title: Initial orthodontic tooth movement of a multirooted tooth: a 3D study of a rat molar.
abstract: OBJECTIVE
  To elucidate the 3D interactions in the tooth-PDL-bone complex immediately after application of orthodontic forces and their implications on tooth movement and function.
  
  
  METHODS
  A special visualization method using microCT allows us to directly image in 3D the movements of a multirooted molar tooth inside the alveolar bone as well as the collagenous network of the PDL. Using fresh, unstained rat mandibular 1st molar under mesial loads of 0.5-1 N, we address basic concepts in orthodontics during the initial stages of orthodontic movement.
  
  
  RESULTS
  We show that immediately after the application of orthodontic load, direct distinct contacts between the tooth and the bone form in the furcation area. These contacts limit tooth movement and interfere with whole body translation. Only localized sites of highly compressed PDL between the root surfaces and the bone were observed. In general, the collagenous network of the PDL appeared loose and not densely packed in the compressed side. On the tension side, the fibers maintained their overall orientation without any significant extension of the fibers.
  
  
  CONCLUSIONS
  Localized direct contact areas between the tooth roots and the bone at the furcation already form within a few minutes of orthodontic tooth movement. This direct and localized bone involvement guides the movement trajectory and provides a mechanism for the miscorrelation found between force levels and tooth movement during the initial stages of an orthodontic tooth movement.
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: G R S
authors.initials: GR
authors.lastname: Naveh
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
authors.forename: S
authors.initials: S
authors.lastname: Weiner
mesh_terms: D000539:Alveolar Process / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D000818:Animals; D001696:Biomechanical Phenomena; D003094:Collagen; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008963:Molar / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D010513:Periodontal Ligament / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D051381:Rats; D017208:Rats, Wistar; D012399:Rotation; D013314:Stress, Mechanical; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D014087:Tooth Movement Techniques / Q000379:methods*; D014092:Tooth Root / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D003094:Collagen
keywords: PDL; initial orthodontic movement; microCT; molar; multirooted tooth movement