Effect of chlorhexidine on multi-species biofilms. 
With human saliva as an inoculum, microcosm dental plaques were grown on dental amalgam in a constant-depth film fermentor (CDFF) in the presence (suc +ve) and absence (suc -ve) of sucrose.  The biofilms were then exposed to 0.2% chlorhexidine gluconate (CHG) for 1, 5, or 60 min and the survivors enumerated.  Suc +ve biofilms had higher proportions of streptococci but lower proportions of veillonellae than suc -ve biofilms.  Exposure to CHG for 1 min reduced the viable count of suc -ve and suc +ve biofilms by 53% and 89% respectively.  In both cases, reductions were mainly attributable to killing of streptococci and actinomyces.  After 60 min of exposure, 4% of the bacteria in the suc -ve and 2% in the suc +ve biofilms remained viable.  This study has shown that large numbers of bacteria in microcosm dental plaques can survive a 1-min exposure to 0.2% CHG and that even after a 60-min exposure, substantial numbers of bacteria remain viable.