Regulatory mechanism of cell differentiation and functional manifestation in the dental pulp.

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The purpose of the present study is to clarify the regulatory mechanisms and factors of cellular differentiation and functional manifestation in the cells of the dental pulp. In vitro experiments were performed to make clear the proliferative and differentiating natures of cultured cells of the dental pulp. In vivo experiments were carried out for invetigating the differentiation from dental pulp cells into odontoblasts. In situ experiments were fulfilled to elucidate the proliferation and differentiation of the dental pulp cells by means of the application of an adhesive resin 4-META/MMA-TBB-O on the exposed dental pulp.In vitro experiments showed that the cultured pulp cells had high alkaline phosphatase activity but low proliferative activity in comparison with cultured cells from periodontal ligament, bone marrow and muscle. Localization of alkaline phosphatase was definite at the dental pulp cells just below the odontoblast layr. No positive cell for proliferative cell nuclear ant … More igen (PCNA) was detected in the intact dental pulp. In vivo experiments demonstrated that the dental pulp cells could differentiated into odontoblasts following transplantation of the dental pulp associated with dentin or into a silicone-tube. However, bone tissue but not dentin was produced when the dental pulp alone was transplanted. Dentin bridge formation was observed in the partial pulpotomy but not in the total pulpotomy in germ-free rats. These results may suggest that the microenvironment is essential for differentiation from dental pulp cells into odontoblasts. In situ experiment using 4-META/MMA-TBB-O resin directly on the pulp tissues indicated that dentin bridge formation was found only about 40%, although neither necrosis nor inflammation could be recognized in the applied pulp tissues. A large numbers of macrophages were detected adjacent to the resin or dentin bridge in some cases of long term observation. Ultrastructural findings of the present study demonstrated the existence of the soft tissue hybrid layrs. Biochemical analysis implied the dissolution of some elements including carbonic acid, boric acid, and 4MET from the polymerized resin and the soft tissue hybrid layr. It is suggested that these elements may influence not only the cellular differentiation of the pulp cells but also the appearance of macrophages. Less