672 X. VITAMINS D 



proportions of 10% and 15% of the daily ration has been reported to have 

 an antirachitic effect/ injections of citrate were found by Nicolaysen and 

 Nordb0^-'' to be entirely ineffective in such cases. The positive effect of 

 oral doses is probably to be ascril^ed to the formation of a soluble complex 

 with calcium in the intestine. The most recent review of vitamin D and 

 its relation to bone is that of Harris. ^^'^ 



(5) Vitamin D and the Formation of Teeth 



According to the classical work of Mellanby and Ejng/-^ vitamin D 

 functions in the metabolism of enamel. The development of enamel 

 hypoplasia as a result of \atamin D deficiency has been demonstrated.^ 

 Moreover, the fat-soluble \dtamins were shown to be concerned with the 

 formation of secondary dentine. These results were established from a 

 study of the structural relations of the teeth of children and from experi- 

 mental work with dogs.^ 



The relation between the growth of the tooth and the presence of vita- 

 min D has been followed, and the tooth has been shown to require vitamin 

 D just as is the case with bone. According to Ir\'ing,'-^'^'^ who studied 

 the growth of teeth in rats from the histologic standpoint, the nature of 

 the change differs with the Ca:P ratio in the diet and with dietary vitamin 

 D. Following the administration of a good Ca :P diet without vitamin D, 

 spherulities were precipitated in the predentin area which varied greatly 

 in size and character from the finely granulated precipitate produced on 

 the same diet "with vitamin D. The incisor teeth of rats were shown by 

 sodium fluoride injections to be a center of high activity. This tooth 

 provided a very sensitive measure of latamin D deficiency. 



There also appears to be some relationship between dental decaj^ (caries) 

 and vitamin D level. Thus, Mellanby and Mellanby^-^ demonstrated 

 that a relationship exists between hypoplasia in the tooth and the develop- 

 ment of caries. However, the dietary regimen employed appears to be of 

 considerable importance. Marshall-Day^" noted the presence of marked 

 hypoplasia in the teeth of Indian children, while the incidence of caries 

 was extremely low. Rickets is frequently associated with caries. The 

 dietary factor is important. -^^ Vitamin D, by promoting adequate cal- 

 cification of the teeth, insures a normal "dental architecture" and reduces 

 the tendency to caries.^" 



323 M. Mellanby and J. D. King, Ergeb. Vitamin- \i. Hormonforsch., 2, 1-54 (1939). 



324 J. T. Irving.V. Physiol., 103, 9-26 (1944). 



326 J. T. Irving, /. Physiol., 104, 253-265 (1946). 



326 M. Mellanby and H. Mellanby, Brit. Med. J., 1948, II, 409-413. 



32' C. D. Marshall-Dav, Brit. Dent. J., ser. 2, 76, 115-122, 143-147 (1944). 



