Caries-preventive effect of fluoride varnish with different fluoride concentrations

Based on the current concept of the caries-preventive mechanism of fluoride, the fluoride concentration of some professionally applied fluoride preparations appears unnecessarily high. The aim of this trial was to study whether reducing the fluoride concentration of the sodium fluoride varnish Duraphat from the present 2.3% to 1.1% affects its clinical efficacy. A total of 274 children aged 12-14 years and having high past caries experience were randomly divided into two groups. The participants received 3 annual applications of either 2.3% or 1.1% varnish for 3 years. Clinical and radiographical examinations were performed at baseline and at the end of the follow-up. The mean total DMFS increments of the 2.3% and 1.1% varnish groups were 5.5 (SD 5.7) and 5.7 (5.3), respectively, when initial caries was excluded, and 14.3 (12.0) and 14.9 (12.9) when initial caries was included. The differences were statistically non-significant. There were no significant differences in the surface-specific DMFS increments between the groups either. The 95% confidence interval for the difference between the groups in total mean DMFS increment (initial caries excluded) was calculated at -1.21 to + 1.54, i.e. at this level of confidence at most 0.5 surfaces per year would have been saved using the more concentrated varnish. Consequently, it can be stated at a reasonable level of certainty that if a difference in the efficacy of the two varnishes exists, it probably is minute. Lowering the fluoride concentration of Duraphat is worth considering at least when used for children.