The Clean Implant Project
Dental implants are an integral part of the therapeutic armamentarium of contemporary dental practices. With their excellent success rates, they have become the globally established treatment alternative to purely prosthetic solutions for tooth loss. And with the variety of implant systems offered, it has become ever more difficult for the dentist to choose just the right system for his or her practice and patients. Specific surface topographies, material properties that promote osseointegration or surface treatments are often emphasized in advertising as significant advantages to distinguish a given system from its many competitors.
It should be a matter of course that all dental implants when delivered in a sterile packaging are clean as surface pollution with organic particles or major inorganic residues originating from the production process are suspected to cause insufficient or missing osseointegration of dental implants. Unintended micrometre-scale particles may induce a foreign body reaction with a loss of bone in the early stages of osseointegration. In three consecutive studies since 2008 - realized in cooperation with the University of Cologne (Germany) and the Charité University Medicine Berlin (Germany) - scientists analysed the quality of dental implants by means of SEM/EDX.
Alarming Residues and Contaminants
In 2015 and 2016 extensive material contrast images were obtained and qualitative and quantitative elemental analyses were performed on 140 dental implants from 100 brands using the same study protocol. Surprising results of the recent study and a comparison with previous analyses showed an increasing spread of quality in the market.
Alarming residues and contaminants were found in the recent analysis e.g. iron, copper, chromium, nickel, silicon, sulfur and large quantities of stainless-steel particles, as well as remnants of polytetrafluorethylene and other major organic contaminations. All analysed implants – even implants with massive contaminants – carried a CE mark or passed other national regulations. All implants were sterile packed and ready to use for implant surgery – supposed to remain in the patients bone, at best, for a lifetime.
High Quality Implants
However, a major group of manufacturers and suppliers are able to offer high quality dental implants with no or only minor and isolated remnants on the micron level. See some examples of these implants in the gallery here...
The aim of this project is and will remain the documentation of the manufacturing quality of dental implants. So it is all the more gratifying that, as in previous years, development efforts at many manufacturers have paid off in the form of a further increase in product quality, such as the elimination of organic contaminants, more precise threads or more user-friendly sterile packaging.
Some manufacturers go one step further. They decided to apply for the CleanImplant quality mark in 2017 and undergo the comprehensive analysis and test procedure developed by the CleanImplant Foundation and it´s Scientific Advisory Board. Corresponding data will be published in the 4th quarter of 2017.
Particle-induced Macrophage Activation
But how does the human body handles with particles we could find on some implants containing tungsten, antimony, copper, tin, chromium and even nickel? Organic pollutions are in general considered as the contaminants with the strongest clinical impact such as early implant loss or peri-implantitis.
Even if these particles are relatively firmly attached to the implant surface, they are likely to become detached by the resulting frictional forces in the bone bed as the implants are inserted at torques in the double digits to achieve the desired level of primary stability. Particles with a diameter of less than 10 μm are susceptible to uptake by macrophages through phagocytosis, so that questions related to the clinical relevance of such impurities cannot simply be brushed aside. From orthopaedics it is known that particle-induced macrophage activation is associated with an increased osteoclastogenesis and may therefore cause increased bone resorption.
Our success rates are high, so what is the problem?
The manufacturers and users of implants which in the recent studies exhibited some organic contaminants report clinical success rates that do not differ from those of implants by other manufacturers. Statements such as “Our success rates are high, so what is the problem?” may be fully justified when discussing statistical average. But the question remains: What happens to those organic contaminants once in the bone? It is hard to imagine that those organic contaminants should have a positive influence on osseointegration. At best, there will be areas with a lack of osseointegration, i.e. smaller areas or entire outer thread edges with less bone contact, because the osteoblasts will have better things to do than to settle on polyethylene residue. Or macrophages cause phagocytosis of these materials during the first remodelling phase, which would amount to biological purification of industrially manufactured surfaces. What then becomes of the phagocytized materials is another question.
There is a probability that a certain amount of residue on implants can be tolerated in healthy patients. But can we be sure that this is also the case in immunocompromised high-risk patients? How about extended augmentation sites? And might not increased failure rates occur due to processing residue, after all? These questions, however, should actually not arise in the first place, because impurities are preventable, as this study clearly shows.
OK to use in patients – but apparently not always good enough to take a closer look
The great majority of manufacturers responded positively to the requests by the University of Cologne in 2015. Nevertheless, some manufacturers declared that they had no interest in this research. Not even the proclaimed fact that the present study did not primarily emphasize the producers’ interests but rather those of the users caused them to reconsider.
Especially noteworthy was the response from one manufacturer stating that one could not remember ever having received requests from users for SEM images or EDX results. Dentists, the statement continued, assumed that these results were good as a matter of course. Or else they were not interested in this information. And even if they were, they would not know how to interpret the data correctly anyway. All relevant information and a variety of studies on the requested implant system, they concluded, could be downloaded from the company’s website. In fact, the website offered no evidence on the safety of the chromium-nickel-steel particles that were found en masse in the analysis on an implant by that manufacturer.
Another manufacturer explicitly refused to participate in the study, but had later decided to fulfill the delivery of a sample implant in order not to boycott the study. However, the shipment contained an explicit note to the effect that the implant was not to be named in any publication related to the present study. We acknowledged that desire, but we did not want to deprive our implantological colleagues of the results. Because if the implants are good enough to be used in patients, they should be good enough to pass an SEM analysis.
Are we implantologists really not interested in the quality of the systems we use? Are we unable to evaluate the results of SEM analyses? Do some manufacturers have to “protect” us from scientific studies because we cannot interpret them correctly anyway?
Each day we are tasked with winning the trust of our patients, and each time we perform an implantological treatment we are trying to prove worthy of this trust. For individual manufacturers to reject quality assessments like the present one or to allege image manipulation is not particularly helpful in this endeavour. But the majority of the studied implants presents an encouraging picture. More and more manufacturers are aware of their responsibility and provide implantologists with solidly made clean implant systems.
However, we have to know, not believe, that a specific implant is without harm to our patients,
as Tomas Albrektsson already stated 10 years ago in 2007.