Experimental Model of Occlusal Trauma in Mouse Periodontal Tissues

The aim of this study was to establish a model, which can be used to investigate the response of periodontal tissues to excessive occlusal loading in mice by observing histopathological changes. The experiment was performed on ten 7-week-old ddY male mice. Under general anesthesia by intraperitoneal injection pentobarbital sodium, a micro-plus-screwpin (head part, 1.7mm in diameter, thickness 0.5mm thickness) was screwed into the pulp cavity of the upper-left-first molar. R_mCT images of the experimental site indicated the occlusal contact position between the upper- and lower-left-first molars during the experimental periods. A micro-plus-screwpin was maintained at a constant position on the occlusal surface throughout the experimental period. Histopathological changes of the periodontal ligament at the furcation lesion of the lower-left-first molar and its surrounding periodontal tissues were observed under a light microscope. The densities of deeply dyeing cells in hematoxylin staining with a round-shaped nucleus were increased in the periodontal ligament, with a peak effect of day 4. Multinucleated giant cells appeared in the central lesion of the periodontal ligament on day 7. The distribution of resorption on the surface of both of the cementum and the alveolar bone was accompanied by multinucleated giant cells, which expanded rapidly from day 7 to day 14. These results showed that histopathological changes of periodontal tissues to excessive occlusal load were observed at the furcation area of molar teeth. The present method confirmed the effectiveness of the experimental model to examine the occlusal trauma on periodontal tissues produced by excessive occlusal load.