Influence of upper lip curvature on smile attractiveness in patients with different degrees of gingival smiles: A cross-sectional study with opinions from oral health providers and laypersons

Introduction: Although there is relative consensus about approaches to gingival smile management, there are still discrepancies as to whether a gingival smile is attractive or not. The purpose of this study was to quantify the influence of upper lip curvature shape and the amount of gingival display on the perception of smile attractiveness assessed by Peruvian orthodontists, dentists, and laypersons. Methods: A frontal photograph was digitally altered to generate 3 types of upper lip curvature shapes (upward, straight, and downward) with 5 different levels of gingival smile exposure (0 mm, 2 mm, 3 mm, 4 mm, and 5 mm). Fifteen images were generated. Three groups of evaluators (50 dentists, 50 orthodontists, and 50 laypersons) assessed the images using a visual analog scale. One-way analysis of variance with Bonferroni post-hoc tests and multiple linear regressions were applied. Results: The downward lip curvature shape had a negative effect on the esthetic evaluation of the smile with gingival exposures of 3 mm or more for all the evaluating groups (approximately 20-30 points less than upward or straight smile curvature shapes, P <0.05). Laypeople gave higher scores of almost 10 points more than dentists and orthodontists when evaluating the upward lip curvature shape with 5 mm of gingival exposure during smile (P = 0.029). Conclusions: We found that upward or straight upper lip curvature shapes have a positive impact on perceived smile esthetics. In contrast, downward upper lip curvature shapes have a negative effect on perception when evaluating different degrees of gingival smiles.