Untreated tooth decay can diminish a child’s ability to eat, speak, learn, and play.¹ Prevalences of lifetime and untreated tooth decay in the US are, respectively, 23.3% and 10.4% in the primary dentition of children aged 2 to 5 years and 56.8% and 16.6% among adolescents aged 12 to 19 years.² Untreated tooth decay is significantly higher for non-Hispanic Black (20.4%) and Mexican American (20.8%) adolescents than for non-Hispanic White (15.6%) adolescents.² Reducing the prevalence of lifetime and active tooth decay in youth are national health objectives.³

Fluoride varnish (FV) treatments to prevent tooth decay (dental caries) are provided off-label in the US.⁴ There is strong evidence that FV prevents caries—about 37% of caries in the primary and 47% in the permanent dentition.⁵ Delivery of FV in dental offices is recommended for children at elevated caries risk by the American Dental Association⁶ and is a CMS quality measure.⁷ The United States Preventive Services Task Force (USPSTF), which makes recommendations for preventive services delivered in primary care settings, also recommends FV treatments for children from the time the first tooth erupts to age 5 years⁸ but found insufficient evidence for youth aged 5 to 17 years.⁹ Receipt of topical fluoride, which includes FV, during annual dental visits is low—less than 18% of children from families with lower incomes received a treatment in 2013–2014.¹⁰ There are also significant disparities in receipt by race and ethnicity.¹⁰

Schools can be an important setting for delivery of FV. In 2022, about 70% of state oral health programs reported having at least 1 school FV delivery program (SFVDP).¹¹ These programs apply FV (5% sodium fluoride) to the teeth of children attending preschools and schools either onsite (school-based) or at offsite venues (school-linked).¹² Schools with high percentages of free/reduced meal program participation are typically prioritized. FV can be applied by dental and medical professionals and trained lay workers. Other services may include caries risk assessment, oral hygiene instruction and supplies, oral health education, and referrals for dental care.

To date, there have been no systematic reviews on the effectiveness of SFVDPs in preschool through high school. This systematic review conducted for the Community Preventive Services Task Force (analytic framework available at Oral Health: School Fluoride Varnish Delivery Programs | The Community Guide) addresses the following questions:

How effective are SFVDPs:

In increasing the receipt of FV applications?

Community Guide systematic review methods were used.^13–15 Centers for Disease Control and Prevention librarians developed the search strategy (available at: Oral Health: School Fluoride Varnish Delivery Programs | The Community Guide) for the following databases: Medline (OVID); Embase (OVID); Global Health (OVID); Cochrane Oral Health Trial Registry; Cochrane Central; Scopus; ERIC (ProQuest); and CINAHL (EBSCO). The team searched for studies published from the database inception through December 31, 2023. The strategy searched for all studies with MeSH terms for FV and children. IRB approval was not required for this study.

Studies were included addressing any of the review questions if participants were recruited and/or provided FV in a school (preschool through high school) located in a World Bank designated high- or upper-middle income country.¹⁶ Guide methods typically restrict inclusion to high-income countries but due to the presence of some RCTs evaluating SFVDP in upper-middle income countries that were included in other reviews,^{5, 8} this criteria was relaxed but findings were presented separately for the 2 income categories.

Studies were excluded if consisting solely of youth with medical or oral conditions that would likely preclude them from participation in a school program; having less than 9-month follow-up period; not published in English; not having a comparison; or not delivering varnish with 5% sodium fluoride. For studies evaluating effectiveness in preventing caries, the comparison group could be negative controls receiving usual care with no additional interventions or with other preventive interventions such as oral health education that were also provided to the intervention arm.

Teams of two reviewers independently screened search results and abstracted qualifying studies (Summary Evidence Table - Oral Health: School Fluoride Varnish Delivery Programs). Differences were reconciled first by the 2 abstractors, with unresolved differences brought to full review team. Reviewers considered the following when evaluating quality of study execution: description of the intervention, population, and sampling frame; assessment of intervention exposure and outcome reliability; description and use of appropriate analytic methods; attrition (i.e., whether >20% of the study population was lost to follow-up); and ability to control for confounding or biasing factors. Reviewers described studies as having good (0–1 limitations), fair (2–4), or limited (>4) quality of execution. Studies with limited quality of execution were excluded from the analyses.

Two caries outcomes were examined—initiation and progression (decay in enamel progressing to dentin) or regression (remineralization or arrestment of decay). Studies varied by how they defined caries initiation. When possible, caries measures that included non-cavitated (incipient) decay were used. Caries measures included both number of affected teeth/surfaces per child (continuous) and presence of caries (dichotomous) measured at the tooth or child level. FV receipt outcomes included whether student received FV and number of annual applications per student.

Community Guide reviews include a wide variety of study designs (e.g., experimental studies with allocated control groups, observational studies with concurrent or historical control groups) and frequently summarize review findings using descriptive statistics such as the median and range or interquartile range of effect sizes.¹³ Because of the heterogeneity in caries measures, type of teeth included in measure, and different study designs, effectiveness was estimated using the relative risk ratio (RR equals change in intervention group relative to change in comparison group) for studies with a concurrent control group. Effectiveness was summarized across studies using the median RR, the mid-point of the series of estimates, and interquartile interval (IQI). In synthesizing evidence, only 1 effect measure was used per study. The following ranking criteria were used in selecting the reported measure from a study: 1) longest follow-up period; 2) highest application frequency; 3) caries measured at surface over tooth level; and 4) increment (change in mean caries) over incidence (change in prevalence). The team adhered to the convention of synthesizing caries prevention evidence separately for primary and permanent teeth.⁵ Stratified analyses were performed for both types of dentition to examine applicability of findings to different categories of setting, population, intervention, and study design characteristics (applicable if upper value of IQI<1.00; likely applicable if median RR<1.00 and IQI including 1.00; evidence gap if no studies or one study with RR≥1.00 and not applicable if 2 or more studies and median RR≥1). Findings summarized for both dentitions were deemed not applicable if there was a finding of non-applicable for at least 1 category of dentition; evidence gap if not found inapplicable and at least one evidence gap, and applicable/likely applicable, otherwise.

