Fluoride exists naturally in water sources and is derived from fluorine, the thirteenth most common element in the Earth's crust. It is well known that fluoride helps prevent and even reverse the early stages of tooth decay.

Tooth decay occurs when plaque — that sticky film of bacteria that accumulates on your teeth — breaks down sugars in food. The bacteria produce damaging acids that dissolve the hard enamel surfaces of teeth. If the damage is not stopped or treated, the bacteria can penetrate through the enamel causing tooth decay (also called cavities or caries). Cavities weaken teeth and can lead to pain, tooth loss, or even widespread infection in the most severe cases.

Fluoride combats tooth decay in two ways. It is incorporated into the structure of developing teeth when it is ingested and also works when it comes in contact with the surface of the teeth. Fluoride prevents the acid produced by the bacteria in plaque from dissolving, or demineralizing, tooth enamel, the hard and shiny substance that protects the teeth. Fluoride also allows teeth damaged by acid to repair, or remineralize, themselves. Fluoride cannot repair cavities, but it can reverse low levels of tooth decay and thus prevent new cavities from forming.

Despite the good news about dental health, tooth decay remains one of the most common diseases of childhood. According to the Centers for Disease Control and Prevention (CDC), more than one quarter of 2- to 5-year-olds and half of kids 12 to 15 years old have one or more cavities, and tooth decay has affected two thirds of 16- to 19-year-olds.