Juntavee Niwut, Attashu Surawut
Department of Prosthodontics, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.
Division of Biomaterials and Prosthodontics Research, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand.
J Clin Exp Dent. 2018 Aug 1;10(8):e794-e804. doi: 10.4317/jced.55034. eCollection 2018 Aug.
Sintering process is responsible for aesthetic of zirconia restoration. This study evaluated the effect of different sintering temperatures and sintered-holding times on color parameters of monolithic zirconia.
One hundred and thirty five zirconia bar specimens (width-length-thickness = 10×20×1.5 mm) were prepared from yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic and randomly divided into nine groups to be sintered at different temperatures [decreasing- (SD, 1350°C), regular- (SR, 1450°C), and increasing- (SI, 1550°C) sintering temperature] and different sintered-holding times [shortening- (HS, 60 min), regular- (HR, 120 min), and prolonged- (HP, 180 min) sintered-holding time]. Color appearance (ΔE), translucency parameter (TP), contrast ratio (CR), and opalescence parameter (OP) were determined with spectrophotometer. An analysis of variance (ANOVA) and Tukey's multiple comparisons were used to determine for statistically significant difference of color parameters (α=0.05). Crystal sizes were microscopically examined using scanning electron microscope (SEM), and phase composition of zirconia was determined using X-ray diffraction (XRD).
The mean±sd for ΔE, TP, CR, OP were 82.28±1.27, 1.4±0.13, 0.982±0.004, 1.25±0.15 for SDHS, 78.38±0.74, 2.16±0.10, 0.967±0.005, 1.90±0.11 for SDHR, 74.43±0.91, 2.24±0.10, 0.964±0.004, 1.94±0.09 for SDHP, 76.31±1.22, 3.03±0.10, 0.945±0.003, 2,50±0.09 for SRHS, 74.51±1.27, 3.19±0.17, 0.942±0.003, 2.65±0.16 for SRHR, 73.94±0.49, 3.42±0.10, 0.937±0.003, 2,83±0.09 for SRHP, 76.30±0.43, 3.16±0.09, 0.937±0.002, 2.48±0.09 for SIHS 76.73±1.15, 3.05±0.20, 0.939±0.005, 2.38±0.17 for SIHR, and 75.32±1.37, 2.95±0.18, 0.942±0.006, 2.33±0.15 for SIHP. The ΔE, TP, CR, and OP were significantly affected by altering sintering temperatures and holding times (<0.05). Increasing sintering temperature and extending sintering time significantly improved color appearance, translucency, contrast, and opalescence of Y-TZP (<0.05) as evidenced by enlarging grain size and increasing t→m phase shift.
Raising sintering temperature and prolonging sintering time lead to better color appearance, translucency, contrast and opalescence of nano-sized monolithic Y-TZP, and are suggested for sintering process. Color appearance, contrast, monolithic zirconia, opalescence, sintering process, translucency.
烧结过程决定了氧化锆修复体的美观性。本研究评估了不同烧结温度和烧结保持时间对整体式氧化锆颜色参数的影响。
用氧化钇稳定的四方多晶氧化锆（Y-TZP）陶瓷制备135个氧化锆棒状试件（宽×长×厚 = 10×20×1.5 mm），随机分为9组，在不同温度[降温烧结（SD，1350°C）、常规烧结（SR，1450°C）和升温烧结（SI，1550°C）]及不同烧结保持时间[缩短烧结保持时间（HS，60分钟）、常规烧结保持时间（HR，120分钟）和延长烧结保持时间（HP，180分钟）]下进行烧结。用分光光度计测定颜色外观（ΔE）、半透明度参数（TP）、对比度（CR）和乳光参数（OP）。采用方差分析（ANOVA）和Tukey多重比较来确定颜色参数的统计学显著差异（α = 0.05）。用扫描电子显微镜（SEM）显微镜检查晶体尺寸，用X射线衍射（XRD）测定氧化锆的相组成。
SDHS组的ΔE、TP、CR、OP的平均值±标准差分别为82.28±1.27、1.4±0.13、0.982±0.004、1.25±0.15；SDHR组为78.38±0.74、2.16±0.10、0.967±0.005、1.90±0.11；SDHP组为74.43±0.91、2.24±0.10、0.964±0.004、1.94±0.09；SRHS组为76.31±1.22、3.03±0.10、0.945±0.003、2.50±0.09；SRHR组为74.51±1.27、3.19±0.17、0.942±0.003、2.65±0.16；SRHP组为73.94±0.49、3.42±0.10、0.937±0.003、2.83±0.09；SIHS组为76.30±0.43、3.16±0.09、0.937±0.002、2.48±0.09；SIHR组为76.73±1.15、3.05±0.20、0.939±0.005、2.38±0.17；SIHP组为75.32±1.37、2.95±0.18、0.942±0.006、2.33±0.15。改变烧结温度和保持时间对ΔE、TP、CR和OP有显著影响（<0.05）。提高烧结温度和延长烧结时间显著改善了Y-TZP的颜色外观、半透明度、对比度和乳光（<0.05），晶粒尺寸增大和t→m相转变增加证明了这一点。
提高烧结温度和延长烧结时间可使纳米级整体式Y-TZP具有更好的颜色外观、半透明度、对比度和乳光，建议在烧结过程中采用。颜色外观；对比度；整体式氧化锆；乳光；烧结过程；半透明度
