In this work itria stabilized ZrO2 based ceramics for dental applications has been sintered and characterized in terms of physical and mechanical properties. Nanostructured blocks were sintered at 1400 0C and microstrutured blocks sintered at 1600 0C. Both nanostructured and microstructured materials were characterized in terms of densification, crystalline phases, mechanical properties and microstructure. Fracture toughness and four point bending strength were evaluated and compared. For the nanostructured zirconia, the reduced grain size allowed the increase of its toughening capacity, generated from maximization of volumetric fraction of retained tetragonal zirconia particles. For this material higher bending flexural strength is related to induced nucleation of microcracks, increase of energy absorption during crack propagation and developed compressive surface stress. The fracture toughness obtained at nanostructured samples sintered at 1400 0C is approximately 20% higher when compared to microstrucutured samples. These results represent the toughening ability of nanostructured zirconia, originated from higher amount of retained tetragonal phase and grain boundary microcracks. The higher Weibull moduli in this case are indicative of material reliability improvement and these results are correlated to grain size and its influence at mechanical strength.