(1) By means of apparatus devised by the author, salivas from parotid and mandibular glands can be collected simultaneously in separate containers. As the amounts, and chemical and physical properties, of saliva from the two sets of glands vary under different conditions, this separation has made more accurate study possible. (2) A complex, non-fermentable carbohydrate exists in salivary mucin—principally in mandibular saliva—the amount of which can be increased or decreased, in the author’s saliva, by increasing or decreasing the amount of carbohydrate in the diet. (3) The diastatic action of parotid and mandibular salivas varies on the contrasting diets, but follows the same general trends as the carbohydrate content of the salivas. (4) Numerous experiments have shown that the complex carbohydrate in saliva is hydrolyzed into fermentable sugar, in from three to four hours, by ptyalin in stagnant saliva—when fermentation by acidogenic bacteria is prevented.
Two types of enamel decalcification have been produced in vitro: (a) In the presence of adequate concentrations of H, Ca, and PO, ions in saliva, in which the surface of enamel remains intact, but decalcification of interprismatic substances occurs, with dissolution of CaCO3remineralization takes place with salivary calcium phosphate at the point of dissolution of the CaCO3, owing to decreased H-ion concentration at that point ; and (b) in the presence of adequate concentration of H ions, but inadequate concentration of Ca and PO, ions, in saliva—in which there is dissolution of enamel prisms and interprismatic substance, producing loss of surface continuity. Decalcification can be arrested in naturally decalcified areas of enamel (including white or opaque areas, with surface intact) by desiccation and application of solution of nitrocellulose. The nitrocellulose hardens in the impregnated decalcified area, this area then being insoluble in 10 percent lactic acid.
References: Den. Cosmos, 1935 ; J. Den. Res., 1938, 1939 (in press) ; J. Am. Den. Assoc., 1939.