Journal Article

Time-lapse observation of rat periodontal ligament during function and tooth movement, using microcomputed tomography

Yoshiki Nakamura, Koji Noda, Shinji Shimoda, Takashi Oikawa, Chihiro Arai, Yoshiaki Nomura and Kenzo Kawasaki

in The European Journal of Orthodontics

Published on behalf of European Orthodontics Society

Volume 30, issue 3, pages 320-326
Published in print June 2008 | ISSN: 0141-5387
Published online March 2008 | e-ISSN: 1460-2210 | DOI: http://dx.doi.org/10.1093/ejo/cjm133
Time-lapse observation of rat periodontal ligament during function and tooth movement, using microcomputed tomography

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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.

Journal Article.  3164 words.  Illustrated.

Subjects: Restorative Dentistry and Orthodontics

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