Abstract
Selection Criteria
The authors conducted a comprehensive search of 7 electronic databases, in addition to gray literature, reference lists, and hand searches. Two independent reviewers extracted data of individual, cluster, or quasi-randomized controlled trials with a follow-up of at least 1 year. A third reviewer resolved any disagreement of study inclusion. After excluding nonrelevant studies or those that did not match the inclusion criteria, 19 studies were included in the systematic review and 17 in the meta-analysis. A total of 16,877 children were randomized, and 13,658 were included in the analyses.
Key Study Factor
The intervention of this systematic review included the application of fluoride varnish alone, or in association with an oral health program for preschoolers (<= 71 months). The age of the participants at the beginning of the studies ranged from 6 months to 5 years. The comparison groups were placebo, usual care, or no intervention. Short-term side effects (allergy, itch, discomfort) and long-term side effects (fluorosis) were also considered. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines on reporting were followed, and the Cochrane risk of bias tool was used for quality assessment.
Main Outcome Measure
The main measure of outcome used in this systematic review was the proportion of children and the number of primary teeth that developed new dentine caries at tooth and surface level. Meta-analysis at the individual level was performed using relative risk and at the tooth and surface levels using prevented fraction and weighted mean difference.
Main Results
Baseline caries prevalence ranged from 0% to 100% with dmft scores of 0-22.8 and dmfs scores of 0-6.57. The relative risks (RRs) statistically significantly favored fluoride varnish in all comparisons (fluoride compared with usual care: RR = 0.84; 95% = CI 0.72, 0.98; fluoride compared with no intervention: RR = 0.85; 95% CI = 0.73, 0.98), except when comparing fluoride with placebo; it was not statistically significant (RR = 0.86; 95% CI = 0.72, 1.03). The pooled RR was 0.86 (95% CI = 0.81, 0.95) with a fluoride varnish protective fraction of 12%. The prediction interval of the pooled RR was 0.68 to 1.14, which is not statistically significant. Pooled preventive fractions were dmfs = 24.15% (95% CI = 12.91, 35.38) and dmft = 31.13% (95% CI = 21.08, 41.18).
The results of the meta-regression showed a one-unit increase of mean baseline dmfs resulted in a 1% increase in the RR (95% CI = 0.99, 1.02), which is not statistically significant. The adjusted R-2 indicated that baseline caries explained 25.87% of variance between studies.
Conclusions
This systematic review and meta-analysis indicated that exposure to fluoride varnish had minimal difference in the risk of developing new dentinal caries in preschool-aged children. This may be due to excessive sugar intake despite multiple exposures to fluoride from different sources.