Evaluation of the Bond Strengths between Dental Porcelainand Cobalt-Chromium Metal Frameworks Manufactured withDifferent Techniques after the Thermal Aging Process

The present study is aimed at examining the bond strength of cobalt-chromium (Co-Cr) metal frameworks, preparedthrough different techniques, to a single type of low-temperature porcelain system after the thermal aging process.Methods.Ahundred and twenty Co-Cr alloy framework specimens were prepared using conventional casting, CAD/CAM, and twocommercially different laser sintering devices, and dental porcelain was applied to the specimens. A single type of dentalporcelain (Kuraray Noritake Dental Inc., Tokyo, Japan) was applied to the specimens. After the subgroups weredetermined, half of the specimens were subjected to a thermal aging process. Bond strength of specimens was evaluatedusing 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×1000magnifications. Normality distribution of obtained data was examined using by a Kolmogorov-Smirnov test. The obtaineddata 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 thebonding value of the CAD/CAM group was the highest among the groups. Besides, the bond strength between dentalporcelain 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 nonappliedgroups.Conclusions. Based on this study, it could be shown that the metal-ceramic bond strength is dependent on themanufacturing method used, but it is independent of the thermal aging application. It was found that the bond strengthvalues of all samples with and without thermal aging application exceeded the minimum acceptable value of 25 MParecommended by the ISO 9693.