Full arch bridge has rocking issue. any ideas ?

D

DPS

Member
Full Member
Messages
50
Reaction score
0
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 ?
 

Attachments

  • 20211124_122522.jpg
    20211124_122522.jpg
    182.8 KB · Views: 70
  • 20211124_122457.jpg
    20211124_122457.jpg
    194.8 KB · Views: 52
  • 20211124_122440.jpg
    20211124_122440.jpg
    209.3 KB · Views: 40
  • 20211124_122416.jpg
    20211124_122416.jpg
    217.2 KB · Views: 66
  • 20211122_224624.jpg
    20211122_224624.jpg
    172.6 KB · Views: 71
Brett Hansen CDT

Brett Hansen CDT

Well-Known Member
Full Member
Messages
1,675
Reaction score
102
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.
 
Sevan P

Sevan P

Well-Known Member
Full Member
Messages
3,413
Reaction score
641
What was the temps and times on the cycle?
 
T

tyjthomas

Member
Full Member
Messages
70
Reaction score
1
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.
 
D

DPS

Member
Full Member
Messages
50
Reaction score
0
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 .
 
D

DPS

Member
Full Member
Messages
50
Reaction score
0
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 ?
 
T

tyjthomas

Member
Full Member
Messages
70
Reaction score
1
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!
 
D

DPS

Member
Full Member
Messages
50
Reaction score
0
The second try was better but not perfect . I placed another extra sprue on 8 and placed it vertically in the oven . Only thing i can think of is that i had to manually do some reduction on the support pre sinter ( material shortage , long story ) .There's still a bit of rocking . It' s going to get tried on in patients mouth anyway,although the i don't have much trust in this dentist's evaluation / judgement .
 
npdynamite

npdynamite

Active Member
Full Member
Messages
342
Reaction score
0
You also might consider adding a sprue at 4 and 11 on the sintering support side. Spruing only 2 and 6 on that side seems like a long span without a connection to the sintering block and the 9-13 span would strike me as the most likely area to see a bad fit due to it having a larger number of pontics than any other bridge sections
 
Brett Hansen CDT

Brett Hansen CDT

Well-Known Member
Full Member
Messages
1,675
Reaction score
102
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 ?
We use Ivoclar's Prime for everything that will fit in a 25mm puck. It's a great product, but there are other's on the market that are as good or maybe a bit better in some aspects. One of the main reasons we use this zirconia is because he have a strong relationship with Ivoclar and we also have two of their sintering ovens and their PM7 mill. I figure it's best to use their zirconia with their equipment as long as the zirconia meets our esthetic needs.
 
D

DPS

Member
Full Member
Messages
50
Reaction score
0
Fit on left quadrant ( patient's)was perfect but not good on the right .
Since we are going to layer i was concerned about reducing strength by having to cut more sprues post sinter . Is there a maximum ratio of sprues to units that has to be met ?
 
Brett Hansen CDT

Brett Hansen CDT

Well-Known Member
Full Member
Messages
1,675
Reaction score
102
Fit on left quadrant ( patient's)was perfect but not good on the right .
Since we are going to layer i was concerned about reducing strength by having to cut more sprues post sinter . Is there a maximum ratio of sprues to units that has to be met ?
As many as will ensure the framework doesn't fall off in the mill :)

Also, you can partially cut into the sprues before sintering so that they will be easier to remove post sinter.
 
npdynamite

npdynamite

Active Member
Full Member
Messages
342
Reaction score
0
I wouldnt say there is a maximum ratio, but in general the more "even" things are with zirconia the more even they sinter. So I would look to have the sprues that remain in tact for sintering to be more evenly spaced. Also a large area of pontics on a bridge that is otherwise mostly abutment supported is a likely spot to have a warp. For that reason I would ensure that besides being evenly spaced I would ensure that the spot with the highest likelihood of warping is supported
 
D

DPS

Member
Full Member
Messages
50
Reaction score
0
In the dental direkt catalogue , it has recommended to only place sprues on pontics or on abutments , not on both . That' s why i chose abutments , since there are more of them
 
npdynamite

npdynamite

Active Member
Full Member
Messages
342
Reaction score
0
Hmm, I can see the logic to that, though I feel like many things it is probably not a hard and fast rule and this is likely a situation that it would be okay to go against it. Those instructions generally line up with what I was saying about keeping things even.

Maybe someone else has a little more knowledge on this specifically though? I've never heard of only spruing one or the other but it does make sense
 
Top Bottom