title: Esthetic evaluation of dynamic smiles with attention to facial muscle activity.
abstract: BACKGROUND
  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.
authors.affiliation: Department of Orthodontics and Pediatric Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA.
authors.forename: Angela I-Chun
authors.initials: AI
authors.lastname: Lin
authors.forename: Thomas
authors.initials: T
authors.lastname: Braun
authors.forename: James A
authors.initials: JA
authors.lastname: McNamara
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Gerstner
mesh_terms: D000293:Adolescent; D000328:Adult; D001504:Beauty; D002610:Cheek / Q000502:physiology; D003815:Dentists; D004955:Esthetics, Dental; D005123:Eye; D005152:Facial Muscles / Q000502:physiology*; D005260:Female; D006801:Humans; D008046:Lip / Q000502:physiology; D008297:Male; D009055:Mouth / Q000502:physiology; D009801:Oculomotor Muscles / Q000502:physiology; D012904:Smiling / Q000502:physiology*; D013335:Students, Dental; D014743:Videotape Recording; D055815:Young Adult