Cavities are permanent damage to teeth and cannot be reversed. You might also hear cavities referred to as tooth decay or caries.
A cavity is simply a hole in your tooth. The cavity starts on the surface of the tooth and if untreated will continue to work its way inward towards the dentin (bony tissue beneath the outer enamel) and nerves connected to the tooth. That’s when a cavity can get really painful. It can also become infected and cause an abscess, which is a pocket of pus around inflamed tissue.