Cavity is caries, tooth decay, caries first of all its location, occurs on the hard tissues of the teeth, that is, on top of the white part of the teeth that can be seen. What causes it? First of all, bacteria as the dominant factor, there are about 700 kinds of bacteria in the mouth, which are normal. Bacteria plus if you do not pay attention to oral hygiene, there are food debris attached to the surface of the teeth, bacteria combined with food debris to carry out chemical reactions, will be the surface of the teeth for chronic, progressive destruction, it is a long time to cause obvious symptoms of the disease. Therefore, when there is caries, it is important to deal with it as soon as possible in the early stages. Because in children, milk teeth are not as hard as permanent teeth in adults, caries progresses relatively faster than in adults. Although it is a chronic, but in children, especially infants and young children, it will be common to see some rapid development of violent caries, can occur in a short period of time more serious tooth destruction. Therefore, caries, whether in adults or children, should be detected and treated early, with regular checkups at the hospital.