ラット臼歯の発育過程における神経分布に関する研究
スポンサーリンク
概要
- 論文の詳細を見る
A study was undertaken to look into the general pattern of nerve distribution in the growing molar teeth of rats from birth to 50 days of age, and results obtained were summarized as follows. 1) Directly after birth of the animal, presence of tooth germs of both 1st and 2nd molars could be seen in both upper and lower quadrants of jaw, of which the former was in an early form of the bell stage and the latter appeared far less developed than the former. In the loose connective tissues filling between basal portion and bony sac of the 1st molar tooth germ, there was observed a small bundle of nerve running collaterally with tiny blood vessels. The nerve bundle was consisted of a few nonmedulated nerve fibers, and stopped there without entering into the dental papilla. 2) By 3 days after birth of animal the whole body of the casps of 1st molar germ except occlusal tip was deposited with enamel substance. Many tiny blood vessels were seen entering into the dental papilla. In the tooth germ of 2nd molar, on the other hand, formation of thin layer of enamel substance was seen only along the oblique surface of the casp. At this stage of growth, a single nerve fiber of finest size in company with tiny blood vessels could be seen entering into the lower part of dental papilla, frequency of which being one in five cases. In the 2nd molar tooth germ, one could see small nerve bundles running through its basal dental sac, but they were never seen to enter the dental papilla. 3) By 10 days after birth of animal, there was already seen formation of tooth roots starting in the 1st molar, and appearance of 3rd molar tooth germ of upper jaw in early shape of bell stage. At this time, some of the nerve fibers were seen to ascend through the tooth pulp, branching on the way to become non-medulated, and reaching as far as to odontoblast layer with their terminal branches. In the 2nd molar tooth germ at this stage, number of the nerve fibers to be noticed to enter into the tooth pulp was yet very limited. 4) By 15 days after birth of animal, enamel substance of the 1st molar showed increased calcification and, with accerelated growth of the root, the whole length of tooth became extended. Growth of tooth roots had also begun in the 2nd molar, and in the 3rd molar germ there was now appearance of small blood vessels within the enamel pulp. There could be seen in the 1st molar the nerve fibers reaching at this time as far as to the odontoblast layer near the pulpal horns, whereas in the 2nd molar no such nerve fiber was seen reaching there, and in the tooth germ of 3rd molar not a single nerve could be seen entering the dental papilla. 5) By 20 days after birth of animal, the 1st molar had begun to erupt and the nerve tissue, now enriched in quantity, had formed a nerve plexus beneath the odontoblast layer and sent terminal branches there. These, however, failed yet to reach the young dentine. In the 2nd molar, on the other hand, the nerve fibers, accompanied by tiny blood vessels, were seen to have reached the odontoblast layer, although fewer in number as compared with those found in the 1st molar. Distribution of the nerve tissues into the dental papilla could not yet be observed with the 3rd molar teeth at this time. 6) By 40 days after birth of animal, the 1st molar was completely erupted and the nerve fibers and also those of the 2nd and 3rd molars likewise became more and more increased and complicated in their amount and running although not to the full extent of nerve development to be attained in the final stage of tooth maturity. In the 3rd molar, the nerve fibers were far less-numbered than in the other two and their running was correspondingly simpler. Even at this time the ends of nerve fibers failed to reach the odontoblast layer.
- 九州歯科学会の論文
- 1976-09-30