Response of Harvard Caries-susceptible and Caries-resistant Rats to a Severe Cariogenic Challenge

¹ U.S. Department of Health, Education, and Welfare, Public Health Service, National Institutes of Health, National Institute of Dental Research, Bethesda, Maryland

The Harvard "caries-susceptible" and "caries-resistant" strains of rats have been subjected to a 56-day caries test regimen, using NIDR Diet 2000. All animals developed caries, although at widely different levels, when caged with their own kind throughout the test period. When animals of either strain were caged with an older caries-active rat for the first week on the test regimen, both the "susceptible" and the "resistant" animals developed higher levels of caries activity than their unexposed littermates. The level of caries activity of the exposed "resistant" rats was in the same general range as that of the unexposed "susceptible" animals. Under the test challenge to which these animals were subjected, both the Harvard "caries-susceptible" and the "caries-resistant" strains of rats developed higher and less-divergent levels of caries activity than had previously been reported.