What does the research show about fluoride?

Fluoride

Cochrane reviews found fluoride toothpaste cut new cavities in children by about a quarter, varnish by 43% and supervised rinses by 27% in permanent teeth. Supplements lowered cavities in permanent teeth, with an unclear effect on baby teeth. Supplements and stronger toothpaste in young children raised mild dental fluorosis. Water fluoride above 1.5 mg/L was linked to lower child IQ.

Add to Bio HackChecked 2026-11-12

Status: In the US, fluoride toothpaste and fluoride mouthrinse are sold over the counter. Fluoride varnish is applied by dental professionals. Fluoride tablets, drops and lozenges are prescription drugs that FDA has not reviewed or approved, and in 2025 FDA moved to restrict those labeled for children under 3 or for older children not at high risk of tooth decay.
Also called: sodium fluoride, stannous fluoride, SnF2, sodium monofluorophosphate, MFP, amine fluoride, fluoride toothpaste, fluoride varnish, fluoride mouthrinse, fluoride mouthwash, fluoride rinse, fluoride tablets, fluoride drops, fluoride lozenges, fluoride supplements, high-fluoride toothpaste, Duraphat, PreviDent
Taken for: cavities, tooth decay, preventing cavities, teeth, stronger enamel, white spots, white spots from braces, tooth erosion, enamel erosion

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help4

StrongShown to prevent about 24% of new cavities in children against non-fluoride toothpaste, more with higher fluoride concentration and supervised brushing.
ModerateShown to prevent about 43% of new cavities in permanent teeth. A preschool review found 12% fewer, with estimates not significant once prediction intervals were considered.
ModerateShown to prevent about 27% of new cavities in permanent teeth with supervised school rinsing in children and adolescents.
LimitedLimited evidence: supplements lowered cavities in permanent teeth about 24% against none, with unclear results in baby teeth and no gain over topical fluoride.

Reported risks5

ModerateLinked to 2.4 to 2.6 times higher odds of dental fluorosis in children who used fluoride supplements in their first 6 years, in non-fluoridated communities.How often is not known
ModerateLower-fluoride toothpaste before age 6 was shown to lower fluorosis in permanent teeth by about 25%. Most fluorosis found was mild.How often is not known
ModerateLinked to lower IQ in children at higher exposures, such as water above 1.5 mg/L. Reviews disagree on any link below that level.How often is not known
ModerateFDA states its evaluation supports limiting ingestible fluoride for children to those 3 and older at high risk of tooth decay. It began removal action in 2025.How often is not known
LimitedLimited evidence: high fluoride exposure was linked to about twice the skeletal fluorosis, with risk rising almost linearly up to 5 mg/L in water.How often is not known

What people take it for, and what was found

Shown to help4

Strong

Cavities: fluoride toothpaste

Shown to prevent about 24% of new cavities in children against non-fluoride toothpaste, more with higher fluoride concentration and supervised brushing.

The numbers and sources

Effect: Across 70 trials (42,300 children), fluoride toothpaste prevented 24% of new decayed, missing and filled surfaces against non-fluoride toothpaste (prevented fraction 24%, 95% CI 21 to 28%). The effect was larger with higher baseline decay, higher fluoride concentration, more frequent use and supervised brushing, and did not change with water fluoridation [1]. A 2019 update of 96 studies found 1,000 to 1,250 ppm toothpaste lowered caries increments in children and adolescents (SMD -0.28, 95% CI -0.32 to -0.25, 55 studies) and 1,450 to 1,500 ppm lowered them more (SMD -0.36, 95% CI -0.43 to -0.29). In young children's baby teeth, 1,500 ppm toothpaste lowered decayed and filled surfaces by 1.86 (95% CI -2.51 to -1.21, 1 study, 998 children). In adults, 1,000 or 1,100 ppm toothpaste lowered decayed, missing and filled surfaces by 0.53 (95% CI -1.02 to -0.04, 3 studies, 2,162 adults) [2].
Population: Children up to 16 in 74 trials [1]. Children, adolescents and adults in 96 trials published 1955 to 2014, most followed for 36 months [2].
Sources: [1], [2]
Caveats: Heterogeneity was clear in the 2003 review [1]. Most comparisons between concentrations were low certainty, and evidence in adults came from 3 studies [2]. Soft tissue damage and tooth staining were minimal where reported, and only a minority of studies assessed adverse effects [2].

