impressionHere’s a tip I learned the hard way—twice! Before I used preparation guides and reduction guides for veneer and crown preparations I would make my provisionals before I took my impression. Then I could measure the thickness of the provisional and be sure I had reduced enough tooth structure so my ceramist had adequate room. It is still a great way to check reduction, however, it also can affect the final impression if you aren’t careful.


Impression Materials and Air-Inhibited Layers

Vinylpolysiloxane impression materials are very sensitive to the air-inhibited layer that is present when bisacrylics set. If provisionals are made directly on the preparations the air inhibited layer remains on the preparations and will likely affect the set of the impression material. The images within this article show an impression that didn’t completely set and a model that was poured from another impression that I thought was okay, but when I saw the stone it was obvious something went wrong. impressionIf the provisionals are made directly before the impression is made, pumicing the preps aggressively and then wiping them with an alcohol sponge and rinsing thoroughly can protect the set of the impression. 

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Commenter's Profile Image Larisa CHIRIAC
October 10th, 2014
You can use consepsis from clinical research!
Commenter's Profile Image Dr. Jorge Montes
October 15th, 2014
I use Peridex on a cotton pellet to clean the preps and then rinse with water. But one thing I also found out the hard way is that many times there is flash from the Luxatemp material on the adjacent teeth. The reason I don't use pumice is because sometimes the tissue starts to bleed and then I have to wait for the bleeding to stop. We need to keep our time in consideration.