The ability of Streptococcus salivarius TOVE-R to displace virulent representatives of the most prevalent human mutans streptococci from the teeth of rats, and thereby to inhibit caries, was studied. Streptococcus mutans 10449S- or Streptococcus sobrinus 6715-13WT-infected specific-pathogen-free rats consuming a high-sucrose diet were inoculated by TOVE-R. The infectants were differentially recovered from swabs of the teeth over the time course of infection and from sonically treated material of extracted teeth and excised tongues. Despite initial colonization of the teeth by the mutans streptococci, TOVE-R colonized the teeth, unlike other essentially nonvirulent plaque formers already described. It did not colonize the tongues of the rats. TOVE-R emerged and persisted as a prominent member of the plaque ecology. There was an associated decline in the mutans streptococci on the teeth, and this decline was associated with significant inhibition of the caries component attributable to 10449S infection (56%) and to 6715-13WT infection (52%). TOVE-R did not reliably inhibit the component of fissure caries attributable to the nonmutans indigenous flora of the rats. TOVE-R itself induced no detectable decay. The data suggest the potential therapeutic utility of TOVE-R to inhibit caries by displacement of mutans streptococci from the teeth. These results supplement the already reported ability of TOVE-R to preempt initial colonization of teeth by the mutans streptococci.

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