Purpose The present study is aimed at examining the bond strength of cobalt-chromium (Co-Cr) metal frameworks, prepared through different techniques, to a single type of low-temperature porcelain system after the thermal aging process. Methods A hundred and twenty Co-Cr alloy framework specimens were prepared using conventional casting, CAD/CAM, and two commercially different laser sintering devices, and dental porcelain was applied to the specimens. A single type of dental porcelain (Kuraray Noritake Dental Inc., Tokyo, Japan) was applied to the specimens. After the subgroups were determined, half of the specimens were subjected to a thermal aging process. Bond strength of specimens was evaluated using a 3-point bending test. The surfaces of the fractured specimens were evaluated using a stereomicroscope. The metal-porcelain bonding area of samples randomly selected from 8 groups has been examined with SEM under ×1000 magnifications. Normality distribution of obtained data was examined using by a Kolmogorov-Smirnov test. The obtained data of the present study was statistically analyzed with a statistical package program (SPSS for Windows 22.0, Chicago, IL, USA). Results There was a statistically significant difference between CAD/CAM and the other three methods, and the bonding value of the CAD/CAM group was the highest among the groups. Besides, the bond strength between dental porcelain and 4 differently produced metal frameworks was high enough to surpass the acceptable threshold (>25 MPa) according to the ISO 9693. There was no statistically significant difference between thermal aging applied and nonapplied groups. Conclusions Based on this study, it could be shown that the metal-ceramic bond strength is dependent on the manufacturing method used, but it is independent of the thermal aging application. It was found that the bond strength values of all samples with and without thermal aging application exceeded the minimum acceptable value of 25 MPa recommended by the ISO 9693.

中文翻译：

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热老化过程后不同技术制造的牙瓷与钴铬金属框架之间的结合强度评估

目的 本研究旨在检查通过不同技术制备的钴铬 (Co-Cr) 金属骨架在热老化过程后与单一类型的低温瓷系统的结合强度。方法 使用传统铸造、CAD/CAM 和两种商业上不同的激光烧结设备制备 120 个 Co-Cr 合金框架标本，并在标本上涂上牙瓷。将单一类型的牙科瓷器（Kuraray Noritake Dental Inc.，Tokyo，Japan）应用于样本。在确定了亚组后，一半的样本进行了热老化过程。使用 3 点弯曲试验评估样品的粘合强度。使用立体显微镜评估断裂样品的表面。用 SEM 在 1000 倍放大下对 8 组中随机选择的样品的金属-瓷结合区域进行了检查。使用 Kolmogorov-Smirnov 检验检查获得的数据的正态分布。使用统计软件包程序（SPSS for Windows 22.0，Chicago，IL，USA）对本研究获得的数据进行统计分析。结果CAD/CAM与其他3种方法相比差异有统计学意义，其中CAD/CAM组的粘合值在各组中最高。此外，根据 ISO 9693，牙科瓷器和 4 种不同生产的金属框架之间的粘合强度足以超过可接受的阈值 (>25 MPa)。热老化应用组和未应用组之间没有统计学上的显着差异。结论 根据这项研究，可以证明金属-陶瓷的结合强度取决于所使用的制造方法，但与热老化应用无关。结果发现，所有样品的粘合强度值无论是否应用热老化都超过了 ISO 9693 推荐的最小可接受值 25 MPa。