Objectives: The exposed dental pulp possesses the ability to form a hard-tissue barrier (dentin bridge). However, the mechanisms by which pulp cells differentiate into odontoblasts in this process are not well understood. During primary dentinogenesis, odontoblasts express a number of mineral-related non-collagenous proteins, including bone sialoprotein (BSP), osteopontin (OPN) and dentin sialoprotein (DSP), a dentin-specific protein. Growth factors such as the TGF-b superfamily are also expressed by odontoblasts and TGF-bs are implicated in cell differentiation and tissue repair. The aim of this study was to investigate the expression of these molecules during reparative dentinogenesis. Methods: We observed these immunohistochemical localization in human teeth, after pulp was exposed and capped with calcium hydroxide. Results: At 14 days, a thin layer of fibrous matrix barrier was formed at the exposure site. An alignment of cells was observed adjacent to the barrier, some of which were weakly immunopositive for BSP, OPN and DSP. At 28 days, the hard-tissue barrier was thickened and pulpally lined with elongated odontoblast-like cells that expressed BSP, OPN and DSP. A number of globular structures intensely stained for BSP and OPN were observed between the cells, suggesting their role in mineralization. The odontoblast-like cells forming reparative dentin expressed TGF-bs, especially b2 and b3, and also TGF-b type II receptor. Conclusions: These results suggest that cells that form reparative dentin express odontoblast phenotype and that TGF-bs may be involved in the differentiation of replacement odontoblasts during reparative dentinogenesis after pulp capping. yoshiba@dent.niigata-u.ac.jp

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