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What the Evidence Says About Fluoride Varnish

The effectiveness of fluoride varnish in preventing caries is the focus of this practical review.

Oral health professionals are charged with preventing dental diseases, and some of the most common are, in theory, preventable. Dental caries—a microbiological disease involving the bacterial metabolism of fermentable dietary carbohydrates that leads to the mineral dissolution of tooth structure—is one of these preventable conditions. Because dietary sources of carbohydrates are key etiological components of the caries process, patients’ diet and self-care patterns are integral to successful caries management. Therapeutics can also play a strong role in caries prevention.1 For example, fluoride is one of the most clearly supported therapeutics for caries prevention in the ­scientific literature. ­Along with pit and fissure sealants, fluoride use remains paramount to reducing the risk of tooth decay.

Fluoride counteracts dental caries in at least three ways: it enhances the uptake of minerals, such as calcium and phosphate during remineralization; its own incorporation into the crystal structure of enamel increases resistance to acid attack; and fluoride ions can disrupt cariogenic bacterial activity.2 Fluoride derived from low-concentration sources like drinking water (0.7 ppm, for example) tends to exist in ionic form in oral reservoirs, such as saliva and plaque. High-concentration delivery methods, such as fluoride varnish, result in the formation of a calcium fluoride layer near the enamel surface. This layer remains ready for anticaries activity when pH levels drop.2


While formal United States Food and Drug Administration approval for fluoride varnish is to treat dentinal hypersensitivity, fluoride varnish has been used off-label for years in the management of dental caries. In its most common form, fluoride varnish is 5% sodium fluoride (NaF) suspended in a colophonium resin. A 5% NaF formulation consists of about 22,600 ppm fluoride, and the sticky resin allows the varnish to cling tenaciously to tooth surfaces. This potent combination contributes to fluoride varnish’s effectiveness in preventing dental caries.

Many major health care associations have made evidence-based recommendations for its use. The American Dental Association first published evidence-based guidelines for in-office fluoride treatments in 2006, with an update in 2013. For patients at risk for dental caries, the application of fluoride varnish or gel every 3 months to 6 months is recommended as an in-office treatment. Because its stickiness allows varnish to adhere to tooth surfaces—thus minimizing swallowing risk—the application of varnish is recommended for all age groups. The guidelines for varnish use are based on research conducted on patients age 18 and younger. These results are extrapolated to apply to older age groups.3

The knowledge of fluoride varnish’s anticaries efficacy extends beyond oral health professionals. In 2014, the US Preventive Services Task Force published its recommendations regarding the prevention of caries in children up to age 5. These recommendations support primary care clinicians such as pediatricians applying fluoride varnish to the primary teeth of infants or young children, starting with the eruption of the first deciduous tooth.4


When considering any clinical question, it is prudent to seek the highest level of scientific evidence relating to the topic of investigation. This is because high-level evidence is less prone to many, if not most types of unintentional bias. When faced with a clinical question, it’s important to discern what level of scientific rigor an article or report represents in its application to the clinical question. Answers to clinical questions supported by high-quality evidence are preferred.

When ranking the strength of scientific articles, the weakest evidence is expert opinion. As the name suggests, this type of paper or communication is simply the thoughts of a respected individual in the profession. Higher up on the scale of scientific strength are the various types of study designs, with randomized controlled trials (RCTs) ranking as the most rigorous. Systematic reviews, especially those that include meta-analyses, are at the top of the evidence-base pyramid. A systematic review basically employs a series of predetermined filters to sift through all existing studies regarding a specific clinical question, only retaining the most rigorous of scientific studies (eg, RCTs) for inclusion in the review. The remaining high-level studies are then statistically analyzed in an attempt to coalesce the data with the intention of drawing broad and valid conclusions that may be used to make clinical recommendations.5

