Richard McGowan reports back from Dr Schlee’s lecture on Botiss Maxgraft bonebuilder, a three-dimensional milled human bone graft.

In December 2015, Straumann and Botiss were proud to host a lecture for key clinicians across Western Europe by Dr Markus Schlee, a periodontist and implant dentist working in private practice in Forchheim, Germany. Dr Schlee presented the theory and practice of using Maxgraft bonebuilder, a threedimensional milled human bone graft. Dr Schlee has been involved with the Maxgraft bonebuilder product since its inception in 2004.

What is Maxgraft bonebuilder?bonebuilder computer graphic

Maxgraft bonebuilder is a pre-fabricated allogenic bone block, individually designed for a patient’s bone defect using CT/CBCT scans and three-dimensional planning software. The block is designed by Botiss technicians and reviewed by the clinician before being milled, ready for insertion into the defect. The product has been commercially available since 2011. The maximum block size is 38 x 13 x 13mm, and delivery time is four to five weeks from submission of the CT/CBCT scan, with the design stage taking up only two or three days. Dr Schlee began his lecture by reviewing the most common method for regenerating large bone defects: autograft bone blocks. Although the use of autograft bone is well accepted, it is not without its drawbacks, and adoption is no guarantee of success in regenerating vital bone. He postulated that there are cases where, some years later, dead bone persists, and can lead to peri-implantitis. Harvesting autograft bone can be problematic, with potentially severe postoperative complications. Intraoral sites risk nerve damage, due to the complicated anatomical structure, particularly in the ramus and chin (where Dr Schlee quoted the incidence of paraesthesia at around 10% of cases). Alternative extraoral locations, such as hip grafts, can harvest greater quantities of bone, but pose a fracture risk (Dr Schlee quoted 1:250), and have published post surgical complication rates of between nine percent and 30%.bonebuilder computer graphic2

Challenging the autograft orthodoxy

Although there are many published studies comparing different bone grafting techniques, Dr Schlee reviewed the Esposito study of 2009, which reviewed many papers comparing different bone grafting techniques – yet only 13 were rigorous enough for consideration (Esposito et al, 2009). The study concluded that some bone substitutes could be a preferable alternative to autograft bone, that complications are common, and that short implants appear to be a better alternative to vertical bone grafting of resorbed mandibles The use of autograft bone substitutes varies from country to country and is often dependant on regulatory and/or cultural reasons. For example, the use of cadaverous allograft bone is commonplace in the USA and fresh frozen allograft bone is used by others (but risks disease transmission). The situation in the UK is different, being historically dominated by xenograft, but the adoption of allograft is increasing. UK clinicians now have access to demineralised, freeze-dried allograft bone from cadaverous donors, or, as in the case with Maxgraft bonebuilder and almost all Botiss Maxgraft lines, live donors (total hip replacement patients).

Allogenic bone 

bonebuilderThe use of any allograft bone requires careful donor selection. In the case of bonebuilder, the donors are asked about their medical and sexual histories, in addition to serological testing. This screening process leads to the exclusion of roughly a third of donors on safety grounds. As allograft bone is freeze-dried, and not heat-treated (as with xenograft), the native collagen remains bioavailable, so can aid the healing process, as it does in autograft bone. As the speed of wound healing slows with age, patient age should therefore be a consideration when it comes to selecting the type of bone graft. When compared to standardised block allografts, Dr Schlee felt the pre-milled Maxgraft bonebuilder blocks had some handling advantages, namely:

• There was no need to rehydrate (as with some other blocks)
• It is quicker
• The preformed shaped means the sterility of the block is maintained better than blocks requiring adaptation (where standard blocks pick up saliva during repeated try ins
as fit is adjusted).

Bone resorption

The floor was then opened up, where allogenic bone resorption was questioned. The protocol states that a bonebuilder site should be left for six months to heal. In reviewing 35 patients after six months, Dr Schlee found that the average resorption was 0.51mm, meaning there is no need to over augment a bonebuilder site. He stated that a similar longer-term study had backed this data up. However, he noted that a few patients (three out of 35) had higher resorption (over 2.5mm). Such severe resorption of the graft may be connected with other medical complications (such as diabetes), or other unknown factors. He then described one case with a 20-yearold woman in whom the first autograft fully resorbed very quickly, the graft was repeated and the same happened again. However, he felt that experiences such as this were unusual enough to not cause any significant challenges to his clinical practice.

Grafting in particularly challenging sites

In wide bone grafting defects, the size of a Maxgraft bonebuilder block is limited by the size of donor femur heads, which restricts a maximum block length of 38mm. If the defect is larger, Dr Schlee explained that he uses one block, trimmed at each end, to create two contained defects that can then be filled with particulate bone, or in especially large defects, he will use two blocks with a 5mm gap in between, filled with particulate bone. In contrast to denser blocks, the soft cancellous bone that the bonebuilder is made from means there is no need to over-drill the fixation screw holes; the screw can engage into the block. Block breakages appear to be rare (in his 11 years with the technology, Dr Schlee has only ever had three break), but should they happen, his solution is simply ‘to use an extra screw’.

The importance of soft tissue management

As with all bone grafts, soft tissue management and flap design is critical to success. This is just as important in a bonebuilder case, as if sutures are too tight you risk exposure. In particular, with a bonebuilder case, clinicians need to take the soft tissue biotype of the patient into consideration to ensure tension-free closure.The design created by Botiss is done without this knowledge, as soft tissue data is not included in CT/CBCT scans. The lecture was well received by the delegates in attendance, and while the technology is new to many in the UK, it has the potential to make a positive impact on the surgical techniques of clinicians nationwide.

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