A possible second site for hydroxyapatite dissolution in acidic media

Dissolution of human dental enamel and of synthetic hydroxyapatite pellets in completely unsaturated acetate buffer solutions was previously shown to follow a model in which a single dissolution site was employed. The present investigation reports similar studies carried out under the clinically more relevant conditions of dissolution into solutions partially saturated with respect to hydroxyapatite, and it is shown that under these conditions the dissolution kinetics may be described by a site which has properties different from the site responsible for dissolution into completely unsaturated solutions. The properties of this second site were consistent with experiments in which bulk solution conditions (degree of partial saturation, Ca/P ratio) and effective diffusion layer thickness were varied. Thus, dissolution kinetics studies indicate that hydroxyapatite crystals have at least two different types of sites that are important in dissolution.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22733/1/0000288.pd