All-on-X sintering issue, inaccurate fits

[Dan_DentalDNA]

hi, been having the same hot/miss issue for the past couple of months and I need some helping figuring it out. Over the past 3 years my lab has been delivering zirconia restorations that fit perfectly on models until a few months ago. More often than not we will get an all-on-x arch that seems to rock on the model towards back implants, today we sintered one that chipped and it doesn’t seem to even belong to that model.
I’ve triple checked all sintering scaling, scanning, and exocad workflow. We use origin multi-y with no stabilization support (19 hour cycle),only our maxillary restorations have this issue too. The mandibular ones fit perfect. The oven is an older sintra oven that seems to display that it heats up just fine. Any one have any recommendations ? Trying a stabilizer for now, but it doesn’t seem like rescans, longer cooldown etc has helped.

 

[Toothman19]

Have you calibrated the oven?

 

[JonnyLathe]

I'd be willing to bet its because you don't use a stabilizer.

 

[sidesh0wb0b]

calibrate the oven, use a stabilizer.
especially for the max arch, that denser chunk of mass can warp a bit during sintering. had one break off the stabilizer not long ago and decided to give it a whirl. no dice. i know people that dont use stabilizers, but for me i would rather play it safe and use all the tools at my disposal to be sure the results are spot on.

 

[Car 54]

I didn't realize it took that long to sinter those type of cases...yikes. My 6-10 hour cycle for normal crown and bridge cases doesn't seem so bad after all

 

[tehnik]

Depends on zirconia. Katana and priti use 8-9 hr cycles for long bridges. I always use supports and dont have any issues.

 

[tuyere]

Use stabilizers for everything and cook the hell out of them, with very gentle and gradual heating/cooling curves. No, slower. Slower. A little bit slower. That's about right. Run it "impractically slow" for a test job and see if you can eliminate the rocking that way- if it's still there, you know the cause lies elsewhere, but if it resolves it you just need to dial in what you can get away with in terms of rushing things along.