The edentulous posterior maxillary region often presents with unique challenging conditions in implant dentistry. Limited bone height secondary to pneumatization of the maxillary sinus and the resorption of the alveolar ridge preclude in many instances the installation of dental implants. To compensate for the lack of bone height, several treatment options have been proposed.

The most conservative and minimally invasive technique is the placement of short implants with less technically demanding operation, lower expense, fewer surgical procedures, and fewer complications. Another therapeutic alternative is to use the residual, taking advantage of the residual bone, present in the anatomic buttress, as the frontomaxillary, frontozygomatic, and pterygomaxillary buttress, using zygomatic implants or pterygoid implants, combined with anterior standard implants; both of them have reported good survival and success rate. Another alternative is regenerative procedure of the maxillary sinus encompassed by two main approaches: the lateral windows approach and the transalveolar or crestal approach. The technique of sinus augmentation was first published in 1980 by Boyne and James and subsequently by Tatum. It is most often used when severe degree of resorption is present, which precludes the installation of short implants and/or the achievement of primary stability. The transalveolar or crestal approach was first described by Summers in 1996. This approach is commonly used when the degree of resorption is lower, and it is possible in the installation of dental implants with primary stability. Both techniques have shown high survival rates similar to those implants installed in the non-grafted posterior maxilla.

The maxillary sinus is a paired pyramid-shaped paranasal cavity lined with thin respiratory ciliated epithelium that serves in the transportation of fluid secretions toward the ostium. This lining of the maxillary sinus cavity is called the Schneiderian membrane. The integrity of the membrane is of paramount importance for the performance of sinus augmentation procedures and the avoidance of potential complications. However, perforation of the membrane remains as the most commonly occurring complications approximately in 15.7% of the cases. Moreover, this complication can occur inadvertently. However, some evidence suggested that these perforations seem not to have a detrimental effect on implant survival or the appearance of further complications. In fact, recent investigations have found greater vital bone when perforations occurred. As such, the survival rate does not differ between implants placed in perforated and non-perforated sinuses not statistically significantly different.

Intrusion of dental implants into the maxillary sinus perforating through the Schneiderian membrane is considered a cause of undesirable complications. However, this phenomenon has never been properly evaluated and systematically studied. For this reason, the aim of this systematic review was to assess the implant survival and complication rates of implants intruding into the sinus cavity.