The purpose of this study was to investigate the effects H2O2 treatment on the mineralization ability of human dental pulp (HDP) cells. Reactive oxygen species (ROS) given off as by-products of cell metabolic activity are known to cause various diseases. However, when produced in small amounts, they are reported to stimulate cell proliferation, possess antiseptic properties and function in cell signaling systems. We have reported previously that laser irradiation increases H2O2-derived free radical production and mineralization ability in HDP cells. In this experiment, we used the dimethyl sulfoxide (DMSO) as a scavenger of hydroxyl radicals. HDP cells were treated with 1×10-3 mol/l, 1×10-4 mol/l, 1×10-5 mol/l, 1×10-6 mol/l, and 1×10-7 mol/l of H2O2, 1×20-2 mol/l of DMSO, and a mixture of 1×10-2 mol/l DMSO and 1×10-5 mol/l of H2O2. Non-treated cells served as a control. Gene expression of BMP-2 and ALP in cells treated with 1×10-5 mol/l H2O2 was greater than that in the others. The ALP activity and production of BMP-2 were highest in cultures treated with 1×10-5 mol/l H2O2. Calcified nodule formation was increased on day 28 by the treatment with 1×10-5 mol/l H2O2. These results suggested that mineralization of HDP cells was enhanced by 1×10-5 mol/l H2O2.
