Effect of mechanical cycling on the flexural strength of densely sintered ceramics.

OBJECTIVES: The aim of this study was to evaluate the effect of mechanical cycling on the biaxial flexural strength of two densely sintered ceramic materials. METHODS: Disc shaped zirconia (In-Ceram Zirconia) and high alumina (Procera AllCeram) ceramic specimens (diameter: 15 mm and thickness: 1.2 mm) were fabricated according to the manufacturers' instructions. The specimens from each ceramic material (N=40, n=10/per group) were tested for flexural strength either with or without being subjected to mechanical cycling (20,000 cycles under 50 N load, immersion in distilled water at 37 degrees C) in a universal testing machine (1 mm/min). Data were statistically analyzed using two-way ANOVA and Tukey's test (alpha=0.05). RESULTS: High alumina ceramic specimens revealed significantly higher flexural strength values without and with mechanical cycling (647+/-48 and 630+/-43 MPa, respectively) than those of zirconia ceramic (497+/-35 and 458+/-53 MPa, respectively) (p<0.05). Mechanical cycling for 20,000 times under 50 N decreased the flexural strength values for both high alumina and zirconia ceramic but it was not statistically significant (p>0.05). SIGNIFICANCE: High alumina ceramic revealed significantly higher mean flexural strength values than that of zirconia ceramic tested in this study either with or without mechanical cycling conditions.