The effectiveness of fluoride varnish in caries prevention has been evaluated at the highest level of evidence—the systematic review. The Cochrane Collaboration publishes systematic reviews for a wide range of health care topics, and it has published several systematic reviews on fluoride varnish. One review examined the effectiveness of fluoride varnish (vs placebo treatment) in preventing caries in children and adolescents. The review included 22 clinical trials, accounting for 12,455 participants in randomized scenarios. Key findings were an average 43% reduction in decayed, missing, and filled tooth surfaces (DMFT) in permanent teeth and a 37% reduction in DMFT in primary teeth.6 Regarding the prevention of early childhood caries, limited, moderate quality evidence exists for the use of fluoride varnish, according to a systematic review that included 33 studies.7

Another Cochrane review examined the use of fluorides to prevent white spot lesions during traditional orthodontic treatment. A number of fluoride modalities, ranging from toothpaste to varnish, were compared with placebo or no treatment. While the number of studies included in the systematic review was relatively small (three), the authors’ key finding was related to a study that applied fluoride varnish to teeth at every orthodontic adjustment visit. This study found a nearly 70% reduction in white spot lesion development in the groups that received fluoride varnish application.8

Besides preventing caries, fluoride varnish also appears to be effective in arresting caries. A systematic review published in the Journal of the American Dental Association explored this use of varnish. A total of 21 studies from a pool of 754 were analyzed, with five studies included in the review. Fluoride varnish was found to be effective in reversing incipient enamel caries lesions (p < 0.05), although the need for more research was suggested.9

Overall, the systematic reviews indicate that fluoride varnish is effective in preventing and perhaps arresting dental caries. Indeed, a recent conference paper assessed 39 of the available systematic reviews regarding various caries prevention strategies and affirmed fluoride varnish’s efficacy, determining that a moderate quality of evidence supports the use of fluoride varnish to prevent caries (contrasted with a low level of evidence supporting modalities like fluoride gel or mouthrinse).10 Thus, the continued use of fluoride varnish to prevent dental caries is both reasonable and evidence based.


Based on the best scientific evidence available, fluoride varnish is one of the most potent tools for the management of dental caries. The clear evidence supporting varnish’s use for the prevention of dental caries has led to its endorsement by leading professional organizations. If the aim of the health care professional is to prevent and successfully manage disease, then fluoride varnish has the scientific record to support its regular use in dental practice.


  1. Fontana M, Young DA, Wolff MS. Evidence-based caries, risk assessment, and treatment. Dent Clin N Am. 2009:53:149–161.
  2. Recommendations for using fluoride to prevent and control dental caries in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep. 2001;50:1–42.
  3. Weyant RJ, Tracy SL, Anselmo T, et al. Topical fluoride for caries prevention: Executive summary of the updated clinical recommendations and supporting systematic review. J Am Dent Assoc. 2013;144:1279–1291.
  4. Moyer VA. Prevention of dental caries in children from birth through age 5 years: US Preventive Services Task Force Recommendation Statement. Pediatrics. 2014;133:1102–1111.
  5. Straus SE, Richardson WS, Glasziou P, Haynes RB. Evidence-Based Medicine: How to Practice and Teach It. 4th ed. Edinburgh: Churchill Livingstone; 2010.
  6. Marinho VCC, Worthington HW, Walsh T, Clarkson JE. Fluoride varnishes for preventing dental caries in children and adolescents. Cochrane Database Syst Rev. 2013;7:CD002279.
  7. Twetman S, Dhar V. Evidence of effectiveness of current therapies to prevent and treat early childhood caries. Pediatr Dent. 2015;37:246–253.
  8. Benson PE, Parkin N, Dyer F, Millett DT, Furness S, Germain P. Fluorides for the prevention of early tooth decay (demineralized white lesions) during fixed brace treatment. Cochrane Database Syst Rev. 2013;12:CD003809.
  9. Lenzi TL, Montaner AF, Soares FZM, Rocha RO. Are topical fluorides effective for treating incipient carious lesions? A systematic review and meta-analysis. J Am Dent Assoc. November 5, 2015. Epub ahead of print.
  10. Twetman S. The evidence base for professional and self-care prevention—caries, erosion and sensitivity. BMC Oral Health. 2015;15(Suppl 1):S4.

From Dimensions of Dental Hygiene. February 2016;14(02):37–38.

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