1. A cavity starts with a tiny hole
A dental cavity begins with a miniscule hole in the enamel of your tooth. The hole gets there when bacteria in your mouth eat away at the enamel. Thanks to that itty-bitty hole, bacteria can then get into the center of the tooth—which is made of a somewhat softer material called dentin—and strip it of calcium. Over time, that turns the dentin into a brown mush. “If you look on an X-ray, it looks like a bomb has gone off,” says dentist Molly Rodgers. To save the tooth, a dentist drills out the harmed dentin and refills the center of the tooth.