Studies of (a) teeth of school children previously examined for rickets (1934), (b) dental changes in Pueblo Indian children (1937), (c) caries in monkeys (1937), and (d) changes in rats on a diet low in organic salts (1935), yielded the findings and conclusions stated below : (a) Enamel hypoplasia of permanent teeth in school children (especially the type characterized by symmetrical distribution of defects in teeth formed during infancy and early childhood) is frequently associated with rickets. The more severe the rachitic process, the more frequently hypoplastic defects develop. When severe hypoplasia occurred, a definite history of moderate or severe rickets was established by roentgenologic evidence in practically all cases. Increased incidence of caries occurred in children having known histories of rickets; but, since caries was found more often in teeth having hypoplastic defects than in those having none, these defects may account for the increased caries. Administration of antirachitic therapy in infancy reduced incidence of enamel hypoplasia and also, to some extent, lessened incidence of caries. (b) Of 204 Pueblo Indian children, 13 percent were free from caries; 64.2 percent had no caries in permanent teeth. Of 811 permanent first molars, 114 (12.7 percent) were carious; 206 (24.1 percent) had white spots in enamel. No carious lesions were observed in any of 1,605 permanent incisors, but 24 percent of these teeth had white spots in enamel. These observations add another recorded group of teeth in which, although structurally defective, incidence of caries was not increased.
(c) Carious lesions in monkeys are similar to, or identical with, those in man. Of a colony of 76 monkeys (Macaca mulatta), 25 had deciduous, 22 permanent, and 29 mixed dentitions ; only 3 had caries. (d) Carious lesions, in pits or other sites, occurred in upper right third molars of rats—on adequate diets, and on low- salt synthetic-diets that passed a 60-mesh screen, from the time each animal attained a weight of 100 grams until death. From weaning until each attained a weight of 100 grams they were fed stock diet that had not been sifted. The rats attained 100 grams in weight at ages ranging from 33 to 38 days ; the third molars began to erupt during this period. Carious lesions occurred on cusps of lower right first and second molar teeth in rats from which the upper right first and second molars had been removed at weaning (approximately 22 days of age). These teeth had no antagonists, fractures did not occur, and the cusps were not abraded. The etiology of the carious lesions was not determined. (Serial sections containing enamel remains were found to be necessary to differentiate accurately the origin and site of all carious lesions in rat teeth.)
References: Am. J. Dis. Child. (with M. M. Eliot, S. P. Souther, and B. G. Anderson), 1934; J. Am. Den. Assoc. (with S. D. Aberle and E. H. Pitney), 1937;
Yale J. Biol. Med. (with B. G. Anderson), 1937; Dental changes in rats consuming a diet low in inorganic salts, Ph.D. dissertation, Yale University, 1935.