ModerateStudied in children

Cavities: fluoride varnish

Shown to prevent about 43% of new cavities in permanent teeth. A preschool review found 12% fewer, with estimates not significant once prediction intervals were considered.

The numbers and sources

Effect: Across 13 trials in permanent teeth, fluoride varnish prevented 43% of new decayed, missing and filled surfaces against placebo or no treatment (95% CI 30% to 57%). Across 10 trials in baby teeth, it prevented 37% (95% CI 24% to 51%) [3]. A review of 20 trials in preschool children found a smaller effect: the risk of new cavities was 12% lower (RR 0.88, 95% CI 0.81 to 0.95), so about 17 children would need varnish for one to avoid new cavities where half develop them. Once prediction intervals were considered, none of the pooled estimates was significant [4].
Population: 22 trials with 12,455 children and adolescents [3]. Preschool children in 20 trials, 17 pooled [4].
Sources: [3], [4]
Caveats: The Cochrane review included mainly high risk of bias trials, with I² of 75% in permanent teeth [3]. Only one preschool trial had low risk of bias in all domains [4]. The two reviews differ in the size of the effect in young children.

ModerateStudied in children

Cavities: fluoride mouthrinse

Shown to prevent about 27% of new cavities in permanent teeth with supervised school rinsing in children and adolescents.

The numbers and sources

Effect: Across 35 trials (15,305 children and adolescents), supervised fluoride mouthrinse prevented 27% of new decayed, missing and filled permanent tooth surfaces (95% CI 23% to 30%, I² 42%, moderate quality). The figure for whole teeth was 23% (95% CI 18% to 29%, 13 trials). Baseline decay, background fluoride, rinsing frequency and concentration did not change the effect [5].
Population: 37 trials with 15,813 children and adolescents, almost all rinsing with sodium fluoride under supervision in schools [5].
Sources: [5]
Caveats: 28 of 37 trials were at high risk of bias. Adverse effects were rarely reported. Most evidence comes from supervised school programs, and the effect of home use is less clear [5].

LimitedStudied in children

Cavities: fluoride supplements (tablets, drops, lozenges)

Limited evidence: supplements lowered cavities in permanent teeth about 24% against none, with unclear results in baby teeth and no gain over topical fluoride.

The numbers and sources

Effect: In 3 studies comparing supplements with no supplement, permanent teeth had 24% fewer decayed, missing and filled surfaces (95% CI 16 to 33%). The effect on baby teeth was unclear: one study found no effect and another found a large reduction. Against topical fluorides or other prevention, supplements showed no difference in either set of teeth [6]. A second review found weak and inconsistent evidence for baby teeth, and found reductions in permanent teeth of older children. One trial of 3 to 6 year olds found a 43.0% difference and another found no significant benefit [7].
Population: 11 studies with 7,196 children [6]. 12 trials reported in 20 papers [7].
Sources: [6], [7]
Caveats: 10 of 11 trials were at unclear risk of bias and 1 at high risk, and the Cochrane authors call the evidence weak [6]. Fifteen reports had withdrawal rates of 30% or more [7].

Mixed results1

Limited

Enamel erosion: stannous fluoride toothpaste

Limited evidence: stannous fluoride toothpaste reduced erosive wear more than sodium fluoride in lab tests, but not in enamel samples worn in the mouth.

The numbers and sources

Effect: Across 8 laboratory and in situ studies, stannous fluoride toothpaste reduced erosive tooth wear more than sodium fluoride toothpaste in vitro (effect size -6.80, 95% CI -13.42 to -0.19). In situ studies, in which volunteers wear enamel samples in the mouth, did not show a significant difference [10].
Population: In vitro and in situ enamel samples [10].
Sources: [10]
Caveats: No clinical trials were included. The authors call the evidence insufficient for firm conclusions [10].

Not shown to help2

Limited

Fluoride tablets in pregnancy and children's cavities

One trial found fluoride tablets late in pregnancy did not change the share of children with cavities at ages 3 or 5.

The numbers and sources

Effect: In one trial, fluoride tablets in the last 6 months of pregnancy did not change the share of children with cavities at age 3 (RR 1.46, 95% CI 0.75 to 2.85, 938 children) or age 5 (RR 0.84, 95% CI 0.53 to 1.33, 798 children). Fluorosis at age 5 was similar in both groups [8].
Population: One randomized trial of pregnant women and their children [8].
Sources: [8]
Caveats: Very low quality evidence from a single trial [8].

