King Saud University, Riyadh, Saudi Arabia
Oper Dent. 2012 Jul-Aug;37(4):406-16. doi: 10.2341/10-237-L. Epub 2012 Feb 16.
Porcelain veneer materials are translucent and are therefore affected by their thickness as well as the color of the underlying substructure, which limits their masking ability and compromises the esthetic result in heavily stained teeth.
The purpose of this study was to compare the contrast ratio (CR) and masking ability of three different veneering ceramics with two thicknesses by measuring the color differences over white and black backgrounds. Correlations between CR and masking ability of these veneering ceramics were evaluated.
A total of 30 disc-shaped specimens (12 mm diameter × 1.0 mm or 1.5 mm) were fabricated in shade A2 from three types of all-ceramic systems: IPS e.max Press (IPSe; Ivoclar Vivadent, Schaan, Liechtensein), Vita VM7 (VM7; VITA Zahnfabrik, Bad Säckingen, Germany), and Nobel Rondo Press Alumina: Solo (NRPA; Nobel Biocare, Zürich-Flughafen, Switzerland). The CR, defined as the ratio of illuminance (Y) of the test material when placed on the black background (Yb) to the illuminance of the same material when placed over a white background (Yw), was determined (CR=Yb/Yw). The color (CIE Lab*) and Y of each specimen were measured over standard white and black tiles using a spectrophotometer (ColorEye 7000 A, Model C6, GretagMacbeth, New Windsor, NY, USA). Masking abilities of the specimens were determined by measuring the color difference (ΔE) over white and black backgrounds. Both CR and ΔE data were analyzed using two-way analysis of variance (ANOVA). One-way ANOVA was used to compare the mean values of CR across the three materials followed by the Duncan multiple comparison test. The correlations between CR and ΔE were determined by comparing R(2) values obtained from a linear regression analysis. A Student t-test for independent samples was used to compare the mean contrast ratio and ΔE values for the two thicknesses.
CR values of NRPA were significantly less than those of IPSe and VM7, and the CR of IPSe was higher than that of VM7. Furthermore, CR increased as the thickness of the discs increased to 1.5 mm for all three materials. Mean ΔE values were significantly higher with 1.0-mm-thick discs than with 1.5-mm discs. Among the three materials it was observed that NRPA had the highest ΔE when compared with IPSe or VM7, whereas the ΔE of the latter two were not significantly different from one another. There was a strong linear correlation between CR and masking ability.
CR and masking ability are affected by the type as well as the thickness of the ceramic used. IPSe and VM7 are similar in their masking abilities, whereas NRPA had the lowest masking ability. NRPA was the most translucent, followed by VM7; IPSe was the most opaque. None of the materials tested was able to completely mask the black background. It is therefore recommended that the type of ceramic should be chosen according to each clinical situation.
瓷贴面材料是半透明的，因此其厚度和底层底色都会对其产生影响，这限制了它们的遮盖能力，从而影响重度染色牙齿的美观效果。
本研究的目的是通过测量白色和黑色背景下的颜色差异，比较三种不同厚度的贴面陶瓷的对比率（CR）和遮盖能力。评估这些贴面陶瓷的 CR 和遮盖能力之间的相关性。
共制作了 30 个直径为 12mm、厚度为 1.0mm 或 1.5mm 的圆盘状试件，来自三种全瓷系统：IPS e.max Press（IPSe；义获嘉伟瓦登特，列支敦士登沙安）、 Vita VM7（VM7；VITA Zahnfabrik，德国巴德沙伊克森）和 Nobel Rondo Press Alumina：Solo（NRPA；诺保科，瑞士苏黎世机场）。CR 定义为测试材料放置在黑色背景下的照度（Yb）与放置在白色背景下的相同材料照度（Yw）之比（CR=Yb/Yw）。使用分光光度计（ColorEye 7000A，Model C6，GretagMacbeth，美国纽约州新温莎市）在标准白色和黑色瓷砖上测量每个试件的颜色（CIE Lab*）和 Y 值。通过测量白色和黑色背景下的颜色差异（ΔE）来确定试件的遮盖能力。使用双向方差分析（ANOVA）分析 CR 和 ΔE 数据。然后使用 Duncan 多重比较检验比较三种材料的 CR 平均值。通过比较线性回归分析得到的 R²值来确定 CR 和 ΔE 之间的相关性。使用独立样本 t 检验比较两种厚度的平均对比度比和 ΔE 值。
NRPA 的 CR 值明显低于 IPSe 和 VM7，而 IPSe 的 CR 值高于 VM7。此外，随着圆盘厚度增加到 1.5mm，所有三种材料的 CR 值都增加。厚度为 1.0mm 的试件的平均ΔE 值明显高于厚度为 1.5mm 的试件。在三种材料中，与 IPSe 或 VM7 相比，NRPA 的 ΔE 值最高，而后两者之间的 ΔE 值没有显著差异。CR 和遮盖能力与陶瓷的类型和厚度有关。IPSe 和 VM7 的遮盖能力相似，而 NRPA 的遮盖能力最低。NRPA 的透光率最高，其次是 VM7；IPSe 的透光率最低。测试的材料都不能完全遮盖黑色背景。因此，建议根据每个临床情况选择陶瓷类型。
