Is fluoride harmful? Fluoride toothpaste, fluorosis, fluoride and IQ, and what the research really says

How does fluoride protect teeth from decay?

Fluoride protects teeth because it supports remineralisation, the rebuilding of minerals in the enamel after attacks by acids produced by plaque bacteria. The UK prevention toolkit Delivering better oral health (DBOH) explains that regular contact with fluoride maintains a level in plaque that favours remineralisation of the tooth surface.

That is why regularity matters, not a single large dose. According to DBOH, brushing with fluoride toothpaste twice a day instead of once lowers the risk of tooth decay by 14%.

Fluoride reaches the teeth mainly from toothpaste, and additionally from varnish applied at the surgery and from mouthwashes. Fluoride is also a natural component of water and some drinks, such as black tea, but the amount in them varies.

Does fluoride toothpaste work? What the research says

Fluoride toothpaste works: a 2003 Cochrane review covering 70 studies and more than 42,000 children found that, compared with fluoride-free toothpaste, it reduces the increase in tooth decay by an average of 24%. The authors considered the benefits firmly established by more than half a century of research.

The effect grows with concentration. A 2010 Cochrane review reports a 23% reduction in tooth decay for toothpastes of 1000 to 1250 ppm and 36% for toothpastes of 2400 to 2800 ppm, while toothpastes of 440 to 550 ppm and lower had no significant effect. The 2019 update (96 studies) confirmed the benefit in adults as well, and side effects, where they were studied, were minimal.

According to a 2013 Cochrane review, fluoride varnish applied at the surgery reduced the increase in tooth decay by about 43% in permanent teeth and by 37% in milk teeth.

When is fluoride harmful? The dose matters

Fluoride does harm when the dose is too high, and in practice this happens in two situations: when a young child swallows too much fluoride while the teeth are developing, and when a large amount of toothpaste is eaten in one go. The first leads to fluorosis, the second to acute poisoning.

Fluorosis is a change in the appearance of the enamel, from fine white lines to patches and pitting, described in more detail in the article on white spots on teeth. DBOH notes that the crowns of the permanent incisors complete mineralisation by about 30 months of age, and that the risk of visible fluorosis of the premolars concerns children under 6. The 2010 Cochrane review points out that most of the data concern mild fluorosis.

Acute poisoning requires doses many times greater than those from brushing. According to Whitford’s review (2011), the probably toxic dose is 5 mg of fluoride per kilogram of body weight, which a child weighing 10 kg would reach by eating about 50 g of ordinary toothpaste. That is roughly 200 times more fluoride than in a pea-sized amount of toothpaste, which is why toothpaste is kept out of children’s reach.

Sources of fluoride: how much they contain and what the research says

Sources of fluoride differ in concentration and purpose, so their safety and effectiveness are assessed separately. The table lists the ones patients come across most often, together with the conclusions of reviews and guidelines.

Fluoride and IQ: what did the NTP report actually find?

The August 2024 report of the US National Toxicology Program (NTP) concludes, with moderate confidence, that higher fluoride exposure, such as drinking water containing more than 1.5 mg of fluoride per litre, is associated with lower IQ in children. This is the value in the WHO drinking water guidelines and also the limit in force in the European Union, including Poland.

The NTP stresses that this is an association, not proof of causation, and that there are not enough data to assess the effect of the lower concentration of 0.7 mg/l recommended for community water supplies in the US. The report concerned total exposure from all sources, the IQ studies were conducted in 10 countries, none of them the United States, and by design it did not assess the benefits of fluoride.

A meta-analysis by the NTP team (74 studies) was published in JAMA Pediatrics in January 2025. The report did not assess toothpaste separately, and its threshold describes the combined exposure of the whole body from all sources.

Can fluoride from toothpaste lower IQ?

Fluoride from toothpaste used as recommended comes in small, measured amounts, while the threshold in the NTP report concerns something else: the body’s combined exposure. The NTP used the value of 1.5 mg/l in water as an approximate measure of total exposure, and a pea-sized amount of 1000 ppm toothpaste contains 0.25 mg of fluoride.

DBOH calculates that even if a child weighing 15 kg swallowed a whole pea-sized amount of 1000 to 1500 ppm toothpaste, the absorbed dose would be about 0.02 to 0.025 mg per kilogram of body weight, and with a smear of toothpaste, recommended for the youngest children, about 0.007 to 0.01 mg. That is why advice for young children relies on small amounts of toothpaste, not on giving up fluoride.

Toothpaste use was taken into account in the Dunedin cohort in New Zealand (Broadbent et al., 2015): using fluoride toothpaste, taking fluoride tablets and living in an area with fluoridated water before the age of 5 were not associated with clear differences in IQ at ages 7 to 13 or at age 38.

Fluoride-free toothpaste: is it a good alternative?

Fluoride-free toothpaste does not give the protection against decay that fluoride toothpaste provides, and the Cochrane reviews compared exactly these two options. DBOH recommends that people who choose fluoride-free toothpaste be told about the loss of the anti-caries effect and the greater need to limit sugar.

According to DBOH, new products, such as toothpaste tablets, have limited or no evidence of effectiveness, and some of them contain no fluoride. For products with nano-hydroxyapatite, the review by Wierichs et al. (2022) found that the small number of studies, short follow-up and high risk of bias do not allow firm conclusions, and some of the studies were funded by manufacturers.

The same problem applies to children’s toothpastes with a very low fluoride content: in the 2010 Cochrane review, toothpastes of 550 ppm and weaker did not differ significantly from placebo. The fluoride concentration in ppm is stated on the packaging.

How much fluoride for children, and what is professional fluoride treatment?

Polish experts recommend for children a 1000 ppm toothpaste in a rice-grain amount up to the age of 3, a pea-sized amount from 3 to 6 (1450 ppm where the risk of decay is high), and 1450 ppm from the age of 6. The European recommendations of the EAPD move the boundary between a rice-grain and a pea-sized amount to the age of 2; both versions and the rules for brushing are in the article on how to brush your teeth properly. An adult supervises brushing, and the child spits out the foam.

Professional fluoride treatment (fluoryzacja) means applying fluoride varnish at the surgery. Children and young people under 18 are entitled to it on the NFZ (Poland’s National Health Fund) no more often than once a quarter, and DBOH recommends varnish twice a year for adults at increased risk of decay too. Legal position as of 18 October 2026.

According to DBOH, the varnish is well tolerated and safe for most patients. It is contraindicated in ulcerative gingivitis and stomatitis, and for varnishes containing colophony also in people with an allergy to sticking plaster or a severe allergy or asthma that has required hospital treatment.

How it works at DentalBlue

At DentalBlue in Białystok, prevention includes professional cleaning, fissure sealing and fluoride treatment, and paediatric dentistry has its own section in the price list. The clinic’s clinical team includes dentists, dental assistants and hygienists.

In the clinic’s price list, the item “Fluoryzacja” (fluoride treatment) costs 100 zł, and “Czyszczenie zębów z fluoryzacją” (teeth cleaning with fluoride treatment) in paediatric dentistry costs 250 zł. The final scope and cost are set at the visit, and prices may change.