Setting, hardening and resorption of calcium phosphate hydraulic cements.

Two examples of calcium phosphate hydraulic cements (CPHC) are presented. Type I cements consist in mixtures of beta-tricalcium phosphate (beta-TCP) and monocalcium phosphate monohydrate (MCPM), to which some plaster of Paris (CSH) is added as a setting retardant. Type II cements consist in mixtures of beta-TCP, dicalcium phosphate dihydrate (DCPD) and calcium carbonate (CC), to which some hydroxyapatite (HAP) is added as a setting accelerator. The setting time of these cements ranges from a few minutes up to a few hours, according to their composition and the amount of mixing water. Tensile strengths ranging from 1.2 up to 3.5 MPa have been recorded on cements which porosity ranged from 38 up to 55 vol%. In-vivo experiments on dogs have shown the perfect biocompatibility and resorbability of cement I.