Maxillary (ie: Upper Jaw) and Mandibular (ie: Lower Jaw) Bone Grafting is the replacement or augmentation of the portion of the jaw bone that anchors the teeth, utilizing one or more variety of surgical techniques. These procedures are often performed in order to reverse the loss (or resorption) of bone that may have occurred due to tooth loss, trauma, disease or ill-fitting dentures, and to rebuild the bone structure beneath the gums in preparation for the placement of dental implants or other tooth replacements. “Sinus Lifts” and “Alveolar Bone Grafting” are two procedures which are commonly performed by Oral & Maxillofacial Surgeons in their daily practice.
When bone grafting is implanted in the jaw, it doesn't just simply fill a void in the bone; it may also help promote new bone growth in that location. When successful, bone grafting can restore both the height and width of your jaw bone. Understand that some types of grafts or techniques are better suited for correcting vertical defects (ie: such as “distraction” or “sinus lift grafting”), while some other techniques are better suited for correcting transverse defects in the bone (ie: “ridge splitting”, or “onlay” bone grafting).
You have multiple options/alternatives for the specific materials or technique used in your bone replacement surgery. Each of these options has certain pros and cons, and they differ not only in how they help promote bone formation, but also in costs and potential risks and benefits. The following discussion is designed to help educate you regarding your options, however, more specific details regarding your specific clinical need and information related to the techniques listed below can be obtained from your doctor: Often 3-D cone-beam CT scanning is performed in order to fully assess the three-dimensional anatomy of an individual prior to proceeding with surgery.
Bone Grafting materials are generally grouped into one of four broad categories:
Also called autografts, these types of grafts are made from the patient's own bone, harvested from elsewhere in the body. Typical harvest sites include the chin, jaw, bone of the lower leg (tibia), hip (iliac crest) or the skull (cranium).
Autogenous bone graft has traditionally been considered the "gold standard" as a graft material because it is "live bone" complete with the living cellular elements that enhance bone growth. These elements include factors which influence osteogenesis (bone formation from cells), osteoconduction (bone formation via migration upon a scaffold) and osteoinduction (bone formation by proteins such as BMP [bone morphogenetic proteins], which direct cells to form new bone). When bone is transferred using the autogenous technique, commonly only 8-10% of the transferred cells remain viable.
A potential downside of autogenous bone grafting, however, is that it involves a second procedure (and second surgical site) in order to harvest the bone, which may be painful and not in some patients' best interest, depending on their condition (a second surgical site also carries the risks of harvesting in that location- including damage to adjacent structures, and infection). It also may not be a viable option in instances where the patient's overall bone quality and/or density is poor, or when a large volume of graft material is required. As this material is derived from the same person in whom it is being used, communicable infectious risks (ie: transmitted from another individual) are nonexistant. Grafting within the oral cavity, however, is potentially problematic, as the oral cavity is considered a contaminated region, and infection due to contamination may result. Antibiotics are commonly prescribed when this technique is used.
One unique form of autogenous bone grafting involves the technique of Distraction Osteogenesis (DO). The technique of DO involves creating a bone cut (osteotomy) over which tension is gradually applied with a distraction device (after an initial period of immobilization). The tensile force induced by the device induces the body to lay down (or form) new bone. DO is commonly used to grow bone in large (discontinuity) defects of the jaw, in repositioning of major jaw segments, or in isolated vertical defects of the upper or lower alveolar jaw bone (transverse alveolar defects are not as easily dealt with using DO). DO requires placement of a distraction device, and this device has to be removed after a period of approximately 8-9 weeks. Costs for this technique are generally higher, due to the costs of the device, surgical procedure, and device removal.
Allogeneic bone, also called allograft, is bone derived from a genetically unrelated member of the same species. It's typically non-vital (dead) bone harvested from a cadaver, then processed using a freeze-drying method that extracts all the water via a vacuum.
Allogeneic bone cannot produce new bone on its own — it's neither osteogenic (like autograft) nor osteoinductive (like BMP). Rather, its primary mechanism of action is that it is osteoconductive, and serves as a framework or scaffold over which bone from the surrounding bony walls can grow to fill the defect or void. Also, as this material is harvested from a cadaver source, there is always theoretical (albeit minimal) risk of infection or communicable disease transmission. These materials are generally purchased from reliable vendors who adhere to standards for procurement and processing according to the American Association of Tissue Banks — and over which the FDA exerts control and monitoring.
Similar to allogeneic bone, xenogenic bone is non-vital bone derived from another species, usually a cow. Because the potential for immune rejection and contamination by viral proteins is higher in bovine bone than in human cadaver bone, xenograft material is processed at very high temperatures (600-1,000 degrees Celsius). Xenograft's mechanism of action is similar to that of allograft – it serves as an osteoconductive framework on which bone from the surrounding area can grow to fill the void. While no recorded case has originated from xenogenic bone grafting, bovine spongiform encephalopathy (BSE)- similar to “mad-cow” disease, is a prion disease linked to bovine sources. While no case of BSE arising from a Xenogenic bone graft has ever been reported, it is felt that the methods noted above used during processing are effective in greatly minimizing (or eliminating) these risks.
