Quantitative comparison of cytotoxicity of dental antiseptics to normal human oral keratinocytes in vitro

Abstract

The cytotoxicities of antiseptics used in dentistry were examined with normal human keratinocytes from the oral cavity by the uptake of neutral red (NR assay). The NR assay is a quantitative in vitro assay that distinguishes between viable, damaged or dead cells. Cultures from different individuals were established, and secondary cultures in serum-free medium were used. The amount of NR extracted from cells after a 3-hr uptake of the dye was linearly proportional to the number of cells exposed to the dye. The cytotoxicity of antiseptics used on mucous membranes in the oral cavity was determined from the dose-response curves of inhibition of NR uptake in cells treated with antiseptics for 2 days. As a quantitative measure of cytotoxicity, NR 50 (i.e. the concentration of antiseptics that resulted in a 50% decrease in NR uptake relative to untreated controls) was extrapolated from dose-response curves. The rank-order of cytotoxicities (NR 50) was Hyamine (10% benzethonium chloride solution) > Hibitane (5% chlorhexidine gluconate solution) > acrinol (0.2% acrinol solution) > Iodine Carbol (liquefied phenol with 3% iodine) > iodine glycerin (glycerin with 10% iodine) > dilute iodine tincture (3% iodine solution) ≈ iodine tincture (6% iodine solution) ≈ Isodine (10% povidone-iodine solution) > Oxydol (3% hydrogen peroxide solution). These results provide useful estimates of relative toxicities of antiseptics to human cells, which can be compared with antimicro-organism activity to maximize therapeutic benefit with minimal toxicity.