Bubbles after second firing or glaze baking using NP metal

[LDent]

Greetings all, Perhaps someone can pinpoint the problem Ive been experiencing for the last few months.

1)Porcelain: Noritake EX-3. Alloy:Bego wirobond 280.
2)Slight greening in crucible from previous casting.
3)Ingot melting time and technique duplicated and mimicked as indicated on Bego website video.
4)Only New metal used.
5)Tried both 110 pu and 250 pu grain for sandblasting
6)Steam cleaned
7)Then Ultrasonically cleaned copings for 5-7 mins
8)Air-dried completely before application of POBA (paste opaque base)--->2 bakes
9)Applied same thickness of Shade opaque as required for Semi-Precious alloys--->1 bake
10)Increased recomended manufacturers drying time by 2 mins
11)Decreased start temperature to 400 degrees C. as per Noritake troubleshooting guide
12)Tried to purge 2 furnaces with carbon to aid in chamber de-contamination.

Problem persists... IRREGULARLY!!! Hit or miss. Bubbles appear after 2nd body bake or glaze bake, particularly common around margin area (thin porcelain area).

I am about to change all burs for metal finishing (once again) to make absolutely certain that there is no cross contamination.

Does anybody have any other suggestions to fix this problem after all of those steps are performed and problem persists?

A solution would be greatly appreciated!!!!

 

[martintay]

Ok dont panic ! I use EX-3 opaque on all my PFm`s ! Even is i`m building with a different brand ( ie Vita or Ivoclar ) I have found over the years that Noritake as a base coat on cad - alloys or cast NP is unpredictable !! I use a base coat of GC-In Metal Bond (the pink stuff) and fire at 980`C - then apply a coat of EX3 opaque -100 % success !! Before GC In -MB came out i used a base coat of IPS Classic paste opaque with the same success ! I don`t know why this is a probem but it is ! I have a friend that does a lot of cad-alloy and EX3 and had the same problem and he fires the first coat of EX3 paste opaque at 1000`C !! and says that this has got rid of his bubble problem. If i were you i would use the In-Bond as its great to apply as a base coat - masks really well and the bond is awesome

 

[Bumfrey]

Yeah.
i use in-line, but i am experimenting with ex3. I use same metal with no problems. In 3 year i had three instances with bubbles. A burr change always stopped it.
I heard someone say hand wash or hand cream was a problem for them.
I use a steamer instead of ultra though. Increase the temp of first opaque fire by 50-80C.
That's all i got.

 

[martintay]

Ivoclar opaque is no problem - but in my experience EX3 as a base coat on NP or cad- alloy is a problem . Trust me

 

[Tayebdental]

I use the Noritake porcelain and it has been grate for me, I do not know if I could help you because I do not use NP alloy at all, mainly noble and high noble alloy and noritaki zirconia porcelain. As far as I know NP is more popular overseas than here in the US.

 

[Al.]

Ok dont panic ! I use EX-3 opaque on all my PFm`s ! Even is i`m building with a different brand ( ie Vita or Ivoclar ) I have found over the years that Noritake as a base coat on cad - alloys or cast NP is unpredictable !! I use a base coat of GC-In Metal Bond (the pink stuff) and fire at 980`C - then apply a coat of EX3 opaque -100 % success !! Before GC In -MB came out i used a base coat of IPS Classic paste opaque with the same success ! I don`t know why this is a probem but it is ! I have a friend that does a lot of cad-alloy and EX3 and had the same problem and he fires the first coat of EX3 paste opaque at 1000`C !! and says that this has got rid of his bubble problem. If i were you i would use the In-Bond as its great to apply as a base coat - masks really well and the bond is awesome

Martin I've never tried the IN MB but it says it neutralizes the cte differences ?

Like the alloy I use is 13.9 which is in the ok range but fast cool. l for initial is 14.2 I think, so I was told that the metal bond may put my alloy into the ideal range without having to switch metal?

Have you heard or experienced this?

 

[martintay]

Al , i think it would help - as you say i reports to increase the CTE range +/_ ! Its good stuff

 

[martintay]

Guys just a tip if you want a reply on a post "like" the comment - so you get a notification ! Because for example 2 days later and the post has gone you dont know unless you trawl the previous post ( a bit like FB ) Hope that makes sense ! Just an idea Not meant to sound rude - Its just iv`e noticed people have made a comment that i would never have known about if i hadn`t had a look at the post again - sometimes days later lol

 

[2thm8kr]

Al , i think it would help - as you say i reports to increase the CTE range +/_ ! Its good stuff

I'd like to hear a scientific explanation of how that works.

 

[martintay]

I'd like to hear a scientific explanation of how that works.

I think you may have to ring GC lol - apparently it acts as a CTE buffering layer ? Out of interest i`m sure i`ve noticed that Ceramco crystals sprinkled onto the second opaque layer has a similar CTE cussioning effect !! How the hell do you spell cussion ?

 

[ts4341]

Martin where do you buy your GC Initial INmetalbond?

 

[LDent]

Great information!

So from what im gathering here, the GC in-metalbond is the sure solution? I just checked out the product and will give it a try.

In addition to the bubbles that we've been experiencing inconsistently when dealing with Noritake EX-3 and Begos Wirobond Series, Argens NP alloy also performed similar results.
When dealing with these NP alloys, There appears to be a difference when changing the wax design to prevent cracks from propagating. It seems that these alloys do not permit for as much non supported porcelain as do Noble alloys. Sharp edges are a definite no-no. Particularly with Posteriors and large pontics, cracks have been an ongoing problem along with the bubbles. Maybe this suggests a stress in the CTE? If this GC INMETALBOND can aid in both these problems, then it is worth trying.

