Influence of Dietary Calcium upon Composition of Mineralized Tissues and upon Susceptibility of Enamel to Erosion in Vivo

¹ Department of Chemistry, Douglass College, Rutgers University, New Brunswick, New Jersey

Six groups of littermate, weanling rats were provided for an 8 weeks' experimental period with a diet containing either 0.08 or 0.48 per cent of calcium and one of three fluids—water, or water replaced three times weekly with either canned orange juice or neutralized, canned orange juice.

The increase in dietary calcium, attended by an increase in molar Ca:P from 0.39 to 2.30, was accompanied by an increase in the percentage of calcium, magnesium, and carbonate ions in the tibia, by an increase in magnesium and phosphate ions in the dentin, and by an increase in magnesium and carbonate ions in the enamel. The only effect of the consumption of orange juice was the increase in magnesium level in dentin and enamel.

The presence of orange juice caused erosion of the enamel in vivo and to a greater extent with the low-calcium diet. The residual enamel had a higher content of magnesium and phosphorus and a higher ratio of Mg:P and of Mg:CO₃ than the enamel from the water-fed animals. There was a preferential retention of phosphate and carbonate ions, and the degree of erosion in individual enamels was found to be related inversely to the level of phosphate enamel. The less eroded enamels from the high-calcium diet had lower Ca:P, Ca:CO₃, and PO₄:2CO₃ ratios. Processes of calcification and remineralization appeared to be taking place in the molars during the 8 weeks of study.

The dietary ratio of Ca:P appeared to be the determining factor in the degree of susceptibility of enamel to erosion in vivo.