Sinus Lifting and Bone Grafting: Implants When Bone Is Insufficient

One sentence comes up often for people considering implant treatment: "You do not have enough bone for an implant." It is usually understood as meaning treatment is impossible, yet contemporary dentistry has well-established surgical methods for increasing bone volume. Sinus lifting and bone grafting are the most common of these. In this article we look at why bone resorbs, how its adequacy is assessed, what grafting and sinus lifting actually involve, and when graft-free alternatives may come into play.

Why Do Implants Need Bone?

A dental implant is designed as a screw placed inside the jawbone that integrates with it over time. For this integration (osseointegration) to happen, there has to be healthy bone of sufficient height and thickness around the implant. When bone volume decreases, the implant cannot find adequate support, and both initial stability and long-term behaviour are affected. You can read about the general process on our implant treatment page.

Why Does the Jawbone Resorb?

Bone maintains its volume as long as it is stimulated by the chewing forces passing through it. When a tooth is removed, that stimulus disappears and the bone in the area gradually thins. The main causes of bone loss are:

• Loss of stimulation after tooth loss: The first year after extraction is the period in which the change in bone volume is most pronounced.
• Advanced gum disease: The inflammatory process affecting the supporting bone around a tooth reduces bone even before the tooth is lost. For details, see our article on periodontitis.
• Long-term removable denture use: A denture does not transmit chewing force to the bone the way a tooth root does, so it does not halt resorption.
• Trauma and infection: A fracture, a long-untreated abscess or a cyst can cause localised bone loss.
• Expansion of the maxillary sinus: In the posterior upper jaw the sinus cavity may expand downwards after tooth loss, reducing the bone height left for an implant.

How Is Bone Adequacy Assessed?

Because clinical examination alone is not enough, suitability of bone for implants is assessed with three-dimensional imaging. A panoramic radiograph gives a general picture, but cone beam computed tomography (CBCT) is used to see bone thickness, the distance to neighbouring anatomical structures and the position of the sinus floor. This imaging makes it possible to plan before surgery at what angle, at what length and in which region the implant can be placed. The assessment covers not only the amount of bone but also its quality and the condition of the gum tissue.

What Is a Bone Graft?

Bone grafting is the placement of a material that supports bone formation in a deficient area. The graft material does not "produce" new bone by itself; it acts as a scaffold so that the body's own cells can migrate into the area and form new bone. The main graft types used in clinical practice are:

• Autogenous graft: Tissue taken from the person's own bone, most often from the jaw region.
• Allograft: Processed and sterilised human-origin tissue bank products.
• Xenograft: Mineral-structured materials of animal origin from which organic components have been removed.
• Alloplastic graft: Synthetically produced bone substitute materials.

The graft is usually covered with a membrane. Its purpose is to prevent faster-growing soft tissue cells from filling the graft area, giving bone cells time to work. Which graft type and technique is appropriate depends on the size and location of the defect.

What Is Sinus Lifting?

Sinus lifting is specific to the posterior region of the upper jaw. This area sits below the maxillary sinus cavities located on either side of the nose. If bone resorbs from below while the sinus expands downwards after tooth loss, the bone height left for an implant can fall to just a few millimetres. During sinus lifting, the thin membrane lining the sinus cavity (the Schneiderian membrane) is carefully raised and graft material is placed into the space created beneath it, increasing the bone height available for the implant.

Open (Lateral) Technique

Preferred when bone height is markedly reduced. A small window is opened from the side of the gum to reach the sinus membrane, the membrane is elevated and graft material is placed. Because it gains greater volume, it is used in advanced loss and involves a longer healing period.

Closed (Crestal) Technique

Applied when the existing bone height is borderline. The sinus floor is pushed up a few millimetres through the socket prepared for the implant. It is a less invasive approach and in many cases the implant can be placed in the same session.

Can the Procedure and the Implant Be Done in One Session?

This depends on the existing bone height. If the remaining bone can provide initial implant stability, grafting and implant placement may be planned simultaneously. If bone is severely reduced, grafting is done first, healing is awaited and the implant is placed at a second stage. Graft healing usually takes several months depending on the site and the material used, and varies from person to person. Although staged planning extends treatment, it aims to improve the quality of the foundation the implant will sit in.

Are There Alternatives That Avoid Grafting?

Not every case of insufficient bone has to be solved with a graft. In some cases the existing bone can be used through a different implant placement strategy:

• Tilted implant approach: In the All-on-4 technique, posterior implants are placed at an angle to use the denser bone in front of the sinus cavity, which reduces the need for sinus lifting in many cases. For details, see our article on the All-on-4 implant technique.
• Zygomatic implants: In advanced upper jaw bone loss, special implants extending into the cheekbone may be considered. See our article on zygomatic implants.
• Short and narrow diameter implants: These may be evaluated where bone height is limited and force distribution is planned appropriately.

Our article on implant treatment in the edentulous jaw may also be a useful guide for comparing options.

What Should Be Considered Afterwards?

The first days after grafting and sinus lifting are decisive for keeping the graft in place and stable. Instructions from your dentist vary from person to person, but the following headings usually stand out during this period:

• After sinus lifting, avoiding forceful nose blowing and keeping the mouth open when sneezing is advised so that pressure in the area is not increased.
• Staying away from hard, hot and finely grained foods in the first days protects the healing site.
• Smoking is among the leading factors that adversely affect tissue healing.
• Oral hygiene continues, but the surgical site is protected in the way your dentist describes.
• Prescribed medication is used as directed and follow-up appointments are kept.

For the period after the implant has been placed, our article on implant aftercare and the healing process gives detailed information.

Who Needs Additional Assessment?

Uncontrolled diabetes, active sinusitis, the use of certain bone metabolism medications, heavy smoking and untreated gum disease are situations that require separate consideration in graft and implant planning. These headings do not mean treatment is ruled out; they mean planning and timing need to be reconsidered individually. For this reason it is important to share your existing conditions and regular medications with your dentist.

Summary

Insufficient bone is not regarded as an insurmountable barrier to implant treatment; it is handled as part of planning. Sinus lifting and bone grafting are established methods for increasing deficient bone volume, while in some cases tilted implant approaches can reduce the need for grafting. Which route is appropriate depends on the degree of bone loss, the region involved and the person's general health.

This article is for general information. Determining the approach that suits you requires clinical examination and assessment with three-dimensional imaging.