title: [Maxillary protraction with and without maxillary expansion on unilateral cleft lip and palate model: a finite element analysis].
abstract: OBJECTIVE
  The aim of this finite element study was to investigate biomechanical effects of maxillary protraction with and without maxillary expansion on unilateral cleft lip and palate(UCLP)model before and after alveolar bone graft (ABG).
  
  
  METHODS
  Orthopedic force (30° downward and forward to the occlusal plane, 5N/side) with expansion and without expansion were loaded on models before ABG, and after ABG respectively. Initial displacement and sutural stress were analyzed by using ANSYS12.0 software.
  
  
  RESULTS
  The amount of displacement at the cleft side was larger than that at the non-cleft side before ABG, a more symmetrical pattern was obtained after ABG. Regardless of ABG, maxillary protraction with maxillary expansion exhibited more evident forward displacement of maxilla. The sutural stress values after maxillary protraction with maxillary expansion were significantly higher than without expansion.
  
  
  CONCLUSIONS
  Analysis of these results showed that maxillary protraction with expansion could presumably promote the orthopedic effects of the facemask on UCLP patients, and more uniform force would obtain after ABG.
authors.affiliation: Department of Orthodontics, Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, China. byndia@gmail.com
authors.forename: Zheng-xi
authors.initials: ZX
authors.lastname: Chen
authors.forename: Xiao-gang
authors.initials: XG
authors.lastname: Pan
authors.forename: Zhen-qi
authors.initials: ZQ
authors.lastname: Chen
mesh_terms: D002971:Cleft Lip; D002972:Cleft Palate; D005115:Extraoral Traction Appliances; D020342:Finite Element Analysis; D006801:Humans; D008437:Maxilla; D010155:Palatal Expansion Technique