title: Photoelastic stress analysis of mandibular molars moved distally with the skeletal anchorage system.
abstract: BACKGROUND
  The purpose of this study was to analyze photoelastically the stress distribution around teeth in the simulated distal movement of mandibular molars with the skeletal anchorage system.
  
  
  METHODS
  Two types of the photoelastic mandibular dentition models were used, 1 before and 1 after distal movement of the second molar. The experiment was performed with 3 forms of traction--first-molar single traction, second-molar single traction, and simultaneous first- and second-molar traction. The direction of traction was set parallel to the occlusal plane and at an angle of 30 degrees downward to the occlusal plane.
  
  
  RESULTS
  In the first-molar single traction model, extremely high stress was generated around the first molar with traction parallel to the occlusal plane. With the traction 30 degrees downward to the occlusal plane, all models showed the stress around the molars extended distally and downward.
  
  
  CONCLUSIONS
  Simultaneous traction of the first and second molars might be preferable to the sequential traction of each molar to prevent the unfavorable distal tipping of the first molar. Regardless of whether simultaneous or sequential traction is used, the downward traction to the occlusal plane seems to induce intrusion of the molars as well as their distal movement.
authors.affiliation: Division of Orthodontics, Department of Oral Growth and Development, Fukuoka Dental College, Fukuoka, Japan. atussy@college.fdcnet.ac.jp
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakamura
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Teratani
authors.forename: Hidemi
authors.initials: H
authors.lastname: Itoh
authors.forename: Junji
authors.initials: J
authors.lastname: Sugawara
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ishikawa
mesh_terms: D001718:Birefringence; D003198:Computer Simulation; D003799:Dental Stress Analysis / Q000379:methods*; D004548:Elasticity; D006801:Humans; D021621:Imaging, Three-Dimensional; D008334:Mandible; D003765:Models, Dental; D008963:Molar / Q000502:physiology*; D052280:Orthodontic Anchorage Procedures; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000295:instrumentation*; D014143:Traction