title: The perception of facial asymmetry using 3-dimensional simulated images.
abstract: OBJECTIVE
  To investigate the perception of facial asymmetry in young adults to identify the amounts of chin asymmetry that can be regarded as normal and may benefit from correction.
  
  
  METHODS
  Three-dimensional (3D) images of 56 individuals of mixed ethnicity were obtained and used to produce average 3D images of male and female faces. Distortion was then applied to these average faces using a 3D graphics package to simulate different amounts of chin point asymmetry. Five observer groups (lay individuals, dental students, dental care professionals, dental practitioners, and orthodontists) assessed timed presentations of 3D images, rating them as "normal," "acceptable," or "would benefit from correction." Time-to-event analysis was used to assess the level of chin asymmetry perceived as normal and beneficial for correction for each group.
  
  
  RESULTS
  The factors influencing the perception of facial asymmetry were the degree of asymmetry and the observer group. Direction of the asymmetry and gender of the assessed individual did not affect the perception of asymmetry, except in the 4- to 6-mm distortion range. The gender of the observer had no influence on perception. There were statistically significant differences in the amounts of asymmetry that the laypeople and orthodontists considered to be normal (5.6 ± 2.7 mm and 3.6 ± 1.5 mm, respectively; P < .001) and felt would benefit from surgical correction (11.8 ± 4.0 mm and 9.7 ± 3.0 mm, respectively; P  =  .001).
  
  
  CONCLUSIONS
  Perception of asymmetry is affected by the amount of asymmetry and the observer group, with orthodontists being more critical.
authors.affiliation: a  Postgraduate Student, School of Dentistry, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Grainne
authors.initials: G
authors.lastname: McAvinchey
authors.forename: Fay
authors.initials: F
authors.lastname: Maxim
authors.forename: Barry
authors.initials: B
authors.lastname: Nix
authors.forename: Jelena
authors.initials: J
authors.lastname: Djordjevic
authors.forename: Rognvald
authors.initials: R
authors.lastname: Linklater
authors.forename: Gabriel
authors.initials: G
authors.lastname: Landini
mesh_terms: D000293:Adolescent; D000328:Adult; D001294:Attitude to Health; D002680:Chin / Q000473:pathology; D003196:Computer Graphics; D003727:Dental Auxiliaries / Q000523:psychology; D003815:Dentists / Q000523:psychology; D005146:Facial Asymmetry / Q000145:classification / Q000523:psychology*; D005260:Female; D005792:General Practice, Dental; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D009970:Orthodontics; D012737:Sex Factors; D013335:Students, Dental / Q000523:psychology; D055815:Young Adult
keywords: Facial asymmetry; Perception; Three-dimensional images