Self-setting calcium phosphate cements (CPC) are promising materials which have a variety of possible medical and dental applications. In situ setting and biocompatibility properties make CPCs potentially useful as endodontic filling materials, as implants for bony defects, and as a binder for other implant materials. CPCs are formed by moistening biphasic mixtures of calcium phosphate salts, usually anhydrous dicalcium phosphate (DCPA) and tetracalcium phosphate (TTCP), with limited amounts of water. Although relatively simple materials in composition, other chemical as well as physical properties, e.g. setting times, porosity and strength, are dependent in a complex manner upon a number of poorly understood parameters associated with the chemistry of the setting process. The purpose of this project is to study factors which influence the conversion of the DCPA/TTCP mixture to apatite, the principal end product in the setting reaction. The principal endeavor currently being pursued is an examination of the hydrolysis of the DCPA component to apatite under controlled experimental conditions in order to obtain mechanistic information on the role of DCPA in the CPC setting reaction. Findings to date suggest that DCPA can initiate apatite formation by surface nucleation but that solution parameters such as pH and supersaturation control the time required to complete the conversion.
