Influence of maxillary canine gingival margin asymmetries on the perception of smile esthetics among orthodontists and laypersons

Introduction: Our objective was to determine the perception of smile esthetics among orthodontists and laypeople with respect to asymmetries in the maxillary canines' gingival margins in full-face and close-up smile analyses. Methods: Full-face and close-up photographs of the frontal smiles of 4 subjects (2 women, 2 men) were used. The images were digitally altered to create a symmetrical image with the gingival margin levels of the maxillary canines matching the central incisors. From this new image, 5 stages of alterations were made in the gingival margin of the right canine in 0.5-mm increments. Final full-face and close-up images of the smiles were assessed by 50 orthodontists and 50 laypeople, who indicated the level of attractiveness of each smile on visual analog scales. The data collected were statistically analyzed by means of 1-way analysis of variance with the Tukey post-hoc test and the unpaired Student t test. Results: In general, the most attractive smiles for the orthodontists were those without asymmetries and the one with a 0.5-mm asymmetry, whereas laypersons could not detect an asymmetry up to 1.5 mm (P < 0.05). For both groups of raters, the lowest scores were assigned for the smiles with asymmetries of 2.0 and 2.5 mm (P < 0.05). When opinions of orthodontists and laypersons were compared, in most situations a statistically significant difference was found, with orthodontists more sensitive in detecting deviations (P < 0.001). Moreover, there was no significant difference (P > 0.05) between the full-face and close-up assessments of the smiles. Conclusions: It can be concluded that the perceptions of unilateral asymmetries in the gingival margin levels of the maxillary canines were 1.0 mm for orthodontists and 1.5 to 2.0 mm for laypersons.