The plaque‐inhibiting effect of copper amalgam

Abstract

In order to assess whether copper amalgam accumulates less bacterial plaque than silver amalgam, 14 copper amalgam cervical restorations were placed in 10 patients. Control silver amalgam fillings were placed in homologous teeth of the same jaw. To evaluate the amount of plaque, the stained areas on the amalgams were analyzed from photographs with a planimetric method. Further quantitative analyses of plaque growth on copper amalgam were carried out with microbiological methods, for which a new group of 10 patients was selected. Cervical cavities were prepared on both sides of the jaw. Specimens of copper amalgam and silver amalgam restorations were placed on opposite sides. The plaque was collected after 2 and 3 days and cultivated under aerobic and anaerobic conditions on blood agar plates and on Mitis Salivarius Agar. The results of both methods show a very significant inhibition of plaque growth on copper amalgam. These results were confirmed by scanning electron micrographs which showed that copper amalgam only had plaque on small areas. The plaque appeared in band formations arranged irregularly on the surface. Higher magnifications revealed a filamentous structure with predominating coccoid organisms. Scanning electron micrographs also showed that pellicle formation, which is considered to be necessary for bacterial adherence to the surface, took place on both amalgams.