Why Root Canals Fail? | The Usual Suspects

Why Root Canals Fail?

If you’ve ever needed to have a root canal redone, you may be wondering why a root canal would fail. Root canals, much like all the other work done in dentistry and endodontics, have the potential to fail, but generally it is for only a few main reasons. While there are a myriad of ways dental and endodontic work can fail, generally it falls into three main categories.

The first reason why a root canal can fail is if the person completing the root canal did not find all the nerve spaces within the tooth. When we do root canals, it is imperative that we locate all the different roots and the different canals. Teeth can have a varying number of nerve spaces, depending on how the tooth developed, and anyone doing a root canal needs to be able to locate all the nerves.

Endodontists work under a microscope, so they can find even the smallest nerve spaces and make sure they are properly treated. Very often we see missed nerve spaces in the premolars and molars, since these teeth have more than one nerve in them. If you are hoping to have a successful root canal, it is strongly suggested you see an Endodontist, or a root canal specialist, so that they can locate all the nerve spaces. Furthermore, even if a clinician has located all the nerves, if they have not sufficiently cleaned out all the nerve tissue, the root canal can fail. Leaving any nerve remnants behind will cause a root canal to fail rapidly, because the tooth is not internally clean. Once again, Endodontists work under a microscope and have advanced endodontic irrigation techniques, so the root canals are as clean as possible.

The second reason why a root canal can fail is if there is decay that has formed in the tooth. All dental work, including endodontic work and root canals, are susceptible to decay. Decay is filled with different types of bacteria, which are so microscopic they can work their way into the root canal and cause it to be contaminated. They have found in multiple studies that even extremely well-done root canals can fail in the presence of bacterial contamination. The entire purpose of cleaning out a tooth for a root canal is to eliminate bacteria, but if bacteria continues to flood into the tooth, this will cause the root canal to fail. Ways this can occur is if the tooth with a root canal develops a cavity, if the crown on top of the root canal is not done well, or if the temporary filling placed in the root canal after the treatment is not replaced with a permanent filling. In addition, when doing a root canal, the clinician should always be using a rubber dam.

A rubber damn protects the tooth undergoing endodontic treatment from the bacterial contamination from the patient’s saliva. If a clinician attempts to do a root canal on you without a rubber dam, this is a red flag and you should seek the advice of a different clinician,
preferably an Endodontist. Endodontists are up to date with the standard of care, and a root canal specialist will never do a root canal without a rubber dam.

The final reason why a root canal can fail is if there is catastrophic fracture of the tooth. Teeth are strong, but they can crack under significant force. Teeth that have had root canals can crack in two ways. First, the crown of the tooth may crack under large amounts of force – such as patients who are grinding against their root canal without having a mouthguard. Clenchers will commonly present having cracked a root canal tooth. If you have a root canal done, a good way to prevent fracture of the crown is to have a mouthguard fabricated to wear at night. This will prevent the patient from putting undue force on the root canal and allow for the best success for the tooth and the endodontic treatment.

Your Endodontist may even recommend you see your general dentist after the root canal to get a mouthguard.

The second type of fracture is a spontaneous root fracture. Unfortunately, roots can also crack over time, due to wear and tear on the tooth and the root canal. If the root canal tooth begins to fracture in the root, which is uncommon, it will generally mean the tooth has to be extracted. Thankfully, even if a root canal begins to fail, it can often be saved by having an Endodontist complete a retreatment. Retreatments are when a clinician redoes a root canal and updates it. Retreatments are best handled by Endodontists or root canal specialists, because they have extra training and tools for these types of endodontic treatments. In addition, it is sometimes possible to fix a failing root canal by doing a procedure called an apicoectomy, which is essentially a root canal surgery. In this procedure, the Endodontist removes the piece of the root canal tooth that is still infected to save the tooth. If you have a failing root canal, please seek the advice of a trained root canal specialist to see if your tooth can be saved.