Once tooth decay has been confirmed, fluoride is no longer useful, because fluoride itself is a kind of protective agent and has no effect on treating tooth decay, just as the screen of cell phone itself has been broken, then the film will not make the broken screen of cell phone grow again. Once the cavity is found, the only and the best way to treat is to go to the professional stomatology department, after the stomatologist check, apply the dental high-speed turbo drill to remove the cavity, and then apply the dental special filling material to fill the cavity, and the fluorine coating is a way to prevent the cavity, it has no meaning to treat the cavity. At present, a lot of toothpaste contains fluorine, it plays a role of preventing caries, but not treating caries.