Purpose: Dynamic asymmetry has not been as rigorously evaluated as static asymmetry for patients with skeletal deformity but could well be even more important. The aim of the present study was to evaluate the dynamic facial movement of Class III patients with facial asymmetry using a 3-dimensional (3D) motion capture system.
Materials and methods: The present cross-sectional study recruited patients with skeletal Class III malocclusion with and without facial asymmetry. A 3D facial motion capture system was used to record the expression process of a maximal smile. Eleven orofacial landmarks were selected to analyze and calculate the cumulative distance and average speed of each landmark during smiling. The predictor variable was mandibular symmetry. The outcome variables consisted of the measurements of each soft tissue landmark and the absolute differences for the paired landmarks between 2 sides. Other variables consisted of descriptive data, including the age and gender of each patient. The data were analyzed using independent t tests and paired t tests. Bonferroni's adjustment was used to control for multiple comparisons.
Results: A total of 63 patients were divided into 2 groups, an asymmetric group (n = 46) and a control group (n = 17), according to the degree of skeletal deviation. The difference in the cumulative distance of the bilateral cheilions was statistically significant between the 2 groups (P = .002). The difference for the asymmetric and control groups was 2.06 ± 1.78 mm and 1.00 ± 0.79 mm, respectively. In the asymmetric group, a comparison of the deviated side with the nondeviated side revealed statistically significant differences in the magnitude of motion for the cheilion (P < .01) and midlateral lower lip (P < .01).
Conclusions: The patients with skeletal asymmetry also showed asymmetry in soft tissue functions while smiling. The magnitude of movement in the nondeviated side was greater than that in the deviated side.
Copyright © 2019. Published by Elsevier Inc.