Contemporary Orthodontics, Sixth Edition PDF

Any screen. Any time. Anywhere. Activate the eBook version of this title at no additional charge. Expert Consult eBooks give you the power to browse and find content, view enhanced images, share notes and highlights—both online and offline. Unlock your eBook today. 1 Visit expertconsult.inkling...

Any screen. Any time. Anywhere. Activate the eBook version of this title at no additional charge. Expert Consult eBooks give you the power to browse and find content, view enhanced images, share notes and highlights—both online and offline. Unlock your eBook today. 1 Visit expertconsult.inkling.com/redeem Scan this QR code to redeem your eBook through your mobile device: 2 Scratch off your code 3 Type code into “Enter Code” box 4 Click “Redeem” 5 Log in or Sign up 6 Go to “My Library” Place Peel Off It’s that easy! Sticker Here For technical assistance: email [email protected] call 1-800-401-9962 (inside the US) call +1-314-447-8200 (outside the US) Use of the current edition of the electronic version of this book (eBook) is subject to the terms of the nontransferable, limited license granted on expertconsult.inkling.com. Access to the eBook is limited to the first individual who redeems the PIN, located on the inside cover of this book, at expertconsult.inkling.com and may not be transferred to another party by resale, lending, or other means. 2015v1.0 Contemporary Orthodontics This page intentionally left blank Contemporary Orthodontics Sixth Edition William R. Proffit, DDS, PhD Emeritus Professor (formerly Kenan Distinguished Professor) Department of Orthodontics School of Dentistry University of North Carolina Chapel Hill, North Carolina Henry W. Fields, Jr., DDS, MS, MSD Professor and Vig/Williams Orthodontic Division Chair College of Dentistry The Ohio State University Chief, Orthodontics, Nationwide Children’s Hospital Columbus, Ohio Brent E. Larson, DDS, MS Professor and Director Department of Developmental and Surgical Sciences School of Dentistry University of Minnesota Minneapolis, Minnesota David M. Sarver, DDS, MS Adjunct Professor, Orthodontics University of Alabama at Birmingham Birmingham, Alabama University of North Carolina Chapel Hill, North Carolina Sarver Orthodontics Vestavia Hills, Alabama 1600 John F. Kennedy Blvd. Ste 1600 Philadelphia, PA 19103-2899 CONTEMPORARY ORTHODONTICS, ISBN: 978-0-323-54387-3 SIXTH EDITION Copyright © 2019 by Elsevier, Inc. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Previous editions copyrighted 2013 by Mosby, an imprint of Elsevier, Inc., and 2007, 2000, 1993, 1986 by Mosby, Inc., an affiliate of Elsevier, Inc. Library of Congress Control Number: 2018951180 Content Strategist: Alexandra Mortimer Director, Continuity: Taylor Ball Publishing Services Manager: Catherine Albright Jackson Senior Project Manager: Claire Kramer Design Direction: Bridget Hoette Printed in China Last digit is the print number: 9 8 7 6 5 4 3 2 1 Preface As with previous editions, this edition of Contemporary Orthodontics we can be (or how uncertain we ought to be) that current views has been extensively revised to maintain the original goal of the are correct. book: to provide an up-to-date overview of orthodontics that is This edition of the book is supported by two types of supple- accessible to students, useful for residents, and a valuable reference mental teaching material available through Internet connections: for practitioners. In each section of the book, basic background (1) self-instructional computer teaching modules primarily oriented information needed by every dentist is covered first and is followed toward predoctoral dental students (but quite useful in residency by more detailed information for orthodontic specialists. training as well) and (2) video recordings of graduate-level clinical New aspects of this edition include: seminars on a variety of topics. Both types of supplemental materials an updated section on human embryology in which all the are used at the University of North Carolina and at other schools images now consist of human embryos, not experimental animals; in the United States and abroad. new material on three-dimensional (3-D) imaging and use The computer modules have been revised and updated of 3-D superimpositions to better understand treatment recently to match the content of this edition and are available to outcomes; students at participating dental schools on a dedicated website, a new, visual way to compare the material properties of various www.orthodonticinstruction.com. Supplying the modules in this orthodontic archwires; way has two major advantages: (1) once access to the website further information on bonding techniques, bracket develop- has been granted, students can use the teaching modules any- ments, and biomechanical considerations; where, and (2) updates and correction of errors are made on an expanded discussion of current growth modification proce- the website and are immediately available to all users. A preview dures and outcomes; of these teaching materials is available on the website. They new aspects of temporary anchorage device use for skeletal are available in course packages (four separate courses for the anchorage, especially linked screws for palatal anchorage and four levels of instruction) that include a syllabus with reading/ the biomechanics of skeletal anchorage; and viewing assignments, unit and course tests, and outlines for the case treatment examples of management of complex problems small-group seminars that are an integral part of the teaching in comprehensive orthodontic or surgical-orthodontic treatment approach. Access to individual components of the courses also can at all ages. be arranged. As before, literature citations have been chosen to include selected The “blended” educational method that includes the use of classic papers but largely are taken from recent publications that recorded seminars is based on the finding that orthodontic residents provide current information and cite previous publications. The who prepare for a seminar, observe the seminar on that topic that goal is to open the door to a more detailed evaluation of the was recorded live at another school, and participate immediately subject without including hundreds of older citations in the text. in a follow-up discussion, learn as much as those who participated As the emphasis on evidence-based treatment increases, systematic in the live seminar. The recorded seminars and the seminar prepara- reviews and meta-analysis are pulling together information from tion materials are available on a different dedicated website, multiple studies, and we also have incorporated findings from watchseminars.com, where orthodontic, oral and maxillofacial well-done reviews of this type. Unfortunately, the emphasis must surgery, and anesthesia teaching materials can be found. be on well done because by no means are all these reviews focused For further information about the supplemental teaching and conducted in a way that provides clinically useful data. We materials, contact Dr. William Proffit or Dr. Tate Jackson at the have attempted to provide recommendations for what are now the Department of Orthodontics, University of North Carolina School preferred approaches to treatment, while indicating how certain of Dentistry, Chapel Hill, North Carolina. v Acknowledgments We thank Ramona Hutton-Howe for her usual excellent work to illustrate the scope of modern treatment with computer technol- with the new photographs and radiographs for this edition and ogy and skeletal anchorage. Drs. Alex Culberson and Brennan Warren McCollum for his equally excellent artwork. Both have Skulski also provided images. Dr. Maura Partrick managed the worked with every edition of this book. Dayne Harrison took over extensive literature searches for the whole book, so that the references the organizational aspect this time, dealt with the hundreds of for all chapters are up to date to late 2017, and Dr. Katherine pages of text, and managed it nicely. (Katie) Born did the cephalometric superimpositions. For this edition, Dr. Kathy Sulik’s update on human embryology We benefited from critical review of sections of the manuscript and contribution of human embryo images of early development by a number of colleagues and appreciate their efforts to help us and the stages of palate closure gave us a clearer and current presenta- get things as correct as possible. And we are grateful to Drs. Gavin tion of this important subject. Dr. Anita’s Gohel’s contribution of Heymann and Tammy Severt of the University of North Carolina cone-beam CT images and clarification of three-dimensional (3-D) Orthodontic Alumni Association for their management of the imaging techniques made this section contemporary, and her voice book production finances. blended in seamlessly. Dr. Tung Nguyen’s 3-D superimpositions To each and all, we greatly appreciate your help. and his expertise in this area were important in our presentation of advances in 3-D technology and much appreciated, as was Dr. William R. Proffit Matt Larson’s assistance with the evaluation of new orthodontic Henry W. Fields, Jr. materials and biomechanical considerations. Brent E. Larson Drs. William Gierie, Dan Grauer, Jack Fisher, Nicole Scheffler, David M. Sarver Tim Shaughnessy, and Dirk Wiechmann provided illustrative cases vi Contents Section I The Orthodontic Problem Section II Diagnosis and Treatment Planning 1 Malocclusion and Dentofacial Deformity in 6 Orthodontic Diagnosis: The Problem-Oriented Contemporary Society, 2 Approach, 140 William R. Proffit William R. Proffit, David M. Sarver, Henry W. Fields, Jr. The Changing Goals of Orthodontic Treatment, 2 Questionnaire and Interview, 140 The Usual Orthodontic Problems: Epidemiology of Clinical Evaluation, 146 Malocclusion, 5 Diagnostic Records, 166 Why Is Malocclusion So Prevalent? 