Fatigue limit of polycrystalline zirconium oxide ceramics: Effect of grinding and low temperature aging.
The following study aimed to evaluate the effect of grinding and low temperature aging on the fatigue limit of Y TZP ceramics for frameworks and monolithic restorations. Disc specimens from each ceramic material, Lava Frame (3M ESPE) and Zirlux FC (Ivoclar Vivadent) were manufactured according to ISO:6872 2008 and assigned in accordance with two factors: (1) "surface treatment" without treatment (as sintered, Ctrl) grinding with coarse diamond bur (181um; Grinding) and (2) "low temperature aging (LTD)" presence and absence. Grinding was performed using a contra angle handpiece under constant water cooling. LTD was simulated in an autoclave at 134degC under 2 bar pressure for 20h. Mean flexural fatigue limits (20,000 cycles) were determined under sinusoidal loading using stair case approach. For Lava ceramic, it was observed a statistical increase after grinding procedure and different behavior after LTD stimuli (Ctrl<Grinding; Ctrl<Ctrl Ltd; Grinding=Grinding Ltd) while for Zirlux, grinding and low temperature aging promoted a statistical increase in the fatigue limit (Ctrl<Grinding; Ctrl<Ctrl Ltd; Grinding<Grinding Ltd) An important increase was observed in m phase content after both stimuli (grinding and LTD) although with different intensities. Additionally, fatigue test did not promote increase of m phase content. Thus, tested grinding and low temperature aging did not damage the fatigue limit values significantly for both materials evaluated, even though those conditions promoted increase in m phase.
Journal of the mechanical behavior of biomedical materials