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Limited evidence supports the use of fluoride varnish for the prevention of dental caries in the primary dentition

L. Virginia Powell DMD, GPR .


Systematic Review Conclusion

Fluoride varnish may reduce the incidence of caries in the primary teeth of children younger than 6 years of age, but the evidence is inconclusive.

Critical Summary Assessment

Even though the majority of clinical trials support the conclusion that fluoride varnishes effectively prevent dental caries in primary teeth, the ideal formulation, the ideal treatment interval, the magnitude of effect, optimum treatment interval, varnish formulation, and overall safety need to be determined through higher quality clinical trials.

Evidence Quality Rating

Limited Evidence

Structured Abstract

Clinical Questions:

Does professionally applied fluoride varnish reduce the incidence of dental caries in the primary dentition of children younger than 6 years of age?

Review Methods:

The authors searched four databases for clinical trials that evaluated the effect of fluoride varnish on the incidence of caries in children younger than 6 years of age. They limited their search to articles published in English, Spanish, and Portuguese. Authors also reviewed Cochrane systematic reviews and their bibliographies. Unpublished reports were not included. Other inclusion criteria were randomized or quasi-randomized trial and published before December 2008. Trials of split-mouth design or trials that included the administration of other fluoride productswere excluded. The authors used consensus methods to finalize study inclusion, then qualitatively ranked the publications. They compared study results descriptively, but did not perform a meta-analysis.

Main Results:

The initial search yielded 513 articles, of which the authors selected eight studies (2,501 children aged 6 months to 5 years). The study periods varied from nine to 30 months with a median time period of 24 months. Most studies evaluated the effect of Duraphat (5 percent NaF), although one study tested Fluor Protector (1 percent Difluorosilano). The most frequent time interval for varnish application was every six months (n = 5). In each study the test and control groups presented with similar caries experience. However the caries prevalence at baseline between the individual studies differed significantly (range dmfs, control 0.00 to 9.70; test 0.00 to 9.90). The preventive fraction attributable to fluoride varnish varied from 5 percent to 63 percent. Seven of the eight studies reported a statistically significant effect of fluoride varnish in the prevention of decay in primary teeth. The study with the largest initial dmfs was the only one to not report a significant effect (P > 0.1).


Fluoride varnish may reduce the incidence of caries in the primary teeth of children younger than 6 years of age, but the evidence is inconclusive.

Source of Funding:

Not reported.


Importance and Context:

Multiple systematic reviews have shown that most clinical trials evaluating fluoride varnishes are flawed, and that more research is needed to confirm effectiveness and safety.1,2,3 These reviews, however, reach different conclusions. Some recommend fluoride varnish application for caries prevention; others conclude the evidence does not support their use. Study inclusion/exclusion criteria may explain this difference. Reviews that had strict criteria for included studies, such as excluding those that used a split-mouth design, those that administered concomitant fluoride products, and those that required clearly stated randomization methods, reported more convincing effects with fluoride varnishes than reviews with less strict criteria.

Strengths and Weaknesses of the Systematic Review:

The selection criteria for the individual studies were appropriate, and the evaluation of the underlying evidence was well conducted. A search of unpublished studies would have strengthened the review. Because of underlying heterogeneity, the authors did not perform meta-analysis. A graphic presentation of the individual studies would have helped illustrate their similarities and differences. Authors identified the weaknesses in the underlying evidence and made appropriate conclusions.

Strengths and Weaknesses of the Evidence:

The included studies demonstrated significant heterogeneity, especially with regard to baseline caries prevalence, extraneous fluoride exposure, and treatment regimens. The included studies were of questionable quality: none utilized a placebo treatment; seven were inadequately blinded; five did not discuss examiner calibration; seven did not adequately describe the randomization process; and the loss to follow-up, when reported, was significant. Two studies dropped children who developed decay during the study. Safety data were either unreported or incompletely reported; none of the studies reported the incidence of fluorosis. The conclusions may not apply to newer fluoride varnish formulations.

Implications for Dental Practice:

Fluoride varnishes may be easier to apply than other fluoride formulations, such as gels and foams which require suctioning equipment. This ease of application would allow fluoride varnish to be used within schools or medical facilities. Thus populations at higher risk for caries could be targeted. Because varnishes have very high concentrations of fluoride (23mg F-/ml), only a small amount of the product is required when administering to small children; therefore the actual ingestion of fluoride may be kept lower than with other modes of application. Because permanent teeth are still developing in younger children, minimizing the amount of fluoride ingestion may decrease adverse events like fluorosis. REFERENCES 1. Marinho CVV, Higgins JPT, Logan S, et al. Fluoride varnishes for preventing dental caries in children and adolescents. Cochrane Database Syst Rev 2002; Issue 1, art no.: CD002279. 2. Petersson, LG, Twetman, S, Dahlgren H, et al. Professional fluoride varnish treatment for caries control: a systematic review of clinical trials. Acta Odontol Scand 2004; 62: 170-176. 3. Rozier, RG. Effectiveness of methods used by dental professionals for the primary prevention of dental caries. J Dent Edu 2001; 65(10): 1063-1072.

Critical Summary Publication Date:


These summaries are not intended to, and do not, express, imply, or summarize standards of care, but rather provide a concise reference for dentists to aid in understanding and applying evidence from the referenced systematic review in making clinically sound decisions as guided by their clinical judgment and by patient needs. American Dental Association © 2019