Relationship between Thyroid Function and Resistance to Dental Caries

Abstract

Twenty groups of albino rats were fed: 1) a control diet, 2) this diet plus 0.05% propyl thlouracil, 3) the control diet plus 0.1% desiccated thryoid. Dental caries was increased by propyl thiouracil and decreased by desiccated thyroid. However, in the 2nd experiment with sialoadenectomized rats there was no difference in the caries rates. In the 3rd experiment, 20 pairs of intact and thyro-parathyroidectomized rats were fed the cariogenic diet. The removal of the thyro-parathyroid apparatus resulted in an increase in caries. pH readings on the teeth of the operated animals were slightly lower than that on the controls. The differences were statistically significant. The 4th experiment on 20 groups of animals showed that the administration of desiccated thyroid via stomach tube or in the food reduced caries to the same extent. In the 5th experiment in which KI was given in the food and in the drinking water, it was shown that 20 ppm I2 did not affect the caries rate. The results of these experiment support the idea expressed by other investigators that the thyroid-dental caries relationship is mediated by the salivary glands. Elucidation of the mechanisms involved awaits further investigation.