[Effect of dihydrotachysterol on the periodontal tissues in rats].

The purpose of the present study was to investigate the histological changes of the periodontal tissues in rats produced by oral administration of dihydrotachysterol (DHT). Forty-five rats, 6 weeks old, were divided equally into 9 groups (Groups A-I). Groups A, D and G, control groups, received an administration of corn oil (0.5 ml) once a day for 1, 2 and 4 weeks, respectively. Groups B, E and H received an administration of DHT (25 micrograms) once a day for 1, 2 and 4 weeks, respectively. Groups C, F and I had an administration of DHT (50 micrograms) once a day for 1, 2 and 4 weeks, respectively. The animals of all groups were killed 24 hours after the last administration. The periodontal tissues of the maxillary first molar of all animals were examined histologically and histometrically. Histological and histometrical findings: 1. In Groups A, D and G, control groups, the periodontal ligament, alveolar bone and cementum appeared normal during the entire experimental period. 2. In Group B, the peridontal tissues were almost similar to those of the control group. 3. In Groups C and E, osteoid tissue was observed in the alveolar bone surface. The thickness of the periodontal ligament decreased and the bone marrow spaces were slightly enlarged. The volmetric density of the alveolar bone decreased compared with that of the control groups. 4. In Groups F, H and I, the thickness of the periodontal ligament decreased significantly. In the periodontal ligament, destruction of collagen fibers was observed, and fibroblasts, collagen fibers and oxytalan fibers decreased in number. Dental ankylosis was also found. An abnormal darkly-stained layes (using the PAS staining method) was observed in the cementum surface. The alveolar bone marrow spaces were enlarged and replaced by fibrous tissue. In the histometrical findings, the thickness of the periodontal ligament and the volumetric density of the alveolar bone had decreased, and the volume of the cementum had increased significantly. The result of the present study suggested that oral administration of dihydrotachysterol to the rats induced the changes of the periodontal tissues similar to those seen in aging humans.