cracks in d.sign porcelain using d.sign 84 alloy

K

king v12

New Member
Messages
1
Reaction score
0
after firing lots of cracks on 8to 12 unit bridges
 
doug

doug

Well-Known Member
Full Member
Messages
2,657
Reaction score
375
What is your firing cycle?
 
GG - J

GG - J

Active Member
Full Member
Messages
408
Reaction score
14
Cracks ?
Steam tears ?
A pic of your issue might help
 
2thm8kr

2thm8kr

Beanosavedmysociallife
Full Member
Messages
11,304
Reaction score
2,510
How many times has the alloy been recast?
 
Car 54

Car 54

Well-Known Member
Donator
Full Member
Messages
7,971
Reaction score
1,122
d.sign in general tends to be a bit of a finicky porcelain, let alone that span and how many times it's been fired,
changing the cte?
 
Mrs.galfriday

Mrs.galfriday

Well-Known Member
Full Member
Messages
1,500
Reaction score
456
The CTE is always important, but with this porcelain I'd go with finicky.

Layered firing is a must from what I have seen, in a lab where the long term tech always had problems. She recommended not letting it dry too long and any fissures in the body could be covered during the second bake. With a large bridge I am sure multiple firings are standard. As mentioned above, a photo might explain further. As in, frameworks not properly designed will have cracks. Covering the freshly removed bridge with a Pyrex dish will slow down the cooling, if that is the problem.
 
doug

doug

Well-Known Member
Full Member
Messages
2,657
Reaction score
375
This may not help now, but here's my process. I sprinkle shoulder power on the last opaque coat before firing. I use shoulder powder to fill under pontics and in the interproximals. This helps keep the porcelain from pulling so much when layering the dentine. i place on firing table at 400'C with a 6 in entry into the furnace. I have an 8 minute cooling when the furnace opens. Yes, I still get some tears and some margin pulls, but it has been a big help in reducing it. All of the crowns, base metal or semi-precious, are fired using the same program
 
Contraluz

Contraluz

Well-Known Member
Donator
Full Member
Messages
1,883
Reaction score
275
I still use d.Sign porcelain, even on full arges. And even on CoCr. frames. But d.Sign 84 is a Pd base alloy, which are not my favorite alloys to deal with...
d.sign in general tends to be a bit of a finicky porcelain
Mainly due to greater shrinkage than 'conventional' ceramics, which leads to tears. But not to cracks.
Layered firing is a must from what I have seen,
That I do on bigger cases. Easier to control volume and placement of the different layers. You can even stain onto the first dentin layer to characterize an incisal edge, for example.
With a large bridge I am sure multiple firings are standard.
Very true. I have fired d.Sign countless times on full arch bridges. As long as the framework is 'clean and solid', ie no bubbles coming up from underneath, you can fire d.Sign several times.
I sprinkle shoulder power on the last opaque coat before firing.
Good technique. What I do is what you mention below. At the same time, I brush glazing liquid over the opaqued frame and then sprinkle shoulder powder on it. Or dip the frame into the powder... ;-) So, I do my normal opaque firings and then I do the above mentioned.
I use shoulder powder to fill under pontics and in the interproximals. This helps keep the porcelain from pulling so much when layering the dentine.
Most of the time, I use a darker deep dentin, which helps the esthetics of the final bridge. Under pontics, I sometimes mix MM light into the DD, to get a bonier appearance.

To circle back to the OP question. I don't have an answer to your issue. But considering PD base alloy, I have a strong feeling of a framework with issues. Do you slow cool? Your cracks may be a sign of bubbles coming up, too.
 
Sda36

Sda36

Well-Known Member
Full Member
Messages
1,094
Reaction score
93
I still use d.Sign porcelain, even on full arges. And even on CoCr. frames. But d.Sign 84 is a Pd base alloy, which are not my favorite alloys to deal with...

Mainly due to greater shrinkage than 'conventional' ceramics, which leads to tears. But not to cracks.

That I do on bigger cases. Easier to control volume and placement of the different layers. You can even stain onto the first dentin layer to characterize an incisal edge, for example.

Very true. I have fired d.Sign countless times on full arch bridges. As long as the framework is 'clean and solid', ie no bubbles coming up from underneath, you can fire d.Sign several times.

Good technique. What I do is what you mention below. At the same time, I brush glazing liquid over the opaqued frame and then sprinkle shoulder powder on it. Or dip the frame into the powder... ;-) So, I do my normal opaque firings and then I do the above mentioned.

Most of the time, I use a darker deep dentin, which helps the esthetics of the final bridge. Under pontics, I sometimes mix MM light into the DD, to get a bonier appearance.

To circle back to the OP question. I don't have an answer to your issue. But considering PD base alloy, I have a strong feeling of a framework with issues. Do you slow cool? Your cracks may be a sign of bubbles coming up, too.
Try glaze cycle under vacuum, release @ 25° below high temp
Helps by putting ceramic under compression. From Tanaka •°• 🙂
 

Similar threads

Top Bottom