In a study of nearly 3,000 schoolchildren, silver diamine fluoride — a liquid that is brushed onto the surface of teeth to prevent cavities or keep them from worsening — was as effective against cavities as dental sealants, the standard of care. A single dose of either topical treatment given in elementary schools prevented roughly 80% of cavities and kept 50% of cavities from worsening when children were seen two years later.