Dental caries, often called cavities, are erosions of the surface of the tooth caused by the combined effects of bacteria, acids, plaque and tartar. Dental caries are common in both children and adults, and they occur most often as a result of poor dental hygiene. Dental caries are usually painless at first, but they may become painful if they spread to the nerve or root of a tooth. If left untreated, dental caries can progress to a tooth abscess, which is a more painful and potentially serious condition. Dental caries are common, but they can often be prevented by practicing good dental hygiene, including regular brushing and flossing.