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.
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
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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.
Clark R says
Wow Dr,Hall great empathy, excellent explanation thanks!
Gary Manning says
I have 16 crowns. All opaque except one. Two teeth so far have rotted beyond help and have to be extracted and implants placed. Gee, what a big help only being able to see the margins. My margins were fine, but due to bad dentistry either with the manufacture of the crown or seating it, the teeth inside the crowns rotted from the top and decay was not detectable via x-rays. Only because of an open margin, the dentist could probe high enough above the margin to find the decay.
Had I had ANY radiolucent crown, I could have saved my teeth! So, no, I won’t leave it up to the dentist and will micro-manage these most expensive products because I want the best chance of detecting caries.
I respect your knowledge and dedication. But I’m going to lean on my end-user experience of decades of owning and dealing with these damned crowns. You’re the pro on the OEM side, I’ll be the pro on the end-user side.
– Gary Manning
Response by Dr. Hall:
Thank you for your insight, which is certainly helpful. However, I think you miss part of the point that I was trying to make, which is that there are more choices than radiolucent and radiopaque. A completely radiolucent crown makes diagnosing recurrent decay difficult, because the decay is radiolucent, just like the crown, and it’s hard to tell one from the other. Yes, a completely radiopaque crown (metal or porcelain-fused-to-metal) will block x-rays and the dentist will be unable to see, on the x-ray, what is going on under the crown. But many dentists are now placing crowns that are metal-free and are partly radiopaque. These make x-ray diagnosis the clearest. So if you tend to have serious problems with recurrent decay, what you should be asking for is a metal-free crown that is partly, but not completely, radiopaque. I think that would be a reasonable request, based on your history.
– Dr. Hall