Studies of solubility of enamel in various buffer solutions indicate that the rate is proportional to the pH of the solution and to the quantities of contained Ca” and if no insoluble salt is formed. The Ca and PO, ions in saliva exert protective action by preventing dissolution of enamel within the usual variations in concentration of salivary H-ions. Individual specimens of enamel do not differ in rate of solution, suggesting that susceptibility or immunity to caries is not dependent upon differences in composition of enamel, and is not influenced by the age or physical condition of the patient. Chemical studies of the amount of lactic acid in carious dentin, by a modification of the Friedemann, Cotonio and Schaffer method, indicate that its concentration may approximate 0.01 N.
References: J. Den Res., 12, 277, 1932; 14, 21, 1934.