treatment will be successful. Under certain circumstances, the non-surgical treatment can offer mild improvement but not complete correction of an asymmetry. It is crucial to evaluate the true discrepancy of the bilateral bony components before treatment (Figures 57.26–57.30; Case 57.4).

57.8  ­Summary This classification of facial asymmetry can be applied to the other dental professions. For orthognathic surgery, as the asymmetry is 3D, the changes in vertical and transverse direction should be included as well. To qualify and quantify a

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Figure 57.24  Case 57.3: Post-treatment records. The protrusive lips were much improved. Problems on the sagittal plane were solved, but problems on the coronal plane remained.

Figure 57.25  Case 57.3: It is hard to establish an ideal occlusion with an asymmetric jaw base. We should put more emphasis on the maxillary dentition than the mandibular dentition in this camouflage treatment – having proper maxillary incisor angulation and symmetrical tooth display. The maxillary and mandibular dental midlines may be deviated, but the maxillary dental midline should be coincident with the facial midline, if possible.

facial asymmetry, it is crucial to identify how asymmetric jaw bones contribute to the condition and what the dentoalveolar compensation is. Therefore, pre-surgical orthodontic treatment planning should focus on the decompensation of dentoalveolar changes in vertical and transverse directions, not just in the sagittal dimension with which we are more ­familiar. The surgical results will be optimized only when all  ­dental compensation is eliminated before surgery. For ­prosthodontists, it is difficult to fabricate a set of esthetic anterior prosthetics in an asymmetric jaw. Besides, to create a harmonious smile arc or level the anterior occlusal plane, it is challenging to maintain a balanced occlusal function when there are different conditions bilaterally.

Using this new classification system, clinicians will be able to make a differential diagnosis of facial asymmetry, to know the relationship between the transverse occlusal cant and the facial asymmetry, and to identify the problem in an easy and systematic way. Moreover, this 3D classification system facilitates choosing an effective treatment and feasible treatment modality that address different types of occlusal cants. The easiest prognosis is the roll and yaw type, while the most challenging prognosis is the pure roll rotation type. For severe skeletal discrepancies, orthognathic surgery is still the best option. Keep in mind that the aim of this camouflage treatment is to harmonize, not normalize.

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

Figure 57.26  Case 57.4: Pre-treatment records. A 20-year old girl complained of crooked front teeth. Chin deviation was not her main concern. Therefore, the surgical option was refused in the initial consultation. From the facial examination, a prominent facial asymmetry with a left side deviated chin and mild protrusive lips were noted. Intraoral findings: There was a 4 mm dental midline discrepancy, mild crowding, and a single tooth (UL3) crossbite.

(a)

(b)

Figure 57.27  Case 57.4: (a) Lateral deviation of the mandible was noted. Side-shift to the left, no roll and yaw rotation because the mouth angles and gonial angles were on the same level as the coronal and horizontal planes. (b) When the patient bites on the dental midline coincidental position, the mandibular asymmetry would become undetectable. The functional shift could predict success with non-surgical treatment. The asymmetrical facial appearance may improve after the dental interference is eliminated.

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(a)

(b)

Figure 57.28  Case 57.4: (a) UR4, UL5, LR4, and LL4 extraction. (b) Asymmetric mechanics were applied to provide more lateral force components to correct the transverse discrepancy and deviated mandible during the different stages of treatment.

(a)

(b)

Figure 57.29  Case 57.4: In the later stage of treatment. (a) Dental midline discrepancy and mandible deviation were not corrected completely due to a true skeletal asymmetry of the mandible. (b) Chin deviation was improved when the mandible was guided to the dental midline coincident position. A large buccal overjet and different inclinations of the maxillary and mandible posterior teeth were noted. That was the dentoalveolar compensation of the mandible deviation. It could not be corrected without surgery. With this camouflage orthodontic treatment, the dental compensation should be maintained.

Chapter 57  Facial Asymmetry: Non-surgical Orthodontic Treatment

Figure 57.30  Case 57.4: Post-treatment records. Although the deviated mandible was not corrected completely, an improved face and stable occlusion were obtained.

­References 1 Lu SM, Bartlett SP. On facial asymmetry and selfperception. Plast Reconstr Surg. 2014;133:873e–881e. 2 Thiesen G, Gribel BF, Freitas MPM. Facial asymmetry: a current review. Dental Press J Orthod. 2015;20:110–125. 3 Smith RJ, Bailit HL. Prevalence and etiology of asymmetries in occlusion. Angle Orthod. 1979;49:199–204. 4 Ackerman JL, Proffit WR. Soft tissue limitations in orthodontics: treatment planning guidelines. Angle Orthod. 1997;67:327–336. 5 Peck S, Peck L, Kataja M. Skeletal asymmetry in esthetically pleasing faces. Angle Orthod. 1991;61:43–48. 6 Chia MS, Naini FB, Gill DS. The etiology, diagnosis and management of mandibular asymmetry. Ortho Update. 2008;1:44–52. 7 Cheong YW, Lo LJ. Facial asymmetry: etiology, evaluation, and management. Chang Gung Med J. 2011;34:341–351. 8 Bishara SE, Burkey PS, Kharouf JG. Dental and facial asymmetries: a review. Angle Orthod. 1994;64:89–98. 9 Hwang H. A new classification of facial asymmetry. In: McNamara J, ed. Early Orthodontic treatment: Is the Benefit Worth the Burden? Craniofacial Growth Series 44. Ann Arbor, MI: University of Michigan, 2007, pp. 269–294.

10 Obwegeser HL, Makek MS. Hemimandibular hyperplasia: hemimandibular elongation. J Maxillofac Surg. 1986;14:183–208. 11 Chen YJ, Yao CC, Chang ZC, et al. A new classification of mandibular asymmetry and evaluation of surgicalorthodontic treatment outcomes in class III malocclusion. J Craniomaxillofac Surg. 2016;44:676–683. 12 Kim JY, Jung HD, Jung YS, et al. A simple classification of facial asymmetry by TML system. J Craniomaxillofac Surg. 2014;42:313–320. 13 Ackerman JL, Proffit WR. The characteristics of malocclusion: a modern approach to classification and diagnosis. Am J Orthod. 1969;56:443–454. 14 Ackerman JL, Proffit WR, Sarver DM, et al. Pitch, roll and yaw: describing the spatial orientation of dentofacial traits. Am J Orthod Dentofacial Orthop. 2007;131:305–310. 15 Padwa BL, Kaiser MO, Kaban LB. Occlusal cant in the frontal plane as a reflection of facial asymmetry. J Oral Maxillofac Surg. 1997;55:811–816; discussion 817. 16 Lundstrom A, Lundstrom F, Lebret LM, Moorrees CF. Natural head position and natural head orientation: basic considerations in cephalometric analysis and research. Eur J Orthod. 1995;17:111–120. 17 Uşümez S,Orhan M. Reproducibility of natural head position measured with an inclinometer. Am J Orthod Dentofacial Orthop. 2003;123:451–454.

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58 The Application of TADs for Gummy Smile Correction Kee-Joon Lee Department of Orthodontics, Institute of Craniofacial Deformity, Yonsei University College of Dentistry, Seoul, South Korea

58.1 ­Introduction/Etiology of Gummy Smiles The achievement of desirable smile esthetics is one of the major goals of clinical orthodontics. Smile esthetics can be assessed using multiple diagnostic factors both in the static and dynamic phases of smile, such as incisor display, gingival display, smile curve (arc), and the number of teeth displayed [1]. Considering the dynamic nature of a smile, an esthetic smile is largely dependent upon the relationship between the position of the incisors and the activity of the perioral muscles [2, 3]. In particular, an excessive display of gingival tissue on smiling (i.e. “gummy smile”) is often regarded as esthetically unattractive [4]. Underlying skeletal and/or dental vertical problems have been associated with excessive gingival display [5, 6]. Pure gingival problems including gingival swelling may also contribute to an unesthetic smile (Figure 58.1). In addition, activity of the lip elevator muscles must also be considered. Due to the inherently large variation of muscle activity from one individual to the next, diagnosis must be made based on a comprehensive understanding of the smile dynamics and soft tissue behavior.

58.2 ­Dynamics of a Smile 58.2.1  Static Smile: Maxillary Incisor Exposure, Lip Competency at Rest At rest, lips should be reposed with a relaxed shape. Excessive incisal exposure below the lower border of the upper lip implies relative vertical discrepancy between the dentoalveolar portion and upper lip [7]. In addition, the amount of vertical separation between the upper and lower lips (i.e. freeway space of the lips at rest) indicates a radical

vertical discrepancy between the underlying hard tissue and overlying soft tissue, and is clinically manifested as lip incompetency (Figure  58.2) [8]. Patients displaying lip incompetency tend to show hyperactivity of the perioral muscles, such as the orbicularis oris and mentalis, to repose the lips [9, 10]. Physical interference between the tip of the maxillary incisor and the lower lip may cause an unnatural lip profile at rest. Therefore, diagnostic findings must be used to determine proper tooth movement.

58.2.2  Dynamics of a Smile: Consideration of the Lip Elevator Muscles Three major lip elevator muscles – levator labii superioris alaeque nasii (LLSAN), levator labii superioris (LLS), and zygomaticus minor (Zmi) – determine the vertical level of lip line on smiling [11, 12]. In fact, hyperactivity of the muscles may be regarded as a separate entity apart from the hard tissue issue. However, vertical discrepancy when the lips are at rest may lead to exaggerated gingival display with smiling. Therefore, the dynamics of a smile and the causative factors must be integrated into the diagnosis of smile esthetics. To summarize, the following diagnostic features associated with vertical activation are considered important: (i) exposure of the maxillary incisors at rest, (ii) exposure of the incisors and gingival tissue with smiling, (iii) freeway space at rest, and (iv) interference between the maxillary incisor(s) and lower lip. Based on those factors, clinical signs may be categorized and defined as follows.

58.3 ­Treatment Modalities Orthodontic tooth movement is expected to induce remodeling of alveolar bone and subsequent soft tissue changes.

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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(a)

(b)

(c)

Figure 58.1  Evaluation of smile esthetics. (a) Esthetic smile with consonant smile arc. (b) Consonant smile arc with generally excessive gingival display. (c) Reversed smile arc with normal gingival display.

(a)

(b)

58.3.1  Gummy Smile due to Pure Muscle Hyperactivity A gummy smile due to pure muscular activity is seen as normal incisal exposure at rest but excessive gingival display with smiling. An active intrusion of the incisors might produce an aging image by decreasing the incisal display at rest. In cases of pure hyperactivity of the lip elevator muscles without further incompetency issues, reduction of muscle activity would be a potential solution. We have proposed a single injection point, the “Yonsei point,” in our previous study for effective botulinum toxin type A (Botox) injection [11]. This point is located at around 10 mm lateral to the alar base and 30 mm above the commissure of the lip.

Figure 58.2  Smile esthetics. (a) Interference between maxillary incisors and lower lip. (b) Vertical incompetency with lips at rest.

58.3.2  Gummy Smile due to Anterior Dentoalveolar Excess

In contrast to the extensive available information on the soft tissue changes in response to the anteroposterior movement of hard tissue, the vertical changes of the soft tissue have hardly gained any orthodontic attention, presumably because there is limited tooth movement in the vertical direction. Hence, an orthognathic surgical intervention has been suggested for excessive gingival display and/or soft tissue incompetency in spite of its high morbidity, risk, and cost [6, 13]. Recent findings in finite element studies have revealed interesting points with regard to vertical correction. The following categorization of vertical problems related to gummy smile may help the clinician when designing tooth movement plans.

Excessive incisal exposure at rest is associated with gummy smile. This type of gummy smile is often accompanied by deep bite and/or interference between the tip of the maxillary incisor(s) and lower lip. If the gummy smile is not accompanied by a major vertical lip incompetency, active intrusion of incisors may be indicated [14].

58.3.3  Gummy Smile due to Vertical Skeletal Excess with Reverse Smile Arc An excessive gingival display combined with vertical lip incompetency calls for major vertical correction, including a reduction of the anterior facial height. For this

Case 58.1  A 25-year-old woman presented with a gummy smile. She had normal incisor display and did not show any incompetency with her lips at rest, but presented excessive gingival display only when smiling. Based on her smile dynamics, hyperactivity of the lip elevator muscles

was considered to be a main etiologic factor for her gingival display. A single dose of Botox (three units) was injected at her “Yonsei point.” Subsequently, 2–3 mm reduction of the gingival display was noted three weeks later (Figure 58.3).

Chapter 58  The Application of TADs for Gummy Smile Correction

(a)

(b)

Alar line

(c)

Lip line

Figure 58.3  Case 58.1: Application of Botox for gummy smile [11]. (a) Yonsei point. (b) Before injection. (c) Three weeks after injection. Source: Hwang et al. [11]. Reprinted with permission from E. H. Angle Education and Research Foundation

r­ eason, orthognathic surgical procedures such as maxillary Le Fort I down fracture and superior relocation of the maxilla used to be the options of choice [15]. However, the latest research findings and clinical outcome studies suggest it might be better to use alternative treatment options such as total arch intrusion to replace the surgical intervention [15–17].

58.4 ­Biomechanics For the correction of a gummy smile, an intrusive movement of the anterior and/or posterior segments is strongly indicated. The following mechanics should be considered.

58.4.1  Conventional Intrusive Mechanics For active intrusion of the anterior segment, the posterior segment was conventionally used for anchorage. However, an overlay intrusion wire tied to the anterior segment exerts extrusive force at the first molar. These mechanics, in turn, flatten the smile arc, so a reversed smile arc may result. Therefore, this type of reciprocal action should be avoided (Figure 58.4) [18].

58.4.2  Intrusion with Miniscrews Miniscrew-type temporary anchorage devices (TADs) can effectively eliminate unwanted movement of the anchorage segment. Nonetheless, the insertion site must be carefully selected since the resultant tooth movement largely depends upon the applied force system [19]. Recent finite element analyses have localized the estimated centers of resistance of anterior segments in the maxilla and mandible, for intrusion of four and six anterior teeth, respectively [20, 21]. Because of the inclination and the location of the roots within the alveolar bone, the center of resistance was localized on the distal side of the crowns of the target segment. Relative to this, another finite element study claimed the insertion site for the anterior segment should be on the distal side of the canine, to achieve pure intrusion along the incisal axis without tipping to either side [22]. According to this, miniscrews located on the distal side of a canine may serve as a reliable point of force application. This contrasts to others suggested miniscrew insertion sites between the two central incisors [23], which in reality is likely to cause unwanted labial flaring of the incisors rather than pure intrusion along the axis (Figures  58.5 and 58.6) [24].

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Figure 58.4  Conventional intrusion arch.

(2a)

(2b)

(2c)

(2d)

(2e)

(2f)

(2a)

(2b)

(2c)

(2d)

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(2f)

Figure 58.5  Finite element analysis for pure intrusion of incisor segment. Source: Park et al. [22]. Reprinted with permission from The Korean Association of Orthodontists.

Chapter 58  The Application of TADs for Gummy Smile Correction

(a) Cr(T)

Cr(A)

Cr(T)

Cr(A)

D

(b)

Figure 58.6  Force diagram for predictable intrusion. (a) Midline miniscrew causing excessive flaring of incisors. (b) Force vectors passing through the centers of resistance of total arch [Cr(T)] and anterior segment [Cr(A)], respectively. Source: Jeong et al. [21]. Reprinted with permission from The Korean Association of Orthodontists.

consonant smile arc with smiling are the clinical manifestations for this. An inherent short lip length may be associated with excessive gingival display with a full smile. In this case, intrusion of the anterior segment would lead to a reversed smile arc which would be esthetically displeasing. The conventional solution for this used to be surgical intervention, including a Le Fort I down fracture and superior relocation of the entire maxilla [17]. Fortunately, using the estimated centers of resistance of the respective maxillary and mandibular dentition, so-called “total arch intrusion” may produce an equivalent treatment outcome and reduction of the overall anterior facial height (Figure 58.6) [16, 20, 21]. Our finite element study also showed that the rotation of the overall occlusal plane is a function of the relationship between the line of force and center of resistance of the entire dental arch (Figure  58.7) [25]. Therefore, either single or dual miniscrews can be placed in the interradicular areas to intrude the whole arch in the oblique direction to resolve a radical incompetency (Figure 58.8).

58.4.3  Total Arch Intrusion

58.4.4  Incisor Control

An upward relocation of the entire maxillary basal bone may be indicated for maxillary vertical excess. Obvious lip incompetency at rest and excessive gingival display with a

If an oblique single linear force is approximated to the center of resistance of the entire dental arch, the distance between the line of force and the estimated center of resistance of the

6 5 4 3 2 1 1

7

8

9

Long lever arm: Labial flaring of incisors Extrusive distalization of molars Flattening rotation of occlusal plane

0.15

Rotation (°)

0.10 0.05 0.00 –0.05 –0.10 C1

C5

C4

C3

C2

C1

C7

C8

C9

Short (no) lever arm: Lingual tipping of incisors Intrusive distalization of molars Steepening rotation of occlusal plane

Figure 58.7  Finite element analysis showing rotation of the occlusal plane according to the direction of linear force. Source: Sung et al. [25]. Reprinted with permission from The Korean Association of Orthodontists.

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(a)

(b)

Cr(P)

Cr(T)

Cr(A)

Moment on wire

Cr(P)

Cr(T)

Moment on wire

Cr(A)

Moment on wire

Cr(P)

Cr(T)

Cr(A)

Figure 58.8  Appliance construction for total arch intrusion. Cr(A), Center of resistance of the anterior segment; Cr(P), center of resistance of the posterior segment; Cr(T), center of resistance of the total arch. (a) Single miniscrew position and force vectors. (b) Dual miniscrew positions and force vectors.

Case 58.2  A 33-year-old female presented with an excessive gummy smile. When smiling, her gingival exposure measured 5 mm and she had a deep 6 mm overbite, severe 7 mm overjet, relatively retrusive chin profile as well as a severe lip incompetency of 6 mm when her lips were relaxed. Considering her skeletal and soft tissue patterns, it was presumed that selective intrusion of her incisor or anterior segment might not be sufficient to effectively reduce the soft tissue incompetency. Therefore, the treatment plan included extraction of four premolars, retraction of maxillary and mandibular incisors and intrusion of both entire maxillary and mandibular dental arches to reduce her anterior facial height (Figure 58.9). Self-ligating ceramic brackets with an 0.018-in slot were bonded. Extraction of four second premolars instead of first premolars was performed due to an existing crown and history of root canal treatment. Nonetheless, maximum retraction was required to correct the excessive overjet. Following leveling and alignment, miniscrews were placed in the interradicular

spaces between her second premolar and first molar. An 0.016 × 0.022-in rectangular stainless steel straight wire with selective torque was used on four incisors at 10° as a working wire. Linear force vectors were established close to the estimated center of resistance of the respective maxillary and mandibular dental arches. Constant linear force was applied throughout the retraction phase. Adequate occlusal relationship was achieved and the incisal relationship was improved (Figure 58.10). Lateral cephalometric superimposition revealed significant intrusion of both anterior and posterior ­ segments, implying simultaneous total arch intrusion. ­ Subsequent forward and upward autorotation of the mandible was evident (Figure  58.11). Her gingival display was normalized possibly by massive retraction and intrusion of the maxillary incisors. The intentional displacement of the whole dentition in both arches supposedly contributed to the improvement of her profile by eliminating the lip incompetency and retracting the lips (Figure 58.9).

Chapter 58  The Application of TADs for Gummy Smile Correction

(a)

(b)

Figure 58.9  Case 58.2: Gummy smile with lip incompetency, facial view before (a) and after (b) treatment.

(a)

(b)

(c)

Figure 58.10  Case 58.2: Intraoral photographs. (a) Pre-treatment. (b) Progress. (c) Post-treatment.

(Continued )

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(a)

(b)

(c)

Figure 58.11  Case 58.2: Before (a) and after (b) treatment lateral cephalograms and superimposition (c).

anterior segment increases accordingly, which in turn causes lingual tilting of the incisors during vertical control [26]. In order to overcome this dilemma, a balancing torque must be given to the incisor segment. With continuous arch mechanics, this counteracting moment can be exerted by incorporating selective torque on the wire. Hence, if an 0.016 × 0.022-in stainless steel wire is inserted in the 0.018-in slot bracket with 10° torque on four incisors, this might produce a moment that counteracts the lingual tipping of the incisors. A posterosuperior linear force in turn is expected to serve as an anchorage which prevents labial flaring and extrusion of the incisors (Figure 58.12) [27].

58.4.5  Gummy Smile During Active Growth – the Rationale for “Four-dimensional Total Arch Intrusion” It is always challenging to make a proper decision on treatment timing, especially when vertical dimension is

(a)

(b)

Figure 58.12  Force diagram for incisor control during total arch intrusion. (a) Horizontal force vector. (b) Oblique vertical force vector which produces greater moment of force causing lingual tipping of the incisors.

Case 58.3  A 23-year-old female complained of her upper anterior crowding and excessive gingival display when smiling. She had severe retrusion of her chin and linguoversion of her incisors. In addition, she was missing her maxillary left first premolar. Based on this, she was diagnosed as skeletal Class II Division 2 with gummy smile. In spite of the severe linguoversion of her maxillary incisors, she believed that she had protrusive lips, possibly due to the

retrusive chin. Significant lip incompetency of around 4 mm was included in the problem list. Therefore, a somewhat unique combination of retroclined maxillary incisors with protrusive lips needed to be corrected at the same time. Because she did not want surgical intervention, a non-surgical treatment was sought (Figure 58.13). Critical issues in this case included major retraction of incisors, precise correction of incisor axis by major

Chapter 58  The Application of TADs for Gummy Smile Correction

(a)

(b)

Figure 58.13  Case 58.3: Gummy smile with retrusive chin, linguoversion of maxillary right lateral incisor, and facial view before (a) and after (b) treatment.

root movement, and vertical correction by total arch intrusion to alleviate the lip incompetency and gummy smile. Following leveling and alignment using 0.018-in slot self-ligating brackets, an 0.016 × 0.022-in rectangular stainless steel archwire was used with selective torque on the four incisors. The treatment was combined with four interradicular miniscrews between the canine and the second premolar, and between the second premolar and the first molar, respectively. A pair of oblique vertical forces were applied from the miniscrews to the hooks attached on the archwire distal to the canines and a constant intrusive force was applied (Figure 58.14).

Lateral cephalometric superimposition showed remarkable retraction of the incisors in the form of root movement, presented as a greater amount of root apex displacement than displacement of incisal edge. Simultaneous intrusion of both anterior and posterior segments resulted in an upward relocation of the mandible and contributed to the elimination of the lip incompetency and improvement of the patient’s convex profile and retrusive chin (Figure 58.15). This excessive gingival display was relieved without having an adverse effect on the smile arc. Consequently, the patient’s post-treatment smile was improved and there was a consonant smile arc (Figure 58.13). (Continued )

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(a)

(b)

(c)

Figure 58.14  Case 58.3: Intraoral photographs. (a) Pre-treatment. (b) Progress. (c) Post-treatment.

(a)

(b)

(c)

Figure 58.15  Case 58.3: Before (a) and after (b) treatment lateral cephalograms and superimposition (c).

involved because the vertical dimension is largely dependent upon genetic regulation [28]. However, now that the average growth “direction” has been recognized as forward and downward along the estimated “Y” axis, the previously introduced “total arch intrusion” methods may be

applied to growing children as well [29]. For instance, a child in the active growth phase showing excessive gingival display is regarded as having severe vertical discrepancy between the hard and soft tissue. Instead of surgical intervention, a single oblique upward and backward force

Chapter 58  The Application of TADs for Gummy Smile Correction

vector applied to each quadrant may effectively restrict vertical growth of the dentoalveolar area. Meanwhile, a normal lengthening of the lips may occur during growth. A combination of these two conditions, a relatively large vertical discrepancy including a gummy smile and/or lip incompetency can be resolved. Specifically, relative suppression of vertical dentoalveolar growth within the basal bone can change the growth direction. The attempt to do this is referred to as “four-dimensional total arch intrusion,” since the dentoalveolar changes takes place over time during active growth. Unlike adult cases, redirecting growth should exert a synergistic effect on the facial profile and extraction of premolars can be replaced by a nonextraction treatment modality.

58.5 ­Summary In terms of smile esthetics, it is crucial to qualify the essential factors of an esthetic smile. Conventional intrusive mechanics tend to produce side effects since extrusion of a particular segment is unavoidable. In order to maintain or improve the smile arc and to reduce gingival display, an intrusive movement of the total arch must be considered. Up-to-date biomechanical findings suggest a reliable and predictable total arch intrusion based on the relationship between the linear force and the estimated center of resistance of the entire dental arch. This chapter has introduced the concepts of total arch intrusion in three dimensions (in adults) and in four dimensions (in children).

Case 58.4  A 12-year-old male presented with moderate protrusion of his lips. Upon clinical examination, he had moderate lip protrusion with mild crowding, but the freeway space with his lips at rest was as large as 8 mm. He complained of an unnatural lip profile when reposed. Therefore, the case was diagnosed as more severe vertical discrepancy than an anteroposterior one ­ (Figure  58.16). Active reduction of his vertical dimension was presumed to be crucial. Considering that he was still in active growth, a full strap-up was done using a set of 0.018-in slot brackets. Following alignment, rectangular stainless steel wires were engaged

(a)

and interradicular miniscrews were inserted in each quadrant. Constant linear forces were applied (Figure 58.17). After treatment, favorable occlusion was obtained. More importantly, the lip incompetency and gummy smile was mostly eliminated (Figure 58.16). Lateral cephalometric superimposition reveals the change of the mandibular growth. Unlike the average growth pattern, the menton point has been displaced upward and forward, and overall anterior facial height was reduced during the active growth phase, implying the obvious effect of total arch intrusion combined with active mandibular growth (Figure 58.18).

(b)

Figure 58.16  Case 58.4: An active grower showing gummy smile with severe incompetency. Facial view before (a) and after (b) treatment.

(Continued )

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(a)

(b)

(c)

Figure 58.17  Case 58.4: Intraoral photographs. (a) Pre-treatment. (b) Progress. (c) Post-treatment.

(a)

(b)

(c)

Figure 58.18  Case 58.4: Before (a) and after (b) treatment lateral cephalograms and superimposition (c).

