Manufacture of macroporous calcium hydroxyapatite bioceramics

Trabecular bones of almost all vertebrate organisms basically consist of macroporous (55-70% interconnected porosity) bone mineral, i.e. calcium hydroxyapatite (HA: Ca-10(PO4)(6)(OH)(2)). The macroporosity observed in the trabecular bones then allows the ingrowth of the soft tissues and organic cells into the bone matrix. Sub-micron, chemically uniform, and high phase-purity HA powders produced in our laboratory were mixed, under vigorous ultrasonification, with methyl cellulose of appropriate amounts in the form of an aqueous slurry of proper viscosity and thickness. The ceramic cakes produced in this way were then slowly dried in an oven in the temperature range of 50-90 degrees C. Dried cakes of porous HA were physically cut into various prismatic shapes. These parts were then slowly heated in an air atmosphere to the optimum sintering temperature of 1250 degrees C. The HA bioceramic parts obtained by this novel 'foaming technique' were found to have tractable and controllable interconnected porosity in the range of 60-90%, with typical pore sizes ranging from 100-250 microns. Sample characterization was mainly achieved by scanning electron microscopy (SEM) studies and three-point bending tests