Indications for platform switching?

Platform switching was discovered almost as a serendipity. When the correct diameter component was not available, an abutment with a smaller diameter than the implant platform was placed into an implant and left there for a time. The gingival and bone reaction was better than expected and the typical “Biologic Height Bone Recession” about the implants was less than usual. This was in the days before most implants were rough surfaced. Most implants had a smooth machined collar and were then“threaded” below the collar. Bone recession about the collar typically extended down to the first or second thread. All sorts of ways were tried out to prevent this bone recession. These included bringing the threads right up to the surface, micro threads, various forms of texturing (often of less roughness than on the implant body). To confuse the situation even more, systems were developed which combined several of these. For example, it’s now common to see rough surfaces combined with platform switching. Many explanations for these benefits were touted and dentists have been led to believe that some systems are better than other. One would hope that all these systems were thoroughly tested out and that long term survival data was now available, but rarely is this the case. There were several other factors to take into consideration. With the older conical implant connections the final restorations were always bought down over the abutment to fit the implant platform. This was necessary because conical connections inherently have a greater vertical discrepancy than flat platform systems. Now with modern conical systems, most of which are “Bone Level“ the final restorations are fit to the abutment. It’s easier and better fitting, though obviously with inherent “Platform Switching”. Unfortunately then, trends gets inter-mixed with expedience and philosophy to become a standard. These days many think that Platform Switching is the way we should be doing things. However, this concept does put more strains on the connection, can make it difficult to maintain clensability in the gingival to subgingival region and makes it difficult to probe the implant region. With rough surfaces extending up and sometimes on to the implant platform then contamination of the region may mean that while peri-implantitis may be delayed, it still has a chance to ruin a final result.

Nice outline Peter. You are exactly correct that there now seems to be less “long term survival rate” research data on each individual implant available in the marketplace compared to when the original titanium implant systems were released. To some extent we are all guessing with some of the new systems in regards to longevity. It is reasonable to say that most implant systems “work” – in fact most seem to integrate well. It is usually acknowledged that the failure rate with implants is about 5% (although many clinicians seem to be achieving better results than this). The failure rate usually increases with medically compromised patients (especially diabetes) and smokers. At the same time, the literature seems to indicate success rates of between 55% to 65% for implants (success usually being defined as the implant being stable, asymptomatic, good bone levels and free of pathology). Thus there is a “grey” area between failure and success and this would seem to be about 30% to 35% in most cases. It is this “grey” area that should concern clinicians. The real issue is what does platform switching and all the other “modern” implant variations do to the “grey” area of results? Whether the various new “ideas” (including platform switching) will significantly reduce the percentage of grey remains to be seen in long term clinical trials of the new implant systems (probably retrospective studies due to commercial necessity). I suspect we will have to wait several decades before we finally know the answer in most cases.