Old Dental Crowns

[leoele]

Hi there! I'm currently a dental student, and I have a modest collection of gold and porcelain fused to metal crowns/bridges. I thought I'd look for some help online from people that know more about precious metal recovery than I do. There are over 100 dental students in my class (over 400 in the school!) and I am fairly sure that most of them do not save old crowns. It seems to me that this could be an opportunity that I should at least look into. Does anyone have any knowledge about this sort of thing?

 

[Harold_V]

Welcome to the forum!

What kind of knowledge do you seek?

Better yet, what color are the crowns/bridges you speak of? If they are a rather blue silver color, they're likely worthless unless they have gold solder used, which you may find under plastic. This material is vary hard and not ductile in the least. If you try to bend it, it breaks. Metals that contain values will be far more ductile and can be bent. They also tend to have a more yellow color instead of the blue/white of the high temperature alloy, even when they're not yellow.

Have you not studied alloys yet? Yellow dental gold can be high in gold, and contain respectable amounts of platinum and palladium, depending on the alloy. With high gold prices, new materials may contain much less of these elements. I recall some new alloys being introduced when gold was high back in '80.

Harold

 

[leoele]

I did some reading of other topics in this forum last night. From what I gathered, many people here aren't really aware of modern dental alloys. You are correct when you say that the high price of gold, coupled with patients concerns of aesthetics, has caused a shift away from high noble alloys (>40% gold w/ total noble metal content >60%). Palladium now actually bears the brunt of usage for high temperature alloys because of the silver color it imparts in alloys. I know for a fact that our dental school uses an alloy called Ultima Lite, which contains 81% Palladium. I can't guarantee that all of these crowns have that same composition, but what I do know is that every single one has at least 25% noble metal content.

 

[qst42know]

At the bottom of page 8 this article describes dental alloys that contain no noble metals.

Are you certain all of your material contains noble metals?

http://airforcemedicine.afms.mil/idc/groups/public/documents/afms/ctb_108343.pdf

 

[leoele]

At the bottom of page 8 this article describes dental alloys that contain no noble metals.

Are you certain all of your material contains noble metals?

http://airforcemedicine.afms.mil/idc/groups/public/documents/afms/ctb_108343.pdf

Wow, you are really making me work for this. I just broke out my textbook on dental materials from my first semester and read through some of the pertinent sections. While it is conceivable that some of the crowns use a base metal for the coping, in all reality base metals typically aren't used in this function in dentistry.

My textbook lists 7 relevant alloys, five of the seven are noble alloys:

Au-Pt-Pd (I know I have some of these, as they are the only gold colored alloys used for Fixed Partial Dentures)
Au-Pd
Au-Pd-Ag
Pd-Ag
Pd-Cu (I most likely have some of these, as this is the alloy type used at my school)
Ni-Cr
Co-Cr

I came to this forum to ask some questions in a field I don't know all that much about. I realize that I am not an expert in metallurgy. I do know a bit about the alloys used during recent years in dentistry. I wouldn't be here trying to learn more about something if I felt it was a waste of all of our time. So, that being said, is the general consensus that I am, in fact, wasting my time?

 

[Harold_V]

I came to this forum to ask some questions in a field I don't know all that much about. I realize that I am not an expert in metallurgy. I do know a bit about the alloys used during recent years in dentistry. I wouldn't be here trying to learn more about something if I felt it was a waste of all of our time. So, that being said, is the general consensus that I am, in fact, wasting my time?

I'm not sure I understand why you're asking that question. None of us (or at least precious few) have your expertise, and we all appreciate your comments. I would like to think that we, so far, have asked questions in a respectable way, and have contributed to your knowledge base, as you have contributed to ours. Is there anything in particular that troubles you?

I think you'll find that we are a pretty friendly bunch, generally mannerly, and often inquisitive. If our questions are troubling, understand that unless we have all of the available information, we can't really solve some problems, nor should we post opinions when we are not clear on the question. So then, speak up and let us know what's troubling you. Do be advised, it's best not to cop an attitude on this forum. We can work through most any problem if you maintain your composure.

Harold

 

[Oz]

I agree with what Harold said, it is the people doing the dental work that have access to the data sheets as to the alloys they are using. Many of us get dental material that spans the last hundred years or so with no tag saying what it contains.

