A 49-year-old man complains of progressing reduction of mouth opening, pain on the left when swallowing, severe deterioration of his general well-being, temperature increase up to 39.3°C. Destroyed tooth 38 presents with acute pain. Objectively the face is symmetrical, the submandibular lymph nodes on the left are enlarged and painful on palpation. Palpation under the left mandibular angle and in the left retromandibular area provokes sharp pain. Mouth opening and movement of the mandible to the left are signi?cantly reduced. The left pterygomandibular fold is hyperemic and in?ltrated. What is the most likely diagnosis?