Research on implant complications has identified  two interesting facts :
1) complications appear to cluster around certain patients. In the past, studies have   reported complications almost exclusively on "implant level".  This means that if  screw loosening is reported with 30% prevalence in a patient sample, it is often mistakenly perceived as 30 patients out of 100 will experience screw loosening. The reality is however different and it became obvious when studies started to report on patient level. The percentage of patients with screw loosening was much smaller, but some patients experienced the problem multiple times.

2)  Patients with technical complications are 3 times more likely to have peri-implantitis as well. Don’t jump off your chair yet, this does not mean that a lose screw is the cause of peri-implantitis. but it does imply that there are certain common “predispositions” behind complications, no matter if they manifest as technical or biological problems.

In rehabilitation treatments, we usually say that maintenance is what you do before things break down and what you do after they break is "management of complications". But even this is not clear when it comes to implants. For example, how  frequently should an implant overdenture be  relined as part of expected maintenance and when an increased need of relining should be seen as “complication”?  Therefore, to define ,  report and understand complications we need to understand three key parametres:

a) Life expectancy
Fatigue of hard working metal parts is a reality since the Iron Age, which however the world of implants surprisingly overlooked. We accept that almost every functioning part of our car engine will be gradually replaced as the kilometer count increases. And although we would preemptively replace the clutch plate after 60,000 km, how long can a prosthetic screw last under an implant supported bridge? Would it make sense to replace it pre-emptively at some point? In reality,  we don’t really know. The way the data is reported on 5 and sometimes 10 year summative numbers, it is very difficult to see in detail how time in function affects mechanical problems .Peri-implantitis on the other hand is a different game: it is a disease, not a result of fatigue or time in function. As such, it is not inevitable.  Peri-implantitis is a complication of implant therapy no more than Periodontitis is a complication of having teeth! But we don’t call periodontitis a complication, right?

2. Conditions of use
This is in my mind the most important and underestimated parameter of the three. Complications will greatly depend on how we choose to use the implants. So what are the necessary conditions of use for implants? You place an implant in the bone, it osseointegrates, you make a crown, patient goes. Is this all?But what if you place an implant in a patient with periodontitis? Or a patient with deficient practice / understanding of oral hygiene? What if you place an implant in unfavorable prosthetic position resulting in an uncleanable prosthesis? In all the cases above, the implant is “predisposed” to trouble.  In the terminology of medical devices this would make the  implant used “off-label”. Problems will surface sooner or later and then we will pack it together in a summative number as complications. But how many of the implants reported in the literature with complications could actually have been “off-label”? For example, how many studies reporting prevalence of peri-implantitis also report how many of the prostheses were uncleanable? As of today, just a couple .  This fact might partly explain the wide range of prevalence found in different studies and environments. Complications will occur even when all conditions of use are met, but if we add on top the problems of implants that are predisposed, do we get a fair picture of the problem? Predisposing factors can also be technical. A series of recent studies  showed that even a small vertical misfit of 100μm has the potential to increase the risk of veneer chipping by multifold in small-medium span implant prostheses.  

3. Need of maintenance
Here we still have some work to do. As of today, maintenance protocols mainly focus on the peri-implant tissues, in most cases directly extrapolated from periodontal maintenance protocols, but there is a large gap in our understanding on how to maintain comprehensively, which includes the technical parts. How to examine the integrity of the prosthesis and all components? When to replace parts? How to identify “predispositions”? How to modify our maintenance protocols when we have compromised and predisposed situations? Now this is a great discussion, but it would take much more than this short article aspires to be…

 Complications of implant therapy is a true problem, and the causes are multiple. Adhering to correct design principles and maintenance can save us a lot of trouble, but will not eliminate trouble completely.  Very often when problems occur, there is a “predisposition” in the system, often due to known or unintended compromised decisions, designs or plans from our side. In the end, the only way to reduce complications remains the profound understanding of the biological and technical principles of Implant therapy, so the key is again, proper education. Finally, setting a baseline of correct understanding, where life expectancy, conditions of use and  regular maintenance are clearly communicated is crucial part of the treatment!