Sinus floor elevation: 1-stage window
Introduction
When a sinus floor augmentation is required (e.g., in cases of insufficient residual bone height, low bone density, or a wide sinus in bucco-palatal width), a lateral window approach is recommended (Valentini et al. 2025).
When this procedure is performed in combination with implant placement (1-stage), the implant(s) can act as tent pillars to support the sinus membrane, and L-PRF can be used as a "sole" graft material.
However, if the implant's primary stability is not predictable (e.g., due to weak bone or insufficient bone height), the augmentation should be conducted first, followed by implant placement after the graft has healed (2-stage). In the case of a 2-stage approach, the sinus must be grafted with a stronger "bone substitute" (eventually in combination with L-PRF), as the L-PRF membranes "alone" are too weak to resist sinus pneumatization.
Protocol: step by step
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make a crestal incision and reflect a mucoperiosteal flap to expose the buccal bone for a clear view,
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prepare a lateral window to the sinus (piezotome/diamond bur),
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carefully elevate the sinus membrane; if possible, push the bony window inside to act as the new floor of the sinus over the implant apex,
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apply a double layer of L-PRF membranes over the inwardly rotated bony window and the elevated sinus membrane,
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prepare the implant(s) osteotomy,
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apply several L-PRF membranes in the uncovered sinus area, especially against the anterior and palatal sinus wall,
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insert the implant(s); the double layer of L-PRF membranes prevents sinus membrane perforation while inserting the implant(s) and patches any membrane tears,
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apply additional L-PRF membranes in the newly created space (due to the implant rotation) and in the window area,
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seal the window area with a double layer of L-PRF membranes,
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suture to obtain primary closure,
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plan for abutment connection after 4-6 months.
step-by-step flow chart
Video: 1-stage sinus floor elevation (window approach, L-PRF only & implant)
Prepare a lateral window; either use the bony window to cover the entrance to the sinus at the end of the surgery, or push it inside to serve as a new floor for the sinus. The latter supports the formation of bone over the implant apex but increases the risk for a sinus membrane perforation. Meticulously elevate the Schneiderian membrane and prepare the osteotomy (eventually protect the sinus membrane with L-PRF membranes). Fill the created space with L-PRF membranes, and insert the implant. Add additional membranes around the implant and fill the window with L-PRF membranes. Seal the entrance to the sinus with another L-PRF membrane.
Cases
(d = day, w = week, m = month, y = year)
1: 1-stage lateral window sinus floor elevation: L-PRF only & implant
d 0: a double layer of L-PRF membranes protects the sinus membranes, and 3-5 additional L-PRF membranes are added after the preparation of the osteotomy.
d 0: the implant is inserted; due to its rotation, extra space becomes available, which requires the addition of extra L-PRF membranes.
d 0: view after adding extra membranes after implant insertion into the sinus and in the window area.
d 0: the entrance to the sinus is sealed with L-PRF membranes.
d 0: post-op CBCT (sagittal image) showing implant for 6 mm into the sinus (red line is initial floor of sinus).
d 0: post-op CBCT (bucco-palatal cut); the location of the window is visible, and the compact filling with L-PRF is less visible.
m 5: intra-oral RX (red = initial floor, white = new floor of sinus).
y 6: intra-oral RX (red = initial floor, white = new floor of sinus).
d 0: for comparison: intra-oral RX at day of tooth extraction (red = initial floor of the sinus).
2: 1-stage lateral window sinus floor elevation: L-PRF only & implant
d 0: sagittal CBCT image with the implant ± 5 mm into the with L-PRF augmented sinus area.
d 0: cross-sectional CBCT cut
(B-P direction) showing the fractured part of the sinus floor (white spot).
m 4: sagittal CBCT image highlighting the increase in bone height.
m 4: sagittal CBCT image (white = new floor of sinus).
intra-oral RX showing the bone regeneration after 1 y of implant loading.
Data:
Clinical trials with L-PRF as "sole" substitute during 1-stage sinus floor elevation
Abbreviations: CCT = controlled clinical trial, CS = case series, RCT = randomized controlled trial, RBH = residual bone height, Substitute: L-PRF = leucocyte- and platelet-rich fibrin, A-PRF = advanced platelet rich fibrin, CGF = concentrated growth factor, cl = clot, m = membrane (s = sinus); Outcome: VBG = vertical bone gain.
Conclusion
Ten papers reported data on vertical bone gain (VBG) during a 1-stage lateral window sinus floor elevation only applying L-PRF as "sole" graft, with an overall mean gain of 6.8 mm (SD 2.4), ranging from 3.5 to 10.4 mm. This gain was frequently in continuity with the implant apices. The residual bone height (RBH) on the day of sinus floor elevation did not appear to influence the outcome of the procedure. This was confirmed by two studies involving patients with an average RBH of 1.8 mm (Simonpieri et al. 2011) or a minimum of 1.0 mm (Merli et al. 2022), respectively.
One CCT (Merli et al. 2022) and one RCT (Dominiak et al. 2021) compared the use of L-PRF alone with a standard bone substitute. Both studies reported a slightly lower VBG when L-PRF was used, with differences ranging from 0.6 to 1.0 mm. The overall implant survival rate was 99.4% (ranging from 94.1% to 100%). Updated from Valentini et al. 2025.
Decision tree: 1 or 2-stage sinus floor elevation: see sinus floor elevation "2-stage"
(Miron & Pikos 2018, Valentini et al. 2025)
Important notice
Clinical experience:
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More bone gain will be obtained when using the bony window as the new floor of the sinus, covering the apex of the implants.
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Protect the sinus membrane with a double layer of L-PRF membranes before preparing the implant osteotomy.
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Apply ≥ 3 L-PRF plugs/membranes to fill the uncovered sinus area (1 per required mm bone gain).
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Make sure to place some of these membranes at the palatal and anterior sinus sites.
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Add extra L-PRF membranes after implant insertion.
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Membranes are superior to clots.
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Fill the window with L-PRF membranes, and cover the entrance to the sinus with a double layer of L-PRF membranes.
Additional Benefits:
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This is a 100% autogenous therapy, without foreign bodies.
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When applying L-PRF as a sole graft, an improved bone quality is obtained without “remaining" bone substitute.
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In case of a perforation of the sinus membrane, only autogenous material will reach the sinus.
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The treatment will become easier and less expensive.
Be aware:
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In case of minor sinus membrane perforations, the L-PRF membranes will facilitate the healing.
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The choice for a 1- or 2-stage window technique depends on several criteria (see the decision tree on the webpage "sinus floor elevation: 2-stage").
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The prevention and management of intraoperative complications during maxillary sinus augmentation are nicely explained in the following 2 papers (Valentini & Artzi 2023, Valentini & Stacchi 2025).
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Check for possible arteries (intra-osseous branch of superior posterior alveolar artery) running in the lateral sinus wall) analyzing CBCT images (Tofangchiha et al. 2022).
After careful erosion of the bony window, the artery (visible on the cross-sections of the CBCT (yellow arrows) could be dissected.
Courtesy:Alexandre Sarfati
Interesting references
Several videos and/or cases on this webpage are discussed more in detail in the following book: Quirynen M & Pinto N 2022. Leukocyte- and Platelet-Rich Fibrin in Oral Regenerative Procedures. Quintessence Publishing;
ISBN: 978-1-78698-105-9