title: Three-dimensional analysis of facial shape and symmetry in twins using laser surface scanning.
abstract: OBJECTIVE
  Three-dimensional analysis of facial shape and symmetry in twins.
  
  
  METHODS
  Faces of 37 twin pairs [19 monozygotic (MZ) and 18 dizygotic (DZ)] were laser scanned at the age of 15 during a follow-up of the Avon Longitudinal Study of Parents and Children (ALSPAC), South West of England.
  
  
  METHODS
  Facial shape was analysed using two methods: 1) Procrustes analysis of landmark configurations (63 x, y and z coordinates of 21 facial landmarks) and 2) three-dimensional comparisons of facial surfaces within each twin pair. Monozygotic and DZ twins were compared using ellipsoids representing 95% of the variation in landmark configurations and surface-based average faces. Facial symmetry was analysed by superimposing the original and mirror facial images.
  
  
  RESULTS
  Both analyses showed greater similarity of facial shape in MZ twins, with lower third being the least similar. Procrustes analysis did not reveal any significant difference in facial landmark configurations of MZ and DZ twins. The average faces of MZ and DZ males were coincident in the forehead, supraorbital and infraorbital ridges, the bridge of the nose and lower lip. In MZ and DZ females, the eyes, supraorbital and infraorbital ridges, philtrum and lower part of the cheeks were coincident. Zygosity did not seem to influence the amount of facial symmetry. Lower facial third was the most asymmetrical.
  
  
  CONCLUSIONS
  Three-dimensional analyses revealed differences in facial shapes of MZ and DZ twins. The relative contribution of genetic and environmental factors is different for the upper, middle and lower facial thirds.
authors: Department of Applied Clinical Research and Public Health, Cardiff University Dental Hospital, Cardiff, Wales, UK. alexmjz@ptt.rs
authors: J
authors: J
authors: Djordjevic
authors: M
authors: M
authors: Jadallah
authors: A I
authors: AI
authors: Zhurov
authors: A M
authors: AM
authors: Toma
authors: S
authors: S
authors: Richmond
mesh_terms: D000293:Adolescent; D059925:Anatomic Landmarks / Q000033:anatomy & histology; D002508:Cephalometry / Q000379:methods / Q000706:statistics & numerical data; D002680:Chin / Q000033:anatomy & histology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004777:Environment; D005143:Eyelids / Q000033:anatomy & histology; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D005500:Follow-Up Studies; D005546:Forehead / Q000033:anatomy & histology; D059647:Gene-Environment Interaction; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods / Q000706:statistics & numerical data; D021621:Imaging, Three-Dimensional / Q000379:methods* / Q000706:statistics & numerical data; D007834:Lasers; D008046:Lip / Q000033:anatomy & histology; D008137:Longitudinal Studies; D008297:Male; D009666:Nose / Q000033:anatomy & histology; D014427:Twins / Q000235:genetics; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics
keywords: 3D imaging; ALSPAC; face; shape analysis; surface laser scanning; symmetry; twins