Dental caries is commonly referred to as “dental caries” or “tooth decay” and its true cause is not well understood. Dental caries is a disease in which inorganic substances in hard tissues are demineralized and organic matter is decomposed under the influence of various factors, resulting in defects in the dental tissues. It is characterized by caries at the beginning of the carious part of the teeth caries color and hardness changes, followed by the occurrence of substantial defects in the dental tissue and the formation of cavities, lesions continue to develop to the deep, can cause endodontics, periapical disease, inflammation of the jawbone and other complications, and even become an oral disease foci affecting the health of the whole body. Clinical manifestations of dental caries Dental caries is most likely to occur in the occlusal surface of the molar teeth and bicuspids in small sockets, fissure grooves, as well as the contact surfaces of neighboring teeth. The former is called fossa caries and the latter is called adjacent surface caries. In children, caries in the cervical region of the teeth is extremely rare, and can only be seen in cases of severe malnutrition or certain systemic diseases that make the body extremely weak. According to the degree of caries destruction, the clinic can be divided into shallow caries, medium caries and deep caries. 1, shallow caries caries damage only in the enamel, the initial performance of the enamel appears brown or dark brown spots or plaques, surface roughness. Followed by the formation of surface destruction. Neighboring surface caries begins to occur below the contact surface, and fissure caries mostly begins in the groove, neither of which can be easily seen in the early stage. Only in the fossa mouth can be seen, but children’s teeth fossa mouth and easy to have food pigmentation, the physician does not check carefully will be misdiagnosed or missed. Shallow caries has no conscious symptoms. Caries has reached the dentin, forming shallow dentin cavities. The patient will feel toothache to cold water, cold air or sweet or sour food, but the symptom disappears immediately after the stimulus is removed. This is because the dentin is allergic to the stimulus. The effect is good if the caries is treated in time. Deep caries Caries has reached the deep dentin layer, close to the pulp, or has affected the pulp. The child has pain to cold, heat, acid, sweet, especially sensitive to heat, and the pain still lasts for a certain period of time before gradually disappearing after the caries is removed. At this point, most of them need endodontic treatment to save the teeth. If deep caries is left untreated, the pulp becomes infected or necrotic. Bacteria can pass through the root of the tooth and reach outside the apical foramen, causing periapical inflammation. A focal infection may develop. The crown of the tooth should be extracted if it has been largely destroyed or if only a residual root remains.