Methods: The agar diffusion assay was used to examine the antibacterial activity of combinations of oral antiseptics and fluoride solutions. Zones of bacterial inhibition were measured using a micrometer gauge.
Results: The mouth rinses containing 2% chlorhexidine gluconate, 0.05% cetylpyridinium chloride and 0.05% sodium fluoride produced antibacterial effects against S. mutans, S. sanguinis and L. acidophilus. Of the pure compounds, 0.01% chlorhexidine produced the greatest zone of growth inhibition against S. mutans; while, pure solutions of sodium fluoride or sodium monofluorophosphate, at concentrations up to 10%, had no antibacterial effects.
The addition of 0.1% sodium fluoride to 0.01% cetylpyridinium chloride interfered with the antibacterial effects of pure 0.01% cetylpyridinium chloride against S. mutans and S. sanguinis (p<0.001). The combination of 0.1% sodium fluoride with 10% povidone iodine produced synergistic antibacterial effects against S. mutans and S. sanguinis compared to either compounds used alone (p<0.001). The combination of 10% povidone iodine with 0.5% sodium hypochlorite interfered with the antibacterial effects of the pure compounds against S. mutans and S. sanguinis and resulted in no bacterial inhibition. This combination, however, produced an additive antibacterial effect against L. acidophilus compared to pure 0.5% sodium hypochlorite and 10% povidone iodine used alone (p<0.01 and p<0.001, respectively).
Conclusion: Mouth rinses containing chlorhexidine, sodium fluoride and cetylpyridinium chloride have growth inhibitory effects against Streptococcus mutans, Streptococcus sanguinis and Lactobacillus acidophilus. The combinations of povidone iodine with sodium hypochlorite and povidone iodine with sodium fluoride produced additive and synergistic effects respectively.