Milled Bridges Rocking Again

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NickB

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Well, today I sat my ass down and WATCHED the waxers sprue everything. Turns out they are heating up the bar in order to bend it, then spruing the bridges to it after it mildly cools.
So, this is likely the main reason that the bridges are warping. Today, I made it known to them that they need to cut the bar if they need to bend it, then either glue it back or use wax
to reconnect it. But they must let it set up and cool before spruing onto the bar if they do this. We'll see if this fixes the issue.

I will still post photos today or tomorrow to show how they are sprued from the machine as sometimes I use a stabilizer bar.

Nick
 
DanM

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Well, today I sat my ass down and WATCHED the waxers sprue everything. Turns out they are heating up the bar in order to bend it, then spruing the bridges to it after it mildly cools.
So, this is likely the main reason that the bridges are warping. Today, I made it known to them that they need to cut the bar if they need to bend it, then either glue it back or use wax
to reconnect it. But they must let it set up and cool before spruing onto the bar if they do this. We'll see if this fixes the issue.

I will still post photos today or tomorrow to show how they are sprued from the machine as sometimes I use a stabilizer bar.

Nick
Can you mill in a CAD Cast type material that they can't warp
 
2thm8kr

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Well, today I sat my ass down and WATCHED the waxers sprue everything. Turns out they are heating up the bar in order to bend it, then spruing the bridges to it after it mildly cools.
So, this is likely the main reason that the bridges are warping. Today, I made it known to them that they need to cut the bar if they need to bend it, then either glue it back or use wax
to reconnect it. But they must let it set up and cool before spruing onto the bar if they do this. We'll see if this fixes the issue.

I will still post photos today or tomorrow to show how they are sprued from the machine as sometimes I use a stabilizer bar.

Nick
When I had waxers that were giving me trouble with this sort of thing, I would make them cut and solder the cases.
It only takes a few times to get properly waxed and sprued cases or you end up with an ace solderer.
 
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NickB

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Can you mill in a CAD Cast type material that they can't warp

Such as? I only know of wax alone. Ive heard of some using PMMA but not sure if that would work or not. Plus PMMA material is much more expensive
than the wax material (so Ive been told).

Nick
 
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Here are the photos from the spruing when I use the stabilizer bar.

20160719_103025.jpg 20160719_103135.jpg 20160719_124340.jpg
 
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Try direct spruing from the pontics only with individual flush head s for the abutements . It works like a charm every time .
 
kimba

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What investment do you guys use for your milled wax? We use microstar HS. I doubt its the investment.....I think microstar is very good. Just wondering if there is another investment
meant for any milled wax in particular.

DEGUVEST GF and ARGIVEST speed
both work with our milled wax which is Wieland. I use deguvest for bridges but to be honest the speed vest works well for shorter span ie 3 unit bridges, but I have never tried it with larger spans I just feel better with a slow burnout for larger spans , but that is not scientific , just the usual technicians voodoo.
glad you have appeared to have sorted it. Interestingly , my guy always understood English well when discussing pay rates , but seemed to have more difficulty when taking technical direction!!
 
vurban210

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Here are the photos from the spruing when I use the stabilizer bar.

View attachment 22424 View attachment 22425 View attachment 22426

Your issue is 100% spruing. That bar is a huge mass of metal and is so close to the bridge that when it cools there are some massive forces going on that are warping the bridge. Not trying to be a pr!ck but honestly, there is so much wrong going on there it is a wonder your bridges ever fit.

I could go on and on, but it would be hard to express in written word. I would be happy to help anyway I can and I can also put you in touch with someone that is a casting guru.
 
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I thought so , but to this day he still thinks I am a pri-k!!! go figure
maybe he thinks you are just a show off. Did you tell him what exactly he was doing wrong?
 
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Seems to me this tech just wants to get done with the work load, and doesn't care. We had a ceramist that broke a full round house Zr bridge in 2 spots while doing a first bake cause she that all bridges are fired the same from 3 unit to 14 unit. WTF!!! I asked here would she fire a full arch metal lingual bridge in the same program as a 3 unit frame pfm bridge? She said no, then I said why would you not do the same on a Zr bridge? I don't know she said...................... unfortunately old techs are stuck on old ways and don't get it sometimes. But the investing parts has never changed, talk to the high up on the food chain and let them know this is what is causing the issues and if the techs can't get in gear then maybe it is time for some replacements.

