A periapical radiograph shows internal root resorption. Under the AAE Case Difficulty Assessment, how is this tooth classified?

Correct answer: C. High difficulty

• A. Minimal difficulty describes a straightforward anterior or premolar case with a single, mildly curved canal in a cooperative patient with no complicating history.
• B. Moderate difficulty covers factors such as moderate canal curvature, a crown restoration, or a previously initiated treatment — not a resorptive defect.
• C. CORRECT. The AAE Endodontic Case Difficulty Assessment Form places INTERNAL RESORPTION in the HIGH DIFFICULTY category. The resorptive defect is an irregular, undercut space that cannot be shaped by conventional instrumentation, is difficult to disinfect, and is difficult to obturate without voids — usually requiring a thermoplastic technique or MTA. Perforating internal resorption is more complex still.
• D. The AAE form explicitly lists resorption among its difficulty criteria.

Note: Other HIGH difficulty markers on the AAE form: extreme canal curvature or S-shaped canals, canal obliteration, prior perforation or separated instrument in the apical third, and roots with open apices requiring apexification.