Invisalign treatment with mandibular advancement: A retrospective cohort cephalometric appraisal

Abstract

Objective: To examine the skeletal, dental, and soft-tissue cephalometric effects of class II correction using Invisalign's mandibular advancement feature in growing patients. Materials and Methods: A retrospective cohort clinical study was performed on cases that were started between 2017 and 2019. A total of 32 patients (13 females, 19 males), with an average age of 13 years old (9.9-14.8 years) had undergone Invisalign treatment (Align Technology, Inc., San Jose, CA) wherein the mandibular advancement phase was completed were included. Photos, digital study models, and cephalograms were taken once during the patients' initial visit and again upon completing the mandibular advancement phase of treatment. The number of aligners worn and the time of treatment in months was recorded for each subject. Cephalometric analysis was performed and overjet and overbite were measured. Statistical analysis was performed using SPSS statistical software (version 25; SPSS, Chicago, Ill) and the level of significance was set at P <0.05. Descriptive statistics were performed to generate means and differences for each cephalometric measurement as well as patient data including age, treatment time, and aligner number. Differences between measurements from patients before treatment (T1) and after treatment (T2) with the mandibular advancement feature were evaluated using a paired t-test. Results: All 32 patients had multiple jumps staged for the precision wings, i.e., incremental advancement. The average length of treatment for the MA phase was 9.2 months (7.5-13.8 months) and the average number of aligners used during this time was 37 (30-55). Statistically significant differences between T1 and T2, in favor of class II correction, were observed in the ANB angle, WITS appraisal, facial convexity, and mandibular length. The nasolabial angle, overjet, and overbite also showed statistically significant changes between T1 and T2. Conclusion: Invisalign aligners with the mandibular advancement feature took approximately 9 months for 1.5 mm of overjet correction. The lower incisor angulation was maintained during class II correction. The minimal skeletal changes are in favor of class II correction.