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Implant rehabilitation in the edentulous upper jaw can be achieved with fixed and removable prostheses. Fixed prostheses are totally supported by implants, whereas removable prostheses can be supported by the mucosa with implant retention or totally supported by an implant. In totally edentulous patients, fixed implant rehabilitation shows higher survival rates compared with removable prostheses.1
The possibility of rehabilitating an arch with a fixed prosthesis with predictable long-term success has been an important goal in dentistry.2 However, the rehabilitation of a completely edentulous maxilla is often associated with anatomical limitations from decreased bone volume, especially in the premolar and molar regions. Bone atrophy progresses rapidly during the first year after tooth loss and continues thereafter. It is affected by long-term use of removable prostheses and relative maxillary sinus pneumatization.3
For moderate to severe maxillary atrophy, in the presence of surgically challenging sinus anatomy, the apex of the posterior implants can be angled anteriorly, passing transsinus, to apically fix at the lateral piriform rim into the lateral nasal wall. The most important bone for apical fixation of implants in this setting is the lateral nasal bone mass with the maximum available bone found at the piriform rim above the nasal fossa4,5. This area, designated the M point, also can engage two implants placed at 30-degree angles (Figs. 1a-b). The transsinus implants are then grafted and possibly placed into immediate function, depending on the level of crestal stability present.