象牙質被蓋形成過程における神経線維, 神経終末に関する電子顕微鏡的観察
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There are many reports on healing after pulpotomy and subsequent capping by calcium pydroxide. They focused primarily on the calcifying mechanism or on the diferentiation 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 pulpotomy during the differentiation of primitive mesenchymal cells into preodontoblasts and odontoblasts, electron microscopic observations were made of tissue reactions during hard tissue formation. Eighteen teeth were obtained for treatment of orthodontic or preventation. Pulpotomy was performed with diamond points and bur under general and local anesthesia, and applied with calcium hydroxide. These teeth were extracted at 1,2,3,4,5 weeks after operation. Immediately after extraction, these were fixed 4% glutaraldehyde (Cacodylate buffer, pH 7.4) for 6-8h and 1% osmium tetroxide (Cacodylate buffer, pH 7.4) for 2h. Thereafter, the teeth were spilt longitudinally in two halves and their intradental tissues were excised carefully. Small pieces of the samples were fixed, dehydrated and embedded by the usual procedure. 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 an electron microscpe (JEM-1200EX), and the following results were obtained. 1. One week after pulpotomy. Changes of unmyelinated nerve fibers and nerve terminals were seen among the fibroblasts and around the distrophic-calcificated area. In this stage, apex of the fiber slightly enlarged like a grow cone and branched a right angle. Many pinocytotic vesicles were seen in the endotherial cell and the fibroblast phagocyted collagen fiber was observed. 2. Two weeks after pulpotomy. Growth cone was garded incomplite by the schwan like cell arounded with calcified layer. Two type of nerve terminal (small and large, two kinds of granule) were seen and presynaptic membrane was seen between the fibroblasts. 3. Three weeks after pulpotmy. Residual root pulp was covered by osteoid-dentine bridge. In the nerve terminals, dark or clear-cored vesicles and small or large vesicles, mitochondria and martivesicular body or secondary lysosomes were observed. 4. Four〜five weeks after pulpotomy. Dark and clear odontoblasts were arranged at calcified front. At the area of calcified front, nerve terminals having the hight density granules were observed. In this post stage, the presynaptic between a odontoblastic process and a nerve terminal was seen. 5 . Four〜five weeks after pulpotomy. Degenerated nerve fiber filled with various kinds of vesicles, lysosome and myelinated organera increased. Normal nerve fiber and terminal in the predentine and odontoblast layer decreased in number. Therefore, it was suggested that starting point of dentine bridge formation exist in the place of about 1mm beneath the necrotic layer which the sprouting of nerve fiber and capillary were seen.
- 福岡歯科大学学会の論文
- 1997-09-30
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- 象牙質被蓋形成過程における神経線維, 神経終末に関する電子顕微鏡的観察