Effect of chlorhexidine rinses on the morphology of early dental plaque formed on plastic film.

The effect of chlorhexidine on early plaque formation was studied in vivo in order to assess potential structural and quantitative changes. 3 subjects with healthy gingiva were used. Plastic films were applied to the buccal surfaces of the maxillary right first premolars and plaque was allowed to form for either 4 or 24 h. A single 1-min rinse with 0.2% chlorhexidine digluconate was used for the 4-h experiments, 1 min after film placement, whereas, for the 24-h experiments, an additional 1 min rinse was used at 12 h. In total, 62 films were obtained, half treated and half controls. These were processed for light and transmission electron microscopy, using standardized techniques for area sampling and cell counting. All plastic films were covered by a surface coating of acellular material in or on which bacteria, epithelial cells and leukocytes were observed. In the controls, an important increase in bacterial count was seen between 4 and 24 h, whereas the increase with chlorhexidine was slight. There were fewer bacteria in the chlorhexidine as compared to the water specimens, for both time periods. Many microorganisms in the chlorhexidine samples appeared to be undergoing degeneration with coagulated cytoplasm and disrupted cell walls.