Bei Minielevationen und Minirekonstruktionen über ein bis zwei Zähne, wird mit einer hohen Erfolgsrate gern Knochen-Ersatzmaterial, beispielsweise Bio-Oss® verwendet. Leider sind diese Knochenersatzmaterialien nicht knocheninduktiv, d.h. sie verursachen ihrerseits keine Knochenneubildung. Die Knochenersatzmaterialien sind im besten Fall knochenkonduktiv, d.h. sie werden durch einwachsenden Knochen langsam ersetzt. Und dies nur in den Abschnitten wo die Durchblutung günstig ist, d.h. in Kammnähe und in der Nähe der Kieferhöhlenschleimhaut, während in den Zwischenabschnitten das Knochenersatzmaterial unverändert im Bindegewebe liegen bleibt.

How is the patient’s own bone used?

The patient’s own bone is used in advanced atrophy for extensive ridge building (Cawood class IV to VI). At the beginning of pre-prosthetic surgery the patient’s own (autologous) bone from the rib was frequently used for building up the ridge. This method is considered obsolete nowadays, since resorption of this bone proceeds rapidly. The autologous bone material used most frequently is the pelvic iliac crest. Its bone marrow resorbs very quickly, the corticalis considerably less rapidly.
It is well known that the soft osteoporotic bone of elderly patients can be resorbed very quickly so that, despite bone augmentation, no implants can be placed since the bone has been resorbed after four to six months already

Are there disadvantages during the extraction of pelvic bone?

While rib bone is practically no long in use for augmentation in the jaw area, the iliac crest is still the most frequently used bone donor zone. Besides bone resorption that is not exactly predictable, pelvic crest demonstrates a particular disadvantage, namely, severe pain in the donor area over an extended period of time, and this often even with the extraction of just a little bone material, something like one by two centimetres
For extensive ridge reconstructions, however, bone sizes of circa six by three centimetres per jaw are needed, primarily then, when, for example, the upper jaw as well as the alveolar process is circularly augmented, since a sinus inlay and a nasal inlay must also be constructed.
Pelvic bone extractions lead to severe pain on movement, which can last for weeks and months and which, primarily for athletic patients and for those who have to climb the stairs, are extraordinarily unpleasant. Apart from the pain, the rate of complications at this extraction site is relatively high, as may be read about in the scientific literature.

And what are the advantages of calvarium bone?

Calvarium bone is definitely superior for larger jaw augmentations. In the process only the outer bone lamella is generally used. The advantages of this bone from the patient are multiple:
- Like jaw bone the bone is of so-called membranous origin – in contrast to all other bony materials, apart from the skull area, which develop via a cartilaginous intermediate stage and are altered only in established jaw bone.
- Calvarium bone is extremely hard and consists of practically only corticalis so that it is degraded only very slowly. Four to six months after an implantation there is hardly any resorption evident. For the most part, an implantation is still possible after ten to twelve months, which is seldom the case with iliac crest bone.
- A further great advantage is that the patients have scarcely any pain after the procedure and can move right after the operation. This is of particular significance for elderly patients, who become mobile only with difficulty after the iliac crest extraction and, for that reason, often remain hospitalised for a longer period of time.

And what do the scars look like?

A fine scar in the hair is the disadvantage of using calvarium bone. The hair is not removed during the operation. The hair itself is not removed in the area around the incision, as occurs with a face lift as well. With larger iliac crest extractions a broad, clearly visible scar develops and very often a deformation of the iliac crest rim, which bothers principally younger women (bikini wearers) a lot.

How does new bone formation function?

Für die Erhöhung und Verbreiterung der Kiefer kann der Schädeldachknochen in mehreren Schichten übereinander gelagert werden und mit Minischräubchen aus Titan oder resorbierbaren Schrauben (Inion) am Restkiefer fixiert werden. Für grosse Sinuselevationsplastiken, bei denen bis zur Hälfte der gesamten Kieferhöhle ausgefüllt wird, wird der Schädeldachknochen in Chips zerlegt.
For the elevation and broadening of the jaw the calvarium bone can be laid down in several layers atop one another and fixed to the rest of the jaw with mini screws made of titanium or reabsorbable (Inion) screws. For large sinus elevation plastic surgeries, in which up to half of the jaw cavity must be filled, the calvarium bone is cut into chips.
Recently we have been covering the bony depression in the fossa canina with a special third-generation (JNION®) membrane, which is not only reabsorbable and becomes rigid within several minutes of placement but, at the same time, is also bone inductive, that means, actively stimulates new bone formation. That happens thanks to NMP (N-methyl-2-pyrrolidone).
As animal trials have shown, the new bone formation is even superior to that from BMP. We use the same membrane in critical load zones, for example, where two bone transplants abut and a depression or a connective tissue infiltration could possibly occur. In the same way we use this membrane in those cases where we have extracted bicortical bone in the chin area for small augmentations and must anticipate a complete ossification at the extraction site, for example, with regard to later placement of implants in the interforaminal region.

Are there proven successes?

Of the 89 larger ridge augmentation and sinus inlays carried out to date we have seen at the second operation, the placement of dental implants, significant resorption of the calvarium bone in only one case; nevertheless, the placement of implants was not jeopardised. Only once did we lose a piece of transplant because of a disturbance of wound-healing.

It should also be mentioned that calvarium bone can also be used for advanced osteoporosis of the skeletal system. Calvarium bone, which is of membranous origin, as is well known, appears to be affected significantly less by osteoporosis than the bones of the rest of the skeletal system which develop from a cartilaginous base.