title: Periodontal microstructure change and tooth movement pattern under different force magnitudes in ovariectomized rats: an in-vivo microcomputed tomography study.
abstract: BACKGROUND
  The purpose of this study was to evaluate the dynamic changes in the periodontal microstructure and the molar displacement pattern during orthodontic tooth movement in ovariectomized rats.
  
  
  METHODS
  Twenty ovariectomized rats received either 100 or 30 g of orthodontic force to induce mesial movement of the maxillary left first molars over 14 days. Ten healthy rats underwent sham operations as controls. Periodontal ligament thickness, alveolar bone microstructural properties, and displacement of the molar were measured with 6 in-vivo microcomputed tomography scans for each sample.
  
  
  RESULTS
  The ovariectomized rats that received 100 g of orthodontic force had obvious changes in periodontal ligament thickness at day 1 and poor periodontal ligament thickness recovery from days 5 through 14. The bone volume fraction increased and the trabecular separation decreased significantly in this group at day 3, and obvious bone loss was observed at day 14. Molar linear and angular movements were also higher in this group than in the other 2 groups.
  
  
  CONCLUSIONS
  Relatively heavier force applications in ovariectomized rats resulted in poor periodontal ligament thickness recovery and local alveolar bone overcompression, and consequently induced undermining resorption and obvious alveolar bone loss; these led to high rates of tooth movement and molar inclination.
authors.affiliation: Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Yiqi
authors.initials: Y
authors.lastname: Xu
authors.forename: Tangmin
authors.initials: T
authors.lastname: Zhao
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Xu
authors.forename: Yin
authors.initials: Y
authors.lastname: Ding
mesh_terms: D016301:Alveolar Bone Loss / Q000473:pathology; D000539:Alveolar Process / Q000648:ultrastructure; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D005260:Female; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008437:Maxilla / Q000473:pathology; D008963:Molar / Q000473:pathology*; D009969:Orthodontic Wires; D010052:Ovariectomy / Q000379:methods*; D010513:Periodontal Ligament / Q000648:ultrastructure; D010519:Periodontium / Q000648:ultrastructure*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation; D014092:Tooth Root / Q000648:ultrastructure; D055114:X-Ray Microtomography / Q000379:methods*