The Effect of Dental Midline Asymmetry and Diastema on Esthetic Perception Among Undergraduate Dental Students: A Survey Study

Background This study aimed to evaluate dental students' perception of smile aesthetics about varying degrees of dental midline deviation and diastema, and to investigate whether these perceptions differ according to gender, prior dental treatment history, and educational level (preclinical vs. clinical phases). Methods A total of 400 voluntary dental students (268 females, 132 males) from Afyonkarahisar Health Sciences University participated in the study. Using a single facial photograph as a reference, nine digitally altered images were created depicting various combinations of dental midline deviations (0 mm, 1 mm, 2 mm) and diastema widths (0 mm, 1 mm, 2 mm). Participants rated each image based on aesthetic perception via an online survey using a Visual Analog Scale (VAS) ranging from 0 (not aesthetic) to 10 (highly aesthetic). Inter-group differences among VAS scores were analyzed using the Kruskal-Wallis test; pairwise comparisons were performed with the Mann-Whitney U test and Bonferroni correction. Additionally, the effects of gender, educational level (preclinical vs. clinical), and prior treatment history were evaluated using the Mann-Whitney U test. Results Statistically significant aesthetic differences were observed for midline deviations (χ²=184.63; p < 0.001), diastemas (χ²=703.98; p < 0.001), and their combinations (χ²=1017.54; p < 0.001). Increasing the midline deviation from 1 mm to 2 mm and increasing the diastema width from 1 mm to 2 mm significantly reduced aesthetic ratings (p < 0.001). The least aesthetically pleasing scenario was identified as the combination of a 2 mm midline deviation and a 2 mm diastema. Clinical students were more sensitive to the 2 mm midline deviation compared to preclinical students (p < 0.05). Prior dental treatment history significantly influenced aesthetic perception only in the control group (p < 0.05). Gender differences were significant only in conditions involving a 1 mm deviation alone (p = 0.038) and a combination of 2 mm deviation with 1 mm diastema (p = 0.028). Conclusion Even minimal dental alterations, such as a 1 mm midline deviation or a 1 mm diastema, negatively impact smile aesthetics, with combined alterations causing the most significant reduction. Advancing clinical education increases sensitivity to midline deviations, while the influence of gender and treatment history is limited.