FC を応用した Apexogenesis に伴う歯髄内神経線維の動態に関する実験的研究

Abstract

Formocresol was applied to immature teeth of young dogs and change in nerve fibers in dental pulp was investigated neurohistologically on apexogenesis. The results were as follows : 1. Nerve fibers in the necrosed layer directly under the pulpotomied surface generally showed swelling, decrease in staining properties, lysis, and disappearance. 2. On the 3rd day postoperatively, slight hyalinization and infiltration of inflammatory cells were observed in the dental pulp directly below the surface layer of living dental pulp, or so called the demarcation layer (von Kossa reaction layer). Nerve fibers in the dental pulp to the portion below the demarcation layer showed degenerated and swollen nerve fibers, fragmented small nerve bundles, single nerve fibers, and traces. In the dental pulp at the mid-portion of the root canal, however, regenerated nerve fibers accompanied by Schwann cells were observed. 3. On the 7th day postoperatively, formation of calcified tissue was observed in the pulpotomied surface, and the dental pulp slightly downward showed hyalinization, bleeding, slight inflammatory cell infiltration. Nerve fibers in the dental pulp below the calcified tissue showed swelling, ruptures, granulated degnerative nerve fibers. In the dental pulp from the mid-portion of the root canal pulp to the apex, minute nerve bundles, small nerve bundles, single nerve fiberd, and nerve fibers accompanied by Schwann cells were observed running upward. 4. On the 14th day postoperatively, a finding of the early stage of calcified barrier formation was seen in the pulpotomied surface. Directly under it, findings of hyalinization, bleeding, and slight inflammatory cell infiltration were seen. The dental pulp below showed the normal findings and apposition of cellular cementum began in the apical region. Most nerve fiber bundles leading to the underside of the calcified barrier were degenerated. 5. On the 35th day postoperatively in the pulpotomied surface, formation of the calcified barrier, formation in places of young dentins stained lightly in eosin, and structures of dentinal tubules were observed. The dental pulp directly under the barrier showed hyalinization, bleeding, and inflammatory cell infiltration. The apical region was being obliterated with thin cellular cementum. Lysis and disppearance of most of the nerve fibers in the barrier were observed. Directly under the barrier, most nerve fibers were degenerated, but in some marginal zones, minute nerve bundles and single nerve fibers were observed. 6. From 95 to 120 days postoperatively in the pulpotomied surface, formation of the dentin barrier, narrowing of the pulp chamber, obliteration of the apical region with cementum, and collateral branches were observed. In the dental pulp directly under the barrier, inflammatory cell infiltration and hyalinization still continued. However, the dental pulp further below to the apex region showed the normal findings. Nerve fibers at this stage thickened and large, medium, and small nerve bundles were seen. Fine nerve fibers were also seen running. Branches terminating in the direction of the odontoblast layer were seen but the stage for formation of nerve plexuses was not yet reached. 7. On the basis of the foregoing, although application of formocresol on the pulpotomied surface and capping the surface with calcium hydrate cause reactive inflammation in the region directly under the suface, this method does not appear to hinder growth of the root thereafter or obliteration of the apex, or so called apexogenesis.