Moderate

White spots during braces

Not shown to lower white spots with fluoride varnish during braces. Single studies found fewer with fluoride foam or 5,000 ppm toothpaste.

The numbers and sources

Effect: Professionally applied varnish of 7,700 or 10,000 ppm every 6 weeks did not clearly lower new white spot lesions against non-fluoride placebo (RR 0.52, 95% CI 0.14 to 1.93, 2 studies, 405 participants, low certainty). In single studies, fluoride foam of 12,300 ppm every 2 months cut new lesions from 49% to 12% (RR 0.26, 95% CI 0.11 to 0.57, 95 participants), and 5,000 ppm toothpaste lowered them from 27% to 18% against 1,450 ppm toothpaste (RR 0.68, 95% CI 0.46 to 1.00, 380 participants). A 250 ppm rinse did not differ from placebo [9].
Population: Patients with fixed braces in 10 studies, 1,798 randomized [9].
Sources: [9]
Caveats: Each positive comparison rests on one study at unclear risk of bias, and none has been repeated [9].

Doses studied

Toothpaste trials compared 440 to 2,800 ppm fluoride, and the adult trials used 1,000 or 1,100 ppm [2]. Mouthrinse trials mostly used 230 ppm daily or 900 ppm weekly or every two weeks [5]. In braces patients, trials used varnish at 7,700 or 10,000 ppm every 6 weeks, foam at 12,300 ppm every 2 months and toothpaste at 5,000 ppm [9]. Most supplement reports used dosage schedules similar to the American Dental Association's [7].

Risks

Reported risks5

ModerateHow often is not known

Dental fluorosis from supplements

Linked to 2.4 to 2.6 times higher odds of dental fluorosis in children who used fluoride supplements in their first 6 years, in non-fluoridated communities.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In non-fluoridated communities, cross-sectional and case-control studies gave an odds ratio of 2.4 to 2.6 for dental fluorosis in children who used supplements in their first 6 years. In follow-up studies the relative risk in long-term users was 5.5 to 12.2 [11]. All 5 studies in a later review found supplements raised the risk of mild to moderate fluorosis [7]. Fluorosis at age 5 did not differ after tablets taken in pregnancy [8].
Population: Children in 14 observational studies [11] and 5 studies published after 1997 [7]. One pregnancy trial [8].
Sources: [11], [7], [8]
Caveats: Observational data. The two reviews share an author [7][11].

ModerateStudied in childrenHow often is not known

Dental fluorosis from toothpaste and varnish in young children

Lower-fluoride toothpaste before age 6 was shown to lower fluorosis in permanent teeth by about 25%. Most fluorosis found was mild.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: In 2 trials (1,968 children) of toothpaste used under age 6, lower fluoride concentrations lowered the risk of fluorosis in permanent teeth: 550 against 1,000 ppm (RR 0.75, 95% CI 0.57 to 0.99) and 440 against 1,450 ppm (RR 0.72, 95% CI 0.58 to 0.89), moderate certainty. Varnish before age 4 did not change fluorosis in one trial (RR 0.77, 95% CI 0.45 to 1.31, 123 children), while 2 cross-sectional surveys linked it with more fluorosis (OR 2.18, 95% CI 1.46 to 3.25). Evidence on the age brushing began, brushing frequency and amount of toothpaste was low or very low certainty [12].
Population: 43 studies, 3 of them RCTs, in children [12].
Sources: [12]
Caveats: Most fluorosis found was mild. Most observational studies were at high risk of bias [12].