7 Orthodontic Classification, 193 Who Needs Treatment? 9 Development of a Problem List, 202 Type of Treatment: Evidence-Based Selection, 11 Demand for Treatment, 13 7 Orthodontic Treatment Planning: From Problem List to Specific Plan, 208 2 Concepts of Growth and Development, 18 William R. Proffit, Henry W. Fields, Jr., Brent E. Larson, William R. Proffit David M. Sarver Growth: Pattern, Variability, and Timing, 18 Treatment Planning Concepts and Goals, 208 Methods for Studying Physical Growth, 23 Major Issues in Planning Treatment, 208 The Nature of Skeletal Growth, 30 Treatment Possibilities, 209 Sites and Types of Growth in the Craniofacial Planning Comprehensive Orthodontic Treatment, 223 Complex, 32 Treatment Planning in Special Circumstances, 236 Theories of Growth Control, 37 Social and Behavioral Development, 46 Section III Biomechanics, Mechanics, and Contemporary Orthodontic 3 Early Stages of Development, 60 William R. Proffit Appliances Late Fetal Development and Birth, 60 8 The Biologic Basis of Orthodontic Therapy, 248 Infancy and Early Childhood: The Primary Dentition William R. Proffit Years, 60 Periodontal and Bone Response to Normal Late Childhood: The Mixed Dentition Years, 66 Function, 248 Periodontal Ligament and Bone Response to 4 Later Stages of Development, 84 Sustained Force, 250 William R. Proffit Anchorage and Its Control, 265 Adolescence: The Early Permanent Dentition Deleterious Effects of Orthodontic Force, 268 Years, 84 Growth Patterns in the Dentofacial Complex, 88 9 Mechanical Principles in Orthodontic Force Maturational and Aging Changes, 96 Control, 276 Brent E. Larson, William R. Proffit 5 The Etiology of Orthodontic Problems, 107 Elastic Materials and the Production of Orthodontic William R. Proffit Force, 276 Specific Causes of Malocclusion, 107 Design Factors in Orthodontic Appliances, 288 Genetic Influences, 121 Mechanical Aspects of Anchorage Control, 292 Environmental Influences, 124 Determinate Versus Indeterminate Force Etiology in Contemporary Perspective, 134 Systems, 298 vii viii Contents 10  Contemporary Orthodontic Appliances, 310 16  Comprehensive Treatment in Adolescence: William R. Proffit, Brent E. Larson Space Closure and Class II/Class III Removable Appliances, 310 Correction, 528 Fixed Appliances, 321 William R. Proffit, Brent E. Larson Space Closure in Incisor Protrusion Problems, 528 Section IV Treatment in Preadolescent Class II Correction in Adolescents, 538 Class III Camouflage, 551 Children: What Is Different? 11  Moderate Nonskeletal Problems in 17  Comprehensive Treatment: Finishing, 556 Preadolescent Children: Preventive and William R. Proffit, Brent E. Larson Interceptive Treatment in Family Practice, 356 Adjustment of Individual Tooth Positions, 556 Henry W. Fields, Jr., William R. Proffit Correction of Vertical Incisor Relationships, 562 Orthodontic Triage: Distinguishing Moderate From Final “Settling” of Teeth, 564 Complex Treatment Problems, 356 Positioners for Finishing, 567 Management of Occlusal Relationship Problems, 364 Special Finishing Procedures to Avoid Relapse, 569 Management of Eruption Problems, 375 Micro-Esthetic Procedures in Finishing, 570 Space Analysis: Quantification of Space Problems, 385 Treatment of Space Problems, 388 18  Retention, 579 William R. Proffit 12  Complex Nonskeletal Problems in Preadolescent Why Is Retention Necessary? 579 Children: Preventive and Interceptive Removable Retainers, 584 Treatment, 402 Fixed Retainers, 586 Henry W. Fields, Jr., William R. Proffit Active Retainers, 591 Eruption Problems, 402 Traumatic Displacement of Teeth, 406 Section VII Treatment for Adults Space-Related Problems, 409 19  Special Considerations in Treatment for Adults, 599 Section V Growth Modification William R. Proffit, David M. Sarver 13  Treatment of Skeletal Transverse and Class III Adjunctive Versus Comprehensive Treatment, 599 Problems, 430 Principles of Adjunctive Treatment, 600 William R. Proffit, Henry W. Fields, Jr. Adjunctive Treatment Procedures, 603 Growth Modification in the Transverse Plane of Comprehensive Treatment in Adults, 614 Space, 430 Summary, 654 Class III Growth Modification, 440 20  Combined Surgical and Orthodontic 14  Growth Modification in Class II, Open Bite/Deep Treatment, 657 Bite, and Multidimensional Problems, 455 William R. Proffit, David M. Sarver Henry W. Fields, Jr., William R. Proffit Development of Orthognathic Surgery, 657 Class II Growth Modification, 455 The Borderline Patient: Camouflage Versus Combined Vertical and Anteroposterior Problems, 484 Surgery, 657 Facial Asymmetry in Children, 492 Contemporary Surgical Techniques, 667 Special Considerations in Planning Surgical Treatment, 681 Section VI Comprehensive Orthodontic Putting Surgical and Orthodontic Treatment Together: Treatment in the Early Permanent Who Does What and When? 692 Dentition 15  Comprehensive Treatment in Adolescents: Alignment and Vertical Problems, 501 William R. Proffit, Brent E. Larson Class I Crowding/Protrusion, 501 Leveling, 518  SECTION I The Orthodontic Problem This section of the book addresses important questions that are the intellectual and scientific background for the practice of orthodontics: Why do we provide orthodontic treatment? Who needs treatment? How do people benefit from it? How prevalent are orthodontic problems? How are these problems related to growth of the head and face? How are these problems related to eruption of the teeth? Can we identify the etiology of these orthodontic problems? You need to consider the answers to these questions before you can appropriately diagnose orthodontic problems, plan the treatment that will provide maximum benefit to the patient, and carry out that treatment. The answers, to the best of our ability to provide them now, are in the following chapters. 1 1 Malocclusion and Dentofacial Deformity in Contemporary Society CHAPTER OUTLINE teeth and the correction of facial proportions. Little attention was paid to bite relationships, and because it was common practice to The Changing Goals of Orthodontic Treatment remove teeth for many dental problems, extractions for crowding The Development of Orthodontics or malalignment were frequent. In an era when an intact dentition Modern Treatment Goals: The Soft Tissue Paradigm was a rarity, the details of occlusal relationships were considered The Usual Orthodontic Problems: Epidemiology of unimportant. Malocclusion To make good prosthetic replacement teeth, it was necessary to develop a concept of occlusion, and this occurred in the late Why Is Malocclusion So Prevalent? 