Swelling behind the big teeth is mainly caused by wisdom tooth pericoronitis, periodontitis or periapical disease, and it is recommended to carry out wisdom tooth pericoronitis rinsing, periodontal treatment or root canal treatment. 1. Wisdom tooth pericoronitis is the inflammation and swelling of the gums at the crown of the wisdom tooth due to food impaction and bacterial infection, the treatment is to rinse and medicate the pericoronary flush of the wisdom tooth in order to reduce the swelling rapidly. 2. Periodontitis is the lack of good oral care, resulting in chronic hyperplasia of periodontal tissues under the stimulation of bacteria and other symptoms, acute periodontal disease can also appear gum abscess; only through periodontal treatment (such as ultrasonic scaling) in order to effectively reduce the swelling. 3. Apical periodontitis is an abscess of the gums caused by the spread of inflammatory necrotic material from the root canal to the periodontal tissues at the root tip; the only way to cure the above symptoms is to carry out endodontic treatment to clean up the infected necrotic material in the root canal. It is recommended to consult a doctor in time for diagnosis and treatment to avoid aggravation of the symptoms.