If at time of diagnosis, it was determined that there isn’t enough bone available to anchor any implants, the first step would be an augmentation (bone graft). There are various methods for bone augmentation, which widely differ in effort, complexity and also cost.
We distinguish unilateral augmentation (i.e. bone grafting and implantation in one step) from bilateral augmentation (i.e. bone graft comes first, implantation happens after 3-4 months).
Bone material and methods
Bone graft with autologous bone meal and / or synthetic bone substitute material.
During the surgery for bone deficiency, required bone for a later reconstruction can be gathered. By using a drill, bone meal is being produced. In addition, own bone material can also be blended with artificial bone material.
A sinus lift is a special form of bone formation. After bone loss, the bone height in the maxillary posterior area, is oftentimes too low for anchoring implants with sufficient length. By embedding bone or bone grafting material into the maxillary sinus floor it will be "lifted", so implants can be securely anchored.
During an external sinus lift, a bone window bone window between the oral cavity and the maxillary sinus will be created, and via this window the maxillary sinus mucosa / periosteum will be detached from the bottom of the maxillary sinus (comparable to the inner skin of an egg). Bone i.e. bone grafting material will be applied to this cavity.
During an internal sinus lift, bone will be pressed below the membrane lining of the maxillary sinus, which allows for the the usage of longer implants.
If the jaw portion is too narrow or too low, a bone piece from a different location of the jaw may be secured by screws at the desired location.
This bone block requires several months to heal, before it is strong enough for implants.
Bone expansion (splitting)
For jaws that are too narrow, it is possible to prepare the bone for implants by bone expansion. With this proven technique the narrow bone will be split into a lip-sided and tongue-sided sheet, using a special micro-saw. After that, implants will be mounted into the resulting gap and the remaining holes are filled with bone substitute material.
Another method uses expanding, not abrasive drills in ascending sizes to make room for the implants in the narrow bone.
Distraction / osteodistraction ("bone formation by pulling apart")
With this method, a bone that’s too low will be split into an upper and lower portion. A special bone screw is applied to these bone parts, which allowed for gradual lifting of the upper bone clip (about 1 mm per day), by utilizing the body’s own bone fracture healing process in order to create new bone (callus).
For this purpose, however, the distraction device must be worn inside the mouth for a few weeks. The reward is about 10 mm new bone height gained within 12 weeks. Another advantage: even soft tissue can be stretched this way.
Horizontally splitosteotomy (HGSO) represents a surgical bone construction method, which in special clinical cases should be preferred the classic technique of open sinus lift. The method was developed by our practice and presented for the first time at the Aannual Congress of Oral and Maxillofacial surgeons, in St. Anton am Arlberg (2010) (for more information, read the PDF of the program).
In general, a bone atrophy of the maxilla is not only associated with a reduction of bone width, but also in vertical dimension. As a consequence the classic bone regeneration technique of open sinus lift is ignoring the vertical dimension of the bone atrophy, resulting in crowns that are very long.
Applying the HGSO method, the trauma to the maxillary sinus is significantly reduced and the actual atrophy of the jaw (vertical shrinkage by a down-shifting of mucosa and bone) will be restored.
The resulting space between the maxillary sinus and the mucus that had shifted downwards, allows the formation of the bone in the area where the teeth used to be.
Due to the lack of injury of the sinus structures, this technique is far less traumatic for the patient than the open sinus lift technique. For better understanding, please view the schematic drawings of this technology above.