Pain in the back of the tooth and pain in opening the mouth may be caused by pericoronitis, temporomandibular arthritis, periapical inflammation and other diseases. 1. Peri-coronary inflammation: patients with wisdom teeth peri-coronary inflammation will have the symptoms of difficulty in swallowing and limitation of opening the mouth, mainly due to the incorrect position of wisdom teeth eruption, which leads to inflammation of the soft tissues around the crowns of the teeth, causing pain. 2. Temporomandibular arthritis: As a result of temporomandibular arthritis, both sides of the temporomandibular jaw are not in an axial position during activities, so when opening the mouth and chewing food, there will be pain. 3. Periapical inflammation: When there is inflammation at the root tip, there will be some irritating substances or pain-causing factors, which will stimulate the pain receptors in the periodontal membrane near the tip of the root or the local tissues will be swollen, resulting in pain at the back of the tooth and pain when opening the mouth. Pain in the back of the tooth and mouth may also be seen in dental caries, periodontitis and other diseases, if the symptoms of pain in the back of the tooth and mouth, persistent and unrelieved, you need to consult a doctor for timely treatment.