Maxillary sinus pneumatization limits implant placement in the edentulous posterior maxilla. Grafted sinus floor augmentation through Schneiderian membrane elevation and space obliteration with autogenous bone grafts, bone substitutes, or a combination of the two has often been used to resolve this problem. More recently, non-grafted sinus floor elevation has been established. This is based on the concept of membrane elevation and support either by tenting technique or using space-maintaining mesh. The aim of this study was to evaluate the predictability of new bone formation after sinus floor elevation using space-maintaining mesh without graft material and to illustrate the difference between the use of bioresorbable and titanium meshes. Eight patients with bilateral sinus pneumatization were selected for implant placement in the edentulous posterior maxilla. Pneumatized sinuses were approached through the lateral window technique; these were elevated and maintained with resorbable or titanium meshes. All patients were evaluated clinically and radiographically immediately and at 6 months postoperative. At 6 months, a core bone biopsy was obtained from the planned implant position using a trephine drill, and the bone formed was examined histologically. Healing was uneventful in all patients, and radiographic, clinical, and histological evidence of new bone formation was seen in both groups. Titanium and resorbable meshes were found to be reliable and predictable as space-maintaining devices.
Implant therapy in the edentulous posterior maxilla becomes challenging in the presence of reduced maxillary bone height. Such a reduction in height may be due to maxillary sinus pneumatization. Numerous sinus augmentation techniques have been proposed to overcome this problem .
Maxillary sinus augmentation utilizing autogenous bone grafts, allografts, xenografts, or combinations of these through the lateral window approach has been the classic technique for maxillary sinus floor elevation. This can be done either in a single stage with simultaneous implant placement, or in two stages with delayed implant placement, depending on whether the available residual alveolar ridge height is sufficient to attain primary implant stability . Non-grafted sinus floor elevation is an innovative technique that aims to maintain the lifted membrane in position for a long enough time to allow stable blood clot formation during the postoperative healing stage .
The pioneering work of Lundgren et al. in 2004 showed that elevation of the Schneiderian membrane alone and its stabilization with implants resulted in new bone formation. This membrane is highly vascular and has osteogenic potential. It was found that the membrane and the antral walls together with the scaffold blood clot played an important role in the process of new bone formation. However, the results of other studies on non-supported sinus membrane elevation have shown membrane collapse into the space created and a limited amount of bone gain, hence several attempts have been made to ensure fixed sinus membrane elevation using titanium screws, resorbable devices, hollow hydroxyapatite devices, and titanium mesh
The studies by Cricchio et al. , Johansson et al. , Kaneko et al. , and Atef et al. showed the positive effects of non-grafted sinus floor elevation with different space-maintaining devices. Hence, the present study was performed to evaluate the predictability of new bone formation in non-grafted sinus floor elevation (assessed radiographically and histologically) and to illustrate the differences between resorbable and titanium mesh.
Materials and methods
A split-mouth study was conducted on a consecutive series of eight patients with bilateral partial or completely edentulous posterior maxillary ridges. All selected patients had bilateral sinus pneumatization. The right side of the maxilla was allocated to the titanium mesh group and the left side to the resorbable mesh group for all patients. Patients who had undergone previous sinus surgery were excluded. Furthermore, the maxillary sinuses had to be free from any local pathological conditions. The distance between the crest of the ridge and the floor of the sinus in the areas planned for future implant placement had to be less than 3 mm. All patients were informed of the risks and benefits of the procedure, and they gave their approval to participate and written consent ( Fig. 1 ).
Stock 0.1-mm thickness dynamic micro-titanium mesh (Leibinger, Stryker Co., Geneva, Switzerland) and stock 0.3-mm thickness resorbable mesh made of poly-dl-lactide (PDLLA) (Resorb-x; KLS Martin, Tuttlingen, Germany) were used in this study. Resorbable sonic pins, an ultrasound welder, and an Xcelsior water bath device were used for the sides treated with resorbable mesh (all from KLS Martin), and resorbable (lyophilized) collagen membranes (Biocollagen; Bioteck S.p.A., Torino, Italy) were utilized in all patients. Schilli Implantology Circle implants (SIC invent AG, Basel, Switzerland) were inserted in all patients; three types of implant drill were employed: classical, crestal, and tapping.
Preoperative preparation and radiographic examination
A thorough preoperative assessment of all patients was carried out, including history-taking and clinical and radiographic examinations. Cone beam computed tomography (CBCT) (SCANORA 3D with AutoSwitch; Soredex, Helsinki, Finland) with exposure parameters of 85 kVp, 15 mA, and 6 cm field of view (FOV) were performed while the patient was wearing a radiographic/surgical stent for standardized measurement. The implant surgical stent was fabricated using implant sleeves seated on the ridge of the cast in the planned implant positions.
First surgical stage
All patients were instructed to use povidone–iodine mouth rinse (Betadine) before the surgical procedures. All procedures were performed under maxillary nerve block anaesthesia with mepivacaine hydrochloride and 1:200,000 adrenaline solution (Scandonest 2%; Septodont, Saint-Maur-des-fossés, France). Bilateral maxillary sinus floor elevation using the lateral window technique was performed for each patient. A full-thickness mucoperiosteal trapezoidal flap was reflected to expose the lateral wall of the maxilla according to the implant treatment plan and fabricated surgical stent ( Fig. 2 ). A round diamond bur was used to outline both the inferior and superior horizontal osteotomies under copious water irrigation to carefully gain access to the Schneiderian membrane. The inferior osteotomy was approximately 3 mm from the sinus floor and the superior osteotomy was made 13–15 mm from the crest; these two osteotomies were connected by two vertical osteotomies. Once the window outline had been completed, special elevators (surgical sinus Freer elevators) were utilized to release the lateral bony window with the underlying Schneiderian membrane attached to it from the periphery of the osteotomy outline to gain a cleavage plane. It is imperative that the membrane is elevated across the sinus floor and up to the medial wall to the level of the proposed implant length ( Figs. 3 and 4 ). A foil template was trimmed to fit into the superior boundary of the sinus space created, reaching the medial wall of the sinus ( Fig. 5 ).