Which feature is MOST useful in distinguishing idiopathic osteosclerosis from ossifying fibroma radiographically?

Correct answer: C. Expansion of the cortical plates

• A. Neither lesion is typically painful. Both are usually asymptomatic incidental findings, so pain does not separate them.
• B. Bleeding on probing reflects gingival inflammation and has no relationship to either intraosseous lesion.
• C. CORRECT. CORTICAL EXPANSION is the discriminator. OSSIFYING FIBROMA is a true benign NEOPLASM: it grows, displaces adjacent structures, expands and thins the cortical plates, and characteristically shows a well-defined border with root divergence or resorption. IDIOPATHIC OSTEOSCLEROSIS (dense bone island) is a developmental anomaly of no consequence — it is a static, well-defined radiopacity with NO expansion, no capsule, no root displacement and no growth over time.
• D. Age overlaps substantially between the two and is not a reliable discriminator.

Note: Idiopathic osteosclerosis requires NO treatment — only periodic radiographic observation to confirm it is not enlarging. Ossifying fibroma requires surgical enucleation because it will continue to grow and expand.