Assistant Professor, Dental Materials Course, Department of Biomedical and Neuromotor Sciences, Unit of Odontostomatological Sciences, Division of Prosthodontics, Alma Mater Studiorum, University of Bologna, Bologna, Italy.
Assistant Professor, Division of Prosthodontics, Federal University of Santa Maria, Rio Grande do Sul, Brazil.
J Prosthet Dent. 2018 Aug;120(2):269-275. doi: 10.1016/j.prosdent.2017.09.007. Epub 2018 Feb 21.
Although several monolithic zirconia ceramics have recently been introduced, the need for improved optical properties remains. The newest cubic-zirconia has been claimed to have optimal translucency characteristics for esthetic restorations.
This in vitro study evaluated the optical properties of novel cubic ultratranslucent (UT) and supertranslucent (ST) zirconia by comparing them with lithium disilicate (L-DIS) glass-ceramic for the manufacture of monolithic computer-aided design and computer-aided manufacturing (CAD-CAM) molar crowns.
The UT and ST multilayered zirconia and the low-translucency grade L-DIS were milled. Eighty monolithic crowns were made from 2 CAD files, corresponding to thicknesses of 1.0 and 1.5 mm, and subdivided (n=20) into 4 groups: UT1.0, UT1.5, ST1.0, and L-DIS1.5. All groups were shaded using A2 color standard. Translucency of the crowns was measured by total transmission, using a photoradiometer in a dark chamber; furthermore, the contrast ratio was analyzed using a dental spectrophotometer applied to the buccal surface of the crowns. Data were analyzed using the Kruskal-Wallis and post hoc multiple Mann-Whitney U tests with Bonferroni correction (α=.05 divided by the number of tests performed in each set).
When the ceramic types were analyzed, using total transmission and contrast methods, they showed significantly different translucency levels: UT1.0>ST1.0>UT1.5>L-DIS1.5 (total transmission P<.001). Contrast ratio evaluation yielded similar results (P≤.006); however, the differences between ST1.0 and UT1.5 were not significant.
Both the ST1.0 and UT1.0 crowns, even at the maximum thickness tested (UT1.5), showed significantly higher translucency than L-DIS. Zirconia translucency was improved by eliminating the tetragonal phase, which is responsible for the toughening effect; thus, further studies are advocated to investigate the mechanical resistance of cubic zirconia.
尽管最近推出了几种整体式氧化锆陶瓷，但仍需要改善其光学性能。最新的立方氧化锆据称具有最佳的美学修复体透光特性。
本体外研究通过比较新型立方超透（UT）和超透（ST）氧化锆与锂二硅玻璃陶瓷，评估用于制造整体式计算机辅助设计和计算机辅助制造（CAD-CAM）磨牙冠的新型立方超透（UT）和超透（ST）多层氧化锆的光学性能。
研磨 UT 和 ST 多层氧化锆和低透光率级别的 L-DIS。从 2 个 CAD 文件制作 80 个整体式牙冠，对应厚度为 1.0 和 1.5mm，并细分为 4 组：UT1.0、UT1.5、ST1.0 和 L-DIS1.5。所有组均使用 A2 颜色标准进行遮色。使用暗室中的光度计测量牙冠的总透射率，以评估其透光性；此外，使用牙科分光光度计分析牙冠颊面的对比率。使用 Kruskal-Wallis 和事后多重 Mann-Whitney U 检验（Bonferroni 校正，α=每个组中进行的测试次数除以 0.05）对数据进行分析。
当分析陶瓷类型时，使用总透射率和对比方法，它们显示出明显不同的透光水平：UT1.0>ST1.0>UT1.5>L-DIS1.5（总透射率 P<.001）。对比率评估得出相似的结果（P≤.006）；然而，ST1.0 和 UT1.5 之间的差异不显著。
即使在测试的最大厚度（UT1.5）下，ST1.0 和 UT1.0 牙冠的透光率也明显高于 L-DIS。通过消除四方相来提高氧化锆的透光率，四方相负责增韧效果；因此，提倡进一步研究以研究立方氧化锆的机械阻力。
