Influence of casting procedures on the corrosion resistance of clinical dental alloys containing palladium

The aim of this study was to compare the in vitro corrosion resistance in artificial saliva of two palladium–silver alloys (a Pd–Ag (Pors on 4) and an Ag–Pd (Palliag LTG)), with and without casting defects; 1 nickel–chrome alloy and 1 high-gold alloy, cast under recommended conditions, served as controls. For each of the palladium-based alloys, three specimens corresponding to three different casting conditions were used: under recommended conditions, with the use of a graphite-containing investment and crucible, and by reusing the sprues and sprue button. The electrochemical tests were run in Fusayama–Meyer artificial saliva. The open-circuit potential was recorded in mV/SCE at t = 24 h. Then, potentiodynamic polarization was performed to measure the polarization resistance (Rp) in kΩ cm2 and the corrosion current (icorr) in μA cm−2. Data were evaluated with one-way analysis of variance and multiple comparisons test (α = 0.05). In addition, each specimen was examined by scanning electron microscopy. Compared to the control alloys, the electrochemical experiments in artificial saliva indicated satisfactory corrosion resistance for the Pd–Ag and Ag–Pd alloys; these results are related to their high noble metal content and stable substructure. The Pd–Ag alloy displayed superior electrochemical properties to those of the Ag–Pd alloy regardless of the casting condition. The use of the graphite-containing crucible and investment during the cast process did not dramatically reduce the corrosion resistance values, but the reuse of sprues and the sprue button did. The optimal corrosion resistance values were obtained for the alloys cast according to the recommended conditions.