In vitro study of differentiating odontoblasts in isolated rat incisor dental papillae.

The dental papillae isolated from rat incisor were examined morphologically and autoradiographically in order to investigate progressive odontoblast differentiation in vitro. Four to eight days after incubation, the preodontoblasts which were labelled with 3H-thymidine became elongated, polarized, odontoblast-like cells with long cytoplasmic processes. They produced an 3H-proline labelled extracellular matrix on the substrate with which the dental papillae were coated. In addition, the odontoblasts located on the initially formed predentin maintained their ordinary shape as elongated cell bodies with long cytoplasmic processes and polarity fo the organelles during the term of culture. The results indicate that the surface of the agar gel substrate may be a critical requirement for odontoblast differentiation, development, and maturation in the absence of both the basement membrane and the enamel epithelium in the culture system used in this study.