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One conventional amalgam and two amalgams with higher copper content were stored in contact with various dental casting alloys in phosphate-buffered 0.9% NaCl solution, pH 6, at 37 degrees C during 35 weeks. Every 7 weeks the solutions were changed, and the corrosion was measured by analyzing the solutions for the amount of Cu, Zn, Sn, Hg, Ag, Co, Cr, and Ni. In the first 7 weeks the amalgams immersed in contact with acrylic or Co-Cr alloys released small amounts of elements, whereas the release was larger when the amalgams were in contact with the gold alloys. During the rest of the experiment the release of elements tended towards the same level, independent of the casting alloy in contact. In general, the high copper amalgams released more corrosion products into the solutions than the conventional one. The release of corrosion products was strongly pH-dependent. Changing the solutions more often and saturating the solutions with oxygen decreased the amounts of Hg and Ag released.

A 69-year-old white female presented bilateral lesions of the oral mucosa possibly related to electrogalvanism. The lesions were histologically characterized as lichen planus and as mild epithelial dysplasia on the left and right sides, respectively. They disappeared after removing amalgam restorations opposing the lesions. Epicutaneous patch tests and lymphocyte-transformation tests showed that the patient suffered from a contact allergy to mercury compounds, indicating this as a mechanism by which electrogalvanism may induce lesions of the oral mucosa.

Fifty-four patients referred to the Faculty of Odontology, University of Umeå, for investigation regarding “oral galvanism” were subjected to a general oral investigation. In addition the following parameters were studied: the highest calculated current between two metallic restorations in contact and the electrogustometrically determined threshold value for each person. No differences were found regarding these two parameters between the patients and a control group consisting of 15 persons. However, the general oral investigation had revealed that a relatively large number of patients had periodontal conditions which, together with mucous membrane affections and hypersensitivity reactions could explain some of the unpleasant sensations which bothered them. Furthermore, the results of a stomatognathic investigation which will be presented separately revealed that about three fourths of the patients needed treatment for their stomatognathic and/or temporomandibular joint conditions.

Galvanism is seldom mentioned to the dental student, yet nearly every dentist alters a patient’s galvanic current every time he treats him. Galvanism is electrical current produced by placing dissimilar metals inan electrolyte. Saliva is the electrolyte. The dental dissimilar metal list is seemingly inexhaustive. We place copper, tin, zinc, mercury, silver, gold, platinum, irridium, indium, paladium, cobalt, chromium, nickle and baryllium into this electrolyte. A battery is produced. Electrical current is generated. Electricity doesn’t just exist. It is the simultaneous biproduct of a chemical reaction between the various phases of metallic interaction in the mouth. As electrical current is generated, various ions of these metals are emitted into the saliva. Many of these metals, or their corrosion products, are known toxins. Among them is mercury.

Galvanic corrosion of amalgam, induced by contact with a type IV dental casting gold alloy, was determined under simulated oral conditions in an electrochemical cell. The effect of a pellicle layer formed by 1 h exposure to saliva in the oral cavity was determined. Pellicle on the amalgam had no effect on the maximum corrosion rate or the 2 h corrosion charge, whereas pellicle on the gold alloy substantially reduced both these parameters of the conventional low-copper amalgam; the corrosion of the high-copper amalgam was less and was not influenced by pellicle formation.

Base metal alloys which contain nickel are not new to dentistry. For the past 25 years, these alloys with nickel content as high as 73.5 percent, have been used to fabricate denture bases and removable partial dentures.