Effect of Surface Characteristics and Clinical Procedures on Corrosion Behaviour of Dental Amalgams

Abstract

The aim of this study was to evaluate and compare the effects of chemical composition, amalgam alloy powder particle shape, and clinical procedures such as finishing and polishing on the corrosion behaviour of dental amalgams. Four different types of commercial amalgam alloy with various chemical compositions and particle shapes (lathe cut, spherical, spheroidal) were studied. A special mould was used, and 21 samples were prepared from each type of commercial amalgam. After triturating and condensation, the samples of each type of amalgam were divided into three groups. Each group was finished using one of three procedures, namely carving, carving and burnishing, or carving, burnishing, and polishing. Structural characterisation by SEM was used to investigate the surface morphology of amalgam samples. Electrochemical potentiodynamic tests were performed in physiological solution in order to determine and compare the corrosion behaviour of the four amalgams as an indication of biocompatibility. Statistically significant differences were found between the mean corrosion current densities in the three different groups of each type of commercial amalgam. The polished samples all possessed the lowest corrosion current density, and the carved samples showed the highest corrosion current density (lowest corrosion resistance). This trend was not affected by the chemical composition of the commercial amalgams. It is concluded that clinical operations and procedures may influence tarnishing and corrosion of dental amalgam, surface plaque accumulation, and recurrence of tooth caries. The results also show that particle shape affects the surface roughness of dental amalgam restoration, and hence corrosion behaviour.