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Dentistry/Failed root canal under bridge


QUESTION: I have a bridge which spans across my three front teeth.  One of the front anchor teeth has an old root canal, possibly some 20 years old.  Xrays show a dark shadow at the root of this tooth and it has been quite uncomfortable to bite for a few weeks now.  The dentist plans to try carrying out another root canal procedure again to clear out the infection at the end of the root, put a post in, and hopefully save the tooth and will try to complete the task keeping the bridge intact.  As you can appreciate I am quite concerned about having this done as there is a risk of the bridge fracturing - albeit there is a metal plate at the back of the part of the bridge in question.  Over the last week the discomfort has subsided somewhat, the bite now seems almost normal - should I go ahead with the treatment, or is there an advantage to waiting to see if the condition improves.  I am told that once there is a shadow at the end of the root it can never ever go away permanently - is this correct.  Thank you for your help.

ANSWER: Hi Margaret,

I'm sorry to hear all this is going on. I can certainly understand your concern. Let me try to help.

First, the bad news. You have been told correctly. Once a root canal fails, it will not heal itself. They tend to flare up, then settle down, sometimes over & over. Sometimes the flare up can be with extreme pain and swelling. Once the diagnosis is made, there is no point in waiting as it only sets you up for problems down line.....sorry for the news.

Now the good news....doing a root canal retreat through a bridge, especially one that is a front tooth and with a metal back of the bridge, is usually pretty easy. The biggest problem might be correcting whatever went wrong the first time so you don't need to deal with all this at some point in the future. The bridge itself should do just fine. You didn't say if a specialist is doing your treatment, but it might not be a bad idea since retreating a root canal has a lower long term success rate than doing it the first time. Therefore, a specialist ability might be worth it...just a thought.

I hope this helps set your mind at ease. I'm sure all will come out just fine.

Gary Backlund DMD, MSD

---------- FOLLOW-UP ----------

QUESTION: Thank you so much for your swift response - it really is appreciated.  May I please just ask two more follow up questions.  You say that delaying could cause further problems down the line, does this mean if I delay a month or so it could cause the infection to spread further and cause possible problems should I ultimately loose the front tooth if I wanted an implant?  Also the dentist who is doing the treatment is not a specialist endodontist, but he has all of the specialist magnifying equipment and seems fairly confident - would you still recommend seeking out a specialist endondist?  Thank you once again.

ANSWER: Hi again Margaret,

When I talked about delaying treatment, it was in response to your idea of waiting all together hoping things would improve and they won't. Waiting one month is probably no big deal, but you do have an unstable situation and you could have swelling and pain overnight, so the sooner you get this dealt with, the better. The main risk is just pain & swelling. There won't be any long term effects that would compromise treatment in the future whether a new root canal or an implant. You don't need to worry about that.

My suggestion for an endodontist was just that you seemed worried about your bridge. Endodontists are more experienced in dealing with these situations because we have had an additional 2 years of training and that's all we do everyday as opposed to a general dentist who does all phases of dentistry. I probably do more root canals in one month than most general dentists do in a year. Your chances of having problems go way down and success rate way up when done by a specialist. Many general dentists are really good at root canals and can provide the treatment at less cost than an endodontist. However, if there are complications, they may not have the experience to solve the problem. Your dentist might be fine, but if you want the best chance of a good outcome, an endodontist would be my choice.

Hope this clarifies what I was trying to say. Good luck!

Gary Backlund DMD, MSD

---------- FOLLOW-UP ----------

QUESTION: Following your good advice I have now had the root canal re-done yesterday through the bridge by an Endodontist.  All went well at this stage, there appeared to be no complications during the process and I now have a temporary dressing through a hole in the back of the bridge which covers my front upper teeth.  It would appear that there has been an infection at the root that has caused some slight bone loss but he is hopeful that now the treatment has been done the bone should re-form.  Please can you advise what precautions I should take with this bridge now, should I not be biting on my front teeth at all until after the next stage, or even after that, I had read that the front tooth bridge will be weakened by the fact that the tooth inside has had a re-root canal done and the bridge may have been weakened by the process.  Thank you.

Hi again Margaret,

I'm really glad to hear all went well and thank you for the feedback...I rarely receive any.

Assuming that the endodontist did not have to do a lot of drilling or tooth removal to get back inside the tooth, which is normally the case, your bridge should do just fine. The filling you have in the back is designed to just cover the hole until you get back to your regular dentist, which you should do as soon as possible. That temporary will hold up well and the only thing I would suggest you avoid would be very sticky foods like gum or chew caramels so the filling doesn't get pulled out. Other than that just eat and brush normally.

Long term, your dentist will pit a filling in the hole and your bridge should hold up just fine. Once again, I wouldn't worry too much about it coming loose. It is possible, but usually only occurs when the tooth under the bridge is very weak or the dentist had to make a really large hole to do the root canal.

I really think all will be fine. Good luck!

Gary Backlund DMD, MSD


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Gary Backlund, DMD, MSD


I am an Endodontist ( root canal specialist ) and can answer questions about root canals and their treatment. I cannot diagnose or treat online, but can answer general questions. I have been a specialist for 25 years and am Past President of the Washington State Association of Endodontists.


25 years practicing as a specialist

American Association of Endodonists, Past President Washington State Association of Endodontists.

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