Full arch bridge has rocking issue. any ideas ?

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DPS

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So i'm quite a beginner on full arches and i'm not sure what i did wrong . I Would appreciate if you check on my design and correct me.
The rocking seems to be in the midline area .Colleague tried to remove undercuts with grinding post sinter , as he always does that and eveyrything turns out fine . But this one just got worse.
I set different radial spacers on the abutments with undercuts ( 20 microns difference ) . Could it be the problem ?
 

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Brett Hansen CDT

Brett Hansen CDT

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This is a tough one. Are you layering porcelain on a zirconia framework? I don't see this bridge lasting long term if that is the case. We won't even do traditional porcelain fused to metal frameworks on these types of cases anymore. We only do monolithic zirconia bridges for these types of cases.

As far as the fit, it could be many things. How was the bridge sintered? We use a very long sintering program for these types of cases(~14 hours). We also sinter it so that the bridge is standing up in the sintering oven with 8 and 9 facing towards the top of the sintering oven. Your support looks good.

I would mill this same file in PMMA and check the fit. If it fits, then I would look at sintering as the issue with the bridge not fitting.
 
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tyjthomas

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I’m sure you’ve done this but make sure there’s no gingival mask on the model when seating it or any contact with the stone for that matter. It could me many things though from an incomplete mill in a spot to a scan body not quite aligned right to a sintering issue or even a path of insertion with a bunch of implants. I like the idea of milling out of PMMA and see what you can find.
 
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What was the temps and times on the cycle?
Oh God the rush on this case made me all dumb i just went with the preset program the sirona tech recommended and it must be the case (pritidenta blank , 4.5 hours. defienetly stupid ) . it is just unbelievable how before i got this job ,previous technician used to sinter all kinds of restorations with only one program and even the sirona support tech insisted we should not change the program saying it's fine with everything. Even a friend of mine with a similar workflow told me he was doing fine with this single program using dental direkt cubex2 and zx2 and prittidenta .
i did a remake ( scan and design all over again ) and milled out of dental direkt biozw this time and ran their recommended 11 hour cycle , tommorrow i'll seat it and will update on it's fit .
 
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This is a tough one. Are you layering porcelain on a zirconia framework? I don't see this bridge lasting long term if that is the case. We won't even do traditional porcelain fused to metal frameworks on these types of cases anymore. We only do monolithic zirconia bridges for these types of cases.

As far as the fit, it could be many things. How was the bridge sintered? We use a very long sintering program for these types of cases(~14 hours). We also sinter it so that the bridge is standing up in the sintering oven with 8 and 9 facing towards the top of the sintering oven. Your support looks good.

I would mill this same file in PMMA and check the fit. If it fits, then I would look at sintering as the issue with the bridge not fitting.
yes it's not a very good idea it's just the doctor is not scanning intraorally and sends faulty records all the time so we can't really risk making monolithic.
thanks a lot for your answer . can i ask what zirconia brand is that you use ?
 
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tyjthomas

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Oh God the rush on this case made me all dumb i just went with the preset program the sirona tech recommended and it must be the case (pritidenta blank , 4.5 hours. defienetly stupid ) . it is just unbelievable how before i got this job ,previous technician used to sinter all kinds of restorations with only one program and even the sirona support tech insisted we should not change the program saying it's fine with everything. Even a friend of mine with a similar workflow told me he was doing fine with this single program using dental direkt cubex2 and zx2 and prittidenta .
i did a remake ( scan and design all over again ) and milled out of dental direkt biozw this time and ran their recommended 11 hour cycle , tommorrow i'll seat it and will update on it's fit .
I would expect greater likelihood of failure/cracking from a faster sinter than distortion occurring. Keep us posted!
 

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