Mechanical characterization of dense calcium phosphate bioceramics with interconnected porosity.

Porous hydroxyapatite/tricalcium phosphate (HA/TCP) bioceramics were fabricated by a novel technique of vacuum impregnation of reticulated polymeric foams with ceramic slip. The samples had approximately 5-10% interconnected porosity and controlled pore sizes appropriate to allow bone ingrowth, combined with good mechanical properties. A range of polyurethane foams with 20, 30 and 45 pores per inch (ppi) were used as templates to produce samples for testing. The foams were inpregnated with solid loadings in the range of 60-140 wt%. The results indicated that the average apparent density of the HA/TCP samples was 2.48 g/cm(3), the four-point bending strength averaged 16.98 MPa, the work of fracture averaged 15.46 J/m(2) and the average compressive strength was 105.56 MPa. A range of mechanical properties resulted from the various combinations of different grades of PU foam and the solid loading of slips. The results indicated that it is possible to manufacture open pore HA/TCP bioceramics, with compressive strengths comparable to human bone, which could be of significant clinical interest.