SIMULTANEOUS CARIES INDUCTION AND CALCULUS FORMATION IN RATS

Weanling specific pathogen-free Osborne-Mendel rats were fed a high-ca lcium, high-phosphorus diet with various levels of sucrose and inocula ted with Streptococcus sobrinus strain 6715-13WT and Actinomyces visco sus strain OMZ-105 in order to determine whether calculus and caries c ould develop simultaneously. Rats consumed diets designated RC-16-5, R C-16-25, or RC-16-50 which partially replaced the corn starch componen t with progressively higher levels of sucrose, thus, to 5, 25, or 50% sucrose. In general, bacterial recoveries of A. viscosus declined with higher sucrose content of the diet, but a pattern of recovery for S. sobrinus was less clear with respect to dietary sucrose. S. sobrinus, however, was recovered at higher percentages from the tooth surface fl ora at the later two of three sampling dates. Most calculus-identified by the brittle quality, staining characteristics, and apatitic x-ray diffraction patterns of tooth surface deposits-was formed on the maxil lary molars, and most carious lesions occurred on mandibular molars. W hile there was minimal association of the calculus score with the amou nt of sucrose in the diet, calculus scores increased greatly from 23 t o 43 days after infectious challenge. Caries scores, of both fissure a nd smooth surfaces, by contrast, increased in a dose-response fashion with increasing dietary sucrose and with time. It is thus possible to induce calculus formation and caries simultaneously in specific pathog en-free Osborne-Mendel rats consuming a high-calcium and -phosphorus d iet conducive to calculus formation and containing sucrose. This model appears to be well-suited for simultaneous evaluation of the putative calculus-inhibitory and caries-inhibitory effects of oral therapeutic agents.