June 7, 2018

View from the dentists chair – how can you tell when a graft material is really working?

You might think there are some easy answers to this question!  Most of us will routinely look at radiographs and my Penguin ISQ device is a fantastic way of measuring stability, showing when the implant is ready for loading.

But when we conduct clinical studies neither of these options are really good enough – they don’t give us an accurate picture of what is happening physiologically within the graft site.  Look at this scan:

Wow – look at all that white!  That graft material must be working really well!

Unfortunately, it’s not that simple – this scan was taken 18 years after a procedure performed with a xenograft material.  Whilst the scan looks great, we know from experience that that this white area is not true host bone – there will be a significant amount of remnant graft material still in the site, many years after the procedure.

I don’t want this for my patients.  I want my patients to have the optimal outcome, which I believe is for them to have their own bone, naturally remodelling over time, hosting the implant.  We often hear about “osseointegration” of implants – for true osseointegration we need host bone.

When undertaking a study the only way to truly know what a graft material is doing is to take core samples and analyse them histologically.  This let’s us see exactly what is going on – including what type of tissue is forming, how much remnant graft material is still in the site and how much bone there is.

I’ve completed numerous studies where we have used histological analysis and seen hundreds of samples from different materials.  The differences between materials are consistently striking.  Have a look at the images below:

These images are taken from an ongoing animal study – they have not been published yet.  The image on the right shows a xenograft sample – sure, some new bone is forming, but you can see the xenograft particles are not being absorbed, and we all know from experience that they are going to stay in the graft site for a long time.  The alloplast (synthetic) on the other hand is being completely absorbed and will be replaced by host bone, as evidenced by the cell activity and bone contact around the BTCP particles.

We have taken this analysis a step further recently by developing a new software system which can analyse these samples, showing us the exact amount of new bone, graft material and connective tissue.

The above samples are from a socket grafting case, with the analysis done by the University of Freiburg.  The alloplast sample above (EthOss) has 48.12% new bone (red), and only 8.11% remnant graft material (blue).  These results are at 10 weeks.

The results are different because these two materials are doing different things.  As is often reported, the xenograft is providing a scaffold for new bone to grow around and encapsulate the bovine particles.  The synthetic is up-regulating the host healing response, encouraging new bone to grow as the material is absorbed.  It will usually be completely absorbed within 12 months, leaving healthy host bone to support the implant.

These findings aren’t revolutionary – there are hundreds of published papers in medicine showing BTCP to be a highly effective, osteo-inductive graft material.  There is a lot that dentistry can learn from looking at this science.  I would particularly encourage people to have a look through:

  • Yuan, H.; Fernandes, H.; Habibovic, P.; de Boer, J.; Barradas, A.M.; de Ruiter, A.; Walsh, W.R.; van Blitterswijk, C.A.; de Bruijn, J.D. Osteoinductive ceramics as a synthetic alternative to autologous bone grafting. Proc. Nat. Acad. Sci. USA. 2010, 107, 13614-13619.
  • Barradas, A.M.; Yuan, H.; van Blitterswijk, C.; Habibovic, P. Osteoinductive biomaterials: current knowledge of properties, experimental models and biological mechanisms. Europ. Cell. Mater. 2010, 21, 407-429.
  • Malhotra, A.; Habibovic, P. Calcium phosphates and angiogenesis: implications and advances for bone regeneration. Trends biotechnol. 2016, 34, 983-992.
  • Henkel, J.; Woodruff, M.A.; Epari, D.R.; Steck, R.; Glatt, V.; Dickinson, I.C.; Choong, P.F.; Schuetz, M.A.; Hutmacher. Bone regeneration based on tissue engineering conceptions – A 21st century perspective. Bone Res. 2013, 1, 216-248.

Our findings in dentistry are the same – the differing physiology of the jaw doesn’t seem to have much impact on the ability of these materials to help the body rapidly generate new bone.  Analysis of histology samples gives us conclusive proof of the efficacy of BTCP in dentistry – it’s time we all caught up with wider medicine!