目的：利用切削素烧瓷块法与三维（three dimensional，3D）胶态成型法制作遮色效果不同的3种氧化锆陶瓷，对比其在不同厚度下的透光性及对异色离体牙的遮色效果，为临床口腔修复提供材料选择依据。方法：制备90片直径14 mm的A2色氧化锆圆盘试件，分成3组（n=30）：（1）CZ组，采用计算机辅助设计（computer aided design，CAD）/计算机辅助制造（computer aided manufacturing，CAM）切削素烧瓷块法；（2）NZW组，采用3D胶态成型法，试件内表面无多孔遮色层；（3）NZY组，采用3D胶态成型法，试件内表面有多孔遮色层。3组试件根据厚度0.6 mm、1.0 mm、1.5 mm再分成3个亚组（n=10）。选用因牙周病拔除的中、重度异色前牙10颗，唇面打磨成大于 6 mm2×6 mm2的平面。暗盒中用Crystaleye比色仪在黑、白背景下分别测量9组试件的色度值（CIE1976L*a*b*），计算透光性［半透性参数（translucency parameter, TP）］。将每组试件与牙齿唇面依次粘接并测量色度值。选标准比色片A2中1/3色度值作为对照，计算试件粘接后同对照色的色差ΔE。以One-way ANOVA和Bonferroni法对数据进行统计分析。结果:（1）3组氧化锆试件在0.6 mm、1.0 mm、1.5 mm 厚度下的TP值分别为：CZ组14.09、12.31和10.45，NZW组19.84、16.54和12.44，NZY组14.81、13.16和11.92。每组试件的3个亚组间透光性均显示为0.6 mm组>1.0 mm组>1.5 mm组，厚度相同的亚组间透光性均显示为NZW组>NZY组>CZ组。（2）3组氧化锆试件粘接后在0.6 mm、1.0 mm、1.5 mm厚度下与对照色的色差ΔE分别为：CZ组10.77、9.94和8.50，NZW组6.84、5.89和5.29，NZY组4.16、3.92和3.67。每组试件的3个亚组间色差值均显示为0.6 mm组>1.0 mm组>1.5 mm组，厚度相同的亚组间色差值均显示为CZ组>NZW组>NZY组。结论：3种氧化锆试件在厚度相同的情况下，透光性均为3D胶态成型技术制作的内表面无遮色处理组试件最好，而遮色效果均为3D胶态成型技术制作的内表面有遮色处理组试件最好，且其厚度在0.6 mm时即可获得较好的遮色效果。
Objective： Three kinds of zirconia specimens were made respectively by milling of the pri-sintered blocks and by three dimensional (3D) gel deposition for in vitro evaluation of their optical translucency under three different thicknesses and their color masking effect on discolored teeth. The study aims for establishing the principle for guiding the materials selection in clinical practice. Methods: Ninety A2-colored zirconia disc specimens with diameter of 14 mm were prepared and were divided into three groups (n=30). (1) Group CZ, by milling of the pre-sintered blanks; (2) Group NZW, by 3D gel deposition, without a color masking opaque inner layer; (3) Group NZY, by 3D gel deposition, with a color masking opaque inner layer. Furthermore, each group was divided into three sub-groups (n=10) according to the sample thickness, i.e., 0.6, 1.0 and 1.5 mm, respectively. The maxillary anterior teeth with severe discoloration, extracted owing to periodontal disease, were collected and embedded. By gentle gridding and polishing a plane, larger than 6 mm2×6 mm2, was generated on the labial surface of each tooth. Chromatic values(CIE1976-L*a*b*) of the zirconia samples in the nine subgroups were measured by the spectrophotometer Crystaleye in front of the black or white background in a cassette, and the translucency parameter (TP) values were calculated for each sample. Thereafter the zirconia specimens were bonded onto the labial surface of the polished teeth for measuring the chromatic values, using the chromatic value of the medium 1/3 of the standardized Vita A2 as a control. The color aberration ΔE between each zirconia specimen and the control value was calculated, respectively. The results were statistically analyzed by One-way ANOVA and Bonferroni. Results: (1) The optical transparency of the three kinds of zirconia disc specimens with the thickness of 0.6, 1.0 and 1.5 mm was 14.09, 12.31 and 10.45 for group CZ；19.84, 16.54 and 12.44 for group NZW；14.81, 13.16 and 11.92 for group NZY. In each group, the degree of optical transparency of the specimens showed a clear tendency as in the sub-group 0.6 mm >1.0 mm >1.5 mm. The TP value of the specimens in the three groups with the same thickness showed a tendency of the group NZW >group NZY >group CZ. (2) After bonding onto the polished labial surface of the teeth, the color aberration ΔE of the specimens with the thickness of 0.6, 1.0 and 1.5 mm was calculated to be 10.77, 9.94 and 8.50 for group CZ; 6.84, 5.89 and 5.29 for group NZW; 4.16, 3.92 and 3.67 for group NZY. In each group, the color aberration of the specimens showed a clear tendency as in the sub-group 0.6 mm >1.0 mm >1.5 mm; the color aberration of the three groups with the same thickness was in the order of the group CZ >group NZW >group NZY. Conclusion: In all the specimen groups with a fixed specimen thickness, the optical translucency of the specimen was the highest in group NZW made by 3D gel deposition, and the best color masking effect was obtained in specimens with a color masking opaque inner layer in group NZY, where a thickness of 0.6 mm was sufficient enough for obtaining the ideal color masking effect.
