Effects of cations on the colloidal stability of some oral bacteria.

The colloidal stability of seven strains of oral bacteria was studied at various concentrations of mono-, di-, and multi-valent metal counterions in the suspending media. Alterations in the concentration and the valency of the counterions were shown to influence the colloidal stability of the bacterial suspensions, as determined by their rate and time of initial sedimentation. The observations were in general in agreement with the accepted theories for colloidal stability. The results support previously made suggestions that under certain experimental conditions oral bacteria behave like colloidal particles.