"It's common, particularly during cold and flu season." That's because the roots of the upper molars are close to the maxillary sinuses, the pair of sinus cavities located behind the cheekbone.

Aspergillus is the primary causative organism. It usually involves a single sinus, most often the maxillary sinus. [19] Presentation is typically an incidental finding on the CT scan of the head ...

(The Water's view is a posterior-anterior radiograph taken with the neck extended to permit an unobstructed view of the maxillary sinuses. It is taken in an upright position to better identify ...