ObjectiveThis study aims to evaluate the optical data of the different sites of the cobalt-chrome (Co-Cr) alloy abutments covered by four different all-ceramic crowns and the color difference between the crowns and target tab using a digital dental spectrophotometer. Methods Ten Co-Cr alloy abutments were made and tried in four different groups of all-ceramic crowns, namely, Procera aluminia, Procera zirconia, Lava zirconia (Lava-Zir), and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic. The color data of the cervical, body, and incisal sites of the samples were recorded and analyzed by dental spectrophotometer. The CIE L*, a*, b* values were again measured after veneering. The color difference between the abutments covered by all-ceramic crowns and A2 dentine shade tab was evaluated. Results The L* and b* values of the abut-ments can be increased by all of the four groups of all-ceramic copings, but a* values were decreased in most groups. A statistical difference was observed among four groups. After being veneered, the L* values of all the copings declined slightly, and the values of a*, b* increased significantly. When compared with A2 dentine shade tab, the ΔΕ of the crowns was below 4. Conclusion Four ceramic copings were demonstrated to promote the lightness and hue of the alloy abutments effec-tively. Though the colorimetric baseline of these copings was uneven, veneer porcelain can efficiently decrease the color difference between the samples and thee target.%目的：采用牙科分光光度比色仪评估钴铬合金基底表面4种全瓷冠各部位的色度学参数及与目标色片的色差。方法制作钴铬合金基牙预备体（钴铬合金基底），分别戴入Procera氧化铝（Pro-Alu）、Procera氧化锆（Pro-Zir）、Lava氧化锆（Lava-Zir）、二矽酸锂增强压铸玻璃陶瓷IPS E.max Press（E.max-HO）4种材料的底冠，并烧结与底冠相同材料的体瓷，制作成全瓷冠。采用牙科分光光度比色仪对钴铬合金基底及底冠、体瓷戴入后样本的颈1/3、体1/3、切1/3区域进行测色。以Vitapan Classical比色板A2色体瓷片为对照，比较各组样本与目标色片A2的色差。结果4种底冠均提高基牙的L*和b*值，a*值下降（除Lava-zir底冠颈部外）；4种底冠L*（除Pro-Zir与Lava-Zir切端、Lava-Zir与E.max-HO颈部外）、a*、b*值均有统计学差异。戴入体瓷后，4种全瓷冠L*值略下降（除Pro-Alu体瓷外），a*、b*值明显上升。4种体瓷与A2体瓷色差ΔΕ均小于4。结论4种全瓷冠对金属基底都有良好遮色性，虽然明度、彩度有差别，但颜色一致性在临床可接受范围。
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