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Options for challenging situations

Major bone augmentations

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Nowadays, it is possible to place implants in patients experiencing considerable bone deficits – if appropriate surgical techniques are used and the patient’s circumstances permit.

Prof. Hendrik Terheyden | Germany

A proper bone augmentation before implant placement allows implants to be planned exactly in the prosthetic position with a correspondingly dedicated crown-bridge prosthesis – and thereby helps to avoid bi-directional planning with dimensionally reduced, angled or anchored implants in case of large bone deficiencies.


Augmentation techniques

Depending upon the defect type, inlay, interpositional, appositional and onlay osteoplasties can be used. The degree of surgical complexity grows correspondingly because it becomes increasingly complex to reliably cover the bone transplants with soft tissue and avoid a subsequent dehiscence.

The more difficult the defect class, the more active the bone transplant itself has to be. But beware that using autologous chips from a bone filter increases the chance for infection, necessitating a good antibacterial regimen and an antiseptic procedure. Bone scrapers or milling of cortical chips are a cleaner alternative source for autologous bone chips. 


Challenge: angiogenesis

Today it is not yet clinically predictable to provide vertical augmentation with blocks made of bone replacement material. This is in part due to angiogenesis, since vascularization occurs only a few vertical millimeters from the bone substrate. Biomaterial which is further than 3 to 4 mm away from the bone substrate tends to heal with scarring.


Sandwich technique and bone splitting

An internal bone defect presents the possibility for the good healing tendencies of inlay and interpositional osteoplasties (sandwich) with angiogenesis from all sides of the graft. Internal bone defects occur when, for example, a vertical defect is transformed into a sandwich osteoplasty by a horizontal osteotomy or when a horizontal defect is carried over into bone splitting.

A major advantage of sandwich-interpositional osteoplasties compared to appositional and onlay osteoplasties is that the soft tissue remains attached to the alveolar ridge and does not need to be shifted in a lingual direction. This facilitates soft tissue coverage, improves peri-implant tissue and reduces the likelihood of resorption. A modification of the sandwich osteoplasty is a swing interposition, which allows a ridge to be raised and broadened, if moderately atrophied knife-edge ridges are involved. 

Problem: transplant resorption

Free bone transplants – whether cancellous or cortical – can permanently heal only through internal bone resorption and subsequent replacement by new bone (“creeping substitution”). Whereas internal resorption of bone is necessary for the transformation, surface resorption on a larger scale is undesirable because it causes the augmentation material to loose volume and produces clinically unpredictable results. Thus, resorption occurs in about 40 percent of cases with large iliac bone transplants1, particularly early in the healing process.

To counteract this uncontrolled resorption, autologous bone blocks can be covered with Geistlich Bio-Oss® and Geistlich Bio-Gide®. Geistlich Bio-Oss® inhibits osteoclast precursor cells, while Geistlich Bio-Gide® forms a barrier against soft tissue ingrowth without inhibiting vascularization, which is crucial for new bone formation.2,3 Augmentation materials containing Geistlich Bio-Oss® exhibit volume preservation for many years.4

Long term prognosis

Implants in augmented bone have an excellent five-year survival rate, which is generally as good as native bone or over 95 percent.5 Cone beam computed ­tomography (CBCT) studies have provided excellent prospective proof of the constancy of volume with alveolar ridge augmentations both for bone blocks and for the membrane (GBR) technique over five years.6,7 Even major augmentations like Le Fort 1 interpositional osteoplasties exhibit an implant survival rate of 94.5 percent.8

The augmented volume remains stable over the long-term when implants are subjected to stress from chewing, as ten-year studies have shown.9,10 On the other hand, the augmentation is 100 percent resorbed if it does not undergo normal physiologic loading by teeth or implants.11

Prof. Hendrik Terheyden

Prof. Hendrik Terheyden | Germany

Clinic for Oral and Maxillo-Facial Surgery
Red Cross Hospital, Kassel

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