A Less-Invasive Window Design for Lateral Wall Maxillary Sinus Augmentation for Single Implants

The maxillary sinus augmentation procedure has been documented to be a predictable technique for restoring bone in severely resorbed posterior edentulous maxillary arches.^1-4 The procedure has been used to increase bone height to achieve the level required for successful endosseous dental implant placement in the posterior maxillary area. The lateral window technique has shown to be a predictable method to access the sinus for bone augmentation in an atrophic posterior maxilla.^1-4

When performing a sinus augmentation, maxillary sinus window design is an important factor for preventing and managing maxillary sinus elevation complications, such as sinus membrane perforations and bleeding, and providing lateral support for the graft material. Initially, this design was based on making the aperture of the window as large as possible, starting approximately 3 mm to 4 mm coronal to the floor of the sinus and extending vertically, to the level of the desired height of the implants planned for placement.⁵ The lateral window was designed to provide maximum accessibility to the sinus.

More recently, a less-invasive window design (LIWD) was introduced that varies depending on the number of implants (single or multiple) planned for placement in the augmented sinus.⁶ In addition to window size, differences between larger conventional maxillary sinus windows and smaller LIWD windows include the fact that the latter enables preservation of the lateral sinus walls and provides improved blood supply to bone graft material. The LIWD window design also offers better containment of the graft material, enhanced visibility, better accessibility for repairing membrane perforations, and the ability to drain sinus infections if needed.

The LIWD for single implants is designed to be a vertically oriented 4 mm to 8 mm ovate, or "I"-shaped, window. After the initial window is created, the sinus membrane is elevated at the apical border of the window and extended by elevating around the borders. A high-speed handpiece with copious irrigation and a fine, long-shank, round diamond bur (size #6 or #8) is used to extend the window coronally, starting 2 mm apical to the sinus floor. For single implants, minimal extension of the mesial and distal borders of the window helps support the bone graft and protect the roots of the adjacent teeth. Any necessary apical and coronal extension of the lateral window allows for additional accessibility and visibility of the sinus elevation. One disadvantage of this window design, though, is the difficulty it poses in allowing access to the anterior area due to the limited space for instrumentation.

A modification of the LIWD window is aimed at improving accessibility to the anterior area of the sinus. The purpose of this case report is to demonstrate the step-by-step surgical procedure for lateral wall maxillary sinus augmentation using this modified "J"-shaped design for single implant placement.

A 29-year-old male patient presented to the Ashman Department of Periodontology and Implant Dentistry at New York University College of Dentistry for replacement of the maxillary right second premolar tooth (Figure 1 and Figure 2). He reported that the premolar had been extracted in 2020 due to endodontic failure. Treatment options were presented, and the patient opted for implant placement. Benefits and risks were discussed extensively with the patient, and informed consent for was obtained.

The patient reported that his medical history included having Crohn's diseaseand taking Stelara^®, 90 mg every 8 weeks.

A periapical radiograph was taken, which did not reveal any pathology in the maxillary right premolar area (Figure 3). A presurgical cone-beam computed tomography (CBCT) scan confirmed adequate bone width with decreased bone height due to the sinus proximity (Figure 4). Prior to the surgery, the patient received full-mouth scaling and root planing and was instructed in proper oral hygiene care.

On the day of the surgery, the area was locally anaesthetized with 2% lidocaine hydrochloride with epinephrine 1:100,000 (Henry Schein Dental, henryschein.com). A full-thickness flap was performed with crestal and vertical incisions distal to the maxillary right first molar and mesial to the maxillary right first premolar. The flap was reflected apically to expose a portion of the lateral bony wall of the maxillary sinus (Figure 5). A LIWD window for a single implant was planned as a vertically oriented 4 mm to 8 mm ovate window.

After the initial "I"-shaped window was created, a small perforation of the Schneiderian membrane was observed (Figure 6). The sinus membrane was elevated at the apical border of the window and extended by elevating around the borders. A high-speed handpiece with copious irrigation and a fine, long-shank, round diamond bur (size #8) was used to extend the window coronally to the level of the sinus floor. The window was then extended mesially to create a "J"-shaped window and allow additional access to the anterior wall of the sinus (Figure 7). The perforation was then repaired during the surgery with an absorbable collagen membrane (CollaTape^®, Integra LifeSciences Corp., integralife.com) positioned between the lateral wall of the sinus and the perforated Schneiderian membrane after extension of the bony window. The sinus membrane was elevated using sinus elevators (Sinus Lateral Lift Kit, Zimmer Biomet, zimmerbiomet.com).

