Effect of toothbrushing with chlorhexidine gel on salivary microflora, oral hygiene, and caries

The effect of daily toothbrushing with 0.5% chlorhexidine-containing gel for 12 months was evaluated in a double-blind study in 37 dental students. The active gel did not markedly influence plaque formation, gingival conditions, or caries as compared with placebo gel treatment. Salivary bacterial counts were performed on subgroups of six subjects using chlorhexidine gel and on six using placebo gel. No differences in the effect of treatment on the microorganisms studied in the two subgroups could be detected except for S. sanguis. The percentage of this species decrease in the placebo group and increased in the chlorhexidine group. The difference became significant after 2 weeks. A tendency to a greater reduction of S. mutans noted in the chlorhexidine group was most marked in individuals who had high initial counts of this species. The proportion of S. sanguis, which could grow on chlorhexidinei-containing mitis salivarius medium, increased and after 12 months of chlorhexidine treatment averaged 34% of cultivable S. sanguis compared with 0.002% prior to treatment. The number of less sensitive S. sanguis decreased in the 12 months following termination of treatment. There was no observed tendency for the selection or proliferation of other streptococci, gram-negative rods, yeasts, or staphylococci.