Systemized orthodontic treatment mechanics

Richard P McLaughlin

San Diego, California, USA

John C Bennett

London, UK

Hugo J Trevisi

Présidente Prudente, Brazil

M Mosby



An imprint of Harcourt Publishers Limited © Mosby International Ltd 2001

KM is a registered trademark of 1 Iarcourt Publishers Limited

The right of Dr Richard P McLaughlin, Dr John C Bennett and Dr I lugo I Trevisi to be identified as authors of this work has been asserted by them in accordance with the Copyright, Designs and Patents Act 1988

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior permission of ihe publishers (Permissions Manager, Harcourt Health Sciences, Robert Stevenson House, 1-3 Baxter's Place, Leith Walk, Edinburgh EH1 3AF), or a licence permitting restricted copying in the llniied Kingdom issued by the Copyright Licensing Agency, 90 Tottenham Court Road, London W1P OI.P.

First published 2001

ISBN 072343171X

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

Library of Congress Cataloging in Publication Data

A catalog record for this book is available from the Library of Congress

The publisher's policy is to use paper manufactured from sustainable forests

Typeset by IMH(Cartrif), Loanhead, Scotland

Printed in Spain '


Goal-directed orthodontic treatment is extremely important. If the goals of treatment goals are not kept in mind from the diagnosis and treatment-planning phase through to the phase of retention, continuous errors can be made. Treatment then becomes inefficient and results are disappointing. However, if treatment goals are kept constantly in mind, results become much more consistent, and when minor compromises must occur, the reasons for these can be understood, and many of them can be avoided in the future. The goals of treatment for the authors are listed below. They hope the reader will keep these in mind when reading the text, to provide greater insight into their intent. It is hoped that in that way it will have more meaning. The treatment goals are:

• Condyles in a seated position - in centric relation

• Relaxed healthy musculature

• Ideal functional movements - a mutually protected occlusion

• Periodontal health

• Best possible aesthetics.

This book was originally planned as a second edition of the first Bennett and McLaughlin text, entitled Orthodontic Treatment Mechanics and the Preadjusted Appliance, published in 1993. However, there have been so many technological changes and improvements over the past 8 years that an entirely next text became necessary, supplementing the general message of the first.

A second Bennett and McLaughlin text, entitled Orthodontic Management of the Dentition with the Preadjusted Appliance, was published in 1997. This devoted a chapter to each tooth in the dentition, emphasizing clinical situations relating to each tooth. It evolved into a far more extensive project than initially intended, and required a substantial manuscript to cover the wide range of material.

With this third textbook, the intention is to return to a concise format somewhat similar in scope to the first. Its primar>' focus is on orthodontic treatment mechanics, in particular intra-arch considerations, or the maneuvers involved in alignment and maintenance of the dentition in each individual arch. These factors are dealt with in Chapter 5 'Anchorage control during tooth leveling and aligning', Chapter 6 'Arch leveling and overbite control'. Chapter 9 'Space closure and sliding mechanics', and Chapter 10 'Finishing the case'. Inter-arch considerations, or the coordination of the upper and lower arches in three planes of space within the facial complex, are also given a slightly greater emphasis than previously; in particular, Chapter 7 and 8 deal with Class II treatment and Class III treatment, respectively. These are extensive subjects, but an attempt has been made to present a concise and up-to-date perspective on the general management of these two categories of case.

The text discusses both extraction and non-extraction treatments. Greater emphasis is placed on extraction treatment, because the mechanics of these cases are more complex. This is not to infer that the authors treat more cases on an extraction basis; in general, every effort is made to treat on a non-extraction basis wherever possible, and the authors treat a much higher percentage of cases in this manner.

After using the original 'Straight-Wire® Appliance' (SWA) for nearly 20 years, it became important to provide modifications to the appliance to more closely complement modern treatment mechanics. Chapter 2 on appliance specification deals with the rationale behind the changes made in the appliance system. Emphasis is placed on the new variations, as well as on the versatility of the appliance (comparisons are restricted to the original SWA and do not refer to other orthodontic appliances).

