Relative cariogenicity and in-vivo plaque-forming ability of the bacterium Streptococcus oralis in gnotobiotic WAG/RIJ rats.

The rats, fed a high sucrose diet, were mono-infected with seven strains of Streptococcus oralis. Moderate levels of caries were induced by four strains, and three others induced low levels. Approximal lesions were induced by two strains; no buccal/lingual lesions were produced. Scanning electron microscopy showed that all strains colonized the tooth fissures, some strains producing a moderately abundant and dense plaque. The most cariogenic strains (PB178, PB180 and PB186) induced similar levels of caries to Streptococcus milleri.