Finishing with clear aligner appliances: a systematic review

Objective: To determine the quality of finishing obtained with removable clear aligners, measured using the American Board of Orthodontics system (ABO) or the Peer Assessment Rating index (PAR). Materials and methods: Electronic databases - PubMed, EMBASE, SCIRUS, SCOPUS and Cochrane Library from 1966 to the second week of September 2017 were searched. Methodological shortcomings were highlighted and the quality of the studies was ranked using MINORS, a validated quality assessment tool. Results: Four relevant articles were selected (a retrospective cohort study, a descriptive uncontrolled case-control study and two descriptive controlled case-control studies). OGS categories that had scores with a statistically significant difference between the groups were buccolingual inclination, occlusal contacts, occlusal relationships and overjet. In these categories, on average the group treated with removable aligners lost more points than the braces group. There was a statistically significant difference between the passing rate (ABO) of both groups, 20.8% of the clear aligner group and 47.9% of the braces group (P.0052). The ABO Model Grading System (MGS) showed significantly correlated scores (range 0.8 + 1.0; P 0.05) for the categories buccolingual inclination, occlusal relations, and interproximal contacts. The alignment results (15.16 + 5.00 vs 6.00 + 3.78, P 0.001) and buccolingual inclination results improved significantly (7.00 + 3.14 vs 6.26 + 3.58, P 1/4 0.024). The smallest change was found in the rating of interproximal contact. In the clear aligner and braces group, OGS scores reflecting mean points lost for deviation from ideal show that only the scores in buccolingual inclinations (-3.55 + 1.36 and -5.85 2.68, respectively) and in occlusal contacts (-1.88 + 0.13 / -3.90 + 1.12, respectively) were significant. Regarding the results obtained using the PAR index, no differences between the measures evaluated in both groups were shown, although no result was statistically significant. Finally, a significant reduction in treatment time was indicated using the clear aligner system (13.35 + 8.63 months), when compared with conventional appliances (19.08 + 5.92 months). Conclusions: OGS scores were similar in both groups for rotations, marginal ridge heights, space closure and root alignment, but clear aligners' OGS qualifications for occlusal contacts, posterior torque, and anteroposterior discrepancies were worse than those obtained with braces. When comparing MGS scores it was shown that those for Invisalign for the alignment, buccolingual inclination, overjet, marginal ridges and interproximal contacts categories showed overall improvements after treatment. Finally, despite it being shown that both techniques were equally successful in treating Class I adult extraction cases, treatment time for the clear aligner system was shorter. Keywords: ABO, clear aligners, finishing, PAR