Effect of maxillary incisors, lower lip, and gingival display relationship on smile attractiveness

Abstract

Introduction: This study aimed to evaluate the effect of the relationship between maxillary incisors and lower lip in conjunction with the maxillary gingival display on perception of smile attractiveness. Methods: The frontal intraoral photograph of ideally aligned teeth was modified using image processing software. Twenty different smiles were obtained with a combination of 10 different maxillary incisor edge-lower lip distances and 10 different maxillary gingival display amounts. Attractiveness of these 20 smiles was evaluated by orthodontists (n = 101), dentists (n = 107), and laypersons (n = 105). Two-way ANOVA was used to compare alterations on smile esthetics, and repeated measures ANOVA was used to evaluate the interaction between the variables. Bonferroni-adjusted pairwise comparisons were applied for determining the differences between the rater groups. Results: Maxillary incisor edge-lower lip distance (P < 0.01), maxillary gingival display amount (P < 0.001), and rater group (P < 0.01) had statistically significant influences on perception of smile attractiveness. Orthodontists prefer to see a minimal amount of mandibular incisor exposure and almost full crowns of maxillary central incisors. Dentists and laypersons are more tolerant of mandibular incisor exposure and maxillary central incisor coverage by the upper lip. None of the rater groups preferred the coverage of maxillary incisor edges or maxillary gingival display. Conclusions: Elimination of maxillary gingival display helps to improve smile attractiveness, whereas the coverage of maxillary incisor edges has a negative influence.