イヌの歯の窩洞形成・充填に伴う神経の微細構造変化
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概要
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This study was designed to elucidate the ultrastructural changes of three types of nerve fibers or endings seen in the odontoblast layer and in the predentin of dog canine teeth after 4 dental procedures. Eighty five canine teeth were obtained from 23 adult dogs. Class V cavities of constant size (4 mm×5 mm×2 mm) on the dentin of 80 teeth were prepared with diamond points under cooling condition, but the remaining 5 teeth were used as controls without any cavity preparation. The cavities were filled with Dycal, Hi-Atomic, Unident and Adaptic, respectively. These teeth were extracted at 5,10,20,30 and 60 days after dental treatment. The apical fourth of the roots of the experimental and control teeth was immediately cut off after extraction and was fixed with 4% glutaraldehyde for 12 h. Thereafter, the teeth were split longitudinally in two halves and their intradental tissues excised carefully were again fixed with the same fixative. The remaining dental tissues excised carefully from the other half were fixed with the same procedures and decalcified with 5% EDTA-Na_2 (pH 7.2) in a cold room for 7 days, by changing the solution every two days. Small pieces of the samples from both halves fixed, dehydrated and embedded by the usual procedures were examined electron-microscopically. The results obtained were as follows. 1. In control teeth, three types of nerve endings were observed in the odontoblast layer and in the predentin. The first type was racket-like and was filled with several mitochondria. The second type was filled with a number of electron-lucent and agranular vesicles at different sizes, in contrast to the third type filled with a number of electrondense and granular and agranular vesicles at different sizes. 2. The degenerating changes of these three nerve endings seen in the odontoblast layer and in the predentin were observed with enlarged mitochondria devoid of cristae and enlarged vesicles at 5 to 10 days after all treatments. 3. Enlargement or disappearance of a number of agranular vesicles, mitochondria deveid of cristae and neurofilaments in the axoplasm was seen after Adaptic treatment, whereas degeneration of mitochondria and enlargement or disappearance of agranular vesicles were seen at 20 to 30 days after Dycal, Unident and Hi-Atomic treatments. In particular, electron-dense granules had a tendency to melt in the third type after the dental procedures except Adaptic treatment. 4. These changes observed in the three types at 20 to 30 days after Adaptic treatment were continued up to 60 days after treatment, but not after Hi-Atomic, Dycal and Unident treatmens. However, after both Dycal and Unident treatments, a number of granular vesicles of different sizes were clearly seen in the extreacellular space near the predentin, where collagen formation had newly occurred, which suggests a phenomenon of exocytosis. It could be concluded that types of nerve endings seen in the odontoblast layer and in the predentin were degenerated for a long time after Adaptic, but not Hi Atomic, Dycal and Unident treatments. In particular, the third type could be associated with collagen formation and calcification.
- 福岡歯科大学学会の論文
- 1991-10-30