title: Comparison between landmark and surface-based three-dimensional analyses of facial asymmetry in adults.
abstract: OBJECTIVE
  To collect the reference values for facial asymmetry in adults using landmark and surface-based three-dimensional analyses and to compare their diagnostic abilities.
  
  
  METHODS
  Laser scans were taken from 85 British Caucasians, 29 males (23.9±5.7 years, range 19-44) and 56 females (28.1±9.5 years, range 19-54), students and staff of the Cardiff Dental Hospital, and three orthodontic patients with marked facial asymmetry. An asymmetry index (AI) was measured for 14 landmarks. The surface-to-surface average distance between the best-fit registered original and mirror scans (ADom) was measured for the whole face and six regions. Non-parametric descriptive statistics was used to obtain the reference values, and Mann-Whitney U-test was used for gender comparison. P values less than 0.05 were considered significant. Patients' values were compared to the reference values by calculating the corresponding percentiles.
  
  
  RESULTS
  The lowest AI was found for 'pronasale' in males [median 0.1 (interquartile range 0.0-0.3) mm] and the highest for 'cheilion' [3.5 (2.4-5.0) mm] in females. The ADom for the whole face was 0.7 (0.5-0.9) mm in males and 0.6 (0.5-0.7) mm in females and regionally between 0.4 (0.3-0.6) mm and 0.8 (0.4-1.2) mm. In orthodontic patients, AI did not always reveal asymmetry in a particular coordinate plane, and surface-based analysis was favourable in regions underrepresented by landmarks.
  
  
  CONCLUSIONS
  Facial asymmetry can be accurately quantified using landmark- and surface-based approaches. The latter offers a more comprehensive analysis of the face.
authors.affiliation: Department of Orthodontics, Cardiff University, School of Dentistry, Cardiff, UK dr_al_qattan@hotmail.com.
authors.forename: M
authors.initials: M
authors.lastname: Alqattan
authors.affiliation: Department of Orthodontics, Cardiff University, School of Dentistry, Cardiff, UK.
authors.forename: J
authors.initials: J
authors.lastname: Djordjevic
authors.affiliation: Department of Orthodontics, Cardiff University, School of Dentistry, Cardiff, UK.
authors.forename: A I
authors.initials: AI
authors.lastname: Zhurov
authors.affiliation: Department of Orthodontics, Cardiff University, School of Dentistry, Cardiff, UK.
authors.forename: S
authors.initials: S
authors.lastname: Richmond
mesh_terms: D000328:Adult; D059925:Anatomic Landmarks; D002508:Cephalometry / Q000379:methods; D005145:Face / Q000033:anatomy & histology* / Q000473:pathology; D005146:Facial Asymmetry / Q000175:diagnosis*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007834:Lasers; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D018709:Statistics, Nonparametric; D055815:Young Adult