An experimental study on hydrothermal degradation of cubic-containing translucent zirconia

Abstract

PURPOSE The aims of this study were to investigate mechanical properties and hydrothermal degradation behaviour of the cubic-containing translucent yttrium oxide stabilized tetragonal zirconia polycrystal (Y-TZP). MATERIALS AND METHODS Four groups of Y-TZP (T, ST, XT, and P), containing different amount of cubic crystal, were examined. Specimens were aged by autoclaving at 122℃ under 2 bar pressure for 8 h. Phase transformation was analyzed using X-ray diffraction (XRD) to measure phase transformation (t→m). Kruskal-Wallis test was used to determine the difference. Surface hardness, biaxial flexural strength, and fracture toughness in values among the experimental groups and verified with Wilcoxon matched pairs test for hardness values and Mann Whitney U for flexural strength and fracture toughness. RESULTS XRD analysis showed no monoclinic phase in XT and P after aging. Only Group T showed statistically significant decreases in hardness after aging. Hydrothermal aging showed a significant decrease in flexural strength and fracture toughness in group T and ST, while group XT and P showed no effect of aging on fractural strength and fracture toughness with P <.05. CONCLUSION Hydrothermal aging caused reduction in mechanical properties such as surface hardness, biaxial flexural strength, and fracture toughness of Y-TZP zirconia. However, cubic-containing zirconia (more than 30% by volume of cubic crystal) was assumed to have high resistance to hydrothermal degradation. Clinical significance: Cubic-containing zirconia could withstand the intraoral aging condition. It could be suggested to use as a material for fabrication of esthetic dental restoration.

The effect of nonthermal argon plasma surface treatment on the fracture resistance of monolithic zirconia restorations containing tetragonal and cubic grains

“…LTD may also be another reason for the significantly lower fracture resistance values of the NP-treated tetragonal (IC and LP) and cubic SC zirconia restorations. Kengtanyakich and Peampring [33] investigated the mechanical properties and hydrothermal degradation of disk-shaped 3Y-TZP and cubic zirconia materials. They found that cubic zirconia had lower fracture hardness and flexural strength than 3Y-TZP before aging.…”

Effect of Hydrothermal Degradation on Flexural Fatigue Strength of Various Cubic-Containing Translucent Zirconia

“…It was found that the average grain size for group XT was 1.57 µm which was larger than the group T and ST. Group P had the largest grain sizes of 2.28 µm. 7 Therefore, larger grain sizes of group XT and P might contribute to lower mechanical strength compared with smaller grains of group T and ST due to the dislocation on the crystal grain boundaries under dynamic or fatigue assessment affecting the transposition of the stimuli from grain to grain. 19,20 The strength in present results was higher than a previous study which evaluated the flexural fatigue strength of 3Y- TZP, 4Y-PSZ, and 5Y-PSZ on a 3-point bend test for 6,000 cycles.…”

Surface Roughness and Translucency of Various Translucent Zirconia Ceramics after Hydrothermal Aging

“…Hydrothermal aging simulation was set up using an autoclave oven (TOMY ES 215/ES-315, TOMY Kogyo) at 122°C under pressure of 2 atm for 8 hours. 10 Each specimen was sealed in a sterilization pack and placed in the autoclave. After aging, all specimens were air-dried for 24 hours before testing.…”

“… 9 Cubic crystal is the most stable phase structure; therefore, mechanical properties of cubic-containing zirconia seem to be stable after being hydrothermally aged. 10 Even though cubic-containing zirconia (4Y-TZP and 5Y-TZP) is proved to resist to hydrothermal aging, some tetragonal crystals presenting in 4Y-TZP and 5Y-TZP are prone to be transformed to monoclinic phase spontaneously after being immersed in water in long-term period especially at the zirconia surfaces. Also, there is little evidence showing that the translucency of cubic-containing zirconia is stable after aging.…”