Under the American Association of Endodontists Case Difficulty Assessment, a single-rooted tooth with INTERNAL RESORPTION falls into which category?

Correct answer: A. High difficulty

• A. CORRECT. Any RESORPTIVE DEFECT — internal or external — places a case in the HIGH DIFFICULTY category regardless of how simple the root anatomy otherwise appears. The resorptive lacuna is an irregular space that files cannot shape, it may perforate the root, and it requires specialised obturation such as warm vertical compaction or an MTA plug. High-difficulty cases are those with a substantial risk of complication and are appropriately referred.
• B. Resorption is explicitly listed on the AAE form under 'Additional Considerations' as a high-difficulty factor.
• C. Moderate difficulty covers moderate curvature (10–30°), moderate calcification, a previously initiated treatment, or a tooth with a crown or post.
• D. Minimal difficulty describes a straightforward anterior or premolar with a single, straight, fully formed canal, normal periapex and no unusual medical or access considerations.

Note: High-difficulty triggers worth memorising: extreme canal curvature (>30°) or S-shaped canals, canals that cannot be negotiated, calcification, resorption (internal or external), open apex, prior perforation or separated instrument, and significant trauma history.