Chu Frederick C S, Chow Tak W, Chai John
Faculty of Dentistry, University of Hong Kong, Hong Kong, China.
J Prosthet Dent. 2007 Nov;98(5):359-64. doi: 10.1016/S0022-3913(07)60120-6.
Although ceramic veneers have been proven to be clinically successful in longevity studies, there is little information on the contrast ratios and masking ability of the available ceramic systems because dental laboratory technology and expensive experimental equipment are required for the investigation. Moreover, the complexity in understanding how to evaluate translucent ceramic materials may also explain why information in this area is limited.
The purpose of this study was to determine the contrast ratios and masking abilities of 3 types of all-ceramic veneers by measuring their luminance and color difference over white and black backgrounds.
Disk-shaped specimens (8-mm diameter x 0.7-mm thickness) of Shade A2 (Vita Lumin) of 3 types of all-ceramic systems: Procera (n=8), Empress 2 (n=8), and Vitadur Alpha (n=10) were fabricated. The luminance (as Y) and color (as CIE Lab*) of the specimens were measured with a colorimeter. The contrast ratio (CR=Yb/Yw), defined as the ratio of illuminance (Y) of the test material when it is placed on the black background (Yb) to the illuminance of the same material when it is placed over a white background (Yw), was determined. The masking ability of a specimen was evaluated by calculating the color difference (DeltaE) of the veneers over white and black backgrounds. Both CR and DeltaE* data were analyzed with 1-way ANOVA and the Tukey HSD test (alpha=.05).
The mean contrast ratios (SD) of Procera, Empress 2, and Vitadur Alpha specimens were 0.50 (0.02), 0.46 (0.05), and 0.39 (0.02), respectively. CR values were significantly different among the 3 materials (P<.001). Procera veneers had a significantly higher CR compared to Empress 2 (P=.01) or Vitadur Alpha (P=.01), whereas the CR of Empress 2 was significantly higher than that of Vitadur Alpha (P=.046). Color difference (DeltaE*) (SD) of Procera, Empress 2, and Vitadur Alpha specimens over black and white backgrounds were 24.46 (1.03), 25.80 (1.03), and 31.08 (1.19), respectively. DeltaE* values were statistically different among the 3 materials (P<.001). Vitadur Alpha specimens had significantly higher DeltaE* when compared with Procera (P<.001) or Empress 2 (P<.001), whereas DeltaE* values between Procera and Empress 2 were not significantly different (P=.331).
Vitadur Alpha had significantly lower contrast ratio and poorer masking ability compared to Procera or Empress 2. The clinical application of Vitadur Alpha as a veneer material over discolored teeth is cautioned. Although the contrast ratio of Procera was significantly higher than that of Empress 2, the masking abilities of these materials were not significantly different. The clinical application of these 2 ceramics as a veneer material may still be limited when applied over intense tooth discoloration because neither can fully mask the color of a black background.
尽管在长期研究中已证明陶瓷贴面在临床上是成功的，但关于现有陶瓷系统的对比度和遮盖能力的信息却很少，这是因为该研究需要牙科实验室技术和昂贵的实验设备。此外，理解如何评估半透明陶瓷材料的复杂性也可能解释了为什么该领域的信息有限。
本研究的目的是通过测量三种全瓷贴面在白色和黑色背景上的亮度和色差，来确定它们的对比度和遮盖能力。
制作了三种全瓷系统（Procera，n = 8；Empress 2，n = 8；Vitadur Alpha，n = 10）的A2色（Vita Lumin）圆盘形试件（直径8毫米×厚度0.7毫米）。用色度计测量试件的亮度（以Y表示）和颜色（以CIE Lab表示）。确定对比度（CR = Yb/Yw），其定义为测试材料置于黑色背景上时的照度（Y）与置于白色背景上时相同材料的照度之比。通过计算贴面在白色和黑色背景上的色差（ΔE）来评估试件的遮盖能力。CR和ΔE数据均采用单因素方差分析和Tukey HSD检验（α = 0.05）。
Procera、Empress 2和Vitadur Alpha试件的平均对比度（标准差）分别为0.50（0.02）、0.46（0.05）和0.39（0.02）。三种材料的CR值有显著差异（P < 0.001）。Procera贴面的CR显著高于Empress 2（P = 0.01）或Vitadur Alpha（P = 0.01），而Empress 2的CR显著高于Vitadur Alpha（P = 0.046）。Procera、Empress 2和Vitadur Alpha试件在黑色和白色背景上的色差（ΔE*）（标准差）分别为24.46（1.03）、25.80（1.03）和31.08（1.19）。三种材料的ΔE值有统计学差异（P < 0.001）。与Procera（P < 0.001）或Empress 2（P < 0.001）相比，Vitadur Alpha试件的ΔE显著更高，而Procera和Empress 2之间的ΔE*值无显著差异（P = 0.331）。
与Procera或Empress 2相比，Vitadur Alpha的对比度显著更低，遮盖能力更差。对于Vitadur Alpha作为变色牙贴面材料的临床应用需谨慎。尽管Procera的对比度显著高于Empress 2，但这些材料的遮盖能力无显著差异。当应用于严重牙齿变色时，这两种陶瓷作为贴面材料的临床应用可能仍然有限，因为它们都不能完全遮盖黑色背景的颜色。
