In vitro cytotoxicity of diverse preparations used in dental practice to human gingival keratinocytes

The cytotoxicities of diverse preparations used for dental practice were examined with normal human keratinocytes from gingival tissues by the uptake of neutral red (NR assay). Cultures from different individuals were established, and secondary cultures in serum-free medium were used. The cytotoxicities to cells treated for 2 days with gargles, mouthwashes, gingival massages, fluoride preparations, dentifrices and local anaesthetics were determined from the dose-response curves of inhibition of NR uptake. As a quantitative measure of cytotoxicity, NR(50) (the concentration of the preparations that resulted in a 50% decrease in NR uptake relative to untreated controls) was interpolated from dose-response curves. Dentifrices examined showed cytotoxicity similar to gingival massages but were more cytotoxic than any fluoride preparations, local anaesthetics, and most gargles and mouthwashes. The cytotoxicities of dentifrices were at least 6.5-fold those of fluoride preparations and 7.9-fold those of local anaesthetics. The results provide useful estimates of relative toxicities of dental preparations to human oral mucosa and are useful as a standard for cytotoxic assessment of newly developed preparations for dental use.