This systematic review consisted of studies primarily conducted in low SES communities located in high or upper-middle income countries among children at elevated caries risk. Review findings on the effectiveness of SFVDPs in preventing caries initiation and regression; in achieving meaningful rates of participation; in increasing the number of FV treatments received; and in reducing disparities in the onset of tooth decay by income and other social determinants of health served as the basis for the CPSTF recommendation to deliver FV in schools based on strong evidence of effectiveness in preventing dental caries. (The Community Guide available at:: Oral Health: School Fluoride Varnish Delivery Programs | The Community Guide)

This review found SFVDPs to be effective across a wide range of setting, population, and intervention characteristics. Most of the effectiveness data, however, were for students at elevated caries risk living in low socioeconomic areas, indicating applicability of findings to US programs that prioritize these populations. There was no evidence to suggest that FV effectiveness varied by type of provider. Fluoride varnish was effective in preventing caries in both the chewing and non-chewing surfaces of teeth, suggesting that school programs could deliver FV as a stand-alone or adjunct service to dental sealants that primarily protect against decay occurring in the chewing surfaces.

SFVDPs typically screen children for untreated caries and refer children for needed care.⁴⁸ The review team postulated as potential benefits that participation in these programs could increase the number of children with an ongoing relationship with a dentist or dental home, ultimately resulting in reduced unmet treatment needs and improved quality of life. No studies in this review, however, evaluated these outcomes. The review team also postulated that SFVDPs could contribute to improved school performance. Although this review did not locate direct evidence related to school performance, the broader literature indicates that reducing untreated caries improves academic performance and reduces absenteeism.^49–51

Similar to the USPSTF review, only minor complaints were found associated with SFVDP participation. Among included studies, none examined systemic exposure to fluoride from SFVDP participation. The USPSTF noted that systemic exposure to fluoride from FV is likely lower than exposure from other topical fluoride modalities.⁸ One study⁵² included in that review found that among school-aged children, prevalence of dental fluorosis (condition of enamel resulting from systemic exposure to fluoride while teeth are developing) did not statistically differ between children receiving FV during tooth development (27%) and similar children never receiving FV (35%).

Many state Medicaid programs reimburse for FV and sealants delivered in schools, but low Medicaid reimbursement⁵³ and care that is not reimbursed²⁶ can hinder program implementation and sustainability. Medicaid reimbursement policy regarding who can bill for preventive dental services and who can deliver them may pose greater barriers for non-dental providers. In most states, Medicaid only allows medical providers who are physicians or nurses with advanced degrees, i.e., nurse practitioners, to bill for FV application and typically does not reimburse for FV delivered to children older than age 6 years.⁵⁴ Although most states allow medical providers to delegate delivery to other types of health professionals (e.g., medical assistants, registered nurses), in a few states other types of non-dental providers are not allowed to apply FV, even without seeking reimbursement.⁵⁴

Although one advantage of FV is that it can be applied easily and with minimal training,⁸ this review and the team’s subsequent search of the broader literature suggests FV delivery programs employing trained lay workers are rare in the US. One qualitative analysis found that policies allowing school sealant programs to substitute less costly labor (e.g., dental hygienists) for more costly labor (e.g., dentists) contributed to successful implementation and expansion of these programs.⁵³ This suggests that removing barriers for less costly, trained lay workers to deliver FV could contribute to SFVDP sustainability. One entity that does use trained lay workers to provide FV is the Indian Health Services (IHS).⁵⁵ Very young children served by IHS have one of the highest rates of early childhood caries in the world.⁵⁶ Lay providers that have been used in IHS models include trained lay health workers²² and Head Start staff including directors, health coordinators, and teachers.⁵⁶

When implementing SFVDPs, optimal effectiveness will likely be achieved by applying FV at least twice annually and by introducing FV as soon as the first tooth erupts²² —preschool (e.g., Early Head Start) for primary teeth beginning eruption at age 6 months and kindergarten for permanent teeth beginning eruption at age 6 years. In this review, all SFVDPs delivered FV at least twice annually and one study finding no evidence of effectiveness for SFVDPs serving children aged 3 to 5 years at extremely high caries risk noted that one possible explanation was implementing the program about 3 years after the first primary tooth erupts (around 6 months). Another study conducted in the same population but introducing FV sooner (at age 9 months) during physician visits found FV to be effective in preventing caries.⁵⁷

The review team identified some gaps in the evidence base. Priority questions for future research included:

How effective are SFVDPs in reducing disparities in the US for historically disadvantaged racial and ethnic groups and for rural areas?

This review found SFVDPs to be effective in preventing caries initiation and progression. SFVDP also increased the number of FV treatments received and reduced disparities in caries initiation by income and other social determinants of health. Findings further suggest that SFVDPs prevent caries among school children of all ages, can be implemented in either rural or urban areas and in communities with and without fluoridated tap water, and can be delivered by dental and non-dental providers.