Statement of problem

Whether reusing the buttons of pressable ceramic materials affects their color or translucency is unclear.

Purpose

The purpose of this in vitro study was to investigate the effect of additional pressing on the color and translucency of 3 different lithium disilicate ceramic brands.

Material and methods

Seventy-two disk-shaped ceramic specimens (Ø14×1.5 mm) were divided into 2 groups: pressed group and additionally pressed group, each containing 36 specimens. These groups were further divided into 3 subgroups: lithium disilicate (LDS), lithium disilicate with high-density micronization technology (LDS-HDM), and zirconia-reinforced lithium silicate (ZLS). Pressing was performed in the press group yielding 36 pressed specimens. Additional pressing was performed by using the buttons resulting from the press group, yielding 36 additionally pressed specimens. Color differences and translucency between pressed and additionally pressed groups were measured with a portable spectrophotometer (VITA Easyshade Compact). The translucency parameter (TP) was measured on black and white backgrounds. Color differences between the 2 groups were analyzed statistically by using the Kruskal-Wallis nonparametric test followed by the Dunn-Sidek method for individual comparison among means of all groups (α=.05).

Results

A statistically significant difference was found in color after additional pressing among the 3 tested materials (P=.005). After additional pressing, color difference (ΔE) values were found between the LDS group (3.78 ±1.11) and the ZLS group (3.03 ±1.44). These ΔE values were beyond the selected clinical perceptible threshold (ΔE=2.6). However, the LDS-HDM group had a ΔE value of 1.80 ±1.22, which is considered clinically not perceivable. Furthermore, LDS showed a statistically significant decrease in translucency after additional pressing (P=.002). However, after additional pressing, ZLS and LDS-HDM showed no statistically significant differences in translucency (P>.05).

Conclusions

The colors of the 3 tested materials were affected by additional pressing. Only LDS-HDM showed color changes below the selected clinically perceptible threshold (ΔE=2.6). Furthermore, only LDS showed a significant decrease in translucency.

中文翻译：

---

额外压制对可压制陶瓷材料颜色和半透明性的影响：一项体外研究

问题陈述

重复使用可压陶瓷材料的按钮是否会影响其颜色或半透明度尚不清楚。

目的

这项体外研究的目的是研究额外压制对 3 种不同二硅酸锂陶瓷品牌的颜色和半透明度的影响。

材料与方法

72个圆盘状陶瓷试样（Ø14×1.5 mm）分为2组：压制组和加压组，每组36个。这些组进一步分为 3 个亚组：二硅酸锂 (LDS)、采用高密度微粉化技术的二硅酸锂 (LDS-HDM) 和氧化锆增强硅酸锂 (ZLS)。在压机组中进行压制，产生 36 个压制样品。使用压机组产生的按钮进行额外压制，产生 36 个额外压制的样品。用便携式分光光度计（VITA Easyshade Compact）测量压制组和额外压制组之间的颜色差异和半透明度。在黑色和白色背景上测量半透明参数 (TP)。

结果

在 3 种测试材料之间进行额外压制后发现颜色存在统计学上的显着差异 ( P = .005)。额外加压后，发现 LDS 组 (3.78 ±1.11) 和 ZLS 组 (3.03 ±1.44) 之间的色差 (ΔE) 值。这些 ΔE 值超出了选定的临床可感知阈值 (ΔE=2.6)。然而，LDS-HDM 组的 ΔE 值为 1.80 ±1.22，这在临床上被认为是不可感知的。此外，在额外按压后，LDS 的半透明度在统计学上显着降低（P = .002）。然而，在额外按压后，ZLS 和 LDS-HDM 在半透明度方面没有显示出统计学上的显着差异（P > .05）。

结论

3种测试材料的颜色受到额外压制的影响。只有 LDS-HDM 显示颜色变化低于选定的临床可感知阈值 (ΔE=2.6)。此外，只有 LDS 显示半透明度显着降低。