Fluoride varnish was effective at reducing caries on high caries risk school children in rural Brazil.

Design: Placebo controlled randomised controlled trial (RCT).

Intervention: Recruited children were randomly assigned to either a treatment (5% NaF varnish, n = 198) or a control group (placebo, n = 181). Data on oral health habits and socio-demographic characteristics was collected from the children by trained interviewers. Diet information was collected using a seven day food frequency diary. Caries was assessed using the International Caries Detection and Assessment System (ICDAS).

Outcome Measure: The main outcome was decayed and filled surfaces (DFS) increment at 12 months.

Results: Two hundred and ten (55.4%) children having one or two applications of fluoride varnish or placebo were available for follow-up at 12 months. At the baseline examination, the children in the treatment and control groups presented with on average 6.2 and 5.6 DFS, respectively (P < 0.001). At 12 months, the children in the varnish group showed significantly lower DFS increments than did children in the control group (10.8 versus 13.3; P < 0.007), with a preventive fraction (PF) of 40% (95% CI: 34.3-45.7%; P < 0.0001).

Conclusions: The results of this study suggest that applications of 5% NaF varnish can be recommended as a public health measure for reducing caries incidence in this high-caries-risk population.