1800s. As the concepts of prosthetic occlusion developed and were Who Needs Treatment? refined, it was natural to extend this to the natural dentition. Psychosocial Problems Edward H. Angle (Fig. 1.1), whose influence began to be felt Oral Function about 1890, can be credited with much of the development of a Relationship to Injury and Dental Disease concept of occlusion in the natural dentition. Angle’s original Type of Treatment: Evidence-Based Selection interest was in prosthodontics, and he taught in that department Randomized Clinical Trials: The Best Evidence in dental schools in Pennsylvania and Minnesota in the 1880s. Retrospective Studies: Control Group Required His increasing interest in dental occlusion and in the treatment necessary to obtain normal occlusion led directly to his development Demand for Treatment of orthodontics as a specialty, with himself as the “father of modern Epidemiologic Estimates of Orthodontic Treatment Need orthodontics.” Who Seeks Treatment? Angle’s classification of malocclusion in the 1890s was an important step in the development of orthodontics because it not only subdivided major types of malocclusion but also included the first clear and simple definition of normal occlusion in the natural dentition. Angle’s postulate was that the upper first molars were the key to occlusion and that the upper and lower molars should be related so that the mesiobuccal cusp of the upper The Changing Goals of Orthodontic molar occludes in the buccal groove of the lower molar. If the teeth were arranged on a smoothly curving line of occlusion (Fig. 1.2) Treatment and this molar relationship existed (Fig. 1.3), then normal occlusion The Development of Orthodontics would result.3 This statement, which 100 years of experience has proved to be correct except when there are aberrations in the size Crowded, irregular, and protruding teeth have been a problem for of teeth, brilliantly simplified normal occlusion. some individuals since antiquity, and attempts to correct this disorder Angle then described three classes of malocclusion, based on go back at least to 1000 BC. Primitive (and surprisingly well- the occlusal relationships of the first molars: designed) orthodontic appliances have been found in both Greek Class I: Normal relationship of the molars, but line of occlusion and Etruscan materials.1 As dentistry developed in the 18th and incorrect because of malposed teeth, rotations, or other causes 19th centuries, a number of devices for the “regulation” of the Class II: Lower molar distally positioned relative to upper molar, teeth were described by various authors and apparently used sporadi- line of occlusion not specified cally by the dentists of that era. Class III: Lower molar mesially positioned relative to upper After 1850 the first texts that systematically described ortho- molar, line of occlusion not specified dontics appeared, the most notable being Norman Kingsley’s Oral Note that the Angle classification has four classes: normal Deformities.2 Kingsley, who had a tremendous influence on American occlusion, Class I malocclusion, Class II malocclusion, and Class dentistry in the latter half of the 19th century, was among the III malocclusion (see Fig. 1.3). Normal occlusion and Class I first to use extraoral force to correct protruding teeth. He was also malocclusion share the same molar relationship but differ in the a pioneer in the treatment of cleft palate and related problems. arrangement of the teeth relative to the line of occlusion. The line Despite the contributions of Kingsley and his contemporaries, of occlusion may or may not be correct in Class II and Class III their emphasis in orthodontics remained the alignment of the malocclusion. 2  CHAPTER 1 Malocclusion and Dentofacial Deformity in Contemporary Society 3 Maxillary Mandibular Line of occlusion Fig. 1.1 Edward H. Angle in his 50s, as the proprietor of the Angle Fig. 1.2 The line of occlusion is a smooth (catenary) curve passing School of Orthodontia. After establishing himself as the first dental special- through the central fossa of each upper molar and across the cingulum ist, Angle operated proprietary orthodontic schools from 1905 to 1928 in of the upper canine and incisor teeth. The same line runs along the buccal St. Louis, Missouri; New London, Connecticut; and Pasadena, California, cusps and incisal edges of the lower teeth, thus specifying the occlusal in which many of the pioneer American orthodontists were trained. as well as interarch relationships once the molar position is established. Normal occlusion Class I malocclusion Class II malocclusion Class III malocclusion Fig. 1.3 Normal occlusion and malocclusion classes as specified by Angle. This classification was quickly and widely adopted early in the 20th century. It is incorporated within all contemporary descriptive and classification schemes. With the establishment of a concept of normal occlusion and a full complement of teeth in both arches, maintaining an intact a classification scheme that incorporated the line of occlusion, by dentition became an important goal of orthodontic treatment. the early 1900s orthodontics was no longer just the alignment of Angle and his followers strongly opposed extraction for orthodontic irregular teeth. Instead, it had evolved into the treatment of maloc- purposes. With the emphasis on dental occlusion that followed, clusion, defined as any deviation from the ideal occlusal scheme however, less attention came to be paid to facial proportions and described by Angle. Because precisely defined relationships required esthetics. Angle abandoned extraoral force because he decided this 4 SE C T I O N I The Orthodontic Problem was not necessary to achieve proper occlusal relationships. He TABLE Angle Versus Soft Tissue Paradigms: A New Way solved the problem of dental and facial appearance by simply 1.1 of Looking at Treatment Goals postulating that the best esthetics always were achieved when the patient had ideal occlusion. Parameter Angle Paradigm Soft Tissue Paradigm As time passed, it became clear that even an excellent occlusion Primary Ideal dental occlusion Normal soft tissue was unsatisfactory if it was achieved at the expense of proper facial treatment proportions and proportions. Not only were there esthetic problems, it often proved goal adaptations impossible to maintain an occlusal relationship achieved by pro- longed use of heavy elastics to pull the teeth together as Angle Secondary goal Ideal jaw relationships Functional occlusion and his followers had suggested. Under the leadership of Charles Hard and soft Ideal hard tissue Ideal soft tissue Tweed in the United States and Raymond Begg in Australia (both tissue proportions produce proportions define of whom had studied with Angle), extraction of teeth was rein- relationships ideal soft tissues ideal hard tissues troduced into orthodontics in the 1940s and 1950s to enhance Diagnostic Dental casts, Clinical examination of facial esthetics and achieve better stability of the occlusal emphasis cephalometric intraoral and facial relationships. radiographs soft tissues Cephalometric radiography, which enabled orthodontists to measure the changes in tooth and jaw positions produced by growth Treatment Obtain ideal dental and Plan ideal soft tissue approach skeletal relationships, relationships and and treatment, came into widespread use after World War II. These assume the soft then place teeth radiographs made it clear that many Class II and Class III maloc- tissues will be all and jaws as needed clusions resulted from faulty jaw relationships, not just malposed right to achieve this teeth. By use of cephalometrics, it also was possible to see that jaw growth could be altered by orthodontic treatment. In Europe, Function TMJ in relation to dental Soft tissue movement the method of “functional jaw orthopedics” was developed to emphasis occlusion in relation to display of teeth enhance growth changes, while in the United States, extraoral force came to be used for this purpose. At present, both functional Stability of Related primarily to Related primarily to and extraoral appliances are used internationally to control and result dental occlusion soft tissue pressure modify growth and form. Obtaining correct or at least improved and equilibrium jaw relationships became a goal of treatment by the mid-20th effects century. TMJ, Temporomandibular joint. The changes in the goals of orthodontic treatment, which now focus on facial proportions and the impact of the dentition on facial appearance, have been codified in the form of the soft tissue paradigm.4 Modern Treatment Goals: The Soft thereof) determine whether the orthodontic result will be stable. Keeping this in mind while planning treatment is critically Tissue Paradigm important. A paradigm can be defined as “a set of shared beliefs and assumptions 2. The secondary goal of treatment becomes functional occlusion. that represent the conceptual foundation of an area of science or What does that have to do with soft tissues? Temporomandibular clinical practice.” The soft tissue paradigm states that both the (TM) dysfunction, to the extent that it relates to the dental goals and limitations of modern orthodontic and orthognathic occlusion, is best thought of as the result of injury to the soft treatment are determined by the soft tissues of the face, not by tissues around the temporomandibular joint (TMJ) caused by the teeth and bones. This reorientation of orthodontics away from clenching and grinding the teeth. Given that, an important the Angle paradigm that dominated the 20th century is most easily goal of treatment is to arrange the occlusion to minimize the understood by comparing treatment goals, diagnostic emphasis, chance of injury. In this also, Angle’s ideal occlusion is not and treatment approach in the two paradigms (Table 1.1). With incompatible with the broader goal, but deviations from the the soft tissue paradigm, the increased focus on clinical examination Angle ideal may provide greater benefit for some patients and rather than examination of dental casts and radiographs leads to should be considered when treatment is planned. a different