The effects of hydrogen peroxide on the proliferation ability and odontogenic differentiation ability of hDPCs

Hydrogen peroxide (HP) is widely used in tooth whitening; however, the incidence of dentin hypersensitivity after tooth whitening is relatively high. This study aimed to evaluate the effect of different concentrations of HP bleaching solution on the viability of human dental pulp cells (hDPCs) and their odontogenic differentiation ability. This study was divided into control group (no treatment) and experimental groups. The experimental groups were cultured with gradient HP concentration for 24 h, then the proliferation (through CCK-8), mineralization ability of hDPCs (through Alkaline Phosphatase activity assay and alizarin staining assay) and the expression level of odontogenic related gene (through real time PCR) were evaluated. CCK-8 method showed that, after 24 h cultured with HP, 1 µg/mL and 5 µg/mL groups had no significant difference compared with the control group while other groups all had inhibitory effects on the proliferation of hDPCs. Alkaline Phosphatase (ALP) activity assay and alizarin red staining assay showed that there was no significant difference between the 1 µg/mL group and the control group in the mineralization ability. After cultured for 7 days, 5 µg/mL and 10 µg/mL groups could increase the activity of ALP and promote the formation of mineralized nodules. The expression level of odontogenic related gene of 5 µg/mL group increased, while that of 10 µg/mL group decreased. hDPCs can overcome the damage of HP and undergo a complete repair with stimulation of low concentration of HP (1 µg/mL, 5 µg/mL), whereas its odontogenic differentiation ability and cell homeostasis may be damaged under the stimulation of high concentration of HP (10 µg/mL).