A 50-year-old patient complains about difficult mastication, teeth mobili- ty, offensive breath, gingival hemorrhage. Objectively: the gum is hyperemic and cyanotic, dental calculus is present. Parodontal pouches are 8 mm deep within upper jaw molars. The pouches of other teeth are 6 mm deep. X-ray picture shows resorption of bone tissue by 2/3-1/2 of tooth roots. What is the most likely diagnosis?