Evaluation of Invisalign Wear Protocol on the Efficacy of Tooth Movement in Four First-Premolar Extraction in Adolescent Patients: A Randomised Controlled Trial.

Abstract

Background: Different protocols exist regarding wear time of invisible aligners. There is no study that compared the effect of different protocols. The aim of this study was to assess the effect of Invisalign aligners in four first-premolar extraction treatments in adolescents using three aligner wear protocols, every 7, 10 and 14 days.

Materials and methods: In the experimental set-up, 50 participants were divided into three distinct groups: group A, with a regimen of changing aligners every 7 days; group B, with a 10-day interval for aligner replacement; and group C, where aligners were replaced every 14 days. The evaluation of occlusal adjustments was conducted employing the Discrepancy Index (DI) and the Cast-Radiograph Evaluation (CRE), as defined by the American Board of Orthodontics for the purpose of recording orthodontic outcomes. The treatment duration, number of maxillary and mandibular Invisalign aligners, and number of Invisalign restarts were simultaneously recorded and evaluated. The data set was statistically examined using ANOVA, complemented by the F-test, least significant difference (LSD) method and Tamhane's T2 test.

Results: The final sample size for analysis is 45 cases, with five cases lost to follow-up. Before treatment, the three groups showed no significant difference in the degree of malocclusion or each item of DI (p > 0.05). Posttreatment, within groups, and regardless of the wearing protocol, the total CRE scores demonstrated no statistically significant differences (p > 0.05). For the other items, groups A and C completed occlusal relations and interproximal contacts significantly better than did group B (p < 0.05). The group C cases had the least number of Invisalign refinement (3.93 ± 0.96 vs. 4.93 ± 0.70 vs. 6.00 ± 1.25, p < 0.05), but the treatment duration and number of Invisalign aligners were not significantly different (p > 0.05).

Conclusions: The different treatment timing protocols showed equivalent effectiveness regarding treatment outcome, with significantly improved results for the 7- and 14-day protocol in terms of occlusal relations and interproximal contacts. The attainment of comparable clinical accuracy between the 7- and 14-day protocol, within a treatment duration of fewer than 3 months, indicates that the 7-day protocol can be deemed an effective treatment approach.