Assessment of invisalign treatment outcomes using the ABO model grading system

Background: A systematic review to determine the treatment effects of the Invisalign system showed that no treatment indications for, or limitations of, Invisalign treatment were supported with scientific evidence. This study was designed to evaluate Invisalign treatment outcomes in mild to moderate malocclusions using the Model Grading System (MGS) of the American Board of Orthodontics. Methods: A total of 425 Invisalign cases were identified from an orthodontic private practice in Buffalo, New York. Of the 425 cases, 119 met the inclusion criteria of having full permanent dentition with a Discrepancy Index (DI) score between 10 and 20 and having been treated completely with Invisalign without extraction. From those 119 cases, 31 had a complete set of records pre- and post-treatment. The pre- and post-treatment models were assessed using the MGS of the American Board of Orthodontics. The Wilcoxon signed rank test was used to compare the pre- and post-treatment MGS scores in all categories. Results: The mean scores of all of the MGS categories were improved after treatment, with the exceptions of the occlusal contacts and occlusal relationships categories. The improvements were statistically significant in scores in the alignment category (15.16 ± 5.00 vs. 6.00 ± 3.78; P < 0.001) and the buccolingual inclination category (7.00 ± 3.14 vs. 6.26 ± 3.58; P= 0.024) and the total MGS score (45.03 ± 7.47 vs. 35.87 ± 9.36; P < 0.001). Conclusion: Invisalign treatment when used in mild to moderate malocclusions was effective in correcting tooth alignment and buccolingual inclination; however, it had a negative effect on posterior occlusal contacts and occlusal relationships.