Tooth decay can be divided according to the different degrees: 1.Only the root is left after the whole crown is destroyed due to the decay. In the past, the root of anterior teeth was basically extracted, and only in the dentistry department of big hospitals, the root treatment was taken to repair the crown by using the root, and this method is called pile crown. With the development of science and technology, especially the successful research of composite resin material for anterior teeth, the roots that should be extracted in the past are now preserved, and the roots are used for piling, and the light-curing composite resin is used to repair the defective teeth. 2.Deep caries (means the caries is almost close to the pulp) The self-conscious symptoms of deep caries are obvious. For example, the stimulation of cold wind can cause tooth soreness and pain, and when it is serious, it produces continuous pain. The treatment of deep caries needs to be based on the situation of cavity, and carefully ask whether there is a history of persistent pain, and take different treatment methods respectively: (1) simple cold, hot stimulation pain, can be padded with a layer of drugs to protect the pulp, observe the children’s day, if no longer produce pain, can keep part of the material, the outer layer of similar color composite resin for permanent filling. (2) With atypical pain, that is, in addition to pain during cold and hot stimulation, there is atypical toothache. Toothache can be a hidden pain, such as a hidden pain for a while at night, but it does not affect rest. In addition, toothache can be manifested as a prolonged pain when subjected to a single cold or hot stimulus, and a strong pain response when a pulp activity test is performed. The treatment of the above toothache is to remove the pulp completely. (3) Removal of tooth decay and pulp exposure. When removing the decayed tooth, the pulp can be exposed near the pulp angle. In this case, the treatment should be combined with the medical history and treated separately. If there is no atypical toothache after careful medical history, it means that there is no inflammation in the pulp, and measures to preserve the living pulp, such as direct pulp capping, are often taken in clinical practice. If there is a history of atypical toothache, it means that the pulp has inflammation, and the treatment measures of removing the pulp are often taken clinically. 3.Medium caries refers to the caries is deeper than shallow caries, in addition to enamel caries, there is also shallow dentin caries. This kind of cavity can produce conscious clinical symptoms, such as when eating popsicles, drinking cold food such as ice-cold soda, or eating hot water or hot meal can cause uncomfortable symptoms. The treatment of medium caries needs to pad a layer of protective medication so that the tooth tissue is not affected when stimulated by cold or hot food and plays the role of protecting the dental pulp. The outermost layer is filled with permanent resin material. 4.Shallow caries refers to shallow cavities, which may only have enamel decay. Superficial caries usually has no self-conscious state brain bed symptoms. The color change occurs at the early stage. As the decayed tissue in the cavity is black, it is easy to find the black change on the incisor in the mirror. This kind of cavity, if filled directly, can prevent the expansion of caries.