A 28-year-old patient complains of tender gums, gingival hemorrhages and pain, especially while eating, for a week. Objectively: the gums are swollen and markedly hyperemic, especially in the region of the 43,42,41, 31, 32, 33 teeth, soft plaque and tartar are present, gingival sulci are up to 2 mm deep. What is the most likely diagnosis?