CYCLIC VOLTAMMETRY OF DENTAL AMALGAMS

Objectives. This study used cyclic voltammetry to examine the effect o f the composition of dental amalgams on their electrochemical behavior , including reactions occurring outside of oral conditions. Methods. A malgams (residual mercury 47.5%) were prepared using two low-copper (3 wt% Cu) powders and five high-copper powders (40-80 wt% Ag, 12-30 wt% Cu) with and without zinc (1.5 wt%). Cyclic voltammograms were obtain ed at 37 degrees C in 1.0% NaCl scanning at 2 mV/s in the potential ra nge from -1.5 V to +0.8 V vs. Ag/AgCl. Results. During the anodic scan s, AgCl and Hg2Cl2 films were formed on all amalgams except the one wi th only 40 wt% Ag. In all high-copper amalgams, a prominent Cu (oxidat ion) peak was found at -0.1 V, indicating the release of copper during corrosion. Zinc affected the oxidation process for both low- and high -copper amalgams. When zinc was absent, a peak for Sn2+ oxidation appe ared at -0.4 V. When zinc was present, a Sn4+ oxidation peak was revea led at -0.6 V. In some amalgams, there was evidence of the selective c orrosion (pitting corrosion) of tin and copper. In the lowest silver-c ontent amalgam, no protective films were formed, which is indicative o f its poor corrosion resistance. As expected, in all the low-copper am algams, an extreme increase in current density was recorded immediatel y at 0 V, due to the release of tin from gamma(2). Significance. Cycli c voltammetry is useful for the rapid examination (less than an hour) of the electrochemical behavior of amalgams, specifically to obtain in formation on the formation of compounds and the sequences of electroch emical reactions.