Recruitment of immunocompetent cells after dentinal injuries in innervated and denervated young rat molars: an immunohistochemical study.

The dental pulp represents a peripheral end-organ deprived of a collateral nerve supply. After inferior alveolar nerve (IAN) axotomy, rat molar pulp is denervated over a period of at least 6 days. Therefore, rat molar pulp was used as an experimental model to study the effect of sensory nerve fibers on influx of immunocompetent cells after dentinal injury. In the present study we performed a quantitative analysis of CD43+, CD4+, CD11b+, and I-A antigen-expressing cells subjacent to dentinal cavities in denervated and innervated first mandibular molars. For visualization of nerve fibers, antibodies to protein gene product (PGP) 9.5, the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP), and the sympathetic neuropeptide Y (NPY) were used. Immunohistochemistry was performed by the avidin-biotin-peroxidase method. In the innervated teeth, a correlation between increased sensory nerve density and influx of immunocompetent cells was found. Compared to the contralateral innervated molars, a significant reduction in recruitment of immunocompetent cells was found in the denervated pulp tissue subjacent to the dentinal cavities. The rat molar represents a unique model to illustrate the influence of sensory nerves and neuropeptides on inflammation and recruitment of immunocompetent cells.