Digital dentistry and new technologies geek. I can quote Star Wars better than you and your friends.
Latest posts by Francisco T. Barbosa (see all)
- 3 Reasons Why High Implant Insertion Torque Backfires - May 15, 2017
- Some Concepts We Should Know About Implant Surfaces Topography - January 16, 2017
Once, someone in a discussion about implant surfaces on a Facebook group came up with the sentence: “I use an implant system with a very rough surface. This feature makes my system slightly better than yours”.
Well, fortunately, this answer was not for me. It was a discussion between two dentists inside the topic “early loading” and “implant surfaces”.
We could think that this sentence makes sense, cause the rougher the surface is, the most initial interaction with proteins and cells (Berglundh 2003).
And I wanted to check what was the opinion of other dentists and I did a poll on Twitter:
How would you consider the the topography of your favorite implant system?🤓
— Francisco T. Barbosa (@Cisco_research) November 29, 2016
The other “trending” sentence is: “all the implant surfaces work well.” And it´s true. They all get osseointegrated, except when they don´t.
Yes, maybe, like everything in life: “The faster, the stronger, the bigger” and why not, “the rougher” are always the best.
But this sentence is false.
And following I´m going explain to you why.
What should I know about the surface topography of the implant system that I´m currently using?
Wenneberg proved that Microstructured implant surfaces show advantageous characteristics for bone formation and are the current standard of surface treatment (Wenneberg 2009).
Inside this characteristics we should know the following:
- Surface topography
- Surface chemistry
- Surface charge and wettability
In this article, we are going to focus on the surface topography.
A lot of parameters can be used to measure the surface topography.
I will analyze the surfaces based on two parameters that are the most commonly used:
- Ra- This is the most common height-descriptive two-dimensional parameter.
- Sa- The same than Ra but in a three-dimensional measurement.
Almost all the articles consider this two parameters to describe the topography of an implant.
Wenneberg & Albrektsson (2004) classified the different surfaces depending on these values as:
- Sa value 0.5 µm- Smooth surfaces.
- Sa value 0.5–1 µm- Minimally rough surfaces.
- Sa value 1–2 µm- Moderately rough surfaces.
- Sa value >2µm- Rough surfaces.
And there are different techniques to change the surface topography. We should consider this two groups:
#1. Subtractive techniques
– Mechanical polishing
2#. Additive techniques
– Hydroxylapatite (HA) and other Calcium phosphate coatings.
– Titanium plasma-sprayed (TPS) surfaces.
– Ion deposition
When we go back to the scientific literature, there is a broad range of different Sa/Ra values among the scientific publications.
Of course, this variation depends on which technique was used to change the surface topography.
Let´s talk about some of them, so we can conclude which can be a right choice for our daily practice:
#1. Blasted implant Surfaces
Some blasted surfaces have been reported to have an optimal bone-implant contact and higher removal torque than turned surfaces.
The optimal Sa value in a blasted surface was found to be 1.5 µm (Wenneberg 1998).
There are a lot of publications comparing blasted surfaces with turned surfaces, and in animal studies, the finding is that blasted have better bone integration.
In contrast, clinical studies failed to prove these results (Karlsson 1998).
Of course, it´s not easy to seduce a patient to remove him/her their implant just to check the removal torque or to make a histology.
Here you can see the video where an implant is being blasted:
In this group is where we can find the scientific literature that proves that more rugosity values don´t mean better biological integration.
I could mention several studies where this was stated, but I´m going to flag the pre-clinical trial in rabbits that compared different surfaces (Cordioli 2000):
- Machined with a Sa value of 0.29 µm
- Acid-etched with a Sa value of 0.62 µm
- Blasted with a Sa value of 1.26 µm
- TPS surfaces with a Sa value of 9.10 µm
Guess who had the higher removal torque?
Yes. You named it: Acid etched with only a Sa value of 0,62 was the winner.
Of course, there are other studies with the same results, but I just wanted to give you an example to prove you that more rough surface doesn’t mean higher removal torque or even more bone-implant contact (BIC).
When we dive into clinical trials with etched surfaces, some points are important to remark:
– Periodontal pathogens were founded in failed implants independently of the surface topography (Shibli 2007).
– The success rate in dual-etched implants is higher than in turned implants (Khang 2001), although there are not major differences.
– Etched surfaces have better osseointegration than turned/machined surfaces in animals. Quite difficult to prove this in humans cause we would need to push out the implant to check the removal torque, or perform a histology.
#3. Blasted+etched surfaces
This technique is the most investigated for creating a micro-rough surface topography (SLA surface. I´m sure you heard about it a lot of times).
The acronym “SLA” reminds me how often sales representatives come to my dental office showing me a “new implant” with a surface that is similar to the “SLA surface from Straumann.”
