Cytotoxicity of ammonium hexafluorosilicate on human gingival fibroblasts

Ammonium hexafluorosilicate (SiF), which is claimed to significantly improve occlusion of dentinal tubules, was proposed as a novel desensitizer for dentine hypersensitivity (DH). However, the cytotoxicity of SiF on oral cells is lacking. The purpose of this study was to investigate the cytotoxicity of SiF on human gingival fibroblasts (hGFs) under different dosages (0.001%, 0.01%, 0.1%, and 1%) and treatment durations (1, 5, 10, and 30min). Cell proliferation, mitochondrial membrane potential (MMP) and cell cycle were tested by MTT assay, JC-1 staining and flow cytometry, respectively. Glutathione (GSH) depletion was analyzed to further investigate the underlying mechanism of SiF-induced cytotoxicity. MTT assay showed that there was significantly lower number of viable cells when the hGFs were treated with 0.01% (10min), 0.1% (10 and 30min) and 1% (5, 10, and 30min) SiF than the control group (p<0.05). MMP decreased and GSH depletion increased dramatically along with higher concentrations (0.1% and 1% SiF) and prolonged times (10 and 30min). DNA synthesis [S (%)] of cells treated with 0.1% and 1% SiF (5, 10, and 30min) was significantly lower than the control group (p<0.05). Our results indicate exposure to up to 0.01% SiF for less than 5min causes low or no cytotoxicity in vitro.