Occlusal Clearance with SP/CG Issues

[lil_leftee]

Hi, this may be a newbie question but I've recently had a dilemma with a doctor that was shocked at the net weight of a PFM Ceramic Gold (sometimes Semi-Precious) crowns.

The occlusal clearance between abutment and opposing was a good 25-35 mm and I was forced to compensate the extra clearance by adding more wax on the coping, thus forcing the Gold dwt up a huge notch. A premolar case came out to a whopping 2.7 dwt net weight that completely shocked the doctor. He scolded our manager asking why so much alloy was used, and naturally, we responded saying that it was necessary to support the porcelain.

In this situation, what would you suggest we should have done? Should we have just fabricated a simple dipped coping without any additional wax? Called the doctor first and discuss? etc..

 

[DMC]

Oh come on.

35mm is over an inch.

What species of animal are we talk'bout here?

 

[TheLabGuy]

Oh come on.

35mm is over an inch.

What species of animal are we talk'bout here?

Replacing some hippo teeth.........lol

 

[charles007]

Call doctor !!!!!!

I lost an accounts gold work for 2 years over a gold crown that the weight was 4.5 dwt............first ever that heavy and no porosity ......2 large 6g reservoir sprues to cast............

 

[dmonwaxa]

I vote mastadons; wholly mammoth

 

[CatamountRob]

wholly mammoth or wooly mammoth? or maybe you meant holy mammoth.

 

[AL1]

When there is that much clearance, the Dr. needs to do a buildup or endopost. You could also very carefully hollow out the inside. I have done that with extremely large gold crowns.

 

[kcdt]

Maybe he just left out a decimal point. That would be about right.

 

[dmonwaxa]

wholly mammoth or wooly mammoth? or maybe you meant holy mammoth.

lol,,,,Rob. play on words, thought it was cute. But you gave me a good laugh anyway. BTW check out my new thread IMP FGC...enjoi

 

[lil_leftee]

Yea.. the doctor's well known for restorations on hippos, mammoths, and other enormous creatures.

Sadly, during one preparation, he lost 3 toes to an elephant agonizing in pain and stampeding all over the office floor.

/sarcasm

lol thanks for jokes and off-topicness! ^_^ haha

Anyway, I apologize, I made a critical typo. I meant around 5-7 mm of clearance for a pre-molar. And actually, it wasn't only the occlusal clearance that was heavily open, but interproximally, there was also 4-5 mm clearance. It all added up to 2.7 dwt in 1 single gold coping.

The thing I don't understand is that this doctor almost always requests for ceramic gold or semi precious. So I didn't feel like I needed to contact him about the case. In the end, he complained to us like it was our fault when I'm sure he clearly knew the amount of clearance there was, and that the alloy would be gold/semi.

@AL1 Thanks for that suggestion of hollowing. I understand the idea of it, but I'm not sure how to go about hollowing the inside.

 

[TheLabGuy]

A simple phone call or email sure makes everyone feel better. Which brings up a good point, every Doctor I know has an email account, get it from them. It's perfect for situations like this, snap a picture and send it via email. It's always better to check than to 'assume'.......thats why they spell 'assume' the way they do, because it will make an 'ass' out of 'u' and 'me'.

 

[dmonwaxa]

First off with all due respect to all parties concerned. I would not recommend hollowing the inside; too risky and too much work. I suspect Al1 is refering to the occlusal aspect of the prep. Thats the only concieveable way to achieve this, I think. Problem is this would leave a large amount of space occlusally and might the lever effect on the crown since there is no occlusal seating of the intaglio, resulting in increased chance of failure. Al1 is correct however in saying that a buildup is necessary, I agree 100%.
The doc plays a role in this also, I'm sure he is aware of alloy cost but is just being frugal. It's a dammed if you do and dammed if you dont situation because if you dont build fir porcelain support, then it would more than likely fail. I am gonna attempt to post an illustration , so cross your fingers . Its a cross section of what think is going on. Blue reprsents the die, red = crown, and yellow = cement or cement space. As you can see if the occlusal element of the intaglio is included it would act as an anti rotational element of the crown without it however it increases the rotational nature of the crown.(Fig 1)
If crown is done using lest say a Straumann ITI solid abutment and you use the burnout plastic, you can get away with having some occlusal space. The geometric design will prevent any rotation. (Fig 2)

 

[kcdt]

I guess the lesson with this doc is to call first.
I will say that anyone who'd remove that much from a premolar and then act shocked probably has problems grasping reality on his own. So be forewarned. It may be all you'll get from this experience.

 

[kcdt]

First off with all due respect to all parties concerned. I would not recommend hollowing the inside; too risky and too much work. I suspect Al1 is refering to the occlusal aspect of the prep. Thats the only concieveable way to achieve this, I think. Problem is this would leave a large amount of space occlusally and might the lever effect on the crown since there is no occlusal seating of the intaglio, resulting in increased chance of failure. Al1 is correct however in saying that a buildup is necessary, I agree 100%.
The doc plays a role in this also, I'm sure he is aware of alloy cost but is just being frugal. It's a dammed if you do and dammed if you dont situation because if you dont build fir porcelain support, then it would more than likely fail. I am gonna attempt to post an illustration , so cross your fingers . Its a cross section of what think is going on. Blue reprsents the die, red = crown, and yellow = cement or cement space. As you can see if the occlusal element of the intaglio is included it would act as an anti rotational element of the crown without it however it increases the rotational nature of the crown.(Fig 1)
If crown is done using lest say a Straumann ITI solid abutment and you use the burnout plastic, you can get away with having some occlusal space. The geometric design will prevent any rotation. (Fig 2)

I agree that hollowing things out doesn't sound like a good idea to me either.

 

[charles007]

Meet with the doctor and tell him on this case, I will only charge only for the gold without any markup..... sell at cost, since it was extremely heavy, and you didn't inform him it would be a high dollar crown.......He's just pissed he has to eat the cost......
This idea may go a long way in your relationship.......

Charles

 

[AL1]

I go under the microscope with a small discoid and hollow out the inside underneath the occlusion and from mesial and distal if needed. Dont get it to thin under the occlusion. I leave enough of the axial walls intact to have a good fit, finish the margins and cast. Its also easier to cast with less gold.I have had gold crowns weighing 3.7 dwt ,at todays gold prices its to much. I think I billed out close to $250. There was no complaints but I feel bad. My PFC`s are under $200 with gold.

 

[AL1]

Something else I have done is do a buildup on the prep.

 

[DMC]

Something else I have done is do a buildup on the prep.

I've been waiting for one of you techs to say this....(not sure where Al was going with his answer, kinda vague)

Just make a two-piece crown. Simple.

Make a "top hat" out of NP or cheap silver alloy. You don't have to go all the way to the margin. Then, make Gold on top of that.

You could go a step further and cement the two together for your idiot Doc. Same thing as a core build-up (only indirect, and we get some $$ out of it).

I've done it a few times.

Scott

 

[TheLabGuy]

Like a telescopic coping? No galvanization by doing that?

 

[JohnWilson]

2 dissimilar alloys on different parts of the periodic table are likely to have a galvanic response. NP to Gold is a good example. Of course guys have been doing cast posts in NP with Gold crowns for years with the stigma that the cement is the buffer between the units.

Truth is its twice the labor to have your client save on alloy. I personally would wax the unit weigh it and make a call with the cost difference for the alloy you may stock.