Defense responses of dentin/pulp complex to experimentally induced caries in rat molars: An immunohistochemical study on kinetics of pulpal Ia antigen-expressing cells and macrophages.

Experimental caries was induced in rats that were innoculated orally with Streptococcus mutants and maintained on a cariogenic diet, During the caries process, kinetics of the pulpal Ia antigen-expressing cells and macrophages was monitored immunohistochemically and was correlated with caries depth and the status of reparative dentin formation. Initial pulpal response was characterized by a localized accumulation of Ia antigen-expressing cells beneath the dentinal tubules communicating with the superficial caries. This was followed by a caries-depth related increase of Ia antigen-expressing cells and macrophages in the coronal pulp, The accumulation of these cells under the dentin was most apparent when the caries had progressed into the reparative dentin, These findings suggest that the response of Ia antigen-expressing cells to carious irritants triggers the defense reactions of the pulp. The intensity of the defense reactions may be correlated with the permeability of carious dentin.