Dental implants play the part of artificial tooth roots and are fitted to the bone of the upper or lower jaw.
To ensure that a prosthesis is firmly in place, implants must be fixed to a sufficient amount of bone. When the bone does not have enough volume, it can be surgically raised by means of a bone graft.
Diagnosis
The amount of bone available for fitting implants is measured using 3D imaging techniques (scan) thanks to which we can calculate the height, thickness and quality of the bone available in the area where the implant is to be fitted.
These images also enable us to ensure that no obstacles will get in the way of fitting the implant, such as leftover pieces of root, small cysts, etc.
Surgical technique
There are different types of bone grafts. Depending on the type of graft applied, the operation can be carried out in the surgery or at a clinic, with either local or general anaesthetic.
In any event, the operation is carried out in surgical and completely germ-free conditions.
We can generally distinguish between two types of bone grafts:
Autologous grafts: the bone is taken from the person to receive the graft. Normally the bone is taken from either the lower or the upper jaw, close to the area to be grafted. For larger grafts, bone can be taken from the cranial vault or from the iliac crest.
Non-autologous grafts: in this case, the lack of bone can be overcome using different kinds of synthetic material. This material is treated using a series of processes to guarantee a very high standard of safety in their use.
Bone Regeneration or Augmentation techniques:
- Urban Technique
- Khoury Technique
- Alveolar Ridge Split
Urban technique. This technique, also known as the “Sausage Technique”, created by the Hungarian, Dr Urban, is used in the rear part of the jaw, when there is insufficient bone height to fit several implants. It involves vertical bone regeneration.
Here the gum is opened and well separated, leaving a flap to surround the material placed under it in sausage shape. The implants are fitted, leaving two or three threads exposed. These threads are surrounded with bone dust taken with a curved scraper from the area furthest back and to the side of the patient’s jaw, adding a pellet of growth factors with biomaterial.
A long duration membrane is added and tacked in place, just like a tent, where the pegs would be the implants. The next layer is a fibrin membrane, over which the gum is stretched and sewn. The implants must remain in place for 9 months with no load, i.e. without fitting the crowns or using removable dentures to eat. The patient may experience a certain feeling of paraesthesia or tingling for a time. This is a complex and laborious technique which we try to avoid by using very short implants.
Khoury technique. This is a 3D bone regeneration technique created by Dr Khoury from Münster University for cases where we want to augment the height and width of bone at the rear of the jaw in order to fit several implants. A square lamina of bone is taken from the patient, from the exterior of the gonial angle. This lamina, measuring several millimetres, is sagittally divided into two, giving us two square laminas of bone.
These laminas are used to create a formwork for the particulated bone: the two laminas are screwed onto the outside part of the two bone walls of the socket into which we want to place the implants, higher than said walls. Between the laminas, we will place regeneration material, normally a mixture of autogenous bone obtained by scraping the bone, together with biomaterial containing growth factors. After waiting for 6 months to a year, the socket is re-opened, and the implants are fitted. This technique is used in the event of being unable to fit very short implants.
Alveolar ridge split. This is a more common procedure, used above all on the jaw when there is sufficient bone height, but the bone ridge is too narrow to take one or more implants. Having opened the gum, a sagittal incision is made in the bone ridge, with mesial and distal discharges which are neither too long nor too deep. This technique is similar to opening a horizontal bread roll to take one or several vertical hot dogs.
Increasingly wider expanders are gradually placed between the two half-open laminas to create the split to take the implants. Growth factors are used to fill the space between the implants. The external lamina, the one that moves, is connected to the interior lamina, which is held in place, with two screws. The whole area is surrounded with a fibrin membrane containing bone particles obtained by reaming. It is important not to stretch the gum too tightly when sewing. We must then wait for 6 months to a year for completion of the implant osseointegration process.
Evolution
The effects of a bone graft depend on its nature and extension. As with any surgical operation, bone grafts made prior to an implant are followed by a healing period during which the patient may experience pain, swelling, and, in very rare cases, some kind of complication.
To ensure that this healing period proceeds in the very best of conditions, the patient is issued with a prescription indicating the medicine they must take and the instructions they must follow.
Summing up
The bone volume available in the area of the upper or lower molars is often insufficient for fitting a dental implant. Bone grafts allow us to increase that volume.
The graft can be made in the surgery or at a clinic, with local or general anaesthetic.
