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.
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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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