Zirconia presents good esthetic aspects after polishing. It is inert in physiological
environments and presents greater flexural resistance, toughness, and lower Young’s
modulus when compared with pure alumina [12]. The ability o f Y-TZP to transform
from a tetragonal crystalline structure to a more voluminous monoclinic structure,
and thus obstruct crack propagation, gives the material its strength and toughness.
The addition of zirconia to the alumina as a sintering additive has been used for a
long time for the densification o f the alumina based ceramic. However, the concept
o f toughening alumina ceramics by dispersion o f zirconia particles in the matrix was
only recognised in the last 2 0 years [13].