Fig. 8. Blood supply of the sinus. There are three areas in the sinus where blood vessels may be encountered during sinus augmentation procedures for implants. On the inflection point between hard palate and alveolar ridge in the posterior maxilla, the greater palatine neurovascular bundle is located embedded in soft tissue. This inflection point is matched in the internal sinus anatomy and presents a landmark that can be palpated with sinus curettes during sinus membrane elevation or seen on cone beam CT images in this patient. It is important to avoid instrumenting the area above this inflection point as branches of the lateral posterior nasal arteries may be encountered superior to this area. Injuring these blood vessels can lead to significant sinus bleeding that is difficult to stop without sinus tamponade. Often on cone beam CT images, we see a small blood vessel channel midway within the lateral wall of the sinus, which likely is the posterior superior alveolar artery and vein. This and the interior medial wall sinus inflection point can serve as anatomic landmark to delineate a risk zone superior to it and to limit sinus augmentation inferior to it