Mechanical Properties of Dental Zirconia Ceramics Changed with Sandblasting and Heat Treatment

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Two types of tetragonal zirconia polycrystals (TZP), a ceria-stabilized TZP/Al_2O_3 nanocomposite (CZA) and a conventional yttria-stabilized TZP (Y-TZP), were sandblasted with 70-μm alumina and 125-μm SiC powders, then partially annealed at 500-1200℃ for five minutes. Monoclinic ZrO_2 content was determined by X-ray diffractometry and Raman spectroscopy. Biaxial flexure test was conducted on the specimens before and after the treatments. Monoclinic ZrO_2 content and biaxial flexure strength increased after sandblasting, but decreased after heat treatment. However, in both cases, the strength of CZA was higher than that of Y-TZP. Raman spectroscopy showed that a compressive stress field was introduced on the sample surface after sandblasting. It was concluded that sandblasting induced tetragonal-to-monoclinic phase transformation and that the volume expansion associated with such a phase transformation gave rise to an increase in compressive stress on the surface of CZA. With the occurrence of such a strengthening mechanism in the microstructure, it was concluded that CZA was more susceptible to stress-induced transformation than Y-TZP.
日本歯科理工学会の論文