They always say the same story:
– “Did you know that two engineers escaped from Straumann facilities and they developed this implant surface that is similar to the Straumann SLA?” is often their argument to try to persuade me to buy their system.
Of course, I can´t believe that two engineers “escaped,” as long as I know, Straumann facilities are not a jail. And if this was true, Straumann must have a building with 30 floors underground to store all that amount of engineers.
Last year I received at least 10 sales representatives arguing that they have in their company two or three “escaped Straumann engineers” developing the same SLA surface to their implant system.
You can make the numbers: 10×3= +/- 30 “escaped engineers!!!!!”
If I were the Straumann CEO, I would put the headquarters at Alcatraz to avoid more deserter employees.
But let’s get serious again.
This two subtractive techniques can be combined to increase the roughness and to smooth sharp peaks after the blasting process.
Also, this can increase the surface frequency which is something important to promote the initial adhesion of proteins and help the early bone-healing process.
Also, it was investigated the influence of the SLA surfaces on the human mesenchymal progenitor cells (HMPC), and it was stated that SLA surfaces promote osteogenic differentiation of HMPC.
And what does that means?
Implies that SLA surfaces are more osteoconductive compared with smoother surfaces we can expect enhanced bone-implant integration, which leads to more bone-implant contact (BIC) and increased removal torque values (Davies 2003).
From a clinical point of view, this is an advantage cause healing period is reduced compared with turned and machined surfaces, and implants can be successfully loaded 6-8 weeks after implant placement.
Reducing the healing time also decreases the risk due to patient interference.
I have to mention that I mainly use a system with a sandblasted and double etched treatment (along with a thermal treatment as well). Some of the characteristics of this surface, Avantblast®, is that it has an SA value of 1,23 µm.
In this chart below you can see the average Sa values for some of the most popular surfaces in the market (Rodríguez Rius 2005, Dohan Ehrenfest 2011).
Maybe with the name “oxidation,” you cannot tell which implant brand is using this kind of treatment, but if I mention “TiUnite®” I’m sure that rings a bell with you.
Oxidation may not sound good to be present in a fixture that is going to be placed in a human being, but all the implants have a native oxide layer.
The oxidation process that can be produced by a thermal treatment or by placing the implant in a galvanic cell increase that native oxide layer (it goes from a native oxide layer of 5 nm to a 1 mm thicker layer).
The Sa values for an oxidized surface are ranging from a 1,17µm (Ivanoff 2003) to 1,35µm (Sul 2006).
There is a remarkable study where the authors placed implants with the same geometry but comparing implants with turned surface with implants with an oxidized surface in immediate loading cases.
The authors found a significantly higher success rate for the implants with the oxidized surface (Rocci 2003).
In this classification, TPS are the most famous.
Titanium particles are applied on implant surfaces with a plasma spraying technique that creates an irregular topography on the implant.
This process creates a very rough surface, really rough: 4-5 µm (Wenneberg 2009).
It would be logic to say that the TPS surfaces are the best, but clinical investigation proved that this is not true:
– They have a more marginal bone loss (Becker 2000).
– More failure rate, especially in periodontally susceptible patients with a smoking habit (De Boever 2009).
#2. Hydroxylapatite (HA) and other Calcium phosphate coatings
Likewise the TPS surface, these HA coated surfaces have a highly rough surface.
They were proven to be bioactive and to promote osteogenesis. In the short term.
It was associated with a multinucleated giant cell activity in the proximity of the implant which leads to bone resorption.
They are not recommended anymore.
After going through the surface characterisation of every technique to change surface topography, we can conclude these takeaways:
– Most of the commercially available surfaces seek for a Sa value between 1-2 µm, which means a moderately rough surface. Check the SA value of the implant brand you are using. If the implant system doesn´t have a feasible study about its surface, switch to a more reliable commercially available brand (not joking).
– Is important to know whether the implant system we are using is validated to perform early loading. This feature mainly depends on the surface characteristics. Macro geometry may have a direct impact also on the healing time (Berglundh 2003, Abrahamsson 2004) as it was pointed to me by Daniel Rodrigo while I was writing this article.
– The majority of commercially available surfaces promote a proper osseointegration even if primary stability is not achieved during the surgery (Rodrigo 2010).
– Animals studies showed that there is an inevitable progression of the peri-implantitis in implants with anodized (Tiunite®) surfaces. Furthermore, the outcome of peri-implantitis therapy is influenced by implant surface characteristics (Albouy 2011, Mellado-Valero 2013).
Other questions remain unanswered:
– What is the impact of the implant surface topography on the survival rate?
– What is the relation between the macro geometry and the surface topography?
This issues may be more critical in short implants, where the marginal bone must be preserved at all cost (is not the same having 2 mm of marginal bone loss in a 13 mm length implant and a 6 mm implant.
These are some of the questions that came up in a conversation with an expert in implant dentistry, David Valero.
What is your opinion? Are we going back to the past and start using turned implants?