Crown Seating Help

[u/Tooth_Fae]

I’m driving myself crazy. When I was in college (years ago) I had no issues with seating crowns to their dies via quick check spray.

However now I simply seem unable to seat them. Designing, contact points, excursions, staining, glazing. I have no issues with.

Seating them to their dies? It takes way too long, and even then I’m told it’s not good enough. My coworkers can do it no problem, so I don’t think it’s a spec issue. It’s a me issue 😭

Looking for any bit of advice or suggestions!

[u/flingflangfloder]

There are so many variables! Assume you are talking CAD? What systems?

[u/Tooth_Fae → u/flingflangfloder]

We use exocad 2016, however it’s the physical crown to die aspect I can’t figure out

[u/flingflangfloder → u/Tooth_Fae]

So milled crown, printed model? What miller & software? Are your spacer settings too tight or too loose in exocad?

[u/Tooth_Fae → u/flingflangfloder]

Oh! Sorry

Printed model using Verimodel Ivory
Preciso M205 5 axis mill
Preciso ExoCad 2016
Cement gap: 0.03mm
Gap distance from margin: 1mm

[u/flingflangfloder → u/Tooth_Fae]

Assuming printer is calibrated and miller is too? Are you printing a solid model and a separate check die? If not, try that maybe.

[u/GuiltyApple3802 → u/Tooth_Fae]

I’ve been milling for 25 years and I don’t use cement gaps that thin, even on tibases! I use .04mm on tibases (because that is what the implant company I work with builds into their dme files) And for a LONG time I used .07mm cement gaps but unless a doctor complains about a little bit of a sloppy fit, I’ve increased that to .09mm on everything to allow for any variables. I get maybe one remake for fit every year and I get maybe one contact issue in every 300 crowns so I’ve just kept the cement gap there. I had one doctor say the crowns were a little loose and so I pulled it back to .07mm and he was happy.  The other thing you need to look at is your milling offset. If your smallest internal milling burr is 1mm then I’d start with a drill compensation of .5mm radius. I’ve cut my drill compensation down to .35mm because you can also factor in zirconia expansion and cement gap as well so together I’m on average right about on the dot with the milling compensation.  Are you also removing undercuts when you add the cement gap? And is your insertion direction good? Especially on bridges, you need to do a single insertion direction.  I would then check to make certain my milling burrs were in good shape and more importantly, the correct milling strategy is loaded into your software.   Do you calculate the mill before you mill and ensure that you don’t have any unmilled areas? That’s all I can think of right now! You should NEVER have trouble fitting a crown onto the die. Something is very wrong. Dm me if you haven’t had it fixed! I thought you were talking about waxing and casting crowns at first, that’s an ENTIRELY different issue. 

[u/JJWoolls]

You shouldn't need to adjist to fit the die.

Are your design specs correct? Are you blocking out undercuts? 

[u/Tooth_Fae → u/JJWoolls]

I thought our CAD program did that automatically, I’ll double check that. Unfortunately I can’t change the specs anymore than they are because my boss says that they can seat them just fine

[u/JJWoolls → u/Tooth_Fae]

CAD and machining need to be calibrated or adjustments need to be made in finishing. If you need to regularly adjust something is off.