A 46-year-old patient complains of spontaneous pain in the 36 tooth. Its crown is decayed. The patient presented with edema of soft tissues adjacent to the mandible. Body temperature rose up to 39,0°C, the patient has chill. Examination of the oral cavity revealed a pronounced edema of the left mandibular alveolar process on the vestibular and oral side (acute periostitis); the 35, 36, 37 teeth are mobile, subgingival pockets contain purulent exudate; their percussion causes acute pain. Positive Vincent's symptom is present. What is the presumptive diagnosis?