| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1987: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1986: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
In recent years, widening of the periodontal space has been thought to be one of the important early radiographic signs of jaw bone injury following irradiation. Alterations of the metabolism in the alveolar bone have been regarded as a cause of such radiographic changes. To disclose the initiation process of this change. the radiation effects to the remodeling of the alveolar bone was examined. An experiment was carried out with Wister rats, in which the mandibular molar region was irradiated with a single dose of Co-60 <gamma>-ray, 20, 40, 60, 80 and 100 Gy in absorbed doses. Irradiated mandibles were excised at 6 hours, 1, 3, 6, 14, 26, 54, 110 and 166 days after irradiation. Animals not irradiated, spending at the same experimental period. were used as a control group. Changes in the periodontal ligament, alveolar bone and thier cellular elements were evaluated histologically and fluorescence-microscopically. Following results were obtained.
1. Newly formed bone area, as indicated by labelling with fluorescence agents, was alsways smaller in the irradiated groups than in the control group, corresponding to the amount of the absorbed dose.
2. Osteoblasts, cementoblasts and fibroblasts in the irradiated periodontium exhibited the pyknotic changes of nuclei and decrease in cell number after 1 to 3 or 26 days following irradiation.
Based on these results, it was suggested that the remodeling of the alveolar bone following irradiation might be disturbed by both quantitative and qualitative changes in the cellular elements comprising the periodontal ligament and alveolar bone.
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