Black Spots on Emax Press restorations

[Aditya Sawant]

Hi,
We have started Emax press restorations few days back and initially everything was good, but from last 2 weeks we started getting blackish/Grayish spots on single units where sprue are attached and then in case of Bridge we are getting black/grayish line on the pontic. We thought initially its Wax issue but we tried different type of Waxes but results are same. we are using PressVest Premium as investment material and doing direct burnout for 1 hr at 850 degree C for single 200 gm ring. we tried to increase temperature of furnace from 850 to 900 Degree C but results were same. Then we tried to change Sprue wax but then still result were same. Anybody had such issues in their past?

my instrumentation details are follows
ingots: IPS emax MT
Method: CAD/CAM Wax pattern and pressed using Stain method
furnace : renfert magma with catalytic converter
Press: Ivoclar P3010
Investment: IPS Pressvest Premium
Ring Size: 200 gm

 

[user name]

Photos would be very helpful.

 

[Doris A]

Photos would be very helpful.

This is their first post, so no pics until they have 5 posts.(I think)

 

[TheLabGuy]

The way they spruing is the cause of this...need a bigger sprue, or the angle of your e.max in the investment former is causing the e.max crystals to collect right at that point and cause this.

 

[Brett Hansen CDT]

The grey line in your pontics is where the lithium disilicate is coming together during the pressing. I think we fixed this by putting a third sprue on the pontic. Lab Guys post on single units is correct. We use an 8 gauge sprue and try and make sure the flow of the emax has to make as few "right hand" turns as possible. We angle the sprue/crown at about a 45 degree angle from the ring former.

 

[Patrick Coon]

Yes, everyone wants to save that nice incisal edge that they worked so hard on, so they cheat the sprue down the axial wall. But because of the shape of the e.max press lithium disilicate crystal (long needle like) as the material flows through the sprue they all line up like logs flowing down a river towards the logging camp. So the first crystals that enter the restoration must turn to flown down the long axis of the tooth, but the last crystals to enter don't get a chance to turn. Then when you cut off the sprue you are looking at the end of the crystal instead of the long side of it. In that orientation the crystal acts like a fiber optic cable and transmits the light through the restoration instead of reflecting it back and this appears as a low value (gray) circle on the crown. Same principle on the bridge pontics, but when the material meets up in the middle of the pontic they cause each other to turn, giving that gray line.



As for black specks, that is a contamination issue. Could be from ash in the wax, dust in the burnout oven, or (if stacking ingots) the label not fully burning off during the melting of the ingot.

(edited for spelling)

 

[Car 54]

Nice post, Patrick.

 

[Brett Hansen CDT]

Thanks for your post Patrick. Little more science behind the observed phenomena

 

[Patrick Coon]

 

[millennium]

How would you fix the gray line top to bottom of the pontic?

 

[Patrick Coon]

How would you fix the gray line top to bottom of the pontic?

I normally plan to layer a little (0.3mm) on all e.max Press bridges, and that covers it. Having said that, most of my colleagues here just stain and make it blend with the rest of the restoration. Being a vertical line helps with that. If it were horizontal, that would would be more difficult.

 

[millennium]

I normally plan to layer a little (0.3mm) on all e.max Press bridges, and that covers it. Having said that, most of my colleagues here just stain and make it blend with the rest of the restoration. Being a vertical line helps with that. If it were horizontal, that would would be more difficult.

Thanks Patrick, pretty much what I do.

 

[sidesh0wb0b]

Yes, everyone wants to save that nice incisal edge that they worked so hard on, so they cheat the sprue down the axial wall. But because of the shape of the e.max press lithium disilicate crystal (long needle like) as the material flows through the sprue they all line up like logs flowing down a river towards the logging camp. So the first crystals that enter the restoration must turn to flown down the long axis of the tooth, but the last crystals to enter don't get a chance to turn. Then when you cut off the sprue you are looking at the end of the crystal instead of the long side of it. In that orientation the crystal acts like a fiber optic cable and transmits the light through the restoration instead of reflecting it back and this appears as a low value (gray) circle on the crown. Same principle on the bridge pontics, but when the material meets up in the middle of the pontic they cause each other to turn, giving that gray line.

