A 16-year-old female patient complains of gingival pain and hemorrhage, a gingival deformity. Over the last 2 years the gums periodically bleed during tooth brushing. Objectively: in the region of the front mandibular teeth the gingival papillae are enlarged and reach 1/2 of the tooth crown height. The gums are swollen and tender, bleed when touched. Radiographic alterations were not revealed. What is the most likely diagnosis?