Influence of Smile Arc on Esthetic Perception in Relation to Gingival Display: A Cross-Sectional Study on an Iranian Population

Objectives: This study aimed to evaluate and compare the Iranian’s perception of smile arc esthetics and its relationship with gingival display. Materials and Methods: Two sets of digitally-altered images of a female and a male model were presented to orthodontists and laypeople. Sixteen images with four different smile arcs (including reverse, flat, consonant, and exaggerated) in combination with four gingival display values (-4mm, -2mm, 0mm, and +2mm) were displayed in each set, sorted by gingival display. The raters were asked to rank the smile arcs from the most attractive (1) to the least attractive (4) for each amount of gingival display. The Kruskal-Wallis H and Mann-Whitney U tests were employed to statistically analyze the relationship of gingival display with smile arc esthetics. Results: Totally, 200 laypeople and 22 orthodontists participated in this study. Laypeople preferred flat smile arcs, and orthodontists believed that flat and consonant arcs were the most attractive in all gingival display values for female and male smiles. Reverse arc was mostly disliked in lower amounts of gingival display, and excessive arc was mostly disregarded in higher amounts of gingival display. Conclusion: As the preferred smile arcs were flat and consonant types regardless of the amount of gingival display, and reverse and exaggerated arcs were ranked the lowest in lower and upper extremes of gingival display, respectively, it may be concluded that the relationship between the gingival display and smile arc esthetics is more significant when considering unattractiveness.