CELLULAR ORGANIZATION IN SUBODONTOBLASTIC ZONE OF DENTAL PULP .2. PERIOD AND MODE OF DEVELOPMENT OF CELL-RICH LAYER IN RAT MOLAR PULPS

An investigation was carried out to determine the period and mode of formation of the subodontoblastic cell-rich layer in the rat molar pulp. Pulp tissues of 48 rats aged 4 to 45 days were studied. No differences in cell density were evident between the subodontoblastic and other regions of the pulp until the period of eruption of the molar teeth into the mouth. The cell-rich zone was observed along the roof and lateral aspects of the coronal pulp at about the time of exposure of the tooth crowns to the oral fluids. Simultaneous with the development of the subodontoblastic cell-rich layer, a decrease in cell density occurred in the deeper regions of the pulp, suggesting that the cell-rich zone forms by peripheral migration of cells lying in the central regions of the pulp. Additional evidence in favour of this suggestion was provided by an experiment using the anti-mitotic drug colchicine. Increased cell proliferation was not found to occur in the subodontoblastic region during the period of formation of the cell-rich layer. The present findings have led to speculation that exposure of the molar tooth crowns to the salivary fluids may initiate in some way changes in cell distribution in the dental pulp. The evidence for this suggestion is discussed and further experiments designed to investigate this phenomenon outlined. © 1969.