The purpose of the present study was to evaluate the mechanical durability of a zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al(2)O(3) nanocomposite) in comparison to yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and discuss its application on ceramic dental restorations. The disk-shaped specimens of both materials were stored in physiological saline solution at 80 degrees C for 30 days, in 4% acetic acid at 80 degrees C for 30 days, and in an autoclave at 121 degrees C for 10 days. Before and after storage, specimens were subjected to the biaxial flexure test and to the determination of the monoclinic zirconia content. After autoclaving, Y-TZP showed remarkable increasing of the content of monoclinic zirconia: 0.3 vol % before and 49.9 vol % after, and slight decreasing of biaxial flexure strength: 1046 MPa before and 892 MPa after; whereas Ce-TZP/Al(2)O(3) nanocomposite showed no significant difference in the monoclinic content (4.8-5.5 vol %) and the biaxial flexure strength (1371-1422 MPa) after storage in any conditions. It is concluded that, compared to Y-TZP, the Ce-TZP/Al(2)O(3) nanocomposite has a high biaxial flexure strength along with a satisfactory durability in terms of low-temperature aging degradation in above conditions. This study indicates that the Ce-TZP/Al(2)O(3) nanocomposite demonstrates excellent mechanical durability for dental restorations such as all-ceramic bridges.

The purpose of this study was to evaluate the low temperature aging degradation (LTAD) of two types of zirconia through the determination of fracture toughness before and after autoclaving. The fracture toughness of yttria stabilized tetragonal zirconia polycrystals (Y-TZP) and zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al 2 O 3 nanocomposite, so called NANOZR) were determined by Single Edge V-Notch Beam (SEVNB) method before and after autoclaving at 134°C for 5 h. The fracture surfaces were characterized by micro-X-ray diffractometry and micro-Raman spectroscopy. Mean fracture toughness of Y-TZP slightly decreased from 6.31 to 5.79 MPa·m 1/2 with the autoclaving ( p < 0.01). On the other hand, mean fracture toughness of NANOZR showed no change as 11.03 MPa·m 1/2 ( p > 0.1) and was 1.751.91 times larger than that of Y-TZP. It seems to be caused by that NANOZR is susceptible to stress-induced transformation from tetragonal to monoclinic, but quite stable against LTAD.

No abstract

No abstract

This study was aimed to investigate the effect of grinding, sandblasting by alumina and SiC, and heat treatment on the phase transformation from tetragonal to monoclinic zirconia on the surface of yttria stabilized tetragonal zirconia (Y-TZP) and zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite). The monoclinic phase content of both materials increased with the grinding and the sandblasting, while it decreased with the heat treatment. The monoclinic content sequentially increased with the sandblasting and decreased with the heat treatment to each specific value. The SiC-sandblasting produced the larger monoclinic content than alumina-sandblasting. Furthermore, the content changes of the nanocomposite were larger than Y-TZP.