Maxillary sinus. As seen in the above film, the floor of the maxillary sinus flows around the roots of the maxillary molars and premolars. The walls of the sinus may become very thin. As a result, sinusitis may put pressure on the superior alveolar nerves resulting in apparent tooth pain, even though the tooth is perfectly healthy. Note coronoid process (green arrow), zygomatic bone (blue arrow), sinus septum (yellow arrow) and neurovascular canal (orange arrows).