Custom abutments help!

rkm rdt

rkm rdt

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Check your investment instructions.Most do not recommend speed burnout with plastic components.
 
wwcanoer

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araucaria, thanks for getting things back on track!

And, RKM rdt, if you go back and reread posting 8, speed burnout technique was not used.

***: this doctor does high-end dentistry, and is willing to pay for top quality lab work. And in my opinion, top quality lab work doesn't just mean a perfectly matched custom shade anterior crown. It also means quality metal work, which is the foundation for a lot of what we do.

I don't mean to rant, but I can't imagine I'm the only one out there who has experienced this problem. Which in my mind, means that somebody has perfected casting a UCLA custom abutment screw retained gold crown. I'm just looking after some good avenues to pursue without spending a small fortune on custom abutments and having to toss them in the garbage. Okay, metal scrap bin.

I do want to say thank you to everybody's responses so far, because I have definitely picked up a few ideas that I'm going to be trying this coming week.
 
rkm rdt

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, RKM rdt, if you go back and reread posting 8, speed burnout technique was not used..

Sorry,You're right,I was referring to a previous suggestion to place the ring in a hot oven and do a speed burnout.

I too was having the exact same problems as you. I reduced the expansion and I no longer wax to the metal base of the ucla.
 
Al.

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Check your investment instructions.Most do not recommend speed burnout with plastic components.

Thats what I was going to say, I didnt know you used regular speed investment.

For sure try not using any or as much special liquid to reduce the expansion, I think the investment may be stronger without the liquid.

I havnt had any problems doing it.

i use CB30. At least 1 hr 30 min bench set.
Put in cold furnace. Temp increase 10 F per minute. to 600 F hold for 1 hr.
10 F increase to 1550 hold for 1 hr then sling it. Its about a 4 and half hour burnout.

Here are my wax ups.

ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd27.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd30.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd35.jpg

This is type 4 gold.

ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd37.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd38.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd40.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd42.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd51.jpg
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd49.jpg

These are not large like full cast crowns, when I do screw retained full gold crowns I add a 3rd stage. From 600 F to 1100F and hold for 30 min, then run up to 1550F.

Hope something here helps.
ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd27.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd30.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd35.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd37.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd38.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd40.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd42.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd51.jpg ai46.photobucket.com_albums_f116_CDLAB_Dr_20D_drd49.jpg
 
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DMC

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Al, for screwed-retained....have you ever left any virgin UCLA Alloy exposed? To be later covered by the porc? Like, for tiny mandibular and little bi-cuspids? Keeps the emergence thinner right above interface of restoration and implant.

Obviously, you have the casting down to a science.
You abutments are text-book amazing!
 
dmonwaxa

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Isn't the question about doing full cast Au screw retained crowns? Why are we questioning porcelain application?
 
Labwa

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i think to find out what other people are doing in a different situation dmon.
 
dmonwaxa

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@Labwa


Its really great to know what others are doing to address a particular situation, ie porcelain application. In this case however, its clear that the problem was with a full cast crown; leaving the wax-up short or creating a ditch short of the collar on the cast to abt does not help in this situation. I really dont think that clients would accept this type of workmanship on this type of restoration. Sure you can fudge it by covering with porcelain on a screw retained pfm but not so on full gold. So how does one elimate the flash problem? There are many was to skin this cat, but first I think one has to understand materials and the techniques involved.

Some abutment designs on cast to's may encourage flashing. Cleaning with alcohol adds another element into the equation and one may actually inadvertently leave a flash of wax in the collar of the UCLA, unseen by the naked eye and leads to flashing. Solution? Be immaculate when waxing by keeping wax off the collar.

Secondly, understanding materials. Investments are formulated to create a certain percentage of expansion, and this is controlled by the special liquid.
Since the metal component of the machined UCLA will not expand as will wax in the invested ring a space will exist between the machined parts and the investment when heat treated during burn out. No expansion is necesary for cast to UCLA's as you would with a crown. One should not be concerned with tight fits with UCLA's as with a conventional crown since the parts are already pre machined to fit prior to casting. So, my solution for flashing on UCLA's? Use less special liquid for investing. Same applies for cast to screw retained PFMs.

Cheers
 
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wwcanoer

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First off, I would like to thank everybody for all of their input and words of wisdom regarding my “flash” issue on UCLA abutments.

I did another casting today, modifying my water\powder ratios, so I’d get less expansion. It worked!:D

picture.php
[/IMG]

I also like to add my two cents worth regarding how this whole thread evolved. The discussion about running porcelain down onto virgin UCLA alloy, was interesting, and is something that I would probably try in the future. Off track? Definitely, but also was important information to get out there.

What initially I found frustrating, which then turned into a humorous situation, was that the idea that I was using speed investment just kind of got ingrained in everybody’s minds. But, the fact that so many talked about using speed investment, made me realize that I need to work more on refining that technique with my gold crowns.

