Electrochemical potentials of amalgam restorations in vivo

The potentials of 407 amalgam restorations have been determined in vivo. The measurements were performed with very high impedance equipment, and relative to a Ag/AgCl reference electrode. The readings varied from -23 mV to -595 mV, with 90% of the readings confined to within -127 mV to -431 mV and a mean value of -226.1 mV. Of the restorations, 394 were measured twice, and no significant difference could be found between the first and the second reading. During the study, eight new restorations were inserted. Their potentials varied from -180 mV to -565 mV, with a mean of -339.4 mV, which was significantly lower than that of the older restorations.