Objective

The goal of this study was to investigate the fatigue life, failure modes, and stress distribution of partial ultrafine restorations for posterior teeth in different ceramics.

Methods

Sixty standard tabletop preparations in epoxy resin G10 received lithium-silicate-based zirconia-reinforced (ZLS) or hybrid ceramic (PIC) restorations in 0.5- or 1-mm thickness bonded with resin cement. The same cycling protocol was applied for all specimens, which consisted of 5000 cycles at 200 N, followed by 450-N cycles until the specimens’ fracture or the suspension of the test after 1.5 × 10⁶ cycles. Axial load was carried out with a 4 Hz frequency in Biocycle V2 equipment (Biopdi, São Carlos, SP), with samples immersed in water. The presence of cracks and/or fractures was checked every 2.5 × 10⁵ cycles, and the survival analysis was performed with the number of cycles in which each specimen failed. All specimens were evaluated by stereomicroscopy and scanning electron microscopy (SEM). After data tabulation, Kaplan–Meier and Mantel–Cox (log-rank test) analyses were performed, followed by multiple pairwise comparison, all with a significance level of 5%, and Weibull analysis. Through three-dimensional finite element analysis, stress distribution and maximum principal stresses in the posterior occlusal veneers were evaluated by comparison of different types of substrate (G10, enamel/dentin, enamel), thicknesses, and ceramic materials.

Results

Zirconium-reinforced lithium silicate restorations with 0.5-mm thickness (ZLS.5) showed lower fatigue strength compared with that of 1.0-mm hybrid ceramic restorations (PIC1), and both were similar to other restorations (PIC.5 and ZLS1) (log-rank test, χ² = 11.2; df = 3; p = 0.0107 < 0.05). ZLS groups presented random defects that culminated in fracture, whereas PIC groups presented defects that increased with mechanical fatigue after some cycling time. Stereomicroscope images show radial cracks due to the translucency of the material. There was no damage caused by the applicator. MPS (maximum principal stress) distributions were similar for the different substrate types, but the highest modulus of elasticity showed slightly lower stress concentration.

Significance

PIC is more likely to be used in thinner thickness than indicated by the manufacturer, with fatigue strength similar to that of thicker ZLS restorations.

中文翻译：

---

超细台式陶瓷修复体的疲劳行为

客观的

这项研究的目的是研究不同陶瓷材料中后牙局部超细修复体的疲劳寿命，破坏模式和应力分布。

方法

环氧树脂G10中的六十种标准台式制剂接受了以0.5毫米或1毫米厚度的硅酸锂基氧化锆增强（ZLS）或混合陶瓷（PIC）修复体，并与树脂水泥粘合在一起。对所有样品都采用相同的循环规程，包括200 N下的5000个循环，然后进行450-N个循环，直到1.5×10 ⁶个循环后样品断裂或测试暂停。在Biocycle V2设备（Biopdi，圣卡洛斯，SP）中以4 Hz的频率进行轴向加载，并将样品浸入水中。每2.5×10 ⁵检查一次裂纹和/或裂缝的存在循环，并以每个样本失效的循环次数进行生存分析。所有样品均通过立体显微镜和扫描电子显微镜（SEM）进行评估。在数据列表之后，进行Kaplan–Meier和Mantel–Cox（对数秩检验）分析，然后进行多对成对比较（显着性水平均为5％）和Weibull分析。通过三维有限元分析，通过比较不同类型的基底（G10，牙釉质/牙本质，牙釉质），厚度和陶瓷材料，评估后牙合板中的应力分布和最大主应力。

结果

厚度为0.5毫米的锆增强硅酸锂修复体（ZLS.5）与1.0毫米混合陶瓷修复体（PIC1）相比具有较低的疲劳强度，并且两者均与其他修复体（PIC.5和ZLS1）相似（对数）秩检验，χ ²  = 11.2; DF = 3; p = 0.0107 <0.05）。ZLS组呈现出随机的缺陷，最终导致断裂，而PIC组呈现出的缺陷随着一段时间的机械疲劳而增加。立体显微镜图像显示由于材料的半透明性导致的径向裂纹。没有由涂药器造成的损坏。不同基材类型的MPS（最大主应力）分布相似，但是最高的弹性模量显示出较低的应力集中。

意义

PIC可能比制造商指定的厚度更薄，疲劳强度类似于较厚的ZLS修复体。