A patient complains of acute short-term toothache caused by thermal and chemical irritants. The tooth has not been treated before, the pain arose about a month ago. Objectively: on the occlusal surface of the 36 tooth there is a deep carious cavity within circumpulpal dentin with overhanging chalky enamel. Probing of the cavity floor causes slight pain. There is also short-term pain from the cold stimulus. The result of electric pulp test is 8 microamperes. What is the most likely diagnosis?