The most serious oral diseases belong to oral malignant tumors, such as tongue cancer, gingival cancer, buccal mucosa cancer, maxillary sinus cancer, etc. These cancers are of high malignancy, and are prone to early lymphatic metastasis and hematogenous metastasis, with a high mortality rate. In addition, interstitial infections of oral and maxillofacial region are also more serious oral diseases. Purulent inflammation caused by pericoronitis of wisdom teeth and periapical inflammation can be confined to one facial soft tissue interstitial space or spread to several adjacent tissue interstitial spaces, and even spread along the neural vessels to cause cavernous sinus thrombosis, phlebitis, cerebral abscess, septicemia and other serious complications. Maxillofacial oral diseases also include parotid gland diseases, such as pleomorphic adenoma of parotid gland, adenoid cystic carcinoma, mucoepidermoid carcinoma, which are also more malignant and belong to more serious oral diseases. Temporomandibular joint disorders, trigeminal neuralgia, and mucocutaneous pemphigoid are also serious oral diseases.