Effect of a fluoride-containing chlorhexidine gel on bacteria in human plaque.

The effect on the plaque flora of a fluoride-containing chlorhexidine gel in mouthpieces was studied in seven subjects. Use of the gel during a 3-month period resulted in a change in the pattern of sensitivity to cholorhexidine in the plaque flora as displayed by determination of the minimal inhibitory amount (MIA) of the drug in agar diffusion assays. Three months after the use of gel was discontinued, the MIA value for plaque bacteria had returned to its original level. The relative proportions of S. mutans and S. sanguis in plaque changed during the chlorhexidine period. Thus S. mutans could not be detected in plaque samples after 3-month use of the gel, and the frequency of S. sanguis was altered.