ModerateStudied in childrenHow often is not known

Children's IQ and brain development

Linked to lower IQ in children at higher exposures, such as water above 1.5 mg/L. Reviews disagree on any link below that level.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: The US National Toxicology Program concluded, with moderate confidence, that higher estimated fluoride exposures, such as drinking water above the WHO guideline of 1.5 mg/L, are consistently associated with lower IQ in children. 18 of 19 high-quality studies found an inverse association. It found the evidence in adults gave low confidence, and stated that more studies are needed on lower exposures [13]. A 2025 meta-analysis of 74 studies found lower IQ with higher exposure (SMD -0.45, 95% CI -0.57 to -0.33, 59 studies, 20,932 children). For drinking water, the association was null below 1.5 mg/L across all studies and stayed inverse below 1.5 mg/L in low risk of bias studies. IQ fell 1.63 points per 1 mg/L of urinary fluoride (95% CI -2.33 to -0.93, 13 studies) [14]. A 2023 meta-analysis of 8 studies from areas without endemic fluorosis found no difference in IQ between water fluoride at levels used for community water fluoridation and lower levels (SMD 0.07, 95% CI -0.02 to 0.17) [15]. Another 2023 meta-analysis found IQ 4.68 points lower at the highest against lowest exposure, and 3.05 points lower per 1 mg/L of water fluoride above 1 mg/L, up to 2 mg/L. The association was strongest in high risk of bias studies, and the one low risk of bias study found no effect [16].
Population: Children in 72 IQ studies [13], 74 studies, 45 in China [14], 8 studies in areas without endemic fluorosis [15] and 33 studies [16]. All observational.
Sources: [13], [14], [15], [16]
Caveats: These are cross-sectional and cohort studies, not trials. The NTP monograph does not address oral health benefits [13]. 52 of the 74 studies in the 2025 analysis were at high risk of bias [14]. Residual confounding could not be ruled out [16]. The reviews disagree at exposures below 1.5 mg/L [14][15][16].

LimitedHow often is not known

Skeletal fluorosis

Limited evidence: high fluoride exposure was linked to about twice the skeletal fluorosis, with risk rising almost linearly up to 5 mg/L in water.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: Across 23 studies, skeletal fluorosis was twice as common at the highest against the lowest fluoride exposure (RR 2.05, 95% CI 1.60 to 2.64), and 2.73 times as common for drinking water (95% CI 1.92 to 3.90). Risk rose almost linearly up to 5 mg/L in water, and moderate to severe forms rose at 5.00 mg/L [17]. A 53-year-old woman with a metatarsal fracture had a spine bone density T-score of +11, with very high fluoride levels linked to excessive tea and toothpaste consumption [18].
Population: Observational studies, many in regions where fluorosis is endemic [17]. One case report [18].
Sources: [17], [18]
Caveats: Observational data at moderate or high risk of bias [17].

ModerateHow often is not known

FDA action on ingestible fluoride for children

FDA states its evaluation supports limiting ingestible fluoride for children to those 3 and older at high risk of tooth decay. It began removal action in 2025.

The numbers and sources

How common: How often is not known: the sources give no rate.
Effect: On May 13, 2025, FDA began action to remove concentrated ingestible fluoride prescription drugs for children from the market. It stated that ingested fluoride has been shown to alter the gut microbiome, and that other studies suggested an association with thyroid disorders, weight gain and possibly decreased IQ [19]. On October 31, 2025, FDA sent notices to four companies about enforcement against unapproved ingestible fluoride drugs labeled for children under 3 or for older children at low or moderate risk of tooth decay. FDA stated it has not reviewed or approved these products for safety, effectiveness or quality, and that its evaluation supports limiting them to children 3 and older at high risk of tooth decay. It cited a Cochrane finding of no reduction in baby tooth decay and a meta-analysis linking higher fluoride exposure with lower IQ [20].
Population: Prescription fluoride tablets, drops and lozenges for children in the US [19][20].
Sources: [19], [20]
Caveats: The action covers ingestible products, not toothpaste, rinses or varnish [20].

Claims tested and not found

That fluoride tablets in pregnancy prevent cavities in the child. The share of children with cavities did not differ at age 3 or 5 [8].
That fluoride supplements prevent cavities in baby teeth. The Cochrane review found the effect unclear [6], and a second review found weak and inconsistent evidence [7].
That fluoride varnish every 6 weeks prevents white spots during braces. Two placebo-controlled studies found insufficient evidence of a difference [9].

