Bi-directional effects of the oral bacteria on dental pulp-derived fibroblasts

Objective: The oral bacteria have a variety of potential biological responses such as pathogenicity. Bacterial metabolites demineralize dental hard tissues and soluble factors lead to tertiary dentinogenesis in the area of the dentin-pulp complex. However, it is unclear whether the oral bacteria are directly involved in the generation of tertiary dentinogenesis. In this study, we showed bi-directional effects of oral bacteria on human dental pulp-derived fibroblasts. Methods: Human dental pulp-derived fibroblasts (hDPF) were obtained from third molar teeth and the cells were subcultured. The sonicated extracts were obtained from Porphyromonas gingivalis (gram-negative) and Streptococcus mutans (gram-positive) bacteria and their effects on cell growth and differentiation of hDPF were examined. Results: The numbers of hDPF were significantly lower at high concentration levels of P. gingivalis. Alkaline phosphatase activities were increased in the hDPF exposed to sonicated extracts form both species at low concentrations while the activity was decreased upon exposure to high concentrations of sonicated extracts from P. gingivalis. Conclusion: The results suggest that hPDF differentiation is induced at low levels of sonicated oral bacterial extracts. This is the first evidence that oral bacteria have a positive effect on cell differentiation.