Non-Oxide Ceramics

The current life expectancy for a successfully implanted hip joint can nowadays be approximately estimated to be 15 years. However, with the development of alternative low-wear bearings, achievement of longer lifetimes are hopefully expected. Non-oxide ceramics and particularly silicon nitride materials certainly exhibit better mechanical behavior as compared to oxide bio-ceramics, which would certainly represent a benefit, explicitly in terms of an improved safety factor. Besides the high fracture strength (comparable with that of composite oxides), the most appealing property is the high fracture toughness due to a microstructure containing elongated grains with a remarkable toughening effect due to crack bridging. Moreover, these engineered microstructures allow a very high reliability of Si3N4-based ceramics. With such interesting characteristics, one may wonder why non-oxide bulk ceramics were not widely used in orthopedics before.