Fluoride is a mainstay of dental care, whether it’s delivered in a treatment at your dentist’s office or in your toothpaste. But fluoride has become the focus of several conspiracy theories over the past few years, raising questions about its use. Some people allege that fluoride is harmful, while others say it’s a helpful tool in good dental health. Who is right? Here’s what you need to know about fluoride, as well as all the misinformation swirling around it.

What is fluoride?
Fluoride is an element that’s naturally found in rivers, lakes and oceans, as well as in some foods and drinks, according to the American Dental Association (ADA). “It is also added to public water supplies,” Dr. Michael Kosdon, a dentist at Smiles of NYC, tells Yahoo Life. Fluoride is known as “nature’s cavity fighter,” according to the ADA, and it’s often added to dental products, including toothpaste, to protect teeth from cavities.

What does fluoride do?
Fluoride helps to strengthen your teeth, Rebecca Henderson, associate professor in The Ohio State University College of Dentistry, tells Yahoo Life. “Teeth, like bones in our body, are composed of minerals —primarily calcium and phosphate.” When someone has cavities, bacteria feed on refined carbohydrates that you eat and produce an acid byproduct in your mouth, Henderson says.

“This acid removes minerals from our teeth, breaking down layers of tooth structure and eventually leading to a hole or a cavity in the tooth surface,” she explains. “Fluoride helps to strengthen the tooth surfaces by returning and preserving the lost minerals in our tooth, preventing a cavity from forming.”

Research has found that adding fluoride to water reduces the amount of tooth decay in young kids by 35%.