Abstract: Objective　To investigate the masking ability of Lava Plus high transparent zirconia under different post-cores including Co-Cr alloy, masking Co-Cr alloy, precious metal and masking precious metal. Methods　 Specimens were fabricated by Lava Plus high transparent zirconia block. The colors of specimens were 2M2 and 3M2. Co-Cr alloy, masking Co-Cr alloy, precious metal, masking precious metal and 2M2, 3M2 zirconia blocks were fabricated as backgrounds. The L, a, b values in the central region of each specimen placed on the different post-cores were measured by using a 3nh spectrophotometer. Multivariate analysis of variance (ANOVA) and LSD’s test were performed, and ΔE values were calculated and compared according to the formula. Results　 There was a statistically significant difference in L, a, b values of colors, backgrounds and their interaction (P = 0.000). The Co-Cr alloy group had the lowest mean L, a, b values among the four backgrounds, and the masking Co-Cr alloy and masking precious metal group had higher mean values than the other two backgrounds. There was a statistically significant difference in ΔL, Δa, Δb, ΔE values of colors, backgrounds and their interaction (P = 0.000), except Δa values in 2M2 and 3M2 groups (P = 0.252). The ΔE values in the Co-Cr alloy group exceeded the clinically acceptable range (ΔE≥5.5), which in the masking Co-Cr alloy group, precious metal group and masking precious metal group were not more than the perceptible threshold (ΔE <2.6). Conclusions　 Co-Cr alloy post-core has a significant effect on the color of Lava Plus high transparent zirconia, while Lava Plus zirconia has good opacity on the other backgrounds.

Key words: zirconia, post-core, color