Objectives

The purpose of this study was to evaluate the effects of artificial aging on thin glass-ceramic occlusal premolar veneers, adhesively bonded to dentin, by examining the changes caused by artificial aging using spectral domain optical coherence tomography (SD-OCT). In addition, the development of cracks in the ceramic veneers and their possible influence on the behavior of the ceramic restorations were examined.

Methods

In total, 48 extracted sound upper premolars were prepared in the dentin for occlusal veneers milled from lithium disilicate ceramic blocks (IPS e.max CAD, Ivoclar Vivadent, Liechtenstein). All restorations were adhesively bonded using resin cement (Variolink Esthetic DC, Ivoclar Vivadent). Specimens were 3-dimensionally and 2-dimensionally imaged by SD-OCT (Telesto II, Thorlabs GmbH, Germany), then subjected to thermal-dynamic loading in a chewing simulator with 1,200,000 cycles at a load of 10 kg. Specimens were 2D and 3D imaged again after the artificial aging. Finally, they were subjected to quasi-static loading using a universal testing machine until failure occurred and later examined microscopically to assess the mode of failure. ANOVA test was performed for statistical analysis of data and Tukey’s post-hoc test was used to compare the groups at 5% significance level. Chi-Square Test and Fischer’s Exact Test of Independence were conducted to test the association between nominal variables.

Results

No changes or irregularities were observed in the cement layer or tooth substrate after the aging process. However, wear of the ceramic was noticed at the surface of contact with the antagonist during the test. The development of cracks was detected in 23% of the specimens. Cracks did not affect the fracture strength (p > 0.05) but influenced the mode of failure (p ≤ 0.001).

Significance

Optical coherence tomography allows an easy and non-invasive method to internally scan teeth and restorations. Development of cracks in the ceramic did not affect the fracture strength of the restorations but might lead to a more catastrophic type of failure.

中文翻译：

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SD-OCT人工老化和裂纹扩展对薄牙合板的影响

目标

这项研究的目的是通过使用光谱域光学相干断层扫描（SD-OCT）检查由人工老化引起的变化，来评估人工老化对粘结在牙本质上的薄玻璃陶瓷咬合前磨牙薄板的影响。此外，还检查了陶瓷贴面的裂纹发展情况及其对陶瓷修复体性能的可能影响。

方法

在牙本质中，共准备了48个提取的声音上前磨牙，用于从二硅酸锂陶瓷块（IPS e.max CAD，Ivoclar Vivadent，列支敦士登）碾磨的牙合板。使用树脂水泥（Variolink Esthetic DC，Ivoclar Vivadent）将所有修复体粘合在一起。通过SD-OCT（Telesto II，Thorlabs GmbH，德国）对样品进行3维和2维成像，然后在咀嚼模拟器中以120万次循环在10 kg的载荷下进行热力学载荷。人工老化后，再次对标本进行2D和3D成像。最后，他们使用通用测试机承受准静态载荷，直到发生故障，然后进行微观检查以评估故障模式。进行方差分析检验以对数据进行统计分析，并使用Tukey的事后检验比较显着性水平为5％的各组。进行卡方检验和菲舍尔独立性精确检验以检验名义变量之间的关联。

结果

时效处理后，在水泥层或牙齿基体中未观察到任何变化或不规则性。然而，在测试期间，在与拮抗剂接触的表面上注意到陶瓷的磨损。在23％的样品中检测到裂纹的发展。裂纹不会影响断裂强度（p> 0.05），但会影响破坏模式（p≤0.001）。

意义

光学相干断层扫描技术允许一种简单且无创的方法对牙齿和修复体进行内部扫描。陶瓷中裂纹的产生并不影响修复体的断裂强度，但可能导致更严重的破坏。