How does fluoride prevent tooth decay?

A fluoride applied to the outer layer of the tooth (topical fluoride) helps prevent tooth decay in adults and children by bonding with the outer layer of the enamel. This makes the outer layer of the enamel harder and more resistant to decay. In children systemic fluorides (fluoride pills that are chewed and swallowed) bind to the enamel that is forming in the permanent teeth also making it harder and more resistant to decay. Your dentist can apply a topical fluoride to your teeth or prescribe fluoride pills for you or your children. Many community water supplies have added fluoride to the water supply to help cut down on cavities.

The outer layer of your tooth consists of enamel. Enamel is composed primarily of calcium hydroxyapatite. When your teeth are exposed to fluoride at high enough concentrations, fluoride ions can displace a small number of calcium ions. Your enamel will now have fluoride hydroxyapatite, as well as the naturally occurring calcium hydroxyapatite. This makes your enamel much more resistant to acid erosion or demineralization.

Daily application of fluoride is easily accomplished by using a fluoride containing toothpaste. Most toothpastes contain fluoride, but you can confirm this by checking that sodium fluoride is listed among the active ingredients at a concentration of around .15%.

When the tooth is forming, fluoride is taken up by the tooth and alters the structure, making it more resistant to the acids produced by bacteria which causes decay. Once the tooth has erupted into the mouth, the fluoride helps to reduce the effect of the acids on the outer surface of the tooth.

Saliva is the mouth's primary defense against tooth decay. Research has proven that fluoride works to prevent tooth decay by boosting the ability of saliva to return lost minerals to tooth enamel before cavities can develop. Saliva enhances protection of enamel by providing high levels of calcium and phosphate ions at the tooth surface. The presence of those ions slows demineralization and encourages an ongoing remineralization of tooth enamel. The best explanation of how fluoride works is that it enhances the natural remineralizing properties of saliva.
Fluoride treatments help strengthen teeth and also are a barrier against further decay.  When a young child drinks water with fluoride in small amounts, the fluoride gets into the child's body through the bloodstream. Fluoride then becomes an actual part of a child's permanent teeth as they are forming. Ingesting fluoride in water combines with saliva in the mouth. The fluoride helps to strengthen the surfaces of the  teeth  and keeps acids from eating away at the hard tooth enamel.  

You actually paint fluoride on your teeth when you brush with a toothpaste that contains fluoride.  Applying fluoride to the hard shell of the teeth speeds up remineralization. Remineralization means that specific minerals in the saliva such as fluoride and calcium are actually put back into the tooth's enamel.  Your dentist has fluoride treatments that are very strong and can block tooth decay and acids. Ask about these treatments at your next visit.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.