Guided Sinus Surgery: Enhancing Precision in Lateral Window Sinus Floor Augmentation
The limited vertical dimension of alveolar bone in the posterior maxilla poses a challenge in implant dentistry, often stemming from periodontal damage or an enlarged maxillary sinus. However, advancements in material science have enabled the development of stronger, shorter implants (≤8mm) that demonstrate promising survival rates (Lemos et al., 2016). In such cases, implants may require sinus floor elevation (SFE), with lateral window and transalveolar approaches offering viable options, both exhibiting comparable success rates to implants placed in normal bone (Pjetursson & Lang, 2014; Jensen & Terheyden, 2009).
Lateral window SFE, well-suited for residual crestal bone heights of <5mm, is a well-established technique, often employed as a staged procedure prior to implant placement (Boyne & James, 1980). The effectiveness of SFE hinges on creating an optimal window, considering factors such as size, location, bone wall thickness, convexity, adjacent teeth, sinus septum, and arterial anastomosis (Stacchi et al., 2020). An "optimal" window should be large enough to provide adequate visualization and instrument access, without compromising graft retention or diminishing vital bone wall (Zaniol & Zaniol, 2017). A recommended window size for a single implant is 5mm vertically and 8-10mm horizontally, ideally positioned mesially and lower relative to the sinus (Zaniol & Zaniol, 2017).
Maintaining a thin bone wall (≤1mm) is advantageous, while the surgeon must carefully navigate the curvature and length of adjacent teeth to avoid complications. The presence of a sinus septum, encountered in approximately 30% of patients, poses a risk for membrane perforation, necessitating careful consideration in surgical planning (Testori et al., 2019). Addressing arterial anastomoses is crucial to prevent intraoperative bleeding, particularly the infraorbital artery, posterior lateral nasal artery, and the posterior superior alveolar artery (Rosano et al., 2009). Meticulous planning and execution, considering these anatomical parameters, contribute significantly to the success of sinus floor elevation procedures.
Guided sinus surgery has undergone significant advancements due to technological progress, effectively addressing challenges in implant dentistry associated with limited alveolar bone in the posterior maxilla. Prior to the widespread adoption of cone-beam CT (CBCT), surgeons relied heavily on their anatomical knowledge and surgical experience, with extraoral and intraoral X-rays providing limited insights into sinus size and surrounding structures. Surgical adjustments were made intraoperatively based on visual and tactile cues. The advent of CBCT imaging revolutionized surgical planning by providing detailed three-dimensional visualizations of anatomical structures, including intraosseous blood vessels and the sinus septum (Neugebauer et al., 2010). Modern planning software facilitates precise identification of the optimal lateral window (Neugebauer et al., 2010).
Technological advancements have also led to the development of computer-aided implant surgery (CAIS), enabling precise implant osteotomy and placement using CAD/CAM technology (Smitkarn et al., 2019; Tahmaseb et al., 2018). This principle has been applied to create surgical guides for lateral window sinus floor augmentation (Strbac et al., 2020; Zaniol et al., 2018).
The clinical application of sinus guides is exemplified in cases utilizing CBCT imaging and virtual study models imported into implant planning software (coDiagnostiX version 10.2, Dental Wings). The surgical guide is designed to align closely with the anterior and inferior borders of the maxillary sinus, ensuring adequate space for instrumentation at the target grafting area. The cut profile, drawn within the planning software, outlines the window, suggesting the superior extent of the mucoperiosteal flap for adequate exposure (Zaniol et al., 2018). While the guide does not physically guide instruments, it serves as a reference for the freehand creation of the window, offering flexibility due to its slim design. Surgical stability is maintained by covering the occlusal surface of all maxillary teeth.
Successful cases demonstrate the efficiency and safety of antrostomy with sinus guides. In one example, simultaneous sinus floor elevation (SFE) and implant placement are achieved using a surgical guide incorporating both features (Sun et al., 2020). Proper prosthetic setup precedes virtual implant placement, considering axial loading and a periodontally-friendly emergent profile design. The sinus window is strategically designed to allow easy access to the target area for SFE and grafting, taking into account anatomical characteristics.
In conclusion, the synergistic combination of advanced imaging, CAD/CAM technology, and 3D printing enhances precision in lateral window sinus floor augmentation. The meticulous planning facilitated by these tools reduces surgery time and improves safety, benefiting patients and justifying the investment in these technologies.
