title: Tooth display and lip position during spontaneous and posed smiling in adults.
abstract: OBJECTIVE
  To analyze differences in tooth display, lip-line height, and smile width between the posed smiling record, traditionally produced for orthodontic diagnosis, and the spontaneous (Duchenne) smile of joy.
  
  
  METHODS
  The faces of 122 male participants were each filmed during spontaneous and posed smiling. Spontaneous smiles were elicited through the participants watching a comical movie. Maxillary and mandibular lip-line heights, tooth display, and smile width were measured using a digital videographic method for smile analysis. Paired sample t-tests were used to compare measurements of posed and spontaneous smiling.
  
  
  RESULTS
  Maxillary lip-line heights during spontaneous smiling were significantly higher than during posed smiling. Compared to spontaneous smiling, tooth display in the (pre)molar area during posed smiling decreased by up to 30%, along with a significant reduction of smile width. During posed smiling, also mandibular lip-line heights changed and the teeth were more covered by the lower lip than during spontaneous smiling.
  
  
  CONCLUSIONS
  Reduced lip-line heights, tooth display, and smile width on a posed smiling record can have implications for the diagnostics of lip-line height, smile arc, buccal corridors, and plane of occlusion. Spontaneous smiling records next to posed smiling records are therefore recommended for diagnostic purposes. Because of the dynamic nature of spontaneous smiling, it is proposed to switch to dynamic video recording of the smile.
authors.affiliation: Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Pieter
authors.initials: P
authors.lastname: Van Der Geld
authors.forename: Paul
authors.initials: P
authors.lastname: Oosterveld
authors.forename: Stefaan J
authors.initials: SJ
authors.lastname: Berge
authors.forename: Anne M
authors.initials: AM
authors.lastname: Kuijpers-Jagtman
mesh_terms: D000328:Adult; D001641:Bicuspid / Q000033:anatomy & histology; D002610:Cheek / Q000033:anatomy & histology; D015331:Cohort Studies; D003481:Cuspid / Q000033:anatomy & histology; D004955:Esthetics, Dental; D006240:Happiness; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D008046:Lip / Q000033:anatomy & histology*; D008297:Male; D008334:Mandible / Q000033:anatomy & histology; D008437:Maxilla / Q000033:anatomy & histology; D008875:Middle Aged; D008963:Molar / Q000033:anatomy & histology; D009811:Odontometry; D023861:Photography, Dental; D012904:Smiling; D014070:Tooth / Q000033:anatomy & histology*