Complex Orthodontic Treatment Using a New Protocol for the Invisalign Appliance ROBERT L. BOYD, DDS, MED
he Invisalign* system was introduced at an orthodontic meeting in 19991 and first described in a peer-reviewed publication in 2000.2 Controversy remains over whether the system is appropriate for moderate-to-difficult cases.3-19 Early longitudinal clinical trials demonstrated successful use of Invisalign for tipping movements, incisor rotations, and closure of naturally occurring spaces.17-19 The system was less effective in more difficult procedures such as extraction space closure. These trials were conducted during the first four years of appliance development, however, when significant problems existed with bodily movement, root torquing, extrusion, and premolar and canine rotation. One of the studies tested soft and hard aligner materials that were never used commercially17,18 (Invisalign appliances are now manufactured using a material of intermediate stiffness). It also evaluated whether a one- or two-week interval between aligners was more effective (for the past eight years, the standard protocol has been two weeks of wear for each aligner). Another study *Registered trademark of Align Technology, Inc., 881 Martin Ave., Santa Clara, CA 95050; www.aligntech.com.
showed predictable intrusion using clear aligners.19 Both of the longitudinal trials found a statistically significant reduction of plaque and gingivitis during treatment. Numerous other studies have shown that orthodontic treatment using fixed appliances often increases plaque and gingivitis, even when a highly structured preventive program is followed to minimize the effects on periodontal tissues and enamel.20,21 An early cross-sectional study compared the first 50 consecutive clear aligner cases treated by the senior author to 50 matched cases treated with fixed appliances.12 Fixed appliances generally yielded better results than the clear aligners, but the author had more than 25 years of experience with fixed appliances, and the aligner patients were treated between 1999 and 2002. More recently, successful outcomes have been reported from Invisalign treatment of patients with more complex malocclusions.11,13-15 This article reports on four patients of various ages with moderate-to-severe malocclusions who were successfully treated using preliminary versions of a new Invisalign protocol. Case Selection Many patients who request Invisalign treatment have previously undergone orthodontic treatment with fixed appliances and do not want to repeat the experience.11 Esthetic concerns are often a significant factor for adult patients, many of whom are unwilling to wear braces, but teenagers also request Invisalign nowadays because they do not want the look of fixed appliances.11 In addition, Spear reported that patients who require minor restorative dentistry or bleaching tend to
Dr. Boyd is a Contributing Editor of the Journal of Clinical Orthodontics and is Frederick T. West Endowed Professor and Chair, Department of Orthodontics, Arthur A. Dugoni School of Dentistry, University of the Pacific, 2155 Webster St., San Francisco, CA 94115; e-mail: firstname.lastname@example.org.
VOLUME XLI NUMBER 9
© 2007 JCO, Inc.
Complex Orthodontic Treatment Using a New Invisalign Protocol
prefer the combination of orthodontic treatment with less invasive restorative dentistry to extensive full coronal restorations and no orthodontic treatment.22 Patients with short dental roots may be better candidates for clear aligners than for fixed appliances. A recent longitudinal study of 100 consecutive Invisalign patients showed no measurable root resorption.23 In contrast, an average 10% of patients treated with fixed appliances have clinically significant root resorption of at least 3mm.24,25 Clear aligners may also be a good choice for patients with mild anterior open bite.11 The double thickness of the clear plastic appliances on the occlusal surfaces, in...
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