Chapter 58  The Application of TADs for Gummy Smile Correction

­References 1 Sarver DM. The importance of incisor positioning in the esthetic smile: the smile arc. Am J Orthod Dentofacial Orthop. 2001;120:98–111. 2 Sarver DM, Ackerman MB. Dynamic smile visualization and quantification: part 1. Evolution of the concept and dynamic records for smile capture. Am J Orthod Dentofacial Orthop. 2003;124:4–12. 3 Sarver DM, Ackerman MB. Dynamic smile visualization and quantification: part 2. Smile analysis and treatment strategies. Am J Orthod Dentofacial Orthop. 2003;124:116–127. 4 Robbins JW. Differential diagnosis and treatment of excess gingival display. Pract Periodontics Aesthet Dent. 1999;11:265–272. 5 Casko JS, Eberle KM, Hoppens BJ. Treatment of a dental deep bite in a patient with vertical excess and excessive gingival display. Am J Orthod Dentofacial Orthop. 1989;96:1–7. 6 Fish LC, Wolford LM, Epker BN. Surgical-orthodontic correction of vertical maxillary excess. Am J Orthod. 1978;73:241–257. 7 Drummond S, Capelli J Jr. Incisor display during speech and smile: Age and gender correlations. Angle Orthod. 2016;86:631–637. 8 Miller H. Lip incompetency and its treatment. N Y State Dent J. 1972;38:210–216. 9 Yamaguchi K, Morimoto Y, Nanda RS, et al. Morphological differences in individuals with lip competence and incompetence based on electromyographic diagnosis. J Oral Rehabil. 2000;27:893–901. 10 Yoshizawa S, Ohtsuka M, Kaneko T, Iida J. Assessment of hypoxic lip training for lip incompetence by electromyographic analysis of the orbicularis oris muscle. Am J Orthod Dentofacial Orthop. 2018;154:797–802. 11 Hwang WS, Hur MS, Hu KS, et al. Surface anatomy of the lip elevator muscles for the treatment of gummy smile using botulinum toxin. Angle Orthod. 2009;79:70–77. 12 Polo M. Myotomy of the levator labii superioris muscle and lip repositioning: a combined approach for the correction of gummy smile. Plast Reconstr Surg. 2011;127:2121–2122. 13 Altug-Atac AT, Bolatoglu H, Memikoglu UT. Facial soft tissue profile following bimaxillary orthognathic surgery. Angle Orthod. 2008;78:50–57. 14 Shu R, Huang L, Bai D. Adult Class II Division 1 patient with severe gummy smile treated with temporary anchorage devices. Am J Orthod Dentofacial Orthop. 2011;140:97–105.

15 Fowler P. Orthodontics and orthognathic surgery in the combined treatment of an excessively “gummy smile.” N Z Dent J. 1999;95:53–54. 16 Bechtold TE, Kim JW, Choi TH, et al. Distalization pattern of the maxillary arch depending on the number of orthodontic miniscrews. Angle Orthod. 2013;83:266–273. 17 Sundararajan S, Parameswaran R, Vijayalakshmi D. Orthognathic surgical approach for management of skeletal Class II vertical malocclusion. Contemp Clin Dent. 2018;9:S173–S176. 18 Sifakakis I, Pandis N, Makou M, et al. Forces and moments on posterior teeth generated by incisor intrusion biomechanics. Orthod Craniofac Res. 2009;12:305–311. 19 Lee KJ, Park YC, Hwang CJ, et al. Displacement pattern of the maxillary arch depending on miniscrew position in sliding mechanics. Am J Orthod Dentofacial Orthop. 2011;140:224–232. 20 Jo AR, Mo SS, Lee KJ, et al. Finite-element analysis of the center of resistance of the mandibular dentition. Korean J Orthod. 2017;47:21–30. 21 Jeong GM, Sung SJ, Lee KJ, et al. Finite-element investigation of the center of resistance of the maxillary dentition. Korean J Orthod. 2009;39:83–94. 22 Park HK, Sung EH, Cho YS, et al. 3-D FEA on the intrusion of mandibular anterior segment using orthodontic miniscrews. Korean J Orthod. 2011;41:384–398. 23 Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod. 1997;31:763–767. 24 van Steenbergen E, Burstone CJ, Prahl-Andersen B, Aartman IH. Influence of buccal segment size on prevention of side effects from incisor intrusion. Am J Orthod Dentofacial Orthop. 2006;129:658–665. 25 Sung EH, Kim SJ, Chun YS, et al. Distalization pattern of whole maxillary dentition according to force application points. Korean J Orthod. 2015;45:20–28. 26 Smith RJ, Burstone CJ. Mechanics of tooth movement. Am J Orthod. 1984;85:294–307. 27 Kim SJ, Kim JW, Choi TH, Lee KJ. Combined use of miniscrews and continuous arch for intrusive root movement of incisors in Class II division 2 with gummy smile. Angle Orthod. 2014;84:910–918. 28 Hartsfield JK Jr. Developement of the vertical dimension: nature and nurture. Semin Orthod. 2002;8:113–119. 29 Linder-Aronson S, Woodside DG, Lundstrom A. Mandibular growth direction following adenoidectomy. Am J Orthod. 1986;89:273–284.

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59 Application of TADs in an Adult Gummy Smile Case with Vertical Maxillary Excess Johnny J.L. Liaw Orthodontic Division, Dental Department, National Taiwan University Hospital, Taipei, Taiwan

59.1 ­Introduction

59.3 ­Etiologies

A beautiful smile is one of the ultimate pursuits of orthodontic treatment. A consonant smile arc, ideally with proportionate tooth sizes and a harmonious gingival line are all requirements for a beautiful smile. However, excessive display of gingiva during a smile, also called a “gummy smile,” is considered a negative factor for esthetics. In the past, it was believed the only way to solve gummy smiles in adult patients was with orthognathic surgery. Nowadays, with the help of skeletal anchorage, also known as temporary anchorage devices (TADs), it is possible to correct gummy smiles in adult patients by using TADs and ­periodontal surgery [1–5].

Possible etiologies for gummy smiles [12–14] can be classified into three categories; dentogingival, skeletal and muscular.

59.2 ­Definitions The upper and lower lips frame the display of the smile. Within this framework, the components of a smile are the teeth and the gingival scaffold [6–8]. The lip lines during smiles have been classified as low, medium, and high. The lip line is low when no gum is shown during a smile. The lip line is medium when 1–3 mm of gum is visible during a smile, and the lip line is high when the gingival display is above 4 mm during a smile, which is also known as a gummy smile. Smiling with the teeth entirely displayed and some gingival display (2–4 mm) is considered most esthetic. Excessive gingival display more than 4 mm is judged as a negative factor for smile esthetics [9–11].

59.3.1 Dentogingival Gummy smiles of a dentogingival origin are the easiest conditions to correct. Super-eruption of maxillary anterior teeth can be intruded by orthodontic treatment. If attrition is noted at the incisal edges with super‐eruption, restorative treatment after braces is helpful to restore an appropriate crown length‐to‐width ratio. If the teeth are too short because they are submerged into the soft tissue, periodontal surgeries such as crown lengthening or gingivectomy are indicated to restore an appropriate crown length.

59.3.2 Skeletal Gummy smiles of a skeletal origin that are due to vertical maxillary excess, so‐called “long face syndrome,” usually require orthognathic surgery to correct. Le Fort I impaction is the standard of care for long face syndrome. If the patient does not accept the surgical modality, TADs can be used to intrude the entire maxillary arch to mimic the treatment results of orthognathic surgery.

59.3.3 Muscular Gummy smiles of a muscular origin may be related to short upper lip length or hypermobility of the upper lip

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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during a full smile. Botulinum toxin type A (Botox) injection has been suggested for gummy smiles due to a hypermobility of the upper lip. However, the treatment effects of Botox last for only six months so repeated injections may be necessary. For a more long‐lasting effect, myotomy of the upper lip elevator muscle might be considered. An implant spacer can reduce the possibility of muscle reattachment.

59.4 ­Differential Diagnosis and Treatment Options As the treatment options and prognosis for various types of gummy smiles are different, depending on the etiology, careful differential diagnosis [13, 15] is very important for gummy smile treatment. First, the clinical diagnosis of a gummy smile is confirmed when the amount of gingival display at a full smile is more than 4 mm. Ask the patient to relax their lips and observe the amount of incisor shown at lip rest. If it is more than 4 mm, the position of the maxillary incisors might be either too forward or too inferior in comparison to the ideal position of maxillary incisors. There is an excess of hard tissues which cannot be well covered by the soft tissues. Possible diagnoses include vertical maxillary excess, maxillary dentoalveolar protrusion, maxillary incisor super‐ eruption and short upper lip length. ●●

●●

●●

●●

Maxillary dentoalveolar protrusion: Lip incompetence, convex profile, mentalis strain, and lip protrusion are the most common clinical manifestations worsened by a retruded chin [1]. Maxillary incisor super‐eruption: Large overjet, deep overbite, and step‐typed occlusal plane are indicators of super‐eruption of the upper incisors [16, 17]. Vertical maxillary excess: Also known as “long face syndrome,” this features an increased vertical proportion of the lower facial third, and a ratio of upper anterior facial height to lower anterior facial height less than 45–55% [18]. Short upper lip length: A gummy smile is caused by insufficient lip frame coverage, which is beyond the scope of orthodontic treatment, although there might be some improvement after extractions and retraction. The extent of improvement depends on the amount of retraction and severity of the discrepancy [19].

With a fixed amount of lip separation during a full smile, the shorter the clinical crowns are, the more gingiva will show. A differential diagnoses related to the length of clinical crowns may include the following.

●●

●●

Short clinical crowns with incisal wear and subsequent super‐eruption: Orthodontic intrusion, composite restorations, and a crown lengthening procedure would be indicated to correct the gummy smile [20]. Altered passive eruption or gingival hyperplasia: This manifests as short clinical crowns without incisal wear [20, 21]. An altered passive eruption occurs when the ginigiva does not physiologically recede following active tooth eruption. Periodontal surgery might help to lengthen the clinical crowns and reduce gummy smile. The causes of gingival hyperplasia, if any, need to be removed to maintain the correction.

If all the above are quite normal, another possible factor might be the soft tissue frame of the smile moving upward too much: ●●

Hypermobility of the upper lip: If the upper lip moves upward too much during a smile, treatment should be focused on the elevator muscles of the upper lip. The use of Botox has been suggested to decrease the amount of upper lip elevation. However, the treatment may last for only six months. For a more long‐lasting effect, myotomy of the upper lip elevator muscles or a lip repositioning procedure might be considered [22–27].

The treatment modality for gummy smiles should be chosen according to the specific diagnosis. The treatment options for gummy smile include extractions and retraction in protrusion cases, orthognathic surgery for vertical maxillary excess, orthodontic intrusion of maxillary incisors and periodontal surgeries for gummy smiles of dentogingival origin, and Botox injection, myotomy, or lip repositioning for gummy smiles of muscular origin.

59.5 ­Prognosis The prognosis for treatment of gummy smiles of a dentogingival origin is the best among the various etiologies. Gummy smiles of a skeletal origin require orthognathic surgery for total correction. The treatment effects of orthognathic surgery are predictable and the prognosis is good. As for gummy smiles of an upper lip hypermobility, it depends on a patient’s willingness to receive repeated injections of Botox. A short upper lip length might be the situation with the most limited prognosis. Even though extractions and retraction help to descend the upper lip, the amount would be limited and the effects on the facial profile need to be considered carefully.

Chapter 59  Application of TADs in an Adult Gummy Smile Case

Case 59.1  History and Clinical Examination A 39-year-old female patient visited the clinic with the chief complaints of protrusive facial profile and a severe gummy smile. Orthognathic surgery combined with orthodontic treatment were suggested because the severity of her protrusion and gummy smile were beyond the scope of orthodontic treatment alone. However, the patient declined the surgical approach, asking for orthodontic treatment alone with the understanding that the treatment results would be compromised. A possible periodontal surgery for crown lengthening and alveoloplasty was also mentioned because a large amount of incisor intrusion and retraction would be necessary for

profile improvement and gummy smile correction. Finally, rhinoplasty and chin augmentation were suggested as something she might consider after orthodontic treatment. Diagnosis Clinical examination showed severe lip protrusions, gummy smile, mentalis strain, and a retrognathic chin. The patient’s frontal view showed a long face with an increased lower third. Intraoral examination revealed bilateral Class I molar and canine relationships. Her overjet was 3 mm and her overbite was 3.5 mm (Figure  59.1a). A panoramic radiograph showed

(a)

Figure 59.1  Case 59.1: (a) Pre-treatment photographs of the patient showed severe protrusion and gummy smile with moderate crowding in the mandibular arch. (b) Pre-treatment panoramic radiograph showed two metal crowns on mandibular second molars. Endodontic fillings were noted at upper right central incisor and two lower second molars. Pre-treatment lateral cephalogram revealed skeletal Class II pattern wtih steep mandibular plane and bimaxillary protrusion.

(Continued )

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Figure 59.1  (Continued)

­ ndodontic fillings in her maxillary right central incie sor and mandibular second molars. There were metal crowns on the mandibular second molars. She also had a mandibular right third molar. Lateral cephalometric analysis showed a severe skeletal Class II relationship with a high mandibular plane angle (ANB, 12.0°; SN-MP, 49.3°). Maxillary incisors were upright and mandbular incisors were proclined (U1-SN, 88.6°, L1-MP, 100.6°), which were typical dental compensations to Class II skeletal relationship. The patient’s diagnosis was skeletal Class II pattern, a bimaxillary dentoalveolar protrusion with a retruded chin (Figure  59.1b and Table 59.1).

Table 59.1  Case 59.1: Cephalometric measurements.

Treatment Plan

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; Wits, distance between perpendiculars drawn from point A and point B onto the occlusal plane; SN‐MP, sella‐nasion plane to mandibular plane; U1‐SN, long axis of maxillary central incisor to sella‐nasion plane; L1‐MP, long axis of mandibular central incisor to mandibular plane; UL‐E, distance between upper lip anterior point and E line (esthetic plane of Ricketts; line that passes through the tip of the nose and soft tissue pogonion); LL‐E, distance between lower lip anterior point and E line.

Orthognathic surgery combined with orthodontic treatment was suggested as the ideal treatment modality. However, the patient would not accept the surgical approach and asked for just orthodontic treatment. After a thorough discussion with an understanding that only compromised treatment results would be achieved without orthognathic surgery, the treatment plan was settled as extraction of four premolars and a third molar. Posterior TADs would be used for maximal retraction, and anterior TADs would be used for anterior intrusion to correct her gummy smile. Periodontal surgery would be needed following orthodontic treatment to remove the exostosis after a massive amount

Norm

Pre-treatment

Post-treatment

SNA (°)

82.0

87.3

83.1

SNB (°)

80.0

75.3

76.7

ANB (°)

2.0

12.0

6.4

Wits (mm)

0.0

5.6

−1.6

SN‐MP (°)

32.0

49.3

45.3

U1‐SN (°)

104.0

88.6

97.2

L1‐MP (°)

90.0

100.6

85.3

UL‐E (mm)

−4.0

12.5

6.0

LL‐E (mm)

−2.0

7.6

4.1

of incisor retraction, to restore the appropriate crown length after a large amount of incisor intrusion, and to reduce the amount of gingival display during a full smile.

Chapter 59  Application of TADs in an Adult Gummy Smile Case

Treatment Progress Orthodontic appliances (Alexander Mini-Wick; 0.018-in slot in six anterior teeth and 0.022-in slot in posterior teeth) were placed with 0.016-in nickel–titanium (NiTi) archwires for leveling. Upper posterior TADs (2.0 mm in diameter, 10 mm in length, Bio-Ray A1; Syntec Scientific Corp., Taipei, Taiwan) were placed bilaterally at the infrazygomatic crests two weeks after initial bonding. The archwires were changed sequentially to 0.016 × 0.022-in stainless steel on both arches in the third month of treatment, and anterior TADs (1.4 × 7 mm, Bio-Ray A1) were inserted between her maxillary central and lateral incisors bilaterally and between her mandibular central incisors for overbite control and gummy smile correction (Figure  59.2). Space closure was started in the fifth month of treatment. Four months later, the molar relationships became Class III because of skeletal anchorage on the maxillary arch and reciprocal space closure on the mandibular arch. Lower posterior TADs were installed on her bilateral buccal shelves to reinforce the mandibular arch anchorage in the ninth month of treatment (Figure 59.3). Anterior intrusion on both arches was continued until the 16th month of treatment. Her anterior open bite was noted. The only contacts at this time were on the molars. Another buccal TAD, distal to the maxillary second molar, and a palatal TAD between her maxillary first and second molars were installed bilaterally in the 16th month for

posterior intrusion to facilitate counterclockwise rotation of her mandible (Figure  59.4a). Her anterior open bite was closed in the 24th month. Although all the extraction spaces were closed, total arch distalization was attempted on both arches with the posterior TADs because there was insufficient improvement to her facial profile (Figure 59.4b). The mandibular archwire was changed to 0.017 × 0.025-in TMA for final detailing in the 28th month. Bilateral Class I dental interdigitations were achieved in the 37th month (Figure  59.4c). Up-and-down elastics were prescribed for better interdigitations. All the appliances were removed after 45 months of active treatment. Treatment Results There was a lot of improvement in the patient’s facial profile after orthodontic treatment, but it was still protrusive with a retruded chin. Her mentalis strain was much relieved. Although her gummy smile was reduced at debonding, it was further refined after periodontal surgery. Both dentitions were well aligned with complete space closure. Her occlusions were Class I relationships with very good interdigitations. However, her lips were still protrusive and her chin still looked retruded (Figure  59.5a). Her root parallelism was acceptable on the panoramic radiograph. No obvious root resorption was noted, even though the roots of her molars were

Figure 59.2  Case 59.1: Both upper and lower anterior TADs were installed in the fourth month of treatment in order to control the overbite and reduce the gummy smile by intruding the maxillary incisors. Upper anterior miniscrews were installed interradicularly between maxillary central and lateral incisors bilaterally with the open method. A lower anterior miniscrew was inserted between two mandibular central incisors subapically with the close method. An extended hook was attached to the lower anterior miniscrew an intrusive force could be applied with a segment of elastic chain.

(Continued )

651

Figure 59.3  Case 59.1: The combined intrusion and retraction force system was used on both arches. The resultant force vector tended to move the maxillary occlusal plane upward and mandibular occlusal plane downward, which helped to rotate the mandible counterclockwise and reduce the lower anterior facial height. One of the upper anterior miniscrews (upper right) failed. It was reinserted in the interradicular space between the two maxillary central incisors.

(a)

Figure 59.4  Case 59.1: (a) Space closure was nearly completed in the 16th month. Open bite and Class III molar relationships were noted. Another buccal miniscrew was installed distal to the terminal molar and a palatal miniscrew was installed between the first and second molars to intrude the maxillary molars. (b) The anterior open bite was closed in the 24th month. Posterior TADs were used for further retraction on both arches. (c) Bony exostosis became obvious after a massive amount of incisor intrusion and retraction. The dental relationships were corrected to Class I in the 37th month of treatment.

Chapter 59  Application of TADs in an Adult Gummy Smile Case

(b)

(c)

Figure 59.4  (Continued)

(Continued )

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Section IV  Esthetic Control with TADs

clearly intruded into the sinus space (Figure  59.5b). Cephalometric superimpositions showed 6.5 mm of maxillary incisor retraction and 6 mm of incisor intrusion; 2.5 mm of maxillary molar mesial movement and 5 mm of maxillary molar intrusion; 7.5 mm of mandibular incisor retraction and 2 mm of mandibular incisor intrusion; 1 mm of mandibular molar mesialization and 2.5 mm of mandibular molar intrusion. Her mandibular plane angle was reduced by 4° from 49.3° to 45.3°, which shifted her chin point forward by 5.5 mm and upward by 6.5 mm. It also revealed good vertical control and an obvious reduction of lip protrusion (Figure 59.6 and Table 59.1). A comparison of the overjet views showed the severity of exostosis after treatment, so the patient was then referred to a periodontist for periodontal surgery to

remove the exostosis and restore the appropriate crown length (Figure 59.7a,b). Follow-up records at 25 months after treatment showed stable occlusion (Figure 59.8). A comparison of pre-treatment and post-treatment periapical radiographs of her maxillary incisors revealed acceptable root resorption. Cone-beam computed tomography (CBCT) images were further checked to examine the degree of root resorption. Root blunting was noted over four maxillary incisors (Figure  59.9). Progressive photographs at rest and with a smile showed stable correction of the gummy smile. Although the patient was satisfied with the compromised treatment results, progressive records of her profile view showed very slow and limited improvement (Figure 59.10).

(a)

Figure 59.5  Case 59.1: (a) Post-treatment facial photographs showed more relaxed and balanced lips with great improvement. The excessive gingival display was totally corrected during a full smile. Post-treatment intraoral photographs showed Class I dental relationships and good interdigitations. Exostosis appeared to be very severe. (b) Post-treatment lateral cephalogram revealed good vertical control and a reduction in lip protrusion. However, the lips remained protrusive and the chin still looked retruded. Post-treatment panoramic radiograph showed that root parallelism was good. No major root resorption was noted.

Chapter 59  Application of TADs in an Adult Gummy Smile Case

Figure 59.5  (Continued)

Figure 59.6  Case 59.1: Cephalometric superimposition showed an upward movement of maxillary occlusal plane and a downward movement of mandibular occlusal plane. Consequently, a counterclockwise rotation of mandible was noted. Pre-treatment (black); post-treatment (red).

(Continued )

655

(a)

(b)

Figure 59.7  Case 59.1: (a) Obvious exostosis was noted after incisor retraction. (b) Periodontal surgery was performed to remove the exostosis and restore the appropriate crown length.

Figure 59.8  Case 59.1: Intraoral records showed stable occlusion 25 months after treatment.

UR3

UR2

UR1

UL3

UL2

UL1

(c)

(a)

(b)

Figure 59.9  Case 59.1: Comparisons between (a) pre-treatment and (b) post-treatment periapical radiographs of maxillary incisors revealed a mild degree of root resorption within normal limits. (c) CBCT images were further checked to examine the degree of root resorption. Root blunting was noted over four maxillary incisors.

(a)

Figure 59.10  Case 59.1: (a) Progressive records of extraoral frontal photographs at rest and with a smile showed stable correction of the gummy smile. From left to right: pre-treatment, post-treatment, five months post-treatment, and 25 months post-treatment. (b) Progressive records of extraoral lateral profile view showed very slow and limited improvement from upper left to lower right: pre-treatment, 9, 21, 26, 31 months into treatment, post-treatment, 5 and 25 months post-treatment.

(Continued )

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Section IV  Esthetic Control with TADs

(b)

Figure 59.10  (Continued)

59.6 ­Discussion: Interdisciplinary Approach to Gummy Smile Treatment Patients with gummy smiles of skeletal origin are usually informed that orthognathic surgery is necessary to correct their gummy smiles. However, many patients reject surgery but still want to improve the gummy smiles without orthognathic surgery. Orthodontists are pushed to expand the envelope of orthodontic treatment with the advent of skeletal anchorage devices. Here in this chapter, Case 59.1 demonstrates the possibility of total maxillary arch intrusion with TADs to correct gummy smiles in adult patients with vertical maxillary excess. Although the treatment results were compromised in terms of facial profile, the gummy smile was corrected by orthodontic intrusion of the entire maxillary arch to mimic Le Fort I impaction to some extent. An interdisciplinary approach combined intrusion and retraction of the maxillary incisors, and periodontal surgery was proposed to correct the gummy smile. The rationale for

this treatment approach was to move the maxillary incisors and the overlying gingiva upward to hide the gingival margin behind the upper lip. Murakami et al. examined the periodontal changes after experimentally inducing intrusion of the maxillary incisors in Macaca fuscata monkeys [28], and found that the gingiva moved in the same direction as the teeth that were intruded, but only about 60% as far. The clinical crown shortened, and the gingival sulcus deepened. Shortening of the crown and deepening of the sulcus were both approximately 40% as much as the tooth intrusion. There was no inflammation or swelling microscopically in the gingiva of both the experimental animals and the controls. The epithelium was always attached in the cementoenamel junction (CEJ), even when the teeth were intruded. Following intrusion of the maxillary incisors, upward movement of the gingival line will help to correct the gummy smile, and periodontal surgery will further ­contribute to the correction of gummy smile by solving the shortening of the clinical crowns. Clinical crown lengthening is defined as a surgical procedure that aims to expose

Chapter 59  Application of TADs in an Adult Gummy Smile Case

sound tooth structure for restorative purposes via apical repositioning of the gingival tissue with or without removal of alveolar bone. Majzoub et al. reviewed the indications of the crown lengthening procedure, highlighting the biologic basis for the crown lengthening procedure, and the orthodontic contribution to crown lengthening in a multidisciplinary approach [29]. The maxillary anterior teeth should be moved to ideal positions relative to the lower lip, which is considered as the smile arc. Next, the crown lengths and crown width were examined to consider whether the length ratios of the maxillary anterior teeth were suitable for esthetic improvement by the crown lengthening procedure. The distance from the CEJ to alveolar bone crest should be around 3 mm. The alveolar bone crest should be scalloped harmoniously to rebuild an esthetic gingival line with proportional crowns during a full smile. For the orthodontic correction of gummy smiles, maximal retraction of the maxillary incisors is as important as intrusion of maxillary incisors. Jacobs discussed vertical lip changes related to maxillary incisor retraction [30]. It was found that the interlabial gap closes vertically at a ratio of approximately 1 mm for every 2 mm of horizontal retraction of the maxillary incisors if neither extrusion nor intrusion occurs during such retraction. With the applications of TADs for maximal retraction in protrusion cases, the amount of retraction was much more predictable with less

anchorage loss. Exostosis can be detected after massive amounts of incisor retraction, which was rarely possible before the advent of TADs. This might be due to less bone remodeling at sites more distant to the site of tooth movement. Hence, the more the incisors are retracted, the more obvious the exostosis will appear. However, it varies with the pre-treatment alveolar bone morphology, texture, and metabolic rate. The exostosis can be removed surgically at the same time as the periodontal flap surgery, together with the crown lengthening procedure.

­59.7  Conclusions Orthodontic treatment of gummy smiles without orthognathic surgery in adult patients is very challenging for orthodontists. With the application of anterior TADs for incisor intrusion and posterior TADs for maximal retraction and active vertical control, it is possible to attain acceptable treatment results, depending on the severity of the skeletal discrepancies. Interdisciplinary approaches, including periodontal surgery, are critical for restoring the appropriate incisor crown length and further resolving gummy smiles. Thorough communication among specialists and patients is one of the keys to the overall success of camouflage treatment for adult gummy smiles with vertical maxillary excess.

