title: Time-lapse observation of rat periodontal ligament during function and tooth movement, using microcomputed tomography.
abstract: The aim of this study was to observe the time-lapse changes in the rat periodontal ligament (PDL) during function and tooth movement. Under Nembutal anaesthesia, time-lapse changes in the thickness of the PDL of the first molars were investigated in five 12-week-old adolescent rats with microcomputed tomography. Three-dimensional (3D) images were reconstructed from the data. Histological observation was also performed, using undecalcified frozen sections of the maxillary first molar area. The PDL appeared as a radiolucent furrow on the 3D images. A slight change in the thickness of the PDL was observed 1 hour after initiation of orthodontic force loading, which became significant after 6 hours, with the appearance of pressure-tension zones during the tooth movement. These changes were more significant 3 days after orthodontic loading. Histological observation of the lingual cervical PDL (pressure zone) in nine 12- to 13-week-old rats demonstrated that the periodontal space had become narrow and the cellular elements appeared to be densely packed in the narrowed PDL 6 hours after orthodontic loading. Degeneration of tissues appeared 3 days after loading. Observation of the buccal cervical PDL (tension zone) demonstrated that the PDL was extended 6 hours after orthodontic force loading, and the extension continued for up to 3 days. Alkaline phosphatase activity was distributed in the PDL, except for the degenerating tissues in the pressure zone 3 days after loading. The results suggest that the periodontal reaction was initiated within 6 hours after orthodontic force loading, which was related to the structural changes of the PDL. The changes probably induced an early response in individual cells of the PDL.
authors: Department of Orthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan. nakamura-ys@tsurumi-u.ac.jp
authors: Yoshiki
authors: Y
authors: Nakamura
authors: Koji
authors: K
authors: Noda
authors: Shinji
authors: S
authors: Shimoda
authors: Takashi
authors: T
authors: Oikawa
authors: Chihiro
authors: C
authors: Arai
authors: Yoshiaki
authors: Y
authors: Nomura
authors: Kenzo
authors: K
authors: Kawasaki
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D021621:Imaging, Three-Dimensional; D007180:Incisor / Q000000981:diagnostic imaging / Q000502:physiology*; D008137:Longitudinal Studies; D008437:Maxilla; D023421:Models, Animal; D017289:Orthodontic Appliances, Functional; D010513:Periodontal Ligament / Q000000981:diagnostic imaging / Q000502:physiology*; D051381:Rats; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000662:veterinary; D014087:Tooth Movement Techniques / Q000662:veterinary