幼若犬永久歯歯胚および周囲組織に対する Betatron 電子線限局照射の影響に関する実験的研究

Abstract

As a means of radiation treatment in the field of oral surgery, high energy electronic therapy employing Betatron and Linac has recently been taken. In the present study, the changes given to the permanent tooth germ and its surrounding tissues of the young dog when Betatron electronic rays was radiated partially and limitedly were investigated roentogenologically and histopathologically. Fifty-eight young dog of about three months old were used as a experimental animals. A dose of 4 MeV, Betatron electronic rays, 600 rad and 1200 rad were applied to the 3rd primary molar and the 4 th permanent premolar germ, respectively in the right mandible. The results obtained were as follows : 1. In the irradiated groups of 600 and 1200 rad, the disturbance of enamel formation were observed on and after the 21st day after the irradiation. 2. Since the 21st day after the irradiation, pulp cells around the cervical end of dentin formation appeared to arrange radially and meet at right angle with collagenous fibers being developed within immature pulp tissue. 3. In the 1200 rad does group, a destruction of the Hertwig's epithelial sheath was observed on the 14st day after the irradiation and on the 30th day, the sheath disappearred. About that time, osteoblast-like cells different from odontoblast occurred in the situation, and an osteodentin began to from already. 4. In the 600 rad dose group, although troubles in dentin and pulp tissues were little observed, enamel hypoplasia was noticed only. These observation might suggested that the radiosensitivity of the ameloblasts derived from the ectoderm was higher than the other. 5. In the 1200 rad dose group, enamel hypoplasia, osteodentin formation, reticular atrophy of pulp and shortening of tooth root were found. These findings was not so vary from the results of predecessors conducted over 1000 R experiments. 6. Both in the 600 and 1200 rad dose group, the growth of the permanent tooth showed remarkably delay and severe crowding within the mandible was observed. 7. In the primary tooth, slight radio-active troubles, such as pulp congestion and the decrease in the number of pulp cells were observed. 8. In the 600 rad dose group, the mandible was not affected at all, but in the 1200 rad one their showed congestion of bone marrow and fibrous degeneration of bone tissue and so on.