A 20-year-old patient complains about gum itching, gingival haemorrage during tooth brushing and eating, unusual look of gums. He has been observing these presentations for the last 1,5 year. It is known from the patient’s anamnesis that he has been taking diphenylamine anticonvulsants for 2 years. Objective examination revealed gingival hyperemia and edema. In the frontal part the gums cover vestibular surface of teeth by 1/2 of their height. Along the loose gingival edge growth of granulation tissue is present, probing causes gingival haemorrage. No roentgenological changes were revealed. Make a diagnosis: