Electrochemical impedance investigation of Ni-free Co-Cr-Mo and Co-Cr-Mo-Ni dental casting alloy for partial removable dental prosthesis frameworks

Abstract Statement of problem The pH level of the oral environment influences corrosion in dental materials. Corrosion behaviors of Co-Cr-Mo and Co-Cr-Mo-Ni alloys in different pH environments remain undetermined. Purpose The purpose of this in vitro study was to evaluate the surface properties and corrosion behaviors of Co-Cr-Mo and Co-Cr-Mo-Ni dental casting alloys in artificial saliva at pH values of 5.0 and 2.5. Material and methods Fifty specimens were divided into 2 groups according to the alloy composition. The surface compositions, hardness values, and microstructures of the alloys were measured before immersion in artificial saliva. The corrosion behaviors of the specimens in artificial saliva at pH values of 5.0 and 2.5 were studied using electrochemical impedance spectroscopy (EIS). The microstructures were examined again after a 7-day immersion test. Data were analyzed by a 1-way analysis of variance (ANOVA) test (α=.05). Results As expected, the relative levels of Co and Cr of the surface composition were higher in the Co-Cr-Mo alloy. The Co-Cr-Mo alloy had statistically higher surface hardness than the Co-Cr-Mo-Ni alloy ( P P P Conclusions The corrosion resistance of the Co-Cr-Mo alloy was better in the oral environment, especially at a low pH value.