­References 1 Kaku M, Kojima S, Sumi H, et al. Gummy smile and facial profile correction using miniscrew anchorage. Angle Orthod. 2012;82:170–177. 2 Kim TW, Kim H, Lee SJ. Correction of deep overbite and gummy smile by using a mini‐implant with a segmented wire in a growing Class II Division 2 patient. Am J Orthod Dentofacial Orthop. 2006;130:676–685. 3 Lin JC, Liou EJ, Bowman SJ. Simultaneous reduction in vertical dimension and gummy smile using miniscrew anchorage. J Clin Orthod. 2010;44:157–170. 4 Shu R, Huang L, Bai D. Adult Class II Division 1 patient with severe gummy smile treated with temporary anchorage devices. Am J Orthod Dentofacial Orthop. 2011;140:97–105. 5 Wang XD, Zhang JN, Liu DW, et al. Nonsurgical correction using miniscrew‐assisted vertical control of a severe high angle with mandibular retrusion and gummy smile in an adult. Am J Orthod Dentofacial Orthop. 2017;151:978–988. 6 Al‐Johany SS, Alqahtani AS, Alqahtani FY, Alzahrani AH. Evaluation of different esthetic smile criteria. Int J Prosthodont. 2011;24:64–70.

7 Gilmore SL. Smile design and esthetic treatment planning. J Colo Dent Assoc. 1997;76:20–23. 8 Tjan AH, Miller GD, The JG. Some esthetic factors in a smile. J Prosthet Dent. 1984;51:24–28. 9 Pithon MM, Santos AM, Viana de Andrade AC, et al. Perception of the esthetic impact of gingival smile on laypersons, dental professionals, and dental students. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013;115:448–454. 10 Sadrhaghighi AH, Zarghami A, Sadrhaghighi S, et al. Esthetic preferences of laypersons of different cultures and races with regard to smile attractiveness. Indian J Dent Res. 2017;28:156–161. 11 Sadrhaghighi H, Zarghami A, Sadrhaghighi S, Eskandarinezhad M. Esthetic perception of smile components by orthodontists, general dentists, dental students, artists, and laypersons. J Invest Clin Dent. 2017;8. 12 Gummy smile. Plast Reconstr Surg. 1984;73:697–698. 13 Levine RA, McGuire M. The diagnosis and treatment of the gummy smile. Compend Contin Educ Dent. 1997;18:757–762, 764; quiz 766.

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1 4 Livada R, Shiloah J. Gummy smile: could it be genetic? Hereditary gingival fibromatosis. J Mich Dent Assoc. 2012;94:40–43. 15 Monaco A, Streni O, Marci MC, et al. Gummy smile: clinical parameters useful for diagnosis and therapeutical approach. J Clin Pediatr Dent. 2004;29:19–25. 16 Li YY, Zhou YH, Lin JX. [Intruding upper incisors using mini‐screw anchorage in patients with gummy smile]. Zhonghua Kou Qiang Yi Xue Za Zhi. 2009;44:449–453. 17 Liu DW, Zhou YH, Li YY. [Gummy smile correction by intruding upper incisors with mini‐screw implant: an esthetic evaluation by the golden facial mask]. Zhonghua Kou Qiang Yi Xue Za Zhi. 2010;45:560–564. 18 Fowler P. Orthodontics and orthognathic surgery in the combined treatment of an excessively “gummy smile.” N Z Dent J. 1999;95:53–54. 19 Dilaver E, Uckan S. Effect of V‐Y plasty on lip lengthening and treatment of gummy smile. Int J Oral Maxillofac Surg. 2018;47:184–187. 20 Pavone AF, Ghassemian M, Verardi S. Gummy smile and short tooth syndrome – part 1: etiopathogenesis, classification, and diagnostic guidelines. Compend Contin Educ Dent. 2016;37:102–107; quiz 108–110. 21 Mahn DH. Elimination of a “gummy smile” with crown lengthening and lip repositioning. Compend Contin Educ Dent. 2016;37:52–55. 22 Hwang WS, Hur MS, Hu KS, et al. Surface anatomy of the lip elevator muscles for the treatment of gummy smile using botulinum toxin. Angle Orthod. 2009;79:70–77.

23 Polo M. Botulinum toxin type A (Botox) for the neuromuscular correction of excessive gingival display on smiling (gummy smile). Am J Orthod Dentofacial Orthop. 2008;133:195–203. 24 Sucupira E, Abramovitz A. A simplified method for smile enhancement: botulinum toxin injection for gummy smile. Plast Reconstr Surg. 2012;130:726–728. 25 Ishida LH, Ishida LC, Ishida J, et al. Myotomy of the levator labii superioris muscle and lip repositioning: a combined approach for the correction of gummy smile. Plast Reconstr Surg. 2010;126:1014–1019. 26 Polo M. Myotomy of the levator labii superioris muscle and lip repositioning: a combined approach for the correction of gummy smile. Plast Reconstr Surg. 2011;127:2121–2122; author reply 2123–2124. 27 Littuma GJS, de Souza HCM, Penarrieta GM, et al. Lip repositioning technique with smile elevator muscle containment – a novel cosmetic approach for gummy smile: case report. Compend Contin Educ Dent. 2017;38:e9–e12. 28 Murakami T, Yokota S, Takahama Y. Periodontal changes after experimentally induced intrusion of the upper incisors in Macaca fuscata monkeys. Am J Orthod Dentofacial Orthop. 1989;95:115–126. 29 Majzoub ZAK, Romanos A, Cordioli G. Crown lengthening procedures: A literature review. Semin Orthod. 2014;20:188–207. 30 Jacobs JD. Vertical lip changes from maxillary incisor retraction. Am J Orthod. 1978;74:396–404.

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60 Facial Esthetics-oriented Treatment Planning with Dental VTOs and TADs Sercan Akyalcin Department of Orthodontics, School of Dental Medicine, Tufts University, Boston, MA, USA

60.1 ­Introduction A thorough pre-treatment diagnosis should include a visualization of the effects of proposed mechanotherapy on the overall balance of the face. Holdaway, in a two-part article series [1, 2], cautioned about adverse facial changes induced by using diagnostic systems based on hard tissue measurements or reference lines alone. Most cephalometric analysis methods used in orthodontics cannot predict precise soft tissue change because they provide only 2D spatial relationships of the dentition and jaws with no specific information about the direction and amount of dental movements required within each arch quadrant. Ricketts [3, 4] signified the importance of changes induced by growth and development and suggested a step‐by‐step construction of a virtual treatment objective (VTO) prediction to forecast the combined results of tooth movement with cranial growth. Although some VTO methods [5, 6] have proven helpful in choosing the best treatment option based on the growth pattern of the individual, many of these methods consider the mandibular incisor position as the key component in their treatment forecast. However, as noted by Holdaway [1] and Wylie [7], satisfying the mandibular incisor position by strictly applying cephalometric principles does not guarantee the harmony or balance of the face. Therefore, some other VTO methods [1, 2, 8] utilize an estimation of optimum soft tissue drape and position the maxillary incisors first accordingly. By determining the maxillary incisor position first, the mandibular incisor can be placed relative to the maxillary incisors where lip support is deemed satisfactory. The major challenge with VTO, whether skeletal or soft‐ tissue‐oriented, is the predictability factor because there is a wide variation in hard and soft tissue growth as well as in response to mechanotherapy. Although we cannot expect

VTO predictions to completely match the final clinical outcomes, setting up treatment objectives should still be the cornerstone of mechanotherapy. Dental VTO, as introduced by McLaughlin and Bennett [9], provides detailed and specific information about the movement of maxillary and mandibular midlines, canines, and molars after the desired incisor positions have been established using cephalometric and clinical judgments. There is plenty of evidence that miniscrews are more effective in anchorage control than conventional anchorage reinforcement methods [10, 11]. Since the miniscrews can manage various needs of anchorage in each quadrant of the arch, they complement the use of dental VTO in facial esthetics‐oriented treatment planning. The aim of this chapter is to introduce the principles of dental VTO and to provide a rationale for strategic placement of miniscrews in each arch quadrant. Case demonstrations illustrate the step‐by‐step use of this philosophy in achieving the optimum facial and smile esthetics.

60.2 ­Facial Esthetics-oriented Treatment Planning Before starting an analysis, the orthodontist must determine the best possible incisor positions in order to achieve an optimum change in the patient’s profile (Figure 60.1).

60.2.1  Face/Maxillary Incisor Position When considering a patient’s chief concerns, the orthodontist should decide whether the upper lip is in a harmonious relationship with the rest of the face or not. If the upper lip position is esthetically pleasing, no change should be planned for the maxillary incisors. Treating a patient without any extractions in moderate to severe crowding

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

(a)

(b)

(c)

Figure 60.1  Pre-treatment (a) and post-treatment (b) records of an 11-year-old female patient who presented with a protrusive lip profile. Ultimate positions of the maxillary and mandibular incisors were determined with the dental VTO in this case. The VTO prediction required the extraction of four first premolars. Extraction spaces were managed with maximum anchorage in the maxillary, moderate anchorage in the mandibular arch. Vertical eruption of the molars was prevented throughout the space closure with intra-arch mechanics. Lateral cephalometric superimposition (c) showing significant changes to the profile due to achievement of treatment objectives and favorable growth.

Chapter 60  Facial Esthetics-oriented Treatment Planning

cases may change the anteroposterior position of the upper lip and cause an undesired fullness of the profile. If the upper lip position is not ideal at the beginning of treatment, what can be done with the maxillary incisors to achieve a better lip profile? The possible options are to advance/flare or retract/upright them. Arch length, vertical, horizontal, and other biological considerations, including the long‐term maintenance of the case, should also be determined at this point.

60.2.2  Mandibular Incisor Position Since ideal overjet and overbite are common goals of orthodontic treatment, the ultimate position of the mandibular incisors as dictated by the facial/maxillary incisor objectives should be evaluated using cephalometric, clinical, and radiographic evidence. For instance, advancing the mandibular incisor position more than 2 mm may not be a healthy treatment goal considering the periodontal sequelae and other long‐term concerns, but the orthodontist should also be mindful of the physiologic limit of incisor retraction by evaluating the mandibular symphysis anatomy. At this point, a decision should be made whether the goals for the mandibular incisors are realistically attainable with non‐surgical methods in Class II and Class III cases.

recorded according to the facial midline, indicating the direction that the midline is shifted.

60.3.2  Step II The second part involves a number of calculations of the amount of discrepancy that exists in the mandibular arch (Table 60.1b). The space needs in the mandibular arch and tooth movement necessary to address these needs are established first. Maxillary tooth movement is calculated accordingly. Please note that the discrepancy is divided into “3–3” and “7–7” columns. The rationale behind this approach is to identify the required movements of the canines to resolve the anterior discrepancy before any other decisions are made. Several steps are involved in the calculation of mandibular arch discrepancy. Crowding should be recorded as (−) and extra space should be recorded as (+) numbers: ●●

●●

60.3 ­The Dental VTO The dental VTO should be regarded as a static figure that is used to calculate the amount of tooth movement in each arch quadrant necessary to reach the treatment goals. It does not incorporate any changes resulting from growth. Differential growth of the jaws may contribute to the occlusal correction, and may affect the prediction of the dental movement. One should consider how much growth is expected during the expected treatment period and monitor the proposed tooth movement at each appointment in growing patients.

60.3.1  Step I The first part of the dental VTO involves defining the maxillary and mandibular dental midlines and molar relationships when the patient is biting in centric occlusion (Table 60.1a). Class I molar relationship should be recorded as “0.” Angle Class II relationship will be shown with an arrow pointing forward, whereas Angle Class III relationship will be demonstrated with a backward facing arrow for both the right and left sides, including the millimetric discrepancy on the upper portion of the chart. Maxillary and mandibular dental midline deviations should be

●●

●●

●●

Anterior crowding/spacing: The orthodontist should measure the discrepancy from canine to midline (3–3) on each side. This value should also be transferred to the 7–7 column because anterior crowding contributes to the total arch discrepancy. Crowding/spacing premolar/E: Next the discrepancy in the premolar/E space should be determined. If the D and Es are present, the orthodontist should be mindful of the size differences between the primary and permanent teeth. The size difference should be added to the “space gained” for each arch quadrant in Step III. This value should only be recorded for the 7–7 column since there are no premolars/primary molars in the 3–3 area. Crowding/spacing molars: The next step is to evaluate the crowding/spacing in the first and second molars. In most circumstances, this is best evaluated using a panoramic radiograph to determine if the second molars are tipped and/or blocked out. The anterior aspect of the ramus resorbs with growth and makes more room for the erupting second molars. However, in non‐growing patients, uprighting the second molars can be very difficult to achieve without adequate space. This value should also be recorded only in the 7–7 column. Curve of Spee: The space needed for leveling a deep curve of Spee is calculated in that 1 mm of space is needed to level every 2 mm of depth in the curve of Spee on each side of the dental arch. This will add to the space discrepancy as a (−) value. In some Class III and open bite cases, the clinician may choose to finish the case with a slightly deeper curve of Spee. For instance, if the clinician is planning to accentuate the curve of Spee at 1 mm, (+) 0.5 mm space will be gained on each side of the dental arch. Midline: Space required for midline correction should be recorded as a positive number on one side and a negative

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Table 60.1  Steps of dental VTO.

The Dental VTO R

L

(a) Step I Molar

Mandibular Arch Discrepancy (mm)

(b) Step II

Molar

Midline 3 to 3 R

7 to 7 R

L

L

Anterior Crowding/Spacing Crowding/Spacing Premolar/E Crowding/Spacing Molars Curve of Spee Midline Incisor Position Initial Discrepancy (mm) Treatment Options (mm) Stripping Expansion/Uprighting Uprighting Mandibular 6s Extraction Remaining Discrepancy (mm) R

L (space gained)

(space gained)

(space gained)

(space gained)

(c) Step III

Molar

●●

●●

Canine

Midline

Canine

number on the other side. If the mandibular dental midline is deviated 2 mm to the right, it needs to be moved 2 mm to the left. This will bring about 2 mm of space discrepancy for the left (−), and 2 mm of space gain for the right side (+). Incisor position: After careful analysis, a decision should be made to maintain, advance or retract the mandibular incisors as required by the facial objectives. While advancing the incisors are recorded as (+) values, retraction should be recorded as (−) numbers. According to Steiner [6], 2.5° of change in incisor inclination would be the equivalent of 1 mm space on both the left and right sides. For instance, if an orthodontist is uprighting the mandibular incisors by 5°, 2 mm of space would be needed on each side. Initial discrepancy: The initial arch length discrepancy is diagnosed for both the 3–3 and 7–7 columns separately.

Possible 3–3 treatment solutions include stripping, expansion/uprighting of the canines if they are tipped ­lingually and extraction of an incisor. Uprighting/­

Molar

distalizing the first molars is a difficult movement that will not help in solving the anterior discrepancy at all. Therefore, this box is disabled for the 3–3 column. Once a final number is reached for the remaining discrepancy in the 3–3 column, the amount of discrepancy will indicate how far the mandibular canines must move to fulfill the treatment objectives. Establishing the right and left side canine movement is critical because these numbers will determine whether extractions are needed. The solutions for a 7–7 discrepancy should be considered next. If there is a negative number remaining from the 3–3 discrepancy, decisions should be made about how to develop the space necessary for distal movement of the canines. In moderate to severe cases, the answer is usually premolar extractions. In order to satisfy the treatment goals, the target for the remaining discrepancy in the 7–7 column after calculation should either be zero or a plus number. A negative number means that the space discrepancy has not yet been resolved.

Chapter 60  Facial Esthetics-oriented Treatment Planning

60.3.3  Step III The last step of the VTO is the establishment of required tooth movement in the dental arch quadrants (Table 60.1c). It will be determined at this time where the midlines, canines and molars should go. The mandibular dental midline and remaining discrepancy for the canines should be filled first since the mandibular arch serves as the diagnostic template for the maxillary arch. If premolars are extracted to resolve an anterior discrepancy in the mandibular arch, the remaining (3–3) discrepancy should be subtracted from the size of the premolar which was removed from the respective mandibular arch quadrant. The size of the premolar is technically the space gained in that dental arch quadrant, and should be noted in the parentheses. The difference between the space gained and the remaining discrepancy should provide the amount of molar protraction needed to close the extraction space in the same quadrant. If there is crowding in the premolar area, the amount of crowding should be subtracted from the space gained by extracting a premolar. Conversely, E space and any interproximal reduction (IPR) planned from the mesial of the first molar to the distal of the canine should be added to the space gained. The mesial movement

of the molars should always be the difference between the amount of distal movement of the canines and the amount of space available as indicated in the parentheses. Establishing the canine vs. the molar movement in the mandibular arch is an excellent opportunity to plan the anchorage requirements such as placing miniscrews. Next, the movement of the maxillary teeth should be determined. At this point, we already know how much the mandibular molars will be moved. The maxillary molars should be moved according to targeted molar relationship. The maxillary canine movement should be calculated by subtracting the molar movement from the space available in that quadrant. If the case starts with a Class I molar relationship, and the molar objective is to finish in Class I position, then the maxillary molar will have to move the same amount of the mandibular molar. If the molar relationship is a 2 mm Class II, and the objective is to finish in Class I molar relationship and 3 mm mandibular molar protraction is planned, then the maxillary molar should be held with maximum anchorage since it can only move forward 1 mm. Accordingly, if a 7 mm tooth is extracted in the maxillary arch, the maxillary canine has to be retracted 6 mm to close the extraction space.

Case 60.1  Diagnosis A 21-year-old male presented with the chief complaints of lower lip protrusion and the lack of an esthetic smile. He presented with an increased anterior facial height, prognathic, and hyperdivergent mandible and lower lip protrusion. Dentally, he had Angle Class III molar and canine relationships with a mandibular dental midline shift to the left. He had moderate crowding in both the maxillary and mandibular dental arches and 2–3 mm negative overjet on both maxillary lateral incisors (Figure 60.2a). His cephalometric evaluation revealed an ANB of −1°, SN-GoGn of 38°, and an FMA of 30°. His mandibular incisors were upright (IMPA, 87°), and maxillary incisors (U1-SN, 113°) were proclined. U1-NA and L1-NB measurements showed that the anteroposterior positions of the maxillary and mandibular incisors were 10 and 7 mm, respectively. Lower lip protrusion as evaluated by the E-line was 3 mm. Objectives and Treatment Alternatives Upon cephalometric and clinical examination, it seemed that the position of his maxillary incisors caused a soft tissue problem, mainly in his lower lip area. First, a surgical plan was devised and presented to the patient. He rejected the surgical option.

For a better lower lip profile, some degree of uprighting of incisors was needed in the maxillary arch. Secondly, restoration of a harmonious smile arc relationship required relative extrusion of the maxillary incisors. In order to achieve these goals, the mandibular incisors had to be retracted. The lingual anatomy of the symphysis and the anteroposterior position of the mandibular incisors safely allowed for 2 mm retraction of the mandibular incisors. A  dental VTO was performed, and the resultant figure required four premolar extractions with two miniscrews in the maxillary left and mandibular right quadrants for minimum, and maximum anchorage, respectively (Table 60.2). It was planned to manage the maxillary right and mandibular left segments with no additional anchorage reinforcement and by reciprocal anchorage. Vertical control of the face required application of careful intra-arch mechanics with no intermaxillary elastics. Additionally, posterior bite turbos were planned for both the maxillary molars in the later stages of treatment to get their intrusive effects, and to aid with anterior crossbite correction. Treatment Progress The decision for premolar extractions was made based on the anchorage requirements for the dental quadrants. The maxillary second premolars, mandibular (Continued )

665

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Section IV  Esthetic Control with TADs

(a)

(b)

Figure 60.2  Case 60.1: Pre-treatment (a) and post-treatment (b) records.

right first premolar, and mandibular left second ­premolar were extracted. Following removal of the premolars, an 0.016-in heat-activated nickel–titanium (HANT) wire was inserted with lacebacks for the initial alignment (Figure  60.3a). The maxillary lateral incisors and the mandibular incisors were bypassed. At the second appointment, buccal TADs (1.5 × 8 mm, The OrthoAnchor™ System; KLS Martin Group, Jacksonville, FL, USA) were placed between UL3 and UL4 to support the molar protraction, and between LR5 and LR6 to support the canine retraction. Canine and molar move-

ments were accomplished with 0.020-in stainless steel (SS) archwire by sliding mechanics. Following the ideal positioning of the canines, posterior bite turbos were placed and the remaining incisors were aligned with 0.016-in HANT with bend-backs to maintain the incisor position. Bite turbos inhibited the elongation of the molars. Miniscrews were removed when the desired canine and molar positions were achieved (Figure  60.3b). The case was detailed and finished with routine orthodontic procedures (Figure 60.3c).

Chapter 60  Facial Esthetics-oriented Treatment Planning

Table 60.2  VTO setup for Case 60.1: (a) Class III molar relationship with a midline shift of 1 mm. (b) Calculation of mandibular arch discrepancy. Premolar extractions were planned. (c) Calculation of canine and molar movements. CASE I

(a)

0

R 3 mm

2.5 mm L

1 mm Molar

(b)

(c)

Mandibular Arch Discrepancy (mm) Anterior Crowding/Spacing Crowding/Spacing Premolar/E Crowding/Spacing Molars Curve of Spee Midline Incisor Position Initial Discrepancy (mm) Treatment Options (mm) Stripping Expansion/Uprighting Uprighting Mandibular 6s Extraction Remaining Discrepancy (mm)

R

Molar

Midline

3 to 3 R –2.5

L –1.5

0 –1 –2 –5.5

0 1 –2 –2.5

0 0

0 0

0 –5.5

0 –2.5

(7 mm) –3 mm

4 mm

1 mm

–5.5 mm (6.5 mm)

Molar

Canine

0

1 mm Midline

7 to 7 R L –2.5 –1.5 –0.5 –0.5 0 0 0 0 1 –1 –2 –2 –6 –3 0 0 0 7 1

0 0 0 7 4

(7 mm) L –0.5 mm 6.5 mm

–2.5 mm 4 mm (6.5 mm) Canine

Molar

Note that due to premolar crowding, the space gained is 0.5 mm smaller than the premolar size, and is equal to 6.5 mm on both sides of the mandibular arch. Red dots represent where anchorage reinforcement by miniscrews are needed.

Treatment Results After 23 months of treatment, the patient showed a significant improvement in his lower lip and facial profile (Figure  60.2b). Lateral cephalometric superimposition demonstrated that the treatment objectives had been met. Molar and canine movement was achieved with precision by the asymmetric extraction pattern and addition

of miniscrews to support the anchorage in the specific quadrants as needed. Accordingly, the incisor objectives were met. The divergence of the mandible was slightly reduced due to the intrusive effects of the posterior bite turbos and the application of intra-arch mechanics with miniscrews, which did not permit any extrusion (Figure 60.4). (Continued )

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Section IV  Esthetic Control with TADs

(a)

(b)

(c)

Figure 60.3  Case 60.1: Case progress, initial leveling and aligning (a), releveling after removal of the miniscrews (b), and finishing and detailing (c).

Chapter 60  Facial Esthetics-oriented Treatment Planning

(a)

(b)

Figure 60.4  Case 60.1: Comparison of the facial profile change (a), lateral cephalometric superimposition (b).

Case 60.2  Diagnosis A 14-year-old female presented with the chief complaint of “upper teeth sticking out too much.” When asked, she indicated some discontent with her flattened smile arc but could not fully describe the problem. Dentally, she had end-on Angle Class II molar and canine relationships with a slight mandibular dental midline shift to the left. She had virtually no crowding, an overjet and overbite of 6 mm, and a 2 mm curve of Spee (Figure 60.5a). She presented with an ANB of 3° with a normal maxilla and mandible. Her Class II molar relationship seemed to be more of a dental nature. Her cephalometric assessment revealed a SN-GoGn of 37°, and an FMA of

27°. Her ­mandibular incisors were normally inclined (IMPA, 95°), and maxillary incisors (U1-SN, 114°) were proclined, causing upper lip protrusion. U1-NA and L1-NB measurements showed that the anteroposterior position of the maxillary and mandibular incisors were 8 and 5 mm, respectively. Lower lip protrusion as evaluated by the E-line was −1 mm.

Objectives and Treatment Alternatives Interactions with the patient and the clinical judgment suggested that maxillary incisors had to be retracted to normalize the upper lip position, to achieve normal overjet, (Continued )

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Section IV  Esthetic Control with TADs

(a)

(b)

Figure 60.5  Case 60.2: Pre-treatment (a) and post-treatment (b) records.

and to restore a harmonious incisor–lower lip relationship. Minimal inclination change was desired in the mandibular incisor position as they were properly positioned and were centered in alveolar bone. Extraction of the maxillary first premolars was considered to be the primary treatment plan, but the patient refused the extractions. As an alternative option, molar distalization with miniscrew anchorage was recommended.

A detailed dental VTO was performed, and the resultant figure required 3.5 mm and 2 mm distal movement of the maxillary right and maxillary left first molars, respectively (Table  60.3). Accordingly, a substantial amount of anchorage was needed to maintain the molar position after distalization. Since there was limited potential for further growth, vertical control was also critical in the management of the case.

Chapter 60  Facial Esthetics-oriented Treatment Planning

Table 60.3  VTO setup for Case 60.2: (a) Class II molar relationship with a midline shift of 1 mm. (b) Mandibular arch discrepancy calculation. Interproximal reduction was planned to offset the discrepancy. (c) Calculation of canine and molar movements.

CASE II (a)

0

R 3.5 mm

3.5 mm L

1 mm Molar

(b)

(c)

Molar

Midline

Mandibular Arch Discrepancy (mm) Anterior Crowding/Spacing Crowding/Spacing Premolar/E Crowding/Spacing Molars Curve of Spee Midline Incisor Position Initial Discrepancy (mm) Treatment Options (mm) Stripping Expansion/Uprighting Uprighting Mandibular 6s Extraction Remaining Discrepancy (mm)

3 to 3

7 to 7

R 0

L 0

–1 –1 0 –2

–1 1 0 0

1 0

1 0

0 –1

0 1

R 0 0 0 –1 –1 0 –2

L 0 0 0 –1 1 0 0

2 0 0 0 0

1 0 0 0 1

R

L –3.5 mm

0

–3.5 mm

0

–2.5 mm

–1 mm

1 mm

1 mm

Canine

Midline

Canine

–2.5 mm

1 mm

(1 mm) Molar

Molar

Note that because of the non-extraction approach in the mandibular arch, either extraction of maxillary premolars or distalization of molars were needed. Red dots represent where anchorage reinforcement by miniscrews are needed. In this instance miniscrews were initially used to distalize the molars, and then hold them in all planes for anterior retraction.

Treatment Progress A single miniscrew was placed 1 mm paramedian to the midpalatal suture between the U5s and U6s (1.7 × 8 mm, OrthoEasy, Forestadent, Pforzheim, Germany). A miniscrew-supported transpalatal arch (TPA) design was placed to hold the U4s in anteroposterior, transverse, and vertical planes. Maxillary posterior quadrants were then aligned to eventually accommodate a 0.017 × 0.025-in SS archwire. Nickel titanium open coil springs with 2 mm incremental activations were placed at each visit

between the maxillary first premolars and first molars on each side (Figure 60.6a). The maxillary second premolar was not bonded to increase the elasticity of the coil. Bodily molar distalization was achieved in six months. Once distalization was complete, another TPA was designed from the same miniscrew to hold the maxillary 6s in all planes (Figure 60.6b). The rest of the maxillary teeth were bonded, and maxillary canine and premolars were retracted with maximum anchorage by sliding mechanics on 0.020-in SS archwire. Incisor retraction (Continued )

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Section IV  Esthetic Control with TADs

(a)

(b)

(c)

Figure 60.6  Case 60.2: Distalization with 0.017 × 0.025-in SS sectional wires (a), maximum anchorage design (b), incisor retraction on 0.019 × 0.025-in SS archwires and the addition of fixed coil spring for midline correction (c).

