الفهرس 
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Abstract
Sufficient bone quantity and quality are essential for proper dental implant placement especially in case of the posterior maxilla where resorption of alveolar bone and pneumatization of maxillary sinus cavity often compromises dental implant therapy.
Sinus augmentation has evolved into a predictable surgical modality for increasing the vertical height that is needed for the successful placement of dental implants. Lateral wall and crestal approach are the main techniques for maxillary sinus augmentation.
Lateral wall technique was first described by Tatum and subsequently, Boyne and James in 1980.This approach results in more predictable outcome in cases with minimum amount of alveolar ridge height. Although the procedure has been proven to be predictable with high success rate, various complications have been reported during surgery or the postoperative period.
Understanding of regional nutritive arteries can allow clinicians to prevent local bone necrosis and also optimize regional healing via proper vascularization of the graft materials. The blood supply of the maxillary sinus and Schneiderian membrane comes from the maxillary artery. Posterior superior alveolar artery (PSAA) and infraorbital artery (IOA) are the branches of maxillary artery that supplies lateral sinus wall and overlying membrane. Both arteries give extra osseous and intraosseous branches and these branches form anastomosis.
The larger the size of the vessel, the greater the risk of bleeding severity. These vessels should be taken into consideration during sinus augmentation because of the potential risk of bleeding during the procedure
Based on a number of previous studies, the PSAA is always found in the sinus wall; however, its location, diameter and route might be different. On the other hand, the distance from the PSAA to alveolar ridge depends on the atrophy of the maxillary bone.
Panoramic radiography is used frequently in clinical dentistry. However, the anatomy of the maxillary sinus cannot be assessed accurately with panoramic radiography only; because overlapping of anatomical structures is inevitable and because of the inherent distortion and the two-dimensional nature of technique.
Cone Beam Computed Tomography (CBCT) is a very useful diagnostic tool commonly used to plan advanced surgical procedures such as implant placement. CBCT images and volumetric reconstructions provide valuable information including bone morphology in the three dimensions of space, presence of concomitant pathoses and location of important anatomical landmarks, including the PSAA canal
Thus, the purpose of this study is to evaluate the prevalence and morphology of the posterior superior alveolar artery canal on cone beam computerized tomography (CBCT) scans in a sample of Egyptian Population.
A retrospective study was performed using cone beam CT images of 600 maxillary sinuses to evaluate the posterior superior alveolar canal. Of the 600 sinuses examined the PSAA was detected on 552 sinuses (92%) with 82.2% of the arteries being intra-osseous, 13.8% under the sinus membrane (intra-sinus) and 4% external to the lateral wall of the sinus (extra-osseous).
The canal diameters were less than 1 mm in 55.8%, 1-2 mm in 40.2% and more than 2 mm in 4% of the cases. Range of diameter of the canal was 0.33-2.64 mm with a mean diameter 0.92 mm. The mean distances from PSAA canal orifice to sinus floor and to alveolar ridge were 7.7±2.2 and 17.8±2.5 respectively.
Therefore, our study has underlined the importance of using CBCT before lateral wall sinus augmentation and implant placement.