Effects of chlorhexidine and iodine on in vitro plaques of Streptococcus mutans and Streptococcus sanguis.

Both chlorhexidine and iodine showed greater antimicrobial effect on in vitro grown S. mutans plaque than on plaque composed of S. sanguis. One treatment with iodine for 8 min inhibited the acid production of S. Mutans plaque whereas S. sanguis plaque required 20 min to be similarly affected. In contrast one treatment with chlorhexidine for up to 20 min did not completely inhibit the acid production of plaque of either microorganism. Repeated short term exposures increased the bactericidal effect of chlorhexidine but not that of iodine. The difference in antimicrobial effect between chlorhexidine and that of iodine on S. mutans and S. sanguis should be investigated in persons heavily infected by S. mutans.