象牙質被蓋形成過程における歯髄細胞ならびに神経線維の電子顕微鏡的観察

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There are many reports on healing after pulp amputation and subsequent capping by calcium hydroxide. They focused primarily on the calcifying mechanism or on the differentiation of pulpal cells into preodontoblasts and odontoblasts during the formation of osteoid dentine or predentine. However, the origin of odontoblast forming the dentine bridge is still unclear. Then, in order to elucidate the mechanism of dentine bridge formation and the role of nerve terminals in healing after amputation during the differentiation of primitive mesenchymal cells into preodontoblasts and odontoblasts, and during the formation of predentine, and dentine, electron microscopic observations were made of tissue reactions during hard tissue formation. Thirty six canine and molars teeth were obtained from 6 adult dogs. Amputation was performed with diamond points and bur under general and local anesthesia, and applied with calcium hydroxide. These teeth were extracted at 5,7,10,15,20,30,45,50,60 days after operation. Immediately after extraction, these were fixed with 4% glutaraldehyde (cacodylate buffer, pH7.4) for 12h and 1% osmium tetroxide (cacodylate buffer, pH7.4) for 2h. Thereafter, the teeth were split longitudinally in two halves and their intradental tissues were excised carefully. Small pieces of the samples were fixed, dehydrated and embedded by the usual procedures. Ultrathin sections were cut in an ultramicrotome (Porter Blum MT2-B) equipped with a diamond knife. After staining with uranyl acetate and lead citrate, they were observed with a transmission-electron microscope (JEM-1200EX). 1. At an early stage of hard tissue formation, many nerve terminals and fibers infolded in a osteocyte or osteoblast-like cells were observed. 2. These nerve terminals were oval or round, and ranging from 0.3 to 5μm in diameler. These nerve terminals had a few mitochondria, numerous small and large vesicles, and maltivesiclar bodies. 3. Vesicles in the nerve terminal were categorized into three types. Type I contained middle density and small vesicles (4〜6nm). Type II had a dense core and intermediate vesicles (10〜20nm). Type III had a hight density and large vesicles (about 150nm). 4. Some of the middle dense core vesicles in contact with the odontablastic process adhered to the cell membrane of a nerve terminal.
福岡歯科大学学会の論文
1995-12-31

象牙質被蓋形成過程における歯髄細胞ならびに神経線維の電子顕微鏡的観察

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