甲状腺摘出が歯の形成に及ぼす影響に関する研究

Abstract

Possible effects of thyroidectomy on the development of teeth were studied in the rats which were divided into 3 groups according to respectively different experimental conditions. Group A was consisted of those rats which were thyroidectomized 7 days after birth and those which were served as control, both fed with the same pellet food MF as prepared by Oriental Co. for general use. Group B was consisted of those rats which were thyroidectomized 30 days after birth and those for control, both fed with the same food as above. Group C was consisted of those rats which were thyroidectomized 7 days after birth and those for control, both fed with the pellet food NMF as prepared by Oriental Co. for special purpose of promoting growth of animals. Weight gain of normal and thyroidectomized animals was followed up and radiological and patho-histological observations were conducted on incisor and molar teeth of both jaws, and results of these studies were summarized as follows. 1. WEIGHT GAIN Difference in weight gain in both operated and control groups of animal was most marked in the case of early thyroidectomy, and no difference of weight gain was noticed with regard to the difference of animal food given. 2. Radiological Findings a) It was particularly noticed that the incisor teeth of thyroidectomized rats were smaller and more curved than those of control animals, but any such difference was not noticed with respect to difference of time of operation nor of laboratory chow given, not even with difference of male and female of the animal. b) Radiological observation showed that the molar teeth in the thyroidectomized rats had larger pulp cavity and their roots less developed than in the teeth of control animals. Comparison of growth rates among every groups revealed that animals in Group B showed a slightly better growth of molar teeth. 3. Patho-histological Findings a) The most significant findings to be observed in the teeth of thyroidectomized animals were the hypoplasia and hypocalcification of dentine, and both symptoms were more apparent in the incisors than in the molars. b) Underdevelopment and even regressive changes were noticed in the enamel organ of incisors, and these symptoms were more apparent in the lingual than in the labial half of the teeth. There was also observed a slight regressive change in the odontoblasts of incisor and molar teeth. c) In the molar teeth of thyroidectomized animals, there was noticed marked retardation in the development of root, accompanied by poor distribution of cell elements in the cellular cement region of the root apex. d) Hypocalcification of dentine was most conspicuous in the teeth of Group C, followed by Group B and A, and formation of root was more retarded in Group C and A than in Group B. e) Thyroidectomy apparently failed to bring out any significant change on the structure of enamel and its calcification.