Department of Prosthodontics and Periodontology, University of Campinas - Piracicaba Dental School, Piracicaba, SP, Brazil.
Department of Restorative Dentistry, Universus Veritas UNG, Guarulhos, SP, Brazil.
Dent Mater. 2019 Jul;35(7):1007-1016. doi: 10.1016/j.dental.2019.04.007. Epub 2019 May 4.
To evaluate the reliability and failure mode of zirconia-reinforced lithium silicate (ZLS) molar crowns of different thicknesses.
Monolithic ZLS molar crowns (0.5mm, 1.0mm, and 1.5 mm thickness) were modeled and milled using a CAD/CAM system (n = 21/group). Crowns were cemented on dentin-like epoxy resin replicas with a resin cement. The specimens were subjected to single load-to-failure test for step-stress profiles designing. Mouth-motion step-stress accelerated-life test was performed under water by sliding an indenter 0.7 mm lingually down on the distobuccal cusp until specimen fracture or suspension. Use level probability Weibull curves and reliability were calculated and plotted. Polarized-light optical microscope and scanning electron microscope (SEM) were used to characterize fracture patterns.
Irrespective of crown thickness, beta (β) values were higher than 1 and fatigue accelerated failures. While 0.5 mm ZLS crowns exhibited a significant reduction in the probability of survival at 200N, 300N and 400 N mission loads (69%, 41% and 19%, respectively), no significant difference was observed between 1.0 mm and 1.5 mm crowns. Both thicknesses have maintained the survivability at approximately 90%. Failure primarily comprised bulk fracture where radial cracks originated from the cementation surface beneath the indenter loading trail and propagated towards the cervical margin.
1.5 mm- and 1.0 mm-thickness monolithic ZLS crowns presented higher probability of survival compared to 0.5 mm crowns. Bulk fracture was the chief failure mode, regardless of thickness.
评估不同厚度氧化锆增强锂硅（ZLS）嵌体冠的可靠性和失效模式。
使用 CAD/CAM 系统对整体式 ZLS 磨牙冠（0.5mm、1.0mm 和 1.5mm 厚度）进行建模和铣削（每组 n=21）。使用树脂水门汀将冠粘接到类似于牙本质的环氧树脂复制品上。根据步进应力轮廓设计，对试件进行单载荷失效试验。在水下通过将压头向颊侧方向滑动 0.7mm 于远颊尖，对试件进行口腔运动步进应力加速寿命试验，直到试件断裂或停止。使用水平概率威布尔曲线和可靠性进行计算和绘制。使用偏光显微镜和扫描电子显微镜（SEM）来表征断裂模式。
无论冠厚度如何，β值均高于 1，且存在疲劳加速失效。当 0.5mm ZLS 冠在 200N、300N 和 400N 任务载荷下显著降低生存概率（分别为 69%、41%和 19%）时，1.0mm 和 1.5mm 冠之间未观察到显著差异。两种厚度均保持约 90%的生存能力。失效主要由体部断裂组成，其中径向裂纹从压头加载轨迹下方的粘结面开始，并向颈缘方向扩展。
与 0.5mm 冠相比，1.5mm 和 1.0mm 厚的整体式 ZLS 冠具有更高的生存概率。无论厚度如何，体部断裂均为主要失效模式。