Thanks again all! Carol
 
JohnWilson

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Glad you got it worked out, I will caution people that say they just run glass down as shown in some diagrams. The picture with the shoulder of the gold cylinder exposed can be perfectly fine because you are still getting the opaque to stick to the casting alloy. If your alloy flashes close you will still have an alloy that oxidizes. so that means you opaque will stick. If you think you can run the opaque down on the collar of the UCLA you will soon find that the opaque can flake off the "non Oxidizing" gold they use for the UCLAs. bases.
 
disturbed

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Glad you got it worked out, I will caution people that say they just run glass down as shown in some diagrams. The picture with the shoulder of the gold cylinder exposed can be perfectly fine because you are still getting the opaque to stick to the casting alloy. If your alloy flashes close you will still have an alloy that oxidizes. so that means you opaque will stick. If you think you can run the opaque down on the collar of the UCLA you will soon find that the opaque can flake off the "non Oxidizing" gold they use for the UCLAs. bases.

John/anyone.
If you do get it opaqued and stacked without any problems would it still probably pose a problem with crown flex? chipping from the weakest area(non oxidized collor)?

kinda like the bond of porcelain to ZR and Ti..no (oxidation) bonding layer....:D

:sorry:
 
rkm rdt

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Proper substructure design prevents porcelain fracture .
 
rkm rdt

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[QUOTE

kinda like the bond of porcelain to ZR and Ti..no (oxidation) bonding layer....:D [/QUOTE]


or emaxpopcorn
 
JohnWilson

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John/anyone.
If you do get it opaqued and stacked without any problems would it still probably pose a problem with crown flex? chipping from the weakest area(non oxidized collor)?

kinda like the bond of porcelain to ZR and Ti..no (oxidation) bonding layer....:D

:sorry:

Well of course we have to compare apples to apples here. Like anything else we can have success deviating from known proper protocols but this doesn't mean we should implement it.

You do know material science right :)
 
dmonwaxa

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First off, I would like to thank everybody for all of their input and words of wisdom regarding my “flash” issue on UCLA abutments.

I did another casting today, modifying my water\powder ratios, so I’d get less expansion. It worked!:D

picture.php
[/IMG]

I also like to add my two cents worth regarding how this whole thread evolved. The discussion about running porcelain down onto virgin UCLA alloy, was interesting, and is something that I would probably try in the future. Off track? Definitely, but also was important information to get out there.

What initially I found frustrating, which then turned into a humorous situation, was that the idea that I was using speed investment just kind of got ingrained in everybody’s minds. But, the fact that so many talked about using speed investment, made me realize that I need to work more on refining that technique with my gold crowns.

Thanks again all! Carol

Carrie,

I'm glad you experienced success without any flashing. However, from the image you posted it seems like you have some technique issues to work out. There's some gapping between the cylinder and the gold casting, which leads back to you waxing (modeling) technique. Wax does not readily adhere to the gold cylinder, beacause of the cold metal the wax usually is repelled causing the gaps at the collar. You will have to modify your technique as I suggested earlier.

Also the thick band isnt really necessary IMO, my guess is that youre doing a final seal prior to investing and this may exacerbate the gapping issue.
 
BobCDT

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Why make a cast gold cast custom abutment if the doc wants a screw retained gold crown?
I must be missing something!
B
 
dmonwaxa

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It's not really a custom abutment, its a FGC cast to a gold UCLA abut. Typically UCLAs are used for the fabrication of custom abuts; and this is just another way to accomplish the same end much faster. Not so much in this case. :D
 
wwcanoer

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Give me a break! One thing at a time. Right now I'm just tickled pink that I think I have my "flash issue" figured out.

Yes, I definitely know that I need to fine tune the rest of my technique, but I figured figuring one thing out at a time would give me the best results in the long run.

Under the microscope, there actually is not a gap between the platform and the cast gold.

Carol
 
Hary

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What kind of casting machine are you using?
if you are using torch make sure you do'nt pass 8 bar for the oxygene. The spring for the casting arm should be less then your usual turns ex. if you use 3 turns for paladium you should use 2 turns for gold.
 
DMC

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Isn't the question about doing full cast Au screw retained crowns? Why are we questioning porcelain application?

Because of the title. Maybe if the thread was called Casting Full Gold UCLA, and not using the term abutment, we'd all be clear from the beginning. I think of an abutment as something that is not finished, and needs a crown/bridge on top. No?

It's a rare animal in my lab to have full gold screw-retained. Gold is so soft, why not just make a damn crown over an abutment?? If you need a hole to unscrew, then just make one later. Duh. Who want's a hole in their new Gold crown filled with light-cure ??(color)? What's the point? To save the Doc a few bucks??

I can't remember ever making one to tell ya the truth. :confused:
 

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