Fluoride, usually you hear this word when talking about dental health, but that's not strictly what it means. Fluoride is technically an F- anion, but not everyone is referring to this particle. Fluorine is capable of bonding with almost every element, so it can make a wide variety of compounds, ranging in use from pesticides to cavity prevention, they can be toxic or medicinal, highly reactive or entirely neutral. Fluoride could easily reference any of these multitudes of compounds, but that's not what I'm here to talk about.
Fluoride is used to help protect teeth from erosion. It's fairly simple, when a fluoride compound is ingested by, or otherwise applied to, a person it dissociates (breaks apart) leaving the lone fluorine ions. These ions are then absorbed into the enamel (the tooth's protective outer coating), where it reinforces that tooth, protecting it from decay. In everyday life, a person's teeth will experience both demineralization and remineralization. This means just what the words suggest, minerals are constantly being leeched from the teeth and replenished. Acids from plaque bacteria and sugars will begin to destroy the enamel of a tooth, causing the tooth to decay if these minerals aren't properly replenished. That's why fluoride is so important, it helps to replenish the enamel and protect it against further destruction.
Structure of the tooth
Fluoride is heavily used by dentists and health care professionals as a preventative measure against cavities, especially for young children. Below the age of 6, ingested fluoride will go into the development of teeth, strengthening them for the remainder of the child's life. Professionally applied topical fluoride treatments usually consist of a mixture of sodium fluoride (NaF), acidulated phosphate fluoride (FH3NaO4P), and sodium fluoride varnish (NaFV).
Duraflor, a brand of fluoride varnish
Fluoride is so useful that it has been added to the U.S. water supply. Now most public water supplies contain between 1.2 and 0.7mg/L of fluoride. These fluoridated water supplies reach well over 70% of Americans. However, with this chemical being added to public water supplies, it hasn't always been greeted favorably. Many people feel that fluoride should not be added to public water. It infringes on a person's right to choice, and there are legitimate medical concerns.
Most tap water contains fluoride
Like everything, fluoride can kill you. A fatal dose can be as low as 3 to 5 mg/kg. Now, given the weight of the average adult, you aren't likely to be hurt by this chemical, however, young children could easily be at risk. Even if it doesn't kill you, fluoride can still cause a condition known as fluorosis. When a person gets too much fluoride, usually while their teeth are developing, their teeth will develop discolorations and pitting. This can range anywhere from white spots to ugly brown blotches. While it may not be fatal, it certainly isn't fun to have.
Bad case of fluorosis.
I am no medical professional, so I won't try to tell you if the fluoride in American water systems is a good or bad thing, but I can recommend that everyone be mindful of how much fluoride they are consuming. Perhaps a talk with your local healthcare professional wouldn't be a bad idea if you're curious, or you could always type "fluoride" into the Google search bar to find more information. There is a strong debate on the subject, a debate I'd like to stay out of.