Ask the Expert: Why is fluoride good for dental health?

Read the Q&A with NIDCR Deputy Director Jennifer Webster-Cyriaque, D.D.S., Ph.D., who answers common questions about fluoride and how it works to prevent tooth decay.

What is fluoride?

Fluoride is a natural substance found in soil, water, and rocks. It is proven to prevent tooth decay (the development of dental cavities).

How does fluoride prevent tooth decay?

Tooth decay begins when bacteria in the mouth feed on sugar in foods and produce acids. These acids dissolve minerals, like calcium and phosphate, on the tooth’s hard outer layer, or enamel. Eventually, the acids create tiny holes that further weaken the enamel. As the holes get bigger, the enamel is permanently destroyed, creating a cavity. As the disease progresses, the decay makes its way to the center of the tooth that houses nerves and blood vessels, allowing spread and causing pain. Untreated cavities can lead to pain, missed days of school or work, and severe infection. An infection in a tooth may spread to other parts of the body and, in rare cases, have deadly results.

The good news is that early tooth decay can be stopped or reversed. Enamel can repair itself using minerals from saliva and – you guessed it – fluoride.

Fluoride prevents, stops, and reverses the early stages of tooth decay in people of all ages. It works by stopping the growth of bacteria that cause cavities and strengthening the hard outer layer of the tooth. Fluoride also reverses early tooth decay by replacing and preventing the loss of minerals in the teeth.

By preventing cavities, fluoride reduces the need for treatments such as fillings and tooth extractions and promotes good oral health. Good oral health is important for eating, speaking, and overall health. It’s also important for appearance, which can impact self-esteem; and performance at school and work. Good oral health is important for overall health.

Where do I get fluoride?

Some tap water contains fluoride from natural sources. Most people in the U.S. get fluoride from tap water that has fluoride added to it in areas where natural sources are low, fluoride toothpaste, and fluoridated mouth rinses. Such toothpastes and mouth rinses are widely available over the counter today. Using these products can significantly reduce tooth decay in children and adults.

Dentists or other health care providers can apply varnishes or gels that contain fluoride directly to teeth. They may also prescribe fluoride tablets or drops if your water doesn’t contain enough fluoride to prevent tooth decay.

How much fluoride is added to drinking water to prevent tooth decay?

Most water naturally contains some fluoride, but usually not enough to prevent cavities.

The U.S. Public Health Service recommends 0.7 mg/L (0.7 ppm) as the optimal concentration of fluoride in water to help prevent tooth decay. That’s less than one part per million or about the same as three drops of water in a 55-gallon barrel. If the local water contains less fluoride than this, the Public Health Service currently recommends adding enough fluoride to get to 0.7 mg/L. Fluoride at this low level is safe and effective at preventing tooth decay.

Although communities are not required to add fluoride to their water, many do. More than 70% of people living in the U.S. have access to fluoridated tap water. In communities with fluoridated water, all members of the community regardless of income have access to cavity prevention.

How do I know if my drinking water has fluoride?

Reach out to your local water utility to find out how much fluoride is in your drinking water. If you have well water or aren’t sure about your water source, ask your dentist to help you get your water tested for its fluoride level.

Additionally, some states voluntarily report to the Centers for Disease Control and Prevention whether their water systems have added fluoride. States are not required to report this information.

How do we know community water fluoridation helps prevent tooth decay?

In 1945, Grand Rapids, Michigan, became the first city to add fluoride to its public water supply. After just 10 years, the rate of cavities among children there fell more than 60%. When fluoride was added to the wider U.S. water supply, tooth decay dropped in both children and adults. Complete tooth loss in older adults also became much less common.

Dental health gets worse in communities where the water supply doesn’t have enough fluoride or where fluoride is removed. Recent research has shown that children who lived in areas without water fluoridation needed more dental treatments (such as fillings, root canals, and extractions) than those who had fluoridated water. Another study found that removing fluoride from drinking water worsened dental health inequities. In other words, the gap in dental health status between affluent and poor children grew even larger.

See our resource on community water fluoridation for more information.

Is there such a thing as too much fluoride?

Yes. The side effects depend on the total amount of fluoride the person takes in. Also, the effects are different depending on the person’s age and for how long they experience high levels of fluoride.

Children and infants who have too much fluoride during the tooth-forming years can develop a condition called dental fluorosis. Symptoms can be mild and show up as barely noticeable white spots on teeth. Severe symptoms may include pits and coloring of the teeth. Dental fluorosis is a concern until age 8. After age 8, the hard outer layer of permanent teeth, or enamel, is already fully formed and can no longer develop spots and pits from too much fluoride. Very high levels of fluoride –such as from accidentally ingesting fluoride products– can cause nausea and vomiting.

Long-term exposure to excessively high levels of fluoride can cause skeletal fluorosis, which causes pain and damage to bones and joints. Skeletal fluorosis is extremely rare in the U.S. and there is no evidence that it is caused by the recommended level of fluoride in public tap water.

Does fluoride increase the risk of health problems?

Studies have examined the effects of fluoride on the body and found no convincing scientific evidence linking it to an increased risk for any condition except fluorosis. Previous scientific studies have shown that fluoride does not increase the risk or severity of cancer, Down syndrome, heart disease, osteoporosis, immune disorders such as arthritis, kidney disorders, Alzheimer’s disease, or allergic reactions. Decades of studies in the U.S. prove that fluoride at the recommended level of 0.7 mg/L is safe and effective at preventing tooth decay.

I’ve heard that fluoride can negatively affect IQ in young children. Should my child avoid fluoridated water and toothpaste?

The National Toxicology Program (NTP) reviewed scientific studies in other countries and found a connection between high levels of fluoride and lower intelligence quotient (IQ) in children. The effect appeared when fluoride exposure was higher than 1.5 mg/L. This amount is more than twice the level that is recommended in U.S. drinking water.

Although the NTP review noted a connection between high fluoride and lower IQ, it did not conclude that high levels of fluoride cause lower IQ scores. We need more studies to better understand potential risks and benefits of higher levels of fluoride.

How can I make sure my children are getting the right amount of fluoride?

Caregivers of young children can do a few things to make sure children are getting the right amount of fluoride to prevent cavities. Caregivers can reach out to a health care professional and can also check that fluoride levels in their drinking water are at the recommended level: 0.7 mg/L. Levels higher than 1.5 mg/L that can increase the risk of dental fluorosis in children younger than 8.

If water fluoride levels are too high, consider using bottled water for drinking and cooking. You can also remove fluoride using a reverse osmosis filter system. Consult your child’s dentist or doctor regarding the appropriate use of fluoride toothpaste and other fluoride products. Supervise children’s tooth brushing until age 6.

If your water fluoride levels are low, talk to a dentist about using fluoride tablets or drops.

Learn about Fluoride and Dental Health