Corrosion Characteristics of Ni-Cr and Co-Cr Alloy Used as a Dental Prosthesis and Its Adhesion to Porcelain

By using Ni-Cr and Co-Cr alloys, porcelain fused to metal (PFM) samples were prepared to examine the interface and the surface corrosion behavior. The potentiodynamic polarization analysis showed that the corrosion current density of Co-Cr alloy ( 1.61×10⁻⁶A/cm² ) was three times lower than that of Ni-Cr alloy ( 4.83×10⁻⁶A/cm² ) at room temperature. A dental prosthesis consisting of the porcelain fused to Ni-Cr alloy extracted from a patient after approximately four years of usage was examined to assess its resistance to corrosion. OM and SEM images of the metal part revealed a typical pitting corrosion. As compared to porcelain fused to Ni-Cr alloy having a thick layer ( ~10μm ) of oxide at the interface, a relatively thin oxide layer (less than 5μm ) was formed on Co-Cr alloy, indicating that the interface between Co-Cr alloy and porcelain may have a better adhesion strength than the interface between Ni-Cr alloy and porcelain.