The purpose of the present study was to evaluate the effect of Al2O3 content on the fracture property of all-ceramics ZrO2. To improve the all-ceramics ZrO2 restoration mechanics properity ,96 samples containing 0,5,10 and 15 wt% of Al2O3 particles were prepared by cold isostatic pressing (200 MPa) and 1 550 ℃ sintered .The phase was analyzed by X-ray diffraction analysis and the bulk densities of the samples were made using Archimedes principle. Samples were randomly divided into four groups. In each group, 24 specimens were prepared so that the angle between notch and specimen's long axis is 90o and 60o. Notch depths were 1 mm for all samples. Samples were loaded with three-point bending method. 90° cut samples were used to measure fracture toughness while 60°cut samples were used to observe fracture curve by taking points on the fracture extension path under microscope, plotting points on coordinates, generating fitting curve by software 'Origin', and analyzing the microstructure of the specimen fracture surfaces by scanning electron microscopy (SEM).The results show that the increment of Al2O3 has insignificant effect on the densification of all-ceramic ZrO2.XRD analysis shows that the specimen is comprised of t-ZrO2 and α- Al2O3 before fracture while fracture surface is m-ZrO2, t-ZrO2 and a-Al2O3. ZrO2 containing 10% Al2O3 has the optimum mechanical properties and unconspicuous crack propagation and distribution. The observations may provide a reference for the materials selection, shape design , and production process of all-ceramic crown and bridge.
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