A thick frame decreases the fracture toughness of veneering ceramics used for zirconia-based all-ceramic restorations
Autor: | Jirun Sun, Shoko Miura, Shinobu Yamauchi, Hiroshi Egusa, Shin Kasahara |
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Rok vydání: | 2019 |
Předmět: |
Dental Stress Analysis
Ceramics Materials science Scanning electron microscope 0206 medical engineering 02 engineering and technology Dental Materials 03 medical and health sciences 0302 clinical medicine Thermal conductivity Fracture toughness X-Ray Diffraction Indentation Materials Testing Yttrium Dentistry (miscellaneous) Cubic zirconia Ceramic Composite material Dental Restoration Permanent 030206 dentistry 020601 biomedical engineering Dental Veneers visual_art Microscopy Electron Scanning Fracture (geology) visual_art.visual_art_medium Stress Mechanical Zirconium Oral Surgery Layering |
Zdroj: | Journal of Prosthodontic Research. 63:184-192 |
ISSN: | 1883-1958 |
Popis: | 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 all-ceramic restorations. |
Databáze: | OpenAIRE |
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