Calcium Phosphate Mineralization

Although it is often assumed that the thermodynamically most stable hydroxyapatite is a suitable prototype for biological minerals, it is now generally accepted that other phases such as dicalcium phosphate dihydrate and octacalcium phosphate as well as defect apatites and carbonated apatites may participate. The Constant Composition kinetics method, has been used to show that defect apatites may be formed with non-stoichiometric coefficients that depend upon the pH of the growth medium. Important factors in analyzing these experiments are the initial surface modification and ion exchange processes involving hydrogen and calcium ions following inoculation of the supersaturated solutions. Proteins and other macromolecules which may inhibit the rate of growth of calcium phosphates in supersaturated solutions are able to enhance the nucleation of these phases when immobilized on inert surfaces.