Formation of hydroxyapatite in cement systems

Self-setting calcium phosphate cements (CPC) have been a subject of considerable interest in recent years. These materials contain only calcium phosphates, have neutral pH, and form hydroxyapatite (OHAp) as the end product. As a result, the cements were found to be highly biocompatible and osteoconductive. Since CPC also sets to a hard mass at the site of application, it has been shown in experimental studies to be highly useful in a wide range of dental and medical procedures. ^1-10 Among the self-setting calcium phosphate cement systems, those cements that consist of tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) or dicalcium phosphate dihydrate (DCPD) form OHAp as the only reaction product. ^11-13 The chemistry of reactions between TTCP and DCPA or DCPD have been studied extensively. ^11-23 This paper reports the effects of several additional factors on the formation of OHAp in the TTCP + DCPA system. Also described is the formation of OHAp in new cement compositions comprising TTCP and a-tricalcium phosphate (α-TCP), octacalcium phosphate (OCP), amorphous calcium phosphate (ACP), or monocalcium phosphate monohydrate (MCPM).