Which of the following is a radiolucent lesion?

Correct answer: C. Periapical granuloma

• A. Condensing osteitis (focal sclerosing osteomyelitis) appears as a RADIOPAQUE lesion associated with a tooth with low-grade chronic pulpal inflammation — it is the OPPOSITE of radiolucent.
• B. Idiopathic osteosclerosis appears as a RADIOPAQUE lesion in the periapical region of vital teeth — not radiolucent.
• C. A PERIAPICAL GRANULOMA appears as a RADIOLUCENT lesion at the root apex — it is a chronic inflammatory response to pulpal necrosis, consisting of granulation tissue. It appears as a round-to-oval radiolucency at the apex, typically well-defined. Contrast with RADIOPAQUE lesions: condensing osteitis, idiopathic osteosclerosis, hypercementosis.
• D. Osteoarthritis of the TMJ shows flattening and sclerosis of the condyle (radiodensity changes) but is NOT primarily described as a radiolucent lesion.