This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Causes of postoperative sensitivity with amalgam restorations include all of the following except _____. 
Select and explain. 
A. Lack of adequate condensation, especially lateral condensation in the proximal boxes., B. Voids., C. Extension onto the root surface., D. Lack of dentinal sealing.
C: Extension onto the root surface.
Answer: C: Extension onto the root surface. 
Explanation: The primary causes of postoperative sensitivity for amalgam restorations are voids (especially at the margins), poor condensation (that may result in a void), or inadequate dentinal sealing. Extension onto the root surface does not necessarily result in increased sensitivity.