A 14-year-old girl complains of a pulsing pain in her upper left teeth that lasts for 3 days already and sharply increases on biting. Objectively, her tooth 26 has a deep carious cavity that does not communicate with the dental cavity. Probing of the cavity floor is painless. Vertical and horizontal percussion is sharply painful. The mucosa in the area of tooth 26 is hyperemic. What is the provisional diagnosis in this case?