Ultra-fine Yttria-Stabilized Zirconia for dental applications: A step forward in the quest towards strong, translucent and aging resistant dental restorations

To decrease the light scattering caused by birefringence of the tetragonal phase of dental Yttria-Stabilized Zirconia (YSZ), two main strategies are followed: 1) increasing Y2O3 content to have a larger amount of non-birefringent cubic phase or 2) decreasing grain size below 100 nm to reduce their scattering coefficient. Both strategies might affect mechanical properties and aging resistance. This study shows that increasing the stabilizer content enhances both translucency and aging resistance, at the expense of mechanical properties. Nanometric-sized YSZ show, instead, very interesting compromise. Nanometric-sized zirconia stabilized with 3 mol.% of Y2O3 possesses high strength and toughness (above 1600 MPa and 3.3 MPa m1/2), aging resistance and translucency, thanks to its fully-stabilized tetragonal nano-grains. Nanometric-sized zirconia stabilized with 1.5 mol.% of Y2O3 has the best mechanical performances (strength above 1500 MPa and toughness of 4.8 MPa m1/2), still showing aging resistance and intermediate opacity. These results highlight the interest of moving towards Yttria-containing transformable tetragonal nano-ceramics for dental applications.