抄録
Thirty rats were used in the experiment. Food Impaction was induced to occur in the interdental space between the upper 1st and 2nd molars in the rat by creating a fossa in the mesial marginal protuberance of the occlusal surface of the 2nd molar by spot grinding. Changes in the periodontal tissues in this region occurred with the elapse of time were histpathologically observed from immediately after to twelve weeks after the operation, with results as follows:
1. In three weeks a gingival pocket had been formed on the side of the 2nd molar; there were a localized inflammatory cell infiltration in the upper part of the lamina propria and a slight enlargement of the periodontal membrane on the 2nd molar.
2. With the elapse of time, the gingival pocket on the 2nd molar gradually increased in depth, the inflammatory cell infiltration in the lamina propria expanded into deep layers, and the periodotal space enlarged. In addition, signs of resorption of the alveolar crest and verical resorption of the alveolar bone along the 2nd molar were observed.
3. In twelve weeks a deep gingival pocket was present on the side of the 2nd molar, the inflammatory cell infiltration in the lamina propria had spread around the pocket apex, and the bundles of fibers of the gingiva showed extremely irregular arrangement and discontinuations.
4. Compared with the above-mentioned changes on the side of the 2nd molar, those on the side of the 1st molar were exceedingly sight throughout the experimental period.
