Toughening of highly translucent zirconia by monoclinic ZrO₂ and SiO₂ particle coating

Abstract

The mechanical properties of highly translucent partially stabilized zirconia (PSZ) need to be improved; however, improvement of mechanical properties often decreases translucency. To overcome this problem, a monoclinic ZrO2 (mZrO2)/SiO2 dispersion was prepared and applied as a coating material for PSZ. The influence of surface treatment by the mZrO2/SiO2 dispersion on the surface topography, crystallography, and mechanical properties of highly translucent PSZ was investigated in this study. Following the treatment, the mechanical strength of highly translucent PSZ improved by 170% compared with control, for the best mZrO2/SiO2 dispersion ratio and heating temperature condition, while maintaining its translucency. The proposed coating is promising for improving the mechanical properties of highly translucent PSZ.

Coating method for smooth and reinforced surface layer of highly translucent zirconia

“…In the previous report, SiO 2 was used as a binder to prevent cracks in the coating layer 8) . However, it was unsuitable for the outer surface of the dental prosthesis because the surface became rough.…”

“…We aim to develop a method to increase the mechanical strength of highly translucent PSZ. In a previous report, we constructed the surface compressive stress layer of tempered glass, and showed that a ceramic coating on the surface of zirconia forms a surface compressive stress layer to increase mechanical strength while maintaining high translucency 8) . A dispersion of two kinds of nanoparticles, mZrO2 and silica (SiO2), was used as a coating material.…”

Nanoparticles and Their Application in Prosthetic Dentistry

“…When unstabilized zirconia is heated above the phase transition temperature and cooled at room temperature, its crystal structure changes from the tetragonal phase to the monoclinic phase. Zirconia does not have sufficient mechanical strength in the monoclinic phase, so stabilizing oxides such as Calcium Oxide (CaO), Magnesium Oxide (MgO) and Yttrium Oxide (Y2O3) are added to its composition in order to keep it partially stabilized in the tetragonal phase at room temperature (79,80).…”

Ceramic Toughening Strategies for Biomedical Applications

“…(A) Monoclinic ZrO 2 and SiO 2 particle coating, toughening highly translucent ZrO 2 . (a–d) scanning electron micrographs, (e–h) Zr and Si elemental mapping of samples coated with mZrO 2 /SiO 2 and heat treated at 1,500°C ( Uno et al, 2020 ). (B) Ion-exchange toughened lithium disilicate glass-ceramic.…”

“…Coating is also an important and widely used method in surface modification. Based on the toughening mechanism of strengthened glass, where the outer surface is compressed to impede breakage because of the outside stress, Uno et al (2020) used a dispersion containing mZrO 2 and SiO 2 as a surface coating agent for partially stabilized zirconia (PSZ). When the crystal phase changed from tetragonal to monoclinic, the mZrO 2 underwent volume change to generate a compressive stress layer on the material’s surface.…”