cracking porcelain on long span bridge

[labguy5381]

Thanks...All very good comments. Yes, Bob I agree...this anterior span is a huge cantilever force on those abutments.

 

[dmonwaxa]

Its not uncommon to see cracking of the porcelain on cases I like this when the design is a wrap around.....full coverage no lingual band's or metal islands etc. That's because the absence of those increases the possibility of the porcelain remaining in a state of tension rather than compression ...which is desirable.

 

[charles007]

I desire metal free lol but not on this case for sure

 

[ztech]

Its not uncommon to see cracking of the porcelain on cases I like this when the design is a wrap around.....full coverage no lingual band's or metal islands etc. That's because the absence of those increases the possibility of the porcelain remaining in a state of tension rather than compression ...which is desirable.

I actually do full wrap around on cases this size and larger routinely without any problems. The porcelain is put under compression by the slight difference in the CTE, the more wrap around you can get the more it is enhanced. The problem is getting the alloy to cool properly to create the compression while the ceramic cools.

 

[orange]

You mentioned you had no cracking during the first firing stages the problem occurs during glazing stage, try prolonging the cooling time during glazing. It happens to me so far this is my remedy.

 

[labguy5381]

Several of you have mentioned using non precious on this case. What is your reasoning here? I know strength...are there other advantages in this case? This original case was in palladium based alloy.

Thanks

Oh, by the way...I like the lottery solution

 

[dmonwaxa]

@ ztech

I'm trying very hsrd to see and understand how the alloy creates the compression. Please share.