Regeneration of Nerve Fibers in The Rat Gingival Epithelium Following Gingivectomy

Abstract

Gingivectomy is a periodontal surgery which favors a reformation of the gingival-tooth attachment. Information on the regeneration process of gingival nerve fibers is meager although that of axotomy has been well-documented. The regeneration process of rat gingival nerve fibers in gingivectomy was therefore examined by immunocytochemistry for PGP 9.5, CGRP, and p75-NGFR in comparison with that in axotomy. In the control group without any surgical treatment, the junctional and gingival sulcular epithelia received a dense supply of nerve fibers with each immunoreaction. In the axotomy group at postoperative day 7 (PO 7), the penetration of regenerating nerve fibers was recognizable in the gingival epithelium after the disappearance of any immunoreaction at PO 1. The gingivectomy group 1 also had no neural staining in healing tissues at PO 1. At PO 3, when the gingival epithelium had begun to regenerate, a few thin nerve fibers sprouted from the damaged nerve fibers in the connective tissue. Healed gingival connective tissue was reinnervated by PO 7, but intraepithelial nerve fibers were not found in the regenerated gingival epithelium until PO 14, indicating that neural regeneration occurred more quickly in axotomy groups than in gingivectomy groups. Since the gingival tissue has been suggested to have a potential for the production of neurotrophins such as nerve growth factor (NGF), it is considered that this time lag in neural regeneration between the two experimental groups is caused by the pres-ence/absence of the surrounding tissue which contains rich Schwann cells and fibroblasts.