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Over a period of time, the jawbone near the missing teeth atrophies (shrinks) or becomes resorbed. This often leaves a condition in which there is poor quality and quantity of bone suitable for placement of dental implants. Without bone grafting, these patients do not have ideal conditions for dental implants.
Today, we have the ability to grow bone where needed. This not only gives us the opportunity to place implants of proper length and width, it also gives us a chance to restore proper form and function.
Major Bone Grafting
Bone grafting can prepare implant sites with inadequate bone structure due to previous extractions, gum disease or injuries. The bone is either obtained from a tissue bank or your own bone is taken from the jaw, hip or tibia (below the knee). Sinus lift bone grafts are commonly performed to thicken the bone in the back part of the upper jaw. Special membranes are sometimes utilized to protect the bone graft and encourage bone regeneration. This is called guided bone regeneration or guided tissue regeneration.
Major bone grafts are typically performed to repair defects of the jaws. These defects may arise as a result of traumatic injuries, tumor surgery, or congenital defects. Large defects are repaired using the patient’s own bone. This bone is harvested from a number of different sites depending on the size of the defect. The skull (cranium), hip (iliac crest), and lateral knee (tibia), are common donor sites. These procedures are usually performed in an operating room and require a hospital stay.
Sinus Lift Procedure
The maxillary sinuses are located in a bone called the maxilla on either side of your nose and above your upper teeth. Sinuses are like hollow pyramid shaped bone cavities. It is common for roots of the upper teeth to extend up into the sinus. When these upper teeth are removed, there is often just a thin wall of bone separating the maxillary sinus and the mouth. Dental implants need at least 10mm of bone to hold them in place. When the sinus wall is very thin, it is impossible to place dental implants in this bone.
The answer to this lack of bone is called a sinus floor graft or sinus lift graft. The oral surgeon makes a small hole in the side of the upper jaw and lifts up enters the sinus from where the upper teeth used to be. The sinus membrane is then lifted upward and donor bone is inserted into and along the floor of the sinus. The floor of the sinus is also the roof of the upper jaw. After several months of healing, the bone becomes a solid part of the upper jaw and can safely stabilize dental implants.
The sinus graft makes it possible for many patients to have dental implants when years ago there was no other option other than wearing standard dentures.
If enough bone between the upper jaw ridge and the bottom of the sinus is available to stabilize the implant well, sinus augmentations and implant placement can sometimes be performed as a single procedure. If not enough bone is available, the sinus augmentation will have to be performed first, then the graft will have to mature for several months, depending upon the type of graft material used. Once the graft has matured, the implants can be placed.
In severe cases, the ridge has been reabsorbed and a bone graft is placed to increase ridge height and/or width. This is a technique used to restore the lost bone dimension when the jaw ridge gets too thin to place conventional implants. In this procedure, the bony ridge of the jaw is literally expanded by mechanical means. Bone graft material can be placed and matured for a few months before placing the implant.
Within the lower jaw, the inferior alveolar nerve, which gives feeling to the lower lip and chin, may need to be moved in order to make room for placement of dental implants. This procedure is limited to the lower jaw and indicated when teeth are missing in the area of the two back molars and/or and 2nd premolar, with the above-mentioned secondary condition. Since this procedure is considered a very aggressive approach (there is almost always some permanent numbness of the lower lip and jaw), usually other, less aggressive options are considered first (placement of fewer or smaller implants).
Nerve repositioning is performed by removing an outer section of the lower jaw in order to expose the nerve. The nerve and blood vessels are then gently pulled out to the side and held safely away from the jaw while the implants are placed. Then the nerve bundle is released and allowed to drape back over the implants. The surgical access is refilled with bone graft material and the area is closed.
These procedures may be performed separately or together, depending upon the individual’s condition. As stated earlier, there are several areas of the body that are suitable for attaining bone grafts. In the maxillofacial region, bone grafts can be taken from inside the mouth either in the chin or in the area where wisdom teeth are located in either the upper or lower jaw.
Minor Bone Grafting
In many cases, we can use graft material from animal (bovine) or human (cadaver) for bone grafting to prepare for dental implants. It is quite effective and very safe. Synthetic materials can also be used to stimulate bone formation. These graft procedures are usually performed in the office under IV anesthesia.