Nobody looks forward to having a cavity drilled and filled by a dentist. Now there’s an alternative: an antimicrobial liquid that can be brushed on cavities to stop tooth decay — painlessly.

The liquid is called silver diamine fluoride, or S.D.F. It’s been used for decades in Japan, but it’s been available in the United States, under the brand name Advantage Arrest, for just about a year.

The Food and Drug Administration cleared silver diamine fluoride for use as a tooth desensitizer for adults 21 and older. But studies show it can halt the progression of cavities and prevent them, and dentists are increasingly using it off-label for those purposes.