Based on the current concept of the caries-preventive mechanism of flu
oride, the fluoride concentration of some professionally applied fluor
ide preparations appears unnecessarily high. The aim of this trial was
to study whether reducing the fluoride concentration of the sodium fl
uoride varnish Duraphat(R) from the present 2.3% to 1.1% affects its c
linical 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% va
rnish for 3 years. Clinical and radiographical examinations were perfo
rmed 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 differe
nces 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. C
onsequently, it can be stated at a reasonable level of certainty that
if a difference in the efficacy of the two varnishes exists, it probab
ly is minute. Lowering the fluoride concentration of Duraphat is worth
considering at least when used for children.