For the Zt samples, the increase in property is visible only for the strength, the toughness (at initiation or in Rcurves) not seeming to be affected. The strengthening by phase transformation being supposed to act on the Rcurve of the sample, we can assume here that this effect is minor and probably erased by the strengthening induced by the crack deflection. Finally, the introduction of residual stresses induced by the difference of thermal expansion between zirconia and alumina (respectively 7.2x10 -6 K -1 and 7.2x10 -6 K -1 ) may play an important role in the observed increase in strength of samples .