Papers by Author: Y. Suehiro

Abstract: The aim of this study was to investigate the effect of surface treatments on bonding strength of two kinds of zirconia to three kinds of resin cements. After thermal cycling, the shear bonding strength of both zirconia decreased in all the resin cements. The bonding strengths of two resin cements in which primer contains silane dramatically decreased after the thermal-cycling (p<0.01). Although the surface roughness of both zirconia sandblasted by 125-%m SiC was quite larger than that by 70-%m alumina (p<0.05), there were no significant differences in the bonding strength of the resin cement to both zirconia sandblasted by 70-%m Al2O3 and 125-%m SiC (p>0.05).

Abstract: The effect of sintering condition, sandblasting and heat treatment on biaxial flexure strengths of the zirconia/ alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite, referred to NANOZR) was evaluated in comparison to that of yttria stabilized tetragonal zirconia polycrystals (Y-TZP). The disc-shaped specimens of NANOZR and Y-TZP were cut from the full-sintered or middle-sintered ones. The discs cut from the middle-sintered ones were finally sintered at the same temperature for the full-sintered one. These four kinds of disc were treated in various conditions combined with the sandblasting, the heat treatment, and the storage. The biaxial flexure strength of both middle- and full-sintered Y-TZP decreased with the autoclaving, whereas those of both NANOZR did not change with it. The monoclinic content of both the materials increased with the sandblasting and decreased with the heat treatment. Regardless of the sintering condition, the monoclinic content of the Y-TZP dramatically increased with the autoclaving and those of NANOZR remarkably increased with the sandblasting. Regardless of the different surface roughness, the biaxial flexure strengths of both materials strongly depended on the content of monoclinic ZrO2 on the surface.

Abstract: This study was aimed to investigate the effect of grinding, sandblasting by alumina and SiC, and heat treatment on the phase transformation from tetragonal to monoclinic zirconia on the surface of yttria stabilized tetragonal zirconia (Y-TZP) and zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite). The monoclinic phase content of both materials increased with the grinding and the sandblasting, while it decreased with the heat treatment. The monoclinic content sequentially increased with the sandblasting and decreased with the heat treatment to each specific value. The SiC-sandblasting produced the larger monoclinic content than alumina-sandblasting. Furthermore, the content changes of the nanocomposite were larger than Y-TZP.

Abstract: The effect of sandblasting and heat treatment on biaxial flexure strengths of the zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al2O3 nanocomposite) was evaluated in comparison to that of yttria stabilized tetragonal zirconia polycrystals (Y-TZP). The disc-shaped specimens of the nanocomposite and Y-TZP were sandblasted with 70)m alumina powder. After sandblasting, half of the specimens were heated at 1000°C for 5 min. The biaxial flexure strengths of Y-TZP were independent on the sandblasting, but decreased with the heat treatment. On the other hand, the biaxial flexure strength of the nanocomposite increased with the sandblasting and significantly decreased with the heat treatment. The content of monoclinic ZrO2 of Y-TZP and the nanocomposite increased with the sandblasting pressure and dramatically decreased with the heat treatment. These results suggest that the stress-induced transformation from tetragonal to monoclinic of the nanocomposite occurs more easily than Y-TZP.