title: Evaluation of the changes in midfacial configuration after face mask therapy in skeletal Class III growing patients by morphometric analysis techniques.
abstract: OBJECTIVE
  The prevalence of Angle Class III malocclusion is relatively high in Taiwan. For children who suffer from maxillary retrognathia, face mask therapy is a promising treatment modality. The purpose of this study was to evaluate the changes in midfacial configuration after face mask therapy in skeletal Class III growing patients by morphometric analysis techniques.
  
  
  METHODS
  Thirty children who had been treated with face masks were compared with a group of 30 gender-matched, age-matched, observation period-matched, and craniofacial configuration-matched subjects with untreated Class III malocclusions. Average geometries, scaled to an equivalent size, were generated by means of Procrustes analysis. Graphical analysis, utilizing thin-plate spline analysis and strain tensor methods, was performed for localization of differences in shape and size changes. Maximum and minimum principal extensions were drawn to express the directions of shape change.
  
  
  RESULTS
  Maxillary protraction-induced changes resulted from a combination of both orthopedic and dental effects. A significant increase in size (7.7% to 9.9%) was noted at the supero-anterior region of the midfacial configuration (rhinion-orbitale-midpalatal point-anterior nasal spine) when subjected to an extraoral traction force; 7.7% to 12.1% of increase in size and 14.4% to 33.4% of change in shape were found at the anterior portion of the maxillary alveolar bone. The directions and amount of principal strain tensors could express the magnitudes and directions of morphological changes within the midfacial complex in an efficient way.
  
  
  CONCLUSIONS
  We conclude that morphometric analysis techniques can be used to evaluate the changes in midfacial configuration after face mask therapy and can provide a valuable supplement for conventional cephalometric analysis.
authors.affiliation: School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Jenny Zwei-Chieng
authors.initials: JZ
authors.lastname: Chang
authors.forename: Hong-Po
authors.initials: HP
authors.lastname: Chang
authors.forename: Yi-Jane
authors.initials: YJ
authors.lastname: Chen
authors.forename: Jane Chung-Chen
authors.initials: JC
authors.lastname: Yao
authors.forename: Pao-Hsin
authors.initials: PH
authors.lastname: Liu
authors.forename: Frank Hsin-Fu
authors.initials: FH
authors.lastname: Chang
mesh_terms: D016022:Case-Control Studies; D002508:Cephalometry; D002648:Child; D002675:Child, Preschool; D005115:Extraoral Traction Appliances; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D008313:Malocclusion, Angle Class III / Q000453:epidemiology / Q000628:therapy*; D008445:Maxillofacial Development; D010155:Palatal Expansion Technique; D013624:Taiwan / Q000453:epidemiology; D016896:Treatment Outcome