title: Locating the center of resistance of maxillary anterior teeth retracted by Double J Retractor with palatal miniscrews.
abstract: OBJECTIVE
  To locate the center of resistance of six maxillary anterior teeth retracted by the Double J Retractor (DJR) and to find the optimal position of palatal miniscrews.
  
  
  METHODS
  The three-dimensional (3D) finite element model included 12 teeth with two first premolars extracted. The DJR was modeled as a 3D beam element. The miniscrew was sagittally placed between the second premolar and the first molar, and the vertical position of the miniscrew was established at five conditions: 6, 7, 8, 9, and 10 mm apically from the cervical line of the first molar. The length of the retraction lever arm was determined according to the position of the miniscrew, for the direction of retraction force to be parallel to the maxillary occlusal plane. The 3D finite element method was used to determine the location of the center of resistance of the maxillary anterior teeth by visualizing the tooth displacement and stress distribution.
  
  
  RESULTS
  As the miniscrew was located apically, the stress spread out to the root apex and the adjacent alveolar bone. At the 8-mm level of miniscrews, a bodily-like parallel retraction could be obtained with DJR.
  
  
  CONCLUSIONS
  In this study, the center of resistance of the six maxillary anterior teeth retracted by DJR with palatal miniscrews was estimated to be 12.2 mm apically from the incisal edge of the central incisor.
authors.affiliation: Kyung Hee University, Seoul, South Korea.
authors.forename: Hyoung-Jun
authors.initials: HJ
authors.lastname: Jang
authors.forename: Won-Jong
authors.initials: WJ
authors.lastname: Roh
authors.forename: Bo-Hoon
authors.initials: BH
authors.lastname: Joo
authors.forename: Ki-Ho
authors.initials: KH
authors.lastname: Park
authors.forename: Su-Jung
authors.initials: SJ
authors.lastname: Kim
authors.forename: Young-Guk
authors.initials: YG
authors.lastname: Park
mesh_terms: D000328:Adult; D001863:Bone Screws; D003481:Cuspid / Q000502:physiology*; D003799:Dental Stress Analysis / Q000379:methods; D055119:Elastic Modulus; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000502:physiology*; D008437:Maxilla; D008904:Miniaturization; D008954:Models, Biological; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D009967:Orthodontic Appliances; D057887:Overbite / Q000503:physiopathology / Q000628:therapy*; D010513:Periodontal Ligament / Q000502:physiology; D013314:Stress, Mechanical