Objectives: This study aimed to evaluate the influence of ceramic type and thickness on the masking ability and final aesthetic effects of chairside machinable all-ceramic crowns.
Methods: Six kinds from three types chairside machinable ceramic materials (IPS e.max CAD HT/MT/LT, IPS Empress LT, and VITA Suprinity HT/T) in shade A2 were fabricated to slice specimens into 1.0, 1.5, and 2.0 mm-thick sections (n=10). The color parameters of the specimens against black and white tiles and four resin substrates (A2, A4, B3, and C4 shade) were measured with a spectrophotometer. The translucency parameter (TP) was calculated using color parameters measured over standard white and black backgrounds. The color differences (ΔE) were calculated between there substrate shades (A4, B3, C4 ) and A2 shade (control group). Two-way analysis of variance (ANOVA) was performed on the TP values. The two va-riables were ceramic type and ceramic thickness. Three-way ANOVA was used to determine the effects of ceramic materials, ceramic thickness, and substrate shades on the ΔE values, followed by Tukey test for multiple comparisons (α=0.05).
Results: Ceramic type, ceramic thickness, and substrate shade significantly affected the ΔE values (P<0.001). The L* and b* values of the specimens increased with increasing ceramic thickness, except in substrate A2, whereas the ΔE values decreased. The color difference of all 1.0 mm-thick specimens or all specimens over the substrates C4 shade exceeded the clinically acceptable threshold (ΔE>3.3).
Conclusions: The masking ability of chairside machinable all-ceramic crowns is influenced by ceramic type and thickness, and ceramic material. The thickness of ceramic less than 2.0 mm cannot mask the gray shade abutment.
目的: 分析瓷材料种类及厚度对椅旁可切削全瓷冠透光性和遮色能力的影响。方法: 选择3类6种A2色调椅旁可切削陶瓷材料（IPS e.max CAD的HT型、MT型、LT型，IPS Empress的LT型和VITA Suprinity的HT型、T型），制备1.0、1.5、2.0 mm厚度的片状试样（n=10）。测色仪分别测量试样在黑、白瓷板和4种色调树脂基底（A2、A4、B3和C4色调）下的色度参数，计算试样的透光度（TP）值以及试样在A4、B3和C4色调基底与A2色调基底（对照组）之间的色差（ΔE）值。双因素方差分析评价瓷材料种类及厚度对试样TP值的影响，三因素方差分析评价瓷材料种类、试样厚度和基底色调对试样ΔE值的影响，Tukey HSD检验多重比较组间差异（α=0.05）。结果: 瓷材料TP值在不同材料和厚度之间的差异有统计学意义（P<0.001），瓷材料种类、试样厚度及基底色调对试样ΔE值的影响均有统计学意义（P<0.001），试样的L*和b*值随着厚度增加而增加（除外A2色调基底），而ΔE值则减少。当试样厚度为1.0 mm或基底为C4色调时，所有试样ΔE值均高于临床可接受的色差阈值（ΔE>3.3）。结论: 椅旁可切削全瓷冠遮色能力受到瓷材料种类和厚度的影响，小于2.0 mm厚度的瓷材料不能遮盖灰色基牙颜色。.
Keywords: all-ceramic crown; chairside machinable ceramic; color diffe-rence; masking ability; resin background.