Cytotoxicity tests of in situ polymerized resins: methodological comparisons and introduction of a tissue culture insert as a testing device.

The in vitro cytotoxic potential of six commonly used methacrylate polymers was evaluated using human oral fibroblast cultures with different cell-material contact systems. A tissue culture insert was introduced to test resin-released components. Both acute and delayed cytotoxic effects of resin were quantified by cellular enzymatic and DNA synthetic activities of fibroblasts over a 6-day exposure period. Resin toxicity was material-dependent. Statistical analysis showed that the experimental conditions significantly contributed to the overall toxicity and the cytotoxicity pattern for a given material. DNA synthesis activity of human oral fibroblasts assayed by 3H-thymidine incorporation was more sensitive to resins than cellular enzyme activity, as determined by tetrazolium bromide reduction. However, extended exposure increased the cytotoxicity of all resins, as measured by tetrazolium bromide reduction, which seemed to be a better indicator of the development of resin toxicity than 3H-thymidine incorporation. Removal of the oxygen inhibition layer on resin specimens partially enhanced cell viability, indicating that this surface layer together with other unknown factors contributed to resin toxicity.