A 25-year-old patient presents with a severe, spontaneous, throbbing pain in the mandibular right first molar (tooth 46) that worsens when lying down.
Clinical examination reveals a deep carious lesion.
The tooth is tender to percussion, and pulp vitality testing with a cold stimulus elicits a sharp, lingering pain.
A periapical radiograph shows a widened periodontal ligament space around the mesial root apex.
What is the most likely diagnosis for the pulp and periapical tissues?
