Comparison of two commercially available chlorhexidine mouthrinses: I. Staining and antimicrobial effects in vitro

Several commercially produced chlorhexidine rinses are now available. These formulations vary in concentration and recommended regimens of use. One formulation, a 0.1% chlorhexidine rinse, anecdotally has been reported to not produce the characteristic dental staining. The aim of this study was to compare the 0.1% formulation with a 0.2% commercially produced chlorhexidine rinse for staining and antimicrobial effects in vitro. Tea staining of tooth and acrylic specimens exposed to the two rinses at various dilutions was measured over a 5-day period. Minimum inhibitory dilutions of each product against standard test bacteria were determined by agar dilution. The 0.1% product produced no staining of specimens greater than that noted with controls. At equivalent concentrations, the 0.2% product produced heavy staining of specimens. The antimicrobial effect of the two products was similar but the overall profile for the 0.1% preparation suggested activity derived from ingredients other than chlorhexidine. The results suggest that the chlorhexidine in the 0.1% rinse was partly or completely inactivated and, although staining may not occur in vivo, the formulation would have a much reduced antiplaque action.