Statement of problem

Materials possessing fluorescent properties are assumed to emit sufficient visible light to change tooth color under daylight illumination. Fluorescent and nonfluorescent glaze pastes are available to finish the surface of a pressed lithium disilicate restoration. However, the effect of a fluorescent-glaze layer on the final color of the restoration remains unclear.

Purpose

The purpose of this in vitro study was to measure the color dimensions of lithium disilicate glass-ceramic with different thicknesses and different surface treatments under daylight (D65) illumination conditions.

Material and methods

A total of 120 pressed lithium disilicate glass-ceramic disks were fabricated with 4 different thicknesses: 0.7, 1.2, 1.7, and 2.2 mm. In each thickness, 3 different subgroups were created based on the surface treatment performed (n=10): polished (NG), clear glaze (CG), and fluorescent glaze (FG). For the NG group, disks were polished with 180-, 320-, 600-, 800-, and 1400-grit SiC papers and a polishing machine. For the glazed groups, the CG and FG groups, the specimens were polished with 180-grit SiC papers and the same polishing machine. After the polishing sequence, the final thickness was verified in all groups by using digital calipers (0.5, 1.0, 1.5, and 2.0 mm). Additionally, 20 μL of clear glaze or fluorescent glaze was applied on the CG and FL groups by using an electronic positive displacement repeating pipette. The glaze layer was crystallized in a furnace according to the manufacturer recommendations. Color measurements in the CIELab coordinates were made with a spectrometer coupled to an integrating sphere and a standardized photography gray card as a background. Color difference (ΔE) values were calculated by using the CIE76 and CIEDE2000 formulas. The Shapiro-Wilk test revealed that the data were normally distributed. Two-way ANOVA and the Bonferroni test for multiple comparisons were used to analyze the data (α=.05).

Results

Statistically significant differences were found among the groups for the L∗, a∗, and b∗ values for the different ceramic thicknesses and surface finishing treatments evaluated (P<.001), except for the b∗ value between the FG and CG groups (P=.988). The L∗ value on the polished group was significantly higher than that on the glazed specimens, followed by the fluorescent-glazed and then by the clear-glazed specimens (P<.001). The ΔE values using the CIE76 formula varied from 0.87 to 2.76 among specimen groups and from 0.32 to 2.34 using the CIEDE2000 among the tested groups.

Conclusions

Ceramic thickness and surface finishing treatment affected all color dimensions (L∗, a∗, and b∗ values) of lithium disilicate ceramic under daylight conditions. These differences resulted in a perceptible but acceptable color mismatch. The value (L∗ color dimension) of the lithium disilicate ceramic was higher on fluorescent-glazed than on not–fluorescent-glazed specimens.

中文翻译：

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荧光和非荧光釉浆对不同厚度二硅酸锂压制陶瓷颜色的影响

问题陈述

假设具有荧光特性的材料在日光照射下发出足够的可见光来改变牙齿的颜色。荧光和非荧光釉浆可用于完成压制的二硅酸锂修复体的表面。然而，荧光釉层对修复体最终颜色的影响仍不清楚。

目的

这项体外研究的目的是在日光 (D65) 光照条件下测量不同厚度和不同表面处理的二硅酸锂微晶玻璃的颜色尺寸。

材料与方法

总共制造了 120 个压制的二硅酸锂玻璃陶瓷盘，具有 4 种不同的厚度：0.7、1.2、1.7 和 2.2 毫米。在每个厚度中，根据所进行的表面处理 (n=10) 创建 3 个不同的子组：抛光 (NG)、清釉 (CG) 和荧光釉 (FG)。对于 NG 组，磁盘用 180、320、600、800 和 1400 粒度的 SiC 纸和抛光机抛光。对于上釉的组（CG和FG组），用180粒度的SiC纸和同一台抛光机对样品进行抛光。在抛光序列之后，使用数显卡尺（0.5、1.0、1.5 和 2.0 毫米）验证所有组的最终厚度。此外，使用电子正位移重复移液器将 20 μL 清釉或荧光釉涂在 CG 和 FL 组上。根据制造商的建议，釉层在熔炉中结晶。CIELab 坐标中的颜色测量是使用与积分球耦合的光谱仪和作为背景的标准化摄影灰卡进行的。使用 CIE76 和 CIEDE2000 公式计算色差 (ΔE) 值。Shapiro-Wilk 检验显示数据呈正态分布。使用双向方差分析和用于多重比较的 Bonferroni 检验来分析数据 (α=.05)。Shapiro-Wilk 检验显示数据呈正态分布。使用双向方差分析和用于多重比较的 Bonferroni 检验来分析数据 (α=.05)。Shapiro-Wilk 检验显示数据呈正态分布。使用双向方差分析和用于多重比较的 Bonferroni 检验来分析数据 (α=.05)。

结果

除了 FG 和 CG 组之间的 b∗ 值（P <.001）外，在不同陶瓷厚度和表面精加工处理的 L∗、a∗ 和 b∗ 值的组之间发现了统计学上的显着差异（P = .988）。抛光组的 L∗ 值显着高于釉面样品，其次是荧光釉面样品，然后是透明釉面样品（P <.001）。使用 CIE76 公式的 ΔE 值在样本组之间从 0.87 到 2.76 变化，在测试组中使用 CIEDE2000 变化从 0.32 到 2.34。

结论

在日光条件下，陶瓷厚度和表面精加工处理影响了二硅酸锂陶瓷的所有颜色尺寸（L*、a* 和 b* 值）。这些差异导致可察觉但可接受的颜色不匹配。荧光釉面的二硅酸锂陶瓷的值（L* 颜色尺寸）高于非荧光釉面样品。