Esthetic evaluation of dynamic smiles with attention to facial muscle activity

Abstract

Introduction: Numerous studies of smile esthetics have used still photos. Photos, however, do not capture the dynamics of a smile, an element that can contribute to overall smile esthetics. In this study, we assessed the esthetics of dynamic smiles.

Methods: Four facially balanced female dental students were trained to produce 8 distinct smiles using the facial action coding system. Videos of the models' whole faces were presented to 2 panels of raters: dental students and nondental undergraduate students. Smile attractiveness was rated using a Web-based survey.

Results: The smile that used 4 labial muscles was rated significantly better than the smile involving only the risorius muscle (P <0.05). The orbicularis oculi improved smile attractiveness (P <0.04), especially among smiles rated less favorably (P <0.05). Visibility of the models' eyes, however, did not influence the ratings (P >0.05), perhaps because orbicularis oculi activation altered activations in other muscles in such a way that smile attractiveness was increased in the lower face.

Conclusions: Smile esthetics increased with increased recruitment of muscles involved in smile production. The results were robust across the models, suggesting that objective rating methods of smile-dynamic esthetics could become an important clinical tool.