Dietary phosphate supplementation and its effects on dental caries and salivary and serum concentrations of calcium and inorganic phosphate in the rat

Abstract

An attempt has been made to determine the mechanism whereby dietary phosphate supplements act to reduce the incidence of caries in rats. Experiments were also done to determine the influence of weight, sex and rate of flow on the concentrations of calcium, inorganic phosphate and bicarbonate in pilocarpine-stimulated saliva from rats of the Harvard caries-susceptible strain. Bicarbonate was found to be the main buffer in rat saliva. The rate of salivary flow was higher in males than females. Saliva from female rats contained a higher concentration of inorganic phosphate than saliva from males and the concentration was independent of flow rate. Salivary calcium concentration was independent of sex but increased at higher flow rates. For the phosphate feeding experiment, eighty-one rats were divided into three groups of which Group 1 received a cariogenic diet alone while Groups 2 and 3 received supplements of 2% Na 2HPO 4 and 2·2% commercial Na phytate, respectively. Groups 2 and 3 had a reduced incidence of caries. By elimination, a direct effect of phosphate on the teeth is postulated as serum and salivary calcium and inorganic phosphate analyses did not differ significantly among the three groups.