The effects of fluoride on the percentage bacterial composition of dental plaque, on caries incidence, and on the in vitro growth of Streptococcus mutans, Actinomyces viscosus, and Actinobacillus sp.

Administration of 250 mug/ml NaF in drinking water to rats reduced both caries incidence (P less than 0.001) and the percentage of S mutans (0.01 greater than P greater than 0.001) although the percentage of Actinobacillus sp. was increased (P less than 0.001). An Actinobacillus sp. and S mutans FA1 both proliferated in NaF broth only if the NaF greater than 10 mug/ml, which was associated with the inhibition of acid production.