What is Bone Grafting?
When teeth are lost, the alveolar bone that previously housed them begins to dissolve away in a process called resorption. Depending on the rate of resorption, the remaining bone may be insufficient to replace the missing tooth with a dental implant. If the missing tooth is to be replaced with a fixed bridge, the prosthetic replacement tooth (pontic) may look artificially large if the bone and gum tissue (gingiva) have resorbed significantly.
One solution to this dilemma is to graft new bone onto the site. This process is sometimes referred to as site development, which refers to the fact that proper bony and gingival contours need to be re-established before ideal tooth replacement can be done. There are several ways of performing a bone graft.
First, bone resorption can be prevented by packing the tooth socket with powdered bone graft material (called a socket graft, or ridge preservation) at the time of tooth removal.
Bone grafting can also re-establish the height (by a limited amount) and width of alveolar bone that has already been lost following removal of a tooth. A block cortical graft involves attaching a solid piece of bone to the deficient area, and attaching it with fixation screws while it integrates into position over several months.
Roots of the upper back teeth often project up into a hollow chamber inside the cheek bones, called the maxillary sinus. When any of those teeth are lost, bone may resorb from the sinus floor, as well as the other walls of the tooth socket. It can usually be regenerated in a procedure known as a sinus lift or sinus elevation.
Bony defects sometimes occur around teeth with multiple roots. Such areas can often be treated by guided tissue regeneration (GTR).
The process of Bone Grafting
There are two common bone graft techniques for assuring an adequate volume of bone at the site of a missing tooth: ridge preservation with a tooth socket graft is used to prevent bone loss; and block cortical graft procedures are used to widen narrow bony ridges where resorption has already occurred. Other types of bone grafting procedures performed in dentistry utilize similar techniques, including the commonly prescribed sinus elevation (sinus lift) procedure. The goal of a sinus elevation is the same: to provide enough bone to place dental implants in the upper jaw, where they would otherwise be sticking up into the air space of the maxillary sinus.
Bone grafting materials
For most bone grafting procedures, powdered bone is used, at least to some extent. Human bone powder from a tissue bank (allogenic graft material) is used most commonly in the United States. After the bone is harvested from the donor, it undergoes a series of rigid sterilization and purification procedures. It is reduced to small particles, packaged in sterile vials and shipped to the dentist. The lot is traceable to the donor through the entire process by unique tracking numbers. An alternative bone material is bovine (cow) bone. Some dentists, especially those outside the United States, prefer to use synthetic materials.
Before the procedure
If you take blood thinning medications or drugs that inhibit platelet aggregation, particularly if your bleeding time is elevated (as measured using the INR value), your dentist and/or physician may require you to suspend those medications temporarily to have any oral surgical procedures, including bone grafting. This is due to the possibility for prolonged bleeding from the surgical area.
If you are anxious about dental procedures, your dentist may recommend sedating you for the procedure. There are several methods of relaxing patients for dental treatment, including oral anti-anxiety pills; inhaled anti-anxiety medication like nitrous oxide; and intravenous anti-anxiety medication. Your dental plan may not pay benefits toward sedation.
You should have a good idea what the process involves after reading this material. Your procedure may vary from that described, and you should discuss specific details with the dentist. Bone science and tissue engineering are rapidly developing areas of dentistry and medicine, and it is possible that new techniques may be available which may be of benefit to you.
Some advantages and benefits of bone grafting
- Preserves or restores the natural bone volume where teeth have been removed, so that the most natural appearing tooth replacement (e.g. dental implant, fixed bridge) can be done.
- Can increase the bone density at the graft site, which may increase the early stability of an implant. Increased bone density may also decrease the rate of bone loss if a significant amount of time must elapse before the missing tooth site is restored with an implant or bridge.
- Allows the placement of dental implants into sites that would not be possible if bone grafting was not accomplished.
Disadvantages and risks of bone grafting
- If you are taking bisphosphonate medications (a drug to reduce the effects of osteoporosis or treat certain cancers), you may be required to go off of the medication for a period of time prior to undergoing bone grafting procedures. Bisphosphonates decrease the blood circulation in the head and neck bones, possibly enough to impair healing and invite infection following surgical procedures like tooth extractions. This is especially true if you receive the medication intravenously, or are also taking immunosuppressive drugs like corticosteroids.
- If you have a history of radiation treatment that may have involved the head and neck, you may be at risk for developing osteoradionecrosis following surgical procedures like bone grafting. Essentially, this means bone death secondary to radiation, which destroys small blood vessels that supply the bone. Even if you don’t develop osteoradionecrosis, the bone graft itself may fail to integrate with your bone due to poor blood flow to the graft site.
- Bone grafting requires the use of anesthetic, which has risks of its own (generally minor ones). Your dentist may provide you with specific information.
- Bone grafting, like any surgical procedure, has general post-surgical risks: pain, swelling, bruising, bleeding, and infection. Most of the early symptoms (pain, swelling, bruising) can be managed with anti-inflammatory medications (check with your physician or dentist before taking any unprescribed medications). Your dentist may provide other specific instructions for addressing your symptoms following tooth removal (extractions). Frequently, dentists will prescribe pain relievers for bone grafting procedures, but the specific medication will depend on the age and health history of the patient. Generally pain is not severe following bone grafting. Bleeding after bone grafting procedures is normally minimal. If you feel you’re experiencing an abnormal amount, apply direct pressure to the area and call your dentist.
- Frequently, dentists will prescribe antibiotics to be taken a day or so before the procedure through 7 to 10 days after the procedure to minimize the likelihood of developing an infection. Infection is the most common way for bone grafts to fail. Failure by infection means a failure for the graft to be integrated into the host (i.e. “your”) bone.
- Bone grafting in a few areas of the mouth can be accompanied by the risk of nerve injury. If this occurs, the worst case scenario includes permanent numbness in the area supplied by the injured nerve. The incidence of this is relatively low, but you should discuss the possibility with your dentist ahead of time.
- You may experience loss of, or reduced chewing function in the surgical area(s), which is normally temporary. You may experience limited ability to open your mouth, which is also normally temporary.
- Additional risks depend on the type of bone graft procedure you’re having done, and the area of the mouth where the graft is required. If the graft involves use of powdered bone materials only, there will be no donor site surgery, and hence no morbidity (i.e. complications) associated with harvesting the material. If the surgical plan involves using your own bone for all, or part of the graft, there will be a second surgical site—the donor site, which may also produce post-operative pain, swelling, infection, bleeding and bruising.
- The degree to which the goals of grafting are met can determine whether the procedure is successful or not. For example, the pre-operative goal may be to obtain a wide enough bony ridge to place a dental implant. Although the graft may integrate, and some additional width may be obtained, it may not be enough width to place the size of implant that is desired, and a secondary grafting procedure may be necessary. Your dentist will be able to identify specific risks that accompany your unique situation.
- Your health history may affect the prognosis for a graft, and may even present contraindications for surgery of any kind, including oral surgery. Among the health risk factors for bone surgery are a history of poorly controlled diabetes, radiation to the head or neck, conditions producing abnormal bone metabolism (such as osteoporosis or altered parathyroid gland function), and certain medications, like bisphosphonate drugs as mentioned. Your dentist will generally review your health history carefully with you prior to performing bone grafting procedures.
- Although the risks of using bone graft material from a tissue bank are thought to be extremely low, due to donor screening and rigorous purification procedures for the donated bone, there is still a theoretical pathway for disease transmission from donor to host. Generally, the benefits of using tissue bank bone are considered to greatly outweigh the risks on this point. If you have concerns, you should discuss this topic in more detail with your dentist.
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