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Using a cheap alloy and calling it a gold crown

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Dear Dr. Hall:
I had asked my dentist to use a gold alloy crown on my root-canaled tooth #15. When I asked about the alloy that was used, my dentist hadn’t even obtained the alloy certificate from the dental lab. So he got it from the lab, and I found out that the crown was made with 35% Palladium, 30% Indium, 30% Silver, 3% Zinc and ONLY 2% Gold. While the root canal itself was done properly, I am very much worried about Palladium and especially Indium in my crown for systemic impact on my health and allergic issues (though the dentists say there is no apparent allergic reaction around the
tooth) which from certain on and off vague external and on face skin reactions. Are these materials questionable? Especially Indium which I believe does not have long history of use in the crown. I would greatly appreciate your response. Thanks.
I found you by searching for dental crown metals.
Ranjit from New Jersey

(See Dr. Hall’s answer below.)


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Ranjit,
I don’t have any good information about the incidence of indium allergy or indium sensitivity. I haven’t heard of any. When I search online, there are some questions about it but no hard data. Indium is frequently used in alloys for dental crowns, but it’s usually present at a much smaller percentage, maybe 5% or less. Its use in such a large amount here appears to me to be a way to make the alloy a little softer without using as much gold, thus making it a cheaper alloy. There are two reasons gold is such a good metal for dental crowns. One is that it will not corrode. Another is that it is soft and thus the margins of the crown can be burnished to the tooth to make an excellent fit of the crown, eliminating the gap between the crown and the tooth that can harbor bacteria that will cause recurrent decay. Palladium is a very hard metal, so the inclusion of indium and silver will make the alloy softer, helping it fit better.

Palladium has also come under question. Are there documented palladium allergies? I can’t find any. You can read my earlier blog post where I answer the question, Is palladium a toxic metal? Palladium is present in almost all dental crown alloys without any apparent adverse reactions.

Do you need to be concerned about possible reactions to this alloy? I don’t know. If you are sensitive, yes, you would expect to see some inflammation where your gum tissue touches the crown. You’re not having that, so that’s a good sign.

But I will tell you that I am very suspicious of what your dentist did here. You asked for a gold crown, and it’s looking to me like he found an alloy as cheap as possible that could be called a gold alloy. And I do not believe that your dentist didn’t get the identalloy certificate until you asked—I think he threw it away. By law, the laboratory is supposed to send that certificate with every case and the dentist is supposed to put it in the patient’s chart. Is this an effort to conceal or just sloppiness? I don’t know, but I’m suspicious.

There are three broad categories of dental alloys that are used in crowns:
– high noble (called gold)
– noble (called semi-precious)
– low noble (called non-precious)

There are two requirements for an alloy to be called high noble or, in common terminology, gold. First it must have at least 60% of a combination of gold, platinum, palladium, and silver. Your alloy comes in at 67% there, so it meets that requirement. But the second requirement is that it needs to have at least 40% gold, so your alloy comes in way short on that.

Here is a sample of an identalloy certificate that should be sent by the laboratory every time a dental restoration is shipped to a dentist. This one is color coded yellow, meaning that it is a high noble or gold alloy. You may note that it has 2.6% palladium and 1.6% indium.
An example of an identalloy certificate. Its contents are explained in the text.
Please note the instructions at the bottom of the form: “DENTIST CERTIFICATE (attach to patient record).” I’m wondering why these instructions weren’t followed.

My advice here? If you have any reason to believe that you are having a reaction to this alloy, I would demand that your dentist replace the crown with a more suitable alloy or you will file a complaint with the dental board. In accepted terminology, your dentist did not give you a “gold” crown, which would mean using a high noble alloy. You got a semi-precious crown, which is a step below and cheaper.

– Dr. Hall

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About David A. Hall

Dr. David A. Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does advanced internet marketing for dentists.

Is zirconia radioactive?

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Dr. Hall, you have kindly answered a dental question for me before. Currently, I am wrestling with what would be the healthiest option for a crown for me to have placed on a lower molar (next to last) which has a 30-plus-year-old crown on it and which required dental surgery to remove severe infection so the tooth could be saved. It seems my dentist saved the tooth but he wants me to return in five weeks to remove the old crown and place a new one. He mentioned zirconia but I understand this material is extremely difficult to remove should I have further problems plus I have read there is radioactivity in this material. I considered e.max and then Encore PFM which has 4o% palladium. I am confused over what would be most healthy in the long run and my dental appointment is looming. Dental issues are definitely life changing. Any clarity you can provide me would be so appreciated. Thank you.

– Sandra from Mississippi


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Sandra,
So which is the safest crown? It probably has less to do with the three materials you mentioned and more to do with the expertise with which the crown is crafted. Your greatest danger with a crown, among those three excellent materials, will be with recurrent decay, which will be minimized by having a precisely fitting crown. And if your dentist was able to save this tooth from a severe infection, that’s a good sign that he may have the skills to make an excellent, well-fitting crown.

Yes, there are trace amounts of radioactivity in zirconia. Some zirconia materials used in dentistry are refined to minimize that radioactivity. But even without that, the amount is extremely small. There is also radioactivity of a similar amount in brick, stone, and concrete. Actually, there is even some radioactivity in water.

