Bone Grafting
Introduction
Inadequate bone quality and quantity has many causes, such as previous extractions performed without socket preservation, gum disease or trauma. To understand why extractions cause bone loss, you must first learn about the effect different types of stress have on bone. The different types of bone stress are internal and external stress. Internal stress is healthy and originates from teeth roots that transmit the bite force into the bone. Just like muscle that when stressed become bigger and stronger, bone when internally stressed becomes more abundant and denser. Similarly, muscles that are not stressed atrophy just as an arm in a cast for many months will atrophy. Paradoxically, external stress is unhealthy and also causes atrophy. External stress is the type of stress that a unsupported denture places on the bone. Studies have shown that a upper jaw will resorb up to four times faster under a denture. Another cause of bone loss is gum disease or periodontitis which is essentially an autoimmune disease. Toxins from the bacteria adhering to your teeth cause your body to attack itself and destroy bone. Trauma is the third common cause of bone loss.
Bone loss from these and other factors result in bone unsuitable for placement of dental implants. Dental implants are helpful because they retain bone by restoring internal healthy stress. In the past, patients with bone loss were not good candidates for placement of dental implants. Today, however, we have the ability to grow bone where needed thereby transforming previously difficient implant sites into sites that can accommodate implants of proper length and width that will support natural looking, well- functioning teeth.
Minor and Major Bone Grafting
There are many approaches to grafting bone. We have found the most elegant solution to be the simpliest. Rather than using bone obtained from a tissue bank or your own bone taken from elsewhere in your jaw, hip or tibia (below the knee), we use a small quantity of your own blood to grow bone. Please see our section on PRGF for a more complete explanation of this approach. At times, we use a small amount of your own bone or bone from other sources especially in severely atrophy cases, however, the majority of our grafting cases require no foreign substances or secondary surgical sites. Our approach also works very well to avoid sinus bone grafts which are required to augment bone in the posterior upper jaw. Again, severly atrophic maxilla's (upper jaw) will likely require sinus graft, however, we have found that in many cases, we can use bone from the implant procedure itself to gain the additional bone volume needed to complete the case. A limited (or internal) sinus graft also works well to atraumatically develop bone in the posterior maxilla. In addition, our approach allows us to create a membrane which is placed under the gum to protects the site and encourages bone regeneration. This is called guided bone regeneration or guided tissue regeneration.
Major bone grafts are typically performed to repair large 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 routinely performed in an operating room and require a hospital stay.
Bone Grafting Overview
For a brief narrated overview of the bone grafting process, please click the image on the right. It will launch our flash educational MiniModule in a separate window that may answer some of your questions about bone grafting.
Sinus Lift Procedure
The maxillary sinuses are behind your cheeks and on top of the upper teeth. Sinuses are like empty rooms that have nothing in them. Some of the roots of the natural upper teeth extend up into the maxillary sinuses. 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 bone to hold them in place. When the sinus wall is very thin, it is impossible to place dental implants in this bone.
There is a solution and it's called a sinus graft or sinus lift graft. The dental implant surgeon enters the sinus from where the upper teeth used to be. The sinus membrane is then lifted upward and donor bone is inserted into the floor of the sinus. Keep in mind that the floor of the sinus is the roof of the upper jaw. After several months of healing, the bone becomes part of the patient's jaw and dental implants can be inserted and stabilized in this new sinus bone.
The sinus graft makes it possible for many patients to have dental implants when years ago there was no other option other than wearing loose 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.
Ridge Expansion
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.
Nerve Repositioning
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 in the lower jaw. 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 second premolar, with the above-mentioned secondary condition. Since this procedure is considered a very aggressive approach (there is almost always some postoperative numbness of the lower lip and jaw area, which dissipates only very slowly, if ever), usually other, less aggressive options are considered first (placement of blade implants, etc.).
Typically, an outer section of the cheek side of the lower jawbone is removed in order to expose the nerve and vessel canal. Then we isolate the nerve and vessel bundle in that area and slightly pull it out to the side. At the same time, we will place the implants. Then the bundle is released and placed back over the implants. The surgical access is refilled with bone graft material of the surgeon's choice 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, in the area of the chin or third molar region, or in the upper jaw behind the last tooth. In more extensive situations, a greater quantity of bone can be attained from the hip or the outer aspect of the tibia at the knee. When we use the patient's own bone for repairs, we generally get the best results.
In many cases, we can use allograft material to implement bone grafting for dental implants. This bone is prepared from cadavers and used to promote the patients own bone to grow into the repair site. It is quite effective and very safe. Synthetic materials can also be used to stimulate bone formation. We even use factors from your own blood to accelerate and promote bone formation in graft areas.
These surgeries are performed in the out-office surgical suite under IV sedation or general anesthesia. After discharge, bed rest is recommended for one day and limited physical activity for one week.