# 3D Volumetric Analysis and Anatomical Considerations for
## 1 Introduction  
The maxillary sinus is an important anatomical structure due to its anatomical relationship with posterior maxillary teeth [1]. It begins to develop at 10 weeks of intrauterine development, increases to a volume of 6-8 cm\({}^{3}\) and has empty space with fluid at birth [2]. The maxillary sinus can be shown to be adult size at 18-20 years of age, and the average maxillary sinus volume is observed to be 15 cm\({}^{3}\)[3].  
The maxillary sinus pneumatication is the expansion of the sinus towards the alveolar process [4]. The causes of maxillary sinus pneumaticzation are poorly understood, but heredity, environment, infection, density of the bone, growth hormone, sinus air pressure, sinus surgery, and posterior tooth extraction can cause this process [5, 6]. Maximillary sinus preunatization and alveolar bone resorption affect the volume and height of the residual ridge [7]. Especially in the maxillary second molar region, these processes may reduce available bone; therefore, bone graft may be required during implant surgery [6, 8].  
The main techniques for sinus bone graft (SBG) are lateral window opening and crestal approach [9]. Maximillary SBG is considered a successful and predictable approach for implant surgery [7, 9]. However, sinus abnormalities can cause problems during SBG [10]. The average available bone height in dentulous maxilla is classified into 3 classes [11]. Class 1 has a 10 mm residual bone, class 2 has a 5-10 mm residual bone, and class 3 indicates a 0-5 mm residual bone height. In classes 2 and 3, SBG should be considered; especially in class 3, lateral window opening is preferred over crestal approach.  
Schneiderian membrane (SM) perforation is the most common complication during sinus bone graft, and possible causes for this include maxillary septum, pathologicalcondition, or very thin membrane [12,13]. It occurs in 11-58.3% of SBG surgeries [14, 15, 16]. SM perforation can occur while preparing the window or reflecting the membrane to access the sinus [9]. Lateral wall thickness and the angle between the lateral and medial walls are related to the SM perforation. The thickness of the lateral wall of the maxillary sinus varies according to sites. The structures such as buttress of zygomatic bone, maxillary tuberosity, and the canine eminence are related to the thickness [17]. The presence of the maxillary sinus septum is a potential risk factor for SM perforation and should be considered during maxillary SBG. When the maxillary sinus septum is present, the clinician should perform careful manipulation during floor elevation and lateral window opening. The posterior superior alveolar artery (PSAA) and infraorbital artery supply the lateral wall of maxillary sinus and SM [8]. These are the branches of the maxillary arteries that supply the lateral walls and membranes [18, 19, 20]. Since they are in close proximity to the lateral window osteotomy, severe bleeding can occur when the PSAA is damaged during maxillary sinus bone graft [12]. Damaging this vessel during surgery may interfere with the procedure as significant bleeding is introduced into the surgical field [21]. Profuse bleeding must be suppressed immediately by various methods such as firm pressure, direct ligation, bone wax, and electrocautery [21]. It is important to understand the anatomy of the maxillary sinus to avoid unnecessary bleeding and perforation of the membrane. Blood vessels with large diameters have a greater risk of bleeding during the surgery [22].  
The aim of this study was to evaluate the anatomical features, such as the height of the PSAA, lateral wall thickness of the maxillary sinus, and the volume of the maxillary sinus to be considered during maxillary SBG.