STREPTOCOCCI AND ACTINOMYCES INHIBIT REGROWTH OF STREPTOCOCCUS-MUTANSON GNOTOBIOTIC PET MOLAR TEETH AFTER CHLORHEXIDINE VARNISH TREATMENT

Clinical studies suggest that the long-term suppression of mutans stre ptococci on tooth surfaces after intensive chlorhexidine therapy is ma inly due to bacterial interference. Other streptococci and also Actino myces naeslundii are proposed to inhibit regrowth of mutans streptococ ci after suppression by the agent. We have tested this hypothesis in g notobiotic rats associated with Streptococcus mutans alone, or associa ted with S. mutans and strains of Stveptococczu oralis, Streptococcus sanguis, Streptococcus gordonii, Streptococcus mitis biovar I, and A. naeslundii. Left lower jaws in these rats were treated with concentrat ed chlorhexidine varnish, and the return of S. mutans on the treated j aws monitored. In monoassociated rats, S. mutans regained the level of the untreated right lower jaw in approximately 1 week. In contrast, S . mutans remained suppressed for several weeks in rats multi-associate d with other streptococci and actinomyces strains. The suppression was more pronounced in the rats fed on basal diet with little free sugars than in rats fed on a sucrose-containing diet. Counts of other strept ococci recovered quickly from the intensive chlorhexidine treatment, b ut A. naeslundii remained suppressed for at least I week. The findings demonstrate the crucial importance of the oral microflora in controll ing regrowth of mutans streptococci after chemotherapy.