Maxillary Sinus Lift: Open and Closed Techniques, Graft Materials and Clinical Indications

Elevation of the maxillary sinus floor — introduced by Tatum in 1977 and formalized by Boyne and James in 1980 — has become the most widely performed pre-implant surgical procedure in implantology. Vertical bone loss in the posterior maxilla, resulting from edentulism and progressive sinus pneumatization, is a universal phenomenon affecting most edentulous adult patients in this area. Residual vertical bone availability is the main discriminating parameter in technique choice: with residual bone heights (ROH) above 5-6 mm, the osteotome technique (OSFE, Osteotome Sinus Floor Elevation) is generally preferred, while with ROH below 4-5 mm, the lateral technique (LSFE) is indicated, allowing larger graft volumes and direct site visualization.

The classic lateral technique (modified Caldwell-Luc) involves creating a bony window on the lateral sinus wall, elevating the Schneiderian membrane, and filling the created space with graft material. The sinus membrane — with a physiological thickness of 0.3-0.8 mm and wide individual variability — is the anatomical layer that determines the procedure's technical difficulty. Membrane thickness below 1.5 mm is associated with a higher perforation risk according to Janner et al. (2011). Perforations, classified by Testori (2012) into Class I (<5 mm, with spontaneous repair), Class II (5-10 mm, manageable with resorbable collagen membranes), and Class III (>10 mm, requiring procedure suspension), occur with a frequency of 19-58% across different case series — a wide range reflecting the importance of operator experience and preoperative sinus morphology.

Graft material choice is governed by four main characteristics: osteogenicity (the ability to produce de novo bone through stem cells within the graft itself), osteoinduction (the ability to stimulate osteoblastic differentiation of surrounding cells, mediated by BMP and other morphogens), osteoconduction (scaffolding properties for vascular and cellular growth), and resorption rate. The patient's own autologous bone remains the material with the most complete properties (osteogenic, osteoinductive and osteoconductive), with predictable resorption. Intraoral harvest sites (mandibular ramus, chin symphysis, coronoid process) provide variable amounts of cortical/cancellous bone, with acceptable morbidity but an additional surgical site. Bovine xenogenic bone substitutes (Bio-Oss®, Endobon®) made of deproteinized hydroxyapatite are the most documented alloplastic materials in the literature, with over 600 published RCTs and prospective studies. They maintain volumetric space long-term thanks to slow resorption, and their apatite crystals integrate into the newly formed bone matrix in a way histologically indistinguishable from native bone after 6-9 months.

Healing times before implant placement vary based on graft material and volume. With pure autologous bone or a 1:1 autologous/xenogenic mix, implant re-entry traditionally happens at 4-6 months; with pure xenogenic material, at 6-9 months. The simultaneous implant placement approach — possible when ROH ≥4-5 mm ensures adequate primary stability — reduces the number of sessions and the extent of atrophy during the waiting period. Implant survival rates in the augmented sinus — reported by Aghaloo and Moy's meta-analysis (J Oral Maxillofac Surg, 2016) on 3,246 implants — are 91.8% with the lateral technique (range 61.7-100%) and 92.8% with the osteotome technique (range 81.8-100%) at 3-5 years, comparable to values in native bone sites without grafting.

The osteotome technique — introduced by Summers in 1994 — leverages the malleability of posterior maxillary cancellous bone to laterally condense residual bone tissue and create space for the graft without lateral access. It's performed progressively, with sequential insertion of increasing-diameter osteotomes at the implant site, up to elevating the sinus floor by 2-4 mm. The main limitations are the amount of volume gainable (generally 1-4 mm vs. 10-15 mm with the lateral technique) and the risk of post-procedure BPPV (Benign Paroxysmal Positional Vertigo), reported with an incidence of 0.6-3% across case series, linked to transmission of percussive impulses to the inner ear through the skull base. Prevention requires appropriately dampened osteotome taps and preoperative assessment of vestibular history.

Contraindications to sinus surgery — beyond the general systemic conditions contraindicating implant surgery — include untreated chronic sinusitis, a surgically operated sinus with scarring and adhesions, sinus cysts larger than 20 mm occupying the floor (to be assessed case by case in collaboration with the rhinologist), heavy smoking (>20 cigarettes/day), which increases graft failure risk by 300% compared to non-smokers (Moraschini et al. meta-analysis, 2020), and prior head-and-neck radiotherapy at a dose >50 Gy. Preoperative CBCT assessment is mandatory to characterize the Underwood septum (present in 32-44% of sinuses, which may require multiple windows or adapted osteotomes), sinus floor morphology, and intraosseous vascularization of the lateral wall.