The effect of chlorhexidine mouthrinses on the human oral flora

The purpose of the present study was to examine the effect of chlorhexidine mouthrinses on the oral flora. Four students rinsed, twice daily, with 10 ml of a 0.2 per cent solution of chlorhexidine gluconate, and four students served as controls on a no oral hygiene programme. The number of bacteria in saliva was estimated by a cultural technique and impression preparations were used for the study of the bacteria on the gingiva and tooth surface. The controls showed a 300 per cent increase in bacterial counts during the experiment. In the chlorhexidine group the number of bacteria per ml saliva was reduced by 85 per cent, after 24 hours, reaching a 95 per cent reduction on day 5. An 85–90 per cent reduction was maintained throughout the experimental period. Impression preparations of the gingival area in the controls showed a heavier accummulation of bacteria than in the chlorhexidine group. In addition an increasing bacterial colonization of the tooth surfaces occurred in the controls throughout the experiment, but was never observed in the chlorhexidine group. Although the number of bacteria in saliva was markedly reduced, large numbers still persisted. It, therefore, appears unlikely that the inhibition of plaque formation is primarily the result of a reduction of the salivary flora.