Crestal Approach Sinus Floor Elevation at Tooth #3 — Step-by-Step
Introduction
Tooth loss in the posterior maxilla is frequently followed by alveolar resorption and sinus pneumatization, leaving insufficient subantral bone for standard-length implants. Transcrestal sinus floor elevation (TSFE), first described by Tatum and modified by Summers, restores subantral height through the implant osteotomy itself, avoiding a lateral bony window and its associated morbidity. This case documents a single-site crestal approach at the maxillary right first molar (#3) with simultaneous implant placement.
Step 1 — Diagnosis and 3D planning (Image: preoperative CBCT cross-section)
A cone-beam CT cross-section at #3 was obtained to measure residual bone height (RBH), bucco-palatal sinus width, and to rule out sinus pathology and septa. Case selection is critical: the crestal approach is best indicated for a single site with adequate ridge width and RBH generally ≥5 mm, where the planned elevation does not exceed ~3–4 mm. Narrow sinuses (bucco-palatal width ≤12 mm) are more predictable and carry lower perforation risk than wide sinuses. An intact Schneiderian membrane and a relatively flat sinus floor without septa were confirmed as prerequisites for a predictable "blind" elevation.
Step 2 — Flapless linear-incision access
The procedure was performed flapless. Under local anesthesia, a linear crestal incision was made over the #3 site and gently opened; the access was enlarged to expose the alveolar crest sufficiently for direct visualization of the osteotomy entry point, without raising a full mucoperiosteal flap and without a tissue punch. This minimally invasive access preserves the periosteal blood supply and soft-tissue architecture while still allowing controlled instrumentation. Osteotomy preparation then followed the standard drilling protocol and was advanced to within approximately 1–2 mm of the sinus floor, as measured on CBCT, preserving a thin shelf of cortical floor beneath the intact membrane.
Step 3 — Controlled fracture of the sinus floor
The residual floor was in-fractured atraumatically. Depending on operator preference, this is achieved with sequential osteotomes of increasing diameter producing a green-stick fracture, or with dedicated protective/atraumatic drills or piezoelectric inserts designed to reduce perforation risk. Osteotome condensation additionally increases the density of the soft posterior maxillary bone, enhancing primary implant stability.
Step 4 — Membrane elevation and integrity check
The Schneiderian membrane was gently detached and displaced cranially. Because access is indirect, membrane elevation is performed hydraulically (saline), with an injectable/granular biomaterial, or via osteotome pressure, and membrane integrity is verified through the osteotomy and with a Valsalva maneuver. A depth gauge was used to confirm adequate subantral space and assess membrane tension. Membrane perforation is the most common intraoperative complication (reported up to ~7% in low-RBH series and higher in wide sinuses); a significant tear would prompt conversion to a lateral window approach.
Step 5 — Grafting the subantral space (Image: periapical radiograph showing the apical dome)
A deproteinized bovine bone mineral graft (particle size 0.25–1 mm) was incrementally introduced through the osteotomy to elevate and support the membrane, creating the characteristic radiopaque apical dome seen on the periapical film. Grafting supports the elevated membrane and maintains subantral space, though evidence indicates that the secluded blood-filled chamber beneath an intact membrane can also support new bone formation with or without added filler.
Step 6 — Simultaneous implant placement (Images: periapical and CBCT/periapical series)
The implant was placed simultaneously, achieving adequate primary stability from the residual crestal bone and the condensed osteotomy walls; the implant apex projects into the grafted dome, consistent with the follow-up radiographs demonstrating graft consolidation circumferentially around the implant apex. Simultaneous placement is standard when primary stability is sufficient and is associated with more stable postoperative height.
Step 7 — Closure, prosthetic context, and follow-up (Images: occlusal clinical view; pre/post panoramic radiographs)
The linear incision was closed with tension-free suturing, and a baseline radiograph was obtained for future comparison. The occlusal view documents the restored maxillary arch and the prosthetic environment of the #3 site, and the pre/post panoramic pair illustrates the augmented subantral bone supporting the integrated implant. Timing of loading and abutment connection is individualized according to residual bone volume, bone quality, and primary stability.
Discussion / Outcomes
The crestal approach offers reduced surgical trauma, less postoperative morbidity, shorter healing, and completion of augmentation and implant placement in a single visit compared with the lateral window. A flapless linear-incision access further limits soft-tissue trauma while maintaining direct access to the osteotomy site. Reported implant survival with the osteotome technique is approximately 95.8% at 5 years, with higher survival above 5 mm RBH (96.9%) than below (92.7%). The principal limitations are the indirect ("blind") nature of membrane elevation and a finite achievable elevation; meticulous technique and preservation of an intact membrane remain the key determinants of a predictable outcome.
