CGRP immunohistochemistry in wound healing and dentin bridge formation following rat molar pulpotomy

The aim of the present study was to investigate the neuropeptide CGRP in order to determine the effect on dentin bridge formation during the healing process after pulpotomy. First maxillary molars in 56-day-old Wistar rats (n=60) were used. The rats were killed for a neurohistopathological examination at 1, 3, 7, 14, and 28 days postoperatively. Neuronal changes in the residual pulp were studied using CGRP immunohistochemistry. By 1-3 days postoperatively, the CGRP-IR nerve fibers with abnormal beaded or knob-like structures were found to be more swollen than in the control and the leakage of a CGRP-IR-positive substance from the involved end of the nerve fibers was seen. At 7 days postoperatively, a vast number of newly sprouted CGRP-IR nerve fibers appeared in the residual pulp and some of them terminated in the differentiating odontoblast layer and the initial matrix layer of the dentin bridge. By 14-28 days, the nerve density had become progressively lower in the residual pulp. Regenerated axons also terminated in the odontoblast layer and the fibrous matrix layer of the calcified dentin bridge. These findings suggest that such sensory neuropeptides as CGRP may, therefore, play a role in dentin bridge formation in the rat molar.