Sinus lift

Maxillary sinus floor augmentation^[1] (also known as a sinus lift, sinus graft, sinus augmentation, or sinus procedure) is a surgical procedure used to increase the amount of bone in the upper back part of the jaw (posterior maxilla) by lifting the lower Schneiderian membrane and placing a bone graft.^[2]

X-ray showing a sinus lift in the left upper jaw

Sinus lift surgery, 3D Illustration

Indications

While there are many reasons to undergo a sinus lift, the most common reason for the surgery is to provide sufficient bone under the maxillary sinus for dental implants.^[3]

A sinus lift is typically required for dental implants because the medial wall is too close to the area where they are to be placed. This procedure is performed to ensure a secure place for the implants while protecting the sinus. Lowering of the sinus may result from long-term tooth loss without treatment, periodontal disease, or trauma to the tooth.^[4]

Patients with one or more of the following conditions may be candidates for sinus augmentation:^[5][6]

• Loss of more than one tooth in the posterior maxilla
• Loss of a significant amount of bone in the posterior maxilla
• Missing teeth due to genetics or birth defects
• Missing most maxillary teeth and requiring a strong sinus floor for multiple implants.

It remains unknown whether sinus lift techniques are more successful than short implants in reducing the number of artificial teeth or dental implant failures up to one year after their placement.^[7]

Technique

1) Edentulous area of two missing teeth is being prepared for future placement of dental implants with a lateral window sinus lift; incisions into the soft tissue are shown here.
2) The soft tissue is flapped back to expose the underlying lateral wall of the left maxillary sinus.
3) The bone has been removed with a piezoelectric instrument, exposing the underlying Schneiderian membrane, which is the lining of the maxillary sinus cavity.
4) Through careful instrumentation, the membrane is peeled from the inner aspect of the sinus cavity.
5) The membrane has been reflected from the internal aspect of the inferior portion of the sinus cavity; one can now visualize the bony floor of the sinus cavity without its lining membrane (note the triangular ridge of bone within the sinus, known as an Underwood's septum).
6) The newly formed space within the bony cavity of the sinus yet inferior to the intact membrane is grafted with human cadaver allograft bone. The floor of the sinus will now be roughly 10mm or larger than before, providing enough room to place dental implants into the edentulous site.

Before undergoing sinus augmentation, diagnostics determine the health of the patient's sinuses. Panoramic radiographs are taken to map out the patient's upper jaw and sinuses. In special instances, cone beam computed tomography is preferable in measuring sinus height and width, ruling out any sinus disease or pathology.^[8]

There are several variations of the sinus lift technique, including the traditional sinus augmentation and the osteotome technique.

Traditional sinus augmentation or lateral window technique

The procedure is performed intraorally, where the surgeon makes an incision into the gum. Once the incision is made, the surgeon then pulls back the gum tissue, exposing the lateral bony wall of the sinus. The surgeon then creates a "window" into the sinus, exposing the Schneiderian membrane. The membrane is separated from the bone, and bone graft material is placed into the newly created space. The gums are then sutured closed, and the graft is left to heal for 4 to 12 months.^[9]

The graft material can be either an autograft, allograft, xenograft, alloplast, synthetic variant, or a combination of both.^[10] Studies indicate that the lifting of the sinus membrane might result in new bone formation due to the principles of guided bone regeneration.^[11] The long-term prognosis for the technique is estimated at 94%.^[12]

Osteotome technique

As an alternative, sinus augmentation can be performed by a less invasive osteotome technique. There are several variations of this technique, all originating from a technique pioneered by Dr. Hilt Tatum, first published by Boyne and James in 1980.^[13]

Dr. Robert B. Summers^[14] described a technique that is normally performed when the sinus floor needing to be lifted is less than 4mm thick. This technique, performed by flapping back gum tissue, made a socket in the bone 1–2mm short of the sinus membrane. The floor of the sinus is then lifted by tapping the sinus floor with the use of osteotomes. The amount of augmentation achieved with the osteotome technique is usually less than what can be achieved with the lateral window technique.

