Custom abutments help!

[JohnWilson]

Screw retained units seem to have a big resurgence for my lab, I think a lot has to do with what lecture the GP has just listened to. Cast full gold screw retained are more rare because of cost of the alloy.

We did just made a huge molar for this man we named "Jaws" that was on a WN strauman where I made a custom Ti abutment that was gigantic and then waxed a thin gold crown over the top with access to the screw. Best of both worlds for this situation. It would have easily been a 6 dwt of gold and we were able to make it 1.3 when we were done. Substantial savings for virtually the same product with out the weight.

 

[user name]

Crystobalite or Beauty cast...Too long on the hold. 15 minutes is enough. 1.5 - 2 winds is enough. Flash...too much vibration when investing causing water to separate from investment.

 

[dmonwaxa]

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.

Not to get in a PCN contest but,,,, if the thread was read one would understand regardles of the term used. I think the term Full Gold imples just that "Full Gold" and how does porcelain fall in that equation,,,,you're just wrong,,,wrong ,,,,wrong,,,,since you haven't done one in your lab I do understand.popcornpopcornpopcorn

 

[DMC]

Thanks.

 

[dmonwaxa]

Thanks.

Just yankin ur chain bro,,,,have a great weekend

 

[NicelyMKV]

The wax did not shrink away from the metal platform slightly did it? I always preheat any metal I am going to apply wax to so it adheres to the metal. I have a nail dryer with heat and air. I also heat up partials when I wax to them. Makes the wax stay right up against it.

 

[wwcanoer]

Asking questions on a forum such as this, in some aspects is a crapshoot! How much information is needed in order to get the idea across? For those of you that the following this particular query, as I stated in an earlier post it is interesting how things diverged, came back on track, then divert again. And then comes the terminology! As we all found out, I was using terms that I felt were correct, but obviously others didn’t!

As noted in my most recent post, I was able to glean enough information to solve my “flashing” problem, but still have some issues that need to be ironed out.

I think that if I had included all of the information below it would have been “too much information”. But in many ways, it is important information to get a full background of the situation.


History

Pre-2010

Kerr casting machine, with a heavy duty spring approximately 25 years old. Gold castings were accomplished with 1.5 winds. PFM castings-Aquarius hard from Ivoclar-2 winds

Casting technique for UCLA abutments-and full gold crowns screw retained, have been perfected. Originally, UCLA abutments were casting out short at the junction, and was advised to run a bead of wax at the junction, and increase burnout temperature up to 1200° from 1000°F, and to heat soak 1.5 hours, and most importantly changing spruing technique. Remember, this is all using Cristobalite investment. This information came from the Nobel Bio Care tech help people, and the friendly lab people up the street from me. UCLA castings were now casting complete. I’ve been using this refined technique for probably 8 years or so.

On average, I probably do three custom UCLA cast abutments a year.

Midyear-2010

Had to replace the spring in my casting machine. Even though the new spring was called heavy duty, it definitely “behaves” differently than the original spring. Gold castings are now done with 3.5 winds, PFM castings are now at 4 winds. Unfortunately there were several miss-casts before I figured that out.

Jump ahead to August 2011

Since installation of the new spring the previous year, I think I had only done 4 custom UCLA abutments. And these were abutments, not full gold crown screw retained castings. One had a minor short area, and one a minor amount of flash, but nothing like the photos in the original post. And, most importantly, I used the above technique regarding burnout temperatures.

The two full gold crown castings that started this whole discussion, were the first that I have attempted with the new spring in my casting machine. Because of the cost of a UCLA abutment, I thought it would be the smart thing to do to ask advice instead of go through a whole lot of miss-casts before I figured out the solution on my own.

So what do you think? Should I have included all the above information under “History”?

Have a happy weekend!

 

[Clear Precision Dental]

The wax did not shrink away from the metal platform slightly did it? I always preheat any metal I am going to apply wax to so it adheres to the metal. I have a nail dryer with heat and air. I also heat up partials when I wax to them. Makes the wax stay right up against it.