Sources

Marinho VC, Higgins JP, Sheiham A, Logan S. Fluoride toothpastes for preventing dental caries in children and adolescents. Cochrane Database of Systematic Reviews. 2003. https://doi.org/10.1002/14651858.CD002278
Walsh T, Worthington HV, Glenny AM, et al. Fluoride toothpastes of different concentrations for preventing dental caries. Cochrane Database of Systematic Reviews. 2019. https://doi.org/10.1002/14651858.CD007868.pub3
Marinho VC, Worthington HV, Walsh T, Clarkson JE. Fluoride varnishes for preventing dental caries in children and adolescents. Cochrane Database of Systematic Reviews. 2013. https://doi.org/10.1002/14651858.CD002279.pub2
de Sousa FSO, Dos Santos APP, Nadanovsky P, et al. Fluoride Varnish and Dental Caries in Preschoolers: A Systematic Review and Meta-Analysis. Caries Research. 2019. https://doi.org/10.1159/000499639
Marinho VC, Chong LY, Worthington HV, Walsh T. Fluoride mouthrinses for preventing dental caries in children and adolescents. Cochrane Database of Systematic Reviews. 2016. https://doi.org/10.1002/14651858.CD002284.pub2
Tubert-Jeannin S, Auclair C, Amsallem E, et al. Fluoride supplements (tablets, drops, lozenges or chewing gums) for preventing dental caries in children. Cochrane Database of Systematic Reviews. 2011. https://doi.org/10.1002/14651858.CD007592.pub2
Ismail AI, Hasson H. Fluoride supplements, dental caries and fluorosis: a systematic review. Journal of the American Dental Association. 2008. https://doi.org/10.14219/jada.archive.2008.0071
Takahashi R, Ota E, Hoshi K, et al. Fluoride supplementation (with tablets, drops, lozenges or chewing gum) in pregnant women for preventing dental caries in the primary teeth of their children. Cochrane Database of Systematic Reviews. 2017. https://doi.org/10.1002/14651858.CD011850.pub2
Benson PE, Parkin N, Dyer F, et al. Fluorides for preventing early tooth decay (demineralised lesions) during fixed brace treatment. Cochrane Database of Systematic Reviews. 2019. https://doi.org/10.1002/14651858.CD003809.pub4
Trentin GA, Mendes LT, Silva BSD, et al. Reduction in erosive tooth wear using stannous fluoride-containing dentifrices: a meta-analysis. Brazilian Oral Research. 2021. https://doi.org/10.1590/1807-3107bor-2021.vol35.0114
Ismail AI, Bandekar RR. Fluoride supplements and fluorosis: a meta-analysis. Community Dentistry and Oral Epidemiology. 1999. https://doi.org/10.1111/j.1600-0528.1999.tb01991.x
Wong MCM, Zhang R, Luo BW, et al. Topical fluoride as a cause of dental fluorosis in children. Cochrane Database of Systematic Reviews. 2024. https://doi.org/10.1002/14651858.CD007693.pub3
National Toxicology Program. NTP monograph on the state of the science concerning fluoride exposure and neurodevelopment and cognition: a systematic review. NTP Monograph. 2024. https://doi.org/10.22427/ntp-mgraph-8
Taylor KW, Eftim SE, Sibrizzi CA, et al. Fluoride Exposure and Children's IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatrics. 2025. https://doi.org/10.1001/jamapediatrics.2024.5542
Kumar JV, Moss ME, Liu H, Fisher-Owens S. Association between low fluoride exposure and children's intelligence: a meta-analysis relevant to community water fluoridation. Public Health. 2023. https://doi.org/10.1016/j.puhe.2023.03.011
Veneri F, Vinceti M, Generali L, et al. Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis. Environmental Research. 2023. https://doi.org/10.1016/j.envres.2023.115239
Veneri F, Iamandii I, Vinceti M, et al. Fluoride Exposure and Skeletal Fluorosis: a Systematic Review and Dose-response Meta-analysis. Current Environmental Health Reports. 2023. https://doi.org/10.1007/s40572-023-00412-9
Joshi S, Hlaing T, Whitford GM, Compston JE. Skeletal fluorosis due to excessive tea and toothpaste consumption. Osteoporosis International. 2011. https://doi.org/10.1007/s00198-010-1428-6
US Food and Drug Administration. FDA Begins Action To Remove Ingestible Fluoride Prescription Drug Products for Children from the Market. 2025. https://www.fda.gov/news-events/press-announcements/fda-begins-action-remove-ingestible-fluoride-prescription-drug-products-children-market
US Food and Drug Administration. FDA Acts to Protect Children from Unapproved Fluoride Drug Products. 2025. https://www.fda.gov/news-events/press-announcements/fda-acts-protect-children-unapproved-fluoride-drug-products

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