Examination shows that tooth 47 touches a deep defect in the patient's buccal mucosa. The margins of the defect are dense and clear, the floor of the defect is gray. Microscopy of the biopsy material obtained from the wall of the defects detected a purulent exudate on the floor of the defect. Under the exudate the is an area of necrotic tissue the underlying granulation tissue that transforms into mature fibrous tissue. What pathology was developed in the patient's check?