A panoramic radiograph shows a horizontally erupting lower left third molar pushing against the second molar, which shows resorption on its distal root surface. This is which type of resorption?

Correct answer: A. External root resorption

• A. Correct. Pressure from the impacted/erupting third molar against the adjacent root causes EXTERNAL (pressure-induced) root resorption on the second molar's distal surface.
• B. Internal resorption originates within the pulp/canal, not from external pressure.
• C. Replacement resorption follows ankylosis (bone replacing root), not adjacent-tooth pressure.
• D. Surface resorption is minor and self-limiting, not the pressure resorption from an impacted molar.