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: ENT
Which sinus is involved in a patient with a toothache and sinusitis 
Select and explain. 
A. Maxillary, B. Ethmoid, C. Frontal, D. Sphenoid
A: Maxillary
Answer: A: Maxillary 
Explanation: Dental infections are an important source of maxillary sinusitis. 
Roots of premolar and molar teeth are related to the floor of sinuses and may be separated only by a thin layer of mucosal covering. 
A peripheral dental abscess may burst into the sinus or the root of a tooth during extraction may be pushed into the sinus.
In the case of oroantral fistula following tooth extraction bacteria from the oral cavity enter the maxillary sinus.