Anwar, R Radwan
| Anwar, R Radwan |
Anwar, R Radwan, Xuejing Xu, Sonaj Vardhaman, Mark Wolff
Yu Zhang
Division of Restorative Dentistry, Preventive and Restorative Sciences, University of Pennsylvania, School of Dental Medicine
Introduction
Ceramics are known to fail from flaws that dominate intrinsic microstructural features. Therefore, damage tolerance tests are vital for predicting the clinical behavior of ceramic restorations. Flaws can be introduced during ceramic processing or from occlusal adjustments with burs. The goal of this study is to analyze the damage tolerance of newly developed two-step sintered, high-strength and high-translucency 5Y-PSZ relative to it’s conventionally sintered counterpart using controlled indentation flaws.
Methods
Two-step sintered Zpex Smile (5Y) disc samples (Ø12 x 1 mm, n = 60) were produced using Tosho powder and sintered at 1550°C for 1 minute followed by 1150°C for 10 hours. The same zirconia composition (n = 60) was also conventionally sintered following manufacturer’s instructions. All samples were polished to 1-μm finish. Each sample was subjected to Vickers indentation with loads ranging from 0.1 N to 98 N. The samples were subsequently loaded with the indented surface in tension in a piston-on-three-ball testing jig. Optical microscope images were taken before and after the flexure test. Flexural strength versus indentation load data was plotted to determine the strength degradation.
Results
The intrinsic strength of two-step sintered 5Y was greater than the conventionally sintered counterpart. The strength of two-step sintered 5Y and conventionally sintered 5Y dropped by 50% at an indentation load of 1 N, and 3 N respectively. Optical images reveled that although low loads did not degrade the strength, they were sufficient to initiate cracks.
Conclusion
Although the two-step sintering fabrication method enhances the intrinsic strength of 5Y, it decreases the damage resistance when compared to the conventional sintering technique.