A 40-year-old patient with mandible fracture consulted a doctor 3 weeks after immobilization of fragments because of pain and body temperature rise. Objectively: a slight swelling in the mental region, mucous membrane of alveolar process in the area of the 21|12 teeth is hyperaemic, edematic, palpatory painful. Overtooth splint on 54321|12345 teeth is in satisfactory condition, no occlusion abnormalities were detected. The patient was diagnosed with acute purulent periostitis of mandible. What surgical action is indicated?