What first comes to mind when you think about dental implant surface?

Implant surface roughness?

Topography?

The shape of the body and threads?

If you have considered implant surface, you may well have been absorbed in the surface-roughness topic for many years. Roughness is, after all, a key factor in the rate of osseointegration. 1

But now it is time to go deeper. Look beyond geometry and topography to discover that chemistry really counts. If you love science and technology, this is a fascinating field that impacts your day-to-day life – and that includes the chemical characteristics of the dental implants you use for successful implant treatment, and ultimately to make your patients’ lives better.

Here are three interesting things you should know about surface chemistry, in dentistry and beyond.

Surface chemistry decides chemical reactions – including with implants

Put simply, the surface chemistry is the surface’s chemical composition. Think of a material’s surface as a ‘frontier’ of atoms, which meets the atoms of another material. The surface chemistry decides which chemical reactions will take place at the interface with other molecules (solid, liquid or gas).2

So, in the case of dental implants, it defines the chemical reaction that takes place between the implant surface and the cells and proteins.

Will the surface adsorb, absorb, or desorb the other substance?

Will there be a hydrophilic or hydrophobic layer?

Will it crystalize? Catalyze? Will the dental implant surface and abutment surface form chemical bonds with proteins? The surface chemistry will decide.

Surface chemistry is interesting. But what’s exciting is when this knowledge is applied; when technology takes control of surface chemistry and takes advantage of chemical reactions, and when we can apply this knowledge to for achieve high clinical results.

Surface chemistry matters, from day-to-day objects, to space travel, to dental treatment

Let’s put surface chemistry in context. This is not just a niche specialism for implantology – you will see that chemistry counts in a whole plethora of technologies, industries and manufacturing. Just a few examples include:

Teflon™ – Teflon (Polytetrafluoroethylene) has a chain of bonds between carbon and fluorine atoms that are so strong, it is difficult for other atoms to bond with the surface.3 Best-known for non-stick pans, it gained real fame when used as a protective material for space suits on the Apollo mission. You may also have medical devices and surgical instruments that use it as a protective layer.

Catalytic converters – In your car, the surface of the catalytic converter is covered with catalysts which, when in contact with exhaust fumes, causes oxidization of carbon monoxide and hydrocarbons and reduce nitrogen oxide. 4

Semiconductor-based technology – The microchips in your phone, computer – and pretty much every digital device – contain millions of transistors created with complex chemical processes including chemical vapor deposition, crystallization, and etching.5

The list of surface-chemistry applications goes on and on. But why does this matter for dental implants and abutments?

For tissue integration with an implant, surface chemistry counts

In essence, the implant surface’s chemical composition triggers its reaction with cells and proteins.

Of course, different molecular functional groups react in different ways – they might encourage tissue integration, or they might inhibit it. For a medical device where protein adhesion should be avoided, it may have a surface in the form of a hydrophobic layer.But if you want to place a dental implant, you need a chemical reaction that creates attachment points for bone and soft tissue.6

One way to alter the chemical composition of the dental implant surface is anodization. In case you’re not familiar with the anodization process, the titanium implant is submerged in an electrolyte fluid, and an electric current is passed through it. This increases the thickness of the titanium oxide layer and changes the topography. 7 If particular molecules are added to this electrolyte fluid, they can attach to the oxide and change the surface chemistry, defining which chemical reactions take place when the surface meets the tissue.8 Particular elements have been associated with improved biological performance of metallic surfaces. 9, 10, 11

An important feature is the presence of hydroxyl groups (OH) on the surface, which are proven to promote osseointegration and bone formation. More hydroxyl groups on the surface mean more attachment points for the fibrinogen that causes blood clots, and research has found that, when compared to sand-blasted and acid-etched implants, anodized surfaces have the most hydroxyl groups12.

Another chemical property of the surface that can impact tissue integration is its hydrophilicity. The ability of cells to attach to the surface is driven by protein adsorption,13 and many studies have shown that hydrophilic surfaces tend to have better attachment to proteins than hydrophobic surfaces. 14

Looking to the future

For decades, surface topography has dominated implant surface debate. But as the wider discipline of surface chemistry grows, along with its multitude of practical applications, the ability to influence surface at a molecular level could be embraced for dental implant systems. Anyone looking for more ways to promote and achieve fast tissue integration – both for bone and soft tissue – should take surface chemistry into account.

References

  1. Bauer S, Schmuki A, von der Mark K, Park J, Engineering biocompatible implant surfaces Part I: Materials and surfaces, Progress in Materials Science 58 (2013) 261–326
  2. Gabor A.S, Y. L. (2011, January 18). Impact of surface chemistry. PNAS, 108(3), pp. 917-924
  3. Tzoraki O, Lasithiotakis M Environmental Risks Associated with Waste Electrical and Electronic Equipment Recycling Plants Reference Module in Earth Systems and Environmental Sciences, 2018 https://doi.org/10.1016/B978-0-12-409548-9.10980-7
  4. Taylor K.C. (1984) Automobile Catalytic Converters. In: Anderson J.R., Boudart M. (eds) Catalysis. Catalysis (Science and Technology), vol 5. Springer, Berlin, Heidelberg doi: https://doi.org/10.1007/978-3-642-93247-2_2
  5. Gabor A.S, Y. L. (2011, January 18). Impact of surface chemistry. PNAS, 108(3), pp. 917-924
  6. Bauer S, Schmuki A, von der Mark K, Park J, Engineering biocompatible implant surfaces Part I: Materials and surfaces, Progress in Materials Science 58 (2013) 261–326
  7. Bauer S, Schmuki A, von der Mark K, Park J, Engineering biocompatible implant surfaces Part I: Materials and surfaces, Progress in Materials Science 58 (2013) 261–326
  8. Bauer S, Schmuki A, von der Mark K, Park J, Engineering biocompatible implant surfaces Part I: Materials and surfaces, Progress in Materials Science 58 (2013) 261–326
  9. Zhang BG, Myers DE, Wallace GG, Brandt M, Choong PF. Bioactive coatings for orthopaedic implants-recent trends in development of implant coatings. Int J Mol Sci 2014; 15: 11878-11921
  10. Park J-W, Kim Y-J, Jang J-H, Kwon T-G, Bae Y-C, Suh J-Y. Effects of phosphoric acid treatment of titanium surfaces on surface properties, osteoblast response and removal of torque forces. Acta Biomaterialia 2010; 6: 1661-1670.
  11. Park J-W, Kim Y-J, Jang J-H. Enhanced osteoblast response to hydrophilic strontium and/or phosphate ions-incorporated titanium oxide surfaces. Clinical Oral Implants Research 2010; 21: 398-408
  12. Smeets R, Stadlinger B, Schwarz F, Beck-Broichsitter B, Jung O, Precht C, Kloss F, Gröbe A, Heiland M, Ebker T, Impact of Dental Implant Surface Modifications on Osseointegration, BioMed Research International, vol. 2016, Article ID 6285620, 16 pages, 2016. https://doi.org/10.1155/2016/6285620.
  13. Smeets R, Stadlinger B, Schwarz F, Beck-Broichsitter B, Jung O, Precht C, Kloss F, Gröbe A, Heiland M, Ebker T, Impact of Dental Implant Surface Modifications on Osseointegration, BioMed Research International, vol. 2016, Article ID 6285620, 16 pages, 2016. https://doi.org/10.1155/2016/6285620.
  14. Bauer S, Schmuki A, von der Mark K, Park J, Engineering biocompatible implant surfaces Part I: Materials and surfaces, Progress in Materials Science 58 (2013) 261–326

Posted by Chris Kendall