approach to obtaining important diagnostic information, 3. The thought process that goes into “solving the patient’s and that information is used to develop treatment plans that would problems” is reversed. In the past, the clinician’s focus was on not have been considered without it. dental and skeletal relationships, with the tacit assumption that More specifically, what difference does the soft tissue paradigm if these were correct, soft tissue relationships would take care make in planning treatment? There are several major effects: of themselves. With the broader focus on facial and oral soft 1. The primary goal of treatment becomes soft tissue relationships tissues, the thought process is to establish what these soft tissue and adaptations, not Angle’s ideal occlusion. This broader goal relationships should be and then determine how the teeth and is not incompatible with Angle’s ideal occlusion, but it acknowl- jaws would have to be arranged to meet the soft tissue goals. edges that to provide maximum benefit for the patient, ideal Why is this important in establishing the goals of treatment? occlusion cannot always be the major focus of a treatment plan. It relates very much to why patients and parents seek orthodontic Soft tissue relationships, both the proportions of the soft tissue treatment and what they expect to gain from it. integument of the face and the relationship of the dentition to The following sections of this chapter provide some background the lips and face, are the major determinants of facial appearance. on the prevalence of malocclusion, what we know about the need Soft tissue adaptations to the position of the teeth (or lack for treatment of malocclusion and dentofacial deformity, and how  CHAPTER 1 Malocclusion and Dentofacial Deformity in Contemporary Society 5 soft tissue considerations, as well as teeth and bone, affect both need and demand for orthodontic treatment. It must be kept in mind that orthodontics is shaped by biological, psychosocial, and cultural determinants. For that reason, when defining the goals of orthodontic treatment, one has to consider not only morphologic and functional factors, but a wide range of psychosocial and bioethi- cal issues as well. All these topics are discussed in much greater detail in the following chapters on diagnosis, treatment planning and treatment. The Usual Orthodontic Problems: Epidemiology of Malocclusion Angle’s “normal occlusion” more properly should be considered the ideal. In fact, perfectly interdigitating teeth arranged along a Fig. 1.4 Incisor irregularity usually is expressed as the irregularity index: perfectly regular line of occlusion are quite rare. For many years, the total of the millimeter distances from the contact point on each incisor epidemiologic studies of malocclusion suffered from considerable tooth to the contact point that it should touch, as shown by the blue lines. disagreement among investigators about how much deviation from For this patient, the irregularity index is 10 (mm). the ideal should be accepted within the bounds of normal. By the 1970s, a series of studies by public health or university groups in most developed countries provided a reasonably clear worldwide picture of the prevalence of the various types of malocclusion by degree of severity. In the United States, two large-scale surveys carried out by the U.S. Public Health Service (USPHS) covered children ages 6 to 11 years from 1963 to 1965 and youths ages 12 to 17 years in 1969 and 1970.5,6 As part of a large-scale national survey of health care problems and needs in the United States in 1989 through 1994 (Third National Health and Nutrition Examination Survey [NHANES III]), estimates of malocclusion again were obtained. This study of some 14,000 individuals was statistically designed to provide weighted estimates for approximately 150 million persons in the sampled racial or ethnic and age groups. The data provide reasonably current information for U.S. children and youths and include the first good data set for malocclusion in adults, with Fig. 1.5 A space between adjacent teeth is called a diastema. A maxil- separate estimates for the major racial or ethnic groups.7 lary midline diastema is relatively common, especially during the mixed The characteristics of malocclusion evaluated in NHANES III dentition in childhood, and disappears or decreases in width as the per- included the irregularity index, which is a measure of incisor manent canines erupt. Spontaneous correction of a childhood diastema alignment (Fig. 1.4); the prevalence of midline diastema larger is most likely when its width is less than 2 mm, so this patient is on the than 2 mm (Fig. 1.5); and the prevalence of posterior crossbite borderline and may need future treatment. (Fig. 1.6). In addition, overjet (Fig. 1.7) and overbite or open bite (Fig. 1.8) were measured. Overjet reflects Angle’s Class II and Class III molar relationships. Because overjet can be evaluated much more precisely than molar relationship in a clinical examina- tion, molar relationship was not evaluated directly. Data for these characteristics of malocclusion for children (age 8 to 11), youths (age 12 to 17), and adults (age 18 to 50) in the U.S. population, taken from NHANES III, are displayed graphically in Figs. 1.9 to 1.11. Note in Fig. 1.10 that in the age 8 to 11 group, just over half of U.S. children have well-aligned incisors. The rest have varying degrees of malalignment and crowding. The percentage with excellent alignment decreases in the age 12 to 17 group as the remaining permanent teeth erupt, then remains essentially stable in the upper arch but worsens in the lower arch for adults. Only 34% of adults have well-aligned lower incisors. Nearly 15% of adolescents and adults have severely or extremely irregular incisors, Fig. 1.6 Posterior crossbite exists when the maxillary posterior teeth so that major arch expansion or extraction of some teeth would are lingually positioned relative to the mandibular teeth, as in this patient. be necessary to align them (see Fig. 1.10). Posterior crossbite most often reflects a narrow maxillary dental arch but A midline diastema (see Fig. 1.5) often is present in childhood can arise from other causes. This patient also has a one-tooth anterior (26% have >2 mm space). Although this space tends to close, over crossbite, with the lateral incisor trapped lingually. 6 SE C T I O N I The Orthodontic Problem 60 Ideal alignment 50 Percent of population 40 Mandibular arch Overjet 30 Severe crowding 20 Excess overjet Fig. 1.7 Overjet is defined as horizontal overlap of the incisors. Normally 10 Open bite the incisors are in contact, with the upper incisors ahead of the lower by only the thickness of their incisal edges (i.e., overjet of 2 to 3 mm is the normal relationship). If the lower incisors are in front of the upper incisors, 0 the condition is called reverse overjet or anterior crossbite. 8-11 12-17 18-50 Age group Fig. 1.9 Changes in the prevalence of types of malocclusion from child- hood to adult life, United States, 1989 to 1994. Note the increase in incisor irregularity and decrease in severe overjet as children mature, both of which are related to more mandibular than maxillary growth. Overbite  0D[  0DQG 3HUFHQWRISRSXODWLRQ  Open bite    WR WR WR WR !PP ,GHDO 0LOG 0RGHUDWH 6HYHUH ([WUHPH ,QFLVRULUUHJXODULW\ PP Fig. 1.8 Overbite is defined as the vertical overlap of the incisors. Nor- mally, the lower incisal edges contact the lingual surface of the upper Fig. 1.10 Incisor irregularity in the U.S. population, 1989 to 1994. One- incisors at or above the cingulum (i.e., normally there is a 1- to 2-mm third of the population have at least moderately irregular (usually crowded) overbite). In open bite, there is no vertical overlap, and the vertical separa- incisors, and nearly 15% have severe or extreme irregularity. Note that tion of the incisors is measured to quantify its severity. irregularity in the lower arch is more prevalent at any degree of severity. 