You could be a valuable asset with your “on the ground data” as we are typically clueless at first sight of dental scrap as to its content. We would enjoy teaching you to refine as you teach us about the current alloys being used.

As was pointed out however, we are very quick to question things (especially when they are blanket statements as to a percentage of noble metals).

By all means break out your books to teach us. We will reciprocate in teaching you how to refine what you can get in scrap from your school.

Since you are in school, you obviously understand the “devil is in the details” in what you are learning and being tested on, it is no different with refining.

Welcome to the forum!

 

[qst42know]

It is quite possible your school only uses noble alloys. From my limited reading the noble alloys are easier to cast, work, and adjust. I meant no disrespect.

The appliances I might encounter may well be from any point in dental history. The strangest of which was bought at auction by a friend of mine which by visual inspection appeared to be an alloy of aluminum? I never did get the opportunity to test them further.

It had no porcelain teeth attached I suppose this could have been a pattern for making molds?

 

[qst42know]

I happen to know a moderator of this forum who may be interested in some or all of your palladium.


http://goldrefiningforum.com/phpBB3/viewtopic.php?f=84&t=7625

 

[Harold_V]

The appliances I might encounter may well be from any point in dental history. The strangest of which was bought at auction by a friend of mine which by visual inspection appeared to be an alloy of aluminum? I never did get the opportunity to test them further.

I had four of my molars capped years ago. I recall that temporary caps were installed while the gold caps were being made.

It had no porcelain teeth attached I suppose this could have been a pattern for making molds?

The temps were aluminum. Not a great fit, but adequate for protecting the tooth until it was covered permanently. So then, it's not impossible that one might encounter aluminum crowns of sorts in dental wastes.

Harold

 

[leoele]

I didn't intend to come off with an attitude. I'm actually pretty laid back. After seeing the first two responses, I was perhaps a little discouraged because it seemed that no one really believed that this metal could be worth much. Yesterday, I spent about three hours reading Hoke. Based on what I've read in these forums over this past week, Hoke's book seems to be a bible for precious metal recovery. Having studied chemistry in undergrad, I found it to be extremely interesting. That said, it it somewhat outdated in terms of current dental alloys. Let me share just a bit of what I know.

If you were to come across a full metal crown, it's composition is most likely > 60% gold, perhaps as much as 85%. Dentists love gold, because it's alloys are similar in hardness to natural tooth structure (enamel). Unfortunately, patients don't really like gold, because they don't like the color. If I was to ever need a crown on a molar, I'd have it done with gold.

Then there are porcelain crowns. You can have solid porcelain crowns made, but as porcelain is brittle, these types of crown typically fracture much sooner than other kinds. To solve this problem, a metal coping is made, and then the porcelain is baked onto the metal, held in place by an oxide layer that is allowed to form. The only trick here, is that the alloy has to have a higher melting point than the porcelain, otherwise it would just melt when you tried to bake it. Okay, so I have a lot of these types of crowns. But, there are definitely a lot of alloys that are used for metal copings. I looked at one of the major dental companies (Dentsply) to see what the offer in the way of alloys for crowns. I was a bit surprised that they offer 43 different alloys for crown and bridge work. You can see the list, and all sorts of good info here:http://www.ceramco.com/pdf/090871_AlloyChartDomestic_LR.pdf. If you look, you'll see that the five most commonly used elements are Gold, Platinum, Palladium, Silver and Copper. Also there is only one alloy that isn't noble, which should really clue you in to how unpopular these are in current crown/bridge work.

Finally, a lot of you seem to be hung up on removable partial dentures. Or at least, that's what it sounds like to me. The alloys used for RPDs are usually base metals, Ni-Cr or Co-Cr. I do not have any of these, and I'm not interested in collecting them. Oh, and just for your reference, here's what an RPD looks like:



Okay, well, that's all I have for now. I really need to get going, as I have to study for an Oral Pathology midterm.

 

[qst42know]

I have purchased removable partials much like your photo made entirely of gold and porcelain teeth, likely predating the use of dental plastic.

What metals are they made of at your school?

 

[Harold_V]

I didn't intend to come off with an attitude. I'm actually pretty laid back. After seeing the first two responses, I was perhaps a little discouraged because it seemed that no one really believed that this metal could be worth much.

I'm afraid you misread the comments, or, at the least, misunderstood the intended message.

