How do I Know if my Root Canal has been Successful?

A successful root canal is not painful (it may take some days to settle as the dentist will have instrumented and aggravated the tissues around the end of the tooth). There are no symptoms or tenderness and mobility has not increased. There is no draining sinus present and ligament surrounding the tooth appears normal.

If a radiograph (X-ray) shows that the dark area around the root of the tooth (periapical radiolucency) has shrunk, compared to when the root canal was originally carried out, this is a good sign and suggests healing but it is important to continue to monitor the tooth.

A root canal is likely to have failed if symptoms begin again and this can happen many years after the treatment was completed. Symptoms may be pain, tenderness on biting, swelling of the gum overlying the roots, increased mobility or the presence of sinus pus. On taking an X-ray, if the area of infection remains unchanged or has grown or even developed at a new site on the tooth, then the options of re-root treatment or extraction need to be considered.

What are the Reasons for Failed Root Canals?

Any root canal complication that permits bacteria to continually enter (such as perforation, root fracture, perio-endo lesion, poorly sealed filling) is likely to result in failure.

Similarly if sufficient bacteria remain in the root canal following completion (as a result of inadequate cleaning by the dentist, missed canals, accessory and lateral canals, difficult root formations, under filing) failure is likely to result.

What should I do if it Happens?

The success rate of root canal is high, but on occasions due to complications or despite our best efforts to disinfect the complex system of multiple connecting canals, the treatment fails. We all have different immune systems and abilities to heal, sometimes unfortunately, it just happens.

If your root canal has failed then you have the following options:

  • Re-root canal treatment. As it sounds, this means taking out the old root canal treatment and trying to re-sterilize and fill the canal or canals for a second time. Often it may be worth considering a referral to an endodotist specialist to have this done.
  • Apisectomy. See below.

Should I have my Tooth Re-root Treated?

If the root canal has failed for whatever reason, is it worth the time, effort, cost and slightly reduced prognosis of having another go? Well, it depends. A high percentage of the re-root treated teeth will be successful the second time around so if you can afford it, I certainly would.

If I had done a root canal on a patient that failed, I am not sure that I would do, or see anything different if I was to attempt it again and for this reason, I personally would refer the case to an endodontist. Perhaps they may be able to identify something I have missed- maybe an extra canal for example. This isn’t always a possibility in some more remote rural areas- so some dentists may try again themselves.

The process for a re-root canal treatment is almost exactly the same- the only difference being the initial stage involves trying to remove all of the gutta percha from each of the canals instead of the nerve. Strong solutions are used to soften and partially dissolve the set material in the canal and then a range of instruments used to help remove this.

If a post has been placed in the tooth to provide support for a crown, this makes a re-root canal treatment considerably more difficult and sometimes impossible. In order to re- sterilise the canal, the post must be first removed and this can be a real pain in the neck and you can risk fracturing the root in the process. Not fun all round. If it is an anterior (front) tooth, an apisectomy can be performed. This is incredibly tough, in fact, almost pointless in molar teeth so it may be better to wave good bye and plan a replacement for the tooth.

A Less than ideal Root Canal needing a Crown?

Sometimes dentists find themselves in a little bit of a dilemma. Let’s say that your tooth needs a crown to protect it and it has a previous root treatment on it, but the root filling is quite short of the apex (we aim to be within 1-2mm of the end on a radiograph) and it doesn’t appear properly condensed..

Does the dentist leave it and just place a crown? Or does he refuse to place the crown unless that root canal treatment is taken out and re-done? You don’t want to build a house on foundations that aren’t solid and you don’t want to place a crown on a root canal that is more likely to play up.

The reality however, is not quite as simple as that. The success of a root canal is dependant on eliminating the bacteria from the root canal system and sealing it; thus preventing further bacteria getting in. The procedure used and the technique for the root canal is very important. Did the previous dentist perform the procedure with an efficient aseptic technique? Was the canal adequately sterilized before filling? It is impossible to say.

Furthermore, an apparently well- filled root canal on an X-ray may have been poorly sterilized, bacteria remain and the treatment fails. Conversely a poor root filling may have followed exquisite technique and disinfection and be successful. It is a tough one. The X-ray isn’t the whole story.

Studies have shown that a poor root filling with a good restoration that seals the tooth properly on the top is likely to be more successful than a great root filling with a poor restoration. Ideally of course we want both.

Ultimately there is no way of knowing. A very large area on the X-ray is likely to indicate a failure, as is pain associated with the tooth. Let’s say you, as the patient have had no trouble since it was done 5 years ago, but on the X-ray there is small area of apparent infection.

Now it is important to understand that if it is a new dentist who is seeing this for the first time, then it may appear on first sight as a problem. It does however need to be considered, that as the dentist is only seeing this at a particular point in time, the area may be unchanged or has healed up somewhat since it was completed.

Ideally the dentist would get hold of the X-ray previously taken when the root canal was finished and compare this with the current one, but this is not always possible.

At the end of the day, the only real way to ensure the optimum result is for the dentist to open up the tooth under aseptic conditions and re-perform the root canal. Yes- this means more cost and yes- another root canal but it provides the most consistent successful result.

If a post is going to be placed in the tooth then because of the difficulty in removing this, if there was a problem, a re-root treatment would be sensible.

But it has never given you any trouble you cry. Well, it’s up to you- I am just trying to help you understand the predicament for what it really is. You could re-root treat the tooth apparently perfectly and get more problems than you have now- the theoretical risk exists. If it was my tooth which had been root canal treated 6 years ago and I hadn’t heard a peep from it, plus there was no infection on the X-ray, I probably wouldn’t mess and just go ahead and place the crown. You are not disturbing anything in the depths of the root so I wouldn’t expect anything to change.

My Root Canal Filling has been Exposed?

What about if the root canal filling material has been exposed because the top fractured off the tooth or the filling fell out?

We see this quite commonly, and it presents another dilemma. It won’t take long for bacteria in saliva to seep down the side of the canal and reinfect the root system, so the best thing you can do is immediately see a dentist and get the top sealed to protect it. If you leave it 4 months, guaranteed, that canal is no longer sterile and it should be re-root treated. That’s my thoughts on it, but different dentists will, as I have said many times before, recommend different courses of treatment.

If a crown is placed on a tooth that subsequently deteriorates, giving rise to pain, a root canal can be performed through the top of the crown. Depending on the type of the crown, the access that is created to do the treatment may simply be filled and a new crown not needed.

Similarly, a re-root treatment can be performed in this manner- it is just a slightly more difficult procedure.