A patient complains about pain in the 51 tooth that is getting worse during cutting. Anamnesis data: the patient underwent treatment on account of pulpitis of the 51 tooth, the tooth was treated with devitalizing paste, the patient didn’t come to see a dentist for the second time. Objectively: carious cavity of the 51 tooth is closed by dentin layer. Percussion is painful. Mucous membrane in the root apex projection of the 51 tooth is hyperemic, edematic, palpatory painful. Make a diagnosis: