Risks and Complications

What are the Possible Complications of a Root Canal?

Root canal has a high success rate but there are a number of complications that can arise during any routine root canal procedure of which you should be aware. Some of these may be anticipated before hand from studying the X-ray but mostly they cannot be predicted. Fortunately they are not common and do not necessarily need the tooth to be removed. They include:

  • Missed root canals

Most teeth have a standard root formation, 1, 2 or 3 roots and up to 4 canals. Sometimes a dentist can miss a canal if the tooth has more canals than anticipated or if it is in an abnormal position. If this happens bacteria remain in the infected canal and can re-contaminate the tooth.

The actual anatomy of the root canal system is a lot more complex than we often give it credit for. We talk about it in terms of 1-3 canals when the reality is, it is a complex maze of smaller interconnecting canals around these big canals. The root may have large lateral and accessory canals that are difficult to sterilize.

Despite our best efforts using the dental bleach, if sufficient bacteria remain in these canals they could cause the treatment to fail. Unusual shaped roots may make cleaning difficult- if for example they are particularly curved or have canals that join together and then separate.

  • Fractured root or crown

Root treated teeth and those without a blood supply are more brittle and more prone to fracture. The location and extent of the fracture will determine if the tooth can be saved, but more often than not an extraction will be required.

Sometimes root fractures are detected before treatment or during treatment. However sometimes they will go un-noticed or occur as result of a grinding habit, or because a crown was not placed.

  • Re-infection

If for some reason the tooth becomes re-infected the root canal is deemed to have failed. This may be due to insufficient, inadequate cleaning, complex root formations or connections to the outside of the tooth via a fracture or lateral canal.

  • Fractured instruments

This is probably the most common complication that occurs. The tiny files used to clean and shape the canals sometimes break during use and become stuck inside the canal. This can happen when canals are very curved or when rotary files have been used too many times without being changed or with too much speed torque.

If it is a large piece of file it can sometimes be removed immediately with fine forceps and a scaler but generally they are difficult to get out. If this occurs after cleaning has been completed and is only a tiny piece right at the tip, the tooth can often be filled up to this point, incorporating it into the final filling without complication.

If it occurs before thorough cleaning then it needs to be removed. Referral to a specialist to attempt to remove it with a microscope and ultrasonic instruments may be necessary; an apisectomy procedure in rare circumstances may need to be performed.

  • Perforation

Sometimes instruments used to prepare the root canal may accidentally perforate the root during filing. Often this a particular risk when the root of the tooth is very curved or it has a sudden twist. Management depends on the size and location of the perforation and can sometimes be repaired without compromising the long-term success of the treatment.

  • Scelrosed and calcified canals

If a canal becomes sclerosed, (the tooth progressively lays down dentine until the nerve chamber completely closes off), it presents a challenge performing a root canal. Luckily only 13-16% of these teeth result in the nerve dying and give problems, so fingers crossed if this has occurred it will stay silent and nothing will need to be done.

  • Phoenix abscess

An acute flare up following cleaning of tooth that previously had no symptoms.This is not uncommon, it is as if the balance between the bacteria in your tooth and your body is all of a sudden upset and often leads to quite a significant swelling.

  • Immature teeth with incomplete roots

If a child receives a knock to a front tooth sufficient to kill off the nerve before the root has finished growing, there can be a long and difficult road ahead. The root continues to close off for 2-3 years after the crown of the tooth appears in the mouth.

If the nerve dies before the end closes, we are left with an ‘open apex’- a very wide canal that is difficult to treat.

A root filling cannot be placed in the normal way; a barrier to pack the filling against is needed and can only be achieved by repeatedly re-dressing the tooth every 6 weeks until this occurs.

A pediatric specialist or endodontist is generally best to manage this procedure.

If the tooth has associated periodontal problems this can provide a continued source of bacteria and infection and the prognosis becomes questionable.

Other very rare complications include:

  • Altered sensitivity following treatment
  • Allergic reaction to the medicines or materials used
  • Perforation of the maxillary sinus.