6% of youths and adults still have a noticeable diastema that Overjet or reverse overjet indicates anteroposterior deviations compromises the appearance of the smile. Blacks are more than in the Class II or Class III direction, respectively, with Class III twice as likely to have a midline diastema as whites or Mexican- being much less prevalent (Fig. 1.12). Normal overjet is 2 mm. Americans (P <.001). Overjet of 5 mm or more, suggesting Angle’s Class II malocclusion, Occlusal relationships must be considered in all three planes occurs in 23% of children, 15% of youths, and 13% of adults. of space. Lingual posterior crossbite (i.e., upper teeth lingual to This reflects the greater postnatal growth of the mandible than the lower teeth; see Fig. 1.6) is the major deviation from the normal maxilla, which is discussed in Chapter 2. Severe Class II problems transverse dental relationship and reflects deviations from ideal are less prevalent and severe Class III problems are more prevalent occlusion in the transverse plane of space. According to the in the Mexican-American than the white or black groups. NHANES III data,7 it occurs in 9% of the U.S. population, ranging Vertical deviations from the ideal overbite of 0 to 2 mm are from 7.6% of Mexican-Americans to 9.1% of whites and 9.6% less frequent in adults than children but occur in half the adult of blacks. population, with excessive overbite occurring much more frequently  CHAPTER 1 Malocclusion and Dentofacial Deformity in Contemporary Society 7 50 Open Bite Ideal Deep Bite 50 White Black 40 Mexican-American 40 Percent of Population Percent of population 30 30 20 20 10 10 0 0 0 to 1 mm 2 to 3 mm 4 to 6 mm 7 to 10 mm >10 mm >–4 –4 to –3 –2 to 0 0 to 2 3 to 4 5 to 7 >7 mm Ideal Mild Moderate Severe Extreme Extreme Severe Moderate Moderate Severe Extreme Incisor crowding, major population groups Incisor overlap (mm) Fig. 1.11 Incisor irregularity by racial or ethnic groups. The percentage Fig. 1.13 Open bite and deep bite relationships in the U.S. population, of the Mexican-American population with ideal alignment is lower than the 1989 to 1994. Half the population have an ideal vertical relationship of the other two groups, and the percentage with moderate and severe crowding incisors. Deep bite is much more prevalent than open bite, but vertical is higher. This may reflect the low number of Mexican-Americans with relationships vary greatly among racial groups. orthodontic treatment at the time of the Third National Health and Nutrition Examination Survey (NHANES III). (approximately 15%) as normal occlusions; and Class III (less than 1%) represents a very small proportion of the total. Class II Ideal Class III Differences in malocclusion characteristics between the United 40 States and other countries would be expected because of differ- ences in racial and ethnic composition. Although the available data Percent of population 30 are not as extensive as for American populations, it seems clear that Class II problems are most prevalent in whites of northern European descent (for instance, 25% of children in Denmark 20 are reported to have Class II malocclusion), whereas Class III problems are most prevalent in Asian populations (3% to 5% in 10 Japan, nearly 2% in China, with another 2% to 3% pseudo–Class III [i.e., shifting into anterior crossbite because of incisor interfer- 0 ences]). African populations are by no means homogenous, but >10 7-10 5-6 3-4 1-2 0 –1 to –2 –3 to –4 >–4 mm from the differences found in the United States between blacks Extreme Severe Moderate Mild Mild Moderate Severe Extreme and whites, it seems likely that Class III and open bite are more Overjet (mm) frequent in African than European populations and deep bite Fig. 1.12 Overjet (Class II) and reverse overjet (Class III) in the U.S. less frequent. population, 1989 to 1994. Only one-third of the population have ideal anteroposterior incisor relationships, but overjet is only moderately Why Is Malocclusion So Prevalent? increased in another one-third. Increased overjet accompanying Class II malocclusion is much more prevalent than reverse overjet accompanying Crowded and irregular teeth now occur in a majority of the popula- Class III. tion; skeletal remains indicate that this was unusual until relatively recently, although not unknown (Fig. 1.14). Because the mandible tends to become separated from the rest of the skull when long- than open bite (negative overbite) (Fig. 1.13). There are striking buried skeletal remains are unearthed, it is easier to be sure what differences between the racial or ethnic groups in vertical dental has happened to alignment of teeth than to occlusal relationships. relationships. Severe deep bite is nearly twice as prevalent in whites The skeletal remains suggest that all members of a group might as blacks or Mexican-Americans (P <.001), whereas open bite of tend toward a Class III or, less commonly, a Class II jaw relationship. more than 2 mm is five times more prevalent in blacks than in Similar findings are noted in present population groups that have whites or Mexican-Americans (P <.001). This almost surely reflects remained largely unaffected by modern development: crowding the slightly different craniofacial proportions of the black population and malalignment of teeth are uncommon, but the majority of groups (see Chapter 5 for a more complete discussion). In contrast the group may have mild anteroposterior or transverse discrepancies, to the higher prevalence of anteroposterior problems, vertical as in the Class III tendency of South Pacific islanders8 and buccal problems are less prevalent in Mexican-Americans than either blacks crossbite (X-occlusion) in aboriginal people of Australia.9 or whites. Although 1000 years is a long time relative to a single human From the survey data, it is interesting to calculate the percentage life, it is a very short time from an evolutionary perspective. The of American children and youths who would fall into Angle’s four fossil record documents evolutionary trends over many thousands groups. From this perspective, 30% at most have Angle’s normal of years that affect the present dentition, including a decrease in occlusion. Class I malocclusion (50% to 55%) is by far the largest the size of individual teeth, in the number of the teeth, and in the single group; there are about half as many Class II malocclusions size of the jaws. For example, there has been a steady reduction in 8 SE C T I O N I The Orthodontic Problem A B Fig. 1.14 Mandibular dental arches from specimens from the Krapina cave in Yugoslavia, estimated to be approximately 100,000 years old. (A) Note the excellent alignment in this specimen. Near-perfect alignment or minimal crowding was the usual finding in this group. (B) Crowding and malalignment are seen in this specimen, which had the largest teeth in this find of skeletal remains from approximately 80 individuals. (From Wolpoff WH. Paleoanthropology. New York: Alfred A Knopf; 1998.) Past and Present Tooth Size 300 250 Square millimeters 200 150 Qafzeh Neanderthal 100 English 50 I1 I2 C P1 P2 M1 M2 M3 Tooth category Fig. 1.15 The generalized decline in the size of human teeth can be seen by comparing tooth sizes from the anthropologic site at Qafzeh, dated 100,000 years ago; Neanderthal teeth, 10,000 years ago; and modern human populations. (Redrawn from Kelly MA, Larsen CS, eds. Advances in Dental Anthro- pology. New York: Wiley-Liss; 1991.) the size of both anterior and posterior teeth over at least the last It is easy to see that the progressive reduction in jaw size, if 100,000 years (Fig. 1.15). The number of teeth in the dentition of not well matched to a decrease in tooth size and number, could higher primates has been reduced from the usual mammalian pattern lead to crowding and malalignment. It is less easy to see why (Fig. 1.16). The third incisor and third premolar have disappeared, dental crowding should have increased quite recently, but this as has the fourth molar. At present, the human third molar, second seems to have paralleled the transition from primitive agricultural premolar, and second incisor often fail to develop, which indicates to modern urbanized societies. Cardiovascular disease and related that these teeth may be on their way out. Compared with other health problems appear rapidly when a previously unaffected primates, modern humans have quite underdeveloped jaws. population group leaves agrarian life for the city and civilization.  