Clinical study indicates that caries, of which there are several varieties, is distinctly a disease of childhood, being almost universal among children. Marked reduction in progress of caries has followed dietary correction. Many teeth in which deep caries was treated with zinc oxide, and silver reduction, have shown that hardening of the cavity bottom occurs through deposition of secondary dentin. Teeth differ greatly ‘in the quality of their organic substance, and their structure is a major factor in resistance to caries. Lactobacilli of the alimentary tract, by overgrowing pernicious types in mouth and intestine, are protective microorganisms, and constitute the predominating flora in the mouths of nurslings. When the carious mass in a cavity is sealed-in, the organisms are changed to an almost pure culture of acidogenic type ; but they die, if the cavity is not too deep and is kept sealed long enough. Attempts, with such residual organisms, to produce caries in rats, guinea pigs, and monkeys, were unsuccessful in experiments lasting for a year. Caries developed among monkeys on inadequate diets, although it could not be ascribed to deficiency of any one food factor.
In eight Macacus rhesus monkeys, fed adhesive balls of sugar twice daily for eight months, no caries was observed. Caries could not be produced in monkeys with acidogenic microorganisms, although such organisms belong to the natural flora of this animal.
Reference: J. Med. Res., 36, 481, 1917.