A question I get often is if it’s OK to use a Straumann impression coping without the snap on cap. And for reference, each closed tray impression coping from Straumann comes with two of these little caps that snap on to the top of the impression coping.
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The answer is no, you do not need to use these caps and in fact, from my experience, it’s actually better not to use them. Seemingly, the purpose of the cap is to provide a solid seat when placing the impression coping back into the impression. But, what we have found however is that sometimes that cap actually prevents the impression coping from seating completely.
And there are a couple of ways that can happen; The first is that the cap can shift slightly when the tray is pulled. This can cause the walls of the plastic cap not to line up completely with the rest of the impression. So when the impression coping is re-inserted in the impression, it hits the top of the cap wall and it feels like it’s seated.
The second is that the walls of the cap can be damaged at some point before or during the impression. Those walls are pretty thin and can easily be deformed which can again lead to an issue where the impression coping gets hung up by the plastic instead of seating completely in to the cap.
If you do want to use the cap, just be gentle when snapping it on to the impression coping to avoid deforming the plastic. I also recommend not using any wash material with these caps. Medium and heavy body impression material will do a much better job of preventing the cap from moving when the tray is pulled.