Hydroxyapatite dissolution rates in fluoride/dodecylamine solutions

Abstract

The influence of fluoride (F) alone and together with dodecylamine hydrochloride (DAC) on the dissolution rate behavior of hydroxyapatite (HAP) crystal suspensions has been studied. The results showed that F and DAC inhibit the dissolution in an additive rather than a synergistic manner. The data suggest that DAC inhibits dissolution from the predominant surface(s) by adsorption physically blocking the HAP surface while F inhibits the same surface by influencing the apparent driving force for dissolution. The existence of a residual component for the dissolution rate at high concentrations that is about 15% of the maximum rate suggests that there are two or more dissolution sites on the HAP crystal. The one associated with the predominant surface(s) is strongly inhibited by both F and DAC whereas the other site(s) is insensitive to F either intrinsically or, in the presence of DAC, because of possible antagonism.