Fluoride works before, during and after it hits your teeth, and it has different roles depending on your age. Used before eating and drinking, it actually inhibits some acid from attacking tooth enamel. It has an effect on the bacteria as it forms to become corrosive to teeth. When fluoride from toothpaste or dental rinses is distributed around the teeth, it sets in and can help with the mouth's ongoing remineralization, as well. And long after fluoridated, or fluoride-containing drinking water goes through the mouth and down the hatch, it works in a systemic way to provide fluoride stores from the inside out [source: AAPD].
Most regions in the United States add fluoride to drinking water sources, and this has been standard practice since about 1945. Studies have shown that fluoridated water has lowered rates of tooth decay by 20 to 50 percent, allowing some children to grow up without getting cavities or with fewer of them [sources: ADA; AAPD]. As permanent teeth are growing, it's considered especially beneficial to use fluoride. Tooth enamel forms tighter bonds as teeth mature and fluoride can actually combine with enamel as this bonding is taking place, adding extra protection from decay [source: Dowshen]. After enamel has finished growing, fluoride stops penetrating at the deeper level of the mineral bonds but it still works well at protecting tooth surfaces from plaque and cavities.
Although fluoridated water at its most effective levels is available through about 72.4 percent of the drinking water sources in the U.S. and fluoride dental products are even more readily available, not everyone chooses to ingest or treat teeth with fluoride [source: ADA]. Some debate both the safety and effectiveness of fluoride, whether it's applied to teeth or taken into the body, and we'll look at some of the controversies later. Others, however, are more aggressive in their use of fluoride because it can be a very effective tool in fighting tooth decay in those who are at high risk for it.
We'll look at who should be getting fluoride treatments and how they're administered, next.