Expert: Gary Backlund, DMD, MSD - 1/28/2005

Question
Dear Dr.

Recently, I had root canals done on teeths 8 & 9.  Previously, I had porcelain crowns placed on these teeth.  The root canals were uneventful, and I am waiting to have the permanent filling placed inside.  The Endodontist said the crowns are in good shape, but I was wondering if you find that crowns through which root canals are performed are so weakened that they break soon after the root canal.  Also, I have been prescribed Prevident booster - is this safe to use on an ongoing basis, especailly considering you leave it in your mouth before bed.  Thank you so much for taking the time to answer my questions.  It's very much appreciated.

Answer
Hi Raju,

I can certainly understand your concern with the amount of money and time you have invested in your two front teeth. Maybe I can help.

First, Prevident should be no problem, as long as the root canals are sealed and that is what you are waiting for, I assume.

The issue of weakness is a bit more complicated. The crowns themselves are not affected, other than the fact there is now a hole in the back side. They are still plenty strong. The only problem could be if the porcelain were cracked or stressed when the hole was made in the back side. I guess we both just need to take the endodontist's word that they are fine. That being the case, they should serve you well. However, the underlying tooth structure may be a different issue. There are two factors here, first, how much tooth was removed in order to find the canals to do the root canal. In most cases, this is not a problem, but if the endodontist had to do a lot of hunting and poking to find the canals, a fair amount of tooth structure might have been removed and that would tend to weaken the tooth. Second, once the nerve and blood supply has died or been removed, the tooth no longer receives the moisturizer affect of having blood inside the tooth. Over time, the tooth tends to dry our and become more brittle which can result in a weaker tooth.

While I understand your concern, the factors above are really out of our control and there is absolutely no way to predict if you will have problems with these teeth. I know that may not be exactly what you want to hear, but from what you have told me, I would guess you have a pretty good chance of NOT having any future problems.

I hope this helps. If you have more questions, please write back. Good luck!

Gary A. Backlund DMD, MSD