Emax greyish stains after glaze firing

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kipsas

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Ci_VhliFLr
Hello,

I have recently started making some emax crowns/onlays, and first few were all fine, but now I faced a problem, none of my colleagues were able to help me with, so I thought I should ask a bigger community :)
So everytghing is file until I put the glaze on a finished crown. The crown is all pressed, individualized with stain (no additional layering),after the stain firing in the oven crown looks fine, but after the glazing - whole crown looks like if it was treated with smoke - grayish, with dark spots (especially where the glaze might be thicker - like fissures, or edges near the margins). I am attaching a picture, the crown should be B1 shade, though looks 3-4 shades darker (sorry for no reference pic with shade tab, will post tomorrow),
Maybe some of you have experienced similar issues, and could help me identify what might be causing this staining?
Thanks for your help
 
rkm rdt

rkm rdt

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Your muffle could be contaminated.

Do you fire pfms in that furnace?
 
M

MasterCeramist

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What brand of glaze are you using emax,lustre paste etc. ?
 
cadfan

cadfan

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Make a cleaning burn max temp 10 min hold maybe the muffle is contaminated have seen this using some LF ceramic we do this one time a week.
 
Patrick Coon

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The grey is usually from the organics in the glaze paste not burning off completely before the vacuum starts.
I would recommend not using the Vita firing paste for two reasons:
1. Additional organic load in the oven that will have difficulty burning off.
2. It contains a spun alumina fiber that will stick to the inside of the crown during firing and the only way to remove it is to sandblast with ALOX, which is a definite NO-NO with e.max after the restoration is final glazed. This will reduce the fracture toughness of your restoration by about 50% and also when you etch the restoration you do not get a good etch pattern for bonding/cementation.
If you must use a putty I would use one that does not contain the spun alumina (such as Object Fix),and only enough to secure the restoration on the pin. Just like Brylcreme – A little dab ’l do ya. That way during firing it will not add an extra organic load to the furnace and after firing it will wash out clean with a toothbrush and running water or a steam cleaner, no blasting required.

Also, don’t overload your oven with restorations, I usually try to stay to 6 or fewer, and if it is a larger bridge lower your rate of rise to allow those organics in the fluids a little longer to burn off. Your vacuum should also start about 50C/120F after your furnace starts to heat up, this will allow the organics to volatize before the air is pulled out of the chamber. After the chamber pulls vacuum, they can no longer burn out and are trapped in the ceramic and turn it grey or black.
 
Marcusthegladiator CDT

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Marcusthegladiator CDT

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You dont need 20psi. Thats way too much to "clean" inside an all ceramic crown.
 
Douglas

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Hey there,
We have had this issue before. First, I found that firing in a furnace used with your pfm work ( especially base alloy) can cause this. We also use washable stick glue on veneer cases to keep them on the model and this can cause the gray tint if not thoroughly cleaned out before firing. But based on your photons it appears that your pressing furnace or porcelain furnace has contamination. Hope this help.
 
Z

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I think Pat may have it, Also not all furnaces are able to hold at entry temp before pulling vacuum but that helps with the organic burnout.
Hi, Pat...Friend from Germany here, was in the office next to Pizana when we moved to Sembach.
 
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Also be sure to use a dedicated glaze brush with no cross contamination, and don't mix different liquids including water into your mix.
 
dentss

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Sometimes I have this problem.
This is an a3 vita
uzepuqa6.jpg

Monolithic emax lt
 
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Looks like youre trying to cover a very dark prep. Patient has quite straight line-angles, so I think you need to rework some of your shape too and not have them so ovoid. At the same time you could close up the gingival embrasures and knock down some of the stippled surface texture...but yeah, that's gray.
 
NicelyMKV

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Sometimes I have this problem.
This is an a3 vita
uzepuqa6.jpg

Monolithic emax lt
So they are not that grey in the lab? Could the doctors bonding material grey out with improper protocol?

I was present during a 6 unit anterior seating one time. They looked Great during try in. I went up front to talk to the office staff, and within thirty minutes the assistant came running to get me. I went back and the crowns had completely greyed out. We came up with one of the catalysts turning grey for some reason, but never really had solid confirmation. Had to prep off and redo..... Used different bonding agent and did
Not have greying effect...


If you never make a decision then your possibilities are endless.
 
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I cant remember the name of the component, but Rob TheLabGuy has mentioned it years ago.
 
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