Antimicrobial activity of amalgams, alloys and their elements and phases

Abstract

This in vitro study aimed to evaluate the antibacterial effect of amalgams, alloys, elements and phases against two cariogenic bacteria, Actinomyces viscosus and Streptococcus mutans. Test materials comprised: (i) commercial amalgams comprising Amalcap (Vivadent), Cavex Avalloy LC and DP (Cavex), Cupromuc (Merz), Fluoralloy and Synalloy (Dentoria); (ii) Ag–Cu alloy; (iii) γ, γ1, γ2 and Cu 6Sn 5 phases; (iv) pure metal samples and chloride solutions of copper, mercury, tin and zinc; and (v) aqueous sodium fluoride. Bacterial suspensions of each of the two bacteria were grown in the presence of the test materials for 24 h. Antimicrobial effectiveness was assessed by measuring reduction in optical density at 640 nm using a visible spectrophotometer. Cupromuc/Fluoralloy, non γ 2 amalgams and Amalcap displayed high, moderate and no antibacterial activity, respectively. Antibacterial effectiveness was not related to copper content. Whereas mercury, copper, Ag–Cu alloy, fluoride and zinc showed antibacterial activity (Hg>Cu>F>Zn), tin, gamma phases and Cu 6Sn 5 showed no such activity. Although the fluoride and copper solutions were most effective at 50 μg ml −1 concentration, their antibacterial action was still significant, albeit reduced, at 10 μg ml −1 concentration. This was not the case for mercury chloride which was just as effective at both concentrations. Our results show that although mercury and copper contribute significantly to the antibacterial properties of amalgams, a high copper content does not necessarily relate to high antibacterial effectiveness. These elements could be useful in conferring antibacterial properties to amalgam although their effects on host cells must be investigated.