HT Zirconia is yellow and not translucent?

[Marcusthegladiator CDT]

So, I spent the last few years milling on the MCXL and sintering frames, only frames, Never HT Zirc.
Then the DWX50 shows up and I cut this. It was a sample. Cut from Noritaki Katana ML A1.

It looked so good that I as a sample/test, I didnt want to stain anything, just a glaze and see the untouched results. It looked fantastic.
So then I cut a few single full casts from the same blank and sinter them so we could stain and glaze as samples/tests.
But these came out ugly as hell. Yellow and not translucent. Nothing like the bridge in the pic but cut from the same blank.
The only difference was when I sintered this bridge, I used no tray and no beads.
So I swapped out the old crusty yellow beads for some brand new shiny white ones.
Sintered a couple more Full Zirconia's from the same blank, and boom, just as ugly yellow non translucent.
So I am sintering one unit, no tray, no beads, resting on the muffle and I pray it comes out of the oven tomorrow morning as pretty as this bridge did.
My question, which is safe to ask since Scott is no longer here is...
Can the trays turn to crap and mess with my colors just like the beads?
Has the Zirconia frames on the MXCL been yellowing for the last few years and I didn't even notice cause I had nothing to compare to? And figured its Sirona Zirc, how good can a frame look?
Katana ML firing temp is 1500, i sintered this gorgeous bridge at 1600.
The samples that were in old trays with new and old beads were fired at 1500, 1530, and 1600 with bad results.
The trays? The beads?
I have my fingers crossed that when I go in in the morning the single unit I sintered at 1600 with no tray and no beads looks great, or FML.

 

[Marcusthegladiator CDT]

http://dentallabnetwork.com/forums/threads/zirconia-going-yellowish.17561/

 

[Brent Harvey]

Yellowing can be caused by a couple of reasons. By contamination of beads, trays, or muffle. Or the Silica Layer needs to be regrown on the elements depending on the oven. Email me and i can send you a purging cycle for you oven and at the same time clean the muffle. Then try with no beads and no tray and see what you get.

 

[Brent Harvey]

Yellowing can be caused by a couple of reasons. By contamination of beads, trays, or muffle. Or the Silica Layer needs to be regrown on the elements depending on the oven. Email me and i can send you a purging cycle for you oven and at the same time clean the muffle. Then try with no beads and no tray and see what you get.

Sorry i meant purge the oven and at the same time Regrow the silica layer on the elements...

 

[Marcusthegladiator CDT]

Yes Brent, I went through the last two famous post about this issue in the last year or two. As hilarious as ***'s responses were, I am going to go over what you and he said and try and problem solving this.

 

[Marcusthegladiator CDT]

To my sweet relief, the full crown I sintered without any beads and without a tray sintered just fine. So it was the trays and the beads. They were just old. I'm optimistic the problem is solved.


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[rkm rdt]

Since Scott is no longer here, let me respond.

You dummy,you should be selling shoes! How's that?

 

[Marcusthegladiator CDT]

Since Scott is no longer here, let me respond.

You dummy,you should be selling shoes! How's that?

I like it. But he most common refer to people as idiots. So you should have called me an idiot.

 

[rkm rdt]

 

[eyeloveteeth]

marcus is this a new oven? or is this the old Sintramat oven when y'all had the MCXL?

There are a couple of different reasons for contamination. Sagar Tray, beads, elements....

We have a big boy dekema and a big boy Nabertherm, and a Zirkonzahn sintering oven. The zirkonzahn with the smallest capacity is the most consistent.


now, at the old lab in NY, I ordered 4 S1 sintering ovens from ivoclar. The biggest reason being that their trays are not sagar trays but rather porous alumina. However, the S1 elements are not dipping friendly. (well technically none are, you're accepting that if you dip you'll be replacing your elements at some point, MolyB or SiC2.)

 

[ps2thtec]

I like it. But he most common refer to people as idiots. So you should have called me an idiot.

But are you a happy idiot?

 

[Marcusthegladiator CDT]

It's a ZYRCONMAT from vita that's not the old one but the new one and is about 3 years old. But the crown I sintered without a tray and without beads and it came out fine so I ordered new trays and beads and hopefully problem solved.


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[eyeloveteeth]

It's a ZYRCONMAT from vita that's not the old one but the new one and is about 3 years old. But the crown I sintered without a tray and without beads and it came out fine so I ordered new trays and beads and hopefully problem solved.


Sent from my iPhone using Tapatalk

just because you did one unit doesn't mean when you put that full arch in, that other gasses didn't screw with it later on. Also, what burs did you use? If there was ANY metal residue left, that would affect it too.

lastly i would mill those thin zirconia slices and run it in your oven. It's possible it's not as even as you like. We found the dekema (even though it is freaking expensive as hell) to be one of the most even heated ovens out there. The Nabertherm is great, and for it's price amazing, but you can tell not as even.

Zirkonzahn one,......seems really expensive for what it is, but it's a small sinter zone and does fine consistently.

 

[Marcusthegladiator CDT]

just because you did one unit doesn't mean when you put that full arch in, that other gasses didn't screw with it later on. Also, what burs did you use? If there was ANY metal residue left, that would affect it too.

lastly i would mill those thin zirconia slices and run it in your oven. It's possible it's not as even as you like. We found the dekema (even though it is freaking expensive as hell) to be one of the most even heated ovens out there. The Nabertherm is great, and for it's price amazing, but you can tell not as even.

Zirkonzahn one,......seems really expensive for what it is, but it's a small sinter zone and does fine consistently.

I've now sintered two single units without a tray or beads with success. So I ordered a new tray and new beads. For now I will leave tonight with some scrap green state zirconia with no trays or beads sintering at 1600. Of course I bought new 557 burs just for cutting the zirc from the blank and new white course silicone polishers to deliminate the sprues from the units. We'll call em white rubber wheels...

 

[eyeloveteeth]

silicone or Aluminous Oxide wheels?

 

[GG - J]

all my zirconia is turning yellow during sintering
HT - non shaded
run about 8 test cases
i have purged oven 2 X
raised high temp
imo i believe it is the oven - hard sell to my boss to purchase new one

 

[TheLabGuy]

all my zirconia is turning yellow during sintering
HT - non shaded
run about 8 test cases
i have purged oven 2 X
raised high temp
imo i believe it is the oven - hard sell to my boss to purchase new one

It is oven.
Is it calibrated? If so, then you need new elements. Cleaning cycle/purging works for maintenance purposes and extending life of elements but once there gone and still producing yellow it's time to replace the elements if calibration is still good. I'd tell my boss to glaze his own shltty yellow crowns, bet he gets elements then.

 

[GG - J]

I will re calibrate thanks

The elemnts were changed about 6 months ago
Prior to my arrival