Stannous chloride (SnCl2, 35%) can increase microtensile bond strength between a self-etching adhesive and dental hard tissue either alone or in combination with phosphoric acid (H3PO4, 35%). Whereas cell toxicity of H3PO4 has been sufficiently investigated, little is known about the toxicity of concentrated SnCl2. The present study determined the in vitro toxicity of SnCl2, H3PO4, the primer of a self-etching adhesive (Clearfil SE) and combinations thereof at three concentrations (0.01%–0.3%) in a L929 fibroblast bioassay. Cell viability was determined by MTT (3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the integrity of cell membranes was visualised by trypan blue staining (cell necrosis assay). Cell viability was impaired at concentrations between 0.09% and 0.13% for SnCl2, between 0.06% and 0.09% for H3PO4, and between 0.19% and 0.29% for Clearfil SE primer. Combinations of agents showed additive toxic effects. SnCl2 showed a slightly lower but comparable in vitro toxicity to H3PO4, which gives a perspective for further in vitro, in situ and clinical studies on this issue, and for the intraoral use of SnCl2 to increase bond strength between an adhesive system and both enamel and dentine.

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