Surface characteristics and corrosion properties of selective laser melted Co–Cr dental alloy after porcelain firing

ObjectiveWe examined the surface characteristics and corrosion properties of selective laser melted (SLM) cobalt–chromium (Co–Cr) dental alloys before and after porcelain-fused-to-metal (PFM) firing.MethodsSamples were manufactured utilizing SLM techniques and control specimens were fabricated using traditional casting methods. The microstructure and surface composition were examined using metallographic microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Corrosion properties were evaluated using electrochemical impedance spectroscopy. Student's t-test was used to evaluate differences in numerical results of electrochemical corrosion tests between SLM and cast specimens before or after PFM firing. The results of electrochemical corrosion tests of the SLM and cast samples before and after firing were analyzed using one-way ANOVA.ResultsAlthough PFM firing altered the microstructure of the SLM specimens, they still exhibited a compact and homogeneous structure, and XPS analysis indicated that there were no significant differences in the surface composition of the specimens after firing. In artificial saliva at pH 5, the Rp value of the SLM specimens was 6.21 MΩ cm−2 before firing and 2.84 MΩ cm−2 after firing, suggesting there was no significant difference in electrochemical corrosion properties (P > 0.05). In artificial saliva at pH 2.5, the Rp value of the SLM group was 4.80 MΩ cm−2 before firing and 2.88 MΩ cm−2 after firing, again indicating no significant difference in electrochemical corrosion properties (P > 0.05). At pH 2.5, there was a significant difference in corrosion behavior between the cast and SLM groups, with the Rp value of the cast group being 0.78 MΩ cm−2 vs. 2.88 MΩ cm−2 for the SLM group.SignificanceThe improved post-firing corrosion resistance of SLM specimens provides further support for their use in prosthodontic applications, as the oral environment may become temporarily acidic following meals.