Understanding Bone Grafting
Over time, the jawbone associated with missing teeth may deteriorate, leading to a reduction in bone quality and quantity, which can make it difficult to place dental implants. In the past, many patients with such conditions were not suitable candidates for implants.
However, advancements now enable us to regenerate bone where needed. This not only allows for the placement of implants with appropriate length and width but also enhances functional and aesthetic outcomes. Our office offers a variety of bone grafting procedures designed to facilitate successful implant placement.
Jawbone and Extraction Site Preservation
When tooth extraction is necessary—whether due to decay, abscess, gum disease, or injury—it is typically beneficial to prioritize preserving as much of the underlying jawbone as possible. After teeth are removed, the surrounding bone can begin to degenerate significantly. There are various options to help prevent this, many of which are most effective when considered before any extraction takes place. Some preservation procedures are ideally performed at the time of extraction. Our specialist in oral and maxillofacial surgery focuses on tooth removal, jawbone preservation, and dental implant placement.
What Happens When a Tooth Is Removed?
A specialized type of bone, known as alveolar “ridge” bone, surrounds each tooth solely to support it. When a tooth is removed, this bone begins to break down and “melt away”. Bone loss occurs in two main dimensions:
1. Horizontal width loss, where the bone around the socket collapses, making the remaining ridge narrower than it was when the tooth was intact.
2. Vertical height loss, which reduces the bone’s height over time.
This degeneration process is typically faster in areas where a partial or complete denture is worn.
Why Is Bone Preservation Important?
When teeth are removed, you have several options for replacement, each relying on bone support and contour to ensure proper function and aesthetics. Here are your options:
– Dental Implants: Dental implants act as root-like supports for replacement teeth. The more bone support available, the stronger and more stable the implants will be. However, if significant bone loss has occurred, implants may not be feasible without additional complex bone grafting procedures to rebuild the necessary support. Preserving bone early is much easier than reconstructing it later.
– Fixed Bridges: A fixed bridge is a restoration supported by the teeth adjacent to the missing tooth. The replacement tooth (pontic) fills the gap, but if bone is deficient, an unsightly space can form under the pontic, trapping food and potentially affecting speech.
– Removable Partial or Full Dentures: These options also function better with sufficient supporting bone, contributing to both comfort and stability.
Preserving bone at the time of extraction helps to maintain these replacement options for optimal results.
How Can Bone Be Preserved?
Preserving the alveolar ridge (jawbone) during and after tooth extraction involves two key phases. Oral surgeon takes a careful approach to remove teeth while retaining as much bone as possible. The second, crucial step in preventing socket collapse is adding bone replacement material to the extraction site.
There are various types of bone grafting materials and techniques, and your surgeon will discuss the most suitable option with you. After extraction, the socket is filled with a bone graft material and covered with a membrane. Initially, this graft material supports the surrounding tissue, and, over time, it is replaced by your own new alveolar bone, providing excellent support if you choose dental implants in the future.
While socket grafting preserves the bone, this support is not indefinite. To ensure lasting preservation, dental implants should ideally be placed two to six months after extraction and grafting. The implant places the jawbone under functional load, similar to a natural tooth, preventing the graft from resorbing over time.
Sinus Lift Bone Grafting
The maxillary sinuses, located behind the cheeks and above the upper teeth, are hollow spaces. In some cases, the roots of upper teeth extend into these sinuses. When upper teeth are removed, only a very thin wall of bone may remain between the maxillary sinus and the mouth. Since dental implants require sufficient bone for stability, a thin sinus wall can make implant placement challenging or impossible.
A sinus lift bone graft addresses this by gently raising the sinus membrane and adding bone graft material to the sinus floor. This procedure creates a stronger bone foundation, enabling the placement of dental implants in the back of the upper jaw where bone loss has occurred. Often, implants can be placed simultaneously with the grafting procedure, streamlining the restoration process.
Block Bone Grafting
When substantial resorption of the jaw ridge has occurred, a bone graft may be required to restore its height or width in preparation for dental implants. In these cases, the graft is sourced from another area within the mouth or body. This procedure involves removing a block of bone from one location and securing it with screws at the site where the dental implants will be placed. Typically, the bone graft is positioned and allowed to integrate with the jawbone over a period of four to six months before the dental implant is inserted.
These procedures may be performed individually or concurrently, depending on the patient’s specific needs. There are several potential sources for bone grafts. In the maxillofacial region, bone can be harvested from inside the mouth, such as from the chin, third molar area, or the upper jaw behind the last tooth. In more extensive cases requiring larger quantities of bone, grafts can be obtained from areas such as the hip or the outer part of the tibia near the knee.
