Three-dimensional evaluation of social smile symmetry

Abstract

ABSTRACT Objective: To evaluate the social smile symmetry using three-dimensional (3D) stereophotogrammetric images. Materials and Methods: The study was conducted with 3D facial images of 30 individuals (age range 13–25 years). The rest position was considered as the reference image and the social smile image was aligned on this image using the best-fit alignment method. The spatial differences between the same points established on both images using 3D analyses were determined for right and left points in X, Y, and Z planes. Results: The highest difference related to spatial distance in right and left points was −0.56 mm (95% confidence interval [CI], −1.19, 0.06 mm) between right and left commissure (Com) points. The difference was not significant, and the Bland-Altman upper and lower limits were −3.85 mm and 2.71 mm, respectively. The highest difference for the transversal plane was found in Com points, similarly to the spatial distance (mean: 0.50 mm, 95% CI, −2.62, 1.02 mm). The differences between the changes in the left and right points in the Y and Z plane were not significant (P > .05). Conclusions: The social smile was observed to show asymmetry in varying amounts in the different directions. Asymmetry increases in some cases, specifically for the corners of the mouth.