The occlusal muscle is attached more widely at the angle of the jaw, and the occlusal gap is formed between the occlusal muscle and the mandible. Infection of the occlusal space mainly comes from pericoronitis of the mandibular wisdom teeth, and may also come from inflammation or abscess of the root tip of the mandibular molar. The symptoms of infection of the occlusal space are mainly several: 1. Swelling and hardening centered on the angle of the jaw, with significant pain in the area of the angle of the jaw, and there will be severe restriction of opening, that is, inability to open the mouth; 2. Abscess formation due to the thicker occlusal muscle: it is usually difficult to break and to feel fluctuating sensation. If the inflammation lasts for more than a week, there is sunken edema and there is pus from the puncture, an incision and drainage should be actively done; 3. Due to the infection, the patient is prone to high fever symptoms: if a routine blood test is done, the patient will be found to have an increased total white blood cell count and an increased neutrophil ratio.