title: A new three-dimensional method of assessing facial volumetric changes after orthognathic treatment.
abstract: OBJECTIVE
  To validate a new method of facial volumetric assessment that is dependent on the use of stereophotogrammetric models and a software-based Facial Analysis Tool.
  
  
  METHODS
  The method was validated in vitro with three-dimensional (3D) models of a lifelike plastic female dummy head and in vivo with a male-subject head.
  
  
  METHODS
  Thirty facial silicone explants were added in the nasal and perioral regions of each head, and their volumes were obtained by three different algorithms. These were compared with the actual values obtained by a "water displacement" method.
  
  
  RESULTS
  The least mean error was found with the "tetrahedron formation" method followed by the "projection" method and the "back-plane construction" method. The error with the tetrahedron formation method was 0.071 cm(3) (95% confidence interval [CI]: -0.074 to 0.2161 cm3) with the in vitro models and 0.314 cm3 (95% CI: -0.080 to 0.708 cm3) with the in vivo models. The increased volumetric assessment error observed in vivo was attributed to the registration procedure and possible changes in facial expression.
  
  
  CONCLUSIONS
  These results encourage the use of this method in the 3D assessment of orthognathic surgical outcome, provided a standardized facial expression is used for image acquisition.
authors.affiliation: University of Al-Baath Dental School, Syria.
authors.forename: Mohammad Y
authors.initials: MY
authors.lastname: Hajeer
authors.forename: Zhili
authors.initials: Z
authors.lastname: Mao
authors.forename: Declan T
authors.initials: DT
authors.lastname: Millett
authors.forename: Ashraf F
authors.initials: AF
authors.lastname: Ayoub
authors.forename: Jan Paul
authors.initials: JP
authors.lastname: Siebert
mesh_terms: D000465:Algorithms; D002508:Cephalometry / Q000379:methods; D005145:Face / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008953:Models, Anatomic; D019647:Oral Surgical Procedures; D017063:Outcome Assessment, Health Care / Q000379:methods*; D019047:Phantoms, Imaging; D010780:Photogrammetry