Chapter 60  Facial Esthetics-oriented Treatment Planning

was carried out by active tie-backs on 0.019 × 0.025-in posted SS archwires (Figure 60.6c). In the meantime, IPR was performed in the mandibular arch, and a fixed Class II spring was used for midline correction. Treatment Results The case was completed in 20 months. Significant improvement was achieved in the upper lip position. Overjet correction and retraction of the maxillary ­incisors

resulted with a better smile arc relationship (Figure  60.5b). Lateral cephalometric superimposition demonstrated that the treatment objectives were met (Figure 60.7). Use of a single TAD in the maxilla assisted bodily distalization of the maxillary molars, maintenance of vertical and horizontal relationships of dentition and maximum anchorage when needed. The incisor objectives were met as the miniscrew-supported TPA was used with versatility.

Figure 60.7  Case 60.2: Comparison of the facial profile change (a), lateral cephalometric superimposition (b).

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Section IV  Esthetic Control with TADs

60.4 ­Conclusions Necessary dental movement as determined by the VTO can reliably be achieved using miniscrews. By placing the minis-

crews strategically to meet the challenging anchorage requirements of each dental quadrant, precise, predetermined dental movement can be assured, which will result in clinical success when restoring the balance of the profile and the smile.

R ­ eferences 1 Holdaway RA. A soft‐tissue cephalometric analysis and its use in orthodontic treatment planning. Part I. Am J Orthod. 1983;84:1–28. 2 Holdaway RA. A soft‐tissue cephalometric analysis and its use in orthodontic treatment planning. Part II. Am J Orthod. 1984;85:279–293. 3 Ricketts RM. Cephalometric synthesis: an exercise in stating objectives and planning treatment with tracings of the head roentgenogram. Am J Orthod. 1960;46:647–673. 4 Ricketts RM. Planning treatment on the basis of the facial pattern and an estimate of its growth. Angle Orthod. 1957;27:14–37. 5 Magness WB. The mini‐visualized treatment objective. Am J Orthod Dentofacial Orthop. 1987;91:361–374. 6 Steiner CC. Cephalometrics for you and me. Am J Orthod. 1953;39:729–755.

7 Wylie WL. The mandibular incisor: Its role in facial esthetics. Angle Orthod. 1955;25:32–41. 8 Jacobson A, Sadowsky PL. A visualized treatment objective. J Clin Orthod. 1980;14:554–571. 9 McLaughlin RP, Bennett JC. The dental VTO: an analysis of orthodontic tooth movement. J Clin Orthod. 1999;33:394–403. 10 Antoszewska‐Smith J, Sarul M, Łyczek J, et al. Effectiveness of orthodontic miniscrew implants in anchorage reinforcement during en‐masse retraction: A systematic review and meta‐analysis. Am J Orthod Dentofacial Orthop. 2017;151:440–455. 11 Alharbi F, Almuzian M, Bearn D. Anchorage effectiveness of orthodontic miniscrews compared to headgear and transpalatal arches: a systematic review and meta‐analysis. Acta Odontol Scand. 2018;77:1–11.

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61 Improved Facial Profile with Premolar Extraction and Molar Intrusion Using TADs and VTOs Kiyoshi Tai1,2 and Jae Hyun Park1,3 1

Postgraduate Orthodontic Program, Arizona School of Dentistry & Oral Health, A.T. Still University, Mesa, AZ, USA Private Practice, Okayama, Japan 3 Graduate School of Dentistry, Kyung Hee University, Seoul, South Korea 2

61.1 ­Introduction The virtual treatment objective (VTO) method is a computer‐assisted growth prognosis that takes into account patient growth during orthodontic treatment [1]. Along with video imaging, VTOs are regularly used for growing children and adolescents to obtain accurate predictions of potential changes to dentoskeletal relations and soft tissue profiles, as well as skeletal growth tendencies caused by orthodontic tooth movements. For both children and adults, the use of VTOs allows for the development of alternative treatment plans and to help patients get a better understanding of their proposed treatment and outcomes. In full‐grown adults, VTOs are even better tools since predicting treatment effects is easier without having to factor growth into the equation. In surgical cases, VTOs have been shown to provide accurate predictions of post‐surgical outcomes. This is important because the increased use of surgical methods for correcting dentofacial deformities has placed an increased demand on the planning skills of orthodontists and surgeons alike [2]. Video imaging can help patients gain a better understanding of their surgical options and allow them to make more informed treatment decisions [3]. In addition, as the esthetic awareness and concerns of adult patients has increased over time, it is now more likely that orthodontists will be required to discuss the potential facial and profile outcomes with their patients [4]. Therefore, VTOs are no longer limited to adults undergoing orthognathic treatment. VTOs can also be utilized for adult patients who are considering extractions and want to see how their profiles may be affected by the different treatment alternatives (Figures 61.1–61.3) [4, 5].

This case report demonstrates how VTOs and temporary skeletal anchorage devices (TADs) were used to treat a full‐ grown Class II female patient orthodontically and with premolar extraction.

61.2 ­Discussion In lieu of orthognathic surgery, four premolar extractions for full‐grown Class II patients may be a viable treatment plan, depending on the case. Extraction treatment involving four premolars has often centered around the claim that it might produce an unesthetic facial profile by flattening the lips in relation to the chin and nose [6]. However, previous studies have found that it is incorrect to blame undesirable facial esthetics after treatment solely on premolar extractions [7, 8]. It has been found that extraction treatment does not negatively impact soft tissue profile and esthetics over time, and that there are no significant differences in facial profiles with or without extraction treatment [9, 10]. Both extraction and non‐extraction treatments have no predictable effect on smile, which means that if well indicated, extraction treatment does not necessarily have harmful effects on facial esthetics [11]. In fact, in patients with greater lip protrusion and convex facial profiles, premolar extraction treatment tends to be more beneficial to soft tissue [10]. Bowman and Johnston [12] reported that the esthetic effects of extraction treatment is proportional to pre-treatment lip procumbency, and that extractions are beneficial when lips protrude more than 2–3 mm behind the E‐plane. However, it is important to note that the response of the soft tissue in Class II patients may differ

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section IV  Esthetic Control with TADs

(a)

(b)

(c)

Figure 61.1  VTOs: (a) Pre-treatment. (b) Four premolar extractions. (c) Advancement of the mandible after total arch distalization of the mandible and maxillary posterior tooth intrusion. Source: Tai and Park [5]. Reprinted with permission from Elsevier.

Dental movement Soft tissue movement

Pre-treatment Skeletal movement

Post-treatment

Figure 61.2  Cephalometric superimposition showing profile improvement: pre-treatment (black); post‐treatment (red). Blue arrows, dental movement; green arrow, skeletal movement; yellow arrow, soft tissue movement.

from one patient to the next depending on variations in soft tissue thickness, strain, and tonicity. Soft tissue profile changes in response to incisor retraction can be difficult to predict. The profile can also be affected by differences in lip thickness. Le et  al. [4] reported that the upper lip retracts about 40–60% of the distance that the maxillary incisors are retracted, while the lower lip retracts almost the same distance as the retraction of the mandibular incisors. The upper lip has been found to be more variable at the labrale superius with increased retraction of the maxillary incisors [13]. In addition, changes in thin lips tend to correspond more closely to hard tissue changes brought forth by maxillary incisor retraction, while thick lips do not always track with the tooth movement. In a profile change study on orthodontically treated patients 10 years post‐retention, the soft tissue changes tended to have a flattening effect in the dental area of the facial profile due to continuous growth of the nose and chin in maturing faces [13]. During treatment, upper lip thickness increased 1 mm for every 1.5 mm of maxillary incisor retraction, while the lower lip was not affected by treatment. During and after retention, it was found that the lip thickness decreased, though not back to its original thickness, with

Chapter 61  Improved Facial Profile with Premolar Extraction and Molar Intrusion

Before

After

Figure 61.3  Improvement of lip protrusion without extracting the premolars.

Case 61.1  Diagnosis and Etiology A 26‐year‐old female adult was referred for an orthodontic evaluation. Her chief complaint was crowding in her upper and lower arch. She had a mesiofacial, convex profile, and a retrognathic chin. Her temporomandibular joint (TMJ) evaluation showed no joint pain or symptoms associated with temporomandibular disease (TMD). Intraorally, the patient had a slight Class III end‐on molar relationship on both sides due to mesial inclination of the mandibular first molars. She had severe crowding in both arches. Her mandibular dental midline was deviated to the right side approximately 4 mm. Her mandibular anterior teeth were also tilted to the right side. She had 10% overbite and 1 mm overjet. In addition, she had anterior crossbite on her maxillary lateral incisors, and her maxillary first premolars also showed lingual crossbite. When her mandible was guided into centric relation, a functional shift was detected because of the anterior and posterior crossbite. A panoramic radiograph showed that her mandibular third molars were horizontally impacted and her maxillary left third molar had not emerged. She was also ­missing her maxillary right third molar. The lateral cephalometric measurement and analysis shows a skeletal Class II pattern (ANB, 5.9°), with a hyperdivergent growth pattern (SN‐MP, 54.4°). The maxillary incisors show retroclination (U1‐SN, 97.3°), while the mandibular incisors

show slight proclination (IMPA, 93.3°). Her upper and lower lips were protrusive to the E line (Figure  61.4; Table 61.1). Treatment Objectives The following treatment objectives were established for the patient: (i) correct the anterior and posterior crossbite, (ii) eliminate the functional shift, (iii) relieve the crowding in both arches, (iv) establish Class I molar relationships, (v) obtain normal overjet and overbite, (vi) improve dental midline deviation, (vii) obtain a stable occlusal relationship, and (viii) improve facial and dental esthetics by establishing an esthetic smile. The patient did not want orthognathic surgery, but was okay with undergoing premolar extractions to improve her facial profile that would result from a hyperdivergent skeletal Class II pattern. To address the facial profile caused by her Class II skeletal pattern and protrusive lips, the two maxillary first premolars would be extracted. To improve the hyperdivergent skeletal Class II pattern, two TADs would be placed to allow for maxillary molar intrusion and autorotation of the mandible. One concern was that a counterclockwise rotation of the mandible might lead to a possible negative overjet. Therefore, mandibular premolar extractions were included in the treatment to help establish an ideal overjet, Class I molar relationships, relieve crowding, correct (Continued )

677

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Section IV  Esthetic Control with TADs

Figure 61.4  Case 61.1: Pre-treatment photographs and radiographs.

dental midline, and improve profile. Details of this specific treatment plan were presented with VTOs, and the patient agreed to go with the treatment plan as described (Figure 61.5).

options except for premolar extractions. Because the patient was an adult and had already finished growing, few other treatment options were available. Treatment Progress

Treatment Alternatives An alternative treatment plan for this patient included orthognathic surgery along with genioplasty to address the skeletal discrepancies, but she declined surgical

After periodontal treatment, four first premolars were extracted. Full fixed preadjusted appliances with 0.022 × 0.028‐in slots were placed in both arches. After leveling and alignment to intrude the maxillary posterior

Chapter 61  Improved Facial Profile with Premolar Extraction and Molar Intrusion

Table 61.1  Case 61.1: Cephalometric measurements. Norm

Pre-treatment

Post-treatment

One year retention

SNA (°)

82.0

76.0

74.4

73.9

SNB (°)

80.0

70.1

70.8

70.5

ANB (°)

2.0

5.9

3.6

3.4

Wits (mm)

0.0

−0.2

−3.4

−2.9

SN‐MP (°)

32.0

54.4

51.8

52.0

FH‐MP (°)

25.0

43.4

40.7

41.2

LFH (ANS‐Me/N‐Me) (%)

55.0

60.5

59.7

59.6

U1‐SN (°)

104.0

97.3

93.2

92.3

U1‐NA (°)

22.0

21.3

18.8

18.4

IMPA (°)

90.0

93.3

86.3

84.6

L1‐NB (°)

25.0

37.9

28.9

27.7

U1/L1 (°)

124.0

115.0

128.7

130.5

Upper lip‐E line (mm)

1.2

4.1

0.2

−0.1

Lower lip‐E line (mm)

2.0

4.5

−0.5

0.2

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; Wits, distance between perpendiculars drawn from point A and point B onto the occlusal plane; SN‐MP, sella‐nasion line to mandibular plane; FH‐MP, FH plane to mandibular plane; LFH (ANS‐Me/N‐Me), ratio between anterior nasal spine‐menton and nasion‐menton; U1‐SN, long axis of maxillary central incisor to sella‐ nasion plane; U1‐NA, long axis of maxillary central incisor to nasion‐A point line; IMPA, incisor mandibular plane angle; L1‐NB, long axis of mandibular incisor to nasion‐B point line; U1/L1 (interincisal angle), angle formed by long axes of maxillary to mandibular central incisors; Upper lip‐E line, distance between upper lip anterior point and E line (esthetic plane of Ricketts; line that passes through the tip of the nose and soft tissue pogonion); Lower lip‐E line, distance between lower lip anterior point and E line.

(a)

(b)

(c)

Figure 61.5  Case 61.1: VTOs: (a) Pre-treatment. (b) Four premolar extractions. (c) Four premolar extractions and maxillary molar intrusion.

(Continued )

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Section IV  Esthetic Control with TADs

Figure 61.6  Case 61.1: Intraoral photographs (nine months of treatment).

­ entition and to provide necessary anchorage, two TADs d (diameter, 1.6 mm; length, 8 mm) were placed bilaterally in the buccal ­interradicular bone between the maxillary second premolars and first molars. Two additional TADs (diameter, 1.6 mm; length, 8 mm) were placed bilaterally in the buccal interradicular bone between the maxillary first and second molars. A modified transpalatal arch appliance was delivered so that elastomeric chains could be connected from the extension arms with hooks to the buccal TADs [5]. Unfortunately, the two TADs installed in the buccal interradicular bone between our patient’s maxillary first and second molars failed. Therefore, the maxillary second molars were intruded by intrusion step bends using 0.019 × 0.025‐in stainless steel archwire [5]. In the mandibular arch, crimpable hooks were engaged between the mandibular lateral incisors and canines, and elastomeric chains were applied from the hooks to the mandibular first molars with 0.017 × 0.025‐in stainless steel archwire for space closing (Figures 61.6–61.8). During the finishing stage, final detailing of the occlusion was accomplished using 0.017 × 0.025‐in titanium molybdenum alloy (TMA) archwires in conjunction with posterior vertical elastics with Class III vectors. A fixed retainer was placed canine‐to‐canine on the mandible and lateral incisors in the maxilla before debonding. Essix retainers were also delivered to maintain the ­intrusion of the maxillary posterior teeth. Total treatment time for this patient was 31 months.

Figure 61.7  Case 61.1: Illustration of four TADs and a modified transpalatal arch appliance for maxillary posterior tooth intrusion.

Treatment Results Post‐treatment records showed the treatment objectives were met. The 31 months of active treatment led to an improved profile and smile esthetics. Optimal overjet and overbite were achieved, and the dental midline was drastically improved. Class I molar relationships were achieved and the maxillary first molars were slightly

Figure 61.8  Case 61.1: Progress panoramic radiograph after space closing.

Figure 61.9  Case 61.1: Post‐treatment photographs and radiographs.

(Continued )

682

Section IV  Esthetic Control with TADs

overintruded to prevent relapse. The patient reported no pain or TMJ joint symptoms both during and after treatment. Post‐treatment panoramic radiograph showed no significant signs of root or bone resorption, and acceptable root parallelism was present. The treatment helped to improve the patient’s facial profile, particularly her lower anterior facial height and the protrusion of both lips. Post‐

treatment lateral cephalometric analysis showed slight skeletal change (ANB, from 5.9° to 3.6°). The maxillary and mandibular incisors were retroclined during treatment (U1‐SN, from 97.3° to 93.2°) (IMPA, from 93.3° to 86.3°). The mandibular plane angle (SN‐MP, from 54.4° to 51.8°) was reduced by maxillary molar intrusion which induced counterclockwise rotation of the mandible and slightly reduced lower anterior facial height (Figures 61.9 and 61.10).

Figure 61.10  Case 61.1: Cephalometric superimposition: pre-treatment (black); post‐treatment (red).

Figure 61.11  Case 61.1: One year post‐treatment photographs and radiographs.

Chapter 61  Improved Facial Profile with Premolar Extraction and Molar Intrusion

Figure 61.11  (Continued)

Records taken at one year post‐retention showed that the treatment results were maintained, and the patient had an improved occlusion. The patient was referred to

a significant increase in upper lip thickness remaining during the 10 year post‐retention study [13]. When treating Class II patients who have had four molars extracted, keep in mind that lip strain can be an issue. Lip strain can cause an incompetency when patients try to close their lips over protrusive teeth, and is defined as the difference between upper lip thickness and the upper lip thickness at the vermillion border [14]. For example, if the upper lip thickness is 15 mm and the vermillion border thickness is 11 mm, then the lip strain would be 4 mm. Previous studies have shown that a retraction of the upper lip does not follow tooth retraction until lip strain and lip taper have been eliminated [14, 15]. In our case, extraction of the four premolars followed by maxillary incisor retraction should help to eliminate lip strain. A benefit of VTO is that it can help visualize all these different predictions of soft tissue profile changes that may occur with orthodontic treatment. An important consideration to keep in mind when treating full‐grown Class II patients is how to improve

an oral surgeon to have her third molars evaluated for extraction (Figure 61.11).

their facial profile. Because of this, treatment plans will  differ from one Class II patient to the next. For instance, in ­skeletal Class II patients with retrognathic mandibles, one treatment modality includes intrusion of the ­maxillary posterior teeth with the use of TADs. TADs have many benefits and can be a potential alternative to  any orthognathic surgery that may be needed to ­correct  patient profile. Intruding the maxillary molars with  TADs can produce autorotation of the mandible, thus helping correct Class II jaw relationships [16]. This autorotation helps with the advancement and forward positioning of the chin [17–19]. In addition, it can help reduce mentalis muscle strain, reduce anterior lower facial height, and increase overbite [17, 19, 20]. The convex profile of our patient was a major concern that we addressed in this case. Intruding the maxillary molars allowed us to address this concern and improve her facial profile. Class II patients tend to have proclined mandibular incisors due to dental compensation. Treatment that

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includes autorotation of the mandible may lead to a negative overjet or edge‐to‐edge bite, which can cause trauma from occlusal contact. Mandibular first premolar extractions and retroclining of the mandibular incisors prior to mandibular rotation can help prevent these negative effects. In the ­present case, the patient’s incisors were retroclined to improve her profile. As shown in different VTOs of our adult patient, the benefit of VTOs is that they allow the patients to see the potential outcomes of alternative treatment modalities before deciding on what they want to do.

61.3 ­Conclusion Video images and VTOs help patients visualize what to expect throughout their treatment process, as well as predicting soft tissue changes that are possible with different treatment options. With the help of TADs, our patient’s facial profile was improved through intrusion of her maxillary molars and autorotation of her mandible. Premolar extractions helped to address her protrusive lips, as well as to obtain optimal overjet that was needed after the counterclockwise rotation of her mandible.

­References 1 Hayat A, Woodside DG, Mayhall JT, Titley K. VTO Predicted profile changes vs actual changes in untreated subjects. Am J Orthod Dentofacial Orthop. 1999;115:111. 2 Sarver DM, Johnston MW, Matukas VJ. Video imaging for planning and counseling in orthognathic surgery. J Oral Maxillofac Surg. 1988;46:939–945. 3 Phillips C, Hill BJ, Cannac C. The influence of video imaging on patients’ perceptions and expectations. Angle Orthod. 1995;65:263–270. 4 Le TN, Sameshima GT, Grubb JE, Sinclair PM. The role of computerized video imaging in predicting adult extraction treatment outcomes. Angle Orthod. 1998;68:391. 5 Tai K, Park JH. Improvement of facial profile by nonextraction orthodontic treatment with temporary skeletal anchorage devices and visual treatment objectives. Am J Orthod Dentofacial Orthop. 2018;154:708–717. 6 Erdinc AE, Nanda RS, Dandajena TC. Profile changes of patients treated with and without premolar extractions. Am J Orthod Dentofacial Orthop. 2007;132:324–331. 7 Young TM, Smith RJ. Effects of orthodontics on the facial profile: a comparison of changes during non‐extraction and four premolar extraction treatment. Am J Orthod Dentofacial Orthop. 1993;103:452–458. 8 Luppanapornlarp S, Johnston LJ. The effects of premolar‐ extraction: a long‐term comparison of outcomes in “clear‐cut” extraction and nonextraction Class II patients. Angle Orthod. 1993;63:257–272. 9 Rathod AB, Araujo E, Vaden JL, et al. Extraction vs no treatment: long‐term facial profile changes. Am J Orthod Dentofacial Orthop. 2015;147:596–603. 10 Iared W, Koga da Silva E, Iared W, Macedo CR. Esthetic perception of changes in facial profile resulting from orthodontic treatment with extraction of premolars: a systematic review. J Am Dent Assoc. 2017;148:9–16.

11 Janson G, Branco N, Fernandes T, et al. Influence of orthodontic treatment, midline position, buccal corridor and smile arc on smile attractiveness. Angle Orthod. 2011;81:153–161. 12 Bowman SJ, Johnston LE. The esthetic impact of extraction and nonextraction treatments on Caucasian patients. Angle Orthod. 2000;70:3–10. 13 Rains MD, Nanda R. Soft‐tissue changes associated with maxillary incisor retraction. Am J Orthod. 1982;81:481–488. 14 Oliver BM. The influence of lip thickness and strain on upper lip response to incisor retraction. Am J Orthod. 1982;82:141–149. 15 Holdaway, RA. A soft‐tissue cephalometric analysis and its use in orthodontic treatment planning. Part I. Am J Orthod. 1983;84:1–28 16 Park JH, Tai K, Ikeda M, Kim DA. Anterior open bite and Class II treatment with mandibular incisor extraction and temporary skeletal anchorage devices. J World Fed Orthod. 2012;1:e121–e131. 17 Kim K, Choy K, Park YC, et al. Prediction of mandibular movement and its center of rotation for nonsurgical correction of anterior open bite via maxillary molar intrusion. Angle Orthod. 2018;88:538–544. 18 Albogha MH, Takahashi I, Sawan MN. Early treatment of anterior open bite: comparison of the vertical and horizontal morphological changes induced by magnetic bite‐blocks and adjusted rapid molar intruders. Korean J Orthod. 2015;45:38–46. 19 Buschang PH, Sankey W, English JP. Early treatment of hyperdivergent open‐bite malocclusions. Semin Orthod. 2002;8:130–140. 20 Umemori M, Sugawara J, Mitani H, et al. Skeletal anchorage system for open‐bite correction. Am J Orthod Dentofacial Orthop. 1999;115:166–184.

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62 TADs vs. Orthognathic Surgery Jeong‐Ho Choi Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, South Korea

62.1 ­Introduction Since the introduction of temporary anchorage devices (TADs) in orthodontics, it has been possible to move teeth more freely in any direction, and the movable range of teeth has also been significantly increased. This has led to changes in Proffit’s “Envelope of Discrepancy,” which explains the limits of tooth movement [1]. When it was first published, the “Envelope” was divided into three categories: orthodontics alone, orthodontics‐with‐orthopedics, and surgery. However, “skeletal anchorage” has recently been added, leading to significant changes in orthodontic treatment plans. The boundaries for “skeletal anchorage” are beyond the limits of general orthodontics alone or orthodontics‐with‐ orthopedics, but smaller than those of surgery. Traditionally, treatment was compromised at a certain level or had to be accompanied by surgery when tooth movement was needed beyond the scope of the orthodontic category with adults or the orthodontics‐with‐orthopedics category for growing patients. Now, a significant portion of these treatments is possible without orthognathic surgery. In this chapter, we will discuss the indications and limitations of orthodontic treatments using TADs, which replace some areas of orthognathic surgery. The dimensions will be divided into categories; transverse, vertical, and anteroposterior as mentioned in the “Envelope of Discrepancy.”

62.2 ­Transverse Dimensions The most common problem with the transverse dimension is the narrow width of the maxillary arch. Fortunately, it is relatively easy to resolve this problem through rapid

palatal expansion (RPE) in growing children, but it is more difficult in adults with fused median palatine sutures. Surely, palatal expansion can be achieved in adults with surgical assistance (surgically assisted rapid palatal expansion, SARPE) or actual surgery (Le Fort I segmental osteotomy). By using miniscrew‐assisted rapid palatal expanders (MARPEs), which add TADs to an existing RPE as anchorage, the midpalatal suture can be opened, and the maxilla can be expanded, even in adults with fused midpalatal sutures (Figure  62.1) [2]. Although not successful in all patients, successful midpalatal suture opening has been reported in a significant number of cases. The TADs serve as a mediator that fixes the RPE and directs the expansion force directly to the maxilla, thereby allowing the median palatine suture to be opened without surgery. A minimal surgical intervention, one that is not too invasive, may assist MARPE in adults [3]. In general, treatment with MARPE in adults can achieve similar results to RPE treatment in growing children [4]. However, there may be some differences. By using TADs for skeletal anchorage and using fewer teeth as anchors, unwanted buccal tilting of the teeth can be reduced and more parallel expansion can be achieved. This also reduces the recession of the buccal gingiva in the upper teeth [5]. Various MARPE designs have been reported by several authors [2, 4–7]. Most of the features are similar but may vary slightly, depending on the design [8]. Maxillary skeletal expanders (MSEs), which use bicortical palatal miniscrews, claim to focus a stronger force directly on the skeleton, allowing more successful expansion in adults, especially in the posterior region. They are also reported to be advantageous for airway widening [2, 5, 9, 10].

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Figure 62.1  Class III malocclusion with posterior crossbite (left) and anterior open bite. Adult female (20 years 10 months). (a) Initial intraoral photographs. (b) MARPE with bicortical screws was used for maxillary expansion. (c, d) Cone‐beam computed tomography (CBCT) images before (c) and after (d) expansion. Midpalatal suture was split. (e) Treatment finished after 25 months. Posterior crossbite was corrected. (f) One‐year retention.

The main reason for expanding the maxilla is to solve problems caused by a narrow maxillary arch (e.g. posterior crossbite). In addition to eliminating inter‐arch discrepancies, maxilla expansion can help to solve airway problems or be used together with a facemask to amplify the effect, as described later [9, 10].

