Effects of children’s toothpastes and mouth rinses on Streptococcus mutans, Streptococcus sanguinis and Lactobacillus acidophilus

Abstract

Objectives: As suppression of mutans streptococci in young children may prevent or delay colonisation of the oral cavity, tooth brushing with dentifrices containing anti-Streptococcus mutans activity may aid in preventing caries. The aims of this study were to compare the effects of children's toothpastes, mouth rinses, oral antiseptics and fluoride solutions on the growth of Streptococcus mutans and non-mutans bacteria (Streptococcus sanguinis and Lactobacillus acidophilus). Methods: The agar diffusion assay at neutral pH was used to determine bacterial growth inhibition. Zones of bacterial inhibition were measured using a micrometer gauge. Results: Dentifrices containing 1,450 ppm fluoride produced greater growth inhibition of both S. mutans and S. sanguinis than those with < 500 ppm. No inhibition was seen for pure solutions of sodium fluoride or sodium monofluorophosphate at fluoride concentrations up to 10%. Stannous fluoride exerted anti-bacterial effects at concentrations above 1%. Significant growth inhibition of both S. mutans and S. sanguinis was seen with sodium lauryl sulphate at 0.25% and with triclosan at 0.01%. The mouth rinses containing 2% chlorhexidine gluconate, 0.05% cetylpyridinium chloride and 0.05% sodium fluoride produced anti-bacterial 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. Of the combinations tested, 0.1% sodium fluoride with 5% povidone iodine produced synergistic anti-bacterial effects against S. mutans and S. sanguinis. The combination of 10% povidone iodine with 0.5% sodium hypochlorite produced additive anti-bacterial effects against L. acidophilus. Interference was seen in some combinations such as chlorhexidine with sodium lauryl sulphate, most likely through anion-cation reactions. However, 0.1% sodium fluoride when combined with 0.01% chlorhexidine did not interfere with the anti-bacterial effects of chlorhexidine alone 3 against S. mutans or S. sanguinis, but it reduced the anti-bacterial effects of cetyl pyridinium chloride alone against these bacteria. Conclusion: Sodium lauryl sulphate and triclosan are major bacterial inhibitory compounds in children's dentifrices. Mouth rinses containing chlorhexidine, sodium fluoride and cetyl pyridinium 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.