What Causes Root Canal Failure . .

. . And what can be done to prevent a failed root canal.

Root canal failure is always disappointing. A failed root canal means the dentist will be upset, because he has spent a lot of time and intense concentration on doing the root canal.

And of course the patient will be disappointed, because they have spent a lot of money on the procedure, as well as sitting in the dentists' chair for a couple of hours. But what exactly IS root canal failure? Is the dentist always to blame?

Of course not. Not always. But sometimes. Lets take a look at how root canals can fail, and whether it could be prevented.

Root Canal Failure

You get a root canal failure when a tooth that has had root canal needs MORE treatment.

WHY would it need more treatment? BECAUSE there's a problem - nearly always, it's pain or discomfort when biting on the tooth.

How can a tooth hurt when it's had root canal, and there's no nerve in the tooth?

SIMPLE - the tooth has become infected. Somewhere, somehow bacteria have got inside the root canal system of the tooth and set up an infection.

SO it's sore, painful, and you need something doing about it. The options are limited - either a RE-TREATMENT with a specialist in root canal work (an endodontist), OR simply get the tooth pulled.

BUT what are the complications with root canal that make failure a possibility? Let's start right at the beginning, from the dentist's point of view. What does he have to do to get the highest chance of a successful root treatment?

First off, the dentist has to get the right tooth. It seems obvious, and usually it's clear enough, but not always. At times, it can be very difficult to judge which of two or three neighboring teeth is the cause of the toothache.

BUT when someone is in severe pain, you have to take your best shot. Very rarely, it's possible for the dentist to start treatment on the wrong tooth. To correct this, the dentist should start treatment on the right tooth, and of course complete the root canal on the one he started first.

Second, the dentist has to find the little space inside the middle of the tooth. Again, it sounds easy, but when you're the one holding the drill, you want to be sure you're drilling in the right direction!

Occasionally, if a tooth is tilted or twisted a little, it is possible (although rare) to drill out of the side of the tooth. This is more difficult to fix. If the dentist realizes his error quickly, the perforation can usually be repaired with a special cement called MTA.

root canal failure

Third, assuming the dentist has got the right tooth and has located the little space down inside it, he needs to clean it out thoroughly. He needs to find ALL the little spaces, and he needs to make sure they are completely cleaned out.

If he doesn't, bacteria can get in there and set up an infection. This is probably the most common cause of root canal failure. Not finding all the canals, and not cleaning them enough.

It's easy to miss one of the canals, and it's difficult to make sure the ones that ARE detected are completely cleaned out. It takes a lot of time, and intense concentration on the part of the dentist. He can't hurry things.

Fourth, once the dentist HAS located all of the canals and cleaned them thoroughly, he has to seal them up to prevent bacteria getting in. This is a little easier than the cleaning step, but there is still plenty of room for error! This is probably the second-most common cause of a failed root canal. Not getting a good seal, all the way to the tip of the root.

The fifth step is getting a good seal over the top of the root filling. Again, this is to prevent bacteria getting in. On a molar tooth, this frequently means getting a crown (a cap) over the tooth. On a front tooth, a carefully sealed tooth-coloured filling is usually enough.

How do you know a root canal has failed?

You feel it.

The tooth becomes uncomfortable to put pressure on. You can't bite on it properly. If the dentist has missed a root canal, you might feel pain on hot food or drinks.

The only solution is to do the root canal over again. If the first treatment was difficult, owing to root canal complications, your dentist will probably refer you to a specialist. (An endodontist).

There are times when the root canal is doomed to failure, no matter what the dentist does. The two most common situations are if the root itself is cracked or broken, or if the tooth is so badly broken down that it's impossible to get a good filling or cap over the top. Unfortunately, the only solution is to remove the tooth.

Sometimes a patient will come to my office with a failing root canal that they had done elsewhere, and ask me if a failed root canal is dental malpractice. The answer is "no, not necessarily".

As you can see, root canal treatments are very complex, and there is potentially a lot that can go wrong. I have rarely seen a failing root canal that I could directly say was due to malpractice. If you think you have a root canal that was not done properly, you really need to get a second opinion from an endodontist.

Research shows that root canal failure is relatively rare. Most root canals have a success rate of over 90%. You are more likely to get a failed root canal in a back tooth than a front tooth, but it is still the best option in most cases, over getting the tooth pulled. That leaves you with a gap, or expensive bridgework or implants!