62.3 ­Vertical Dimensions A number of problems with vertical dimension have made orthognathic surgery necessary in the past, but with the help of TADs, successful orthodontic outcomes can be achieved without surgery in some cases. Two typical

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s­ ituations – gummy smile and anterior open bite – will be reviewed.

62.3.1  Gummy Smile This is a condition in which excessive gingiva can be seen under the upper lip with smiling. It is caused by various factors such as vertical maxillary excess, abnormal lip length (a short philtrum), hyperactivity of the upper lip, altered passive eruption, and dentoalveolar extrusion/protrusion. Appropriate treatment depends on the cause. In the case of vertical maxillary excess, vertical impaction of the maxilla through Le Fort I osteotomy has been considered as a solution to this problem [11]. Impaction or retraction of the maxillary dentition will help to reduce a gummy smile by reducing exposure of the maxillary incisors and gingiva. In the past, high pull headgear with J hooks were used as a non‐surgical approach, but it was difficult to obtain satisfactory outcomes. Now, with TADs, some gummy smiles can be treated without surgery [12, 13]. TADs and proper mechanics make it possible to move the maxillary anteriors or entire maxillary dentition upward and/or backward relatively easily, thereby reducing excessively exposed gingiva (Figure  62.2). In addition, many gummy smile patients with vertical maxillary excess show lip incompetency due to their increased lower anterior facial height, both of which can be improved by the intrusion of the total maxillary dentition and subsequent reduction of the vertical dimension. In the case of skeletal Class II patients with chin deficiency, conditions that are frequently accompanied by vertical maxillary excess and gummy smile, forward movement of the chin can be achieved with mandibular autorotation when the entire maxillary dentition is intruded [13]. However, care should be taken to avoid a flat smile arc, which can be formed when intruding the maxillary anterior dentition with TADs to correct gummy smile [13]. A flat occlusal plane makes a flat smile arc. In order to prevent this, it is sometimes necessary to intrude posterior teeth together. It should also be noted that intrusion is accompanied by a loss of the attached gingiva. Inflammation of the periodontal tissue must be checked before intrusion.

62.3.2  Anterior Open Bite Anterior open bite occurs for various reasons and is one of the most difficult malocclusions to correct. Before TADs, orthodontic treatment was based on habit‐breaking appliances, anterior vertical elastics, multiloop edgewise archwire (MEAW) techniques, and anterior vertical correctors,

and in severe skeletal open bite cases, orthognathic surgery was the only answer. As direct intrusion of the posterior dentition became possible with TADs, the range of anterior open bite correction by orthodontic treatment was expanded [14–16]. For example, secondary open bite by temporomandibular disorder (TMD) and condylar resorption can be treated with TADs [16]. And with the anterior open bite cases which had to be treated with surgical orthodontics in the past, it is now possible to correct them by intrusion of the posterior teeth with orthodontics (Figure 62.3). Anterior open bite is a malocclusion with a high relapse rate. When correcting an open bite by intrusion of the upper posterior teeth, the intruded teeth have been reported to extrude back about 15–20%, which can decrease the overbite. Because of the reported likelihood of relapse when the mandibular molars are intruded [17], it might be necessary to overcorrect by about 15–20%. Some authors [14] recommend the use of an active retainer after treatment, and it should be noted that discontinuing use of the retainer can lead to new retention problems. The treatment of anterior open bite by intruding posterior teeth with TADs is more advantageous in skeletal Class II malocclusion cases because of the forward rotation of the mandible along with open bite correction. This makes it possible to obtain a more esthetic appearance with an advanced chin, and to improve the Class II dental relationships [18, 19]. On the other hand, it should be noted that with skeletal Class III malocclusion and anterior open bite, forward rotation of the mandible can exacerbate chin protrusion and Class III dental relationships [18]. Meanwhile, TADs can also be used for anterior extrusion [19]. Figure 62.4 shows a secondary anterior open bite by TMD, which was treated with anterior extrusion using a TAD. Unlike extrusion with vertical elastics, there is an advantage that only the teeth of one jaw can be extruded without simultaneous extrusion of the other side. However, care should be taken to maintain a consonant smile line and not make gummy smile when extruding anterior teeth.

62.4 ­Sagittal Dimensions The typical role of TADs is, of course, absolute anchorage for tooth movement. Traditionally, a transpalatal arch (TPA) and headgear were used to reinforce the anchorage for retraction of anterior teeth, but they did not provide absolute anchorage, whereas TADs do, allowing for better retraction of anterior teeth. With TADs, changes in the sagittal dimension make it possible to treat with orthodontics some malocclusion cases that could only be treated with orthognathic surgery in the past.

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Figure 62.2  Class I malocclusion with gummy smile and anterior protrusion. Adult female (21 years 6 months). (a) Initial facial photographs showing gummy smile and lip protrusion. (b) Initial intraoral photographs. (c) Four first premolars were extracted. TADs were used for maxillary intrusion and retraction. (d) Intraoral photographs after 24 months treatment. (e) Facial photographs after treatment. Gummy smile and protrusion have been improved. (f) Superimposition of lateral cephalometric tracings.

62.4.1  Bimaxillary Protrusion In patients with severe dentoalveolar protrusion, maximum anchorage is required for maximal retraction of the anterior teeth. Anterior segmental osteotomy (ASO) used to be the preferred treatment for patients with severe protrusion that was difficult to treat with orthodontics, or in

cases where quick treatment was needed. But the use of ASO has significantly decreased since the advent of TADs. Although it is not possible to shorten the treatment time with TADs as with ASO, maximum retraction of the anterior teeth can be achieved to some extent (Figure  62.2) because TADs provide absolute anchorage [20].

Chapter 62  TADs vs. Orthognathic Surgery

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Figure 62.2  (Continued)

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Figure 62.3  Class II division 1 malocclusion with anterior open bite. (a) Initial. (b) Intrusion of maxillary molars using bonded TPA and a mini‐implant. (c) After correction of anterior open bite (overcorrection showing posterior open bite). (d) After treatment.

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Figure 62.4  A case of relapsed anterior open bite due to the remodeling of the mandibular condyle. She had orthodontic treatment combined with orthognathic surgery previously. However, anterior open bite relapsed because of TMD and condylar resorption. Considering incisal display, retreatment was planned to extrude maxillary anterior teeth rather than intruding posteriors. (a) Beginning of retreatment. (b) Selective force application by extrusion spring and a TAD. (c) After correction of anterior open bite. (d) After treatment. (e) Fifteen‐month retention after treatment (CBCT 3D imaging). (f, g) Extrusion spring made of 0.014‐in stainless steel before (f) and after (g) application.

However, there is a difference between the retraction of anterior teeth using TADs and that with ASO. If TADs are used to move anterior teeth backward, they cannot be moved in translation, as they can with ASO. The bodily tooth movement itself may be possible with proper biomechanics, but there are still some anatomical limitations. Care should be taken when retracting anterior teeth bodily through the whole extraction space, as they can invade the alveolar bone boundary of the palate or symphysis. Special attention should be paid to patients who have a thin symphysis with a hyperdivergent skeletal pattern and those with thin alveolar bone around the anterior teeth [21]. Of course, when the thickness of the alveolar bone is sufficient, teeth can be translated by a considerable amount using TADs.

62.4.2  Skeletal Class II With skeletal Class II malocclusions, TADs offer options beside surgery. This is because most skeletal Class II malocclusions are accompanied by a mandibular deficiency. Mandibular deficiencies can cause functional problems such as obstructive sleep apnea syndrome, as well as esthetic problems. When TADs are used to move the maxillary dentition backward or the mandibular molars forward, a significant improvement in occlusal relationship can be achieved, including a reduction in excessive overjet (Figure  62.5).

They can also solve vertical problems, and in some cases may help to resolve a chin deficiency by advancing the chin with autorotation of the mandible following intrusion of the posterior teeth [13, 18, 19]. This is an effective treatment method for Class II malocclusions with anterior open bite and is especially good for patients with TMD, who have a backward rotation of their mandible due to condylar resorption and remodeling. Since TADs by themselves are not able to correct mandibular deficiency, they will not always be able to replace surgery, but with a careful case selection, TADs can be used to treat a number of Class II malocclusion patients without surgery.

62.4.3  Skeletal Class III Non‐surgical orthodontic treatment of skeletal Class III malocclusion is difficult for two reasons. First, it is difficult to achieve functional occlusion and second, there is a limit to the improvement possible with facial esthetic problems caused by a large mandible. TADs can be used to treat skeletal Class III malocclusion in two ways. One is to distalize the entire mandibular dentition [22–24]. Anterior crossbite is resolved and the protruding lower lips are retracted when the lower teeth are retracted, so the esthetics of the face can be improved to some extent. In this way, results that were achieved

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Figure 62.5  Class II division 1 malocclusion with crowding. Adult female (25 years 4 months). (a) Initial. (b) Her treatment began with extraction of maxillary first and mandibular second premolars. (c) TADs were used for reinforced anchorage to retract maxillary anteriors and to protract mandibular posteriors. Also, maxillary posterior teeth were intruded to close the anterior open bite. (d) Molar relationship has been changed to Class I relationship. (e) After treatment. (f) Three‐year retention.

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with orthognathic surgery in the past can now be obtained partly with orthodontic treatment using TADs. However, anatomical limitations must be considered when the mandibular dentition is distalized. As noted above, it is necessary to avoid excessive displacement of the lower anterior teeth when the symphysis is thin, something common with hyperdivergent skeletal Class III malocclusions. Also, movement of the posterior teeth when they are too close to the ramus should be avoided to prevent impingement of the teeth into the gingiva. The second way that TADs are used in skeletal Class III malocclusion is for dentofacial orthopedics in growing children. With the more severe skeletal Class III malocclusions that are difficult to treat with common facemask treatment, it has been reported that plate‐shaped TADs can be used to increase the success rate by applying force directly to the maxilla [25, 26]. Some studies have reported that the use of a special type of MARPE improves the outcomes of the facemask treatment by separating the maxillary complex from the craniofacial skeleton, even when patients are older than the general indication [9]. As the success rate of dentofacial orthopedics is increased by using TADs, the need for orthognathic surgery will be reduced. For instance, there is a report about a treatment method that uses plate‐shaped TADs in both jaws with Class III elastics attached directly to the TADs [27]. Although these new approaches need more evidence‐based research, they are expected to help correct skeletal Class III in growing children.

62.5  ­TADs with Orthognathic Surgery TADs are used for more than just avoiding orthognathic surgery, they can be used to supplement it. Traditionally, when pre-surgical orthodontics is finished, full‐size surgical archwires are placed for the surgery. This requires a considerable period of pre-surgical orthodontic treatment, during which time the patient must endure rather undesirable facial changes. To reduce some of the discomfort of pre-surgical orthodontics, the recent trend has been to minimize presurgical orthodontics or use a surgery‐first approach. In such cases, several TADs are placed in the upper and lower

Figure 62.6  Intermaxillary fixation using TADs (three days after surgery). The patient had Le Fort I and bilateral sagittal split osteotomy. TADs and elastics were used for intermaxillary fixation instead of surgical wires. Source: Courtesy of Dr. Sang‐Jin You.

jaws and elastics, rather than surgical wires, are used between them for intermaxillary fixation (Figure  62.6). TADs are also usually used to help in the post‐surgical orthodontic phase in surgery‐first approaches [28, 29]. In summary, TADs can be substituted for orthognathic surgery, but can also be a useful aid with orthognathic surgery.

62.6 ­Conclusions TADs are expanding the range of tooth movement without surgery and, as of yet, the limits are unknown. Orthodontic treatment with TADs is replacing a significant portion of treatment that used to require orthognathic surgery. TADs facilitate minimally invasive, less traumatic treatment, and are economically feasible due to their relatively low cost. However, without orthognathic surgery, there are still some limitations in the amount of esthetic improvement and anatomical tooth movement possible with skeletal discrepancy cases. By recognizing these limitations and using TADs with the appropriate biomechanics, the orthodontist can correct malocclusions in a more flexible way with a wider range of options than before. The creative use of TADs is playing a major role in not only replacing orthognathic surgery but also in blazing new trails in orthodontics.

R ­ eferences 1 Nguyen T, Proffit W. The decision‐making process in orthodontics. In: Graber LW, Vanarsdall Jr. RL, Vig BDS, et al., eds. Orthodontics Current Principles and Techniques, 6th edn. New York: Elsevier, 2017, chapter 8.

2 Carlson C, Sung J, McComb RW, et al. Microimplant‐ assisted rapid palatal expansion appliance to orthopedically correct transverse maxillary deficiency in an adult. Am J Orthod Dentofacial Orthop. 2016;149:716–728.

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3 Lee SC, Park JH, Bayome M, et al. Effect of bone‐borne rapid maxillary expanders with and without surgical assistance on the craniofacial structures using finite element analysis. Am J Orthod Dentofacial Orthop. 2014;145:638–648. 4 Park JJ, Park YC, Lee KJ, et al. Skeletal and dentoalveolar changes after miniscrew assisted rapid palatal expansion in young adults: A cone‐beam computed tomography study. Korean J Orthod. 2017;47:77–86. 5 Kim BH. Clinical application of miniscrew‐assisted rapid palatal expansion. J Korean Foundation Gnatho‐Orthod Res. 2015:12;7–25. 6 Wilmes B, Drescher D. A miniscrew system with interchangeable abutments. J Clin Orthod. 2008;42:574–580. 7 Winsauer H, Vlachojannis J, Winsauer C, et al. A bone‐borne appliance for rapid maxillary expansion. J Clin Orthod. 2013;47:375–381. 8 Walter A, Wendl B, Ploder O, et al. Stability determinants of bone‐borne force‐transmitting components in three RME hybrid expanders – an in vitro study. Eur J Orthod. 2017;39:76–84. 9 Moon W. Class III treatment by combining facemask (FM) and maxillary skeletal expander (MSE). Semin Orthod. 2018;24:95–107. 10 Hur JS, Kim HH, Choi JY, et al. Investigation of the effects of miniscrew‐assisted rapid palatal expansion on airflow in the upper airway of an adult patient with obstructive sleep apnea syndrome using computational fluid structure interaction analysis. Korean J Orthod. 2017;47:353–364. 11 Garber DA, Salama MA. The aesthetic smile: diagnosis and treatment. Periodontology 2000 1996;11:18–28. 12 Hong RK, Lim SM, et al. Orthodontic treatment of gummy smile by maxillary total intrusion with a midpalatal absolute anchorage system. Korean J Orthod. 2013;43:147–158. 13 Paik CH, Park HS, Ahn HW. Treatment of vertical maxillary excess without open bite in a skeletal Class II hyperdivergent patient. Angle Orthod. 2017;87:625– 633. 14 Baek MS, Choi YJ, Yu HS, et al. Long‐term stability of anterior open‐bite treatment by intrusion of maxillary posterior teeth. Am J Orthod Dentofacial Orthop. 2010;138:396.e1–396.e9. 15 Park HS, Kwon OW, Sung JH. Nonextraction treatment of an open bite with microscrew implant anchorage. Am J Orthod Dentofacial Orthop. 2006;130:391–402.

16 Kim TW. Clinical Application of Orthodontic Mini‐ Implant. Seoul: Myungmun Publishing, 2008. 17 Sugawara J, Baik UB, Umemori M, et al. Treatment and posttreatment dentoalveolar changes following intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthodon Orthognath Surg. 2002;17:243–253. 18 Choi JH. Treatment of the anterior open bite with bonded connected TPA. Invited lecture at the 14th Academic Congress of Dentistry of Catholic University, Seoul, December 4, 2016. 19 Choi JH. Class II malocclusion with open bite. Clin J Korean Assoc Orthod. 2013:3;58–59. 20 Park HS, Bae SM, Kyung HM, Sung JH. Microimplant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin Orthod. 2001:35;417–422. 21 Wehrbein H, Bauer W, Diedrich P. Mandibular incisors, alveolar bone, and symphysis after orthodontic treatment. A retrospective study. Am J Orthod Dentofacial Orthop. 1996;110:239–246. 22 Heo W. Application of orthodontic mini‐implants to distalize lower dentition. Clin J Korean Assoc Orthod. 2017:7;52–60. 23 Jing Y, Han X, Guo Y, et al. Nonsurgical correction of a Class III malocclusion in an adult by miniscrew‐assisted mandibular dentition distalization. Am J Orthod Dentofacial Orthop. 2013;143:877–887. 24 Kuroda S, Tanaka E. Application of temporary anchorage devices for the treatment of adult Class III malocclusions. Semin Orthod. 2011;17:91–97. 25 Baek SH, Yang IH, Kim KW, Ahn HY. Treatment of Class III malocclusions using miniplate and mini‐implant anchorage. Semin Orthod. 2011;17:98–107. 26 Cha BK, Choi DS, Ngan P, et al. Maxillary protraction with miniplates providing skeletal anchorage in a growing Class III patient. Am J Orthod Dentofacial Orthop. 2011;139:99–112. 27 De Clerck HJ, Cornelis MA, Cevidanes LH, et al. Orthopedic traction of the maxilla with miniplates: a new perspective for treatment of midface deficiency. J Oral Maxillofac Surg. 2009;67:2123–2129. 28 Paik CH, Woo Y, Kim J, Park JU. Use of miniscrews for intermaxillary fixation of lingual‐orthodontic surgical patients. J Clin Orthod. 2002;36:132–136. 29 Sugawara J, Nagasaka H, Yamada S, et al. The application of orthodontic miniplates to Sendai surgery first. Semin Orthod. 2018;24:17–36.

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63 Advantages of Miniscrew Usage for Pre‐ and Post-operative Orthodontics in Skeletal Class III Malocclusion Patients Seong Sik Kim and Sung‐Hun Kim Department of Orthodontics, School of Dentistry, Pusan National University, Yangsan, South Korea

63.1 ­Introduction The introduction and application of miniscrews in orthodontics has brought significant changes to the concept of anchorage as it applies to conventional tooth movement and orthodontic treatment planning [1–3]. They eliminated the need for extraoral orthodontic appliances, such as J‐hook headgear, which means that treatment results will be independent of patient cooperation and thus increase the likelihood of obtaining favorable and consistent results. In this way, miniscrews have allowed an expanded social acceptance of orthodontic treatment [4–6]. Miniscrews were initially thought of as replacements for extraoral orthodontic appliances for tooth movement. However, they are now being widely used for traction of impacted teeth as well as anchorage reinforcement for maxillary expansion [7–10]. The purpose of this chapter is to introduce the advantages and applications of miniscrews in the intermaxillary fixation (IMF) of orthognathic surgery patients.

63.2  ­Advances in Pre-operative Orthodontic Treatment with Miniscrews in Orthognathic Surgery Patients

are in the compensated position so that an esthetic and functional position can be maintained after the surgery [11]. The goal of pre-operative orthodontic treatment is to create a stable anterior and posterior occlusal contact in the expected post-operative occlusion based on the appropriate relationship between maxillary and mandibular arch widths. Following this preparation, oral and maxillofacial surgeons perform operations to reposition the maxillomandibular complex in order to obtain maximal facial esthetics (Figure 63.1) [12, 13]. Stable contact of the maxillary and mandibular teeth is an essential requirement for effective post-operative orthodontic treatment. Because IMF is achieved by spurs attached to an orthodontic wire, teeth should be arranged so that at least a 0.019 × 0.025‐in stainless steel archwire can be applied without resistance. This is the major objective of the extensive pre-operative orthodontic treatment period, but according to statistics, the longer the preoperative orthodontic treatment period, the worse the patient cooperation and lower the expectations [14]. Fortunately, when miniscrews are used for IMF, orthognathic surgery can be performed if there are at least three contacts of anterior and posterior teeth, the minimal requirement for a stable occlusion. This explains why the use of miniscrews can shorten the duration of the preoperative orthodontic treatment period.

63.2.1  Shortening the Period of  Pre-operative Orthodontic Treatment

63.2.2  Fewer Maxillary Premolar Extractions

When treating skeletal Class III malocclusion patients, it is often difficult to obtain proper occlusion with just tooth movement, so orthognathic surgery is usually the treatment of choice. For orthognathic surgery to be successful, it is necessary to perform pre-operative orthodontics to decompensate the maxillary and mandibular incisors that

The maxilla is first repositioned and fixed with orthognathic surgery followed by a repositioning of the mandible. Maxillofacial surgeons use the anteroposterior position and inclination of the maxillary incisors to set the maxillary position [15, 16], so it is difficult to obtain satisfactory surgical results if the orthodontist and surgeon have a different

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section V  Application of TADs in Surgical Cases

(a)

(b)

(c)

Figure 63.1  IMF types: (a) archbar fixation, (b) surgical archwire fixation, and (c) orthodontic miniscrew fixation.

Figure 63.2  Pre-treatment facial and intraoral photographs.

understanding of the anteroposterior position and inclination of the maxillary incisors. It is important, at least during the pre-operative orthodontic treatment period, for the orthodontist to correct the anteroposterior position and inclination of the maxillary incisors in order for the surgeon to achieve maximal esthetic results. Since the position of the maxillary incisors has an absolute impact on the facial aesthetics, it is important to evaluate their position relative to the cranial base structures during conventional, non‐surgical orthodontic treatment. However, with orthognathic surgical cases, the position and inclination of the maxillary incisor, which is set on the basis of the cranial base structures, can be changed after the positions of the maxilla and the mandible have been surgically modified.

Therefore, it would be wise to use the occlusal plane as a reference to determine the inclination of the incisors [17]. In Asians, the average inclination of the maxillary incisors on the occlusal plane is in the range of 52–56°, and that of the mandibular incisors is in the range of 65–70°. Functional occlusion and esthetic appearance should be easy to obtain post‐surgically if the orthodontist has set the incisor inclination within the appropriate range relative to the occlusal plane during pre-operative orthodontic treatment, and the oral surgeon repositions the maxillomandibular complex within the normal range of the occlusal plane (Figures 63.2– 63.6). The most common feature of Class III patients, highly prevalent in Asians, is labioversion of the maxillary incisors and a reduced maxillary width. When the inclination of the

Chapter 63  Miniscrew Usage in Skeletal Class III Malocclusion Patients Norm

Initial

SNA (°)

81.6

84.1

SNB (°)

79.1

86.0

ANB (°)

2.4

–1.9

AFH (mm)

127.4

127.7

FH-OP (°)

13.0

5.1

Pog-N Perp (mm)

–1.8

7.0

FMA (°)

25.0

27.2

116.0

130.8

U1-MxOP (°)

56.0

45.2

L1-MnOP (°)

65.0

73.2

IMPA (°)

95.0

82.6

U1-FH (°)

Figure 63.3  Pre-treatment lateral cephalometric analysis. The inclination of the maxillary incisors on the occlusal plane (45.2°) is less than 56°, so maxillary premolar extraction could be chosen as the treatment option. SNA, Sella‐nasion‐A point; SNB, sella‐ nasion‐B point; ANB, A point‐nasion‐B point; AFH, anterior facial height, distance between nasion and menton; FH‐OP, FH plane to occlusal plane; Pog‐N Perp, distance between pogonion and nasion perpendicular line; FMA, Frankfort mandibular plane angle; U1‐FH, long axis of maxillary central incisor to FH plane; U1‐MxOP, long axis of maxillary central incisor to maxillary occlusal plane; L1‐MnOP, long axis of mandibular central incisor to mandibular occlusal plane; IMPA, incisor mandibular plane angle.

(a)

(b)

(c)

Figure 63.4  Treatment progress. (a) Initial tooth movement after maxillary premolar extraction. (b) Pre-surgical orthodontic treatment completed. (c) Post‐surgical orthodontic treatment.

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Section V  Application of TADs in Surgical Cases

Figure 63.5  Post‐treatment photographs. It can be confirmed that a stable canine guidance has been formed. Norm

Initial

Final

SNA (°)

81.6

84.1

88.6

SNB (°)

79.1

86.0

84.8

2.4

–1.9

3.8

AFH (mm)

127.4

127.7

121.4

FH-OP (°)

13.0

5.1

7.6

Pog-N Perp (mm)

–1.8

7.0

5.5

FMA (°)

25.0

27.2

26.9

ANB (°)

116.0

130.8

120.8

U1-MxOP (°)

56.0

45.2

51.2

L1-MnOP (°)

65.0

73.2

70.4

IMPA (°)

95.0

82.6

89.0

U1-FH (°)

Figure 63.6  Post‐treatment lateral cephalometric analysis. The maxillary incisor inclination was within the appropriate range relative to the occlusal plane. SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; AFH, anterior facial height, distance between nasion and menton; FH‐OP, FH plane to occlusal plane; Pog‐N Perp, distance between pogonion and nasion perpendicular line; FMA, Frankfort mandibular plane angle; U1‐FH, long axis of maxillary central incisor to FH plane; U1‐MxOP, long axis of maxillary central incisor to maxillary occlusal plane; L1‐MnOP, long axis of mandibular central incisor to mandibular occlusal plane; IMPA, incisor mandibular plane angle.

maxillary incisors with respect to the occlusal plane is less than 52°, it is necessary to expand the maxillary width to correct the inclination [18, 19]. However, since most patients requiring surgery are adults, maxillary expansion is difficult. In order to solve this problem, maxillary premolar

extraction has been predominantly chosen as the treatment option in Korea. Recently, however, it has been reported that miniscrew‐assisted rapid palatal expansion (MARPE) has allowed maxillary expansion in adults to some extent  (Figures  63.7–63.12) [9, 10]. The Department of

Chapter 63  Miniscrew Usage in Skeletal Class III Malocclusion Patients

Figure 63.7  Pre-treatment facial and intraoral photographs. In childhood, the maxillary first premolar was extracted and orthodontic treatment was performed, but as the growth progressed, reduction of maxillary width, mandibular advancement and facial asymmetry occurred.

Norm

Initial

SNA (°)

81.6

85.4

SNB (°)

79.1

85.4

ANB (°)

2.4

0.0

AFH (mm)

127.4

142.5

FH-OP (°)

13.0

4.7

Pog-N Perp (mm)

–1.8

1.5

FMA (°)

25.0

23.1

116.0

124.2

U1-MxOP (°)

56.0

51.3

L1-MnOP (°)

65.0

68.5

IMPA (°)

95.0

94.8

U1-FH (°)

Figure 63.8  Pre-treatment lateral cephalometric analysis. The inclination of the maxillary incisors on the occlusal plane is less than 56°, so maxillary premolar extraction could have been chosen as the treatment option. SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐ B point; ANB, A point‐nasion‐B point; AFH, anterior facial height, distance between nasion and menton; FH‐OP, FH plane to occlusal plane; Pog‐N Perp, distance between pogonion and nasion perpendicular line; FMA, Frankfort mandibular plane angle; U1‐FH, long axis of maxillary central incisor to FH plane; U1‐MxOP, long axis of maxillary central incisor to maxillary occlusal plane; L1‐MnOP, long axis of mandibular central incisor to mandibular occlusal plane; IMPA, incisor mandibular plane angle.

