Cytotoxicity of sodium fluoride on human oral mucosal fibroblasts and its mechanisms

Because sodium fluoride (NaF) is widely used for prevention of dental carie s, pathobiological effects of NaF were investigated on human oral mucosal f ibroblasts. The results showed that NaF was cytotoxic to oral mucosal fibro blasts at concentrations of 4 mmol/L or higher. Exposure of cells to NaF fo r 2 h also inhibited protein synthesis, cellular ATP level and functional m itochondrial activities in a dose-dependent manner. However, incubation of cells with NaF up to 12 mmol/L for 2 h depleted only 13% of cellular glutat hione level. The IC50 Of NaF on cellular ATP level was about 5.75 mmol/L. P reincubation of the cells with pyruvate and succinate did not protect cells from NaF-induced ATP depletion. At concentrations of 4 mmol/L, 8 mmol/L an d 12 mmol/L, NaF inhibited 31%, 56% and 57% of mitochondrial functions, res pectively, after 2 h incubation. No significant inhibition for NaF was foun d at concentrations lower than 2 mmol/L (40 ppm). These results indicate th at NaF can be toxic to oral mucosal fibroblasts in vitro by its inhibition of protein synthesis, mitochondrial function and depletion of cellular ATP. Because of repeated and long-term usage of NaF, more detailed studies shou ld be undertaken to understand its toxic effects in vitro and in vivo.