Immatured dental pulp responses under hypoxic in vitro

Objectives: It is known that the use of local anesthetics containing vasoconstrictors, which can reduce pulpal blood flow and result hypoxic condition. The purpose of this study was to investigate the immature dental pulp responses under the condition of hypoxia.

Methods: The pulp cells were obtained from molar teeth of 4 weeks old SD rats, weighing approximately 100 g and cultured. In the hypoxia group, pulp cells were incubated under hypoxic conditions (2% O2) for one to four days. In the control group, pulp cells were incubated under normoxic conditions (20% O2) for one to four days. Cell proliferation ratio and expressions of vascular endothelial growth factor (VEGF)-, alkaline phosphatase (ALP)- and dentin sialophosphoprotein(DSPP)-mRNAs were analyzed by reverse transcriptase polymerase chain reaction.

Results: The proliferation ratio of cultured immature pulp cells in the hypoxia group was significantly lower than that of control group at 2, 3 and 4 days (p<0.01). The expression of VEGF-mRNA in the hypoxia group was significantly lower than that of control group at each of the time period (p<0.01). The expression of ALP-mRNA decreased with time-dependent in both groups, however there was no significant difference in both groups at any of the time periods. The expression of DSPP-mRNA increased with time-dependent in both groups.

Conclusions: These results suggested that hypoxia did not affect dentinogenesis under the hypoxic conditions, but reduced the function of vascularization and cell proliferation, and this might effect the wound healing of pulp tissue when the pulp was damaged.