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

¹ Indiana University, Bloomington, Ind.

Previous experiments have shown that the ingestion of a cariogenic diet containing desiccated thyroid will significantly reduce the incidence of dental caries in the rat. In this experiment the importance of the amount of food consumed daily by rats on such a regime was considered. Under ad libitum feeding conditions, desiccated thyroid added to a cariogenic diet significantly reduced the dental caries incidence when compared to a control group receiving the same diet without thyroid. When control animals receiving a nonthyroid-containing cariogenic diet were pair-fed with animals receiving the same diet to which desiccated thyroid had been added, the thyroid-fed animals again demonstrated a significant decrease in caries incidence. These results indicate that differences in food consumption which may result between experimental groups is not an important factor in explaining the anticariogenic action of desiccated thyroid.

In addition, the injection of sodium fluoride to animals receiving desiccated thyroid produced no synergistic anticariogenic effect. This result suggests that the anticariogenic synergism observed when the fluoride is given in the drinking water or in the diet is probably a result of the topical effect of the fluoride ion.