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Enamel, the outer layer of the crown of a tooth, is made of closely packed mineral crystals. Every day, minerals are lost and gained from inside the enamel crystals. Losing minerals is called demineralization. Gaining them back is called remineralization.

Demineralization begins with the bacteria in the plaque on your teeth. They primarily feed on sugar in your mouth. They can also feed on other carbohydrates, such as processed starches. As they feed, the bacteria produce acids that dissolve crystals in tooth enamel.

The loss of enamel is balanced by remineralization. In this process, minerals in the saliva, such as fluoride, calcium and phosphate, are deposited back into the enamel. Too much loss of minerals without enough replacement leads to tooth decay.

Fluoride helps teeth in two ways. Fluoride that is swallowed in water, other drinks and foods becomes part of the developing permanent teeth of children. Swallowed fluoride also is released by the saliva and can strengthen teeth from the outside. Acids are less able to damage tooth enamel strengthened by fluoride.

In addition, people apply fluoride directly to their teeth when they use a fluoride toothpaste or rinse at home. Both children and adults also can receive fluoride treatments in the dental office. Fluoride applied to the outside of the teeth helps to speed remineralization. Fluoride treatments, applied in the dental office, also are strong enough to disrupt the production of acids by bacteria.


About 75% of Americans served by public water supplies have adequate levels of fluoride in their home water supply. All community water systems with added fluoride in the United States have 0.7 parts per million (PPM) added to the water. Some types of bottled water also contain fluoride. If you drink public water, it's easy to find out whether your water contains fluoride, and how much. Just contact your town or city offices, or call the number on your water bill. In addition, the Centers for Disease Control (CDC) maintains a website where you can enter your water system and find out if the water you receive at home contains fluoride. The website address for The CDC’s “My Water’s Fluoride is:

If you drink well water, contact your state or county health department for a list of approved laboratories that will test a water sample. You may need to pay a fee.

Some types of home water filters can remove much of the fluoride from water. Check with the manufacturer or read the information that came with the filter.


Fluoride in foods, supplements and water enters the bloodstream through the stomach. From there, it is absorbed into the body. In children, the fluoride then becomes available to the teeth that are developing in the jaw. This process continues only until about age 16, when the crowns of all the permanent teeth are fully developed.

Topical fluoride can help to strengthen teeth at any age. These products are applied directly to the teeth. They include toothpaste, mouth rinses and professionally applied fluoride treatments. Topical fluoride treatments are in the mouth for only a short time. However, fluoride levels in the mouth remain higher for several hours afterward. Dentists can prescribe high-concentration fluoride gels, toothpastes and rinses. These can help people who are at high risk of developing cavities.

Professional fluoride treatments are given in a dental office. They are applied as a gel, foam or varnish. Another option is a medicine applied to the teeth that combines fluoride and silver (silver diamine fluoride). The fluoride used for these treatments has a higher strength than over-the-counter or prescription mouthwashes or toothpastes.

Fluoride supplements also are available by prescription for home use. They usually are reserved for children who live in areas where the water supply does not contain enough fluoride. Children who need supplements can receive them from ages 6 months to 16 years.


Children between 6 months and 16 years old should take fluoride supplements only if:

  • They do not drink water fluoridated to optimum levels
  • They also are at high risk of cavities (caries)
Fluoride supplements are available as liquids for younger children and tablets for older children. Either your pediatrician or your dentist can prescribe them. If your child has had cavities or is at high risk of tooth decay, he or she should use extra fluoride. This will promote remineralization. Fluoride mouth rinses are recommended for children over the age of 6. They are found in the mouthwash section of most stores and are available without a prescription. Your dentist can prescribe fluoride rinses and gels if your child needs a higher level of fluoride.


Water fluoridation is safe and effective. Carefully supervise your children when they use any fluoride supplement or other fluoride product. Be sure to store fluoride safely away from young children.

Fluoride supplements are taken each day in small amounts. The dose can range from 0.25 to 1 milligram per day. The dose is based on:

  • The child's risk of caries
  • The child's age
  • The amount of fluoride in the water
  • Keep fluoride tablets and all medicines out of reach of children. Toxic fluoride doses are based on weight. For example, the toxic dose of fluoride for a 2-year-old child weighing 22 pounds is 320 milligrams. For an 8-year-old child weighing 45 pounds, the toxic dose is 655 milligrams.

    Since these fluoride products are used in such small amounts, it is very difficult to receive toxic doses when using fluoride products at home. Dentists and physicians limit the amount of tablets they prescribe at one time to reduce the risk of overdose. To avoid any chance of overdose, do not stock up on fluoride tablets in your home. If you have any questions regarding fluoride risks, talk to your dentist or physician.

    All children should use fluoridated toothpaste. The CDC recommends If your children are younger than 6, be cautious about how they use it, and that caregivers and parents monitor the use of toothpaste. Young children are more likely to swallow toothpaste after brushing instead of spitting it out. Use only a pea-sized amount of toothpaste when they brush. Encourage them to spit out as much as possible. Avoid flavored toothpastes that might encourage swallowing. For children less than 3 years of age a thin “smear” the size of a rice grain should be placed on the toothbrush.

    Swallowing excess toothpaste while teeth are developing can cause a cosmetic defect known as fluorosis. Mild fluorosis appears as white specks on the tooth. For many people this is not noticeable. Swallowing larger amounts of fluoride can cause "mottled" brown enamel. This is unusual and occurs mainly in areas that have naturally high levels of fluoride in the water supply.


    Last updated May 7, 2021



    • (Accessed 05-07-21)
    • U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries. Public Health Rep. 2015 Jul-Aug;130(4):318-31. doi: 10.1177/003335491513000408. PMID: 26346489; PMCID: PMC4547570.
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    • Chen AY, Wright JT, Quiñonez RB, Phillips C. Appropriate Fluoride Toothpaste Application: Improving Caregiver Compliance. Pediatr Dent. 2018 Nov 15;40(7):412-418. PMID: 31840640.