A thick frame decreases the fracture toughness of veneering ceramics used for zirconia-based all-ceramic restorations

• Yamauchi Shinobu

  Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry Volpe Research Center, ADA Foundation

• Miura Shoko

  Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry Liaison Center for Innovative Dentistry, Tohoku University Graduate School of Dentistry Division of Fixed Prosthodontics, Meikai University School of Dentistry

• Kasahara Shin

  Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry

• Sun Jirun

  Volpe Research Center, ADA Foundation

• Egusa Hiroshi

  Division of Molecular and Regenerative Prosthodontics, Tohoku University Graduate School of Dentistry Liaison Center for Innovative Dentistry, Tohoku University Graduate School of Dentistry

Abstract

Purpose: To investigate the influence of firing condition and thickness of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) frame on the fracture toughness of veneering ceramics. Methods: Layering and pressable ceramics without frames or on 0.8- and 1.2-mm-thick Y-TZP frames were fired with 5 schedules (normal and 4 customized conditions). The fracture toughness of the ceramics was measured at 0.5–2.5 mm from the frame by the indentation fracture method. Crystal structures at the measurement points were evaluated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results: Under customized firing conditions, the fracture toughness of the layering ceramic significantly decreased, particularly near the frame. Use of a 1.2-mm-thick frame significantly decreased the fracture toughness of both layering and pressable ceramics compared to ceramics without the frame. The decreased fracture toughness only occurred close (0.5 and 1.0 mm) to the frame. XRD analysis showed identical diffraction patterns between points near and far from the frame, suggesting that the decreased fracture toughness was not due to crystal defects or impurities. SEM revealed many microcracks and large crystals in layering ceramic near the 1.2-mm-thick frame, possibly resulting from the thermal properties of the zirconia frame, such as large heat capacity and low thermal conductivity. Conclusions: Modification of the firing conditions from the manufacturer's instructions and inclusion of a thick Y-TZP frame decreased the fracture toughness of veneering ceramics at the interface, suggesting that a thick frame would pose a potent fracture risk in veneering ceramics used for zirconia-based allceramic restorations.

Journal

• Journal of Prosthodontic Research

  Journal of Prosthodontic Research 63 (2), 184-192, 2019

  Japan Prosthodontic Society

Keywords

• Firing schedule
• Fracture toughness
• Frame thickness
• Veneering ceramic
• Y-TZP

Details

• CRID: 1390282763115696640
• NII Article ID: 130007655307
• DOI: 10.1016/j.jpor.2018.11.007
• ISSN: 18839207
• ISSN: 18831958
• Web Site: https://api.elsevier.com/content/article/PII:S1883195818304365?httpAccept=text/xml
• Web Site: https://api.elsevier.com/content/article/PII:S1883195818304365?httpAccept=text/plain
• Web Site: https://www.jstage.jst.go.jp/article/jpr/63/2/63_184/_pdf
• Web Site: https://search.jamas.or.jp/link/ui/2020221395
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed