1.The milk teeth do not fall off overdue and have affected the eruption of permanent teeth or the root tip of milk teeth is exposed, resulting in ulcerative gingivitis. 2.The crown caries is more serious and can’t be repaired, and at the same time, there is lesion in the root of the tooth, which is not suitable for making pile crown or covering denture. 3.Serious periapical lesion, which cannot be cured by root canal treatment or apical resection etc. 4.Serious periodontal disease, resulting in frequent overflow of pus from the gums, destruction and resorption of alveolar bone, loosening of teeth by more than 3 degrees, loss of chewing function, and ineffective treatment. 5, no teeth, misaligned teeth and multiple teeth, no chewing function, and often cause plugging, bite wound mucosa or affect the denture repair; individual teeth are normal, but affect the denture repair and orthodontic needs must be extracted. 6.The obstructed teeth with abnormal position, cannot erupt and repeatedly inflamed; the inclined obstructed teeth that induce caries of neighboring teeth and prevent their filling treatment or cause root resorption of neighboring teeth should be extracted as soon as possible. 7.The teeth that cause maxillary sinusitis, osteomyelitis of jaw bone or repeatedly secondary infection of maxillofacial space. 8. Teeth that are split or fractured below the neck due to trauma and cannot be treated and repaired; or teeth located on the fracture line that affect fracture healing should be extracted. 9. Teeth that cannot be retained due to necrosis, cysts or benign masses in the jaw; or teeth located at the site of radiation treatment for malignant tumors, teeth that are prone to osteomyelitis in the jaw during radiation treatment. 10, can induce systemic diseases, such as rheumatoid arthritis, rheumatic heart disease, endocarditis, nephritis and other diseases of the focal tooth.