The influence of speck size in the aging of the zirconia

Objectives: The increscent demand for prosthesis ceramics with esthetic accomplishment and high mechanic capacity, involve the crescent utility of zirconia. When exposit thought saliva the surface of zirconia might suffer a stage transformation, this could be a factor that affects the mechanical resistance. The present study had the aim to investigate the different microstructure that could influence the effect of aging though hydrothermal technic.
Methods: 24 stripe of zirconia stabilized with yttria (ZrO₂ 3% mol Y₂O₃) with this dimensions 2,0 cm X 2,0cm X 1,0cm, was manufactured with different conditions of temperature and processing, this provided distinct size of speck. The sample was divided in 6 groups: group 1: Y TZP with grain size 0,8μm, group 2: YTZP with grain size 0,8μm immersed in artificial saliva for 30 hours at 1350C.; group, 3: YTZP with grain size of 0,3μm (green body before the final sintering); group 4 YTZP with grain size 0,3μm immersed in artificial saliva for 30 hours at 1350C. (green body before the final sintering) group 5 YTZP with 0,3μm grain size after final sintering; group 6 YTZP with grain size 0,3μm immersed in artificial saliva for 30 hours at 1350C, after the final sintering. The stage was identified thought x-ray diffraction. All the samples was featured before aging for testing Vickers hardness, dilatometry and density. The topography of the samples before and after degradation was evaluated in a scanning electron microscope.
Results: The group 1 and 2 samples showed peaks consistent to monoclinic phase. All the samples as with grain size reduced to 0,3μm showed peaks consistent with tetragonal phase. This provided changes in topography after aging.
Conclusions: The effect of aging is inversely proportional to speck size.