A 28-year-old woman came to a dentist with complaints of acute paroxysmal spontaneous pain in her upper left tooth. The pain attacks last 5-10 minutes. Objective examination detects a carious cavity in tooth 26. The carious cavity has a narrow entrance, is located within the softened non-pigmented peripulpal dentin, and does not communicate with the pulp. chamber. Probing of the cavity floor is painful in the projection of the mesiobuccal pulp horn. The response to cold is painful and prolonged. Percussion is painless. Electric pulp testing i-15 microamperes. What diagnosis can be made in this case?