Effects of sustained-release chlorhexidine acetate on the human dental plaque flora.

The aim of this study was to determine the effect on the human dental plaque flora of a varnish containing chlorhexidine diacetate. The in vitro release of chlorhexidine acetate from the varnish preparation was relatively fast on the first day, followed by a substantial decline in the subsequent three days. In a clinical experiment, 26 volunteers were randomly distributed over four experimental groups. After a dental prophylaxis, the subjects were treated with a single application of a placebo varnish (group I), a fluoride varnish (group II), a chlorhexidine varnish (group III), or a fluoride-plus-chlorhexidine varnish (group IV). Saliva and pooled plaque samples from approximal surfaces were taken before (baseline) and one, two, three, four, and six weeks after the treatments. No suppression was found of total cultivable flora or S. sanguis after the experimental treatments. Application of the fluoride varnish did not suppress the A. viscosus/naeslundii or S. mutans levels in the dental plaque. Chlorhexidine suppressed A. viscosus/naeslundii until two weeks after the treatment. S. mutans was significantly suppressed until four weeks after a single chlorhexidine application. While in some subjects S. mutans was effectively suppressed over the whole experimental period, in others S. mutans recovered quickly. In five subjects in whom S. mutans recovered quickly, the dentition was treated twice with chlorhexidine varnish, with an interval of one week between the treatments. After two chlorhexidine treatments, S. mutans in saliva and on the teeth was suppressed more strongly than after a single treatment. However, the second chlorhexidine treatment could not prevent the return of S. mutans in the approximal areas to its original level.