A 19-year-old patient came to a dentofacial clinic with complaints of pain in the gonial angle on the right, impaired mouth opening and painful chewing. The signs had been persisting for 5 days, emerged spontaneously and had been aggravating gradually. Mandibular contracture is of the III-degree. On examination of the oral cavity: hyperemia, edema of the retromolar space on the right, hood-shaped mucosa from under which pus is being discharged and 2 tooth tubercles can be detected. X-ray shows oblique medial tooth position. Make the diagnosis: