Histological Study of Reparative Dentin Formation after Direct Pulp Capping and Pulpotomy using MTA

Park, Seul Hee; Hwang, Ho Keel; Kim, Heung Joong; Park, Joo Cheol

Abstract

The ultimate goal of a regenerative pulp treatment strategy is to reconstitute normal tissue continuum at the pulp-dentin border, regulating tissue-specific processes of reparative dentinogenesis. However, little is known about the molecular mechanism of reparative dentinogenesis. The purpose of this study was to investigate the pulpal response after direct pulp capping and pulpotomy with mineral trioxide aggregate (MTA) by histological and immunohistochemical studies. There was continuous reparative dentin bridge formation at 2 weeks after treatment with MTA in both the pulp capping and the pulpotomy groups. The cells in the pulp capping group showed typical odontoblast characteristics, while the cells of reparative dentin in pulpotomy group were round in shape, lost their polarity, organized as a sheet of cells, and trapped in osteodentin-like mineralized tissue. In pulp capping group, upper layer of the reparative dentin showed cell lacunae indicating osteoblastic characteristics, whereas lower layer of the reparative dentin contained predentin and dentinal tubule-like structures as normal dentin. However, there was osteodentin formation in pulpotomy group. DSP protein was expressed at 4 weeks in odontoblasts of pulp capping group, while BSP was expressed at 4 weeks after pulpotomy. These results suggest that two different types of reparative dentin formation, dentin-like and bone-like dentin, may depend on the type and extent of the injury and the effect of the associated defense reaction on the structural and functional integrity at the dentin-pulp border.