Journal
JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS
Volume 65, Issue -, Pages 256-263Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jmbbm.2016.08.023
Keywords
Flexural strength; Phase transformation; Nanoindentation; Surface topography
Funding
- Faculty of Dentistry Summer Student Research Program
- Dr De Souza's University of Toronto Start-up fund
- Dr De Souza's Start-up fund
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Objective: To investigate the effect of aging on phase transformation and mechanical properties of yttria-tetragonal zirconia polycrystal (Y-TZP). Materials and methods: Fully-sintered Y-TZP slabs, IPS E-max ZirCAD (ZC - Ivoclar) and Z-5 ceramic (Z5- C5 Medical Werks), were artificially aged in autoclave for: 0, 30, 60 or 90 min. Flexural strength (FS), crystalline changes (X-ray diffraction analysis - XRD) and surface topography were analyzed. 0 and 90 min-aged samples were evaluated by nanoindentation to measure hardness and modulus, and results were compared using Wilcoxan Mann Whitney rank sum test (p <= 0.05). FS results were compared using two-way ANOVA and Tukey HSD (alpha=0.05). Results: Material factor had significant effect (p=0.001) on flexural strength (Z5=966.95 MPa; ZC=847.82 MPa), but aging did not. Nanoindentation showed incidence of typical load/depth curves combined with some exhibiting features compatible with cracking. When typical curves were considered, aging had no effect on the modulus and hardness, but hardness was dependent on material type. A steady increase in the in phase related to aging time was observed for ZC samples. The maximum incidence of in phase was 6.56% for Z5/60 min. Significance: Flexural strength is not affected by surface transformation in dental Y-TZP. Hydrothermal aging has an effect on m content and surface topography of different zirconia brands, but mechanical tests that can precisely characterize surface changes in aged Y-TZP are still missing. (C) 2016 Elsevier Ltd. All rights reserved.
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