Porous silicon nitride ceramics designed for bone substitute applications

Abstract Porous silicon nitride ceramics having properties similar to the human trabecular bone have been sintered and characterized in order to develop a material applicable as bone substitute. At first, human trabecular bone was characterized especially in terms of pore structure which is, besides the non-toxicity, the most critical for acceptation of the substitute. The pore network of highly porous trabecular bone is formed by interconnected large pores of approximately 300–1000 μm. Similar pore structure of silicon nitride-based ceramics was attained by the replica method with polyurethane sponge as pore forming agent. Porous ceramics were prepared in two ways, namely as air-sintered silicon nitride and sintered reaction-bonded silicon nitride. The materials were characterized using the same methods as for the human bone samples. Both types of ceramic materials fulfilled the microstructural requirements for bioapplications. Moreover, their non-cytotoxicity was proved by measuring the yellow tetrazolium MTT proliferation assay using human fibroblast cell line.