Objectives: The aim of this study tried to find an appropriate addition of mullite to modify zirconia in order to improve the shortcomings of zirconia for clinical applications. Methods: 10%, 20%, 30%, 40%, 50% (on weight basis) mullite modified zirconia (MDZ) were fabricated.The hardness, fracture toughness and elastic modulus were tested on specimens prepared through respective methods. Results: The flexural strength, hardness and elastic modulus of these five groups decreased with an increase in the percentage of mullite, which may be ascribed to the increasing presence of a glassy phase. The fracture toughness of the 30% mullite content showed a similar result with the 10% group. Conclusions: In general, an increase in the content of mullite is accompanied with a decrease of the strength and fracture toughness. The MDZ with a 10% content of mullite presents better mechanical properties and a better comprehensive clinical performance may be expected from.

Keywords: Mullite, 3Y-TZP, Fracture toughness, Flexural strength, Elastic Modulus, Crystalline phase.