The Effect of Hydrothermal Aging on Monolithic Zirconia

Objectives: To evaluate the effect of different zirconia compositions with different levels of translucency and hydrothermal aging on surface roughness and flexural strength of Y-TZP. We hypothesize that higher levels of translucency and hydrothermal aging will affect roughness and flexural strength of Y-TZP.
Methods: Bar-shaped specimens of 14x4x2 mm from four different zirconia compositions were used (n=40 per material): Low translucency 3Y-TZP (3Y-LT); High translucency 3Y-TZP (3Y-HT); and two types of the high translucency 5Y-TZP (5YX-HT; 5YL-HT). Hydrothermal aging (0h – control, 5h, 10h, or 15h at 134 °C, 2 bar) was applied prior to surface roughness (Alpha-Step D-120, KLA Tencor profilometer) and flexural strength (ISO/CD 6872.3) analyses.
Results: There was a significant effect of zirconia’s composition on roughness (p=0.016). Aging (p=0.73) and the interaction material*aging (p=0.073) had no significant effect on surface roughness. The highest Ra value was presented by CT/3Y-HT specimens (2.29µm±0.81) and the lowest by CT/3Y-LT group (0.86µm±0.25). There was a significant interaction effect of material*aging (p=0.012) on flexural strength.
Conclusions: Zirconia materials with higher levels of translucency were associated with significantly higher surface roughness and lower flexural strength. A significant effect of hydrothermal aging was observed for flexural strength but not for surface roughness.