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Section V  Application of TADs in Surgical Cases

(a)

(b)

(c)

Figure 63.9  Changes in maxillary width using MARPE. (a) MARPE immediately after placement. (b) MARPE at the end of the activation period. (c) Successful expansion of maxillary can be seen.

(a)

(b)

(c)

Figure 63.10  Treatment progress. (a) Initial tooth movement. (b) Pre-surgical orthodontic treatment completed. (c) Post‐surgical orthodontic treatment.

Orthodontics, Pusan National University, has actively used  MARPE since 2013, and the extraction of maxillary premolars has been reduced by about 60% since then.

63.3  ­Advances in Post-operative Orthodontic Treatment with Application of Miniscrews in Orthognathic Surgery Patients Orthognathic surgery causes bone remodeling of the oral and maxillofacial region as well as systemic changes; therefore, it is necessary to accurately understand and deal with the changes that occur after orthognathic surgery.

63.3.1  Skeletal Relapse Immediately after Orthognathic Surgery The most common reason for skeletal relapse immediately after orthognathic surgery of mandibular prognathism is the clockwise rotation of proximal segments of the mandible. Relapse also occurs when the amount of proximal segment displacement is large or posterior displacement of the condyle on the glenoid fossa is too great. The repositioning of the muscles attached to the mandibular body and ramus affects the relapse. A pterygomasseteric sling attached on the gonial angle exerts a force on the mandible in the anterosuperior direction. The suprahyoid muscle group, which attaches on the distal segment of the ramus, causes the mandible to move in an anteroinferior direction and

Chapter 63  Miniscrew Usage in Skeletal Class III Malocclusion Patients

Figure 63.11  Post‐treatment photographs. Facial asymmetry was improved, and occlusal relations were symmetrically and stably formed. Norm

Initial

Final

SNA (°)

81.6

85.4

85.4

SNB (°)

79.1

85.4

84.3

ANB (°)

2.4

0.0

1.1

AFH (mm)

127.4

142.5

143.0

FH-OP (°)

13.0

4.7

3.3

Pog-N Perp (mm)

–1.8

1.5

2.3

FMA (°)

25.0

23.1

22.8

U1-FH (°)

116.0

124.2

116.4

U1-MxOP (°)

56.0

51.3

58.7

L1-MnOP (°)

65.0

68.5

68.9

IMPA (°)

95.0

94.8

90.1

Figure 63.12  Post‐treatment lateral cephalogram. The inclination of the maxillary and mandibular incisor with respect to the occlusal plane is 58.7° and 68.9° respectively. These are within the appropriate range.

rotate clockwise (relapse) (Figure 63.13) [20]. This type of relapse has been reported in 43.7% of one‐jaw surgeries and 53.4% in two‐jaw surgeries [21]. Therefore, the most serious side effect of interdental fixation with surgical archwires is skeletal relapse due to the transmission of adverse forces as

mentioned above wholly to the teeth [11]. When the teeth are firmly fixed, the forces from skeletal relapse will act as an orthodontic force on the teeth. Particularly when fixation of proximal and distal segments of the mandible is done with wire fixation or with non‐rigid intraoral vertical

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Section V  Application of TADs in Surgical Cases

Figure 63.13  Skeletal response immediate after orthognathic surgery. Red arrows indicate pull of the muscles of mastication on the proximal and distal segments.

ramus osteotomy (IVRO) surgery, the abnormal orthodontic force may last for six to eight weeks because of IMF during bone healing [22]. Ueki et al. [23] first described the use of miniscrews for IMF with orthognathic surgery, and they reported a significant difference in anterior facial height six months after surgery in cases where miniscrews were used vs. where dental fixation was used.

63.3.2  Regional Acceleratory Phenomenon Bogoch et al. [24] reported a fivefold increase in new cancellous bone without a change in bone volume after four weeks of osteotomy in the femoral condyle of a rabbit.

Such localized acceleration of bone remodeling is suggested to be evidence of a regional accelerating phenomenon proposed by Frost. This phenomenon can also be observed both in the maxilla and mandible after orthognathic surgery. Park et  al. [25] reported that cortical punching performed in the maxilla of rats resulted in accelerated orthodontic tooth movement, and reverse transcription polymerase chain reaction (RT‐PCR) showed that cortical punching stimulated the expression of OPG, RANK, and RANKL in the periodontal tissue by two to three times during tooth movement. It is argued that post-operative orthodontic tooth movement should be performed early in order to achieve the desired amount of tooth movement in a short period of time using the regional acceleratory phenomenon after orthognathic surgery [26]. However, optimal orthodontic force might result in excessive force due to increased bone metabolism after orthognathic surgery, which often leads to extrusion of teeth, making it difficult to form a stable vertical dimension of occlusion (Figure 63.14). In addition, it is recommended to refrain from applying orthodontic force early after orthognathic surgery because Class III elastics applied directly to the teeth to prevent a skeletal relapse after orthognathic surgery might cause undesirable tilting of the teeth. This is also the reason why IMF using miniscrews after orthognathic surgery is more advantageous.

63.3.3  Physical Therapy Physical therapy should be initiated at some point after orthognathic surgery to rehabilitate the mandible movement, regardless of the method of fixation [27]. When rigid fixation is used, physical therapy is initiated at one week after surgery, whereas when non‐rigid fixation is used, it

Figure 63.14  Side effect of the surgical archwire fixation. During the surgery, some of the brackets on the anterior teeth were debonded due to strong IMF force, and other incisors (arrows) on which the brackets were not debonded extruded in the alveolar socket.

Chapter 63  Miniscrew Usage in Skeletal Class III Malocclusion Patients

­ ifferences attributable to one or the other type of fixad tion, except for incisor overbite. Incisor overbite increased moderately in both groups during the post‐surgical orthodontic treatment but the increase was slightly more in the wire fixation group than in the miniscrew group. Overall, the results suggest that miniscrew fixation is not less effective clinically than wire fixation. This means that a clinician can choose the fixation type depending on the individual case (e.g. miniscrew fixation may be more useful in a surgery‐first approach without orthodontic bracket bonding, or in cases where the use of surgical archwire would be difficult).

Figure 63.15  At the beginning of post-operative physical therapy, when the elastics are applied directly to the surgical archwire, there is a risk of tooth extrusion.

begins three weeks after initial fixation of the mesial and distal segments. Abnormal tooth movement can occur during dental fixation when elastics are used to properly guide the opening and closing movement of the mandible. During the post-operative period, tooth movement is accelerated due to the surgery. Therefore, rather than applying guiding elastics on dental fixation, miniscrew fixation may be the resolution to maintain the surgical results as they are (Figure 63.15).

63.5  ­Protocol for Miniscrew Fixation Miniscrews (diameter, 2.0 mm; length, 8 mm; Dual Top Anchor System; Jeil Medical, Seoul, South Korea) for IMF were placed directly with a hand driver by the maxillofacial surgeons using the self‐drilling method under general anesthesia during orthognathic surgery. For each patient, 12 miniscrews were placed on the buccal alveolar bone of the mandible and maxilla on both right and left sides, including the sites between the central incisors and lateral incisors, between canines and the first premolars, and between the second premolars and the first molars (Figure  63.16). During the first one or two months after orthognathic surgery, guiding elastics were applied on the miniscrews. Subsequently, the miniscrews were removed without anesthesia on an outpatient basis by the orthodontist.

63.4  ­Miniscrews vs. Surgical Archwires for IMF After Orthognathic Surgery

63.6  ­Summary

Son et  al. [28] evaluated the difference between mini­ screws and surgical archwires for IMF after orthognathic surgery. The purposes of this study were (i) to investigate the skeletal and dental changes that occurred during post-operative orthodontic treatment involving the use of miniscrews for IMF, and (ii) to compare the use of miniscrew fixation and surgical archwire fixation for IMF in adult patients who had Class III malocclusion and had undergone maxillomandibular surgery. The changes in cephalometric values after two‐jaw orthognathic surgery were compared between the two groups of patients – one with miniscrew fixation and the other with wire fixation. The results showed that there were no dental change

The use of miniscrews for IMF provides many benefits to patients and surgeons including (i) quick and easy insertion, (ii) compatibility with any plating system, (iii) ideal for use in cases involving heavily restored teeth, (iv) ease of maintenance of gingival health compared to when arch bars and eyelet wires are used, and (v) easy and painless removal without anesthesia on an outpatient basis. Additionally, orthodontic miniscrews can be used as anchors for elastic traction. However, clinicians need to be aware that iatrogenic injury to dental roots is the most common complication associated with the use of miniscrews, and take appropriate steps to avoid this complication.

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Section V  Application of TADs in Surgical Cases

(a)

(b)

(c)

(d)

Figure 63.16  Miniscrew fixation on the panoramic films and CBCT: (a) panoramic view; (b) right oblique view; (c) frontal view; (d) left oblique view.

­References 1 Rossouw PE, Buschang PH. Temporary orthodontic anchorage devices for improving occlusion. Orthod Craniofac Res. 2009;12:195–205. 2 Reynders R, Ronchi L, Bipat S. Mini‐implants in orthodontics: a systematic review of the literature. Am J Orthod Dentofacial Orthop. 2009;135:564.e1–19. 3 Ren Y. Mini‐implants for direct or indirect orthodontic anchorage. Evid Based Dent. 2009;10:113. 4 Li F, Hu HK, Chen JW, et al. Comparison of anchorage capacity between implant and headgear during anterior segment retraction. Angle Orthod. 2011;81:915–922. 5 Lai EH, Yao CC, Chang JZ, et al. Three‐dimensional dental model analysis of treatment outcomes for protrusive maxillary dentition: comparison of headgear, miniscrew,

and miniplate skeletal anchorage. Am J Orthod Dentofacial Orthop. 2008;134:636–645. Yao CC, Lai EH, Chang JZ, et al. Comparison of treatment 6 outcomes between skeletal anchorage and extraoral anchorage in adults with maxillary dentoalveolar protrusion. Am J Orthod Dentofacial Orthop. 2008;134:615–624. 7 Tseng YC, Chen CM, Chang HP. Use of a miniplate for skeletal anchorage in the treatment of a severely impacted mandibular second molar. Br J Oral Maxillofac Surg. 2008;46:406–407. 8 Park W, Park JS, Kim YM, et al. Orthodontic extrusion of the lower third molar with an orthodontic mini implant. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;110:e1–6.

Chapter 63  Miniscrew Usage in Skeletal Class III Malocclusion Patients

9 Choi SH, Shi KK, Cha JY, et al. Nonsurgical miniscrew‐ assisted rapid maxillary expansion results in acceptable stability in young adults. Angle Orthod. 2016;86:713–720. 10 Suzuki H, Moon W, Previdente LH, et al. Miniscrew‐ assisted rapid palatal expander (MARPE): the quest for pure orthopedic movement. Dental Press J Orthod. 2016;21:17–23. 11 Miloro M, Ghali GE, Larsen PE, Waite PD. Principle of Oral and Maxillofacial Surgery, 2nd edn. Toronto: BC Decker, 2004, pp. 1118–1133. 12 Arnett GW, Jelic JS, Kim J, et al. Soft tissue cephalometric analysis: diagnosis and treatment planning of dentofacial deformity. Am J Orthod Dentofacial Orthop. 1999;116:239–253. 13 Arnett GW, Bergman RT. Facial keys to orthodontic diagnosis and treatment planning. Part I. Am J Orthod Dentofacial Orthop. 1993;103:299–312. 14 Hernández‐Alfaro F, Guijarro‐Martínez R. On a definition of the appropriate timing for surgical intervention in orthognathic surgery. Int J Oral Maxillofac Surg. 2014;43:846–855. 15 Arnett GW, Gunson MJ. Facial planning for orthodontists and oral surgeons. Am J Orthod Dentofacial Orthop. 2004;126:290–295. 16 Arnett GW, McLaughlin RP. Facial and Dental Planning for Orthodontists and Oral Surgeons. St. Louis, MO: CV Mosby, 2004, pp. 241–243. 17 Arnett GW, Bergman RT. Facial keys to orthodontic diagnosis and treatment planning – part II. Am J Orthod Dentofacial Orthop. 1993;103:395–411. 18 Georgalis K, Woods MG. A study of Class III treatment: orthodontic camouflage vs orthognathic surgery. Aust Orthod J. 2015;31:138–148. 19 Park HM, Lee YK, Choi JY, Baek SH. Maxillary incisor inclination of skeletal Class III patients treated with

extraction of the upper first premolars and two‐jaw surgery: conventional orthognathic surgery vs surgery‐ first approach. Angle Orthod. 2014;84:720–729. 20 Franco JE, Van Sickels JE, Thrash WJ. Factors contributing to relapse in rigidly fixed mandibular setbacks. J Oral Maxillofac Surg. 1989;47:451–456. 21 Politi M, Costa F, Cian R, et al. Stability of skeletal class III malocclusion after combined maxillary and mandibular procedures: rigid internal fixation versus wire osteosynthesis of the mandible. J Oral Maxillofac Surg. 2004;62:169–181. 22 Ayoub AF, Millett DT, Hasan S. Evaluation of skeletal stability following surgical correction of mandibular prognathism. Br J Oral Maxillofac Surg. 2000;38:305–311. 23 Ueki K, Marukawa K, Shimada M, et al. The use of an intermaxillary fixation screw for mandibular setback surgery. J Oral Maxillofac Surg. 2007;65:1562–1568. 24 Bogoch E, Gschwend N, Rahn B, et al. Healing of cancellous bone osteotomy in rabbits – Part I: regulation of bone volume and the regional acceleratory phenomenon in normal bone. J Orthop Res. 1993;11:285–291. 25 Park WK, Kim SS, Park SB, et al. The effect of cortical punching on the expression of OPG, RANK, and RANKL in the periodontal tissue during tooth movement in rats. Korean J Orthod. 2008;38:159–174. 26 Lee TC, Staines A, Taylor D. Bone adaptation to load: microdamage as a stimulus for bone remodelling. J Anat. 2002;201:437–446. 27 Bell WH, Gonyea W, Finn RA, et al. Muscular rehabilitation after orthognathic surgery. Oral Surg Oral Med Oral Pathol. 1983;56:229–235. 28 Son S, Kim SS, Son WS, et al. Miniscrews versus surgical archwires for intermaxillary fixation in adults after orthognathic surgery. Korean J Orthod. 2015;45:3–12.

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64 Orthodontic Biomechanics with Miniplates in the Surgery‐first Orthognathic Approach Jorge Faber1,2, Carolina Faber2, and Patricia Valim2 1

 Postgraduate Program in Dentistry, University of Brasília, Brasília, Brazil  Private Practice, Brasília, Brazil

2

64.1 ­Introduction Conventional surgical orthodontic treatment has been recently challenged by another treatment alternative: the surgery‐first (SF) protocol [1]. SF eliminates the conventional pre-operative orthodontic treatment (Pre-op Ortho) for orthognathic surgery, allowing the patient to be operated on within a short time after the start of orthodontic treatment. There are two main ways to perform SF. In the first, the surgeon rotates the occlusal plane in order to favor the correction of the skeletal deformity [2, 3]. In general, the occlusal plane is rotated counterclockwise in Class II dentofacial deformities, whereas it is rotated clockwise in Class IIIs. The rotations were introduced by surgeons so that the orthognathic surgeries could be made even when the Pre-op Ortho was not able to eliminate the dental compensations for the dentofacial deformity. Later, this approach was expanded to the maxillomandibular advancement for sleep apnea patients, when the conventional preparation for orthognathic surgery is iatrogenic, unless the patient has continuous positive airway pressure (CPAP) therapy during Pre-op Ortho. However, rotation of the occlusal plane can result in less than ideal esthetic results, because of dental exposure. Another way to perform the SF protocol is to use the skeletal anchorage to perform the same dental movements that would be made in a Pre-op Ortho [1, 4]. This way of planning and performing the treatment transfers responsibility for the final occlusion to the orthodontist. It requires expertise on how to use skeletal anchorage, mainly but not exclusively miniplates. The skeletal anchorage is placed during the orthognathic surgery.

The aim of this chapter is to demonstrate the orthodontic biomechanics with the application of skeletal anchorage miniplates in SF orthognathic surgery.

64.2  ­Class III Treatment with SF 64.2.1  General Considerations The dental movements performed for decompensation in treatment of Class III dentofacial deformities are, basically, the same as those used to treat a Class II malocclusion [5, 6]. When Class III dentofacial deformities are corrected through a SF approach, the general goal of the surgical procedure is  to transform the Class III malocclusion into a Class II ­malocclusion. The maxilla and mandible will be in adequate positions, but the teeth will be in a Class II position. The magnitude of the resulting Class II malocclusion depends on the intensity of the dental compensations. The more intense dental compensation a Class III patient presents, the greater will be the resulting Class II. The increased positive overjet generated during surgery will be corrected with either protraction of the mandibular teeth, or retraction of the maxillary teeth, or both. The need for and positions of skeletal anchorages are determined according to the cephalometric and clinical characteristics of each case. Figure 64.1 shows the most common orthodontic biomechanics performed after surgery in Class III treatment. When the mandibular incisors are well inclined and the maxillary incisors are flared, which is particularly common in patients who only have maxillary deficiency [7, 8], only maxillary arch decompensation is needed. Typically, this is done with retraction miniplates installed in the molar region, about 5 mm above the orthodontic archwire. It is

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section V  Application of TADs in Surgical Cases

(a)

(b)

(c)

(d)

Figure 64.1  Most common mechanics with miniplates when one treats a Class III dentofacial deformity. (a) This is implemented when the mandibular incisors have proper inclination and the maxillary incisors are protrusive. (b) This is used when the maxillary incisors have normal inclination and the mandibular incisors are retroclined. Note that the force must pass at the level of the center of resistance of the mandibular molars. (c) This is a combination of the two previous alternatives. There is retroclination of the mandibular incisors and proclination of maxillary incisors. (d) This is a less common condition: both maxillary and mandibular incisors show normal inclination. In these cases, the dental relationship obtained in the operating room is Class I.

interesting to note that distalization of the entire maxillary dentition tends to incline the molars distally and this change causes extrusion of the anterior teeth. The application of the retraction force from the miniplates straight to the archwire (Figure 64.1a), not parallel to it, mitigates the extrusion of the anterior teeth and provides good incisor vertical control. When the maxillary incisors are well inclined and the mandibular incisors are retroclined, only mandibular teeth need to be projected with the skeletal anchorage placed at the level of the center of resistance of the mandibular molars (Figure 64.1b). In practice, both maxillary and mandibular incisors might simultaneously present inadequate inclinations due to compensation for skeletal deformities. In this situation, mandibular protraction can be carried out together with maxillary retraction using skeletal anchorage (Figure 64.1c). Occasionally, we come across a case where there is an anteroposterior discrepancy with negative overjet, but both maxillary and mandibular incisors have adequate buccolingual inclinations (Figure  64.1d). These cases do not

require any skeletal anchorage and tend to have short treatment time. In these situations, patients end the surgery in Class I malocclusion, rather than in Class II malocclusion as in most SF treatments of Class III deformities.

64.2.2  Treatment of Class III Dentofacial Deformity Class III dentofacial deformities can be treated with SF. The main limitations for surgery at the beginning of treatment are a severe curve of Spee and vertical asymmetries. The curve of Spee can make it difficult to establish a predictable mandible position. When asymmetries are the challenge, it is difficult to make a proper evaluation of the occlusal plane due to the differences in tooth height. In both cases, a presurgical alignment and leveling stage is highly recommended, very often with the use of skeletal anchorage [4]. The primary objective of skeletal anchorage in the treatment of Class III deformities is to eliminate or mitigate existing dental compensations for skeletal deformity. In SF, this step is performed after surgery.

Chapter 64  Biomechanics with Miniplates in the Surgery-first Approach

Case 64.1  The male patient, 26 years 8 months when he started treatment, had as chief complaints facial esthetics and  poor mastication. He had an anteroposterior maxillary deficiency and a mandibular prognathism ­ (Figures  64.2a–c and 64.3a,b). The inclination of the maxillary incisors was satisfactory, but the mandibular

incisors were retroclined (Figures  64.2a and 64.3a). Two skeletal anchorage miniplates were used in the mandible for protraction of all the mandibular teeth (Figure 64.3b,c). When the forward movement of the mandibular or maxillary dentition is required, it is very important to

(a)

(b)

(c)

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Figure 64.2  Case 64.1: Facial and intraoral views of the patient before (a–f) and after (g–l) treatment. The severe retroclination of the mandibular incisors improved. The two anchorage miniplates depicted in the final photos were used to mesialize the mandibular dentition.

(Continued )

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Figure 64.3  Case 64.1: (a, b) Lateral cephalograms before and after treatment. The detail in (b) is represented in (c). The force is applied from the miniplate to the molar tube by means of bent hooks made with rectangular stainless steel wire. (d) This shows the force being applied straight to the tube, which tends to tip the molar and intrude the anterior segment as in (e). (f) This shows the resulting anterior open bite of such improper approach.

place miniplates at the level of the center of resistance of the first molars (Figure  64.3c). The mesialization forces are applied from the miniplates to the first molars by means of nickel–titanium (NiTi) coil springs. In addition, bent hooks of rectangular stainless steel wire are attached to the double tubes of first molars for proper level of force. This permits bodily mesialization of molars,

64.3  ­Class II Treatment with SF 64.3.1  General Considerations The tooth movement implemented in surgery cases of patients with Class II dentofacial deformities is, in essence, similar to the compensation of teeth carried out when Class III patients do not want to undergo orthognathic surgery (i.e. retraction of the mandibular incisors).

without tipping of teeth and consequent rotation of the occlusal plane. If the NiTi coil spring is applied directly from the miniplates to the molar tube without the hook (Figure  64.3d), the occlusal plane rotates, resulting in molar tipping and intrusion of the anterior segment (Figure 64.3e,f).

However, it is important to take into consideration that many of the Class II individuals present with Obstructive Sleep Apnea Syndrome (OSAS). If this is the case, one has  to compromise ideal esthetic goals in favor of more  ­pronounced maxillomandibular advances. Usually patients with OSAS undergo maxillary advancements around 8–10 mm and mandibular advancements greater than 10 mm.

Chapter 64  Biomechanics with Miniplates in the Surgery-first Approach

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Figure 64.4  Most common orthodontic mechanics for post-operative treatment of Class II deformities. (a) The maxillary incisors show normal inclination and the proclined mandibular incisors are improved by retraction of the whole mandibular dentition. (b) Both the maxillary and mandibular anterior teeth are proclined. The bimaxillary dentoalveolar protrusion is corrected by means of miniplates. (c) The anterior teeth have good inclinations and there is no significant spacing or crowding, so there is no need for skeletal anchorage.

64.3.2  Orthodontic Mechanics in Class II Treatment with SF A post-operative Class III dental relationship is the most common occlusion when treating a patient with a Class II deformity with SF (Figure 64.4a). Contrary to what patients intuitively expect at the beginning of treatment, the patient’s appearance after surgery is not Class III, but rather normalization of the facial profile with a slight projection of the lower lip. The Crossbite can be avoided in many cases, with counterclockwise rotation of the occlusal plane [2]. Although this approach actually avoids crossbites, it could excessively decrease the exposure of the upper incisors, and this may be esthetically unfavorable for the patient [9]. Several individuals who have Class II deformities have significant protrusions in the maxillary and mandibular arches. In such cases, the retraction of all maxillary and mandibular dentition may be indicated after orthognathic surgery (Figure  64.4b). Therefore, miniplates should be placed on both maxillary and mandibular arches, at the region of first molars.

Some patients with Class II deformities have adequate dental inclinations and positions in the anterior region. If this is the case, there is no indication of anterior tooth movement in the anteroposterior direction, and no miniplate should be applied (Figure 64.4c).

64.3.3  Treatment of Class II Dentofacial Deformity Usually, patients who present Class II deformities have significantly proclined mandibular incisors. Often the maxillary incisors also show pronounced protrusion. The maxillomandibular skeletal discrepancy is often greater than the dental discrepancy. The latter can be accessed through the Class II molar relationship and marked overjet. During Pre-op Ortho for orthognathic surgery, the orthodontist increases the patient’s overjet, thus creating greater space for mandibular advancement. In cases of SF, the same decompensation of teeth is performed after surgery with skeletal anchorage.

Case 64.2  The chief complaint for this female patient, 36 years 4 months old at the beginning of treatment, was about facial esthetics. There was no obstructive sleep apnea syndrome and her medical history was not relevant for the orthodontic surgical treatment. Her face was symmetrical, with a convex profile and adequate exposure of maxillary incisors when smiling (Figure 64.5). She had a Class II Division 2 subdivision malocclusion.

The maxilla was well positioned, and the mandible was retrognathic (Figure 64.6a). The mandibular incisors were proclined 10°, while the maxillary incisors were in an acceptable position. Thus, the treatment plan involved mandibular advancement through bilateral sagittal split  osteotomy and retraction of mandibular incisors by  10°  –  about 3 mm  –  using skeletal anchorage miniplates. (Continued )

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After surgery, the patient had an anterior crossbite according to the plan (Figure  64.6b,c). The anchorage miniplates were placed as seen in Figure  64.6d. They

allowed correction of the anterior crossbite by distalization of the mandibular dentition (Figures  64.5g–l and 64.6e,f).

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Figure 64.5  Case 64.2: Facial and intraoral views of the patient before (a–f) and after (g–l) treatment. Note the improvement of Class II skeletal and dental relationships.

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Figure 64.6  Case 64.2: Lateral cephalograms of the patient before surgery (a); immediately after surgery (b); and after treatment (e). (a) The mandibular incisors were proclined 10°, or 3 mm. (b, c) These demonstrate that the surgery resulted in an anterior crossbite that would allow the incisors to be retracted 3 mm. This retraction was performed using the miniplates as anchorage, as detailed in (d) (arrows). (e, f) Note the improvement in the skeletal and dental relationships.

64.4 ­Conclusions The treatment of dentofacial deformities with SF depends intrinsically on orthodontic planning. Orthodontists must

have proper knowledge of surgical planning, as well as a comprehensive understanding of how to use skeletal anchorage, mainly miniplates.

R ­ eferences 1 Nagasaka H, Sugawara J, Kawamura H, Nanda R. “Surgery first” skeletal Class III correction using the skeletal anchorage system. J Clin Orthod. 2009;43:97–105. 2 Brevi BC, Toma L, Pau M. Counterclockwise rotation of the occlusal plane in the treatment of obstructive sleep apnea syndrome. J Oral Maxillofac Surg. 2011;69:917–923.

