5. Components for alumina-zirconia prostheses

The development of zirconia reached its limits due to –– problems of accelerated degradation. In response, new alumina-zirconia composites were developed (in the late 1990s). In this section, the main aspects of these composites - microstructure, mechanical properties and durability - are examined, and possible optimization paths are proposed.

The idea behind alumina-zirconia composites was to exploit the advantages of two materials: the hardness and chemical inertness of alumina, and the phase-transformation reinforcement of zirconia. The most common way of achieving this is to create a homogeneous dispersion of zirconia grains in an alumina matrix (this produces a material known as "ZTA" (Zirconia-Toughened Alumina ). A crack propagating in such a material causes the q-m transformation of the zirconia grains, and is therefore slowed down by the compressive stresses...