Corrosion of amalgams under sliding wear

Objectives. During mastication, dental amalgams are simultaneously subjected to corrosion by the oral environment and to a sliding-wear process by biting forces. In the present study, the effect of sliding wear on the corrosion behavior of two high-copper dental amalgams was investigated. Methods. An experimental apparatus was utilized that allows electrochemical testing under sliding-wear conditions. Corrosion potential measurements and anodic polarization scans were conducted in 0.1 M NaCl solution under sliding wear to characterize the behavior of two commercial, high-copper, single composition dental amalgams. In addition, long duration tests were conducted to assess possible corrosion and wear synergistic effects. Results. The results showed that sliding wear caused a sharp reduction in the corrosion potential, a significant increase in the corrosion rate and a decrease in the repassivation rate of both amalgams. These effects are due to the mechanical removal by the wear process of the surface protective film formed on dental amalgams. The simultaneous action of sliding wear and corrosion can also induce embrittlement that leads to cracking. Significance. The present evidence suggests that this cracking may be one of the major contributors to marginal failures of dental amalgam restorations.