Fluoride, a substance that's found naturally in water, plays an important role in healthy tooth development and cavity prevention.

Fluoride combats tooth decay in two ways:

1. It strengthens tooth enamel, a hard and shiny substance that protects the teeth, so that it can better resist the acid formed by plaque.
2. Fluoride allows teeth damaged by acid to repair, or re-mineralize, themselves.

Fluoride cannot repair cavities, but it can reverse low levels of tooth decay and thus prevent new cavities from forming.

Most children get the right amount of fluoride through a combination of fluoridated toothpaste and fluoridated water or supplements. Too much fluoride before 8 years of age can cause enamel fluorosis, a discoloration or mottling of the permanent teeth. This condition is unsightly but harmless and often can be treated with cosmetic procedures.