If you thought fluoride was a synthetic chemical additive to many oral care products, you are not alone. Actually, fluoride is a naturally occurring mineral that is found throughout the Earth’s crust and widely distributed in nature. Some foods and water supplies contain fluoride as well. Fluoride is often added to community drinking water supplies that do not already have it at sufficient levels to help strengthen teeth and reduce tooth decay.

The effectiveness of fluoride in fighting cavities was discovered, in the 1930s, when researchers found that children who grew up drinking naturally fluoridated water had less tooth decay than people living in areas without fluoridated water. Studies since then have repeatedly shown that when fluoride is added to a community’s water supply, tooth decay decreases.

The American Dental Association, the World Health Organization and the American Medical Association, among many other organizations, have endorsed the use of fluoride in water supplies because of its effect on tooth decay. It’s even been referred to as “nature’s cavity fighter,” according to the American Dental Association (ADA).

The “how” behind the fluoride gets a little more technical – let’s dive in. Fluoride works during the demineralization and remineralization processes that naturally occur in your mouth. The demineralization process is started by the bacteria in the plaque on your teeth. The bacteria feeds on sugar and other carbohydrates in your mouth and produces acidic saliva that weakens tooth enamel. Fluoride helps control and protect against the damage caused by the demineralization process, keeping teeth resilient to its negative effects.

Other times, when your saliva is less acidic, fluoride helps by replenishing the calcium and phosphate ions that make your teeth harder and more protected. This process is called remineralization. Too much loss of minerals without enough replacement leads to tooth decay.

Fluoride helps teeth in two ways. When children eat or drink fluoride in small doses, it enters the bloodstream and becomes part of their developing permanent teeth. Additionally, fluoride becomes part of the saliva and helps strengthen teeth from the outside, so acids are less able to damage tooth enamel. This process keeps your teeth strong while also helping to prevent cavities and tooth sensitivity.

Now it’s time to get mineral. Fluorine is an element and, as the Royal Society of Chemistry (RSC) points out, it is highly reactive. Because it’s so reactive in its elemental form, fluorine easily forms compounds. One of fluorine’s most well-known compounds is fluoride. This means that fluoride is a natural ingredient when used in fluoride toothpaste.

Some examples of fluoride compounds include calcium fluoride, sodium fluoride, sodium monofluorophosphate, and stannous fluoride (sometimes called tin fluoride). Sodium fluoride and stannous fluoride are two types that are often used in toothpaste.

When you use a product containing fluoride, like toothpaste, the fluoride ends up in your saliva. When your teeth are coated in that saliva, the enamel (the outermost layer of the teeth) ends up absorbing the fluoride. Once there, the fluoride bonds with the calcium and phosphate that naturally exist in your enamel to create fluorapatite, which is a strong material that can resist decay and help prevent cavities.

Fluoride is safe and effective when used properly and in appropriate doses, but like anything else, it is possible to get too much of a good thing. After decades of research, the main risk linked to fluoride overuse is dental fluorosis, a condition that kids can develop if they’re exposed to excessive fluoride for an extended period of time when they’re too young.

The Centers for Disease Control and Prevention (CDC) confirms that both the safety and benefits of fluoride are well documented. There has never been any scientific evidence linking fluoride to adverse health effects when consumed in the correct amounts. In fact, the evidence consistently shows that fluoride is safe and effective in the amounts your toothpaste and household tap provides.

It’s not just the CDC that upholds the merits of fluoride, though; according to the American Dental Association (ADA), more than 125 organizations around the world also recognize its safety and value. These organizations include the ADA, the American Medical Association and the World Health Organization.