The membrane was again evaluated for perforation by direct vision and via the Valsalva technique. Neither assessment indicated further perforation. The sinus membrane was kept elevated while the implant osteotomy was prepared using a surgical guide. The residual space between the sinus membrane and the maxillary sinus floor was grafted with a xenograft (large-particle, cancellous Bio-Oss^®, Geistlich, geistlich-pharma.com) (Figure 8). A 4.1 mm x 12 mm bone-level implant (SLActive^® Roxolid^®, Straumann, straumannn.com) was placed using a submerged approach (Figure 9 and Figure 10). Using the sinus cortical bone to increase initial stability, a torque value of 35 Ncm was achieved. Primary closure of the flap was attained with absorbable sutures (4-0 Chromic Gut, Henry Schein Dental) (Figure 11 and Figure 12). A postsurgical radiograph showed the implant in a proper position following the sinus grafting (Figure 13).

The patient was prescribed 500 mg amoxicillin for 1 week, 600 mg ibuprofen as needed for 5 days, and chlorhexidine digluconate 0.12% for 2 weeks. He was instructed to avoid excessive activity during the first few postoperative days and to refrain from rinsing his mouth or expectorating, except when required by the prescribed medications. The patient was also told to avoid maneuvers that could increase pressure in the maxillary sinus, such as blowing his nose or sneezing. (If the urge to sneeze occurred, the patient was instructed to do so with his mouth open.) In addition, the patient was placed on a soft diet (warm or cold) for at least 1 week.

The patient returned 2 weeks later for a follow-up visit; healing had proceeded within normal limits, with no signs of complications (Figure 14). After 3 months of undisturbed healing, second-stage surgery was performed. Two weeks later, a pick-up impression was produced. The fully seated, fixture-level impression coping was confirmed with a radiograph. One month later, a definitive screw-retained crown was delivered. The patient was seen 3 months, 6 months, and 1 year after restoration. At 1 year, the implant and prosthesis were functioning well, with no marginal bone loss around the implant (Figure 15).

The patient was regularly followed for the 6-month healing period. He did not suffer from any sinus infection or abnormal postoperative bleeding. After 18 months of functioning, the patient reported no discomfort.

It had been widely assumed that a large lateral window design was advantageous for preventing and managing complications during and following a sinus augmentation procedure due to improved visibility and accessibility to the membrane-perforated area and sinus cavity. The "J"-shaped window design described in this article, however, is less invasive compared to the conventional lateral window design and still provides accessibility to properly elevate the sinus membrane. Also, the window can be modified and enlarged for additional accessibility in cases of managing inter- or postoperative complications.

Adequate elevation of the sinus membrane creates the necessary space for the bone to regenerate and allows dental implant placement in a more-ideal position. The previously reported "I"-shaped LIWD offers support and stability for the bone graft inside the maxillary sinus and provides a source of bone cells to surround the bone graft particles, thereby improving the amount of regenerated vital bone formed.⁶ The window design, however, allows limited accessibility of instrumentation to the anterior area and achieves incomplete membrane elevation. The modified LIWD described in this report utilizes a "J"-shaped window design that enables better accessibility to the anterior border of the sinus. This improves membrane elevation for enhanced grafting.

Sinus membrane perforations have been reported to be the most common complication of the sinus elevation procedure.^7,8 The literature reports a 10% to 50% prevalence of membrane perforation.^9,10 Sinus membrane perforation is assumed to be a detrimental factor for graft and implant survival rate and can also lead to infection, edema, sinus pathology, wound dehiscence, and procedure failure. Small perforations of the Schneiderian membrane can be repaired with a collagen membrane, and the augmentation procedure can then be completed.¹¹ In the present case, a collagen membrane was placed over the perforated site, and elevation, grafting, and implant placement were then performed.

As compared to conventional lateral window design, advantages of the "J"-shaped window design described in this article are better visibility, good accessibility regarding anatomical obstacles, improved blood supply to bone grafts, and enhanced containment of the graft material. Within the limitations of this case report, the technique presented appears to be a simple and reliable alternative to LIWD. Although these results are promising, further studies are required to validate this single case report.

Peerapol Tevavichulada, DDS
Resident, Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York

Inès Zouari, DDS
Resident, Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York

Mitsuhiro Sawada, DDS
Resident, Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York

Stuart J. Froum, DDS
Clinical Adjunct Professor and Director of Clinical Research, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York; Private Practice; New York, New York

Sang-Choon Cho, DDS
Clinical Associate Professor and Director of Advanced Program for International Dentists in Implant Dentistry, Ashman Department of Periodontology and Implant Dentistry, New York University College of Dentistry, New York, New York