Effect Of Dyeing Time On Color Penetration Depth Of Zirconia

Objective:To analyze the influence of dyeing time on the surface color characteristics and dyeing depth of dental Upcera-ST white zirconia ceramics.Methods:1)84 Upcera-ST white zirconia test samples were made by 3shape CAD/CAM software in diameter 10x10mm of length and width,and all samples were divided into 4 groups for different thickness（0.5、1.0、1.5 and 2.0mm）,with 21 samples in each thickness group).All samples of each thickness group,be further divided into 7groups according to the dyeing time（10s、20s、30s、60s、120s、180s、and 240s）with3 samples in each time group),were immersed in the Upcera A2 staining solution.The values of L*、a*and b*of sintered samples and the VITA classic A2 shade-card were measured and recorded by means of ShadeEye NCC.The data were analyzed by the way of analysis of variance of factorial design with SPSS 18.0 software.The Chromatic aberration between each group and the A2 shade card were calculated and recorded(ΔE=[（ΔL）²+（Δa）²+（Δb）²]^1/2).Color matching of dying specimen to A2colorimetric cards based on Chromatic aberration.2)27 Upcera-ST white zirconia samples were made by 3shape CAD/CAM software in diameter 10x10x2.5mm.The samples were divided into 9 groups according to the dyeing time（5s、10s、15s、20s、30s、60s、120s、180s、and 240s）with 3 samples in each group.One of the 10x10 surfaces of the sample was exposed,and the other five surfaces were sealed with nail polish and immersed in A2 special dyeing solution for dyeing.All blocks were cut into 2 pieces.The dyeing depths were measured by micrometer in section.The data of L*、a*and b*of exposed surface were measured by ShadeEye NCC,and then,the chromaticity of each group of samples and the A2 color card was calculated after statistical analysis.Color matching of dying specimen to A2 shade card based on Chromatic aberration.The crystal phase structure and constituent elements of the sample section were analyzed by X-ray photoelectron spectroscopy.Results:1).Factorial design analysis of variance show the brightness and chromaticity of the samples was dependent on the thickness and time.In the same thickness group,the brightness decreased and the chromaticity of the samples increased with the increase of dyeing time,and L*、a*、b*values of different dyeing times were statistically different.In the same time group,the brightness decreased and the chromaticity of the samples increased with the increase of thickness,and L*、a*、b*values of different thickness were statistically different.There was an interaction between the thickness and time.The L*value of the A2 shade card was 70.50±0.20,the a*value was-0.73±0.12,and the b*value was 12.97±0.47.The matching range of Chromatic aberration results were:1 mm specimens soaked between 120²40seconds,1.5 mm specimens soaked between 120²40 seconds and 2 mm specimens soaked between 30¹20 seconds,the Chromatic aberration values wereΔE=0-1.5（NBS）.2)dyeing depth（mm）for each dyeing time period:5s:0.543±0.75、10s:1.195±0.25、15s:1.311±0.22、20s:1.341±0.20、30s:1.461±0.14、60s:1.706±0.141、20s:1.731±0.13、180s:2.077±0.15 and 240s:2.175±0.15.There were statistical differences among 9 groups.The matching range of Chromatic aberration result was:the Chromatic aberration value between 30¹20 seconds wasΔE=0-1.5（NBS）.Conclusion:1 The color characteristics and dye penetration depth of zirconia surface were affected by soaking dyeing time.1)When the thickness of the samples were same,the brightness of the surface color decreased and the chromaticity increased with the increase of soaking and dyeing time.In the same soaking dyeing time,with the increase of thickness,the brightness of the surface color decreased and the chromaticity increased.2)Interaction effect on thickness and time.The thickness of the small samples needed a longer soaking time to achieve the desired color,the thickness of the larger samples needed less time to achieve the desired color.3)With the increase of dyeing time,the penetration depth of the staining agent was increased.The surface brightness decreased and the chromaticity increased.Time was the main influence factor of chromatics.2 Staining did not change the crystal phase structure and the peak value of the constituent elements of the sample section.