The above grafting options are preferred by many patients and dental professionals alike because they eliminate the potentially painful second harvesting procedure. However, because both allografts and xenografts lack autograft's bone forming properties, bone regeneration may take somewhat longer than it does when using the patient's own bone and the outcome may be less predictable or reliable (ie: less volumetric fill may result). Transmission of disease from the donor to the recipient, however, is a theoretical risk with the use of all allografts and xenografts.
Bone morphogenetic proteins (BMPs) are proteins naturally produced in the body that regulate bone formation and healing. A commercially available recombinant BMP is INFUSE® Bone Graft (rhBMP-2/ACS). The active ingredient in INFUSE® Bone Graft – rhBMP-2 – is a manufactured version of a protein already present in the body that promotes new bone growth.
Bone graft substitutes are commercially produced synthetic products that have many of the same bone forming properties as human bone, and are a safe and proven alternative to autograft and allograft.
One of the advantages of using a bone graft substitute instead of autogenous bone is that it eliminates the need to harvest the patient's own bone, thus potentially reducing the risk and pain associated with the harvest procedure. As these materials do not (unto themselves) stimulate bone formation (but are considered osteoconductive), use of these materials in an onlay technique (ie: lateral mandibular grafting) is typically contraindicated (these materials are more commonly used for socket grafting).
Demineralized Bone Matrix (DBM)/ Demineralized Freeze-Dried Bone Allograft (DFDBA)/ Mineralized Bone Allograft/ “Banked Bone” — a product of processed allograft bone, DBM/DFDBA contains collagen, proteins and growth factors that are extracted from the allograft bone. It is available in the form of a powder, crushed granules, putty, chips or as a gel that can be injected through a syringe. These materials are typically resorbed by your body after placement, and generally work to form a latticework for your body’s own osteoprogenitor cells to adhere to. As these materials are essentially allograft materials, the same risks of allografts as noted above apply to these materials. Puros is a commercially available preparation of mineralized allograft — available in both a powder, as well as block form.
Bone Ceramics — Ceramics are also used as a substitute for bone grafts, and are available in many forms such as porous and mesh. Although ceramics may provide a framework for bone growth (ie: are osteoconductive), they contain none of the natural proteins that influence bone growth and may be associated with inflammation in some patients (they are not osteoinductive or osteogenic). Since these materials are man-made, there is minimal, if any, infectious risks with the use of these materials. These materials are generally resorbed by the body over time, hopefully replaced by normal bone. Cerasorb (Beta Tri-Calcium Phosphate), Perioglass, and Hydroxylapetite are examples of bone ceramics.
Graft Composites — Graft composites use combinations of other bone grafting materials and/or bone growth factors to gain the benefits of a variety of substances. Typical combinations in use today include: a collagen/ceramic composite, which closely reproduces the composition of natural bone; DBM combined with bone marrow cells, which aid in the growth of new bone and a collagen/ceramic/autograft composite. Some of these materials may resorb gradually; if they do not resorb quickly enough, drilling through this material (at the time of implant placement) may be problematic. BioOss is an example of a xenogenic graft composite material.
Bone morphogenetic proteins, or BMPs, have been studied for decades because of their remarkable ability to heal bone and eliminate the need for bone graft harvesting from other parts of the body. Approximately 20 BMPs have been discovered, but only six appear capable of initiating bone growth. Of these, rhBMP-2 has been studied more than any other BMP and is FDA approved for use in certain spinal, tibial (leg) and oral and maxillofacial surgeries.
Naturally occurring BMP is found within the bone itself, but only in small amounts. To provide clinically useful and reproducible amounts of isolated, human BMP, it must be manufactured in a special facility.
Scientists isolated the gene for one protein (BMP-2) from bone tissue and used well-established molecular biology techniques to create genetically engineered cells. These cells then produce large quantities of rhBMP-2. A similar process is used to manufacture other proteins, such as insulin. The recombinant form of rhBMP-2 is identical to the natural form in both its chemistry and its ability to grow new bone.
During surgery, rhBMP-2 is soaked onto and binds with an absorbable collagen sponge (ACS) that is designed to resorb, or disappear, over time (this sponge, however, is derived from a bovine source). As the sponge dissolves, the rhBMP-2 stimulates the cells to produce new bone. The rhBMP-2 also goes away once it has completed its task of initiating the normal bone healing process.
rhBMP-2 may be used to promote bone growth in several areas of the body. In the spine, the rhBMP-2 grows bone in the disc space to join or fuse the vertebrae to reduce back pain and stabilize the spine. In certain tibial fractures, rhBMP-2 has been shown to help heal broken bones. In instances of jaw bone resorption, rhBMP-2 may be placed in the section or sections of the jaw bone that need to be built back up in preparation for dental implants.