Water to liquid and sprueing of round house pfms are so crucial for fit not everyone should to it. maybe train and hone a single tech to be responsible for them narrowing the chances down a bit and if it happens again you know exactly who to go to.
Seems to me this tech just wants to get done with the work load, and doesn't care. We had a ceramist that broke a full round house Zr bridge in 2 spots while doing a first bake cause she that all bridges are fired the same from 3 unit to 14 unit. WTF!!! I asked here would she fire a full arch metal lingual bridge in the same program as a 3 unit frame pfm bridge? She said no, then I said why would you not do the same on a Zr bridge? I don't know she said...................... unfortunately old techs are stuck on old ways and don't get it sometimes. But the investing parts has never changed, talk to the high up on the food chain and let them know this is what is causing the issues and if the techs can't get in gear then maybe it is time for some replacements.

Water to liquid and sprueing of round house pfms are so crucial for fit not everyone should to it. maybe train and hone a single tech to be responsible for them narrowing the chances down a bit and if it happens again you know exactly who to go to.
How can a long span bridge "break in 2 spots" just because of firing it on 3 unit bridge program parameters? you may get porcelain under fired but not breaking the framework???
 
Sevan P

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How can a long span bridge "break in 2 spots" just because of firing it on 3 unit bridge program parameters? you may get porcelain under fired but not breaking the framework???
Sold Zr doesn't cool down as fast as our think. So when your small unit program has a cooldown down of 1min and you long span program has a cooldown of 12 min then yeah the Zr straight sheers clean. And the case has Zr lingual with each connector was well in size.

Sent from my SM-G920V using Tapatalk
 
kimba

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maybe he thinks you are just a show off. Did you tell him what exactly he was doing wrong?

Tell him what he was doing wrong ?? No , it's just my hobby to waste my time and materials by making 6 high gold metal frameworks with someone who was insisting it was not him , but the materials I had been successfully using in my laboratory for years!! Judging by the tone in your question to seven P let me guess, you are a young technician who knows a lot and everyone in the laboratory is just picking on you
 
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Tell him what he was doing wrong ?? No , it's just my hobby to waste my time and materials by making 6 high gold metal frameworks with someone who was insisting it was not him , but the materials I had been successfully using in my laboratory for years!! Judging by the tone in your question to seven P let me guess, you are a young technician who knows a lot and everyone in the laboratory is just picking on you
cheer up.. nothin wrong of showing off;))
 
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Sold Zr doesn't cool down as fast as our think. So when your small unit program has a cooldown down of 1min and you long span program has a cooldown of 12 min then yeah the Zr straight sheers clean. And the case has Zr lingual with each connector was well in size.

Sent from my SM-G920V using Tapatalk
Manufacturers generally note the slow cooling for veneering YSZ, some emphasizes only the last cycle that is the glaze. slow cooling by definition can't be more than 50c/m and mainly to avoid delamination. as for fracturing the framework itself I 'd like you to elaborate more on that since never happened with me and used to do 8-10 units a day including opaque and adjusting frameworks whether 3 unit bridge or full arch. many zirconia porcelains fire at 800c and find it hard to believe if the muffle opens at 800c without slow cooling to 400c then to 23c that will cause fracture
 
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Your issue is 100% spruing. That bar is a huge mass of metal and is so close to the bridge that when it cools there are some massive forces going on that are warping the bridge. Not trying to be a pr!ck but honestly, there is so much wrong going on there it is a wonder your bridges ever fit.

I could go on and on, but it would be hard to express in written word. I would be happy to help anyway I can and I can also put you in touch with someone that is a casting guru.

That photo shows what the machine mills out when I add the stabilizer bar. Its just one solid piece and not sprued with wax. And I cut back the bar to reduce that suck back effect.
Today, after showing how to properly sprue and invest to these waxers yesterday, we had two big bridges that fit really well. One waxer tried to heat up the entire bar to bend it
for a full arch bridge that was milled yesterday, and she sprued it without allowing it time to set and cool. I made it known that this is a big no no. They seemed to have gotten
the point. As for the length of the sprues on the photo.....Ive tried to make them longer in the software, but it simply wont allow me to do so. All I have control of is the thickness
of the sprues.
 
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That photo shows what the machine mills out when I add the stabilizer bar. Its just one solid piece and not sprued with wax. And I cut back the bar to reduce that suck back effect.
Today, after showing how to properly sprue and invest to these waxers yesterday, we had two big bridges that fit really well. One waxer tried to heat up the entire bar to bend it
for a full arch bridge that was milled yesterday, and she sprued it without allowing it time to set and cool. I made it known that this is a big no no. They seemed to have gotten
the point. As for the length of the sprues on the photo.....Ive tried to make them longer in the software, but it simply wont allow me to do so. All I have control of is the thickness
of the sprues.
When I used to cast, any sprues/rods that were heated and bent weren't used for 24 hours. I always had a few in the drawer that were bent for future use. In my experience, even a cold water dip and some time in the fridge isn't enough. They have to sit along time to fully lose memory.
 
TheLabGuy

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Yeah, I've said this is spruing technique since day 1. Glad you finally seen what they were doing.
 
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