Effects of hydrogen peroxide (H2O2) on alkaline phosphatase activity and matrix mineralization of odontoblast and osteoblast cell lines

Hydrogen peroxide (H2O2), an oxidizing agent, has been widely used as a disinfectant. Recently, because of its reactive properties, H2O2 has also been used as a tooth bleaching agent in dental care. This is a cause for concern because of adverse biological effects on the soft and hard tissues of the oral environment. To investigate the influence of H2O2 on odontoblasts, the cells producing dentin in the pulp, we assessed cellular viability, generation of reactive oxygen species (ROS), alkaline phosphatase (ALP) activity, and nodule formation of an odontoblastic cell line (MDPC-23) after treatment with H2O2, and compared those with the effects on preosteoblastic MC3T3-E1 cells. Cytotoxic effects of H2O2 began to appear at 0.3 mmol/L in both MDPC-23 and MC3T3-E1 cells. At that concentration, the accumulation of intracellular ROS was confirmed by a fluorescent probe, DCFH-DA. Although more ROS were detected in MDPC-23, the increasing pattern and rate are similar between the two cells. When the cells were treated with H2O2 at concentrations below 0.3 mmol/L, MDPC-23 displayed a significant increase in ALP activity and mineralized bone matrix, while MC3T3-E1 cells showed adverse effects of H2O2. It is known that ROS are generally harmful by-products of aerobic life and represent the primary cause of aging and numerous diseases. These data, however, suggest that ROS can induce in vitro cell differentiation, and that they play a more complex role in cell physiology than simply causing oxidative damage.