Consequently, it seems that maxillary sinus changes in relation to protruded implants inside the sinus cavity and does not statically affect to implant survival rate neither to clinical nor radiographic complications.

Several limitations could be described for the present review. Firstly, there is a lack of a control group in the included studies, to compare outcomes and complications, with implant placed in native bone, or with regenerative techniques. Second limitation was related to the types of included studies being seven retrospectives [26,27,28,29,30,31,32,33] and one prospective study [31]. Third, the lack of a reliable method to evaluate the millimeters of implants intruded inside the maxillary sinus and to assess sinus membrane perforation or not. Fourth, the analysis of the radiographic complications has been analyzed only in three studies with computerized tomography and in two studies by orthopantomographies and periapical radiographs, taking into account the difficulties of analyzing radiological complications in periapicals and orthopantomographies.

Future research should focus on performing randomized studies comparing implant intrusion in the maxillary sinus versus regenerative techniques, focusing on the rate of complications and patient outcomes. Further, it would be interesting to study the possibility of placing short implants and thus avoid access to the maxillary sinus.