title: [Comparison between one-step and two-step space closing methods of sliding mechanics using three-dimensional finite element].
abstract: To construct a three-dimensional finite element model comparing between one-step and two-step methods in torque control of anterior teeth during space closure.
  
  
  METHODS
  Dicom image data including maxilla and upper teeth were obtained though cone-beam CT. A three-dimensional model was set up and the maxilla, upper teeth and periodontium were separated using Mimics software. The models were instantiated using Pro/Engineer software, and Abaqus finite element analysis software was used to simulate the sliding mechanics by loading 1.47 Nforce on traction hooks with different heights (2, 4, 6, 8, 10, 12 and 14 mm, respectively) in order to compare the initial displacement between six maxillary anterior teeth (one-step method) and four maxillary anterior teeth (two-step method).
  
  
  RESULTS
  When moving anterior teeth bodily, initial displacements of central incisors in two-step method and in one-step method were 29.26 × 10⁻⁶ mm and 15.75 × 10⁻⁶ mm, respectively. The initial displacements of lateral incisors in two-step method and in one-step method were 46.76 × 10(-6) mm and 23.18 × 10(-6) mm, respectively. Under the same amount of light force, the initial displacement of anterior teeth in two-step method was doubled compared with that in one-step method. The root and crown of the canine couldn't obtain the same amount of displacement in one-step method.
  
  
  CONCLUSIONS
  Two-step method could produce more initial displacement than one-step method. Therefore, two-step method was easier to achieve torque control of the anterior teeth during space closure.
authors.affiliation: Department of Orthodontics, School of Stomatology Lanzhou University, Lanzhou 730030, China.
authors.forename: Yaohui
authors.initials: Y
authors.lastname: Han
authors.forename: Lan
authors.initials: L
authors.lastname: Mou
authors.forename: Gengchi
authors.initials: G
authors.lastname: Xu
authors.forename: Yiqiang
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Email: gezhl@lzu.edu.cn.
authors.forename: Zhenlin
authors.initials: Z
authors.lastname: Ge
mesh_terms: D054893:Cone-Beam Computed Tomography; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor; D008437:Maxilla / Q000000981:diagnostic imaging; D010519:Periodontium / Q000000981:diagnostic imaging; D012984:Software; D019228:Tooth Crown / Q000000981:diagnostic imaging; D014087:Tooth Movement Techniques / Q000379:methods*; D014092:Tooth Root / Q000000981:diagnostic imaging; D019415:Torque