Bone Expansion
Contrary to common belief, bone in the living body is not as hard or rigid as dried skeletal bone. In certain areas of the jaw, living bone is pliable enough to be gently stretched—a process known as bone expansion. This technique involves carefully widening the bone in specific areas to create more space for dental implants without the need for grafting. Bone expansion allows for greater flexibility in implant placement and can often be a minimally invasive alternative to other bone augmentation procedures
Bone Expansion Rationale
Bone expansion increases the available space in an area of the jaw, allowing for the placement of larger dental implants. Larger implants have a greater surface area, providing better stability and a stronger bond with the bone, which contributes to improved long-term outcomes. The primary goal of bone expansion is to create sufficient space to accommodate these larger implants in areas where bone volume may have been insufficient.
Although bone expansion is most commonly performed in the front of the upper jaw to replace incisors, it can also be done in other areas of the mouth as needed.
Bone Expansion Procedure
The procedure begins with a small hole being drilled into the bone at the site of expansion. A series of progressively larger bone expansion tools are then inserted into the hole. As the tools expand the bone, the walls of the bone gradually widen. Once the desired expansion is achieved, the hole can be filled with bone graft material, or a dental implant can be placed immediately. This technique allows the bone to expand and create the necessary space for implant placement.
Nerve Repositioning
In some cases, the inferior alveolar nerve, which provides sensation to the lower lip and chin, may need to be repositioned to create enough space for the placement of dental implants in the lower jaw. This procedure is carefully performed to ensure the nerve is moved safely, minimizing any risk to sensation in the lip and chin.
Immediate Dental Implant Placement
In certain situations, it is possible to extract a tooth and place a dental implant in the same procedure. This approach, known as immediate implantation, allows for a more streamlined treatment process, reducing the overall healing time and the number of procedures required for tooth replacement.
Guided Tissue Regeneration
Soft tissues, such as gum tissue, tend to grow quickly, while bone growth is much slower. After a surgical procedure, gum tissue can rapidly fill the surgical site, preventing bone from growing into the area where it’s needed for implant placement. To address this issue, a membrane barrier is used to cover the surgical site, preventing gum tissue from entering the area and allowing the bone to gradually fill the space without interference.
The membrane barrier effectively directs the gum tissue away from the surgical site, ensuring that bone can regenerate properly. This technique is known as guided tissue regeneration (GTR). Some practitioners may refer to it as guided bone regeneration (GBR), particularly since the focus is on regenerating bone to support dental implants.
Guided tissue regeneration can be used to repair bone defects around existing implants or to create additional bone in areas where there is insufficient bone for implant placement. The surgical site may be filled with different materials before being covered with the protective membrane barrier.
When there is sufficient bone height, width, and density, dental implant placement and success are generally guaranteed. However, many patients present with bone deficiencies. In these cases, regenerating the missing bone is essential for successful implant placement. While the process can be complex, it typically achieves high success when performed with the right skills and expertise.
Graft Materials for Bone Regeneration
Autogenous Bone: Considered the gold standard for bone grafting, autogenous bone is taken from the patient’s own body, often from nearby areas such as the chin, the tuberosity (the upper part of the jaw), or occasionally the hip or other areas. This bone is highly compatible with the patient’s own tissue, promoting the best healing outcomes.
Allografts: These are bone grafts obtained from genetically unrelated individuals of the same species, typically cadaver bone that has been specially processed for medical use. Freeze-dried cortical bone is a common form of allograft.
Xenografts: Sourced from other species, typically cows, xenografts are frequently used in bone regeneration. These materials work through two main mechanisms: Osteoconduction – the formation of new bone from host cells along a compatible framework provided by the graft material; or Osteoinduction – the stimulation of new bone formation through the biomechanical differentiation of the host’s mesenchymal cells. Bone Morphogenic Protein (BMP) is a key substance in osteoinduction, showing promise in stimulating bone growth rapidly and predictably.
Barrier Membranes: In addition to grafting materials, membranes are often used to guide new bone formation. When a bone defect occurs, there is competition between bone cells and epithelial or connective tissue cells to fill the defect. If left unregulated, epithelial and connective tissue cells tend to dominate, hindering bone regeneration. A membrane barrier blocks these non-bone cells from entering the site, allowing bone cells to regenerate more effectively and “win” the competition for space.
These materials, combined with techniques like BMP and membrane barriers, offer significant advancements in bone regeneration, helping to create the necessary conditions for successful dental implants and other procedures.