CHAPTER 1 Malocclusion and Dentofacial Deformity in Contemporary Society 9 M-3 PM-4 C 1-3 Basic mammalian M-3 PM-3 C 1-2 Prosimian M-3 PM-2 C 1-2 Higher ape M-3 (2) PM-2 C 1-2 Man Fig. 1.16 Reduction in the number of teeth has been a feature of primate evolution. In the present human population, third molars are so frequently missing that it appears a further reduction is in progress, and the relatively high prevalence of missing maxillary lateral incisors and mandibular second premolars suggests evolutionary pressure on these teeth. High blood pressure, heart disease, diabetes, and several other medical problems are so much more prevalent in developed than underdeveloped countries that they have been labeled “diseases of civilization.” There is some evidence that malocclusion increases within well-defined populations after a transition from rural villages to the city. Corruccini, for instance, reported a higher prevalence of crowding, posterior crossbite, and buccal segment discrepancy in urbanized youths compared with rural Punjabi youths of northern India.10 One can argue that malocclusion is another condition made worse by the changing conditions of modern life, perhaps resulting in part from less use of the masticatory apparatus with softer foods now. Under primitive conditions, of course, excellent function of the jaws and teeth was an important predictor of the ability to survive and reproduce. A capable masticatory apparatus was essential to deal with uncooked or partially cooked meat and plant foods. Watching an Australian aboriginal man using every muscle of his upper body to tear off a piece of kangaroo flesh from the barely cooked animal, for instance, makes one appreciate the decrease in demand on the masticatory apparatus that has accom- panied civilization (Fig. 1.17). An interesting proposal by anthro- pologists is that the introduction of cooking, so that it did not take as much effort and energy to masticate food, was the key to the development of the larger human brain. Without cooked food, it would not have been possible to meet the energy demand of the enlarging brain. With it, excess energy is available for brain development and robust jaws are unnecessary.11 Determining whether changes in jaw function have increased the prevalence of malocclusion is complicated by the fact that both dental caries and periodontal disease, which are rare on the primitive diet, appear rapidly when the diet changes. The result- ing dental pathology can make it difficult to establish what the Fig. 1.17 Sections from a 1960s movie of an Australian aboriginal man occlusion might have been in the absence of early loss of teeth, eating a kangaroo prepared in the traditional (barely cooked) fashion. Note gingivitis, and periodontal breakdown. The increase in malocclusion the activity of muscles, not only in the facial region, but throughout the in modern times certainly parallels the development of modern neck and shoulder girdle. (Courtesy M. J. Barrett.) civilization, but a reduction in jaw size related to disuse atrophy is hard to document, and the parallel with stress-related diseases can be carried only so far. Although it is difficult to know the Who Needs Treatment? precise cause of any specific malocclusion, we do know in general what the etiologic possibilities are, and these are discussed in some Protruding, irregular, or maloccluded teeth can cause three types detail in Chapter 5. of problems for the patient: (1) social discrimination because of What difference does it make if you have a malocclusion? Let’s facial appearance; (2) problems with oral function, including now consider the reasons for orthodontic treatment. difficulties in jaw movement (muscle incoordination or pain), 10 SE C T I O N I The Orthodontic Problem temporomandibular dysfunction (TMD), and problems with normal speech. As methods to quantify functional adaptations of mastication, swallowing, or speech; and (3) greater susceptibility this type are developed, it is likely that the effect of malocclusion to trauma, periodontal disease, or tooth decay. on function will be appreciated more than it has been in the past. The relationship of malocclusion and adaptive function to TMD, manifesting with pain in and around the TMJ, is understood much Psychosocial Problems better now than only a few years ago. The pain may result from A number of studies in recent years have confirmed what is intui- pathologic changes within the joint but more often is caused by tively obvious: that severe malocclusion is likely to be a social muscle fatigue and spasm. Muscle pain almost always correlates handicap. The usual caricature of an individual who is none too with a history of clenching or grinding the teeth as a response to bright includes protruding upper incisors. A witch not only rides stressful situations or of constantly posturing the mandible to an a broom, she has a prominent lower jaw that would produce a anterior or lateral position. Class III malocclusion. Well-aligned teeth and a pleasing smile Some dentists have suggested that even minor imperfections carry positive status at all social levels and ages, whereas irregular in the occlusion serve to trigger clenching and grinding the teeth. or protruding teeth carry negative status.12,13 Appearance can and If this were true, it would indicate a real need for perfecting the does make a difference in teachers’ expectations and therefore in occlusion in everyone, to avoid the possibility of developing facial student progress in school, in employability, and in competition muscle pain. Because the number of people with at least moderate for a mate. This places the concept of “handicapping malocclusion” degrees of malocclusion (50% to 75% of the population) far exceeds in a larger and more important context. If the way you interact the number with TMD (5% to 30%, depending on which symptoms with other individuals is affected constantly by your teeth, your are examined), it seems unlikely that dental occlusion alone is dental handicap is far from trivial. There is no doubt that social enough to cause hyperactivity of the oral musculature. A reaction responses conditioned by the major deviations from the usual to stress usually is involved. Some individuals react by clenching appearance of the face and teeth can severely affect quality of life and grinding their teeth; others develop symptoms in other organ and self-esteem in a way that compromises an individual’s whole systems. An individual almost never has both ulcerative colitis adaptation to life.14 (also a common stress-induced disease) and TMD. It is interesting that psychic distress caused by disfiguring dental Some types of malocclusion (especially posterior crossbite with or facial conditions is not directly proportional to the anatomic a shift on closure) correlate positively with TMJ problems and severity of the problem. An individual who is grossly disfigured other types do not, but even the strongest correlation coefficients (e.g., with a distorted nose and scarred lip after cleft lip or palate are only 0.3 to 0.4. This means that for the great majority of repair) can anticipate a consistently negative response.15 An patients, there is no association between malocclusion and TMD.19 individual with an apparently less severe problem (e.g., a deficient Therefore orthodontics as the primary treatment for TMD almost chin or protruding maxillary incisors) is sometimes treated differently never is indicated, but in special circumstances (see Chapter 18) because of this but sometimes not. It seems to be easier to cope it can be a useful adjunct to other treatment for the muscle pain. with a defect if other people’s responses to it are consistent than if they are not. Unpredictable responses produce anxiety and can Relationship to Injury and Dental Disease have strong deleterious effects.16 The impact of a physical defect on an individual also will be strongly influenced by that person’s Malocclusion, particularly protruding maxillary incisors, can increase self-esteem. The result is that the same degree of anatomic abnormal- the likelihood of an injury to the teeth (Fig. 1.18).20 There is about ity can be merely a condition of no great consequence to one one chance in three that a child with an untreated Class II maloc- individual but a genuinely severe problem to another. clusion will experience trauma to the upper incisors, but most of In short, it seems clear that the major reason people seek the time the result is only minor chips in the enamel.21 For that orthodontic treatment is to minimize psychosocial problems related reason, reducing the chance of injury when incisors protrude is to their dental and facial appearance.17 These problems are not “just cosmetic.” They can have a major effect on the quality of life,18 and the evidence presented in the final section of this chapter documents that orthodontic treatment can improve it. Oral Function Although severe malocclusion surely affects oral function, oral function adapts to form surprisingly well. It appears that maloc- clusion usually affects function not by making it impossible but by making it difficult, so that extra effort is required to compensate for the anatomic deformity. For instance, everyone uses as many chewing strokes as it takes to reduce a food bolus to a consistency that is satisfactory for swallowing, so if chewing is less efficient in the presence of malocclusion, either the affected individual uses more effort to chew or settles for less well-masticated food before swallowing it. Tongue and lip posture adapt to the position of the teeth so that swallowing rarely is affected (see Chapter 5). Similarly, Fig. 1.18 Fractured maxillary central incisors in a 10-year-old girl. There almost everyone can move the jaw so that proper lip relationships is almost one chance in three of an injury to a protruding incisor, though exist for speech, so distorted speech is rarely noted even though fortunately the damage rarely is this severe. Most of the accidents occur an individual may have to make an extraordinary effort to produce during normal activity, not in sports.  