The comparative cariogenicity and plaque-forming ability in vivo of four species of the bacterium Actinomyces in gnotobiotic rats.

Gnotobiotic WAG/RIJ rats on a high sucrose diet were monoinfected with 12 strains of Actinomyces spp. Moderate levels of caries were induced by a single strain of Actinomyces naeslundii and low levels by two strains of Actinomyces viscosus, three strains of A. naeslundii and one strain of Actinomyces israelii. No caries was induced by single strains of A. viscosus and A. israelii or by three Actinomyces odontolyticus strains. Only fissure caries was observed. Scanning electron microscopy showed that all strains colonized the fissures and most colonized the lingual surface of the teeth, but to a limited extent. Production of abundant and dense plaque was not always accompanied by caries.