Effect of Carbonate and Fluoride on the Dissolution Behaviour of Synthetic Apatites

Abstract

The initial rates of dissolution of synthetic apatites were determined using the rotating disc method. The reactivities of carbonated apatites in acidic media were directly related to their carbonate content. This appeared to be due, in part, to a decrease in the apparent activation energy for dissolution of carbonated apatites. Structurally incorporated fluoride in carbonated apatites at levels up to 1,000 μg/g did not influence the dissolution rates, whereas fluoride at a concentration of 1 μg/ml in the buffer solution reduced the dissolution rates by 20–30%. Apatite dissolution under the experimental conditions was intermediate between transport control and surface chemical control. After 10 min, diffusion processes within the apatite pellets were found to influence the overall dissolution rate.