Outcome of Invisalign and traditional orthodontic treatment using PAR index

Invisalign has become a popular choice for orthodontic treatment of adult patients because of the esthetics and comfort of the clear removable aligners compared with conventional braces. However, due to insufficient clinical research, the effectiveness of Invisalign treatment remains questionable among clinicians. Purpose: The aim of this retrospective study was to compare the outcomes of orthodontic treatment with Invisalign to that of conventional braces. Methods: In this study, the pre-and post-treatment study models of cases treated with conventional fixed appliances (N=20) and with Invisalign (N=20) were used. The pre-treatment sample of both groups consisted of Class I malocclusion cases with crowding or spacing of 2-4 mm/arch, rotations of less than 45 degrees, overbite of 20-50% and overjet of 2-4 mm that were treated without extraction of teeth. Pre-and post-treatment casts were assigned peer assessment rating (PAR) scores by a single investigator calibrated for the PAR index. Intraexaminer reliability was evaluated by a duplicate scoring of 5 Invisalign and 5 conventionally treated study models at a 2 week-interval. The percent improvement in the mean PAR score was used to assess the treatment success. Data were analyzed using one way ANOVA to evaluate whether there were significant differences between the groups. The statistical significance level was p<0.05. Results: Although there was a substantial improvement in outcomes in patients treated with Invisalign, there was statistically significant difference in the percent improvement between the groups (91.80 % ± 4.99 for braces group vs. 68.7 ± 4.99 for Invisalign group, p<0.05). Conclusions: According to the PAR index, conventional fixed appliances achieved better results in the treatment of Class I mild crowding malocclusions . .