Effect of Dietary Phosphate Supplements on Dental Caries in the Rat

¹ Dental Division, Naval Medical Research Institute, National Naval Medical Center, Bethesda, Maryland

Studies were made of the effect of various dietary phosphates on the occurrence of dental caries in the NMRI-D strain of rat. Two experiments were performed. In Experiment 1, it was found that the addition of either CaHPO₄ or Na₂HPO₄ to a purified diet resulted in fewer carious teeth, fewer carious lesions, and a tendency for the lesions to be less severe than in the unsupplemented control rats. In Experiment 2, the results with Na₂HPO₄ were confirmed, and it was found that (NH₄)₂HP0₄ was also an effective cariostatic agent when added to the diet at a level equivalent to the sodium salt. On the other hand, it was demonstrated that Na₄P₂O₇ and Na₅P₃O₁₀ were not effective under our experimental conditions.

Titration curves, of aqueous preparations of the various phosphates, showed that sodium pyrophosphate had the highest pH in solution, and after reaching a pH of about 6.5, it titrated very similarly to sodium or ammonium phosphate. If the buffering capacity of the various phosphate compounds is the only mechanism of caries reduction, sodium pyrophosphate would be expected to be effective; since it was not, some possible reasons for this were discussed.