Some people also question whether or not there is an allergic sensitivity of some people to zirconia. We had one report of that and then it turned out to be a case of burning mouth syndrome. And yes, zirconia is very difficult to remove, but that is the dentist’s problem, not yours. He or she may wear out a diamond bur or two trying to get it off if that ever becomes necessary, but that won’t hurt your tooth any. The e.max crowns are also difficult to remove, porcelain fused to metal not so much.

If you are allergic to a lot of things, an all-ceramic crown would seem to be a good choice. The two popular, strong ceramic materials are zirconia and lithium disilicate. The CEREC crown-in-a-day is made out of lithium disilicate. The e.max crown is made of a lithium disilicate core veneered with feldspathic porcelain. It can be made highly aesthetic and has become very popular with dentists because of its strength, aesthetics, and the ease of working with it. I have one of those on a first premolar. But if you want the safest, longest-lasting crown on a lower first molar, cast gold would be the material of choice. Whether or not that would show would depend on how wide your smile is. I have crowns on three of my second molars, and they are all cast gold. Gold can be cast to a very fine margin, won’t ever break under the most severe oral stresses, and is extremely biocompatible. After gold, the strongest material for a crown for a molar would be zirconia.

– Dr. Hall

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Click here to ask Dr. Hall a question of your own.

About David A. Hall

Dr. David A. Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does advanced internet marketing for dentists.

Is palladium a toxic metal? My crown has palladium in it.

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Dr. Hall,
Recently from my periodontist who also does cosmetic dentistry I was fitted with 6 high noble porcelain-fused-to-metal crowns. I knew they were PFM crowns but later I discovered they are Encore crowns and contain 40% palladium. I have read of the toxicity of this metal and am concerned that there is such a high percentage of it in my crowns. I am now considering having them removed and considering e.max or even zirconia, whichever is the most inert. I hope you will advise me on what steps I should take.
Thank you for your time.
– Sandra from Delaware


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Sandra,
I was struck by your question because I had never heard of palladium toxicity, and I try to keep myself informed of these things. Many dentists, I feel, are much too casual about metal toxicity issues. You can check other posts in this blog where I list various metals used by some dentists that cause sensitivity reactions. But palladium? I decided to do some research to see where this idea comes from.

In the movie Iron Man 2, Tony Stark has an arc reactor that keeps him alive and powers his armor, and this arc reactor has a palladium core. In the movie, the palladium is poisoning his blood. In the real world, however, palladium is a noble metal and a member of the platinum group, and is fairly biocompatible. Yes, there are compounds such as palladium chloride that are toxic, but that is very different from the pure metal. And remember, that we are not talking about putting this metal into the tissue but only putting it into a situation where you are in superficial contact with it.

Also, in doing an online search, I discovered a natural health website that alleged that palladium is a heavy metal that is highly toxic. (not true—palladium is a precious metal that is actually fairly light.) To put their claims in context, near the bottom of the page is a link for visitors to get themselves tested to see if they have palladium toxicity. The link takes us to a page that urges visitors to send in $325 for a hair mineral analysis. So if we follow the money it seems that we are discovering the motivation for their mis-information.

Almost every dental alloy that is used in making crowns and bridges has palladium in it. Like platinum and gold, palladium doesn’t corrode. Its presence in a dental alloy lends a certain amount of stiffness to the alloy, so it is pretty much required in stress-bearing dental bridges. Alloys without palladium tend to be very soft.

Here is a chart of dental alloys manufactured by Aurident for use with porcelain-fused-to-metal crowns. Aurident is one of the leading manufacturers of dental alloys.
a chart of dental alloys used with porcelain fused to metal crowns, showing the percentage of palladium in the alloy
You can see the percentage composition of the various alloys. Au is gold, Pt is platinum, Pd is palladium, and Ag is silver. Notice that palladium, while it isn’t in every alloy, it is a component of more alloys than any other metal. When it isn’t present, the metal will be softer and will be more yellow in color. Soft is good in some situations. It makes the metal easy to burnish so that it fits tightly to the tooth. But a soft metal without palladium can also make the restoration susceptible to bending or breaking. The second column, labeled “class,” shows how the alloy is categorized. The square icon with the HN means high noble. These are alloys that have at least 40% gold and a total of at least 60% noble (precious) metals, of which palladium is one. Sometimes these alloys are simply called “gold,” and the term “porcelain fused to gold” is used. The triangles with the N are noble alloys that have at least 25% precious metals.

Even with gold alloys used in gold crowns, almost all of them have palladium in the alloy.

In my mouth, four of my crowns have metal in them—three gold and one porcelain-fused-to-metal—and I am pretty confident that each of them has some palladium content.

My opinion, Sandra—you don’t have anything to worry about, and as long as you are happy with how they look and aren’t having an allergic reaction, I would leave well enough alone. There are some instances reported of palladium allergy. If that is your situation, you will have symptoms such as redness in the gums around the crowns and/or an itching or burning sensation there.