The reason for this post is that this week I had the pleasure of seeing a delaminated buccal cusp of #35 and a crack originating from the margin of its neighbor molar #36 while patient was asked to bite on articulating paper before cementation. Could this be evidence of the unforgivable characteristics of NP crowns when dealing with non supported porcelain because although after delamination, there appeared to be about 1.3-1.5 mm of available space from the frame to the opposing tooth. The case is currently back in the lab and now it is under way to be made with silver palladium...
We recently increased the amount of NP crowns that have been cemented but are still not certain of their longevity due to these potential stresses in CTE. Im still not sure of what can happen in vivo that could trigger another crack. Theoretically NP crowns would be a cost effective product but so far im having difficulty in seeing its long term sustainabliity due to bubbles and cracks. What about the bubbles we CANNOT see that well enough under the porcelain that dont bulge? Perhaps there is evidence to support that these too are a potential risk factor in crack propagation!?

Are there any other known preventive methods to bubbles and cracks with NP alloys that have not yet been mentioned?

 

[martintay]

Martin where do you buy your GC Initial INmetalbond?

I`m in England _ Skillbond !

 

[martintay]

Great information!

So from what im gathering here, the GC in-metalbond is the sure solution? I just checked out the product and will give it a try.

In addition to the bubbles that we've been experiencing inconsistently when dealing with Noritake EX-3 and Begos Wirobond Series, Argens NP alloy also performed similar results.
When dealing with these NP alloys, There appears to be a difference when changing the wax design to prevent cracks from propagating. It seems that these alloys do not permit for as much non supported porcelain as do Noble alloys. Sharp edges are a definite no-no. Particularly with Posteriors and large pontics, cracks have been an ongoing problem along with the bubbles. Maybe this suggests a stress in the CTE? If this GC INMETALBOND can aid in both these problems, then it is worth trying.

The reason for this post is that this week I had the pleasure of seeing a delaminated buccal cusp of #35 and a crack originating from the margin of its neighbor molar #36 while patient was asked to bite on articulating paper before cementation. Could this be evidence of the unforgivable characteristics of NP crowns when dealing with non supported porcelain because although after delamination, there appeared to be about 1.3-1.5 mm of available space from the frame to the opposing tooth. The case is currently back in the lab and now it is under way to be made with silver palladium...
We recently increased the amount of NP crowns that have been cemented but are still not certain of their longevity due to these potential stresses in CTE. Im still not sure of what can happen in vivo that could trigger another crack. Theoretically NP crowns would be a cost effective product but so far im having difficulty in seeing its long term sustainabliity due to bubbles and cracks. What about the bubbles we CANNOT see that well enough under the porcelain that dont bulge? Perhaps there is evidence to support that these too are a potential risk factor in crack propagation!?

Are there any other known preventive methods to bubbles and cracks with NP alloys that have not yet been mentioned?

It sounds like the opaque is not bonding - did the bridge fracture right down to the metal ? Check burn-out furnace is venting ok !As i`ve said EX3 opaque does not like NP as a base coat !! The bond too NP is probably higher than Noble or SP, also the alloy in thin sections does not deflect as easily thus reducing the risk of fracture.Np frames are finished with new diamonds then i sand-blast 50um @ 4 bar - ultrasonic in water 2mins - dry in furnace 400`C . Gc In MB and EX 3(for the second coat) is the same fireing cycle -

Dry @ 400`C for 6 mins
Heat rate 60`C/min
Vac on @ 450
High Temp 980
Vac off 979
1 minute hold time in air.

No need to pre oxidize NP in fact don`t !
When opaqued ultrasonic in water for 1 minute to wash off "free oxide" which will send your porcelain greenish as soon as the moist build-up comes into contact with it.
Be carefull not to "pool" the opaque !
If its a large frame increase Dry Time to 8 minutes to be on the safe side

 

[JMN]

How are you retreiving & transporting them from the ultrasonic to opaque stage?

 

[user name]

Scrap the steam cleaner. Its the source of so many contamination issues, and provided you have clean aluminum oxide in your blaster running with clean air, theres no need for it.

 

[adamb4321]

I'm having this problem with EX3 and NP alloys too, not every day just occasionally. One thing that did strike me the last time it happened was that I inadvertently stuck the hot carbide bur I was using into a block of metal polish that was in the draw. Things like that are easily done and can't help much.

Bubbling can defiantly cause the porcelain to crack as the opaque has often deboned on a larger area than you realise.

The drying cycle is really important when using paste opaques, to hot an entry temp or too fast can cause problems and just to be a pain too cool an entry temp cause issues too.

Noritake apparently recommend using a hot plate to pre dry you opaques helps, haven't tried of yet but it can't hurt, at the moment I let he opaques sit on the firing platform till they've dried before I start the firing.

 

[MasterCeramist]

I agree with scrapping the steamer just this alone may cure your problem. On n.p. alloys i don't run an oxidation/degassing cycle on single units just fire a wash coat at around 20 degrees higher than regular opaque temp. With bridges the manuf. of the alloy we use aalba dent recommends using a degas cycle. After cycle is run look for any areas with splotches of dark color. If you see that refinsh alloy in those areas and degas again if all is a nice even oxide then proceed with wash coat .

 

[martintay]

How are you retreiving & transporting them from the ultrasonic to opaque stage?

Please explain ?

 

[JMN]

We hold them with sandblasted forceps/mosquitoes etc. by the very tip of the holder from the time they go into the sandblaster, until final bake/glaze. When they are going, as a group, to the poc. room after sand blasting they are dropped into distiiled water for transport to pocelain room. This way, nothing touches them, no chance for contaminates to come into contact with them. Our body oils even can cause issues if the are touched directly.