We all want healthier teeth, but what does the science say about fluoride, an additive that’s used in the U.S. and around the world to help support strong, healthy teeth?

According to the Centers for Disease Control and Prevention (CDC), fluoride is a safe and healthy solution. In small amounts, it helps to strengthen the teeth and to hinder the acids that harm them. Here’s how fluoride works, and why it’s important.

Fluoridated Water Access

Fluoride is a mineral that’s naturally found in our food and water. But because it fights tooth decay, additional fluoride is also added to drinking water in communities throughout the U.S., and to dental products, to reduce the risk of cavities.

In the U.S., the average person consumes an adequate amount of fluoride through their food and water, though the bulk of the mineral that people in the U.S. consume — around 60 percent — comes from fluoridated water, or water with additional fluoride added. In 2020, almost 63 percent of people in the U.S. could access fluoridated water in their communities.

The most common fluoride additive that’s incorporated into water is fluorosilicic acid, though sodium fluorosilicate and sodium fluoride are also used. For communities that add fluoride to their water, the recommended concentration is around 0.7 milligrams of fluoride per liter — a concentration that maintains the mineral’s ability to combat tooth decay, while also minimizing associated risks.

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Fluoride Fights Tooth Decay

Fluoride reduces the risk of tooth decay, which occurs when bacteria in the mouth make acids that attack the teeth, demineralizing them over time. This can cause cavities and lead to infection and tooth loss in the long term, affecting quality of life for children and adults alike. In children, these issues can also impact school attendance and performance, as studies show that students with poor tooth health miss more school than their peers.

Fluoride intake at the recommended levels staves off tooth decay by slowing the activity of bacteria in the mouth, preventing the production of tooth-attacking acids. It also impedes and reverses tooth damage, stopping demineralization and supporting remineralization instead.

In 2018, a study of around 7,000 children and 12,000 children and adolescents found that communities with fluoridated water saw fewer cases of tooth decay. In fact, when 75 percent of their water contained at least 0.7 milligrams of fluoride per liter, there was a 30 percent reduction in the rate of decay in primary teeth and a 12 percent reduction in the rate of decay in their permanent teeth.

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How Does Fluoride Do It?

Filling in for minerals that are already missing from the tooth surface, fluoride patches up past decay. Sometimes, fluoride also switches the substances in the tooth surface, swapping minerals with more resilient replacements, making teeth more resistant to demineralization. Some studies also suggest that fluoride minimizes the amount of acid that bacteria make.

Studies show that too much fluoride can cause dental fluorosis, a condition commonly associated with tooth staining and sometimes associated, in severe cases, with tooth damage. Chronic over-consumption of fluoride is also associated with skeletal fluorosis, in which fluoride accumulation weakens the bones.

According to the National Institutes of Health in June, the risk of these conditions rises as fluoride intake increases above the amounts that are recommended, though “there is no indication” that the two conditions are “caused by the recommended level of fluoride in water.”

Another common concern is fluoride’s impact on children’s cognition. Some studies suggest that the consumption of water with an increased concentration of fluoride — in one report, 1.5 milligrams per liter — is associated with reduced IQ in children. That report, which was released by the National Toxicology Program in August 2024, did not consider currently recommended concentrations, while other studies show no such associations up to concentrations of 1.5 milligrams per liter.

“Fluoride in drinking water has a beneficial effect at lower concentrations in the prevention of tooth decay and detrimental effects on human health at higher concentrations,” reports a review of fluoride research from 2023. “These meta-analyses show that fluoride exposure relevant to community water fluoridation is not associated with lower IQ scores in children.”

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Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.