To evaluate the effect of grinding and sandblasting on the microstructure and flexural strength of partially sintered yttria stabilized tetragonal zirconia polycrystals (Y-TZP) ceramic, 60 bars from each material were randomly divided into four groups of fifteen. For each group, a different surface treatment was applied: grinding, sandblasting and grinding + sandblasting, and a control group. The flexural strength and Knoop microhardness were determined and data were analyzed using one-way

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... sis of variance (ANOVA) (F = 38.962, P<0.001), followed by Tukey's honestly significant difference (HSD) test (p<0.05).The phase composition was assessed by X-ray diffraction (XRD). In flexural strength, statistically significant differences (p<0.05) were found between the as-sintered group (901.49±33.42 MP) and other group materials. However, no significant difference was found between the ground group (1168.16±90.01 MP) and the sandblast group (1120.11±50.1 MP). There were statistically significant differences between the ground + sandblast group (1260.59±77.2 MP) and other groups (p<0.05). In Knoop microhardness, no significant difference (P>0.05) was identified between groups. Results indicate that the ground of partially sintered Y-TZP ceramic may provide a powerful technique to strengthen Y-TZP in clinical practice. Sandblasting of surfaces is recommended to increase the strength of dental Y-TZP.