CHAPTER 1 Malocclusion and Dentofacial Deformity in Contemporary Society 11 not a strong argument for early treatment of all Class II problems (see Chapter 13), but with previous trauma and age younger than 9 years, the risk of additional trauma is 8.4 times higher than in Evidence of Clinical Effectiveness: children with no history of trauma.22 For such a child, retracting A Hierarchy of Quality the incisors (but not growth modification) is indicated. Extreme overbite, so that the lower incisors contact the palate, can cause significant tissue damage leading to early loss of the upper incisors and also can result in extreme wear of incisors. Both of these effects can be avoided by orthodontic treatment (see Chapter 18). It certainly is possible that malocclusion could contribute to Meta-analysis, multiple trials both dental decay and periodontal disease by making it harder to care for the teeth properly or by causing occlusal trauma. Multiple studies have indicated, however, that malocclusion has little if any impact on diseases of the teeth or supporting structures.23 An Randomized clinical trial individual’s willingness and motivation determine oral hygiene much more than how well the teeth are aligned, and presence or absence of dental plaque is the major determinant of the health Prospective study, nonrandom of both the hard and soft tissues of the mouth. If individuals with assignment Systematic Review malocclusion are more prone to tooth decay, the effect is small compared with hygiene status. Occlusal trauma, once thought to Retrospective study, inclusion be important in the development of periodontal disease, now is based only on pretreatment characteristics recognized to be a secondary, not a primary, etiologic factor. There is only a tenuous link between untreated malocclusion and major periodontal disease later in life. Retrospective study, inclusion Could orthodontic treatment itself be an etiologic agent for based on treatment response oral disease? Long-term studies have shown no indication that orthodontic treatment increased the chance of later periodontal problems.24 The association between early orthodontic and later Case report(s) periodontal treatment appears to be only another manifestation of the phenomenon that one segment of the population seeks dental treatment while another avoids it. Those who have had one Unsupported opinion of expert type of successful dental treatment, such as orthodontics in child- hood, are more likely to seek another such as periodontal therapy in adult life. Fig. 1.19 Evidence of clinical effectiveness: a hierarchy of quality. In summary, it appears that both psychosocial and functional handicaps can produce significant need for orthodontic treatment. The evidence is less clear that orthodontic treatment reduces the development of later dental disease. than anything else, the probability that an accurate conclu- sion can be drawn from the group of patients who have been Type of Treatment: Evidence-Based studied. The unsupported opinion of an expert is the weakest Selection form of clinical evidence. Often, the expert opinion is sup- ported by a series of cases that were selected retrospectively from If treatment is needed, how do you decide what sort of treatment practice records. to use? The present trend in health care is strongly toward evidence- The problem with that, of course, is that the cases are likely to based treatment—that is, treatment procedures should be chosen have been selected because they show the expected outcome. A on the basis of clear evidence that the selected method is the most clinician who becomes an advocate of a treatment method is natu- successful approach to that particular patient’s problem(s). The rally tempted to select illustrative cases that show the desired better the evidence, the easier the decision. outcome, and if even he or she tries to be objective, it is difficult to avoid introducing bias. When outcomes vary, as they often do, picking the cases that came out the way they were supposed to Randomized Clinical Trials: The Best Evidence and discarding the ones that didn’t is a great way to make your Orthodontics traditionally has been a specialty in which the opinions point. Information based on selected cases, therefore, must be of leaders were important, to the point that professional groups viewed with considerable reserve. One important way to control coalesced around a strong leader. Angle, Begg, and Tweed societies bias in reporting the outcomes of treatment is to be sure that all still exist, and new ones whose primary purpose is to promulgate of the treated cases are included in the report. their leaders’ opinions are still being formed in the 21st century. If retrospective cases are used in a clinical study, it is much As any professional group comes of age, however, there must be better to select them on the basis of their characteristics when a focus on evidence-based rather than opinion-based decisions. treatment began, not on the outcome, and better yet to select the That very much includes orthodontics. cases prospectively before treatment begins. Even then, it is quite As Fig. 1.19 illustrates, a hierarchy of quality exists in the possible to bias the sample so that the “right” patients are chosen. evidence available to guide clinical decisions. It reflects, more After experience with a treatment method, doctors tend to learn 12 SE C T I O N I The Orthodontic Problem subtle indications that a particular patient is or is not likely to treatment time, and that sequential radiographs usually are required. respond well, although they may have difficulty verbalizing exactly Radiation exposure for untreated children is problematic. At present, what criteria they used. Identifying the criteria associated with it is very difficult to get permission to expose children to x-rays success or failure is extremely important, and a biased sample that will be of no benefit to them personally. This means the makes that impossible. longitudinal growth studies in the mid-20th century that used a For this reason, the gold standard for evaluating clinical pro- series of cephalometric radiographs of untreated children cannot cedures is the randomized clinical trial, in which patients are be repeated now. In the absence of newer data, they still are being randomly assigned in advance to alternative treatment procedures. used to provide control data in studies involving growth The great advantage of this method is that random assignment, if modification—although it is well established that in the United the sample is large enough, should result in a similar distribution States and almost all other countries, children now grow larger of all variables between (or among) the groups. Even variables that and mature more quickly than at the time of those studies (see were not recognized in advance should be controlled by this type Fig. 3.7). When historic controls are the best that are available, it of patient assignment—and in clinical work, important variables is better to have them than nothing, but the limitations must be often are identified only after the treatment has been started or kept in mind. Growth magnitudes and timing, along with so much even completed. Clinical trials in orthodontics are referred to in else, have changed in the last 50 years. some detail throughout this book. Systematic reviews of the literature, which look primarily at An additional way to gain better data for treatment responses papers based on retrospective data, have received considerable when multiple randomized clinical trials exist is the application emphasis in the last few years. A typical search for reports on of meta-analysis. This draws on recently developed statistical the subject of the systematic review yields a large number of techniques to group the data from several studies of the same papers to be evaluated. Most are discarded because of obvious phenomenon. Orthodontic research is an excellent example weaknesses in the methods, poor quality of the data, or insuf- of an area in which numerous small studies have been carried ficient data. The remaining papers are evaluated for statistical out toward similar ends, often with protocols that were at least significance. The key step, of course, is discarding the poor papers somewhat similar but different enough to make comparisons and keeping the good ones, which inevitably requires judgment difficult. Meta-analysis is no substitute for new data collected on the part of those conducting the review. Unfortunately, many with precise protocols, and including poorly done studies in a recent systematic reviews conclude only that the data are not meta-analysis carries the risk of confusing rather than clarifying the good enough to provide a definitive answer, and such reviews are issue.25 Nevertheless, applying meta-analysis to clinical questions not helpful to