Occlusal Contact Changes in Patients Treated with Clear Aligners

Abstract

Introduction: Clear aligners are commonly used in orthodontic treatment to correct malocclusions and enhance smile esthetics. There is little quantitative data on how occlusal contacts are altered by clear aligners. This study uses digital intra-oral scans to evaluate how clear aligners affect occlusal contacts and to determine the influence of sex and age on contact changes. Results are compared to contact changes that occur during fixed appliance therapy. Methods: Patients included in this study were treated at the University of Washington orthodontic clinic between January 2017-August 2021 and in a local private practice between May 2016-February 2021. Inclusion criteria were a Class I malocclusion treated non-extraction with Invisalign and the presence of digital intra-oral scans obtained before treatment was initiated (T1) and post-treatment following debond (T2). Scans were imported into GOM Inspect Software (GOM Precise Industrial 3D Metrology, Braunschweig, Germany) and occlusal contacts were analyzed. Contacts studied ranged from 0-1.25 mm of space between maxillary and mandibular teeth and were grouped into five categories (tight, near, approximating, open, and no contacts). Analysis was done for the total contact area, anterior area, and posterior areas. The effect of age and sex on contact changes during clear aligner treatment was determined. Changes in occlusal contacts were compared to contact changes that occur during fixed appliance treatment using an existing dataset. Results: A total of 45 patients fit the eligibility criteria for this study. Clear aligners reduced the percentage of tight, near and approximating contacts while the percentage of open and no contacts increased. These changes in occlusal contacts were greater for the older age group studied. Sex influenced occlusal contact changes in the anterior dentition only where the decrease in near contacts and increase in open contacts was greater for males. These results for patients treated with clear aligners were similar to those for patients treated with fixed appliances; both treatment modalities reduce close occlusal contacts at the time active treatment is completed. Conclusions: Clear aligners reduce close contacts and increase open contacts. Overall contact changes during clear aligner treatment are influenced by age, and anterior contact changes are influenced by sex. Clear aligners and fixed appliances result in similar occlusal contact changes.