Background and purpose: Several factors are involved in caries prevention in children. One of the most effective factors is the appropriate use of fluoride. Fluoride induces its main effects in caries prevention through antibacterial effects and topical contact with enamel. In this study the inhibitory effects of sodium fluoride (NaF) and acidulated phosphate fluoride (APF) gels on cariogenic microorganisms concentrations (Streptococcus mutans and Lactobacillus) were compared using Quantitative Real-Time PCR.

Materials and methods: A single blind parallel clinical trial was performed in which plaque samples were investigated twice (before and after the use of fluoride). The plaque samples of 44 children were studied by quantitative Real Time PCR and the number of bacteria (lactobacilli and Streptococcus mutans) was counted in each sample. Then, APF gel (Fluoride 1.23% +0.98% phosphoric acid, pH 5.3) was randomly used for 22 children. All the teeth (primary and permanent) were covered with fluoride by applicator. For other children 2% NaF gel (neutral pH) were used. After the use of fluoride, the numbers of bacteria were measured again by quantitative real-time PCR. Finally, the variability of microorganisms before and after the intervention was compared. Mann-Whitney test was applied for data analysis using SPSS V.18.

Results: Significant reductions were observed in numbers of streptococcus mutans and lactobacillus after consumption of APF-gel (P<0.05).

Conclusion: The APF gel exhibited more caries-preventive effect compared to NaF gel and could be used to benefit children’s oral health.