QUANTITATIVE COMPARISON OF CYTOTOXICITY OF DENTAL ANTISEPTICS TO NORMAL HUMAN ORAL KERATINOCYTES IN-VITRO

The cytotoxicities of antiseptics used in dentistry were examined with normal human keratinocytes from the oral cavity by the uptake of neut ral red (NR assay). The NR assay is a quantitative in vitro assay that distinguishes between viable, damaged or dead cells. Cultures from di fferent 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 me mbranes in the oral cavity was determined from the dose-response curve s of inhibition of NR uptake in cells treated with antiseptics for 2 d ays. As a quantitative measure of cytotoxicity, NR(50) (i.e. the conce ntration of antiseptics that resulted in a 50% decrease in NR uptake r elative to untreated controls) was extrapolated from dose-response cur ves. The rank-order of cytotoxicities (NR(50)) was Hyamine (10% benzet honium chloride solution) > Hibitane (5% chlorhexidine gluconate solut ion) > acrinol (0.2% acrinol solution) > Iodine Carbol (liquefied phen ol with 3% iodine) > iodine glycerin (glycerin with 10% iodine) > dilu te iodine tincture (3% iodine solution) approximate to iodine tincture (6% iodine solution) approximate to Isodine (10% povidone-iodine solu tion) > 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 th erapeutic benefit with minimal toxicity.