Why is platform switching good for implant restorations?

screw retained crown #30 with with platform switch

The first generation implants that came to the U.S. mostly involved an "external connection" attachment. These had a protruding hex with a small hole for a screw. They worked well but had the problem that too often screws became loose or even worse broke.  Then Core vent, 3I and Nobel Biocare  came out with implants designed internal attachments. These were popular and easy to use since it was much easier to  seat abutments and screws were less likely to become loose.

The Core-Vent design eventually became Zimmer and is still popular today. When I speak with my various implant surgeons they all say the Zimmer implant is a good implant today and it has a small platform switch. The width of the implant is slightly smaller in diameter than the parts the attach to it.

A newer generation of implants have a more severe platform switch and the piece the attaches to the implant has a rather severe taper as it emerges from the implant. it starts out narrow and widens as it emerges from the implant. This has the effect of keeping the margin of the abutment further away from the bony interface. There seems to be a growing consensus among implant dentists that this feature tends to make bone die back adjacent to the head of the implant less likely. Some of the earlier designs often experienced bone resorption around the head of the implant slowly after placement and it seemed to often to continue exposing the threads (not a good thing).

What makes the platform switching a good thing? While no one really knows for sure, it seems that one  good theory is the platform switch keeps oral bacteria further away from the bone housing the implant.  The screws attaching either the implant abutment and implant screw retained crowns are not hermetically  sealed  and allow bacteria to travel along the interface with implant and pump out from the margin of the the restoration.  As the implant restoration functions in the mouth it can flex slightly causing microscopic movement that is thought to "pump" bacteria out horizontally towards the edge of the head of the implant.  The platform switch, at least in theory,  keeps this bacteria further away, possibly creating a healthier environment for the supporting bone.





from Ask Dr. Spindel - http://lspindelnycdds.blogspot.com/2019/07/why-is-platform-switching-good-for.html - http://lspindelnycdds.blogspot.com/

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