A cavity, also called tooth decay, is a hole that forms in your tooth. Cavities start small and gradually become bigger when they’re left untreated. Because many cavities don’t cause pain in the beginning, it can be hard to realize that a problem exists. Regular dental appointments can detect tooth decay early. According to the Mayo Clinic, cavities and tooth decay are some of the most common health problems in the world. Anyone with teeth can develop cavities, including babies. Finding out that you have a cavity might come as a surprise. This is especially true if you think you have a good oral hygiene routine. However, even if your dentist delivers this news, there are ways to treat a cavity and prevent new ones from forming.