Apexogenesis に伴う歯髄内神経線維の消長に関する実験的研究

Abstract

Pulpotomy with calcium hydroxide was performed on teeth with incomplete root of young dogs, and growth of root and apical closure thereafter, or changes in pulpal nerve fibers at what is called Apexogenesis were investigated neurohistologically. The results were as follows : 1. On 7th day postoperatively, regenerated nerve fibers extended to the matrix formed directly under the boundary zone of the plane of pulp cross section. On 14th day, degenerated nerve fibers remaining in the living pulp were nearly nil. This stage corresponded to non-apposition stage of cellular cementum of root apex in normal growth of root, and medium and small nerve bundles, single nerve fibers, and minute nerve fibers with Schwann cells were seen ascending straight mainly in the region between the tips of Hertwig's epithelial sheath in the pulp of the root. 2. On 35th day, the dentin barrier was formed about evenly. Regenerated nerve fibers and their branches extended toward the periphery, branched out further on reaching the periphery, and formed relatively sparse nerve plexuses. This stage corresponded to apposition stage of cellular cementum of root apex in normal growth of root, and was characterized by degenerative findings of tortuous courses and moniliform in the nerve fibers penetrating between cementoblasts and in the nerve fibers penetrating through gaps where future side branches would be. 3. On 95th day, formation of dentin barrier and root dentin was stabilized. At the same time, nerve plexuses at the periphery of dentin barrier were dense and nerve endings were abundant. Many individual nerve fibers had about the same width as the contrast. This stage corresponded to terminal stage of root formation, and was characterized by arrangement into bundles of nerve fibers penetrating into the pulp, penetration together with blood vessels of mainly large, medium, and small nerve bundles through apical branches, and by absence of minute nerve fibers with Schwann's cells, and reduction in single nerve fibers.