Carvable calcium phosphate bone substitute material.

This study investigated the use of partially set hydroxyapatite forming calcium phosphate cement as a carvable and mechanically stable bone substitute material. Hydroxyapatite-forming cements were made of either mechanically activated alpha-tricalcium phosphate or a mixture of tetracalcium phosphate and dicalcium phosphate anhydrous and setting was arrested up to 4 h post setting. The study showed that these partially set rigid samples of defined geometry could be carved into a desired shape when the degree of reaction was 30-40% and the relative porosity between 40 and 50%; samples are then expected to set completely after implantation in the presence of water or serum, having the same compressive strength as a continuously set calcium phosphate cement (up to 36 MPa). The development of compressive strength, phase composition, and crystallinity when varying production parameters of these partially "preset" bone substitute materials are presented for both cement systems.