Effect of different diets on oral bacteria and caries activity in Sprague-Dawley rats.

The conventional rat model of dental caries has been used extensively to measure the contribution of various inoculated bacteria or diets to dental caries production. Only limited information is available on the effect of different diets on the oral bacterial community as a whole. In the present study, using selective and non-selective media, the oral bacterial populations of 21-day-old Sprague-Dawley rats fed diets with commercial rat and mouse cubes (control), high-starch (56%) and sucrose (56%) diets for 21 days were investigated. The high-starch diet did not significantly change the proportion of oral bacteria compared with the control group; the high-sucrose diet significantly enhanced the total cultivable bacteria, particularly Actinomyces naeslundii, Streptococcus rattus and Streptococcus suis-like bacteria. The order of diets with respect to the production of dental caries was sucrose > starch > normal. Thus the high-sucrose diet changed the oral bacterial population of Sprague-Dawley rats and these changes were reflected in the increased level of dental caries.