title: [Three-dimensional finite element analysis of craniofacial skeleton protraction at medium position].
abstract: OBJECTIVE
  The purpose of this study was to investigate the biomechanical changes of midface skeleton protraction at its medium position in the craniofacial complex, using the three-dimensional finite element method (FEM).
  
  
  METHODS
  A three-dimensional FEM model was developed from the CT scan images by the technologies of three-dimensional reconstruction, image processing and meshing. The protraction forces were applied to the following locations: the first molar, full maxillary arch, and the floor of aperture piriforms. Biomechanical changes from different position protraction were investigated by means of finite element analyses.
  
  
  RESULTS
  Protraction forces at the level of the floor of aperture piriforms produced a more forward movement of the upper maxilla in sagittal direction. Vertical and lateral displacements were less than those in loading with teeth or denture. Compressive stress on the radix nasi decreased obviously in midface skeleton protraction at its medium position.
  
  
  CONCLUSIONS
  Compared with traditional orthopedic protraction, midface skeleton protraction at its medium position could advance maxilla en bloc, decrease the counterclockwise rotation of the maxilla, and reduce the constriction of the anterior part of the palate.
authors.affiliation: Department of Orthognathic Surgery, Tianjin Stomatological Hospital, Tianjin 300041, China.
authors.forename: Min
authors.initials: M
authors.lastname: Hou
authors.forename: Chun-ming
authors.initials: CM
authors.lastname: Liu
authors.forename: Hai-zhong
authors.initials: HZ
authors.lastname: Zhang
authors.forename: Li-min
authors.initials: LM
authors.lastname: Liang
authors.forename: Quan-wen
authors.initials: QW
authors.lastname: Gao
mesh_terms: D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008437:Maxilla / Q000601:surgery; D012886:Skull / Q000601:surgery*; D013314:Stress, Mechanical