Large PFM bridges cracking after glazing

[jcdentalcc]

I'm having some serious issues with large PFM bridges cracking right after glazing, I need advice to see how to correct this problems that has me very stressed. I've been doing large PFM cases for about 30 years with minimal problems, now for the last 6 months I'm having issues. All cases involve Rexillium III non-precious metal using Ceramco 3 porcelain. Rex III CTE (600 C) is14.3, Ceramco 3 ideal CTE is 14.4 - 14.9, CTE 13.9-14.4 requires no cooling and CTE 14.9-15.1 requires 2-3 minute cooling.
I have tried no cooling, slow cooling, fast cooling, taking it out at 1100 F and placing under a beaker, I've tried several methods and still the same results. Tonight after letting the bridge cool under a beaker until it reach room temperature I could hear the cracks as they happened. Any advice and suggestions would be appreciated.

 

[grantoz]

can we see some pictures it might help

 

[CatamountRob]

If it’s not a CTE problem then I would look at your de-gassing/oxidation firing and the way you are treating the metal beforehand. Double check and make sure you are following the instructions to the letter.
Having said that, it’s been my experience that large masses of metal magnify CTE issues. What works fine on a single unit crown may not work when a large pontic or large implant structure is involved.

 

[jcdentalcc]

can we see some pictures it might help

3 new items by Juan Carlos Villafane

photos.app.goo.gl

 

[millennium]

You have all kinds of cracking, horizontal and vertical. Maybe not enough metal support? Sharp edges in the incisal?
Also Rexillium has a very light oxide layer, maybe try a bonder before opaquing.

 

[PCDL]

I would look at your degassing. Purge and calibrate your furnaces, check for contamination. With the variety of cracks, and the size, that would be my first thought. This is assuming you arent trying to hang 5+mm of porcelain off your framework.

 

[Davor RDT]

Few questions ,
Are you using one ceramic system by it self or is there components from other kits ? Creation mixed with some vita stuff for an effect and universal glaze from another company ?

Do you naturally glaze or do you use glaze material ?

How clean are the solder joints is there any porousity in the joints and internally still have flux that hasn't burned out completely ? Otherwise how deep are the aproximal cuts in ceramic where interproximal contacts would be ?

Finally is there huge difference in thicknesses between occlusal and basal halves of framework ?

Some of these might cause trouble? Where exactly are the cracks?

 

[sndmn2]

When you flick the porcelain off does the opaque come off stuck to the porcelain ?

 

[jcdentalcc]

Thanks for everyone's help. The problems were solved by reviewing the opaque procedures we do and adding an additional sandblasting after degassing. Also when baking Ceramco 3 porcelain I lowered the hi temp from 1760 to 1680 and added a 10 - 15 minute cool down then placing it outside for 10 minutes to naturally cool down. Since introducing these changes everything has been working perfectly. Merry Christmas to everyone.

 

[rkm rdt]

You can eliminate the degassing stage. There's no need for it. Trim , sandblast, apply opaque and fire.

 

[GG - J]

Thanks for everyone's help. The problems were solved by reviewing the opaque procedures we do and adding an additional sandblasting after degassing. Also when baking Ceramco 3 porcelain I lowered the hi temp from 1760 to 1680 and added a 10 - 15 minute cool down then placing it outside for 10 minutes to naturally cool down. Since introducing these changes everything has been working perfectly. Merry Christmas to everyone.

https://www.dentsplysirona.com/content/dam/dentsply/pim/manufacturer/Prosthetics/Fixed/Ceramics/Veneering_Porcelain/Ceramco_3_Veneering_Porcelain_Materials/Ceramco-Porcelain-Troubleshooting-Guide.pdf