The relation between endogenous and exogenous causes of caries (type of diet, L. acidophilus, etc.) is such that, in the presence of exogenous factors, dental surfaces that have been made defective by developmental disturbances are first attacked even when they are not included in locations where food lodgments occur.
Exceptionally high resistance to caries occurs in diabetic children. Even in children manifesting susceptibility to caries at the onset of diabetes, high caries- resistance develops. This cannot be due exclusively to low-carbohydrate content of the diet, since most of these children receive a normal mixed diet and insulin. Changes in metabolism, perhaps changes in salivary composition, seem to be influential factors. There is extreme destruction of deciduous teeth in children who receive, until their second year, a nipple or solacer dipped in sugar or honey.
Certain types of metabolic and alimentary disorders, during the period of tooth development, may cause defects in enamel calcification that later become sites for caries.
References: Wien. Med. Woch., 1934, 1935, 1936, 1938; Z. Stour., 1936, 1938; Wien. Klin. Woch., 1936; J. Den. Res., 1938, 1939.
STEPHAN, ROBERT M.: College of Dentistry, University of Illinois, Chicago, Ill. (Feb. 16, 1939).
The pH of dental plaques, and of debris from cavities, varies from 4.0 to 7.6. Within this pH range, variations may occur on different tooth surfaces in a mouth at one time, or on the same surface of a tooth at different times. The usual pH range of dental plaques is 5.0 to 7.0. After rinsing the mouth with carbohydrate solution (glucose, fructose, sucrose, maltose, cooked starch, but not lactose), the pH of plaques may fall as low as 4.0. This fall in pH may be almost immediate and lasts for 30 minutes to several hours.
References: J. Den. Res., 1938; J. Am. Den. Assoc. (in press).