Staining and antimicrobial properties in vitro of some chlorhexidine formulations

Dietary staining studies have proved useful determinants of chlorhixidine activity in mouthrinse products, and results correlate with plaque inhibitory effects. This investigation compared the staining and antimicrobial action in vitro of two known and similarly effective, commercially available chlorhexidine mouthrinses with a reformulated 0.1% chlordexidine preparation. After adjustment for original concentration the 0.2%, 0.12% and reformulated 0.1% products had essentially similar, minimum inhibitory-dilution values against standard test organisms. The 0.1% preparation was more effective against Capnocytophaga ochracea, suggesting additional antimicrobial activity derived from an ingredient other than chlorhexidine. The staining in vitro of tooth and acrylic specimens was equivalent with the 0.2% and 0.12% products. By comparison with equivalent concentrations of the diluted 0.2% preparation, the 0.1% formulation produced less staining, particularly when diluted. The data suggest that the 0.1% formulation, when used in diluted form as recommended by the manufacturer, may have slightly reduced plaque-inhibitory effects by comparison to the 0.2% or 0.12% products. However, the results raise the question whether chlorhexidine solutions could be formulated to reduce side effects, in particular, tooth staining at the expense of some loss of antiplaque activity.