## 1 Introduction  
During pre-operation planning, an implantologist has to decide about the location of a dental implant based on the available bone, anatomical structures and future prosthetics. There are locations which are more--or less--favorable, such as the mandible bone which is much more suitable than the maxillary one because it is more dense, with less fat and marrow spaces, especially when the posterior parts are being considered as implantation sites [1]. In the case of severe bone atrophy in the maxillae with enlarged pneumatisation of the maxillary sinuses, it seems that the only available bone is in the front around and under nasal cavity and it is widely utilized in all-on-4, V-4 concept and nazalus implants. An alternative to these methods is zygomatic implants, but they require advance surgery, such as extensive flaps, sinus wall osteotomy and sinus membrane elevation. A third option involves an area of very good mineralization--even 139.2% greater than in the tuberosity zone--and this is called the tubero-pterygoid region [2]. In this region three bones: the maxillary tuberosity, the pterygoid process of the spinenoid bone and the pyramidal process of the palatine bone create a syphilis zone which can be used for implant anchorage, achieving great primary stabilization. There is still confusion in the literature about an adequate nomenclature of the implants and the placement sites. Terms _supergoid_> or _supergomaxillary_> and _<tuberosity implants_> are almost equally used. The term pterygoid is defined in the glossary of oral and maxillofacial implants, as positioning the implants through the tuberosity of maxilla into the pterygoid plate. Maximly tuberosity is defined as the most distal aspect of the maxillary alveolar ridge [3]. Some authors use the term _pterygomaxillary_ implants, which probably emphasizes implantation in the region of the complex anatomy of the spinenoid and palate bones [4]. Pterygoid implants go through maxillary tuberosity, but mostly anchorage occurs in the dense, compact bone of the pterygoid plates of the spinenoid bone and pyramidal process of palatal bone. In the literature regarding basal implantology, the term _<tubero-pterygoid_> implants is used most commonly and it will be used in this thesis as well [5; 6]. Maximls and the pterygoid process of the spinenoid bone are fused in a fusion zone (Figure 1a,b). Below and above the fusion zone both bones form a fissure. The distal maxilla and the pterygoid process differ in mineralization (Figure 2). Figure 1: View from distal towards both _processus pterygoid_ and into the nasal cavity (**a,b**). White arrows indicate the junction zone of the pterygoid process, maxillary tuberosity and pyramidal process (**a**). Red points mark ideal penetration points for the apex of the implants (**b**). This case shows a pronounced atrophy of the distal maxilla (centrifugal atrophy) (**b**). View of lateral distal maxilla and adjacent _processus pterygoid_ of the spinenoid bone (**c**). The literature regarding drilling directions and angulations during implant bed preparations, implant length and implant positioning is inconsistent. There are many factors that influence the right decision, such as degree of bone atrophy, maxillary sinus range diversity, soft tissue thickness or the configuration of the maxillary tuberosity in relation to the pterygoid and palatal processes themselves [7]. There are some anatomical variations of dimensional correlation of this zone which should be recognized by the operator in order to increase the surgical accuracy and to minimize the risk of complications. It is crucial to know what kind of bone configuration and anatomical structures the implant surgeon can meet in this area and how they differ among the population. One of the possible tools which can make the treatment planning more predictable is Cone Bean Computed Tomography (CBCT) and the use of a 3D printed model of the maxillae based on CBCT examination [8].