A dental implant is placed in the socket formed at the time of the sinus lift procedure and left to integrate with the bone. Bone integration usually takes 4 to 8 months. The goal of this procedure is to stimulate bone growth and form a thicker sinus floor to support dental implants for tooth replacement.^[15]

The dimensions and shape of the maxillary sinus significantly influence new bone formation following transcrestal sinus floor elevation. With this technique, substantial new bone regeneration is a predictable outcome primarily in narrow sinus cavities. Therefore, sinus width should be considered a critical parameter during surgical planning when selecting the appropriate sinus floor elevation approach.^[16]

Dr. Bruschi and Scipioni^[17][18] described a technique known as Localized Management of Sinus Floor (LMSF), which is based on a partial thickness flap procedure. This technique improves the crestal bone malleability by utilizing the medial wall bone, rather than the bone directly below the sinus, allowing its application in extreme cases of bone resorption that would normally require treatment with the lateral wall technique. The healing period is reduced to 1.5 to 3 months. Around 2014, an electrical mallet^[19] has been introduced to simplify the application of this and similar techniques.

Complications

One of the primary risks of sinus augmentation is perforation or tearing of the sinus membrane. This can often be remedied by suturing the tear or applying a protective patch. In certain cases, the surgery may be halted to allow the membrane to heal naturally, typically over 3 to 6 months. The regenerated membrane often becomes thicker and more resilient, improving the chances of success in a subsequent procedure. ^[20] Although rarely reported, such secondary intervention can also be successful when the primary surgery is limited to the elevation of the membrane without the insertion of additional material.^[21]

Besides tearing of the sinus membrane, there are other risks involved in sinus augmentation surgery. Most notably, the close relationship between the augmentation site and the sinonasal complex can induce sinusitis, which may become chronic and cause severe symptoms. According to Felisati's classification, sinusitis resulting from maxillary sinus augmentation is considered a Class 1 sinonasal complication and should be addressed surgically utilizing a combined endoscopic endonasal and transoral approach.^[22] Besides sinusitis, other procedure-related risks include:

• Infection^[7]
• Inflammation
• Pain
• Itching
• Allergic reaction
• Tissue or nerve damage^[7]
• Scar formation
• Hematoma
• Graft failure
• Tilting or loosening of implants
• Bleeding^[7]

Recovery

It generally takes three to six months for the sinus augmentation bone to integrate with the patient's natural sinus bone. Up to six months of healing is sometimes required before implants are attempted. However, to avoid performing two different surgeries, some surgeons perform both the augmentation and dental implant simultaneously.^[23][24]

History

A sinus-lift procedure was first performed by Dr. Hilt Tatum in 1974 during his period of preparation to begin sinus grafting. In February 1975, the first sinus graft was performed by Tatum in Lee County Hospital in Opelika, Alabama. This was followed by the placement and successful restoration of two implants. Between 1975 and 1979, much of the sinus lining elevation was conducted utilizing inflatable catheters. Afterwards, the development of suitable instruments enabled the management of the lining elevation from the different anatomical surfaces encountered in the sinuses. ^[25]

In 1976, Tatum first presented the concept at the Alabama Implant Congress in Birmingham and demonstrated the technique's evolution during multiple presentations each year until 1986, when he published an article describing the procedure. In 1977 and 1978, Tatum introduced the process to Dr. Philip Boyne when he invited him to be "The Discusser" of a presentation on sinus grafting given by Tatum at the annual meeting of the American Academy of Implant Dentistry. In 1980, Boyne and James authored the first publication on the technique. They published case reports of autogenous grafts placed into the sinus and allowed to heal for 6 months, which was followed by the placement of blade implants. ^[26] In 1994, this sequence was confirmed by Boyne at the Alabama Implant Congress.^{[citation needed]}

Cost-effectiveness

The slightly higher effectiveness of the lateral sinus-lift technique should be considered, given the higher costs compared to the transalveolar sinus lift technique. From a patient perspective, the lateral technique's higher invasiveness is another important decision criterion. However, the effectiveness of the transalveolar approach is unlikely in cases of advanced levels of bone reduction at the implant site.^[27]