| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1990: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
Age-related changes of the tooth and the periodontal tissues were studied morphologically using inbred mouse named senescence accelerated mouse (SAM). In our laboratory, two SAM-sublines ; R/1 (resistant/1) and P/2 (prone/2) were maintained. The incidence of incisor abnormality such as loss of enamel color, hypoplasia of enamel, and fracture was significantly higher in P/2 than in R/1. The onset of OK abnormality was earlier in P/2 and the severity of that was also higher in P/2.
Neither SAM strain manifested a chronic periodontitis similar to that in humans, and no obvious plaque and calculus were observed under a conventional environment and eating standard pellets. However, in both strains, 15% of M3 was lost after 13 months of age, and alveolar bone loss gradually increased with advancing age. Though there was no significant difference in the incidence of M3 loss between the two strains, P/2 showed a higher alveolar bone loss around all molars than did R/1 after one month of age thr
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oughout their life span. It was probably caused by the difference in degree of molar eruption. Other factors, such as occlusal trauma and gingivitis, may play some role in alveolar bone loss.
Statistical analyses of the gingival tissues in these region showed that the following phenomena occurred with age in both strains. The length of the junctional epithelium increased, the depth of the gingival sulcus did not change, and the height of the gingival crest decreased. Therefore, long junctional epithelium was developed and gingival recession occurred, as the periodontal pocket did not develop with age in either strain.
Oral senile amyloidosis in SAM was examined for various ages. The amyloid deposition, was observed only in P/2. In P/2, no amyloid deposition was found at age 6 months ; however, frequency and extent of such deposits increased with advancing age. The gingiva was also affected by the amyloid deposition being positive with anti-AS SAM serum being raised against a unique amyloid protein AS SAM which probably induced "senile systemic amyloidosis". Less
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