3 Zaghi S, Holty JEC, Certal V, et al. Maxillomandibular advancement for treatment of obstructive sleep apnea ameta‐analysis. JAMA Otolaryngol – Head Neck Surg. 2016;142:58–66. 4 Faber J. Anticipated benefit: a new protocol for orthognathic surgery treatment that eliminates the need

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for conventional orthodontic preparation. Dental Press J Orthod. 2010;15:144–157. 5 Larson BE. Orthodontic preparation for orthognathic surgery. Oral Maxillofac Surg Clin North Am. 2014;26:441–58. 6 McNeil C, McIntyre GT, Laverick S. How much incisor decompensation is achieved prior to orthognathic surgery? J Clin Exp Dent. 2014;6:e225‐e229. 7 Arnett GW, Bergman RT. Facial keys to orthodontic diagnosis and treatment planning. Part I. Am J Orthod Dentofacial Orthop. 1993;103:299–312.

8 Arnett GW, Bergman RT. Facial keys to orthodontic diagnosis and treatment planning. Part II. Am J Orthod Dentofacial Orthop. 1993;103:395–411. 9 Parrini S, Rossini G, Castroflorio T, et al. Laypeople’s perceptions of frontal smile esthetics: a systematic review. Am J Orthod Dentofacial Orthop. 2016;150:740–750.

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65 Biomechanical Mistakes Related to the Use of TADs Ki Beom Kim1 and Guilherme Thiesen1,2 1 2

Department of Orthodontics, Center for Advanced Dental Education, Saint Louis University, St. Louis, MO, USA Private Practice, Florianópolis, SC, Brazil

65.1 ­Introduction A correct orthodontic treatment plan must include the study of the anchorage unit. This means that biomechanics in orthodontics does not always aim to just move teeth. Sometimes the clinician may plan to maintain the position of certain elements in the dental arch or to utilize groups of teeth that comprise an anchoring unit in order to achieve the desired movement of other elements [1, 2]. In order to facilitate this task, temporary anchorage devices (TADs) were developed and are now widely used in orthodontics, leading to an expansion of the possibilities in the envelope of discrepancy for orthodontic tooth movement. TADs include miniplates, miniscrews, endosseous implants, and onplants, but miniscrews are the most often used TADs in orthodontics. TADs were created as an effective alternative in anchorage control because they transmit reaction forces to the bone instead of to other teeth, as is the case with conventional anchoring mechanisms. This improves the predictability for complex cases, reducing the need for patient compliance [2–5]. Nowadays, these devices are incorporated into orthodontic practices due to the various advantages they offer when compared to other anchoring systems. These advantages include reduced size, ease of installation in several areas of bone tissue, resistance to orthodontic forces, possibility of applying immediate loads, easy insertion and removal, and low cost and use with different orthodontic mechanics [1, 6–9]. TADs are deemed successful when they remain stable until the desired orthodontic movement has been achieved, which minimizes undesired side effects to the adjacent teeth [1, 10–12]. Studies have shown that success rates range from 70% to 100% [9, 11, 13–16].

Several factors can influence the success or failure of TADs as orthodontic anchorage, but studies do not present consensus on these variables. Some of these factors are related to the device itself (its type, shape, length, and diameter), some are related to the clinician (clinical experience, loading time, place of insertion, location in relation to dental roots, type of movement, and applied biomechanics on the screws), and some to the patient (age, gender, thickness and type of mucosa, hygiene care, etc.) [7, 17–27]. Many papers in orthodontic literature focus on the structural characteristics of TADs and on the “safe places” to insert them  –  trying to increase their success rates. However, little attention has been given to the most important aspect: orthodontic biomechanical planning and the basic principles of anchorage that can help clinicians use these devices effectively. It is important to keep in mind that TADs, like traditional anchorage devices which have been used for centuries, need an experienced professional to get the most out of them and really broaden the envelope of discrepancy for tooth movement. The main goal of this chapter is to present clinical situations with biomechanical mistakes related to the use of TADs in orthodontics.

65.2 ­Biomechanical Problems Related to TADs Positioned in the Palatal Region A transpalatal arch (TPA) supported by TADs is one of the most common ways to achieve maximum anchorage in a maxillary arch. Figure 65.1 shows a typical example, where two TADs were placed in the paramedian palatal region to reinforce anchorage. Two helixes of TPA were tied to the TADs with stainless steel ligatures. Two ­buttons

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Figure 65.1  (a–e) Pre-treatment intraoral photographs of a case treated with extraction of the upper premolars. (f) Two palatal miniscrews were placed in the paramedian palatal region to reinforce anchorage. (g–l) The TPA was tied to the miniscrews with stainless steel ligatures until the necessary anterior retraction was achieved. (m–q) Post‐treatment intraoral photographs demonstrating the efficacy of the biomechanical approach.

were bonded on the lingual side of the maxillary canines. In order to prevent rotation of the canines as they were retracted, both buccal and lingual retraction forces were applied. This figure illustrates a conventional approach with TADs used to stabilize teeth connected to a TPA. However, even this approach can lead to problems in maintaining anchorage, as will be seen in the next cases. Figure  65.2a–f shows an example where one TAD was placed in the midpalatal region. A TPA was bonded to the maxillary second premolars and was tied to the TAD with stainless steel ligatures. Open coil springs were placed between the maxillary second premolars and the first molars to distalize the maxillary first molars. The spaces were opened between the first molars and the second premolars. However, as the maxillary first molars moved distally, the maxillary second premolars moved mesially. The same problem occurred in the next example (Figure  65.2g–l), in which soldering caps were used to connect a TPA to a TAD. A TPA with a cap was bonded to the maxillary first premolars to distalize them. As the maxillary first molars were distalized, the maxillary first premolars moved mesially. While the TAD seemed stable, the TAD‐supported TPA was not able to prevent the anchorage loss.

The reason for the anchorage loss in these examples was slack in the connection between the TPA and the head of the TAD, even though soldering caps were incorporated into the TPA. Since the head of the TAD was round, the TPA that was connected with a soldering cap tipped forward because the line of force applied to the teeth was below the center of resistance, which produced a rotational moment. Anchorage loss can also occur when a TAD‐supported TPA is connected to the upper molars in cases where maximum retraction of the anterior teeth is necessary. Even using a large‐diameter archwire, heavy retraction force can deflect the TPA and cause anchorage loss (Figure 65.2m,n). This problem is illustrated in Figure 65.2o–w, where a TAD‐supported TPA was used to retract the maxillary canines. Maxillary first molars were mesially tipped and lost anchorage. If TADs are placed in the posterior area of the palate and the TPA is designed very close to them (Figure 65.3a), they can be rigidly secured with flowable composite (Figure 65.3b). As seen in this example, when heavy retraction forces are applied with a small‐diameter flexible archwire, flowable composite by itself is unable to resist the rotational moment. Therefore, a TAD‐supported TPA connected to the maxillary first molar can move mesially due to anchorage loss, since the force for space closure is applied

Chapter 65  Biomechanical Mistakes Related to the Use of TADs

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Figure 65.2  (a–c) A TPA bonded to the maxillary second premolars was tied to a palatal TAD to distalize the maxillary first molars using open coil springs. (d–f) Anchorage loss occurred in the maxillary second premolars connected to the TAD‐supported TPA, demonstrated here as mesialization of the premolars. (g–i) Distalization of maxillary first molars with open coil springs and an anchorage unit with a TPA presenting soldering caps connected to a palatal TAD. (j–l) Anchorage loss occurred during distalization of maxillary first molars, although the TAD remained stable. Slack in the connection between the TPA and TAD, as well as the flexibility of the TPA wire, explains the anchorage loss. (m) A TAD‐supported TPA can be connected to the maxillary first molars aiming maximum anchorage in cases of premolar extractions. (n) Anchorage loss can still occur since the connection between the TPA and the TAD may not be completely rigid, as well as flexibility of the TPA wire can allow some movement of the maxillary first molars. (o–q) Retraction of maxillary canines in a case of first premolar extractions, using a TAD‐supported TPA for maximum anchorage. (r–w) At the end of canine retraction some anchorage loss was noticed, associated with bending of the archwire and opening of the bite in the posterior region.

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Figure 65.2  (Continued)

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Figure 65.3  (a) A TPA designed close to palatal TADs. (b) It was fixed with flowable composite to miniscrews inserted in the posterior palatal region, in order to provide a rigid fixation. (c–i) This TAD‐supported TPA fixed with flowable composite can still lose anchorage, especially when heavy forces are applied.

Chapter 65  Biomechanical Mistakes Related to the Use of TADs

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Figure 65.4  (a) When the TPA is ligated to an anterior TAD with stainless steel ligatures, the way to institute this ligation method must be carefully addressed. (b) If the stainless steel ligature produces a mesial force, anchorage loss is prone to occur. (c) If the TPA is designed to pass mesially to the TAD, the stainless steel ligature will produce a distal force component. (d) The distal force produced by the ligature tied to an anteriorly positioned TPA can even produce a distal movement of the maxillary molars connected to this TPA. (e) If the fixation provided by stainless steel ligatures is compromised, the TPA will lose its skeletal anchorage element and move toward the forces applied to it. (f) TADs can be placed through a ring connected to a TPA to provide better fixation. (g) Even with rings soldered in TPA, the connection is not completely rigid. (h) Some anchorage loss may occur and the TPA may submerge into soft tissues.

occlusally to the center of resistance. In this case, the molars will tip forward (Figure 65.3c–i). If a TPA is designed distal from the TADs and is ligated by stainless steel ligature wires to the TADs, the ligating force can move the maxillary first molars mesially. Hence, this approach may lead to anchorage loss (Figure 65.4a,b). Therefore, the TPA should be designed anterior from the TADs, so the ligation force can push the TPA backward and the maxillary first molars will move slightly distally (Figure 65.4c,d). However, if the steel ligature ties loosen or break, anchorage will be lost as shown in Figure 65.4e. TADs can be placed through a ring connected to a TPA (Figure  65.4f). Even in this configuration, there can be minor anchorage loss as seen in Figure 65.4g,h where the TPA was slightly submerged into soft tissues.

A Nance button supported by TADs can also be used. In these cases, the TADs should be placed before the pick‐up impression or scanning is obtained. Holes in the acrylic can be made in the position of the inserted palatal TADs, so that they can sit on top of the TADs’ exposed heads. TADs can be secured with flowable composite (Figure 65.5a,b). If miniscrews are positioned at 90° to the applied retraction force, the entire anterior surface of the miniscrew can resist the mesial force along with the acrylic button – and the chance of anchorage loss is minimal (Figure 65.5c). TADs supported by an acrylic button can also be used to distalize the maxillary first molars. One of the problems that  may arise is the difficulty in evaluating the stability of the  TADs because they are under the acrylic button. In Figure  65.5d–i, a good amount of activation for the

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Figure 65.5  (a, b) TAD‐supported Nance buttons are usually built with two holes in the acrylic, filled with flowable composite when positioned in the palate. (c) If the TAD is inserted perpendicular to the direction of the forces applied to it, its whole surface will resist this force and anchorage will be reinforced. (d–g) TAD‐supported Frog appliance (miniscrew‐ supported molar distalization appliance). (h) Impingement of the palatal tissue from the instability of the TADs during molar distalization. (i) The miniscrews became loose, but the presence of the acrylic button in the palate camouflaged their instability.

­ istalization can be seen, but there was not much movement d of the maxillary first molars. In fact, both of the TADs ­loosened and all the distalization force was delivered to the soft tissue, which caused a serious soft tissue impingement.

Figure 65.6  (a) Distalization of maxillary molars can be done with a TPA presenting an anterior extension with hooks, associated with posterior TADs applying a distal force to them. (b) Mesial rotation of the maxillary first molars connected to the TPA is commonly seen, since the force is applied palatal to the center of resistance of these teeth. (c–e) If a patient presents with a high‐vaulted palate, distal force may be applied apical to the center of resistance of the molars and the TPA might tip, causing it to impinge into the palate soft tissue.

Distalization of the maxillary molars can also be performed with palatal TADs by applying forces to anterior hooks incorporated onto a TPA. Although this approach is efficient for many cases, it can lead to some problems (Figure 65.6). One common problem is mesial rotation of the maxillary first molars connected to the TPA, since the force is applied palatally to their center of resistance in an occlusal view. Another problem that may occur is tipping of the TPA, which causes impingement into the palate, especially when a patient has a high‐vaulted palate and the force is applied apically to the center of resistance of the molars being distalized.

65.3 ­Biomechanical Problems Related to TADs Positioned in the Buccal Region The most common place for buccal placement is the interradicular space between the maxillary first molar and second premolar. As illustrated in Figure  65.7a–f, as space

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Figure 65.7  (a–f) TADs inserted buccally between the maxillary first molar and second premolar to retract anterior teeth after first premolar extractions. Space closure mechanics may lead to extrusion and overbite increase. (g) Space closure with the TAD inserted buccally between the maxillary first molar and second premolar may provide good anchorage control, but some important aspects must be considered. (h–p) Application of excessive forces, a small‐diameter archwire, or the combination of both can deflect the archwire and lead to anchorage loss, a posterior openbite and extrusion of the anterior teeth. (q) Using long hooks for applying the retraction forces close to the center of resistance tends to minimize side effects.

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Figure 65.8  (a) A special buccal TAD with a hole in its head can be used so the archwire can be inserted directly into it, thereby avoiding side effects in the molars. (b–j) A TAD with a hole in its head allows the archwire to be inserted into it, instead of in the bracket slots of posterior teeth. Intramaxillary and intermaxillary mechanics can be applied to the TAD without risking anchorage loss. Side effects are therefore minimized in the posterior teeth and good results can be achieved predictably.

closure mechanics using buccal TADs were applied, the maxillary canines were retracted, maxillary anterior teeth were extruded, and overbite was increased. This can be caused by the application of excessive retraction forces, a small‐diameter archwire, or both. If excessive retraction force is applied to the maxillary canine with a small‐diameter archwire, deflection of the archwire (bowing) may lead to anchorage loss (Figure 65.7g–p). Using a long hook to apply the retraction force close to the center of resistance will help to

avoid such anchorage loss and unwanted maxillary incisor extrusion (Figure 65.7q). If an archwire is inserted into a hole in the miniscrew without having any appliances to the maxillary posterior teeth, Class I elastics can be used to retract the maxillary anterior teeth without the risk of anchorage loss (Figure 65.8a). This methodology is illustrated in Figure 65.8b–j, where a round stainless steel archwire was inserted into miniscrews and Class I elastics were used to retract the maxillary

Chapter 65  Biomechanical Mistakes Related to the Use of TADs

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Figure 65.9  (a, b) Whenever a cantilever is inserted directly to a miniscrew, the force system must be carefully evaluated. The moment applied to the miniscrew should not provide a force in the direction of unscrewing the device out of the alveolar bone. (c–e) As the moment was created in the same direction as the miniscrew’s insertion, the stability of the TAD was not compromised during the mechanics. (f) If specific mechanics are necessary to move a group of teeth and they produce a moment in the opposite direction to the miniscrew’s insertion, this might tend to unscrew it. A major resistance to this moment needs to be created. Using two or more miniscrews or even a bicortical miniscrew as illustrated in this picture can provide this extra stability.

anterior teeth, associated with Class III elastics used to retract the mandibular canines. An important topic to address is the way in which force is applied to the miniscrew: directly or indirectly. Direct anchorage means that the force is applied directly to the TAD by elastic chains, elastic threads, coil springs, or any other source of force. Indirect anchorage means that a device is attached to the TAD and that a force is applied to a tooth or a group of teeth from this device. When applying direct forces to a miniscrew, careful consideration must be taken regarding the force system. This is extremely relevant since moments created during force application may tend to unscrew the miniscrew. This must be avoided to prevent the miniscrew from loosening. If it is not possible to avoid using a force system with an undesirable moment, indirect anchorage is recommended. Therefore, the orthodontist must evaluate the force system applied to the miniscrew in order to avoid instability. In Figure 65.9a–e a cantilever inserted into the miniscrew was activated to correct the cant of the maxillary occlusal plane by extruding the left anterior segment, which led to an intrusive force and a clockwise moment being applied to the TAD. Since a moment was created in

the same direction as the insertion of the miniscrew, there was no major complication throughout treatment, but if this moment had been applied in the opposite direction, the miniscrew might have started to unscrew and become unstable. For these cases, a bicortical ­miniscrew should be used so the tendency to become unscrewed is minimized, and this mechanics can be instituted (Figure 65.9f). Another common mistake that clinicians often make is  when using TADs to protract posterior teeth. Figure  65.10a–f shows an example where miniscrews were placed in the interradicular space between the mandibular canine and mandibular first premolar to protract the mandibular first molar and replace the congenitally missing mandibular second premolars. Hooks were used to apply a protraction force close to the center of resistance of the mandibular first molar. As the mandibular first molars moved mesially, an anterior open bite and anterior crossbite developed. Both miniscrews loosened, so they acted as wedges and pushed the first premolars backward. This created space between the mandibular canines and first premolars. If a protraction force is applied occlusally to the center of resistance of the mandibular first molar (Figure  65.10g), the crown will tip mesially, causing

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binding between the mesial end of the molar bracket and the archwire (Figure 65.10h). This will bow the archwire and open the bite in the anterior region. Another common problem related to this case is friction from the binding caused by the protraction force, since the entire lower dentition and archwire can move mesially rather than the molar sliding through the archwire to close the space (Figure 65.10i). Figure 65.10j–o illustrates the successful mesialization of the mandibular first molar by using a large‐diameter stainless steel archwire, an extended hook close to the center of resistance, appropriate protraction forces, and “V” bends to prevent crown tipping of the mandibular first molar. Reaching the center of resistance of the ­posterior tooth using a long hook is essential to minimize the usual side effects associated with this mechanics (Figure 65.10p). Even though the hook is placed close to the center of resistance, if the mandibular arch is not leveled completely or if a small‐diameter archwire is used, the mandibular first molar crown can tip mesially and end up causing an anterior open bite and crossbite. This problem can get even worse if this mechanics is done unilaterally, since a cant in the occlusal plane can develop (Figure 65.10q–x).

In order to avoid these problems, indirect anchorage is sometimes advisable to protract posterior teeth (Figure 65.10y), because the TAD attached to the anterior teeth will prevent them from intruding and protracting, even when binding exists during mesial movement of the molars. This is extremely important because x‐ray images usually demonstrate that, even when long hooks are used (and most of times the patients do not tolerate them), they may not be able to reach the center of resistance of the posterior teeth (Figure 65.10z).

65.4 ­Conclusions Thanks to the recent development of temporary skeletal anchorage devices, it is now possible to tackle some of the most difficult tooth movements. TADs provide rigid anchorage, making orthodontic treatment more efficient without many of the unwanted side effects. In this text, common biomechanical problems and mistakes related to TADs were discussed so they can be avoided and the necessary skeletal anchorage can be achieved. Proper treatment plans along with careful mechanics planning is always essential to obtain the best orthodontic treatment results.

Figure 65.10  The protraction of posterior teeth is a difficult task in orthodontics, even when skeletal anchorage is applied. (a–c) Intraoral photographs of a case with missing mandibular second premolars, when protraction of the mandibular molars was initiated. (d–f) The most common side effects of protracting molars using TADs are tendency toward anterior open bite and anterior crossbite. (g) Protraction of posterior teeth using a TAD as direct anchorage, applying a force occlusal to the center of resistance of the molar. (h) The molar crown will tend to tip mesially, and this will produce binding between the molar bracket and archwire. This will bow the archwire and tend to create an open bite in the anterior region. (i) Another common problem with this mechanics is friction from the binding caused by the mesial force, since the entire lower dentition will move mesially. (j–m) Protraction of posterior teeth can be successfully achieved if some principles are observed. Treatment progress demonstrates good biomechanical control with the use of a large stainless steel archwire, extended hook close to the center of resistance, low protraction forces, and “V” bends incorporated into the archwire. (n, o) Post‐treatment intraoral photographs. (p) Even if long hooks are used to reach the center of resistance of the molars being protracted, this must be monitored at every office visit since there will still be a tendency for anterior open bite and anterior crossbite to develop. (q–t) Pre-treatment intraoral photographs of a case with one mandibular and two maxillary second premolars missing. (u–x) In order to protract the right mandibular first molar to close the congenitally missing mandibular second premolar space, TADs were inserted in the buccal and lingual alveolar bone distal to the first premolar. An open bite and anterior crossbite tendency can be noticed, which was exacerbated by maxillary protraction of the posterior teeth. A bigger problem in this case was the cant in the lower occlusal plane, iatrogenically produced by the asymmetric mechanics in the lower arch. (y) Indirect anchorage can be used to protract posterior teeth, since the side effects produced in the anterior region will be canceled by the TAD connected to the anterior teeth. (z) Panoramic radiograph showing that even when long hooks were used for protracting posterior teeth, they usually cannot reach to the level of the center of resistance of those teeth. Therefore, indirect anchorage is strongly recommended for these cases.

Chapter 65  Biomechanical Mistakes Related to the Use of TADs

(a)

(b)

(c)

(e)

(f)

(g)

(h)

(j)

(k)

(l)

(m)

(n)

(o)

(p)

(q)

(r)

(s)

(t)

(u)

(v)

(w)

(x)

(y)

(z)

(i)

Figure 65.10  (Continued)

(d)

729

730

Section VI  Complications with the Use of TADs

­References 1 Papadopoulos MA, Tarawneh F. The use of miniscrew implants for temporary skeletal anchorage in orthodontics: a comprehensive review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;103:e6–15. 2 Roberts‐Harry D, Sandy J. Orthodontics. Part 9: anchorage control and distal movement. Br Dent J. 2004;196:255–263. 3 Baumgaertel S, Jones CL, Unal M. Miniscrew biomechanics: Guidelines for the use of rigid indirect anchorage mechanics. Am J Orthod Dentofacial Orthop. 2017;152:413–419. 4 Favero L, Brollo P, Bressan E. Orthodontic anchorage with specific fixtures: related study analysis. Am J Orthod Dentofacial Orthop. 2002;122:84–94. 5 Miyawaki S, Koyama I, Inoue M, et al. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2003;124:373–378. 6 Alkadhimi A, Al‐Awadhi EA. Miniscrews for orthodontic anchorage: a review of available systems. J Orthod. 2018;45:102–114. 7 Dalessandri D, Salgarello S, Dalessandri M, et al. Determinants for success rates of temporary anchorage devices in orthodontics: a meta‐analysis (n > 50). Eur J Orthod. 2014;36:303–313. 8 Kuroda S, Nishii Y, Okano S, Sueishi K. Stress distribution in the mini‐screw and alveolar bone during orthodontic treatment: a finite element study analysis. J Orthod. 2014;41:275–284. 9 Papageorgiou SN, Zogakis IP, Papadopoulos MA. Failure rates and associated risk factors of orthodontic miniscrew implants: a meta‐analysis. Am J Orthod Dentofacial Orthop. 2012;142:577–595. 10 Kravitz ND, Kusnoto B. Risks and complications of orthodontic miniscrews. Am J Orthod Dentofacial Orthop. 2007;131:43–51. 11 Park HS, Jeong SH, Kwon OW. Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2006;130:18–25. 12 Ure DS, Oliver DR, Kim KB, et al. Stability changes of miniscrew implants over time. Angle Orthod. 2011;81:994–1000. 13 Antoszewska J, Papadopoulos MA, Park HS, Ludwig B. Five‐year experience with orthodontic miniscrew implants: a retrospective investigation of factors influencing success rates. Am J Orthod Dentofacial Orthop. 2009;136:158.e1–10. 14 Chen Y, Kang ST, Bae SM, Kyung HM. Clinical and histologic analysis of the stability of microimplants with immediate orthodontic loading in dogs. Am J Orthod Dentofacial Orthop. 2009;136:260–267.

15 Moon CH, Lee DG, Lee HS, et al. Factors associated with the success rate of orthodontic miniscrews placed in the upper and lower posterior buccal region. Angle Orthod. 2008;78:101–106. 16 Papadopoulos MA, Papageorgiou SN, Zogakis IP. Clinical effectiveness of orthodontic miniscrew implants: a meta‐ analysis. J Dent Res. 2011;90:969–976. 17 Alharbi F, Almuzian M, Bearn D. Miniscrews failure rate in orthodontics: systematic review and meta‐analysis. Eur J Orthod. 2018; 40:519–530. 18 Cheng SJ, Tseng IY, Lee JJ, Kok SH. A prospective study of the risk factors associated with failure of mini‐ implants used for orthodontic anchorage. Int J Oral Maxillofac Implants. 2004;19:100–106. 19 Mohammed H, Wafaie K, Rizk MZ, et al. Role of anatomical sites and correlated risk factors on the survival of orthodontic miniscrew implants: a systematic review and meta‐analysis. Prog Orthod. 2018;19:36. 20 Nguyen MV, Codrington J, Fletcher L, et al. The influence of miniscrew insertion torque. Eur J Orthod. 2018;40:37–44. 21 Poggio PM, Incorvati C, Velo S, Carano A. “Safe zones”: a guide for miniscrew positioning in the maxillary and mandibular arch. Angle Orthod. 2006;76:191–197. 22 Radwan ES, Montasser MA, Maher A. Influence of geometric design characteristics on primary stability of orthodontic miniscrews. J Orofac Orthop. 2018;79:191–203. 23 Shah AH, Behrents RG, Kim KB, et al. Effects of screw and host factors on insertion torque and pullout strength. Angle Orthod. 2012;82:603–610. 24 Uesugi S, Kokai S, Kanno Z, Ono T. Stability of secondarily inserted orthodontic miniscrews after failure of the primary insertion for maxillary anchorage: maxillary buccal area vs midpalatal suture area. Am J Orthod Dentofacial Orthop. 2018;153:54–60. 25 Uesugi S, Kokai S, Kanno Z, Ono T. Prognosis of primary and secondary insertions of orthodontic miniscrews. What we have learned from 500 implants? Am J Orthod Dentofacial Orthop. 2017;152:224–231. 26 Watanabe T, Miyazawa K, Fujiwara T, et al. Insertion torque and Periotest values are important factors predicting outcome after orthodontic miniscrew placement. Am J Orthod Dentofacial Orthop. 2017;152:483–488. 27 Oh HJ, Cha JY, Yu HS, Hwang CJ. Histomorphometric evaluation of the bone surrounding orthodontic miniscrews according to their adjacent root proximity. Korean J Orthod. 2018;48:283–291.

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66 Pros and Cons of Miniscrews and Miniplates for Orthodontic Treatment Cheol‐Hyun Moon Department of Orthodontics, Gil Medical Center, Gachon University College of Medicine, Incheon, South Korea

66.1 ­Introduction Anchorage control is very important in orthodontic treatment to achieve the planned tooth movement without side effects. Temporary anchorage devices (TADs) have been broadly used in the orthodontic field with high clinical value [1–4]. TADs can be categorized as screw type or plate type, depending on their shape. Understanding the characteristics of each is helpful when selecting the appropriate device for individual cases.

