Vital fluorescence to assess in vitro and in vivo the antibacterial effects of amalgams.

The aim of the present study was to establish an alternative methodology for testing the antibacterial effects of different amalgams. The vitality of mutans streptococci grown in vitro on various amalgam surfaces was monitored with a vital fluorescence staining technique using fluorescein diacetate and ethidium bromide. The in vivo effect of amalgam-non-gamma 2 fillings on the vitality of dental plaque was assessed with the same method and compared with samples originating from enamel. The median in vitro vitality of mutans streptococci was estimated as 70% on glass, 50% on Amalcapnon-gamma 2 and Sybraloy, 20% on Amalcap F and 10% on Neo-Silbrin. In vivo plaque vitality on enamel varied from 60 to 70%. In contrast, plaque sampled from non-gamma 2-amalgam surfaces revealed significant reductions in vitality with a minimum value of 25% of one day old supragingival plaque. The vital fluorescence technique was shown as an easy and quick method to assess the bactericidal effect against biofilm bacteria of dental materials in vitro as well as in vivo.

Antibacterial effects of amalgams on mutans streptococci in an in vitro biofilm test procedure.

Conflicting data continue to be presented in the literature regarding the antibacterial potential of various amalgam alloy compositions. The aim of the present study was to compare the antibacterial effects of 4 different amalgam samples on mutans streptococci using two in vitro test procedures. Glass and bovine enamel served as negative controls. The first test, one commonly used, consisted of immersing freshly prepared disks of the six materials in culture broth inoculated with mutans streptococci. Optical density measurements of the broth served to evaluate bacterial growth. This was followed by a biofilm technique which provided more intimate contact between the bacteria and specimen surfaces. With the exception of one high-copper lathe-cut amalgam, the first test revealed no antibacterial potential of the samples whereas the second test with the biofilm design elucidated significant differences in antibacterial potential between the amalgam alloy compositions and the controls. The biofilm technique, used in an in vitro test procedure, reflects the conditions of the oral environment more accurately than conventional test designs.