Silicon Nitride Biocomposites

This chapter addresses silicon nitride composites with an emphasis on biomedical applications. Beyond its use as a bulk ceramic, silicon nitride can be added to other materials, such as low-melting-point metals. However, metal–ceramic matrix composites are limited by nitrogen release at higher melting points. Laser-cladding of silicon nitride onto metal and nonmetal surfaces may overcome these limitations. Silicon nitride is also suitable as an additive for a variety of polymeric matrices, some of which are amenable to 3D printing. Mechanical properties of ceramic–polymer matrices generally improve up to 10–15 vol.% addition of silicon nitride and then decline. Regardless of approach, these composites and coatings retain silicon nitride’s bioactivity in terms of bone formation and antibacterial properties. Combining silicon nitride with bioglass, hydroxyapatite, or the surface treatment of zirconia-toughened alumina leads to similar findings, especially in terms of the osteogenic behavior of the resulting matrices. Ceramic matrix composites containing silicon nitride show strength, thermal stability, and chemical resistance. These properties are desirable in industrial applications, but they have added value and importance in bone tissue engineering. Inert, biocompatible structural polymers such as PMMA, PEEK, polyethylene, and polypropylene can be functionalized with fractions of silicon nitride. The composites stimulate bone cell activity and demonstrate antibacterial and antiviral attributes, as long as the surface maximization of silicon nitride particles is ensured. Silicon nitride polymer composites are promising candidates for medical materials with desired mechanical strength, wear resistance, stimulation of bone growth and integration, and microbial resistance. These materials will be suitable for dentistry, orthopedics, and tissue engineering scaffolds.