The posterior upper jaw — the maxillary molar and premolar region — is the area where implant dentistry most commonly encounters the limitation of insufficient bone. After tooth loss in this region, the maxillary sinus expands downward into the vacant space through a process called pneumatisation, while the alveolar bone resorbs from below. The result is a situation where there may be insufficient vertical bone height to safely place a standard-length implant. My research comparing crestal bone loss around implant prostheses with and without sinus augmentation, published in the Journal of Oral Implantology (2021), gives me a direct clinical perspective on how this procedure affects long-term outcomes. At Taki Dent, we approach sinus augmentation conservatively — it is performed when necessary, not as a default upsell.
Why the Posterior Maxilla Is Different
The maxillary sinus is an air-filled cavity within the cheekbone. Its floor lies in close proximity to the roots of the upper premolars and molars. After these teeth are lost, two processes work in tandem to reduce the bone available for implants:
Sinus pneumatisation
The sinus expands inferiorly once tooth roots are no longer present to limit it. This is a normal physiological process that begins within months of extraction and continues over years.
Crestal bone resorption
The alveolar ridge loses height and width following tooth extraction due to the loss of mechanical stimulation. In the maxilla, resorption is primarily centripetal — the ridge narrows and resorbs inward.
The combined effect over several years of tooth loss can be a residual bone height of 2–4 mm in the upper molar region — far below the 8–10 mm required for standard implants. This is the anatomical situation that necessitates sinus augmentation.
The Residual Bone Height Threshold
I use residual bone height (RBH) — measured in millimetres on CBCT — as the primary determinant of whether sinus augmentation is required:
| RBH on CBCT | Clinical Approach |
|---|---|
| > 10 mm | No augmentation needed — standard implant placement |
| 6–10 mm | Internal (transcrestal) sinus lift with simultaneous implant placement possible |
| 4–6 mm | Internal lift possible with experienced surgeon; external lift preferred by many clinicians |
| < 4 mm | External (lateral window) sinus lift with staged implant placement after 6–9 months healing |
These thresholds assume standard implant lengths of 8–10 mm. If short implants (4–6 mm) are planned, the requirements shift — see the section on alternatives below.
Internal vs External Sinus Lift: The Technical Difference
The two sinus augmentation techniques differ fundamentally in their surgical approach:
Internal (Transcrestal) Sinus Lift
Also called the osteotome or hydraulic technique. The sinus floor is elevated through the implant osteotomy — no separate lateral window is created. Bone graft material is condensed upward through the osteotomy site, raising the Schneiderian membrane (the mucosal lining of the sinus) before the implant is placed.
External (Lateral Window) Sinus Lift
A window is created in the lateral wall of the maxillary sinus. The Schneiderian membrane is carefully elevated from the sinus floor, and bone graft material is placed beneath it. The window is covered with a collagen membrane and the site heals over 6–9 months before implants are placed.
Alternatives to Sinus Augmentation
Sinus lifting is not the only solution for the atrophic posterior maxilla, and for some patients, alternatives are preferable:
- Short implants (4–6 mm): Modern short implants with wide diameters and optimised surface treatments achieve survival rates comparable to standard implants when bone quality is adequate. They avoid sinus augmentation entirely in patients with 5–7 mm RBH.
- Tilted implant designs: In the All-on-4 and All-on-6 context, angled posterior implants can be placed entirely anterior to the sinus floor, avoiding the sinus altogether while still supporting a full-arch prosthesis.
- Zygomatic implants: For severely resorbed maxillae where even external sinus lifting is insufficient, zygomatic implants engage the zygomatic bone rather than the maxillary alveolus. These are specialist procedures with excellent outcomes in appropriate cases.
- Pterygoid implants: Implants engaging the pterygoid process of the sphenoid bone posteriorly, avoiding the sinus entirely. Technically demanding but highly effective in the right anatomy.
What Patients Should Expect from the Procedure
An internal sinus lift combined with implant placement is typically performed under local anaesthesia in approximately 60–90 minutes per side. Post-operative instructions include avoiding nose blowing, sneezing through the nose, or any activity that increases sinus pressure for the first two weeks. Swelling and bruising in the cheek area is expected for 5–7 days.
A lateral window sinus lift is a more extensive procedure, typically taking 90–120 minutes per side. Post-operative swelling is more pronounced and may persist for 10–14 days. Patients should plan to remain in Antalya for a minimum of 3–5 days following the procedure to allow for our post-operative review appointment before travelling home.
My published comparison of crestal bone loss between implants with and without sinus augmentation confirmed that when the procedure is executed correctly, augmented sites achieve bone levels equivalent to native bone sites over a 2-year follow-up period. The augmentation, in other words, does not create a long-term disadvantage — it creates a foundation equivalent to the bone that was never lost.