A 33-year-old man, a metalworker, complains of pain and itching in the gums, gingival hemorrhages intensifying during tooth brushing. The onset of the disease was 1 year ago. Objectively: the gums in the area of upper and lower frontal teeth are hyperemic, swollen, and cyanotic. There are significant mineralized deposits on the teeth; the periodontal sockets are 3 mm deep and produce small amount of serous discharge. What is the most likely diagnosis?