One of the primary advantages of INFUSE® rhBMP-2 Bone Graft is that it is an alternative to autograft – the use of autogenous bone (from the hip, rib, leg, jaw or chin) for implantation into a void or defect elsewhere in the body, such as the bones of the jaw.
Prior to INFUSE® Bone Graft, autogenous bone traditionally provided patients with the best grafting results in oral surgeries such as a sinus or socket augmentation. INFUSE® Bone Graft eliminates the need for the bone-harvest surgery that autograft requires, an additional procedure that, depending on the location, may be painful for some patients and lengthen the overall healing process. Except for the absorbable collagen sponge, as the rh-BMP-2 material is derived via a recombinant method, there is essentially no infectious risk associated with use of this product, as seen with allografts and xenografts.
INFUSE® Bone Graft also may be used for oral procedures in which autogenous bone is not typically used, such as a localized alveolar ridge augmentation. INFUSE® Bone Graft may restore bone in the extraction socket of a tooth that has been removed, allowing for future dental restoration such as the placement of dental implants.
During your procedure, the rhBMP-2 protein, which is in powder form, is mixed with sterile water. The solution is then soaked into the ACS. Your surgeon will then place the protein-soaked ACS into the space he or she has prepared and then follow the normal surgical care protocol for your procedure.
The specific details of your particular oral surgery will vary, depending on the condition to be treated. Please discuss your treatment plan and the use of INFUSE® Bone Graft thoroughly with your dental surgeon.
While research on INFUSE® rhBMP-2 has taken place over the past 10-20 years, widespread use in the public is just now beginning. As with any new medical technology, INFUSE® rhBMP-2 is currently an expensive treatment alternative. As with all new medical technologies, costs are a factor, with current minimum costs of approximately $2500 (for an extraction socket)- and upwards of $3500-6500 for use in bilateral sinus lifts and larger grafting procedures (some medical insurance plans may provide coverage for use of this product, but this is difficult to predict). Please ask your doctor for an estimate of the volume of INFUSE® rhBMP-2 required for your specific planned procedure.
The absorbable collagen sponge used with the INFUSE® rh-BMP-2 material is derived from a bovine source. This material is composed of a very purified Type I collagen, and undergoes an extensive purification process following harvesting (allergies to this material, while reported, are considered rare; Approximately 3% of the population is allergic to bovine collagen; these individuals should not receive these implants). Bovine Collagen should not be used if you have:
While no report of transmissible infection has ever been documented with bovine collagen material, this theoretic risk persists.
From a practical perspective, INFUSE® rh-BMP-2 when used as directed with the absorbable collagen sponge technique (ie: the rh-BMP-2 is first regenerated in a saline solution, and this solution is then allowed to impregnate a collagen-sponge, which is applied- or grafted- to the needed surgical site), is a compressible material. This compression can prove problematic when attempting to graft certain regions (such as with “onlay grafting” or grafting of “through and through” bone or alveolar defects), as the overlying soft tissues often will compress this material during the healing phase, thereby diminishing the volume of regenerated bone. Many times, this soft tissue compression can completely eliminate any benefit to use this material in this fashion.
More recently, in an effort to explore options for use of rh-BMP-2 in an onlay fashion (and in an effort to minimize these soft tissue compressive forces) some doctors have used titanium meshwork to overlay the areas of grafted material, thereby minimizing the compressive soft tissue effects (the titanium meshwork is removed after adequate bone regeneration has taken place). Others have explored the use of combining rh-BMP-2 with other alternative non-compressible materials (ie: other than the collagen sponge supplied with the product- such as with freeze-dried cancellous bone). While not officially FDA-approved at this time, some have been combining the rh-BMP-2 regenerate solution with demineralized freeze-dried bone putties (mixing these in a 1:1 volume), and applying this putty-rh-BMP-2 mixture to the site of needed grafting (in an “off-label” fashion). Others are additionally combining this putty-rh-BMP-2 mixture with calcified bone blocks (also taken from a cadaveric source) which are fixated in place with titanium bone screws (obviously, these techniques negate the benefit of using a single recombinant material, as cadaveric sources are used). While the results of these techniques have yet to be published, there is widespread word within the profession that excellent clinical results have been obtained, and that this may be a very viable technique. Other types of BMP are also being used (namely, rh-BMP-7). Research in this area is ongoing.
INFUSE® rhBMP-2 should not be utilized in pregnant women, or in those women anticipating pregnancy within the next year. Use of this product in persons less than 18 years of age has not been studied. If you are hypersensitive to bovine (cow) Type I collagen or recombinant human Bone Morphogenetic Protein-2, you should not receive this product. Those persons with active cancer are not candidates for use of INFUSE® rhBMP-2, as are those with active infections close to the area of planned placement of this product.
Although not seen in studies performed by the manufacturer, there is a remote possibility that too much bone may form at the implantation site (exuberant bone formation) or bone may form at a location away from the implant site (ectopic bone formation).
Please discuss with your doctor any questions you have related to the above material, or, questions related to your unique and specific procedure.
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