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The Effect of Galvanic Corrosion on the Axial Tensile Strength of Amalgam

The improved clinical performance of high copper amalgam has led to the introduction of several different high copper amalgams. Some of these, which contain little or no zinc, such as non-zinc Dispersalloy* and Tytin § amalgam, are more cathodic in Ringer's solution than the conventional amalgam such as Aristaloyt and Zn-containing Dispersalloy amalgams (Table 1). The placement of different amalgam restorations or other metals, gold for instance, in opposition or interproximally in the mouth, could become a cause for concern if galvanic degradation were to occur. In the present investigation, a simple experiment was performed to test this hypothesis. Aristaloy amalgam was placed in intimate contact with one of the three different materials. They were: 1) non-zinc (0.02% Zn) Dispersalloy amalgam, 2) Type III dental gold plates, and 3) zinc-containing (0.8% Zn) Dispersalloy amalgam. The cathodic area was four times the anodic area. The amalgams were triturated and condensed according to manufacturers' directions and ADA Spec. #1 for dental amalgams in specially constructed dies, which produce dumbbell axial tensile specimens (Chen, C. P. and Greener, E. H., J Oral Rehab 3:323-327, 1976). The specimens for each combination were immersed in Ringer's solution at 370C for seven days in an open top flask. At the end of seven days, the flasks were checked, and the specimens were removed from the Ringer's solution. Axial tension tests on at least four specimens of each condition were then performed in air at room temperature.