Differentiation of Pulpal Cells and Inductive Influences of Various Matrices with Reference to Pulpal Wound Healing

Abstract

Based on recent literature, the dynamics of mesenchymal cells in transplantation of various tissues and matrices, as well as the origin of new odontoblasts which participate in the formation of the dentin bridge, are described. Experiments involving implantation of pulp, periosteum, perichondrium, treated dentin, and bone matrices were performed to emphasize the capability of these cells to produce hard tissue. Light and electron microscopic and autoradiographic studies were carried out to clarify the origin of replacement odontoblasts. It appears that the pulp cells, endothelial cells, and pericytes become undifferentiated mesenchymal cells following pulp exposure. These mesenchymal cells differentiate into odontoblasts, which subsequently produce a dentin matrix. Pulp tissues autografted to non-pulpal sites, elaborated bone (or osteodentin) matrix, but they did not graft to tubular dentin. An experiment on dentin bridge formation, using germ-free rats, demonstrated that the pulp tissue has intrinsic healing potential. Therefore, it was concluded that the ability of pulp tissue to elaborate hard tissues depends on its environment.

Autoradiographic analysis of odontoblast replacement following pulp exposure in primate teeth

“…Indeed, fibroblast-like cells are able to differentiate into either osteoblasts or chondroblasts depending on the nature of the surrounding matrix and the amounts of vascular-derived oxygen (Indue et al, 1981). Given the proper environment, they may also be able to differentiate into replacement odontoblasts, as suggested by Fitzgerald (1979), Yamamura et al (1980, Yamamura (1985) and Tziafas and Kolokuris (1990). The shift in numbers of fibroblast-like and odontoblast-like cells in zone 1 between Days 8 and 10, was not seen between Days 10 and 12 in zone 1.…”

“…These patterns suggest a migration of cells from the deeper pulp (represented by zone 3) through an intermediate area (zone 2) into the area directly against the capping agent (zone l), and support the findings of Sveen and Hawes (1968), Feit et al (1970), Yamamura er al. (1980) and Yamamura (1985). Tziafas and Kolokuris (1990) demonstrated that cells in the deep pulp can differentiate into odontoblasts when exposed to demineralized dentine surgically implanted in the pulp.…”

“…Others have proposed that replacement odontoblasts are derived from either undifferentiated mesenchymal cells in the pulp proper that are induced to differentiate into odontoblasts or from differentiated pulpal cells that are induced to dedifferentiate into undifferentiated cells and then redifferentiate into odontoblasts (Fitzgerald, 1979;Yamamura et al, 1980;Yamamura, 1985;Tziafas and Kolokuris, 1990). This process would require recruitment and induction of a cell population(s) within the pulp proper after pulpal trauma, one or more DNA replication cycles and finally differentiation into functioning odontoblasts.…”

“…This process would require recruitment and induction of a cell population(s) within the pulp proper after pulpal trauma, one or more DNA replication cycles and finally differentiation into functioning odontoblasts. Studies with [3H]-thymidine in wounded, non-exposed pulps (Sveen and Hawes, 1968) as well as in pulps wounded by exposure (Feit, Metelova and Sindelka, 1970;Yamamura et al, 1980;Yamamura, 1985) have demonstrated that DNA replication can occur during the replacement of odontoblasts lost due to trauma. The replacement cell population in this type of pulp healing could be located anywhere within the coronal pulp, as suggested by Fitzgerald (1979) Yamamura et al (1980) Yamamura (1985 and Tziafas and Kolokuris (1990).…”

“…Studies with [3H]-thymidine in wounded, non-exposed pulps (Sveen and Hawes, 1968) as well as in pulps wounded by exposure (Feit, Metelova and Sindelka, 1970;Yamamura et al, 1980;Yamamura, 1985) have demonstrated that DNA replication can occur during the replacement of odontoblasts lost due to trauma. The replacement cell population in this type of pulp healing could be located anywhere within the coronal pulp, as suggested by Fitzgerald (1979) Yamamura et al (1980) Yamamura (1985 and Tziafas and Kolokuris (1990). The cell types involved could be from fibroblastic (Fitzgerald, 1979;Yamamura et al, 1980), vascularrelated (Yamamura et al, 1980), and undifferentiated mesenchymal (Yamamura et al, 1980) lines.…”