Subjects Children age 1 to 4 years (n = 100 in fluoride varnish arm and n = 100 in placebo varnish arm) attending a public health dental clinic for low-income families in Rio de Janeiro, Brazil were recruited in 2006 and 2007. Children were excluded if they received fluoride varnish in the previous 6 months, had 10 or more tooth surfaces with dentin caries, presented with a dental abscess, or had a systemic disease that could be aggravated by caries. At baseline, 96.5% of children were exposed to fluoridated water, 79.5% brushed their teeth with fluoridated toothpaste, and 23.4% had at least 1 carious tooth surface. Children were examined at baseline and again at 24 months, at which time 89/100 children in the topical fluoride group and 92/100 children in the placebo group were included in the final intention-to-treat analyses. Key Exposure/Study Factor There were 2 study arms: Fluoride Varnish Arm. Participants received 5% sodium fluoride varnish (Duraphat, Colgate Oral Pharmaceuticals, New York City, NY, USA) at baseline and subsequently every 6 months for 24 months (up to 4 fluoride varnish applications). Placebo Varnish Arm. The placebo varnish was provided by the same company that manufactured the fluoride varnish (Colgate Oral Pharmaceuticals). It was identical to the fluoride varnish except that it did not contain sodium fluoride. The varnish was applied to the participant's teeth by a trained undergraduate or graduate dental student. For participants with a full primary dentition, a pea-sized dose of varnish was dispensed onto a paper pad and applied to the teeth. For participants with 10 or fewer teeth, about one-half of a pea-sized varnish dose was used. The teeth were isolated with cotton rolls and dried with compressed air. The varnish was applied to all tooth surfaces with a disposable microbrush. Parents were instructed to avoid brushing the child's teeth and giving the child hard foods following varnish treatment. The fluoride and placebo varnish tubes were identical except that each type was labeled with letters (A or Z) by an individual not involved in the trial to maintain blinding. The dental examiners, students who applied the varnish, and study participants/parents were blinded to the varnish identity throughout the trial. Main Outcome Measure The primary outcome was the proportion of children who developed new dentin caries after 24 months. Dentin caries incidence was estimated by subtracting the total number of decayed, missing, and filled surfaces (d(3)mfs) at baseline from the total number of d(3)mfs at 24 months. Main Results After 24 months, a larger proportion of children in the placebo varnish group (46.7%) had new dentin caries than children in the fluoride varnish group (35.9%), although the difference was not statistically significant (difference: -10.8; 95% confidence interval [CI]: -24.9, 3.3; p = 0.14). Conclusions Application of fluoride varnish every 6 months for 2 years does not prevent primary tooth dentin caries incidence more effectively than a placebo varnish.
