Fabrication of three different types of porous carbonate-substituted apatite ceramics for artificial bone

The purposes of this study were to fabricate porous carbonate-substituted apatite (CAp) ceramics and characterize important properties such as compressive strengths and dissolution rates for an artificial bone. Porous A-type CAp (A-CAp) with uniaxial pores was fabricated by sintering porous hydroxyapatite green bodies at 1000°C in carbon dioxide gas atmosphere. B-type CAp (B-CAp) nanocrystals prepared by a wet method were mixed with an organic binder, freeze-dried and heated at 800°C in air, and AB-type CAp (AB-CAp) was fabricated by heating B-CAp porous bodies including the organic binder at 1100°C in carbon dioxide gas atmosphere. From the morphological observations with a scanning electron microscope, the porous A-CAp had uniaxially oriented pores of 104±33 μm in diameter, while the porous B-CAp and AB-CAp had large pores of 143±48 μm and 181±46 μm in diameter, of which pores were interconnected with small pores of 31±11 μm and 45±17 μm in diameter. The dissolution rates of CAps were apparently larger than that of HAp; the calcium concentrations increased in the order of AB-CAp > B-CAp > A-CAp > HAp. This is mainly attributed to carbonate content although it could be partialy depended on the different porous structures and diameters.