Bioinert Ceramics: State-of-the-Art

Abstract

Bioinert ceramics in use today are the result of more than 60 years of continuous development. Early studies were concentrated on alumina that in the late 1960s was the most advanced ceramic, and on pyrolytic carbon. After tests in orthopedic bearings, pyrolytic carbon found clinical applications in artificial heart valves, where it is in clinical use so far. After 1970 zirconia-toughened ceramics (YTZP, ZTA, ATZ) were investigated in view of their use as biomaterials in orthopedics. Especially the introduction of YTZP in clinics in the 1990s gave a new momentum to the use of inert bioceramics. So far, zirconia-toughened ceramics are replacing alumina because of their outstanding mechanical properties leading to high reliability in ceramic components. The behavior of ZTAs and ATZs are exploited in several innovative devices. Especially metal-free devices are of interest, because of the increasing number of patients sensitized to metals. Using zirconia-toughened ceramics were achieved remarkable development in ceramic knee replacements, a field pioneered by Japanese researchers, because the behavior of these materials allow the production of devices similar in size to the metallic ones. In dentistry, a number of manufacturers are marketing metal-free dental implants, as well as machinable zirconia blanks for the production of crowns, bridges, copings by CAD/CAM. Besides oxides, that in todays’ orthopedics and dentistry are the state-of-the-art bioinert ceramics, silicon nitride has found application in spinal surgery, and investigations in view of its use in joint replacement bearings are in progress.