View attachment 32251 View attachment 32252

As for black specks, that is a contamination issue. Could be from ash in the wax, dust in the burnout oven, or (if stacking ingots) the label not fully burning off during the melting of the ingot.

(edited for spelling)

the only major issue with "proper" spruing is the constant breaking of the investment inside the ring. and before you say to switch to ivoclar investment....its happened with a dozen or more investments ive used over the years!
now, i have a work around....but its a PITA!

 

[Patrick Coon]

the only major issue with "proper" spruing is the constant breaking of the investment inside the ring. and before you say to switch to ivoclar investment....its happened with a dozen or more investments ive used over the years!
now, i have a work around....but its a PITA!

Bob, of course I want you to use Ivoclar investment, I like keeping my job.

But in reality, it is again about proper sprue angle and not overloading a ring. Or if you are using printed/milled patterns, either use a slow burnout from a cold oven, or switch to an investment made to withstand the way that plastic patterns expand during quick burnouts (PressVest Premium or another meant for that purpose).

 

[sidesh0wb0b]

Bob, of course I want you to use Ivoclar investment, I like keeping my job.

But in reality, it is again about proper sprue angle and not overloading a ring. Or if you are using printed/milled patterns, either use a slow burnout from a cold oven, or switch to an investment made to withstand the way that plastic patterns expand during quick burnouts (PressVest Premium or another meant for that purpose).

the issue im referring to comes from the press being too aggressive with proper sprue angle. especially on tall and skinny lower anterior preps. everyone here has had the issue if they have been pressing at all over the last couple decades. has nothing to do with investment which is why i said what i did.

 

[KentPWalton]

Could be some residual wax ash. I've had that in the past.

We used to put them in a "Bullpin" oven first and let them soak for 30 mins on like 850C, then do the final burnout. That seemed to help it. We were also using resin from the 3D Systems 3000DP. So resin and wax two different ballgames, but we had same issues.

 

[Aditya Sawant]

Thank you all for your valuable reply !!

However we have taken all most above steps into consideration like

1. Sprue: Sprue placement and angles are as per IFU's recommendation
2. Distance from wall is as per IFU's recommendation
3. Sprue thickness is 2.5 mm to 3 mm not more than this

But results are the same, we don't have black spots if you can see the pictures, these are Grey spots(discoloration) due to temperature and you all are correct that this is temperature issue. I would like to know what is permanent solution for this? or such spots will always appear on the restorations.
As a bandage, I have started applying Porcelain after trimming grey color area. same for bridges.

I am still struggling with Bridges are grey line i.e Junction is still evident, would like to know more details on solving this problem.

Thank you. its a great help for me !!

Photos:https://www.dropbox.com/sh/ywy28uvqoso4kk1/AABwNqzbEqdCF9lPJbdfluEra?dl=0

 

[Patrick Coon]

Thank you all for your valuable reply !!

However we have taken all most above steps into consideration like

1. Sprue: Sprue placement and angles are as per IFU's recommendation
2. Distance from wall is as per IFU's recommendation
3. Sprue thickness is 2.5 mm to 3 mm not more than this

But results are the same, we don't have black spots if you can see the pictures, these are Grey spots(discoloration) due to temperature and you all are correct that this is temperature issue. I would like to know what is permanent solution for this? or such spots will always appear on the restorations.
As a bandage, I have started applying Porcelain after trimming grey color area. same for bridges.

I am still struggling with Bridges are grey line i.e Junction is still evident, would like to know more details on solving this problem.

Thank you. its a great help for me !!

Photos:https://www.dropbox.com/sh/ywy28uvqoso4kk1/AABwNqzbEqdCF9lPJbdfluEra?dl=0

Aditya,

I do not want to argumentative, but these are not temperature issues. If you were getting to a temperature high enough to cause the glass matrix to start to devitrify then you would see this graying in the rest of the glass (and an excessive reaction layer as the glass would be so liquid that it would deeply penetrate the investment). If the temperature were too low you would be getting short pressings with either missing margins or large rounded divots in the surface.

