THE RELATION OF THYROID GLAND ACTIVITY TO THE INCIDENCE OF DENTAL CARIES IN THE RAT II. A COMPARISON OF CARIES INCIDENCE UNDER PAIRED-FEEDING TECHNICS

THE AMOUNT of cariogenic diet eaten by a rat has been shown to be re-Ilated to the incidence of dental caries.1 In our studies concerning the role of the thyroid gland and dental caries in the rat, the problem of food inges-tion was of interest, since there may be major differences in the amount of cariogenic diet consumed by rats receiving desiccated thyroid as compared to controls, thus resulting in an altered caries experience not due primarily to the administration of thyroid supplements. In order to evaluate this im-portant variable, the present study was conducted in which rats not receiving desiccated thyroid in the diet were pair-fed to similar rats receiving the same diet with desiccated thyroid. EXPERIMENTAL A total of 100 weanling male Sprague-Dawley rats were equally divided as to initial body weight into 4 experimental groups. Group 1 was fed desic-cated thyroid in the diet in increasing concentrations (5 to 15 mg. per cent), depending upon the growth of the animals. The animals in Group 2 were fe