A new porous hydroxyapatite ceramic prepared by cold isostatic pressing and sintering synthesized flaky powder.

A new porous hydroxyapatite ceramic was prepared by cold isostatic pressing and sintering of the flaky powder, that was synthesized through two-stage hydrolysis of brushite; (1) a structural change into the apatite structure and (2) a compositional increase in Ca/P ratio, according to the method of Monma and Kamiya. The appearance of the synthesized powder resembled the flaky shape of the starting materials and its average particle size was about 15 microns. This powder consisted of fine needle crystals, which had a tendency to grow into the larger grains, but the powder was highly resistant to sintering under the usual heating conditions at 1200 degrees C. Porous hydroxyapatite blocks and granules were prepared by cold isostatic pressing and sintering a pellet consisting of the hydroxyapatite powder and spherical polymer beads. The product showed a 70% apparent porosity with spherical pores, ranging from 100-200 microns in size, and most pores were interconnected. These properties were ascribed to the effect of cold isostatic pressing on the hydroxyapatite powders with the flaky shape.