FC を応用した乳歯歯髓切断後の神経線維の動態に関する実験的研究

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  • An Experimental Study of the Changes in Nerve Fibers after Pulpotomy of Deciduous Teeth with Formocresol

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Ca(OH)_2-pulpotomy of the deciduous teeth in young dogs was performed with FC and the changes in the nerve fibers in the remaining living dental pulp after pulpotomy of the ends of the pulp nerve were examined neurohistologically. The results were as follows : 1. Three days after operation, the pulp directly under the necrosed layer showed slight inflammatory change, with several lymphocytes that were found the free ribosomes and several mitochondria in cytoplasm under the electron microscope. Findings of atrophy of the nuclei of pulp cells were seen in the surrounding tissues. The nerve fibers in this region were degenerated and an electron microscopic observation showed marked destruction of myelin of the myelin sheath and decrease in the microtubules in axon. 2. From seven to ten days, calcified tissue was observed in the cut surface of the pulp. In the adjacent pulp, large and spindle cells concentrated. The region of calcified tissue contained proper pulp tissue and degenerated nerve fibers were seen. An electron microscopic observation of the regenerated nerve fibers directed toward the calcified tissue showed myelinated nerve fibers which appeared to have undergone degeneration during regeneration, and the axon was approximately normal. 3. At 14 days, a finding of the initial formation of the dentin barrier was seen and a formation of slightly eosin-stained pre-dentin was seen in the innermost of the barrier. The radicular pulp was healthy. The nerve fibers under the electron microscopic obervation myelinated nerve fibers with sheaths, the nuclei of Schwanns cells, and nonmyelinated nerve fibers only with nerve processes. 4. At 21 days, the barrier was more compact in constitution than it was at 14 days and a continuous formation of pre-dentin from the peripheries to the mid-pulp was seen. In the dental pulp below the dentin barrier, minute nerve fibers began to appear. 5. At 35 days, formation of a thick dentin barrier was seen in the cutsurface of the pulp. No marked changes were seen in the pulp upto the root apex. Branches of nerve fibers began to appear in the pulp directly below the barrier. The nerve fibers in the pulp under the electron microscopic observation showed myelinated and non-myelinated nerves, and a large number of dense collagen fibers were seen between the nerve fibers. In the axon, neurofilament, microtubles, and mitochondria were always seen.

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