in
Invisalign
Orthodontic Treatment
Private Practice
Clinical Professor
Universities of Paris 5 and Paris 7
Paris, France
Paris, Chicago, Berlin, Tokyo, London, Milan, Barcelona, Istanbul, São Paulo, Mumbai, Moscow, Prague, and Warsaw |
First published in French in 2009 by Quintessence International, Paris
Les Traitements Orthodontiques Invisalign®
Disclaimer
This book expresses the author’s opinions and personal reflections, which are not necessarily those of Align Technology (Align), the manufacturer of the Invisalign system. Align neither contributed to the contents nor guarantees its exactness, nor authorized the disclosure of information not known to the public. Invisalign and ClinCheck are trademarks of Align.
© Quintessence International, 2011
Quintessence International
11 bis, rue d’Aguesseau
75008 Paris
France
All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher.
Unless otherwise indicated, all photos are courtesy of Align Technology.
Design: STDI, Lassay-les-Châteaux, France
Printing and Binding: EMD, Lassay-les-Châteaux, France
Printed in France
Cover | |
Table of Contents | |
Preface | |
1 | The Invisalign Concept |
What Is Invisalign? The Science of Invisalign Aligners: Thermoforming Development of Align Technology Advantages of the Invisalign System Disadvantages of the Invisalign System Examples of Ideal Initial Invisalign Cases Invisalign Protocol | |
2 | Biomechanics of Orthodontic Aligners |
Applications of Force in Orthodontics Advantages of Aligners Invisalign Treatment in a High-Risk Periodontal Case | |
3 | Clinical Records |
Impression-Taking Procedures Photographs Radiographs Important Clinical Points Future Development | |
4 | Diagnosis and Treatment Plan |
Diagnosis Treatment Plan | |
5 | Treatment Strategies |
Control of Tooth Movements: Attachment Types and Indications Control of Available Space Control of Anchorage Loss | |
6 | Indications and Contraindications |
Indications Contraindications Conclusion | |
Bibliography |
This book would not have been accomplished without:
• The constant support of the author’s family, despite his recurrent absence
• The editorial advice of Dr J.-M. Korbendau
• Dr A. Decker and his scientific and academic openness
The author would like to express his profound gratitude to all of them.
This book was written to provide the reader a tool for daily clinical use of the Invisalign system. It offers a summary of the author’s 8 years of clinical experience treating several hundred patients with this esthetic alternative orthodontic system that makes use of individualized and industrialized thermoformed polycarbonate overlay appliances called aligners. Clinical results obtained from various treatment types are shown, from the simplest to the most complicated cases, using aligners alone or in combination with other techniques, eg, fixed and surgical orthopedics or orthodontics.
The Invisalign system is unique in that, in order to obtain an optimal result, the clinician must be capable of planning in advance, even before the onset of treatment, the totality of the treatment plan. The fabrication of a series of aligners then follows, corresponding to the desired treatment objectives. This system requires considerable knowledge of orthodontics and biology to establish a sound diagnosis, as well as an understanding of the biomechanics of the appliances to ensure satisfactory movement of teeth and maxillary and mandibular bone.
To move teeth, orthodontists initially used removable and later fixed appliances to control and minimize undesirable tooth movements in three-dimensional space. The Invisalign system, in which the aligners have intimate contact with nearly the entire surface of the tooth crown, attempts to bring together the best qualities of removable and fixed appliances. Moreover, it provides an esthetic touch and undeniable comfort as well as easy oral hygiene access for patients.
The computer-assisted design of tooth movements (performed in a program called ClinCheck) to be carried out by the aligners gives orthodontists a new and fascinating way to treatment plan: programming in advance every desired movement according to their own diagnostic practices, treatment insight, and knowledge of the aligners’ biomechanics. According to their diagnosis and treatment plan, orthodontists can use ClinCheck to control:
• Velocity and direction of tooth movements
• Amount and frequency of force to be applied to these movements
• Anchorage and available space necessary for the planned movements
Through precise clinical cases, this book provides tools for ClinCheck application and management of space and anchorage required for desired tooth movements. It is not meant to be exhaustive, but rather a clinical introduction to this comfortable and effective orthodontic treatment concept.
The Invisalign |
What Is Invisalign?
• Invisalign is a minimally visible method for moving teeth without band, wire, or bracket.
• Invisalign therapy consists of a series of clear aligners that are worn to gradually move teeth (Fig 1-1).
• An Invisalign aligner is a custom-made, removable, comfortable dental retainer made from thermoformed medical polycarbonate, which is inert and compatible with human saliva. (See following section for details on thermoforming.)
• Each aligner is worn approximately 22 hours a day over a 2-week period for a total of over 300 hours. This leaves 2 hours a day for eating and toothbrushing.
