Comparative analysis of the surface properties and corrosion resistance of Co-Cr dental alloys fabricated by different methods

The complex oral environment leads to the corrosion of dental alloy materials and the release of metal ions that may have a negative impact on health. Digital manufacturing is increasingly being used in dentistry, but whether digitally manufactured prostheses have better resistance to corrosion than traditional cast prostheses is unclear. The purpose of this in vitro study was to determine the surface properties and corrosion resistance of dental cobalt-chromium (Co-Cr) alloys fabricated by lost-wax casting (CAST), selective laser melting (SLM), and computer numerical control milling (CNC). The surface characteristics of the specimens were analyzed via scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS), metallurgical observation, and X-ray diffraction (XRD). For corrosion resistance, the specimens were immersed in artificial saliva at a pH 2.3 and 6.8 for 1, 4, and 7 weeks. Then, inductively coupled plasma-mass spectrometry (ICP-MS) was used to detect the main metal ion. Electrochemical impedance spectroscopy (EIS) was conducted based on a 3-electrode system to assess the electrochemical corrosion resistance. An ANOVA test was used to evaluate statistically significant differences among the groups (α=.05). The SLM and CNC specimens showed more homogenous microstructures, less ion release at different times and pH, and more charge transfer resistance than CAST specimens. Compared with casting, SLM-printing and CNC-milling have advantages in terms of surface properties and corrosion resistance.