Responses of Immunocompetent Cells in Dentin Bridge Formation after Pulpotomy

Objective: The aim of the present study was to investigate the responses of heterogeneous populations of macrophages in order to determine their effect on dentin bridge formation using calcium hydroxide during the healing process after a pulpotomy.Method: The first maxillary molars from Wistar rats (n=60), 56 days old, were obtained. The rats were sacrificed at 1, 3, 7, 14 and 28 days postoperatively. The residual pulp of the first maxillary molars was evaluated by both immunohistochemistry and immunoelectron microscopy to anti-class II molecules (OX6 antibody) and monocyto/macrophage lineage cells (ED1 antibody). Result: By 1-3 days postoperatively, ED1- and OX6-positive cells were widely distributed under the demarcation zone and many ED1-positive cells appeared phagocytic vesicles. By 7 days postoperatively, some ED1 and OX6-positive cells accumulated along the differentiating odontoblast layer to be found. By 14 days postoperatively, the pulp progressively lost the ED1- and OX6-positive cells and a few OX6+ DC cell-like cells were found to be in close contact with the differentiating odontoblast bodies. By 28 days postoperatively, the density of ED1- and OX6-positive cells were less than that observed at 14 days. In addition, a few ED1+cells were found in the odontoblast layer and predentin. Conclusion: This study may provide a basis for investigating the participation and changes and variety function of macrophages in wound healing and represent strong evidence that the heterogeneous populations of macrophages may play a role in dentin bridge formation.