The effect of real time and accelerated aging on the physical and mechanical properties of YTTRIA partially stabilized zirconia
Alalawi, Haidar Ali
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OBJECTIVES: To evaluate accelerated and real time aging effect on microstructure and mechanical properties of different types of zirconia’s with various surface treatments. METHODS: In this in-vitro study 830 discs were prepared from four Y-TZP based materials. These materials were TZ-3YSB-E, ZPex®, ZPex® Smile (Tosoh Corporation, Japan), and Cercon®xt extra translucent zirconia (Dentsply-Sirona). Final dimensions of each specimen disc were about 15 mm in diameter and 1.5 mm thick. An accelerated aging process for 5, 24, and 168 hours of steam aging at 134°C under a pressure of 0.2 MPa was applied to the specimens. Real time aging was performed for one year in normal saline solution at 37°C in an incubator. Sandblasting was performed using a PrepStar® system with Al2O3 50μm particle size at pressure of 60 psi, rate 4.2 gram/minute. Grinding with a Buehler AutoMet 250 was performed using a 240 μm diamond disc with a 0.0034 kg/mm2 load and speed of 120 rpm for two minutes. Bruker D8 advance diffractometer was used for the acquisition of X-ray diffraction (XRD) spectrum. Biaxial flexural strength was determined using a ball-on-three-balls configuration in a universal testing machine. Scanning Electron Microscopy (SEM) was used to examine the sample's surface topography. RESULTS: The results of this study show that the zirconia materials with smaller grain size have higher flexural strength. Sandblasting and grinding treatment increases the tensile flexural strength of TZ-3YSB-E and ZPex® compared to the controlled group of the same material. XRD analysis shows that TZ-3YSB-E at room temperature does not have any monoclinic phase before surface treatment and it increased after aging, sandblasting and grinding. Cercon®xt has the highest amount of cubic phase and it increases with surface treatment. CONCLUSION: Sandblasting surface treatment should not be applied to all types of zirconia and it has to be material specific. Within the scope of this study, accelerated aging process did not affect the grain size of all materials control groups. The smaller grain size of zirconia is correlated to higher flexural strength of the material. The smaller amount of cubic phase present is correlated to higher biaxial flexural strength.