Statement of problem

How the translucency and color of ceramic restorations are affected by surface changes from the corrosive environment in the oral cavity and aging of materials is unclear.

Purpose

The purpose of this in vitro study was to compare the impact of acidic exposure and aging on the color and translucency of monolithic zirconia and lithium disilicate ceramics.

Material and methods

Twenty computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic zirconia specimens and 20 pressed lithium disilicate specimens were fabricated. Half of the specimens of each group were aged in an autoclave (7.5 hours, 134 °C, 0.2 MPa), and the rest were immersed in hydrochloric acid to simulate the acidic conditions in the oral cavity from gastric reflux. The color coordinates L∗, a∗, and b∗ were measured with an ultraviolet spectrophotometer before and after aging or acidic storage. The translucency parameters and contrast ratios were calculated, and the CIEDE2000 color difference formula was used to determine color differences before and after each treatment. ANOVA and ANCOVA test models were used for data analysis (α=.05), while differences of color parameters in respect to acceptability and perceptibility thresholds were evaluated with the 1-sample t test (α=.05).

Results

Lithium disilicate presented a significantly higher translucency parameter and lower contrast ratio at baseline compared with monolithic zirconia specimens (P<.001). Acidic storage significantly impacted all parameters compared with aging, especially for the lithium disilicate group. Color differences were above the acceptability ΔΕ₀₀ threshold for lithium disilicate after acidic storage (P=.001) and below for monolithic zirconia after acidic storage (P=.003).

Conclusions

The performance of lithium disilicate was slightly inferior compared with that of monolithic zirconia specimens, as they presented significant and clinically observable differences for the translucency parameter and ΔΕ₀₀ after acidic storage and aging.

中文翻译：

---

体外老化和酸贮对单片氧化锆和二硅酸锂陶瓷颜色、半透明性和对比度的影响

问题陈述

口腔腐蚀环境和材料老化造成的表面变化如何影响陶瓷修复体的半透明度和颜色尚不清楚。

目的

这项体外研究的目的是比较酸性暴露和老化对整体氧化锆和二硅酸锂陶瓷颜色和半透明度的影响。

材料与方法

制造了 20 个计算机辅助设计和计算机辅助制造 (CAD-CAM) 整体式氧化锆样品和 20 个压制二硅酸锂样品。每组一半的标本在高压釜中老化（7.5小时，134℃，0.2MPa），其余标本浸泡在盐酸中，以模拟胃反流引起的口腔酸性条件。颜色坐标 L*、a* 和 b* 在老化或酸性储存前后用紫外分光光度计测量。计算半透明度参数和对比度，并使用CIEDE2000色差公式确定每次处理前后的色差。ANOVA和ANCOVA检验模型用于数据分析（α=.05），t检验 (α=.05)。

结果

与单片氧化锆样品相比，二硅酸锂在基线时呈现出显着更高的半透明度参数和更低的对比度（P <.001）。与老化相比，酸性储存对所有参数都有显着影响，尤其是对于二硅酸锂组。颜色差异高于酸储存后二硅酸锂的可接受 ΔE _{00阈值 (} P =.001)，低于酸储存后整体氧化锆的可接受性 ΔE 00 阈值 ( P =.003)。

结论

与整体式氧化锆样品相比，二硅酸锂的性能略逊一筹，因为它们在酸性储存和老化后的半透明度参数和 ΔE _{00方面存在显着且临床可观察的差异。}