Can Root Canals Fail?

Can Root Canal treatment be Guaranteed?

No dental treatment is immune to the possibility of failure, and that certainly includes root canals. Even though success rates with endodontic treatment are as high as they’ve ever been, it is still important to know what some of the potential causes of failure are, what they mean, and how they can be addressed.

It is also important to break down root canal failure into two categories: failures that occur due to the nature of the procedure, and those that cause previously successful root canals to fail. Let’s examine the former group first.

Root canal treatment is a highly complex operation and requires years of education and experience to effectively deliver. There are dozens of variables that can cause root canals to fail even as the procedure is underway. Many of them are unavoidable.

Consider the following scenario: your dentist informs you that a tooth you have been experiencing pain and sensitivity with has a deep crack in it, one that may be threatening the nerve of the tooth. For that reason, he or she refers you to an endodontist for evaluation and treatment. The endodontist recommends root canal treatment, and the procedure begins. However, while accessing the pulp chamber and cleaning out the inside of the crown of the tooth, the endodontist notices that the crack in the tooth is, in fact, deeper than originally believed. So deep, in fact, that it has spread to the floor of the tooth beneath the bone or into one of the roots themselves. This situation, unfortunately, prevents successful completion of a root canal. Therefore, it may not be accurate to say that root canal failed in this case, only that there are circumstances that can derail treatment, and that some of them may be found only by initiating treatment, to begin with.

But suppose the tooth was not cracked and the endodontist completed the root canal. The only problem is, you are still experiencing pain in the days and weeks after treatment. This is often attributable to incomplete cleaning of the canals or failure to remove all of the dental pulp. This can happen for a few reasons. First, many teeth have curved roots or canals with complicated anatomy. Aside from the operator’s own knowledge and clinical expertise, there is no test to ensure that all infected pulp has been removed. Therefore, it is possible that some diseased tissue can be left behind—the very tissue that was causing pain in the first place.

There may also be “hidden” canals that are not part of normal anatomy and are missed. Still, other canals may branch off from main canals and be so tiny that they are essentially undetectable. The bottom line is that any amount of diseased tissue left behind can cause lingering pain and thus the root canal is considered to have failed.

It also bears mentioning the operator error can contribute to root canal failure. If a cleaned canal is not obturated (filled) all the way to the canal opening, there exists the potential for infection to reoccur. If canals are perforated (i.e., have a wall pierced by an instrument), the procedure cannot be completed. Again, though, these sorts of “iatrogenic” problems (those caused by the operator) are rare and reinforce the idea that a root canal specialist is probably the best doctor to see for root canal treatment in the first place. Another reason you might seek the endodontist is if you have a failed root canal treatment that has been done by another dentist in the past, and now it needs to be retreated (redone) by a specialist to improve the quality of the treatment and save the tooth.

There are other factors that can cause a root canal to fail after it has been successfully completed. Some of these may even happen years down the road. For example, if a root-canal-treated tooth develops a cavity that goes undetected or untreated, it can allow bacteria to re-enter the tooth and potentially cause infection. Similarly, a dental crown that was placed on the tooth incorrectly may allow bacterial leakage or a break in the crown may do the same. Finally, a root-canal-treated tooth may fracture in a way that makes the tooth non-restorable. Instances of decay can usually be addressed, whereas fractures—depending on the severity—can not. In those cases, extraction is the only option. This leads us to another important question.


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