As it turns out, fluoride helps prevents tooth cavities in at least three ways.
Science has known for a while that fluoride acts as a building block for teeth. Fluoride supplements, whether in drinking water or vitamins, help build stronger enamel in kids’ teeth before they even emerge from the gums.
After the teeth emerge, fluoride, regularly applied, settles into the nooks and crannies in the teeth that are formed when acid begins breaking down the surface of the enamel (the beginnings of a cavity).
The fluoride attracts calcium and other strengthening minerals to the weakened site. Repeated exposure to fluoride ends up forming a new layer of tooth that is harder and stronger than the original.
What’s interesting is a more recent discovery about another role of fluoride in fighting tooth decay. It appears that fluoride residue in your mouth neutralizes the bacteria in plaque and keeps it from forming acidic, tooth-rotting sugars.
Ironically, it goes to show that you should probably drink fluoridated tap water instead of that bottled stuff you thought was somehow healthier.
You should also use a fluoride toothpaste.
And no matter what your mom may have told you, you should avoid rinsing out your mouth after brushing your teeth so that the fluoride can stay around and kill all of those harmful bacteria.