ラット臼歯部上皮遺残の加令的変化に関する研究
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Using rats of multifarious age stages from one day after birth to the extremity of 1083 days of age, study was undertaken on the epithelial remnants at the molar region of animal with special reference to their morphological changes with age, quantitative distribution changes with age and difference in their regional distribution density as shown in the circumference of tooth root. Results were summarized as follows. 1) It was observed with the epithelial remnants of rat's molar region that, besides being produced as remnants of Hertwig's epithelial sheath, they were also consisted of those remnants of the dental lamina and epithelial cells of the enamel organ which were either proliferated or transformed into squamous cells. 2) The epithelial remnants assumed multifarious shapes corresponding to the progressive age stages of animal, and these shapes allowed to be classified into 6 types : primitive, fused, proliferative, retrogressive, calcified and specific. 3) Some of the epithelial remnants became lost in sight by suffering a variety of retrogressive degeneration and others turned into many-sized calcified particles through the mineralization process. 4) The epithelial remnants which originated from Hertwig's epithelial sheath made their first appearance by 19 days after birth of animal and increased the amount thereafter, attaining the maximum size during the period from 60 to 80 days of age. After this period, however, the epithelial remnants became reduced in size and were almost invisible after 301 days of age, except in certain particular cases. 5) There were observed two different modes for the formation of calcified particles, and some particles were formed by direct calcification of the epithelial remnants, while others turned into particles by way of making use of calcified fragments of tissue and cells as their own nuclei. 6) These calcified particles increased gradually with advancing age of animal after 121 days of age. 7) The amount of the epithelial remnants distributed in various regions of tooth root was as follows : 41% at the inside of bifurcation, 19% at cervical region, 17% on inner surface of bifurcated root, 13% on outer surface of bifurcated root, and 10% at the tip of root. Distribution in amount of caleified particles, on the other hand, was as follows : 29% on outer surface of bifurcated root, 28% at apical region, 18% on inner surface of bifurcated root, 14% at the inside of bifurcation, and 11% at cervical region. This apparent discrepancy in distribution patterns between the epithelial remnants and calcified particles strongly suggested the possibility that a considerable portion of the epithelial remnants once produced might have been dissolved and lost through retrogressive degeneration in one hand, while the calcified particles, on the other hand, might have been produced not only from the single source of epithelial remnants but also from the abundant source of tissues and cells in the periodontal membrane suffering calcification with progressive age of animal.
- 九州歯科学会の論文
- 1977-01-31
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