Research Associate, Department of Prosthetic Dentistry, University Hospital, Ludwig-Maximilians-University, Munich, Germany.
Scientific Head of Dental Material Unit, Department of Prosthetic Dentistry, Dental School, Ludwig-Maximilians-University Munich, Germany.
J Prosthet Dent. 2021 Mar;125(3):518-526. doi: 10.1016/j.prosdent.2020.01.016. Epub 2020 Mar 19.
Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) materials of different formulations (3Y-TZP, 4Y-TZP, and 5Y-TZP) can be colored by using color liquids. However, practically and clinically relevant factors such as modifications of sintering protocols and hydrothermal aging might affect the extent of light transmittance and flexural strength of zirconia materials of different formulations; studies on these outcomes, however, are lacking.
The purpose of this in vitro study was to test the impact of hydrothermal aging on the light transmittance and flexural strength of colored zirconia materials compared with a lithium-disilicate (LiSi) ceramic.
A total of 210 specimens were prepared from 3Y-TZP (n=30), 3Y-TZP (n=30), 5Y-TZP (n=30), 4Y-TZP (n=60), 4Y-TZP (preshaded, n=30), and LiSi (n=30). All specimens, except for 4Y-TZP and LiSi, were manually colored, predried, and either conventionally sintered at 1450 °C (3Y-TZP, 3Y-TZP, 5Y-TZP, and half of 4Y-TZP) or high-speed sintered at 1580 °C (other half of 4Y-TZP and 4Y-TZP). Light transmittance was measured initially and after 2, 5, 10, 20, 40, and 160 hours of hydrothermal aging (134 °C, 0.2 MPa). Biaxial flexural strength was tested initially and after 160 hours of hydrothermal aging (n=15). The Kolmogorov-Smirnov test, multivariate analysis, and 1-way ANOVA with the Tukey HSD post hoc test, the t test, and linear mixed models were calculated (α=.05).
LiSi showed the highest translucency, followed by 5Y-TZP, 4Y-TZP, 4Y-TZP, 3Y-TZP, and 3Y-TZP. 4Y-TZP was most opaque and matte. The decrease in translucency related to aging hours was higher for LiS and conventional sintered zirconia materials than for 4Y-TZP and 4Y-TZP. Initially, 3Y-TZP had the highest flexural strength, followed by 3Y-TZP, 4Y-TZP, and 4Y-TZP. 4Y-TZP was comparable with 4Y-TZP but significantly higher than 5Y-TZP. LiSi had the lowest biaxial flexural strength. Hydrothermal aging increased biaxial flexural strength for 3Y-TZP and 3Y-TZP (P<.001) but decreased it for 5Y-TZP (P=.005) and 4Y-TZP (P<.001). After aging, 4Y-TZP showed comparable values of flexural strength with 4Y-TZP (P=.06) and higher values than 4Y-TZP after aging (P=.019).
Manually colored, conventionally sintered 4Y-TZP was resistant to hydrothermal aging regarding flexural strength. High-speed sintering inhibited color development for manually colored 4Y-TZP but did not affect the resistance to hydrothermal aging. The findings were reversed for industrially preshaded 4Y-TZP.
不同配方的氧化钇稳定四方氧化锆多晶（3Y-TZP、4Y-TZP 和 5Y-TZP）材料可以通过使用彩色液体进行着色。然而，实际和临床相关因素，如烧结方案的修改和湿热老化，可能会影响不同配方氧化锆材料的透光率和抗弯强度；然而，关于这些结果的研究还很缺乏。
本体外研究的目的是测试湿热老化对彩色氧化锆材料透光率和抗弯强度的影响，与锂硅（LiSi）陶瓷进行比较。
共制备了 30 个 3Y-TZP、30 个 3Y-TZP、30 个 5Y-TZP、60 个 4Y-TZP、30 个预着色 4Y-TZP 和 30 个 LiSi 样本。除 4Y-TZP 和 LiSi 外，所有样本均进行手工着色、预干燥，并分别在 1450°C（3Y-TZP、3Y-TZP、5Y-TZP 和一半 4Y-TZP）或 1580°C（另一半 4Y-TZP 和 4Y-TZP）下进行常规烧结或高速烧结。初始和经过 2、5、10、20、40 和 160 小时湿热老化（134°C，0.2 MPa）后测量透光率。初始和经过 160 小时湿热老化后（n=15）测试双轴抗弯强度。使用 Kolmogorov-Smirnov 检验、多变量分析和 1 方差分析与 Tukey HSD 事后检验、t 检验和线性混合模型进行计算（α=0.05）。
LiSi 显示出最高的半透明度，其次是 5Y-TZP、4Y-TZP、4Y-TZP、3Y-TZP 和 3Y-TZP。4Y-TZP 最不透明和哑光。与 LiSi 和常规烧结氧化锆材料相比，4Y-TZP 和 4Y-TZP 的透光率随老化时间的下降幅度更高。初始时，3Y-TZP 具有最高的抗弯强度，其次是 3Y-TZP、4Y-TZP 和 4Y-TZP。4Y-TZP 与 4Y-TZP 相当，但明显高于 5Y-TZP。LiSi 具有最低的双轴抗弯强度。湿热老化增加了 3Y-TZP 和 3Y-TZP 的双轴抗弯强度（P<.001），但降低了 5Y-TZP（P=.005）和 4Y-TZP（P<.001）的双轴抗弯强度。老化后，4Y-TZP 的抗弯强度与 4Y-TZP 相当（P=.06），高于老化后的 4Y-TZP（P=.019）。
手动着色、常规烧结的 4Y-TZP 对湿热老化的抗弯强度具有抗性。高速烧结抑制了手动着色 4Y-TZP 的颜色发展，但不影响其对湿热老化的抵抗力。工业预着色 4Y-TZP 的情况则相反。