1. The bridge: This is from the material coming together in the pontic and is a natural phenomenon. The only way to avoid this location of it is to sprue to the pontic as well, but you only move it to another location and actually create two of these lines. You also run the risk of breaking the preps due to the material pressing very fast into the pontic and then through the connectors into the abutments (This is why we don't recommend sprueing to the pontic). My colleagues in Amherst will use stains to hide the vertical line and make it look more like a craze line, but I personally plan on layering a small amount of porcelain on all bridges, especially when I consider these are in the esthetic zone and the LT material needs a little dressing up (in my opinion). If it has to be monolithic, and I have the ability, I prefer to mill bridges and I completely avoid this issue.

2. The Molar: Let me ask you to send a few photos of how you are sprueing these. To me it looks like you had it sprued directly to the interproximal wall of this molar, this would be incorrect. We would only recommend sprueing to the interproximal wall like this if it were an MO, DO, or MOD inlay where it is your only choice, and in those cases the gray spot will be hidden anyways. Normally we would recommend sprueing to the cusp tip of the molar at about a 45-60 degree angle so that the material can flow over the top of the prep and then down to the margins

 

[Patrick Coon]

the issue im referring to comes from the press being too aggressive with proper sprue angle. especially on tall and skinny lower anterior preps. everyone here has had the issue if they have been pressing at all over the last couple decades. has nothing to do with investment which is why i said what i did.

Bob,

Sorry if it sounded like I was coming at you, that's one of the problems with text based communications. You try to stay brief and you sound curt, if you get into an overly long response it can sound like your talking down or being a "know-it-all", and you can't hear the humor or sarcasm in a written response.

And yes those small, thin, "spindly" lower anterior preps can be a PITA. I'm glad you have a technique that works for you now, but for others out there who don't please allow me to give a few tips.

So, in my experience it is mostly a sprue placement issue that you can minimize, but not always eliminate this issue. This is because we have to look at two different things in sprue placement and those are: Proper angles to eliminate the gray spot (incisal edges and cusp tips),and proper angle to put the prep in compression during pressing v/s applying a shearing force on the prep (See illustration).

If it happens to be one of the preps like in the Shear force illustration (on right) if we place the sprue in the proper position to eliminate the gray spot then we place the prep at an angle to receive shearing forces (although it may not always be as severe as the illustration). If we place the sprue in a position to put the prep under compression, then we will get the gray spot. So what can we do? One thing is to place a small diameter stainless steel ortho wire (.030") into the prep area of the pattern during investment. This small piece of wire acts like rebar in cement and reinforces the investment helping it to resist breakage when receiving the shearing force (See Illustration). I do put a small loop in the wire end that sticks out of the pattern to secure it in the investment.

 

[sidesh0wb0b]

Bob,

Sorry if it sounded like I was coming at you, that's one of the problems with text based communications. You try to stay brief and you sound curt, if you get into an overly long response it can sound like your talking down or being a "know-it-all", and you can't hear the humor or sarcasm in a written response.

And yes those small, thin, "spindly" lower anterior preps can be a PITA. I'm glad you have a technique that works for you now, but for others out there who don't please allow me to give a few tips.

So, in my experience it is mostly a sprue placement issue that you can minimize, but not always eliminate this issue. This is because we have to look at two different things in sprue placement and those are: Proper angles to eliminate the gray spot (incisal edges and cusp tips),and proper angle to put the prep in compression during pressing v/s applying a shearing force on the prep (See illustration). View attachment 32313

If it happens to be one of the preps like in the Shear force illustration (on right) if we place the sprue in the proper position to eliminate the gray spot then we place the prep at an angle to receive shearing forces (although it may not always be as severe as the illustration). If we place the sprue in a position to put the prep under compression, then we will get the gray spot. So what can we do? One thing is to place a small diameter stainless steel ortho wire (.030") into the prep area of the pattern during investment. This small piece of wire acts like rebar in cement and reinforces the investment helping it to resist breakage when receiving the shearing force (See Illustration). I do put a small loop in the wire end that sticks out of the pattern to secure it in the investment.
View attachment 32314

all good @Patrick Coon !!!
and we do the same. run a piece of wire from the base up and over and into the pattern. keeps that bit of investment from breaking off during pressing. #winning