A 23-year-old patient complains about gingival hemorrhage during tooth brushing and eating solid food. Objectively: gingiva of the frontal part of mandible is hyperaemic, edematic, it bleeds on palpation. Mucous membrane of the oral cavity as well as gingiva in other regions present no changes. The patient has deep overbite. Teeth are stable except for the 41 and 31 (I degree of mobility). X-ray picture shows resorption of interalveolar septa by 1/3 of root length in the region of the 42, 41, 32, 31 teeth. What is the most likely diagnosis?