A 34-year-old male patient complains of acute spasmodic pain in the region of his upper jaw on the left that is getting worse as affected by cold stimuli. Toothache irradiates to the ear and temple. He had acute toothache of the 37 tooth one year ago, but he didn't consult a dentist. Pain recurred three days ago. Objectively: the 37 tooth has a carious cavity communicating with the dental cavity. Probing of the opened carious cavity is extremely painful. X-ray picture shows widening of periodontal fissure at the root apex of the 37 tooth. What is the most likely diagnosis?