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The adverse effects of tungsten carbide grinding on the strength of dental zirconia.

Authors
  • Wang, Yiru1
  • Lam, Walter Y H2
  • Luk, Henry W K2
  • Øilo, Marit3
  • Shih, Kaimin4
  • Botelho, Michael G5
  • 1 Prosthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China; The Affiliated Stomatology Hospital and School of Stomatology, School of Medicine and Key Laboratory of Oral Biomedical Research of Zhejiang Province, Zhejiang University, Hangzhou, China. , (China)
  • 2 Prosthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China. , (China)
  • 3 Department of Clinical Dentistry, Faculty of Medicine, University of Bergen, Bergen, Norway. , (Norway)
  • 4 Department of Civil Engineering, Faculty of Engineering, The University of Hong Kong, Hong Kong SAR, China. , (China)
  • 5 Prosthodontics, Faculty of Dentistry, The University of Hong Kong, Hong Kong SAR, China. Electronic address: [email protected] , (China)
Type
Published Article
Journal
Dental materials : official publication of the Academy of Dental Materials
Publication Date
Apr 01, 2020
Volume
36
Issue
4
Pages
560–569
Identifiers
DOI: 10.1016/j.dental.2020.02.002
PMID: 32063392
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

This study investigated the effects of tungsten-carbide grinding on the surface characteristics and mechanical strength of dental 3 mol% yttria-stabilized zirconia (3Y-TZP). Two types of tungsten-carbide burs (TC), 6-blade (TC1) and 8-blade (TC2) were used to grind 3Y-TZP, in a dental air-turbine handpiece with water-cooling and were also subjected to air-particle abrasion (APA): TC1 + APA and TC2 + APA; and rubber polishing (RP): TC1 + RP and TC2 + RP; one group received only rubber-polishing RP. The control group received no treatment. Surface characterization was examined by surface roughness (Ra) and atomic force microscopy. Specimens were also observed with scanning electron microscopy (SEM) and X-ray-diffraction (XRD) for microstructure and crystalline phases. A piston-on-three-balls biaxial-flexural strength (BFS) test was performed with 15 samples-per-group and the broken specimen were observed under SEM to investigate the fracture origin pattern. One-way ANOVA, Kruskal-Wallis test and Weibull analysis were performed at α = 0.05. Groups TC1 and TC2 had the lowest mean BFS (p < 0.05) with up to 74 % reduction in strength. APA and RP both significantly increased the mean BFS after tungsten-carbide grinding but was still less than the control (p < 0.05). Compared to the control, the mean BFS was significantly reduced for all groups except for the RP group (p < 0.05). APA and rubber-polishing following TC2 grinding had significant higher mean BFS than those following TC1 grinding respectively (p < 0.05). SEM revealed distinct micro-cracks after tungsten-carbide grinding. Tungsten-carbide burs (6- and 8-blade) are not recommended for zirconia grinding due to the significant reduction of biaxial-flexural strength and observed micro-structural surface and subsurface damage. Copyright © 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

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