External factors 1.Physical factors: Long-term chronic stimulation: such as long-term chronic stimulation of root, crown, sharp tooth tip and bad restoration can lead to the occurrence of tongue and cheek cancer; smoking and lip cancer, burns (sunlight and ultraviolet radiation) and skin cancer; trauma and scar cancer, injury and jaw sarcoma are closely related to each other; radiation therapy can cause secondary radiological cancer. 2.Chemical factors: It is the earliest factor that has been paid attention to and confirmed. (1) Alkylating agents: such as organic pesticides, sulfur mustard, etc. (2) Polycyclic aromatic hydrocarbon compounds: 3,4-benzopyrene (3) Aminoazoids: dyes (4) Nitrosamines (5) Mycotoxins and phytotoxins: Aspergillus flavus, thapsigargin, etc. (6) Other: heavy metals such as: coal tar can cause skin cancer, oral cancer is related to smoking, cigarette oil contains benzopyrene, N-nitrosoquatidine, arsenic and other carcinogens, alcohol Carcinogenesis has been confirmed, and has a synergistic effect with tobacco carcinogenesis, and is seen as a promoter. 3. Biological factors: Experimentally, viruses can cause the occurrence of malignant tumors, such as: nasopharyngeal carcinoma and malignant lymphoma are related to EBV, immunodeficiency virus (HIV) is related to AIDS, and T-lymphotropic virus (HTLV) is related to T-cell lymphoma. In recent years, the relationship between human papillomavirus (HPV) and oral cancer has aroused people’s interest. 4.Nutritional factors: Changes of certain vitamins and trace elements are related to the occurrence of oral cancer. Animal experiments have proved that vitamin A and retinoic acid deficiency are prone to cancer caused by chemical carcinogens; selenium deficiency of trace elements is prone to tumor. Intrinsic factors 1. Neuropsychiatric factors: Excessive mental tension → hormone (corticosterone) level in blood ↑ → changes in the relationship between certain compounds → white blood cell viability ↓ → immune organ weight ↓ → immune function ↓. Excessive mental tension and disruption of psychological balance cause dysfunction of human body, which is a favorable factor for tumor development. 2. Endocrine factors: endocrine dysfunction can cause some tumors. For example, the chance of oral cancer after breast cancer and cervical cancer is greatly increased, and some people report that the risk of female salivary cancer patients to have breast cancer again is 8 times of normal people. Repeat cancer is related to endocrine disorder. 3. Immune status of the body: In the early stage of malignant tumor patients, especially in the late stage, the immune function decreases. The incidence of tumor is high in patients with immune deficiency disease and long-term use of immunosuppressants, and the immune status of the body is also related to the prognosis. 4, genetic factors: in the occurrence of malignant tumors can not be ignored, clinical see a family history. It is expressed in the form of “susceptibility”, and what is inherited is not the cancer itself, but the “individual quality” of susceptibility to cancer, of course with environmental involvement. Gene mutation: Since the mid-1980s, oncogene research has been attracting attention, and now it has become a hot topic. There are oncogenes and oncogenes in human chromosomes, and the development of tumor is related to the activation of many oncogenes and inactivation of oncogenes. Under normal circumstances, oncogenes and oncogenes are interdependent and mutually restrained.