Rocking, Rocking, ROCKING!

dmonwaxa

dmonwaxa

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Back to topic, "Rocking". IMO warpage of a FPD could also be related to the button size. This is probably overlooked by many. As alluded to in a previous post, a well respected and published technician in England proposed a technique for a passive fit every time, using a buttonless casting method. It works to this day. Dont guess on bridgework, weigh your junk before you cast. And for heavens sake use grams already...geeeessssshhhhhhhH!:Dpopcorn
 
TheLabGuy

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LOL Troy.......I do with full cast gold ALWAYS......but for your run of the mill PFM bridge, no problem, been doing 10 unit torch casting units without any warpage for years.
 
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cdl

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What nobody has picked up on regarding the rocking bridges is the expansion. If the bridge span is slightly over-expanded you will probably get a rock. I reduce the expansion liquid - water ratio by 0.5 to 1mm for a 60g ring. The actual copings on the abutment teeth end up a bit tight but the bridge span expansion is correct. This is especially important with cross-arch bridges.
 
Mark Jackson

Mark Jackson

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I didn't read all five pages of posts, but many years ago, we went through a whole slew of rocking bridges. Cooincidentally it happened about the same time we hired a new metal finisher. I thought maybe he was just extra observant and catching things our other technicians had been missing. Then our other technicians started seeing it too. Again, I thought maybe this guy had raised the bar and now the other ones were paying more attention all of the sudden, after all, nothing else changed.

Then one day I saw him in the casting room, and he was tossing hot rings into a quench bucket. Then a little later I heard this loud pinging sound coming from the casting toom, and caught him holding the buttons with plaster nips and banging on the bottoms to knock the investment off them.

I put a stop to both practices and everything went back to normal. FWIW
 
araucaria

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tossing hot rings into a quench bucket.
banging on the buttonbottoms to knock the investment off them.

curiously, what do folk find to be the most effective/efficient/simplest method of devesting metalwork. Size of rings, and production levels play a part in common working practices.
 
Mark Jackson

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We have a giant 100 pound capacity glass bead cabinet. It blows low pressure, but MASSIVE firehose quantities of beads. It devests any ring in a minute.
 
dmonwaxa

dmonwaxa

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Then one day I saw him in the casting room, and he was tossing hot rings into a quench bucket. Then a little later I heard this loud pinging sound coming from the casting toom, and caught him holding the buttons with plaster nips and banging on the bottoms to knock the investment off them.

I put a stop to both practices and everything went back to normal. FWIW

When you say stopped the practice, do you mean the individual was terminated?
 
Mark Jackson

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When you say stopped the practice, do you mean the individual was terminated?

No, I just told him that whatever he learned at his last job did NOT apply to his new job. He was tweaking the castings beating on the button like that, and I think quenching gold crowns is fine, but not ceramic frameworks.
 
dmonwaxa

dmonwaxa

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LOL....maybe he was trying to dewarp the castings since he knew it was already warped. Did he not know how to use the devester? Sometimes old habits die hard and technology scares off some.
 
Mark Jackson

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Just like ceramists. Some like to build up little pin size dots of ceramic and others like to build a giant glob and jackhammer it into a tooth shape.

Some people just prefer to beat things into submission.

I get it.
 
dmonwaxa

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Maybe it was an interview for the new ceramist position.
 
stt672

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I totaly agree with you. I know I have waste in investment but for bridges I fill abutments up with invesment with 5ml more of expansion liquid, then mix a second pour with 4ml less of expansion liquid to fill the ring. I got this advise from a former president of Colorado Dental lab Assoiation. It works for me every time. Good luck with whatever you try.
 
Gdentallab

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in the pdf brochure of talladium galaxy 2 the say how to do it.
 
oaktra

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did'nt see if this was already posted but I would also look at how and what type of model work is being done and are you in the habit of making sure your dies are fully seated? some times the dies get sawed out befor the stone is dry = no fun for waxer/finisher!!! also how is your investment stored,is the liquid by a outside wall I know if I leave mine in the wrong spot its got to be warmed up but since its winter did your company get you freeze stable liquid? you have got to love that even though its frustrating you will definitely figure this out and you will be an even better tech than befor...
 
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dentcre

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after 25 years doing bridges i started having lots of wax shrinkage , i can notice it right away after i finish waxing i can see that abutments lift.
strange ,,same technique for years and years,,,
it can also be a bad badge of wax or the manufacturer screwing up on the quality of the wax , there are so called "dead waxes" out there, try to get some and use it in your connectors.

..
 
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digidental

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I know this post has been around for a while but just thought I would add my opinion anyway.
This is how I sprue large units, the idea is not to have a button, for 2 reasons first I want my bridge to cool first, a button will slow down the cooling on the other end and if the feeder sprues are not joined to the button it minimises the chance of distortion

aimg803.imageshack.us_img803_273_img1001tp.jpg

If you do introduce stresses into your bridge after investing try running it through the furnace with a slow cooling cycle just a little hotter than a degasing cycle, the important thing is to make sure the temperature is well above any temperature that it will go to during porcelain firing, this can sometimes work in releasing any stresses in the bridge, I am a one man lab and it is a lot easier to control things, but in my time in a bigger lab this is one technique I had to use to help others I use to do it with a casting torch but that takes a little practice, it helps if you understand the material you are working with, its ok to cut corners as long as you are aware of what effect you are having, but in a bigger lab I found it was usually the corners someone else was cutting that was the cause of the problem
aimg803.imageshack.us_img803_273_img1001tp.jpg
 
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Harmony

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Wow allot of experts on their techniques here...... My experience, the most important factor here is to get your entire framework on the same temperature, that means cutting the connector, re-connecting it with either gc pattern resin, duralay or plain sticky wax (yes it actually does work very well) then put it in a bowl of room temperature tap water for 30 minutes. then take it out and invest. Mostly it is not the technique you use, but actually the way you remove it with your hand BE CAREFULL. I have never used a runner bar or any of that. as long as your sprue is thicker that the part you are connecting to, it will be cool. It also helps to use the bego acrylic sticks as connectors.
Let me know
 

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