Nice trick/suggestion. I still remember Scott talking about a lady that used to sit on her dies for a while before waxing so that she could bring them up to temperature...

 

[dmonwaxa]

@ Carol ____history

No, I don't think the history was necessary. Miscasts due to excessive turbulence looks differently. BTW I'm just trying to help only been doing it for 20+ years.
Since the miscasts happened with the same casting equipment with which to finally succeeded, its then safe to say that your modification of the liquid/water ratio worked.
As for technique, like was stated hot wax does not readily adhere to cold metals, hence the need to modification was made.
Didn't mean to yank your chain if I did.

 

[wwcanoer]

Yank my chain? Not even close!

I honestly value everybody's thoughts and words of advice.

I think part of my problem is that I've been working solo for 30+ years, so when something goes wrong I don't have somebody readily available to bounce questions off of. I have a wonderful relationship with the lab down the street, and they have definitely helped me through some rough spots over the past three decades.

In regarding heating the metal abutment up prior to waxing, I haven't tried that with UCLA's. But, I have tried that technique when waxing up copings and sealing margins on metal abutments. Sometimes it works, sometimes it doesn't. I've even had them set overnight on top of my P 80 muffle to see if that would help in producing quality margins. I finally just take an impression of the metal coping screwed onto an analog with Impregum to give myself a stone die. It works for me.

 

[dmonwaxa]

You can also try GC resin, Picoplast from Bredent etc to start off with and create the marginal seal then wax as usual to finish.

 

[rkm rdt]

Why not just invest in an electric waxer with adjustable temperature settings. This is by far a better way to wax to metal.

 

[NicelyMKV]

Just found this in the 3i manual.
Improved Cylinder Retention Design
The new design incorporates machined vertical grooves that reduces the potential for miscasts due to the smoother alloy flow onto the gold alloy cylinder during casting. The vertical grooves provide mechanical retention and are designed to eliminate the problem on previous UCLA designs of the alloy stopping on the horizontal retention instead of flowing to the margin (fig. 10).

 

[Scuff75]

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.

I understand that many labs/dentists may not see the value or reason that a doc would want a screw retained implant restoration. I personally try not to use them unless I have to, but I can think of several advantages/philosophical trains of thought that may call for one.

Personally I feel that I have better control over the emergence of a cast UCLA abutment when compared to an Atlantis abutment - this is of greater importance when substantially sub-gingival or if the implant is not in an ideal position.

By using a solid cast restoration there is one less component/interface where a problem/failure could occur. Again, depending on the patient presentation (elderly with not the greatest manual dexterity, xerostomia or some other condition that creates on non-ideal oral hygiene environment) not having a crown/abutment interface is one less place to trap plaque/bacteria.

I understand your point about putting a hole in the surface a new all metal restoration and saying you can just drill one later if you need to access the screw. That is assuming that the patient is never going to move geographic locations and that the same dentist that delivered the restoration will be the one drilling that hole. But, as I'm sure you have seen, there are times when the access hole is not dead center in the middle of the crown. When accessing those screws you can end up obliterating a good portion of the occlusal table trying to find and then get adequate access for your driver.

I guess I just don't understand your irritation over the thought of someone wanting a one piece implant restoration. Also if the doc requested the restoration - out of all gold, as I'm sure he understands the current costs of metal and is going to pay his bill - why wouldn't you make it? If you talk them out of your services because you don't feel like doing the work or that the milled abutments are "better", then in the future as Atlantis type services become more mainstream and user friendly, if I really was a greedy/cheap doc - what would be your argument of why you (dental labs) should not just be cut out of the process and you can have the case once the abutment is already fabricated? Whether I asked you to wax me up and cast a gold crown, or a little gold santa claus and I was going to pay for your time/material - doesn't it pay the bills just the same and keep your lab going?

Lastly - the comment about gold being so soft....I don't recall any recent articles in the literature about gold abutment failures, or even one for that matter. Implants are designed to fail at the weakest component in the system - the screw.