A 9-year-old girl complains of persisting pain in tooth 11 that one month ago sustained a trauma resulting in broken crown. The tooth received no treatment. Objectively the 1/4 of the tooth crown of 11 is broken off, the remaining crown is grayish, the dental cavity is not exposed. Percussion is acutely painful. The mucogingival fold is hyperemic and acutely painful on palpation. Make the diagnosis: