What are bone grafts
Bone grafts are bio-materials that help in the formation of new bone. They can originate from:
- other parts of the jaw or the ilium (pelvic area) of the same patient (auto-grafts)
- another donor’s bone, which has undergone specific treatment and sterilization procedures (allo-grafts)
- an animal’s bone material, usually from cattles or pigs, that have undergone specific treatment and sterilization procedures (xeno-grafts)
- synthetic material (alloplastic implants)
- bone morphogenetic proteins and growth factors
Except auto-grafts, all other types of grafts are available in the market. Due to their processing and the scrutinous assessment of quality control, they are totally safe for the patient. Usually, they are in a dried status, in the form of small granules, which, when dissolved in saline water, turn into a putty compound. In some other cases they come in a gel form.
Membranes are bio-materials that are used for the isolation and protection of the bone graft from the gingiva (gums). They can be absorbable (made of collagen or pericardium) or non-absorbable (made of Gore-Tex). Depending on the case, the appropriate type of membrane that will be used is chosen. In some bone grafts, however, the use of a membrane is not obligatory.
in granule form (Bio-Oss)
in gel form (Emdogain)
Where bone grafts are used
Bone grafts are bio-materials that help in the formation of new bone. Some bone grafts achieve this by releasing growth factors that stimulate the patient’s bone cells to produce new bone. Other bone grafts, function as a scaffold which protects and supports the formation of new bone. Depending upon their mode of action, bone grafts and membranes, solely used or in combination, can have various applications such as:
- in the formation of new supportive bone around a tooth that has lost bone due to periodontitis (guided tissue regeneration)
- in the preservation of the dimensions of the jaw bone after tooth extraction (socket preservation)
- in the maxillary sinus elevation
- in the increase of the dimensions of the bone, in deficient areas of the jaw (ridge augmentation)
The most common uses of a bone graft are socket preservation and ridge augmentation in order to obtain enough bone volume to place implants. The bone grafts, depending on the case, can be simultaneously placed with the dental implants, thus reducing the treatment period or the number of surgical sessions.
Periodontitis leads to the destruction of the gingiva and of the jaw bone that supports the teeth. During periodontal therapy, most often, although plaque/tartar are removed and the tissues become healthy, the supportive bone around the teeth is not regenerated. In some cases, however, depending on the morphology of the bone defects, the periodontist, using bone grafts and special surgical techniques, can regenerate new supportive bone around the teeth and hence increase their support.
This process is called Guided Tissue Regeneration. The bone graft is surgically placed under local anesthesia and after the plaque has been removed. Typically, over the bone graft a special absorbable membrane is placed in order to protect the graft. Radiographically the new bone is visible after about six months.
Normally, after tooth extraction the bone of the jaw in that region gets resorbed, and hence the jaw bone becomes thinner. This change in bone dimensions may impair implant placement or affect the aesthetics of the future restoration.
Normal resorption of the jaw bone after tooth extraction
In order to avoid such unpleasant situations, after the atraumatic extraction of a tooth the socket is filled with a bone graft material. This graft will minimize bone resorption and will facilitate the formation of new bone in the socket.
The sinus is an airway cavity, like a balloon, located at the posterior region of the upper jaw.
If the distance from the ridge of the jaw until the maxillary sinus is big enough, then an implant can be placed.
Sometimes, though, after the extraction of a posterior tooth, the sinus begins to move downwards due to the absence of the tooth root. Hence, the sinus starts occupying the space of the jaw where the root was. Thus, the placement of an implant in this region may not be possible, because the penetration of the sinus by the implant is not desirable.
To resolve this problem, we resort to a surgical procedure called maxillary sinus elevation. During this surgery, the periodontist, after having gained access to the maxillary sinus, moves it upwards and fills the empty space with a bone graft. Thus, new bone is formed again in the region and the implant can now be placed. The elevation of the maxillary sinus is done under local anaesthesia. The minor discomfort that the patient may experience post-surgically is treated with mild pain killers.
Multiple teeth loss can lead to an extensive resorption of the jaw bone which may create large bone deficiencies. This alteration in bone dimensions may prevent implant placement or may induce aesthetic problems to the future restoration.
In these cases, the reconstruction of the jaw bone with bone grafts is necessary prior to implant placement. It is reasonable, that the more extensive the defect the more challenging the grafting procedure may become.