Objective: To determine the influence of different ion exchange temperatures on biaxial flexural strength (σ), hardness (H) and fracture toughness (K_IC) of a feldspathic ceramic (UltrapalineST, Jen Dental, Ukraine). Methods: 40 disk-shaped ceramic specimens (12mm diameter X 1mm thick) were fabricated according to the manufacturer's instructions and ISO6872 specifications. Specimens were polished through 1μm, divided in four groups (n=10) and submitted to an ion exchange procedure using KNO₃ paste as follows: I – control (no ion exchange); II – 450°C/15min; III – 470°C/15min; and IV – 490°C/15min. The σ was determined using a piston-on-three-balls device, in artificial saliva at 37°C and constant loading rate of 10 MPa/s. The following was used σ=[3P(1+υ)/4πt²]{1+2ln(R_a/b)+[(1-υ)/(1+υ)][1-(b²/2R_a²)](R_a²/R²)}, where P is the applied load (N), t is the disk thickness, υ is Poisson ratio, b is radius of contact area between the ball and disk, R is the disk radius and R_a is the ball radius. For H and K_IC, 3 Vickers indentations (2kg, 30s) were made on each specimen. The diagonals (2a, in μm) and radial cracks (2c, in μm) were measured in order to calculate H and K_Ic according to H=0.5(P/a²) and K_IC=0.028(E/H)^1/2Ha^1/2(c/a)^-3/2, where and E is the Young's modulus (74.4 GPa). Results were analyzed with one-way ANOVA and Tukey's test. Results: Mean and standard deviations values of σ (MPa), H (GPa) and K_IC (MPa.m^1/2) were: I: 57.95±8.97, 7.24±0.79, 1.14±0.14; II: 125.04±23.58, 5.80±0.14, 2.62±0.14; III: 133.00±11.00, 5.88±0.45, 2.54±0.22; IV: 137.67±12.05, 5.88±0.17, 2.57±0.10; respectively. Mean values of Group I were significantly different from those of all other groups for all three properties (p≤0.05), which were not statistically different from each other (p>0.05). Conclusion: Different ion exchange temperatures did not influence the ceramic properties studied. The ion exchange process increased the mean σ and K_IC values of the material studied. Acknowledgements: FAPESP, CAPES and CNPQ. 

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