Tabatabaian Farhad, Masoomi Faeze, Namdari Mahshid, Mahshid Minoo
Assistant Professor, Department of Prosthodontics, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Graduate Student, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
J Dent (Tehran). 2016 Sep;13(5):340-348.
Masking ability of a restorative material plays a role in hiding colored substructures; however, the masking ability of zirconia ceramic (ZRC) has not yet been clearly understood in zirconia-based restorations. This study evaluated the effect of three different core materials on masking ability of a ZRC.
Ten zirconia disc samples, 0.5mm in thickness and 10mm in diameter, were fabricated. A white (W) substrate (control) and three substrates of nickel-chromium alloy (NCA), non-precious gold alloy (NPGA), and ZRC were prepared. The zirconia discs were placed on the four types of substrates for spectrophotometry. The L*, a*, and b* values of the specimens were measured by a spectrophotometer and color change (ΔE) values were calculated to determine color differences between the test and control groups and were then compared with the perceptual threshold. Randomized block ANOVA and Bonferroni test analyzed the data. A significance level of 0.05 was considered.
The mean and standard deviation values of ΔE for NCA, NPGA, and ZRC groups were 10.26±2.43, 9.45±1.74, and 6.70±1.91 units, respectively. Significant differences were found in the ΔE values between ZRC and the other two experimental groups (NCA and NPGA; P<0.0001 and P=0.001, respectively). The ΔE values for the groups were more than the predetermined perceptual threshold.
Within the limitations of this study, it was concluded that the tested ZRC could not well mask the examined core materials.
修复材料的遮色能力在遮盖有色亚结构方面发挥作用；然而，在基于氧化锆的修复体中，氧化锆陶瓷（ZRC）的遮色能力尚未得到明确了解。本研究评估了三种不同核材料对ZRC遮色能力的影响。
制作了10个厚度为0.5mm、直径为10mm的氧化锆圆盘样本。制备了白色（W）基底（对照）以及镍铬合金（NCA）、非贵金属合金（NPGA）和ZRC三种基底。将氧化锆圆盘放置在这四种类型的基底上进行分光光度测定。用分光光度计测量样本的L*、a和b值，并计算颜色变化（ΔE）值，以确定测试组与对照组之间的颜色差异，然后与感知阈值进行比较。采用随机区组方差分析和Bonferroni检验分析数据。显著性水平设定为0.05。
NCA组、NPGA组和ZRC组的ΔE平均值和标准差分别为10.26±2.43、9.45±1.74和6.70±1.91单位。ZRC组与其他两个实验组（NCA组和NPGA组）的ΔE值存在显著差异（分别为P<0.0001和P=0.001）。各组的ΔE值均超过预定的感知阈值。
在本研究的局限性范围内，得出的结论是，所测试的ZRC不能很好地遮盖所检查的核材料。
