(D1) Fixing temporary crown margin?

[planisphere]

Hello, I'm a current D1 learning to make temporary crown on a prep on a typodont.

Every time I make one, margin is somehow always open/defective that I always have to use flowable to fix it. But when I see youtube videos, it looks like they get closed margin on the first try without additional steps.

Does this mean I am doing wrong, or is it something that's supposed to happen, even for experienced dentists?

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[Boofy]

A lot of time that is due to removing the temporary material prior to setting. If you are using PMMA one way to prevent this is holding the stent on the site for 4 minutes, removing every 2 minutes for 10 seconds, until the temp crown has cooled completely. This should avoid any shrinking of the margin. The constant removing is to avoid locking onto the preparation.

 

[Gen. Beauregard]

Try and get ahold of some bis-acryl temporary crown material, either from a benevolent instructor or an upperclassman. It's the stuff that squirts out of an automixing tip from a gun or syringe, and it's what you'll use most in practice. You probably aren't allowed to use it yet though because of the skill development from using PMMA. It will let you know if the open margin is from your prep design or from material shrinkage. If it's from having too much of a belly, or undercut, in your axial reduction you'll have a bang-on margin, but your temp will be locked on (assuming your embrasures are clear). Pumping PMMA past an undercut will lead to a billowed out margin, like a skirt. If you have a nice passive fit and a nice margin, try it again with PMMA. If your margin is open then, it's probably from material shrinkage or a floppy stent. That just takes time and practice. It is a practical, yet frustrating right of passage. Be glad that the materials are covered by tuition and enjoy the monomer buzz. Just don't set the bench on fire.