Post-Graduate Program in Restorative Dentistry (Prosthodontics Unit), São Paulo State University (UNESP), Science and Technology Institute, São José dos Campos, São Paulo, Brazil.
Post-Graduate Program in Oral Science (Prosthodontics Unit), Faculty of Odontology, Federal University of Santa Maria - UFSM, Santa Maria, Rio Grande do Sul, Brazil.
Dent Mater. 2022 Jun;38(6):1060-1071. doi: 10.1016/j.dental.2022.04.021. Epub 2022 May 6.
This study aimed to evaluate the impact of mechanical fatigue cycling using the step-stress approach along with hydrothermaldegradation (134 ºC with a constant pressure of 2 bars for 20 h), and a novel intercalated hydrothermal/fatigue aging protocol on different aspects of the aging resistance of three generations of dental zirconias.
"Y"Z T (VITA), INCORIS "T"ZI (Dentsply Sirona) and "K"ATANA UTML (Noritake Kuraray) - 1st, 2nd and 3rd generation, respectively-, zirconia disks (N = 153), were divided into 6 groups (n = 3) for monotonic testing and 9 groups (n = 15) for mechanical fatigue testing, according to 3 proposed treatments for each zirconia: CF (control - only mechanical fatigue cycling); AF (aging in hydrothermal reactor at 134 °C for 20 h + mechanical fatigue cycling); AFA (Alternating protocol: 4 steps of 5 h of hydrothermal aging intercalated with mechanical fatigue cycling). Mechanical fatigue aging was performed according to the step-stress approach through biaxial flexural setup (piston-on-3-balls, initial strength: 100 MPa, step: 50 MPa/10,000, frequency: 20 Hz) until failure. Data were analyzed using Kaplan-Meier and Mantel-Cox test (α = 0.05), in addition to Weibull analysis. Fractured disks were analyzed in stereomicroscope, Scanning Electron Microscopy and X-Ray Diffraction.
Continuous hydrothermal and mechanical fatigue cycling decreased the fatigue strength of YAF group (516 ± 38 MPa), while the alternating protocol increased it (730 ± 58 MPa). KATANA UTML showed no differences for both treatments and did not undergo t-m phase transformation. The TAF group showed the highest fatigue strength (810 ± 76 MPa) and cycles for failure (147,000.00 cycles). The fracture origin for all specimens was on the tensile side in pre-existing defects.
INCORIS TZI zirconia had higher fatigue strength and survival rates after hydrothermal and mechanical fatigue aging. Although less resistant, KATANA UTML did not suffer chemical degradation.
本研究旨在评估使用阶梯式压力法结合湿热降解（在 134°C 下恒定压力 2 巴持续 20 小时）以及新型层间湿热/疲劳老化方案对三代牙科氧化锆耐老化性能的不同方面的影响。
“Y”Z T（VITA）、INCORIS“T”ZI（登士柏西诺德）和“K”ATANA UTML（诺里塔克库拉雷）——分别为第一代、第二代和第三代氧化锆——氧化锆圆盘（N=153），根据每种氧化锆的 3 种处理方法，分为 6 组（n=3）进行单调测试和 9 组（n=15）进行机械疲劳测试：CF（对照-仅机械疲劳循环）；AF（在 134°C 的热反应器中老化 20 小时+机械疲劳循环）；AFA（交替方案：4 个 5 小时的湿热老化步骤，中间插入机械疲劳循环）。机械疲劳老化通过双轴弯曲装置（活塞-3 球，初始强度：100 MPa，步长：50 MPa/10,000，频率：20 Hz）按照阶梯式压力法进行，直至失效。使用 Kaplan-Meier 和 Mantel-Cox 检验（α=0.05）以及威布尔分析对数据进行分析。对断裂圆盘进行立体显微镜、扫描电子显微镜和 X 射线衍射分析。
连续的湿热和机械疲劳循环降低了 YAF 组的疲劳强度（516±38 MPa），而交替方案则提高了其疲劳强度（730±58 MPa）。KATANA UTML 两种处理方法均无差异，且未发生 t-m 相变。TAF 组表现出最高的疲劳强度（810±76 MPa）和失效循环次数（147000.00 次）。所有样本的断裂起源均在拉伸侧的原有缺陷处。
INCORIS TZI 氧化锆在湿热和机械疲劳老化后具有更高的疲劳强度和存活率。虽然 KATANA UTML 的耐化学腐蚀性较差，但它并未发生化学降解。
