The treatment, called silver diamine fluoride, has been used for decades outside of the United States to combat cavities without the need for fillings. The FDA has been unable to approve silver diamine fluoride for cavities because it has lacked data from large clinical trials showing its effectiveness and safety among the U.S. population. But a new clinical trial conducted in the United States bolsters the argument for the FDA to approve silver diamine fluoride for tooth decay, the researchers say. The study found silver diamine fluoride effectively stopped tooth decay in more than half of children's baby teeth treated every six months with the liquid. The main downside of using silver diamine fluoride is that is permanently stains the site of decay on teeth.