The interaction of diet and microflora in experimental caries in the rat

Abstract

Weanling rats were pretreated with tetracycline and erythromycin and subjected to a caries test period on either Diet 580 (associated with caries on all tooth surfaces) or Diet 585 (associated with caries in the sulci only). One group on each diet was maintained as controls, two groups were reinfected by exposure, one to donor animals which had been on Diet 580 and one to donors on Diet 585. Exposed animals on Diet 580 developed both sulcal and smooth-surface lesions, irrespective of the diet consumed by the donor animals from which they were infected. This indicates that a microflora capable of inducing smooth surface caries was supported by both diets and transmissible from both groups of donors. The control animals on Diet 580 developed lesions in the molar sulci only, indicating that a segment of their microflora which was essential for the induction of caries on the smooth surfaces had been selectively eliminated by the antibiotic treatment. All animals receiving Diet 585, whether they were uninfected controls or exposed to donors, developed carious lesions almost exclusively in the sulci. The results indicate (1) that a specific type of microflora is required for the development of smooth-surface caries and (2) that even in the presence of such a flora and a diet which can support it, smooth-surface lesions may not occur. It is suggested that in the case of Diet 585 this was due to the inability of microbial plaques to accumulate on the smooth surfaces of the molars.