Fluoride is a natural mineral that builds strong teeth and prevents cavities. It’s been an essential oral health treatment for decades. Fluoride supports healthy tooth enamel and fights the bacteria that harm teeth and gums. Tooth enamel is the outer protective layer of each tooth. Fluoride is especially helpful if you’re at high risk of developing dental caries, or cavities. Cavities occur when bacteria build up on teeth and gums and form a sticky layer of plaque.