Expert: Frederick R. Liewehr DDS, MS, FICD - 11/3/2004

Question
My dentist recommend that I have a crown placed on a bottom chewing tooth because it had lots of "cracks".  Even though I was experiencing no pain or problems with the tooth I had the crown done. It is now two months since the placement of the permanent crown and I am experiencing pain from hot and cold and chewing that I didn't have before the crown was done. I am now told that a root canal is needed.
I am concerned that I will have a filling (for the root canal) in a crowned tooth, not something I would expect to happen -- will the filling in the crown last as long as a normal filling or should I expect the dentist to replace the complete crown once the root canal is done?


Answer
Hi,
    Unfortunately, your question is one of those that are impossible for me to adequately answer without seeing you. All I can do is guess at what might be going on, so you have to take it for what it is worth.
    First, I don't know what these "cracks" were. There is something we call "cracked tooth syndrome", which usually has symptoms of pain on biting, and pain when eating or drinking cold foods. Now, these symptoms can occur due to other causes as well, but usually you will know if you have it because one particular tooth will hurt when you get food in your mouth in just such a way that you bite mostly on that tooth. So, if you had this, you would probably recognize it from my sorry attempt to describe it. In that case, sometimes restorative dentists will recommend placing a crown, to avoid the tooth from further splitting. Occasionally this works; often you wind up being more sensitive afterwards and need the root canal that probably should have been done in the first place.
    However, if you had no symptoms before, then it is hard to know why the crown was placed. You cannot diagnose cracks by looking; almost all posterior teeth have what can appear to be cracks that are in reality no problem. It may have been that the tooth was broken down from previous decay and/or big fillings. In that case, a crown may have been recommended to prevent the tooth from cracking and giving you the above symptoms. Sometimes these teeth, when crowned, become sensitive, too. In fact, a predictable number of crowned teeth require root canal therapy, because remember that a lot of your tooth needs to be removed in order to place the crown, and teeth really don't like being cut up.
    There is also a possibility, though I hate to mention it, that the crown was not done well and does not fit properly. In that case, the interface between the crown and the tooth is not tight, and your saliva, food, bacteria, etc. is leaking into the tooth. This will make the tooth sensitive, and in time will cause decay. In this case, the solution is to remake the crown properly, not mask the symptoms by removing the nerve so you don't realize you have a problem. After all, that is what the nerves are for. There is no way I can diagnose this by e-mail, so someone has to examine you and let you know what is going on.
    As for doing the root canal, the endodontist would need to get to the inside of your tooth, so that can be done in one of two ways. Either he can make a hole through the crown, and patch it afterward, or he can remove the crown. Removal sounds better, but crowns can be difficult to impossible to remove without destroying the crown (and preventing that is why you are removing it in the first place), and occasionally the tooth can be broken in the process. So, which to do is usually a judgement call. Do you need this to be done? Not really; your dentist can patch the crown and it will be good as new from a functional standpoint. However, it may not look exactly like it did before. But that is better than a broken tooth.
    So, good luck. I hope everything works out well for you.

Dr. Liewehr