Copper-inhibition of the growth of oral streptococci and actinomyces

Copper ions were found to inhibit the rate of growth in broth culture of Streptococcus mitis, Streptococcus mutans, Streptococcus salivarious, Streptococcus sanguis, Actinomyces viscosus and Actinomyces naeslundii. In all cases, 10^?3 M copper inhibited the rate of growth, whereas 10^?4 M and lower concentrations had little or no effect. At the concentrations used in mouthwashes one mode of action of copper ions is to reduce the rate of growth of oral bacteria in vitro.