This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
Most common cause of oroantral fistula 
Select and explain. 
A. TB, B. Penetrating injury, C. Tooth extraction, D. Iatrogenic
C: Tooth extraction
Answer: C: Tooth extraction 
Explanation: A most impoant cause of oroantral fistula is dental extraction. It is a communication between the antrum and the oral cavity. Roots of the second premolar and upper molars are closely related to the antral cavity and their extraction may lead to fistula formation. It presents with regurgitation of food foul smelling discharge filling nose and inability to build positive or negative pressure in the mouth. Ref: Textbook of diseases of ENT; PL Dhingra; 7th edition, pg 208