RESUMEN
<p><b>OBJECTIVE</b>To investigate the mechanical properties and microstructure of nano -zirconia toughened alumina ceramics with variety of nano-zirconia content in centrifugal infiltrate casting processing of dental all-ceramic.</p><p><b>METHODS</b>Composite powder with different ethanol-water ratio, obtained serosity from ball milling and centrifugal infiltrate cast processing of green, then sintered at 1 450 degrees C for 8 h. The physical and mechanical properties of the sintered sample after milling and polishing were tested. Microstructures of the surface and fracture of the sintered sample were investigated by SEM.</p><p><b>RESULTS</b>The experimental results showed that there had statistical significience (P < 0.01) on static three-point flexure strength and Vickers Hardness in three kinds of different nano-zirconia content sintered sample. Fracture toughness of 20% group was different from other two groups, while 10% group had not difference from 30% group (P < 0.05). The mechanical properties of this ceramic with 20% nano-zirconia was the best of the three, the static three-point flexure strength was (433 +/- 19) MPa and fracture toughness was (7.50 +/- 0.56) MPa x min 1/2. The intra/inter structure, fracture of intragranular and intergranular on the surface and fracture of sintered sample in microstrucre was also found.</p><p><b>CONCLUSION</b>Intra/inter structure has strengthen toughness in ceramics. It has better toughness with 20% nano-zirconia, is suitable dental all-ceramic restoratives.</p>