Semester

Spring

Date of Graduation

2026

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Peter Ngan

Committee Member

Khaled Alsharif

Committee Member

Guoqiang Guan

Abstract

Background and Objectives: Comprehensive orthodontic treatment aims to achieve optimal facial esthetics, which is guided by established norms that have shown variability across different ethnic and gender groups. There is a paucity of literature comparing the esthetic preferences of Chinese and Caucasian orthodontic professionals regarding smiling esthetics. The purpose of this study was to determine the perceived smiling attractiveness ratings between Chinese and Caucasian orthodontic professionals. Methods: One Chinese and one Caucasian lateral smiling photograph generated by artificial intelligence (AI) were used in this study. The maxillary central incisor position was digitally manipulated to simulate variations in anteroposterior (AP) position (2 mm, on Glabella Vertical (GV), +2 mm, and +4 mm) relative to GV and inclinations (0 degrees, 7 degrees, and 14 degrees). A survey was administered to a panel of 59 Chinese (n=35) and Caucasians (n=24) orthodontic professionals to obtain their ratings on the 24 resulting images using a Visual Analogue Scale (0-100). Data were analyzed using an independent sample t-test and a Generalized Linear Model (GLM) for repeated measures ANOVA. Results: No significant differences were found between the rating scores of Chinese and Caucasian professionals on the 24 images (p>0.55).  The ratings by the professionals on the Chinese images were significantly different from the Caucasian images (66.7 + 22.2 vs. 59.5 + 23.5, p< .0001)) with both the Chinese and Caucasian professionals rated the Chinese images as more attractive than the Caucasian images (p< 0.001). The most esthetically pleasing images of were similar for both the Chinese and Caucasian images (Image #2 79.2 vs 82.4, Image #4 73.8 vs 76.2, and Image #5 79.1 vs 78.1) when the AP position of the incisors was on or -2 mm to the GV, and the incisor inclination was 0 to +7 degrees lingual inclination. Conclusion: The ethnicity of the raters did not have a significant effect on rating of smiling esthetics between Chinese and Caucasian images. Both groups consistently and significantly rated the Chinese images as more attractive, suggesting that the unaltered baseline features of the Chinese were perceived as inherently more harmonious. Among the 24 images, both Chinese and Caucasian raters found that the smiling images were most attractive when the AP position of the incisors were on or -2mm to the GV and the incisor inclination was 0 to +7 degrees lingual inclination.

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