While waste zirconia can be recycled, whether the optical properties of recycled zirconia match those of commercially available zirconia is unclear. The purpose of this in vitro study was to evaluate the optical properties of recycled zirconia by assessing its color, translucency, and opalescence across different thicknesses and shades. Sixty specimens were prepared from 3 mol% yttria-stabilized tetragonal zirconia polycrystal blocks (Lava Plus; 3M ESPE) (group C); 60 other specimens were prepared from waste blocks of the same zirconia (group R). The specimens were further categorized into 4 subgroups (n=15) based on their thicknesses (1.0 mm or 1.5 mm) and shades (A1 or A3). Specimen color was measured with a spectrophotometer (Easyshade Advance 4.0; Vita ZahnFabrik). The parameters of color difference (ΔE), translucency (TP), contrast ratio (CR), and opalescence (OP) were calculated. Grain size analysis was performed using scanning electron microscopy. Data were analyzed with analysis of variance (ANOVA) (α=.05). Significant differences in translucency and opalescence were observed between groups C and R in all specimens (.001). Group R exhibited a range of TP (4.89 to 11.27), CR (0.74 to 0.91), and OP (3.36 to 8.65) values. The ΔE values between groups C and R ranged from 13.99 to 21.31. Both thickness and shade significantly affected the ΔE values (<.001). The grain size in group C was not significantly different from that in group R (F=0.364, df=1, =.555). The TP and OP values of group R decreased with increasing thickness (<.001). Recycled zirconia was less translucent and opalescent than commercially available zirconia. The color difference between commercially available and recycled zirconia exceeded the acceptable threshold, even when using the same staining procedure. Recycled zirconia exhibited reduced translucency and opalescence with increasing thickness.

中文翻译：

---

用于牙科应用的再生氧化锆的光学特性

虽然废弃氧化锆可以回收，但回收氧化锆的光学性能是否与市售氧化锆相匹配尚不清楚。这项体外研究的目的是通过评估不同厚度和色调的颜色、半透明度和乳光来评估再生氧化锆的光学特性。由 3 mol% 氧化钇稳定的四方氧化锆多晶块（Lava Plus；3M ESPE）制备了 60 个样品（C 组）；由相同氧化锆（R 组）的废块制备了 60 个其他样品。根据样本的厚度（1.0 毫米或 1.5 毫米）和色调（A1 或 A3），样本进一步分为 4 个亚组（n=15）。使用分光光度计（Easyshade Advance 4.0；Vita ZahnFabrik）测量样本颜色。计算色差（ΔE）、半透明度（TP）、对比度（CR）和乳光度（OP）等参数。使用扫描电子显微镜进行晶粒尺寸分析。通过方差分析 (ANOVA) (α=.05) 分析数据。在所有样本中，C 组和 R 组之间观察到半透明度和乳光的显着差异 (.001)。R 组表现出一系列 TP（4.89 至 11.27）、CR（0.74 至 0.91）和 OP（3.36 至 8.65）值。C组和R组之间的ΔE值范围为13.99至21.31。厚度和阴影均显着影响 ΔE 值 (<.001)。C组晶粒尺寸与R组无显着差异（F=0.364，df=1，=.555）。R组的TP和OP值随着厚度的增加而降低(<.001)。回收的氧化锆的半透明性和乳白色度低于市售氧化锆。即使使用相同的染色程序，市售氧化锆和回收氧化锆之间的色差也超过了可接受的阈值。随着厚度的增加，回收的氧化锆的半透明度和乳光度降低。