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The Influence of Dietary Factors upon the Composition of Mineralized Tissues and upon the Susceptibility of Enamel to Erosion in vivo

I. Phosphorus^1,2,

Department of Chemistry, Douglass College, Rutgers—The State University, New Brunswick, New Jersey

In a preliminary experiment the Sobel-Hanok diet supplemented with either a calcium or phosphate salt was fed in conjunction with water or water-cola to Sherman strain rats for 40 days. Erosion of the enamel layer occurred with the cola fluid and to a greater degree when using the phosphate supplemented diet. The levels of calcium and of phosphorus in the whole teeth were similar for all the diet-fluid combinations.

In a second experiment a highly purified diet containing either 0.09 or 0.25% of phosphorus was fed in conjunction with water, water and orange juice, or water and neutralized orange juice to Wistar-strain rats for 8 weeks. Irrespective of the fluid the following measurements were found at a higher level for the higher phosphate-containing diet: length and weight of tibia; weight of 6 lower molars; percentages of calcium, phosphorus and carbonate in the tibia; and percentage of calcium in the dentin. The level of carbonate in the dentin was lower for the higher phosphate diet. The composition of the enamel showed no differences for the two levels of dietary phosphate when water was the sole fluid.

When canned orange juice, pH 3.7 to 3.8, was provided as the fluid, erosion of the enamel layer occurred and to a greater extent on the higher phosphate diet. The carbonate content of the eroded enamel showed an inverse relationship with the extent of erosion but the Ca:P ratio remained unchanged. When neutralized orange juice was provided no erosion was observed but chemical changes occurred which were similar to, but not as marked, as the changes which occurred with untreated orange juice.

The level of carbonate in the eroded enamel was the result, and not the primary cause, of erosion. The Ca:P ratio, rather than the level of phosphorus, in the diet seemed to determine the degree of availability of carbonate ions for loss by erosion.

² Presented in part before the Annual Meeting of The American Institute of Nutrition, Atlantic City, New Jersey, 1959.

Manuscript received 13 May 1960.