A liquid painted on a tooth stops cavities. No drilling.

A liquid painted onto a tooth in seconds can stop a cavity from getting worse, according to a Phase III clinical trial published in JAMA Pediatrics. The treatment, silver diamine fluoride, arrested decay in more than half of affected baby teeth when applied every six months. Researchers led by the University of Michigan enrolled 830 children younger than 6, recruited through dental clinics and Head Start programs in Michigan, New York, and Iowa. A dentist uses a small sponge tipped applicator to paint the liquid directly onto the decay. No drilling. No injections. The silver fights bacteria while fluoride strengthens the tooth. There is one catch. The treated spot permanently turns dark, which is noticeable on front teeth and entirely cosmetic. Tooth decay affects more than 40% of American children, and untreated cavities send thousands to emergency rooms every year. "This is a very effective and safe treatment, even in children as young as 1," said lead investigator Margherita Fontana.