External root resorption is caused by which activity?

• A. Peripheral osteoclastic activity
• B. Intracanal osteoclastic activity
• C. Pulpal necrosis
• D. Occlusal trauma

Answer: (A)

External root resorption occurs when osteoclasts located in the periodontal ligament on the outer surface of the root are activated. These peripheral osteoclasts resorb cementum and dentin from the exterior, typically in response to inflammatory signals, trauma, or forces that stress the periodontium. This is different from internal resorption, where clastic cells inside the pulp space (intracanal) cause resorption from within the canal. Pulpal necrosis isn’t the direct driver of external resorption, though inflammation stemming from the pulp can influence other types of resorption; external resorption is fundamentally about activity in the periodontal ligament on the outside of the root.