I refined for just over 21 years. In that time period I processed a huge amount of dental material, including retorting silver amalgam. The points of concern are real and very valid. Those that salvage this type of waste often have no clue as to its content or potential value, to say nothing of an underhanded individual that knows better, but still promotes worthless material as being valuable. From my perspective, I wanted to insure that you understood that not everything has value to a refiner---and the line is broad. I've seen gold solder holding worthless materials together, and I've seen porcelain crowns made on high temp alloy, not easily sorted from those made on a precious white metal alloy. Just wanted to insure that you knew about all that, that you could possibly have something valueless. We do that here. We talk about things, and we try to teach and learn.

Hoke's book seems to be a bible for precious metal recovery.

Because I have no education, and because Hoke's book was the sole source of my knowledge, yes, I promote it as if it is the bible of refining. There's good reason, too. She wrote for the layman, for a guy that had no clue about chemistry, but had need to process values. It speaks clearly and provides processes that are very functional. There may be some processes that are superior, but the point is, her processes work, and work well.

Most importantly, she familiarizes the reader with testing and testing procedures, and hand carries one through the process of making and using testing solutions.

Unfortunately, patients don't really like gold, because they don't like the color.

Depends on the patient, eh?
About 25 years ago, I chipped one of my top front teeth. The dentist said repair was a piece of cake, he'd just grind the bottom flush, then remove material from the back of the tooth, to which he'd affix the white alloy. Not for me, says I. It will be gold. I was informed that people didn't like the looks of gold. I had to remind him that I was a person, and it would be gold, and nothing else. In the end, both of my front teeth (on top) were so repaired. Not done for any reason other than reliability. There was no vanity involved. Does it look funny? Probably to those that are overly concerned about such things, but I happen to like it.

I have to study for an Oral Pathology midterm.

Luck with the midterm.

Harold

 

[leoele]

I'm afraid you misread the comments, or, at the least, misunderstood the intended message.

I completely understand. I realize that if you get your hopes up too early, you'll most likely end up with disappointment. It makes sense that rather than assume a piece of scrap is going to be worth something, you'd be much better of to scientifically determine it's composition, and move on from there. That's why i'm here: to learn how to separate the chaff from the grain, so to speak. Right now, I am going to focus on learning how to test the crowns I have.

I am also going to look into gold recovery, because I am pretty sure that students are losing small bits all the time when they cast crowns/posts. As I was watching someone last week, I saw some gold go flying during the casting procedure. I hung around to see if the guy picked any pieces from the casting pit, and he did not. I feel this is very common.

 

[Fournines]

If you want to send me a few different crowns, I'll have them put through our XRF to give you a readout of the composition. Then I'll send them right back to you with the reports.

Let me know if you're interested.

 

[nickvc]

If you want to send me a few different crowns, I'll have them put through our XRF to give you a readout of the composition. Then I'll send them right back to you with the reports.

Let me know if you're interested.

There you go we are helpful here on the forum.
I'd take fournines up on his offer but, and this is the rub, use his results to give you standards to learn how to use stannous and be able to test materials accurately yourself.

 

[Oz]

That is a very generous offer Fournines.

For what it is worth, I have not done business with Fournines but others have and I have not heard a complaint. I have no reason to believe he is being anything other than generous. Sure, if you like his results I am sure he would enter into a purchase agreement with you.

 

[Fournines]

That is a very generous offer Fournines.

For what it is worth, I have not done business with Fournines but others have and I have not heard a complaint. I have no reason to believe he is being anything other than generous. Sure, if you like his results I am sure he would enter into a purchase agreement with you.

Thanks Oz

I'm happy to help out if I can. The crowns will come right back to you, and you can decide how you want to proceed.

 

[leoele]

If you want to send me a few different crowns, I'll have them put through our XRF to give you a readout of the composition. Then I'll send them right back to you with the reports.

Let me know if you're interested.

Thanks for this offer. It is very generous. I didn't respond at first because I didn't want to inconvenience you. It looks as if you are pretty busy trying to help run a susccessful company. It really says a lot about you by offering to help a newb whom you really don't even know. I really like the idea of getting a couple of readings and using those as standards for learning to test with stannous chloride.

 

[Fournines]

That is pretty much the spirit of the forum here, a lot of information and help is provided to people who want to learn.

Besides, I figure we can post some pictures and results for others to view and learn from. That way if others run into certain types of material they would maybe have a good idea of what it is.

It just happens that I have access to some good equipment (and people) at my company.