Objective: The aim of this study was to determine whether the Pd-Cu-based dental ceramic alloys possess any electrochemical characteristics distinguishable from that of other Pd-containing alloys. Of all Pd-containing alloys, this particular alloy group has been linked to frequent incidence of allergy and hypersensitivity reactions. Electrochemical corrosion may instigate these reactions.Methods: Four groups of alloys, Pd-Cu, Pd-Ga-(with and without Ag), Pd-Ag, and Au-Pd, were evaluated by traditional corrosion measurement techniques in a phosphated buffer saline solution at 20 o C. The electrochemical characteristics measured were: (1) 20h open circuit potential (OCP); (2) 20h corrosion rate (I c o r r ); and (3) anodic polarization (E-i) curves.Results: The OCP values (232+/-25mV) of the Ag-free Pd-Ga and Pd-Cu-based alloys were higher than and distinctly different from that (144+/-52mV) of the Ag-containing alloys. The I c o r r values of different alloys, despite varied compositions, were indistinguishable from one another. The E-i curves of all alloys were essentially similar, with the Ag-containing (>5wt%) alloys showing a subtle difference in their anodic slope within 100mV above their corrosion potentials.Significance: The OCP values of Pd-Cu alloys and the Ag-free Pd-Ga alloy are comparable to that reported for pure Pd (239+/-21mV), which indicates that during corrosion these alloys undergo dealloying and consequent Pd-enrichment on their surface. Such a condition is conducive to the release of allergenic Pd + + ions and offers a plausible explanation for the frequent incidence of hypersensitivity reactions associated with the Pd-Cu alloys. The OCP values in other alloys are attributed to dealloying followed by surface enrichment with Ag and/or Au and the possible formation of an insoluble AgCl surface film on the respective alloy surfaces. These events have the potential to suppress or prevent Pd + + ion release. Alloys showing these characteristics have seldom been linked to allergic reactions.