Mechanisms of hydration of calcium phosphate cement

Calcium Phosphate Cement (CPC) is a new kind of bone repair material. The mechanism of hydration of CPC was studied and some results were obtained. The hydration of CPC is based on the differences of solubility, of calcium phosphate salts. HAP is the least soluble phase when pH>4.2, so other calcium phosphate salts can dissolve and reprecipitate as HAP when suspended in an aquenous solution; when CPC is comprised of two kinds of calcium phosphate salts with different basicity or acidity, the pH value of the system will become stable by the neutralizing reaction of acidic and basic byproducts, so the promotion of hydration is maintained and the reacion can proceed to completion. The kinetics of hydration of CPC which consists of tetracalcium phosphate (TECP) and dicalcium phosphate anhydrous (DCPA) is initially controlled by the surface dissolution of DCPA, and eventually controlled by the rate of diffusion through the product layers.