66.2 ­Miniscrews The advantages of miniscrews include the provision of sufficient anchorage for tooth movement, the convenience of placement and removal, and low cost. However, there can be complications with miniscrews, such as injury to the root and fracture of the miniscrew.

66.2.1  Force Application Miniscrews can provide sufficient anchorage to support orthodontic tooth movement. Previous research has shown that miniscrews can withstand forces from 300 g [5–7] up to 800 g [8]. In some cases, miniscrews may not provide sufficient anchorage for orthopedic forces, but they can provide good anchorage for orthodontic force.

66.2.2  Success Rate There was a broad range of success rates with miniscrews. Miyawaki et al. [9] reported a success rate of 0%, while 100% success rate of miniscrews was shown by Motoyoshi et al. [10]. For miniscrews placed on the buccal side of the alveolar bone, Moon et al. [11, 12] reported a 79–83.8% success rate, and other groups have reported greater than 80%

s­ uccess rate. Meanwhile, the success rate for miniscrews placed on the palatal side was greater than 90% [13–16]. Several factors were identified that influence the success rate of miniscrews, such as the skeletal pattern [11], age of the patient, skill of the operator [16], root proximity [17], length of the miniscrews [18], drilling or drill‐free method of insertion [19], and cortical thickness [20]. Although more research is required to determine how these factors influence the success rate of miniscrews [14, 15], we assume that placing a long miniscrew at a distance of at least 1 mm from the root using the drill‐free method will result in an increase in the success rate.

66.2.3  Limiting Factors 66.2.3.1  Root Damage from Miniscrews

Root damage can occur when miniscrews are implanted [21], a factor that limits the location of miniscrew placement. Liu et al. [22] and Suzuki and Suzuki [23] proposed the use of a surgical template to prevent root damage during miniscrew placement. Cone‐beam computed tomography also can provide useful information for assessing the root‐to‐ root distance and the cortical bone thickness [17, 24]. Usually, periapical radiographs are taken before and after placement of miniscrews in our clinic. Even though they do not provide accurate information about direct contact between a miniscrew and the roots, they can suggest whether immediate removal and replacement of a miniscrew to another position is required (Figure 66.1). When a root is injured by a miniscrew, almost complete recovery of the root surface is likely if the miniscrew is removed immediately and the injury is confined to the dentin or cementum. However, if the miniscrew invades the pulp, normal healing will not occur [21, 25–27]. Therefore, to prevent root damage, extra‐alveolar placement of the miniscrew is recommended as having a high success rate [28, 29].

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section VI  Complications with the Use of TADs

(a)

(b)

Figure 66.1  Verification of the location of the miniscrew by periapical radiographs taken at different angles often helps to assess the whether the miniscrew is in contact with the root. (a) After x‐ray verification, the miniscrew was kept in the same place. (b) After x‐ray verification, the miniscrew was removed and placed in a different location.

(a)

(b)

Figure 66.2  Miniscrew fracture. Miniscrews were placed on the palatal side. Upon removal after 20 months of usage, fractures were found on both miniscrews. (a) Miniscrews placed on the palatal side. (b) Miniscrews fractured during removal.

66.2.3.2  Fracture of the Miniscrew

Fracture of the implant is another complication to consider when using miniscrews (Figure  66.2) [30, 31]. Buchter et al. [5] reported seeing a 4% incidence of miniscrew fracture, while Wilmes et al. [32] observed that miniscrew fracture occurred at insertion torque values of between 108.9 and 640.9 N·mm. Insertion torques of 100 N·mm or more were associated with low success rates [33]. Predrilling in patients with dense bone [32], and using miniscrews with a diameter more than 1.5 mm are important for the prevention of fractures [34].

When removing a fractured miniscrew, the use of a trephine bur causes a large amount of surrounding bone to be removed, so it is advisable to remove the surrounding bone with a carbide bur and then remove the fractured TAD with a Howe plier [31, 35]. 66.2.3.3  Ingestion of a Miniscrew

If a miniscrew loosens while a patient is eating or sleeping, the patient may swallow it. The sharp tip of the miniscrew could get lodged in their stomach; however, in most cases, it gets excreted naturally [36].

Chapter 66  Pros and Cons of Miniscrews and Miniplates

66.3 ­Miniplates

66.3.2  Success Rate

Miniplates, developed by Sugawara and Nishimura [37], address the disadvantages of miniscrews. They provide strong anchorage, have high success rates, a low probability of root damage, and low risk of fracture as advantages; however, the need for surgery and high cost are their disadvantages.

66.3.1  Force Application Maxillary protraction has been accomplished with a force of 300–500 g, using a combination of headgear and ­miniplates on the maxilla [38, 39]. For patients with cleft palate, miniplates are placed on the maxilla and mandible followed by forward traction of the maxilla [40]. Miniplates are fixed with two or three screws so that they can resist the large forces necessary for orthopedic treatment.

Miniplates made of titanium provide an on‐plant effect on the bone surface. They use two to three screws for fixation which provide a stronger implant effect on the cortical bone than that of miniscrews. These factors contribute to the high success rates (96.4–98.6%) when miniplates are used [9, 30, 41]. Miniplates avoid the risk of root damage by using short monocortical screws, placed in the extra‐alveolar regions such as the zygomatic buttress and retromolar pad [30, 41]. In addition, there is no risk of contact with the roots when the teeth move [42]. To the best of my knowledge, there have been no reports of miniplate or fixation screw fractures. This is thought to be due to the thickness (a diameter of 2 mm) and short length (4–7 mm) of the screws used for the fixation of miniplates compared to the length of the miniscrews [38, 39, 41].

(a)

(b)

(c)

(d)

Figure 66.3  Miniplate placement. (a) Miniplates in the maxillary buccal side were placed in the exact positions as requested by the orthodontist. Accurate and sufficient communication between the orthodontist and oral surgeon and sufficient experience of the oral surgeon are necessary for successful placement. Left, Panoramic radiograph; right, intraoral photographs. (b) Miniplates placed for intrusion of the maxillary first and second molars. The miniplates on both sides were not effective in properly intruding the second molars because they had been inappropriately placed in the first molar regions. This could have been due to an error by the oral surgeon or a lack of good communication between the oral surgeon and orthodontist about where the miniplates should be placed. (c) Miniplates placed for intrusion of the maxillary first and second molars. The miniplate on the right side was placed more buccally to be covered with the soft tissues and was invisible. This happened due to a lack of experience on the part of the oral surgeon. The miniplate on the left side was placed in the proper position. (d) Miniplate in the improper location. There is gingival swelling due to inflammation. This inflammation might cause the miniplate to loosen and fall off.

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Section VI  Complications with the Use of TADs

66.3.3  Limiting Factors 66.3.3.1  Surgery and Postoperative Discomfort

Lam et  al. [30] observed that the main limitations with miniplates was the requirement for surgery. Flap surgery is not usually performed by orthodontists [41] but rather by an oral surgeon or periodontist, which might cause a delay in the procedure. Sometimes miniplates are placed in positions other than those recommended by the orthodontist. The surgical ­procedures for miniplate placement can also result in postoperative pain, swelling, or speech difficulty (Figure 66.3) [30, 41, 43].

66.3.3.2  Economic Factors

Miniplates are made of titanium and require two to three anchor screws. Therefore, they are expensive compared to miniscrews. In addition, although orthodontists may place miniplates by themselves, patients are often referred to an oral surgeon or periodontist for the surgery [40, 41]. This is in contrast to miniscrews, which are most often placed by orthodontists. Thus, miniplates are more expensive and less affordable than miniscrews.

Case 66.1  Diagnosis

Treatment Alternatives

A 21‐year‐old male presented with chief complaints of crowded teeth, an anterior open bite, and mouth protrusion. He had a convex facial profile, facial asymmetry, and mentalis strain when closing his mouth. A lateral cephalogram revealed a severe skeletal problem (Figure 66.4 and Table 66.1).

Orthodontic and surgical treatment options were ­presented to the patient as the first line of treatment. The patient agreed to undergo orthognathic surgery if orthodontic treatment was not successful.

Figure 66.4  Pre-treatment photographs and radiographs

Table 66.1  Lateral cephalometric measurements.

Treatment Plan

Norm

Pre-treatment

Post‐treatment

SNA (°)

82.0

76.8

76.9

SNB (°)

80.0

75.0

74.6

ANB (°)

2.0

1.8

2.3

Wits (mm)

−1.0

−8.0

−1.4

Occlusal plane (°)

14.0

6.0

10.6

U1‐FH (°)

116.0

117.6

109.4

IMPA (°)

90.0

86.7

73.7

FMIA (°)

65.0

54.7

69.4

FMA (°)

25.0

38.4

36.8

PFH/AFH (%)

69.0

56.6

56.5

Z angle (°)

75.0

64.1

68.7

SNA, Sella‐nasion‐A point; SNB, sella‐nasion‐B point; ANB, A point‐nasion‐B point; Wits, distance between perpendiculars drawn from point A and point B onto the occlusal plane; Occlusal plane, occlusal plane to FH plane; U1‐FH, maxillary central incisor to FH plane; IMPA, incisor mandibular plane angle; FMIA, Frankfort mandibular incisor angle; FMA, Frankfort mandibular plane angle; PFH, posterior facial height, distance between sella and gonion; AFH, anterior facial height, distance between nasion and menton; FHI (PFH/AFH), posterior facial height/anterior facial height; Z angle, angle between FH plane and Z line (line drawn from soft tissue pogonion to the most forwardly placed lip).

Details about the type of TADs (plate and screw types) required for maxillary molar intrusion and en‐masse retraction of maxillary incisors were provided to the patient. He was also informed that surgery would be required for placement of the miniplate, and of the cost of the procedure. Treatment Progress For molar intrusion, three miniscrews (1.6 mm in diameter, 8 mm in length) were placed on the palatal side, and a spider bar was fabricated and attached to the miniscrews in the orthodontic department. The ­ miniplates were implanted by an oral surgeon. Four screws (2 mm in diameter, 4 mm in length) were used to fix the two L‐type miniplates. The operation was performed under local anesthesia in the morning. After discharge, at home the patient developed severe swelling at the surgical site so he ­ returned to the hospital in the afternoon of the day of the operation. There was bleeding and a blood clot had formed at the surgical site. The surgical wound was dressed after removal of the blood clot. A week after surgery, the swelling had completely subsided without any other complications. There were no complications associated with the miniplates during the subsequent treatment.

(a)

(b)

(c)

(d)

(e)

Figure 66.5  Treatment progress. (a) At two months of treatment, maxillary TADs (miniscrews and miniplates) were installed. (b) At five months of treatment, for intrusion of the maxillary left premolars, two miniscrews were installed and a properly designed wire bar was attached. (c) At 10 months of treatment, two miniscrews were placed in the maxillary right side as well. The first premolars were extracted to solve the protrusion and crowding. (d) At 14 months of treatment, the second premolars were extracted from the mandible. The miniscrews were placed mesial of the mandibular first molars. The miniscrews placed in the maxillary premolars were removed between the seventh and eleventh months. (e) At 35 months of treatment, crowding of the anterior teeth was resolved and optimal overbite was established.

(Continued )

Figure 66.6  Post‐treatment photographs and radiographs.

During treatment, six more miniscrews (1.4 mm in diameter, 6 mm in length) were installed without complication for intrusion and retraction (Figure 66.5). Treatment Results The treatment was finished in 37 months. The palatal miniscrews were removed, but we decided to retain the maxillary miniplates and mandibular miniscrews, given the high probability of a recurrence of the open bite (Figure 66.6). Lateral cephalometric superimposition shows the intrusion of the maxillary molars and counterclockwise rotation of the mandible. The severe anterior open bite was corrected with sufficient posterior intrusion. To improve occlusion, the splint was removed from between the mandibular first molar and the minis­ crew and then intermaxillary elastics were used for 22  months. It is presumed that the extrusion of the  mandibular molar and premolar has occurred (Figure 66.7, Table 66.1).

Figure 66.7  Cephalometric superimposition: pre-treatment (black); post‐treatment (red).

Chapter 66  Pros and Cons of Miniscrews and Miniplates

66.4  ­Conclusions TADs provide a secure anchorage for successful orthodontic treatment. A thorough understanding of the

advantages and disadvantages of miniscrews vs. miniplates will enable orthodontists to use them appropriately, resulting in significant benefits to their orthodontic practice and patients.

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14 Papageorgiou SN, Zogakis LP, Papadopoulos MA. Failure rates and associated risk factors of orthodontic miniscrew implants: a meta‐analysis. Am J Orthod Dentofacial Orthop. 2012;142:577–595. 15 Dalessandri D, Salgarello S, Dalessandri M, et al. Determinants for success rates of temporary anchorage devices in orthodontics: a meta‐analysis. Eur J Orthod. 2014;36:303–313. 16 Kim YH, Yang SM, Kim S, et al. Midpalatal miniscrews for orthodontic anchorage; Factors affecting clinical success. Am J Orthod Dentofacial Orthop. 2010;137:66–72. 17 Kuroda S, Yamada K, Deguchi T, et al. Root proximity is a major factor for screw failure in orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2007;131(suppl):S68–S73. 18 Sarul M, Minch L, Park HS, Antoszewska‐Smith J. Effect of the length of orthodontic mini‐screw implants on their long‐term stability. A prospective study. Angle Orthod. 2015;85:33–38. 19 Turkoz C, Atac MS, Tuncer C, et al. The effect of drill‐free drilling methods on the stability of mini‐implants under early orthodontic loading in adolescent patients. Eur J Orthod. 2011;33:533–536. 20 Marquezan M, Mattos CT, Sant’Anna EF, et al. Does cortical thickness influence the primary stability of miniscrews? A systematic review and meta‐analysis. Angle Orthod. 2014;84:1093–1103. 21 Hwang YC, Hwang HS. Surgical repair of root perforation caused by an orthodontic miniscrew implant. Am J Orthod Dentofacial Orthop. 2011;139:407–411. 22 Liu H, Liu D, Wang G, et al. Accuracy of surgical positioning of orthodontic miniscrews with a computer‐ aided design and manufacturing template. Am J Orthod Dentofacial Orthop. 2010;137:728.e1–728.e10. 23 Suzuki EY, Suzuki B. Accuracy of miniscrew implant placement with a 3‐dimensional surgical guide. J Oral Maxillofac Surg. 2008;66:1245–1252. 24 Kang S, Lee SJ, Ahn SJ, et al. Bone thickness of the palate for orthodontic mini‐implant anchorage in adults. Am J Orthod Dentofacial Orthop. 2007;131:S74–81. 25 Alves M Jr, Baratieri C, Mattos CT, et al. Root repair after contact with mini‐implants: systematic review of the literature. Eur J Orthod. 2013;35:491–499.

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2 6 Brisceno CE, Rossouw PE, Carrillo R, et al. Healing of the roots and surrounding structures after intentional damage with miniscrew implants. Am J Orthod Dentofacial Orthop. 2009;135:292–301. 27 Kim H, Kim TW. Histologic evaluation of root‐surface healing after contact or approximation during placement of mini‐implants. Am J Orthod Dentofacial Orthop. 2011;139:752–760. 28 Jia X, Chen X, Huang X. Influence of orthodontic mini‐implant penetration of the maxillary sinus in the infrazygomatic crest region. Am J Orthod Dentofacial Orthop. 2018;153:656–661. 29 Chang C, Liu SSY, Roberts WE. Primary failure rate for 1680 extra‐alveolar mandibular buccal shelf mini‐screws placed in movable mucosa or attached gingiva. Angle Orthod. 2015;85:905–910. 30 Lam R, Goonewardene MS, Allen BP, Sugawara J. Success rate of a skeletal anchorage system in orthodontics: a retrospective analysis. Angle Orthod. 2018;88:27–34. 31 Desai M, Jain A, Sumra N. Surgical management of fractured orthodontic mini‐implant – a case report. J Clin Diag Res. 2015;9:ZD06–ZD07. 32 Wilmes B, Panayotidis A, Drescher D. Fracture resistance of orthodontic mini‐implants: a biomechanical in vitro study. Eur J Orthod. 2011;33:396–401. 33 Motoyoshi M, Hirabayashi M, Uemura M, Shimizu. Recommended placement torque when tightening an orthodontic mini‐implant. Clin Oral Implant Res. 2006;17:109–114. 34 Barros SE, Janson G, Chiqueto K, et al. Effect of mini‐ implant diameter on fracture risk and self‐drilling

35

36

37 38

39

40

41

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efficacy. Am J Orthod Dentofacial Orthop. 2011;140:e181–e192. Ahluwalia R, Kaul A, Singh G, et al. Microimplants fracture: prevention is better than cure. J Ind Orthod Soc. 2012;46:82–85. Choi BH, Li J, Kim HS, et al. Ingestion of orthodontic anchorage screws: an experimental study in dogs. Am J Orthod Dentofacial Orthop. 2007;131:767–768. Sugawara J, Nishimura N. Minibone plates: the skeletal anchorage system. Semin Orthod. 2005;11:47–56. Cha BK, Lee NK, Choi DS. Maxillary protraction treatment of skeletal Class III children using miniplate anchorage. Korean J Orthod. 2007;37:73–84. Kaya D, Kocadereli I, Kan B, Tasar F. Effectiveness of facemask treatment anchored with miniplates after alternate rapid maxillary expansions and constrictions: a pilot study. Angle Orthod. 2011;81:639–646. Garib D, Yatabe M, Faco RAS, et al. Bone‐anchored maxillary protraction in a patient with complete cleft lip and palate: a case report. Am J Orthod Dentofacial Orthop. 2018;153:290–297. Sugawara J. Temporary skeletal anchorage devices: the case for miniplates. Am J Orthod Dentofacial Orthop. 2014;145:559–565. Chung KR, Kim SH, Kang YG, Nelson G. Orthodontic miniplate with tube as an efficient tool for borderline cases. Am J Orthod Dentofacial Orthop. 2011;139:551–562. Kuroda S, Sugawara Y, Deguchi T, et al. Clinical use of miniscrew implants as orthodontic anchorage: success rates and postoperative discomfort. Am J Orthod Dentofacial Orthop. 2007; 131:9–15.

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67 Orthodontic Miniscrews: The Pearls and Pitfalls of TADs Takashi Ono Department of Orthodontic Science, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan

67.1 ­The Golden Axe in Orthodontic Treatment Anchorage control is one of the most important factors in orthodontic treatment, and patient compliance is indispensable for the application of the various intra‐ and extraoral appliances required for anchorage control. Recently, the paradigm of anchorage control has shifted toward temporary anchorage devices (TADs). In ­particular,

the application of miniscrews has become a popular method for achieving anchorage in non‐compliant patients, because they can be inserted into the bones rapidly and easily. Moreover, the application of miniscrews allows more dynamic tooth movement than conventional methods. In this report, we describe two cases in which the patients underwent treatment by means of miniscrews and we discuss the effectiveness of the treatment.

Case 67.1  Maximum Retraction of Anterior Teeth in a Protrusive Profile The patient was a 22‐year‐old woman who presented with the chief complaints of lip prominence, protrusion, and a gummy smile (Figure 67.1). Pre-treatment intraoral and facial photographs indicated Class II malocclusion. Lateral cephalogram indicated a skeletal Class I relationship (ANB, 3.2°) with a protrusive profile. The maxillary and mandibular incisors were labially inclined (U1‐FH, 128.3°; IMPA, 102.9°). On the basis of these findings, the patient was diagnosed with Class II Division 1 malocclusion with a protrusive profile and an unesthetic smile. The overall treatment goals were to obtain Class I molar occlusion with an ideal overjet and overbite, and to improve the protrusive profile and gummy smile. To this end, we planned extraction of the maxillary and first premolars, as well as retraction and intrusion of the ­second premolars and extreme maxillary incisors.

Intrusion of the maxillary anterior teeth was attempted with J‐hook headgear; however, the patient’s compliance was poor. Therefore, two miniscrews were inserted between the maxillary second premolars and first molars to reinforce anchorage for anterior tooth retraction. We performed space closure with en‐masse sliding mechanics, using elastic power chains from the miniscrews to long hooks placed between the lateral incisors and canines. The duration of active treatment was 27 months. As a result of treatment, the patient showed an improved profile and gummy smile, a Class I molar relationship, and an ideal overjet and overbite. Lateral cephalometric superimposition showed retraction of the maxillary and mandibular incisors, along with intrusion, without loss of maxillary molar anchorage; this resulted in improvement of the facial profile. (Continued )

Temporary Anchorage Devices in Clinical Orthodontics, First Edition. Edited by Jae Hyun Park. © 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.

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Section VI  Complications with the Use of TADs

Figure 67.1  Case 67.1: Pre- and post-treatment facial and intraoral photographs, as well as superimposition.

Case 67.2  Mandibular Total Arch Distalization for Mandibular Protrusion The patient was a 24‐year‐old man who presented with the chief complaints of edge‐to‐edge bite and difficulty in chewing (Figure  67.2). Pre-treatment intraoral and facial photographs indicated Class III malocclusion. He had an edge‐to‐edge bite. Lateral cephalometric analysis demonstrated a skeletal Class III relationship (ANB, −2.7°). The SNA angle (80.3°) was normal, while the SNB angle (83.0°) was >+1 standard deviation (SD) from the mean angle for adult Japanese male individuals. On the basis of these findings, Class III malocclusion with mandibular protrusion was diagnosed. We recommended orthognathic surgery to improve the patient’s skeletal discrepancy, but he declined surgical treatment. Therefore, we planned dental compensation with an orthodontic approach alone. This involved mandibular total arch distalization to obtain a Class I molar relationship and good occlusion, with an ideal overjet and overbite.

After extraction of the mandibular third molars, orthodontic miniscrews were inserted between the bilateral mandibular second premolars and first molars. Mandibular molar distalization was initiated with sliding jigs and miniscrews. Elastic power chains connecting the miniscrews to hooks on jigs placed between the lateral incisors and canines were used for mandibular molar distalization. After completion of molar distalization and attainment of a Class I molar relationship, retraction of anterior teeth was performed. The initial edge‐to‐edge bite and Class III molar relationships were improved by mandibular total arch distalization. The duration of active treatment was 26 months. As a result of treatment, the patient showed a Class I molar relationship with an ideal overjet and overbite. Cephalometric superimposition showed distalization of mandibular molars and incisors, with clockwise rotation of the mandible. This was considered dental compensation for skeletal discrepancy.

Chapter 67  Orthodontic Miniscrews: The Pearls and Pitfalls of TADs

Figure 67.2  Case 67.2: Pre- and post-treatment facial and intraoral photographs, as well as superimposition.

67.2 ­Is the Miniscrew Always the Ideal Anchorage Tool? The orthodontic miniscrew is very effective for both clinicians and patients because it allows absolute anchorage control without requiring patient compliance. It appears to be an ideal anchorage tool; hence, the use of miniscrews has become the mainstream approach in modern orthodontic treatment. However, some complications have been reported in relation to the use of miniscrews. Some studies have indicated a lack of stability and loss of some miniscrews prior to achievement of treatment goals [1–3]. Many retrospective studies and systematic reviews have reported that the success rate of orthodontic miniscrews exceeds 80%. However, some miniscrews could be lost, despite the low failure rate (range: 5–40%, mean: approximately 15%) [1– 3]. Risk factors associated with an instability of miniscrews can be categorized as host‐related factors (age [1], sex [3], oral hygiene [3], cortical bone thickness [4–6], root proximity [5], where the insertion occurs (maxilla or mandible) [2, 7]), miniscrew‐related factors (shape [8], diameter [3], and length [9] of the screws), surgical management‐related factors (insertion torque [6], angle [4], placement height in the movable mucosa or attached gingiva [5], the necessity for predrilling [10] or flap surgery [5], and the latency

period (early or delayed orthodontic loading) [2]). Although many factors seem to affect success and failure rates, there is little supporting evidence. Further clinical studies are needed to provide the information necessary to achieve more predictable results with miniscrews. When miniscrews are lost, the options are to reinsert them or change the treatment plan, including the use of other appliances for anchorage control. Although many case reports in the literature have described successful outcomes with miniscrews, few studies have reported follow‐up of cases that failed. Recently, to determine indications for the application of miniscrews based on case presentation, we conducted two retrospective studies [11, 12] on secondary post‐failure reinsertion of the first insertion to focus on cases that involved failure of miniscrew insertion. These two studies are described in the following sections.

67.3 ­Study 1: Success Rate of Secondary Insertion at the Maxillomandibular Buccal Site In this study, we investigated both primary and secondary insertion success rates in the buccal area in both jaws and examined risk factors associated with their instability [11].

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Section VI  Complications with the Use of TADs

The subjects were 240 patients [61 men and 179 women, aged 28.1 ± 9.8 years (mean ± SD)] and the total number of miniscrews inserted in the subjects was 500. Before surgery, 3D computed tomography (CT) images were obtained for all subjects and the anatomical features, i.e., root proximity, cortical bone thickness, and maxillary sinus, were analyzed. Based on the imaging results, the miniscrew placement sites, as well as required diameters and lengths, were selected to avoid injury to the roots and minimize damage to surrounding tissues. Success was defined based on the following three criteria: (i) absence of inflammation in soft tissue surrounding the miniscrews, (ii) absence of clinically detectable mobility, and (iii) sustained anchorage function after one year of orthodontic loading. Cases that did not meet these criteria were considered as failures. If the miniscrews lacked stability, they were removed. A new miniscrew, of the same or different size (with changes in diameter and length, as necessary), was reinserted into the same position (between the same pair of teeth as used for the first insertion, with changes in the mesio‐distal position, height, and insertion angle) or into other positions (between a different pair of teeth from that used in the first insertion). Over a one‐year period after insertion, the overall primary success rate was 80.4% for all miniscrews (402 of 500 screws). Of the 98 screws that exhibited failure of primary insertion, reinsertion was attempted for 77 screws. The secondary success rate was 44.2% (34 of 77 screws), significantly lower than the primary success rate (P = 0.01 chi‐squared test, Figure 67.3). In cases where the inserted miniscrews lacked stability, reinsertion of a new screw into either the same or a different location was attempted. There were no significant differences between rates of reinsertion failure in the same or different locations; failure rates in both locations were high. Moreover, high failure rates of secondary insertions were not site‐specific. Based on these findings, it is likely that the instability of miniscrews was associated with the local condition of the position of primary insertion, as well as with the host’s

Success rate 100 80

%

* 80.4

60

44.2

40

Table 67.1  Rates of success and failure based on independent parameters with primary insertions. Parameters

Success (%)

Failure (%)

Male

85.5

14.5

Female

78.6

21.4

Gender

Primary

Secondary

Figure 67.3  Comparison of success rates with primary and secondary insertions. *P < 0.05.

Age (yr)

0.41