The effect of radioactive iodine on dental caries in the rat

Abstract

Experience in this laboratory has shown that the thyroid gland is related to the in­ cidence o f experimental dental caries in the albino rat. W hen desiccated thyroid is furnished as a component o f the diet, a significant reduction in the incidence o f dental caries results. Similarly, when thiouracil is added to the diet, a signifi­ cant increase is found in the incidence of dental caries.1 Furthermore, it has been shown by histologic observation that ad­ ministration of testosterone increases the activity o f the thyroid gland,2 and that testosterone and desiccated thyroid given together increase the anticariogenic effect o f desiccated thyroid alone.3 Evidence also suggests that certain his­ tologic changes o f the rat submaxillary gland parallel the activity o f the thyroid gland and the incidence o f dental caries.4 It is interesting that the thyroid glands in the caries-resistant and caries-susceptible strain of rats used by the Michigan State group show pronounced differences.5 R e­ cently, an explanation o f these observa­ tions has been offered by Ryan and Kirkwood.6 .Since thiouracil was used in previous studies1,3 to reduce the function o f the thyroid gland, it was o f interest to de­ termine if destruction o f the thyroid would result in a similar increase in dental caries. Because of the surgical difficulties o f thyroidectomy without con ­ comitant parathyroidectomy, the elimi­ nation o f the thyroid was accomplished by the administration of radioactive iodine ( I 131).