An ultrastructural study of the differentiation of mesenchymal cells in implants of allogeneic dentine matrix on the amputated dental pulp of the dog

Abstract

The sequential transition of the cells adjacent to autolysed antigen-extracted allogeneic dentine matrix was observed in a cavity on the amputated pulp in vivo. One week post-operatively, cells having poorly developed organelles and many free ribosomes, reminiscent of dedifferentiated or embryonic cells, were seen in migration and forming attachments to the allogeneic dentine matrix. Two weeks post-operatively, the cells close to that matrix had polarized nuclei and a clear distal area with minute processes, suggestive of preodontoblasts. Matrix vesicles were observed in the newly formed predentine-like matrix close to the allogeneic matrix. Some of the matrix vesicles contained needle-like crystals. Four weeks post-operatively, long, polarized cells with a well-developed endoplasmic reticulum and Golgi apparatus were seen. They contacted via a terminal web with desmosomes and tight junctions, and each had a long process extending into the predentine-like matrix, suggesting that they were identical to odontoblasts. These findings suggest that in the repair of the amputated pulp implanted with allogeneic dentine matrix the differentiation of odontogenic cells and initial mineralization may be analogous to those in normal dentinogenesis.