Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University at Kiel, Germany.
Department of Cariology, Endodontology and Periodontology, University of Leipzig, Germany.
J Mech Behav Biomed Mater. 2018 Dec;88:231-237. doi: 10.1016/j.jmbbm.2018.08.017. Epub 2018 Aug 23.
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.
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.
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).
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.
本研究旨在通过光谱域光相干断层扫描（SD-OCT）评估人工老化对黏接于牙本质的薄型玻璃陶瓷牙釉质贴面的影响。此外，还研究了陶瓷贴面中的裂纹发展及其对陶瓷修复体行为的可能影响。
共制备 48 颗完整的上颌前磨牙，在牙本质上预备用于制作锂硅玻璃陶瓷块（IPS e.max CAD，义获嘉伟瓦登特，列支敦士登）的牙釉质贴面。所有修复体均使用树脂水门汀（Variolink Esthetic DC，义获嘉伟瓦登特）黏接。通过 SD-OCT（Telesto II，德国 Thorlabs GmbH）对标本进行三维和二维成像，然后在咀嚼模拟器中进行热动力学加载，在 10kg 的负载下进行 120 万次循环。人工老化后再次对标本进行 2D 和 3D 成像。最后，使用万能试验机进行准静态加载，直至失效，并随后进行显微镜检查以评估失效模式。对数据进行方差分析（ANOVA）检验，采用 Tukey 事后检验比较各组在 5%显著水平的差异。采用卡方检验（Chi-Square Test）和独立性 Fisher 精确检验（Fischer's Exact Test of Independence）检验名义变量之间的关联。
老化过程后，在黏固层或牙本质基底中未观察到任何变化或不规则现象。然而，在测试过程中，在与对颌牙接触的表面观察到陶瓷磨损。在 23%的标本中检测到裂纹的发展。裂纹并未影响断裂强度（p>0.05），但影响了失效模式（p≤0.001）。
光相干断层扫描允许对内牙和修复体进行简便且非侵入性的内部扫描。陶瓷中的裂纹发展不会影响修复体的断裂强度，但可能导致更具灾难性的失效类型。