• Aligners are replaced every other week on average to allow for gentle tooth movement over time according to the clinician’s diagnosis and treatment plan.
• Treatment duration, which can range from 3 to 30 months, and cost depend on the extent of tooth malpositioning and malocclusion.
The Science of Invisalign Aligners: Thermoforming
Thermoforming is the art of shaping thermoplastic materials with heat. Chemically, plastics consist of polymers that are made up of numerous monomers, which are organic molecules with nuclei that contain one carbon atom. Examples of natural polymers include proteins, rubber, collagen, and cellulose. The behavior of plastics mostly depends on the type of structure developed by polymerization of constituent monomers. To optimize their behavior, additives can be used to modify physical and chemical properties, and reinforcements can be added to modify mechanical properties.
In orthodontics, plastic materials in the form of soft, resilient round or square sheets (Fig 1-2) possessing excellent modeling properties are often used. These materials are inert, unaltered by saliva, and resistant to daily cleaning detergents. In addition, they are transparent, nontoxic, odorless, and tasteless.
Scheu et al proposed the first thermoforming machine to synthesize orthodontic appliances in 1966. Currently, two types of thermoforming machines, the Ministar and Biostar (Scheu Dental) (Fig 1-3), are available. Based on the principles of Scheu et al, Align Technology developed a large-scale, custom-made thermoforming system, which continues to undergo development and improvement (Fig 1-4).
Development of Align Technology
Design for the thermoforming system began in April 1997 when two MBA students from Stanford University, Zia Chishti and Kelsey Wirth, with the aid of a computer specialist, founded Align Technology in a garage in Palo Alto, California.
Chishti, who had suffered a relapse of mandibular incisor crowding after undergoing fixed orthodontic treatment, was required to wear a retainer to realign his mandibular anterior teeth. Disappointed by the relative slowness and limited progress of the relapse correction, Chishti conceived a revolutionary treatment concept: moving teeth with multiple appliances, whereby each tooth movement would be progressively conceptualized in three dimensions and virtually simulated by computer-assisted design software.
Appliances would be mechanically fabricated under computer control through a stereolithographic process to create resin models for each stage of desired tooth movement. These models would then be combined with thermoformed polycarbonate sheets, which would allow for mass-produced, custom-made aligners for orthodontic treatment.
This new concept for orthodontic treatment combined orthodontic principles of tooth movement, 21st century three-dimensional (3D) computer-aided design/computer-assisted manufacture (CAD/CAM) technology, and computer-assisted, mass-prototyping industrial processes, ultimately leading to the development of the Align Technology company and the current Invisalign treatment concept and techniques.
This new system gained clearance from the Food and Drug Administration in 1998. It was presented at the American Association of Orthodontists conference in 1999 and arrived in Europe in 2001. By broadening the range of applications, Invisalign has introduced a new method of orthodontic therapy.
Advantages of the Invisalign System
Minimal visibility
The transparency of Invisalign is a key feature and responds to the increasing demand from adult and adolescent patients for discreet orthodontic devices that are more suitable to social and professional life. In this way, Invisalign provides access to new patients who would otherwise decline treatment. Even patients with complications such as a missing tooth can benefit from Invisalign therapy. A prosthetic replacement tooth, called a pontic, can be incorporated into the appliance to replace an extracted tooth for esthetic enhancement (Fig 1-5).
Removability
During treatment, the patient can remove the aligners to eat or drink or for an important meeting. A storage container is supplied with the first aligner in the Patient Starter Kit (Fig 1-6).
Versatility
Toothbrushing and periodontal maintenance are well facilitated. Aligners can be inserted on natural or prosthetic teeth, definitive or provisional fixed prostheses (implant-supported or not), and resin and metal removable prostheses. Aligners can also serve as drug or chemical diffusers during orthodontic treatment and can administer substances such as toothbleaching products (Fig 1-7). To reduce periodontal risk, some periodontists recommend adding a drop of chlorhexidine gel at the molar region of the aligner. When the aligner is inserted in the mouth, the gel will flow and spread over the inner surface.
Comfort
Custom-made aligners adapt to teeth so that the margin coincides precisely with the dentogingival junction. Lips, cheeks, and tongue naturally slide along aligners as they would teeth. Fabricated by a precise industrial and automated process, aligners do not produce the irritation usually caused by the defects and irregular borders of appliances made by traditional methods. Wounds in the mouth caused by brackets, bands, wire, and other accessories of fixed appliances are also eliminated. Emergency treatment visits for rebonding of accessories or repairs of material breakage are also avoided.
Ease
Simple
The computer-assisted design process provides clear images of the progressive tooth movements, allowing the patient to easily understand the treatment plan and immediately visualize the progression of treatment (Fig 1-8).
Understandable