Changes in the Structure of the Developing Tooth in Rats Maintained on a Diet Deficient in Vitamin A *

It has been shown that diets completely deficient in vitamin A influence the growing incisor teeth of animals. Both Shibata9 and Simola'0 described changes occurring in most of the tooth structures and particularly in the odontoblasts and pulp cells. Wolbach and Howell showed, however, that the effect of this diet is chiefly on the enamel organ of the incisor tooth of rats and guinea-pigs, with secondary involvement of the odontoblasts. Gross and histological changes in the molar teeth have been described by Marshal' and by Mellanby' in animals fed a diet deficient in vitamin A. None of these investigators has dealt with the effects of a chronic type of vitamin-A deficiency on the teeth and other tissues. The difficulties encountered in producing and in maintaining a chronic deficiency are many; nevertheless, it has been possible to maintain rats for a year in a state of known chronic vitamin-A deficiency by feeding minimal quantities of vitamin A. The gross changes that were found to develop in the incisor teeth of the older rats while on this diet were bizarre and unusual. It is our purpose, therefore, to describe the sequence of the gross and histological changes found in the incisor and molar teeth of these rats and to compare them with those occurring in normal rats and in the animals fed a diet completely deficient in vitamin A.