PFM BRIDGE CRACKED

[BLUE]

HELLO,

I HAVE FULL MOUTH PFM BRIDGE MADE 5YEARS AGO.

I REMOVE ALL OF THE PORC. AND RE-APPLY THE NEW PORC. AFTER SOLDERED TWO OCCLUSAL

HOLES DUE TO PATIENT HAD ENDO TREATMENT.

RIGHT AFTER THE GLAZE FIRING, THERE ARE CRACKS ALL OVER THE AREAS.

DOES ANYBODY KNOW THE REASON FOR THIS?

I EVEN BRING THE BRIDGE DOWN MUCH SLOWER THAN NORMAL CYCLE SINCE IT IS A MUTIPLE

UNITS.

ANYBODY KNOW HOW TO SOLVE THIS PROBLEM WITH OUT RE-DOING IT?

THANK YOU

 

[JMN]

HELLO,

I HAVE FULL MOUTH PFM BRIDGE MADE 5YEARS AGO.

I REMOVE ALL OF THE PORC. AND RE-APPLY THE NEW PORC. AFTER SOLDERED TWO OCCLUSAL

HOLES DUE TO PATIENT HAD ENDO TREATMENT.

RIGHT AFTER THE GLAZE FIRING, THERE ARE CRACKS ALL OVER THE AREAS.

DOES ANYBODY KNOW THE REASON FOR THIS?

I EVEN BRING THE BRIDGE DOWN MUCH SLOWER THAN NORMAL CYCLE SINCE IT IS A MUTIPLE

UNITS.

ANYBODY KNOW HOW TO SOLVE THIS PROBLEM WITH OUT RE-DOING IT?

THANK YOU

Providing you aren't having amazingly wild levels of steam tearing from wet porcelain drying too fast in the furnace and tearing things apart, it's likely to be the CTE.

That is, there is a mismatch between your porcelain and the metal's CTE.

Simply, the Coefficent of Thermal Expansion is a number that expresses how much growing and shrinking stuff does at the temperatures we use. The metal has a higher CTE and is expanding more than the porcelain pulling it apart in tiny little pieces like crazed glass.

ideally, ask the dentist what it is made of, 'Identalloy' stickers have been used for longer than 5 years so he will have a record of exactly what metal was used.
Then you can search the internet site of or call and ask the metal manufacturer what CTE range is acceptable for a porcelain system on this metal.
If it was another dentist, the patient will need to tell who placed the bridge so they can be contacted.

if you want to gamble and have another porc set on hand, check if it is higher CTE than the one you used. Not a goood soluton as it may have, still, a too low value and you've wasted time. Or worse was close, but fails in the mouth 2 weeks later.

edit: oh, and Greetings Earthling! Welcome!

If you could please turn off your caps lock key, it will make things much easier to read. Thanks.

 

[BLUE]

Thank you for your information.

But I am the one who made that previous bridge.

My question is that why it worked in the first time but not this time.

It was good for 5years until dentist took it out.

Any other options beside redoing it?

The dentist not trying to take a new impression and the model that I have is the one dentist took a pick up impression with that existing bridge.

 

[charles007]

What brand of porcelain did you use the first time and the second bridge ?
Did you slow cool on the second bridge ? Describe you glaze cycle.
Did you mean cracks over the soldered area only, or entire bridge ?

 

[BLUE]

I used creation porcelain on both of them.

I slow cool- almost spent 1hour before I took the bridge out from the furnace.

Cracks are all over the areas- horizontal cracks and vertical cracks on everywhere.

Anteriors, and posteriors but not the areas where I did solder though.

Any thoughts?

Thank you

 

[JMN]

Thank you for your information.

But I am the one who made that previous bridge.

My question is that why it worked in the first time but not this time.

It was good for 5years until dentist took it out.

Any other options beside redoing it?

The dentist not trying to take a new impression and the model that I have is the one dentist took a pick up impression with that existing bridge.

did you strip it down completely, or are you trying to just add on?

 

[BLUE]

I stripped completely and started from the scratch. Only used the old frame.

Thank you

 

[grantoz]

you may have cooled it too slow this will change the cte ,the porcelains cte will increase. if you can, just go back to your original cooling protocol and see what happens. good luck but i think you be staring again.

 

[grantoz]

by the way creation porcelain doesnt like slow cooling i know this from personal experience.

 

[BLUE]

I will try to fire it with normal program and see it can be solved.
Hate to redo the whole thing again!!!

Thank you very much for your helps.

 

[BLUE]

So one more question,

In creation web site,

Precious metals or non-precious metals with CTE of 13.8-14.9 at 25°-500° can be veneered with creation CC.

This means that white high nobel or yellow high Nobel are not comparable alloys for this porcelain?

The alloy that I used was white high noble.
Maybe I used the wrong alloy?

What is CTE?
Is it better to use higher CTE or lower CTE?

 

[BLUE]

And what is this mean by
CTE
25-500°C=14.4
25-600°C=14.7

What is this mean?

Thank you

 

[CatamountRob]

You need to use an alloy with a CTE between 13.8 and 14.9. I’d look for something in the middle. It’s like there is a sweet spot in that range. My experiance has been that you can be in that range and still have occasional cracks any where there is a large mass of metal that causes uneven cooling. You should be able to find any type alloy you want, white, yellow, noble, high noble, etc, with an acceptable CTE.
After you stripped the porcelain, did you sandblast it and re-oxidize it? Did you follow the alloy manufacturers directions? An improper oxide can cause fractures as well because you don’t have a good bond.

 

[BLUE]

Got it.
Thank you

 

[BLUE]

And what is this mean by
CTE
25-500°C=14.4
25-600°C=14.7

Why there are two different numbers?

 

[JMN]

And what is this mean by
CTE
25-500°C=14.4
25-600°C=14.7

Why there are two different numbers?

The extra temperature causes a greater range of expansion.

 

[2thm8kr]

And what is this mean by
CTE
25-500°C=14.4
25-600°C=14.7

Why there are two different numbers?

Because there were two standards of measurement. When matching your alloy to porcelain check to see which temperature the manufacturer used.

 

[JMN]

Because there were two standards of measurement. When matching your alloy to porcelain check to see which temperature the manufacturer used.

Definately a clearer response. Need more coffe.

 

[JMN]

How are you handling the metal between sandblasting and opaquing?
Gloves at all times?
Kept covered in distilled water and using forceps/tweezers?
Were they left uncovered on the bench in the heat/airconditioner vent path overnight(edit: so stuff could fall on them)?
Did you get all the flux off after soldering?

 

[Patrick Coon]

Solders usually have very different CTEs than the casting alloys. This is because they are usually meant to cover a wider range of alloys, based on melting temps. This is usually not an issue if you are soldering a rocking bridge, because that joint is very small and uses a minimal amount of solder. If filling a large hole from a root canal therapy or a large are from a miscast (and you don't use a chunk of the parent metal (to take up space),then now you have a larger area of a very different metal with a very different CTE.