Switching to zirconia? While rare, there are also some instances that have been reported of zirconia allergy. I had one woman write to me who, after going the rounds with several dentists, finally decided that she was allergic to the zirconia in her crowns. I have decided never to tell someone that it’s impossible for them to be allergic to some dental material. Sometimes it seems that putting anything artificial in your mouth carries at least a tiny amount of risk. Wouldn’t that be ironic if you are having no reaction to the palladium and switch to something else only to find out that you are actually allergic to the new material!

– Dr. Hall

Do you have a comment or anything else to add? We’d love to hear from you. Enter your comment below.

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About David A. Hall

Dr. David A. Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does advanced internet marketing for dentists.

Should I get a radiolucent crown or a radiopaque crown?

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Hi Dr. Hall,

I came across your blog and read your very interesting response to a writer with root canal issues. I, too, seek your advice.

I had my lateral and central incisor teeth filed down for a bridge (missing the two teeth in-between). I changed my mind from having the bridge when I learned about some negatives surrounding it, and went back to the partial denture. I have been wearing the temporary crowns for almost 6 months now.

I ended up having to do a root canal on the central incisor and I have been told that the lateral will also need a root canal because it has been exposed for too long and I am getting sensitivity to cold. I am not keen on doing another root canal.

I read about pulp cap in your blog. That’s interesting. Does this need a special dentist to perform?

Could you also tell me which dental crown is radiolucent? I was interested in the eMax crowns (lithium disilicate) but I read that it is radiopaque and as such will block xrays and disallow evaluation of the tooth underneath over time. Could you please tell me if this is so? And if this is so, could you tell me which is the best material for my now vulnerable teeth. I have a lot of anxiety that I might lose them.

Thanks very much for your response.

Marcia


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Dear Marcia,

I hope that you aren’t trying to micro-manage your dentist and make all these clinical decisions for him or her. One thing I worry about in providing all this dental advice is that patients, thinking now that they are armed with sufficient knowledge, will try to tell the dentist what materials to use or will obsess over these decisions. I hope you’re not doing that. When you tell me that you have been wearing temporary crowns for 6 months and have all this anxiety I want to tell you to let go and let your dentist make these decisions. Do the best you can with the knowledge that I provide here to find a dentist you can trust and then trust him or her.

It sounds like you’ve been stewing over these decisions, wearing these temporary crowns for so long, and now one of the teeth became hypersensitive and needed a root canal and another is getting that way. It surely is time to let your dentist finish your case.

You’ve latched onto this question about whether a particular crown material is radiolucent or radiopaque and have decided that you want a radiolucent crown. But you don’t know enough to be getting into the weeds this deeply. There are a number of factors that go into selecting a material for a crown, and you have a very imperfect understanding of even this one factor.

But since you asked, let me explain a little about this issue.

Radiolucency of Crown Materials.

The only type of crown that is radiolucent is a plastic crown, which would be used as a temporary crown. A radiolucent crown is one that doesn’t block the x-rays at all. So yes, you are right, that with the x-rays you can see right through it. The problem is that decay is also radiolucent. Decay would tend to start at the margin of the crown, and with a radiolucent crown it would be impossible to tell for sure what is decay and what is just part of the crown.

But, you say, a radiopaque crown blocks the x-rays and so you couldn’t see under it. Here’s where oversimplification is getting you into trouble. There are many degrees of radiopacity. The ideal would be to have a crown that is partly radiopaque, just like tooth structure is. It doesn’t block the x-rays completely, only partially, so you can see through it to a certain extent but it doesn’t look just like decay.

To illustrate, here is an x-ray of a patient showing four types of crowns plus composite filling materials, and you can see the variations in radiopacity. None of the restorative materials used are radiolucent, for the reason I gave above—radiolucency causes the most complications for diagnosis.
radiolucent and radiopaque crowns
On the upper, starting with the canine on the left, we have a composite filling that is partly radiopaque. Next, on the premolar, is an eMax crown. Yes, it is radiopaque, but it has a very helpful partial level of radiopacity that makes it easy to tell what is going on with the tooth. Next, on the first molar, is a porcelain fused to metal crown. True, you can’t see through it, but you can see what is happening on the margins, which is where you would expect recurrent decay to start. Finally, on the second molar, is a gold crown.

On the lower, the premolar has a composite filling, the first molar has a CEREC crown which is made of lithium disilicate, and the second molar has a gold crown.

My preference for crowns on second molars is gold, even though it is totally radiopaque. I have heard many dental educators and researchers state the same preference. I’m not going to go into all the reasons here for that choice. I only want to make the point that this radiopacity is not a simple cut-and-dried issue nor is it the only factor to be used in the choice of a crown material.

– Dr. Hall

Do you have a comment or a question or anything else to add? We’d love to hear from you. Enter your comment below.

Click here to ask Dr. Hall a question of your own.

About David A. Hall

Dr. David A. Hall was one of the first 40 accredited cosmetic dentists in the world. He practiced cosmetic dentistry in Iowa, and in 1990 earned his accreditation with the American Academy of Cosmetic Dentistry. He is now president of Infinity Dental Web, a company in Mesa, Arizona that does advanced internet marketing for dentists.

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