Maxillary Sinus Tenting and Implant Placement

 Maxillary Sinus Tenting and Implant Placement

"Sinus lifting"

When a tooth is lost the alveolar process begins to remodel. The vacant tooth socket collapses as it heals leaving an edentulous (toothless) area, termed a ridge. This collapse causes a loss in both height and width of the surrounding bone. In addition, when a maxillary molar or premolar is lost, the maxillary sinus pneumatizes in this region which further diminishes the thickness of the underlying bone. Overall, this leads to a loss in volume of bone that is available for implantation of dental implants, which rely on osseointegration (bone integration), to replace missing teeth. The goal of the sinus lift is to graft extra bone into the maxillary sinus, so more bone is available to support a dental implant.

The bone quality or quantity of the patient may not be conducive to support a proper dental implant. Thus, a secondary surgical procedure is used to augment the bone so that the implant can be ideally positioned and stabilized. 

Dental implants have become a well-accepted mode of treatment to our patients. They present with missing teeth and request permanent replacement with fixed prostheses. The success of our modern dental implants is reliant on their ability to integrate into the bone. This requires a relatively healthy patient with no uncontrolled healing properties and adequate hard-tissue availability. Initial stability is paramount. Bone grafting procedures are well established in the profession. They involve adding a bone substitute into a deficient site to create volume and density. A common material used today is referred to as an allograft, which is graft material harvested and processed from another human.

Sinus tenting procedures can seem daunting to the general practitioner. As teeth are lost, we see physiologic shrinkage both palatally and vertically. The subsequent socket can lose 40% to 60% of bone structure in the first 3 years following extraction. The maxillary posterior region is further complicated by the fact that when teeth in the sinus area are removed, the sinus floor will fall, enlarging the sinus cavity. There is often not enough vertical height of hard tissue to predictably place a dental implant to help restore the site with an implant-retained crown. Sinus tenting, in some situations, can be a simple surgical procedure that lifts the maxillary sinus membrane upward to make some room for additional bone. This sinus augmentation provides increased availability of hard tissue to accept a dental implant. The maxillary sinus can be divided into compartments separated by septae. This must be evaluated thoroughly prior to any surgical intervention. It has been demonstrated in the literature that the newly formed bone around a grafted dental implant resembles native bone over time .

Indication of sinus lifting procedure :

1) Lost more than one tooth in the posterior maxilla.

2) Lost a significant amount of bone in the posterior maxilla.

3) Missing teeth due to genetics or birth defect.

4) Minus most of the maxillary teeth and need a strong sinus floor for multiple implants.

It is not known if using sinus lift techniques is more successful than using short implants for reducing the number of artificial teeth or dental implant failures up to a year after teeth/implant placement

Short Implants (5 to 8 mm) Versus Longer Implants (>8 mm) with Sinus Lifting in Atrophic Posterior Maxilla

The systematic review of some studies showed that no difference between the survival rates of short implants (5–8 mm) and long implants (>8 mm) 

Techniques :

Traditional Sinus Augmentation or Lateral Window Technique

There are multiple ways to perform sinus augmentation. The procedure is performed from inside the patient's mouth where the surgeon makes an incision into the gum, or gingiva. Once the incision is made, the surgeon then pulls back the gum tissue, exposing the lateral bony wall of the sinus. The surgeon then cuts a "window" to the sinus, which is 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 close and the graft is left to heal for 4–12 months.

The graft material used can be either an autograft, an allograft, a xenograft, an alloplast (a growth-factor infused collagen matrix), synthetic variants, or combinations .

Studies indicate that the mere lifting of the sinus membrane, creation of a void space and blood clot formation might result in new bone owing to the principles of guided bone regeneration.

The long-term prognosis for the technique is estimated to 94%.

Osteotome Technique

This technique  is normally performed when the sinus floor that needs to be lifted is less than 4 mm. The technique is performed by flapping back gum tissue and making a socket in the bone within 1–2 mm 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 normally placed in the socket formed at the time of the sinus lift procedure and left to integrate with bone. Bone integration normally lasts 4 to 8 months. The goal of this procedure is to stimulate bone growth and form a thicker sinus floor, in order to support dental implants for teeth replacement. Sinus dimensions and shape significantly influence new bone formation after transcrestal sinus floor elevation: with this technique, the regeneration of a substantial amount of new bone is a predictable outcome only in narrow sinus cavities. During presurgical planning, bucco- palatal sinus width should be regarded as a crucial parameter when choosing sinus floor elevation with transcrestal approach as a treatment option.

Complications

A major risk of a sinus augmentation is that the sinus membrane could be pierced or ripped. Remedies, should this occur, include stitching the tear or placing a patch over it; in some cases, the surgery is stopped altogether and the tear is given time to heal, usually three to six months. Often, the sinus membrane grows back thicker and stronger, making success more likely on the second operation. Although rarely reported, such secondary intervention can also be successful when the primary surgery is limited to elevation of the membrane without the insertion of additional material.

Besides tearing of the sinus membrane, there are other risks involved in sinus augmentation surgery. Most notably, the close relationship of the augmentation site with the sinonasal complex can induce sinusitis, which may chronicize and cause severe symptoms. Sinusitis resulting from maxillary sinus augmentation is considered a Class 1 sinonasal complication according to Felisati classification and should be addressed surgically with a combined endoscopic endonasal and endoral approach.  Beside sinusitis, among other procedure related-risks include: infection, inflammation, pain, itching, allergic reaction, tissue or nerve damage, scar formation, hematoma, graft failure, oro-antral communication / oro-antral fistula, tilting or loosening of implants, or bleeding .

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