Are all synthetic bone grafting materials the same?
Absolutely not! There are a wide range of materials out there and they all stimulate different physiological reactions from the patient. I have been using synthetic materials exclusively in my practice for almost 20 years and have performed over 5,000 grafts with them – and I can tell you definitively that they are all different.
They have evolved too. Modern synthetic materials are often nothing like those that were on the market 20 years ago – the way they handle and perform have improved significantly.
In my opinion, the material which has been through the greatest evolution is Beta Tricalcium Phosphate (BTCP).
Beta Tricalcium Phosphate
Anyone who knows me will know that I’m a fan of BTCP, but it’s important to recognise that BTCP is not a commodity – different brands of the material are very different. There are many variables which can be altered depending on the manufacturing / sintering processes used. Research in the medical arena has taught us a lot about how surface area, porosity, particle size and particle shape can all be changed to produce widely different clinical results.
Using modern brands of the material makes a big difference – the performance is drastically different to the BTCP which was on the market years ago. Personally, I believe modern BTCP ticks almost all of the boxes of the ideal graft material. I mentioned in my last blog that it is widely used in medicine for its fully resorbable, osteo-conductive properties, and there is a large body of evidence showing that it can be osteo-inductive when used in orthopaedics and maxillofacial surgery (we are doing this research with dental materials at present, with encouraging initial results).
BTCP provides a fantastic environment to stimulate the body to do its’ own healing – I often refer to this as “upregulated host healing response”. I think this is the best outcome – as a dentist I want to do as little work, and as little surgery, as possible. If I can stimulate the body to do the work for me then that’s much better.
There are two notable limitations with BTCP though – it doesn’t have a mechanism to prevent soft tissue ingress and it isn’t particularly stable when used by itself. Traditionally you would tackle these issues by using a collagen membrane, but these bring a variety of concerns which I have also covered before.
These issues can both be overcome by using a material like Calcium Sulphate. It is a material that we are all familiar with, with a very long history in medicine, and something that we all know about it is that it hardens. This means that the graft will set in situ, creating a stable, cell-occlusive barrier which protects against soft tissue ingress. This effectively gives the graft a built-in membrane, removing the need for a separate collagen membrane.
So why don’t we use a graft which is 100% Calcium Sulphate? I’ve used them in the past and whilst they do set very hard and handle very well, in my experience they don’t have the same osteo-conductive properties of a material like BTCP. The Calcium Sulphate often resorbs within 3-4 weeks, too quickly to allow effective new bone formation.
I do all my grafting with EthOss® – a mixture of 65% BTCP and 35% Calcium Sulphate. This gives us the best of both worlds – we get the highly osteo-conductive BTCP, combined with the hardening properties of Calcium Sulphate, to give us an extremely effective, resorbable graft with great mechanical properties.
Using the two materials in combination also seems to give us the benefits of a staggered resorption rate. Sure, the Calcium Sulphate will absorb away faster than the BTCP (and I have many scans which prove this), but this can be a good thing. By having 35% of the graft begin to absorb away so quickly you are altering the porosity of the material at a critical time for the new bone formation, potentially opening up new pathways for angiogenesis and bone formation.
There are many other synthetic materials out there and it wouldn’t be fair to write this without mentioning some of them, particularly Hydroxyapatite (HA).
I’ve used many different versions of HA over the years and it is a completely different material to BTCP and Calcium Sulphate. Where both BTCP and Calcium Sulphate are completely absorbed, most forms of HA will not resorb and turn over into new host bone. It is more of a “filler” material that will stay in the graft site for a long time. Sure, it looks great on radiographs, but it isn’t inducing the same physiological response as a resorbable, osteo-conductive material. It comes back to a question of what result are you looking for – for me, the ideal end result is the patient having their own healthy bone with no foreign particles remaining in the site. Achieving this with HA is very difficult.
The last group of materials I would look at is polymers. I’ve used polymers in the past as well, but mainly as an adjunct to BTCP, in a similar way to how I use Calcium Sulphate now. They can work very well used like this, offering a hardening function that removes the need for a collagen membrane, but I often had concerns with the resorption rate. As the polymer component forms a barrier around the graft, until it absorbs it can restrict the blood supply to the BTCP and restrict the new bone formation. Polymers don’t seem to absorb in 3-4 weeks like Calcium Sulphate, in my experience they take a lot longer.
I am very comfortable with the materials I use now – it’s taken me a long time and thousands of grafts to find the options that work best for me, but something that I have learnt over time is that we have to trust the science. We know that different materials have different properties and produce different physiological reactions from the host.
I believe that the patients own bone, supporting an implant and naturally turning over, is the ideal outcome for any graft. Therefore we need to choose the materials that are most likely to give us this outcome and, for me, I don’t think there is presently any better option than a combination of BTCP and Calcium Sulphate.