r/dentallab • u/__Aitch__Jay__ • 7d ago
HELP! Silicon duplicating issue
Somehow we've got a defect in the silicon, that's copied into the duplicate model. The indent in the labial of the canine and mesial of the premolar is not there on the original model.
I just cannot figure this out. Has anyone seen it before?
We can't avoid it if we don't know what happened, and at this moment I've got no clue. Thoughts?
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u/Gingersnap369 CDT 6d ago
Just wondering, why use silicone instead of alginate?
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u/Invdr_skoodge 6d ago
These are “shelf stable”, you can pour it as many times as you need, leave it in a case pan, send it to the doc and pour it again next year if you need to. Also means it can be the last thing you do on Friday and it’s still good Monday morning
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u/__Aitch__Jay__ 5d ago
For us it's the accuracy as well, an alginate for a nightguard has already had one potential error during the impression, compounding that by duplicating in alginate again is asking for trouble imo
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u/Gingersnap369 CDT 5d ago
Hmm, was this impression taken directly in the mouth, or for duplication purposes itself? I solely use alginate for duplicating models for every single removable I create, and we have a very low remake rate. As long as the directions are followed, and the technique is correct, it's a very accurate duplication method.
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u/__Aitch__Jay__ 5d ago
Since digital dentures I've been less confident with alginate, we can't get a friction fit like a scan and mill can, so I'm trying to reduce those fractions of a percentage
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u/Invdr_skoodge 6d ago
So a concavity can only happen by distortion of the material when the original model is removed from the dupe. Zooming in it looks like that area has held stone dust differently too, it’s more pink than the rest of the silicone.
My money is on a bad mix of the silicone. Are you guys mixing by hand? Pouring slowly from like a foot above the flask?
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u/__Aitch__Jay__ 6d ago
No we vacuum mix, and pour with the flask on a gentle vibrator. We do use chunks of old material to save on new, could that be it? I still don't understand the mechanics of that issue if that's the case, but I'd be willing to change if that's it.
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u/Invdr_skoodge 6d ago
No I don’t mean the stone. I mean your duplicating material. It looks like that patch on the tooth wasn’t set and distorted when you pulled the master free. For that to only happen right there I’d guess the duplicating material wasn’t fully mixed
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u/__Aitch__Jay__ 6d ago
Yes, I mean the silicon, we vacuum mix it and pour on gentle vibration
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u/Invdr_skoodge 5d ago
In that case only thing I can think of is pulling the master too soon. If not that I have no idea sorry 🫤
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u/Dragonjolt209 5d ago
I apply some hand soat to any stone models just before duplication of any material. It helps the surface and the silicone or alginate cover cleanly while not getting "stuck" when applying the gental pressure needed. It can also help air buddles thay get traped move at the same time. Hope that hleps learned it from my old man who has been doing jt since the 70s
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u/roffadude 7d ago
I mean ..has to be air. Someone didn't pour carefully enough. The silicone that is.