Final answer:
The probable diagnosis for the patient with severe toothache, swelling, fever, and moth-eaten radiolucent appearance of the mandible is acute osteomyelitis.
Step-by-step explanation:
Given the symptoms described, such as a history of a large carious lesion in a mandibular right molar, severe toothache, submandibular facial swelling, fever, purulent exudation through the gingival sulcus, lymphadenopathy, and radiolucent appearance of the mandible, the most probable diagnosis is C. acute osteomyelitis. These symptoms suggest an infection has spread to and affected the bone, consistent with osteomyelitis. Acute osteomyelitis is a severe bone infection that often arises after a chronic tooth infection spreads beyond the tooth's root and into the surrounding bone.