clinicians who have to do something even if it’s has considerable potential to reduce uncertainty about the best wrong. Fortunately, experienced clinicians can perceive patterns treatment methods. in the data that provide insight into clinical significance, especially An important caveat for meta-analyses is that the emphasis on when the evidence allows comparing the pluses and minuses of statistical significance should not lead to overlooking the difference different methods even though statistically significant differences between statistical and clinical significance. Statistical significance were not demonstrated. The depiction of systematic reviews in evaluates the chance that a difference in the data set would be due Fig. 1.19 is meant to emphasize that caution is needed when they just to the random variation that affects any group of treatment are evaluated. responses; clinical significance evaluates whether a difference of A final important consideration is that what clinicians consider this magnitude would have any practical effect on the provision the important aspects of outcomes of treatment may or may not of treatment. Not all statistical differences are clinically significant, coincide with how patients perceive the outcome. In orthodontics, and sometimes differences that do not reach statistical significance it is apparent that the appearance of the teeth on smile is a key nevertheless may indicate a clinical advance. outcome for patients. Fortunately, what the patients think now Unfortunately, randomized trials and meta-analysis cannot be receives more attention than it did all the way through the 20th used in many situations for ethical or practical reasons. For instance, century, and data for the acceptable range of tooth display have a randomized trial of extraction versus nonextraction orthodontic become available recently.13 Less fortunately, characteristics of the treatment would encounter ethical concerns, would be very difficult dental occlusion (e.g., the relationship of the dental midlines) that and expensive to organize and manage if ethical difficulties could are not important to patients still are considered very important be overcome, and would require following patients for many years by some dentists when they evaluate the outcome of orthodontic to evaluate long-term outcomes. treatment. Patient-centered treatment does not mean the patient is always right, but it does mean that the patient’s point of view has to be kept in mind both when treatment is planned and when Retrospective Studies: Control Group Required its success is evaluated. A second acceptable way to replace opinion with evidence is by The era of orthodontics as an opinion-driven specialty clearly careful retrospective study of treatment outcomes under well-defined is at an end. In the future, it will be evidence driven, which is all conditions. The best way to know—often the only way to know— for the best. In the meantime, clinical decisions still must be made whether a treatment method really works is to compare treated using the best information currently available. When the latest patients with an untreated control group. For such a comparison new method appears with someone’s strong recommendation and to be valid, the two groups must be equivalent before treatment a series of case reports in which it worked very well, it is wise to starts. Unless the pretreatment groups were statistically adjusted, remember the aphorism “Enthusiastic reports tend to lack controls; you cannot with any confidence say that differences afterward well-controlled reports tend to lack enthusiasm.” were due to the treatment. In this and the subsequent chapters, recommendations for There are a number of difficulties in setting up control groups treatment are based insofar as possible on solid clinical evidence. for orthodontic treatment. The principal ones are that the controls When this is not available, the authors’ current opinions are provided must be followed over a long period of time, equivalent to the and labeled as such.  CHAPTER 1 Malocclusion and Dentofacial Deformity in Contemporary Society 13 Demand for Treatment BOX 1.1 Index of Treatment Needs (IOTN) Treatment Grades Epidemiologic Estimates of Orthodontic Grade 5 (Extreme/Need Treatment) Treatment Need 5.i Impeded eruption of teeth (except third molars) due to crowding, Psychosocial and facial considerations, not just the way the teeth displacement, the presence of supernumerary teeth, retained fit, play a role in defining orthodontic treatment need. For this deciduous teeth, and any pathologic cause. reason, it is difficult to determine who needs treatment and who 5.h Extensive hypodontia with restorative implications (more than one does not just from an examination of dental casts or radiographs. tooth per quadrant) requiring preprosthetic orthodontics. 5.a Increased overjet greater than 9 mm. Nevertheless, it seems reasonable that the severity of a malocclusion 5.m Reverse overjet greater than 3.5 mm with reported masticatory and correlates with need for treatment, and as we will discuss in more speech difficulties. detail here, there is good evidence to support that correlation. This 5.p Defects of cleft lip and palate and other craniofacial anomalies. assumption is necessary when treatment need is estimated for 5.s Submerged deciduous teeth. population groups. Several indices for scoring how much the teeth deviate from Grade 4 (Severe/Need Treatment) 4.h Less extensive hypodontia requiring prerestorative orthodontics or the normal, as indicators of orthodontic treatment need, were orthodontic space closure (one tooth per quadrant). proposed in the 1970s but not widely accepted for the screening of 4.a Increased overjet greater than 6 mm but less than or equal to potential patients. There now are two major methods for scoring the 9 mm. severity of malocclusion: the peer assessment rating (PAR) system, 4.b Reverse overjet greater than 3.5 mm with no masticatory or developed in the United Kingdom, and the American Board of speech difficulties. Orthodontics (ABO) discrepancy index, developed in the United 4.m Reverse overjet greater than 1 mm but less than 3.5 mm with States. It is important to keep in mind that these systems consider recorded masticatory or speech difficulties. just the dentition, not skeletal or facial characteristics. 4.c Anterior or posterior crossbites with greater than 2 mm PAR scores are calculated from measurements of maxillary and discrepancy between retruded contact position and intercuspal mandibular anterior alignment (crowding and spacing), buccal position. 4.l Posterior lingual crossbite with no functional occlusal contact in segment occlusion (anteroposterior, transverse, and vertical), overjet one or both buccal segments. or reverse overjet, overbite, and midline discrepancies, with use of 4.d Severe contact point displacements greater than 4 mm. a weighting scale for each characteristic.26 ABO index scores are 4.e Extreme lateral or anterior open bites greater than 4 mm. calculated similarly, with the difference primarily that it adds three 4.f Increased and complete overbite with gingival or palatal trauma. cephalometric measurements.27 Both systems were developed as a 4.t Partially erupted teeth, tipped, and impacted against adjacent teeth. way to objectively determine the amount of improvement achieved 4.x Presence of supernumerary teeth. during treatment but have been shown to correlate reasonably well Grade 3 (Moderate/Borderline Need) with expert opinions of orthodontic treatment need. 3.a Increased overjet greater than 3.5 mm but less than or equal to The Index of Treatment Need (IOTN), developed by Brook 6 mm with incompetent lips. and Shaw in the United Kingdom,28 was designed to evaluate need 3.b Reverse overjet greater than 1 mm but less than or equal to for treatment. It places patients in five grades from “no need for 3.5 mm. treatment” to “treatment required” that correlate reasonably well 3.c Anterior or posterior crossbites with greater than 1 mm but less with clinician’s judgments of need for treatment. The index has a than or equal to 2 mm discrepancy between retruded contact dental health component derived from occlusion and alignment position and intercuspal position. (Box 1.1 outlines the criteria and shows how the score is calculated) 3.d Contact point displacements greater than 2 mm but less than or and an esthetic component derived from comparison of the dental equal to 4 mm. 3.e Lateral or anterior open bite greater than 2 mm but less than or appearance versus standard photographs (Fig. 1.20). There is a equal to 4 mm. surprisingly good correlation between treatment need assessed by 3.f Deep overbite complete on gingival or palatal tissues but no the dental health and esthetic components of IOTN (i.e., children trauma. selected as needing treatment based on one of the