A bracket placement chart, developed in 1995, has been most valuable in the important area of bracket placement. The text discusses recent developments in bracket-placement techniques - renewed interest in indirect bonding, for instance, has occurred because of improved materials, such as adhesive systems and tray materials. An overview of this subject is provided.

Archwire technology has improved dramatically over the past 8 years. The use of heat-activated nickel-titanium wires (I IAN'L) has become a vital part of the treatment system, and, consequently, modifications to the treatment mechanics have occurred. Information on HANT wires, along with a discussion of archwire sequencing, is presented in Chapter 5 'Anchorage control during tooth leveling and aligning'.

Since its introduction in the 1970s, attempts have been made with the preadjusted appliance to select and use a single arch form on most patients. Even using the most frequently observed arch form in the orthodontic population, the authors observed numerous cases that were either too narrow or over-expanded. Therefore, Chapter 4 is dedicated to the subject of arch form, and presents efficient techniques for managing arch form selection and archwire coordination.

Chapter 11 is dedicated to retention protocol, which is a new subject lor this text. It gives an overview of the protocol, as well as describing the methods most frequently used by the authors.

Drs Bennett and McLaughlin have spent a great deal of time with Dr HugoTrevisi of Presidente Prudente, Brazil, who has used this system of treatment for over 20 years. Dr Trevisi has provided a number of important insights into the technique, and therefore a decision was made to introduce him as a third author of the text, thus reinforcing its international perspective, and bringing together the best ideas from three continents.

The success of a project of this scope and complexity depends on the commitment of many individuals. The authors acknowledge and appreciate the documentation skills and extra photography carried out by the assistants in each of the authors' practices. The work of Patty Knecht and Laura Plante in San Diego, and Cath West in London, was invaluable, as were the interpreting skills of Michelle Trevisi Araujo in Brazil.

Text and illustrations were assembled in London, and production and publication were handled by the Mosby team in Edinburgh. On behalf of the publishers, Barbara Simmons, project development manager, and her colleagues contributed unfailing energy and enthusiasm to this project. Their professionalism and respect of the authors' sometimes unconventional work patterns helped make the publishing process both efficient and enjoyable. The authors freely acknowledge the valuable help and advice given by Michael Parkinson, commissioning editor. They also wish to make particular mention of the contribution of Graham Birnie, who laboriously checked and edited the original text, and of Judith Wright, who was responsible for the design. Looking ahead, there are plans for at least 12 foreign co-editions, and the authors are grateful to Ilona Turniak for her work on this important aspect of publication.

Chapters 7 and 8 include information on the diagnostic methods of Dr Bill Arnett, who gave considerable time and assistance, and made important material available for Chapter 8. The authors are also grateful for Dr Fredrik Bergstrand's advice on bonding, and for the photograph. The authors' work has benefited over the course of many years from the input of international colleagues - although space constraints make it impossible to acknowledge each individually, their friendship, enthusiasm and support does not go unrecognized.

The following technical production information may be of interest. The original text was generated in Apple Works 5.0 on a Macintosh G4 computer. Line drawings were created in Apple Freehand 8.0, and teeth are represented approximately to scale, with form based on dental anatomy texts. The color photographs were mainly originated in Kodachrome 64. No digital enhancement of clinical material took place. Apart from the removal of red-eye on some of the facial photographs, it has been published directly from the original Kodachrome slides.

Finally, the authors would like to thank 3M Unitek for its efforts in designing (he new appliance, as well as for support in the other areas of the treatment system, such as bracket-placement gauges and charts.


1. A brief history and overview of treatment mechanics 1

2. Appliance specifications - variations and versatility 25

3. Bracket positioning and case set-up 55

4. Arch form 71

5. Anchorage control during tooth leveling and aligning 93

6. Arch leveling and overbite control 129

7. An overview of Class II treatment 161

8. An overview of Class III treatment 217

9. Space closure and sliding mechanics 249

10. Finishing the case 279

11. Appliance removal and retention protocols 305 Index 319

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