The surgical management in cases of a membrane perforation might also influence the overall postoperative outcome and complications. Although the sinus lifting procedure has been established for many years now, there are no evidence-based guidelines for perforation closure or indications to interrupt the procedure. To date, most existing studies recommend sealing smaller sizes of perforations with membranes (collagen, demineralized laminar bone) or fibrin glue. Additional resorbable sutures in cases of larger perforations are advisable if a complete closure of the perforation is feasible [5, 8, 28] but have not been shown to be superior as the coverage of larger perforations with membranes alone were shown to be effective [9, 12, 28, 29]. A lateral approach in sinus lifting might be obligatory to securely detect and therefore treat a perforation. In the primary assessment of the study, four procedures had to be terminated due to an extensive perforation, thin mucosa, or a retention cyst. After waiting 6 months, the procedure was repeated without any complications [11]. Other studies also recommend interrupting the procedure, when the repair does not seem to be sufficiently possible [7, 17].

In this study, a one-stage procedure was significantly less likely to result in membrane perforation. Implant insertion was immediately performed only if the estimated residual bone quality ensured high primary stability, which was consistent with a study by Cha et al. [3]. Residual bone height between 1 to 3 mm was not favorable for immediate implant insertion after sinus floor elevation with a lateral approach [16]. Therefore, the surgeon should be aware that a two-stage approach includes the risk of further complications relating to the surgical procedure itself. A recently published study revealed a significantly higher risk for soft-tissue complications in cases of a second procedure [30].

Due to the retrospective nature of this study, the management in cases of perforation did not follow a standardized protocol. Most of the studies regarding the outcome after membrane tear rely on retrospectively acquired data, and similar to in our study, with an inhomogeneous study cohort with different approaches in cases of perforation, there were different augmentation procedures, including grafts and grafting material, one- and two-stage procedures and different types of dental implants. Based on our data and regarding the limitations within the design of this study, we might conclude that a perforation of the Schneiderian membrane, if recognized and properly addressed, does not necessarily endanger or negatively impact the stability of the augmented bone or implant survival. To systematically assess the impact of membrane perforation on the augmented sinus and implant survival, prospective studies and higher case numbers should be considered in the future.