What is root canal treatment?

Root canal treatment - also called endodontic treatment - is a dental procedure used to save an infected or badly decayed tooth. It is a common procedure that has been used for decades to save teeth that would otherwise have to be extracted.

A healthy tooth

A healthy tooth consists of the crown - the part you can see that sits above the gum line - and the roots, which hold the tooth in the bone and are hidden below the gum line. The surface of the crown is covered in a hard outer shell of enamel. Beneath this layer is the dentine, which is softer and sensitive if exposed. In the centre of the tooth lies the pulp. This consists of nerves and blood vessels that supply the tooth and connect to other nerves and blood vessels in the jawbone.

The pulp is important when the tooth is growing and developing. Once it has fully formed, the pulp's main purpose is to give the tooth feeling so it can detect temperature changes in the mouth. A fully-developed tooth can function perfectly well without a pulp. It no longer feels hot or cold, but will still feel biting pressure and function normally. Root canal treatment involves removal of an infected or damaged pulp from within the tooth.

Crown

Also commonly called a cap. This is an artificial shell of porcelain, or metal, or both that is made in a laboratory designed to fit over all or part of the surface of a tooth. It restores the tooth’s form, function and desired colour and is permanently cemented to the underlying prepared tooth.

Nerves

One or more fibres that transmit signals of sensation and motion between the brain or spinal cord and other parts of the body.

Reasons for having a root canal

When a tooth is badly damaged or infected, the alternatives for treatment are either root canal treatment or extraction (removal) of the tooth. Root canal treatment means that you will save the tooth. Removing the tooth means:

  • You will have fewer teeth to chew and speak with;
  • The tooth that normally sits opposite (above or below) the extracted tooth will now be useless. Effectively, you will have lost the use of both teeth;
  • Nearby teeth can move or drift when a tooth is removed. This can interfere with the bite, make cleaning difficult and lead to further tooth loss;
  • When a number of back teeth are removed, there is a loss of support to the bite and the remaining teeth must take all the chewing forces. Front teeth are not designed to cope with these forces and can often break down quickly. They can also drift outwards (splay) and become protruded;
  • When a tooth is lost, a certain amount of bone that supported the tooth will resorb (be reabsorbed) and disappear over time. This will affect the bone supporting any adjacent teeth. These neighbouring teeth can become loose as they lose some supporting bone, which can result in premature loss of these teeth as well, and;
  • Cheeks and lips supported by the underlying bone can appear sunken over time, as the bone that supported the lost tooth disappears. This is more noticeable where there are multiple missing teeth.

While there are several ways to replace a missing tooth, it will never be more than a substitute for a natural tooth. A natural tooth is usually much stronger, more efficient for biting and chewing and easier to clean and maintain than an artificial one.

Root canal treatment has a high rate of success if an appropriate assessment is made before treatment. If you take good care of a root canal-treated tooth, it can last you for many years, possibly the rest of your life.

Signs and symptoms

A tooth will need root canal treatment when the pulp (nerve and blood vessels inside the tooth) has become infected, damaged or has died. This can happen as a result of:

  • A deep cavity;
  • Repeated deep dental work to the tooth;
  • Trauma, such as a knock to the tooth;
  • A crack in the tooth;
  • Extreme wearing down of the tooth, and;
  • Breakdown or leakage of an existing filling or crown.

Symptoms of an infected pulp include:

  • Pain;
  • Sensitivity to heat or cold;
  • Tenderness in the tooth when chewing;
  • Discolouration of the tooth;
  • Swelling or soreness in the gums surrounding the tooth, and;
  • A 'pimple' that appears on the gum near the tooth.

An infected pulp will die if it is not treated. This can result in severe pain and the infection will spread to the bone at the ends of the tooth roots. Sometimes the tooth will stop hurting once the pulp has died and the infection has spread into surrounding bone. The bone is destroyed by the infection and will only heal once root canal treatment is done or the tooth is removed. Antibiotics alone will not cure this type of infection.

Antibiotics

Chemical substances that kill or suppress the growth of bacteria.

Crown

Also commonly called a cap. This is an artificial shell of porcelain, or metal, or both that is made in a laboratory designed to fit over all or part of the surface of a tooth. It restores the tooth’s form, function and desired colour and is permanently cemented to the underlying prepared tooth.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Nerve

One or more fibres that transmit signals of sensation and motion between the brain or spinal cord and other parts of the body.

Cavity

1. A hollow compartment within a body part. 2. Loss of tooth structure caused by dental decay.

Methods for diagnosis

After thoroughly inspecting the tooth and taking an X-ray, your dentist or endodontist (a dentist that specialises in treating the roots of teeth) will decide if the tooth is suitable for root canal treatment.

X-ray

A scan that uses ionising radiation beams to create an image of the body’s internal structures.

Types of treatment

Root canal treatment aims to remove the infected pulp, disinfect the canals inside the tooth and fills them with an inert material that will prevent any further infections. The sooner root canal treatment is started on an infected tooth, the higher the chance of success. A tooth with a long-standing infection and a large abscess has a lower chance of success.

What happens during the procedure?

A local anaesthetic is injected to numb the tooth and block pain. A sheet of rubber, called a 'rubber dam' is placed around the tooth. This isolates the tooth, keeping it clean and dry during the procedure and preventing cleaning agents used in the tooth from flowing into the mouth. 

The pulp is reached by drilling an opening in the tooth. If it is a back tooth, it is drilled through the top. If a front tooth is being treated, the pulp is reached through the back of the tooth so that the opening is not visible from the front.

Special instruments called endodontic files are used to remove the inflamed or infected pulp from each canal of the tooth. The canals are enlarged and shaped and flushed out with antibacterial solutions. Several X-rays may be taken during the treatment to check the length and shape of the canals.

An antibiotic paste is usually placed inside the tooth to help clear any infection and inflammation. This is usually kept inside the tooth for a few days and the opening sealed with a temporary material. Root canal treatment can take several visits to complete. The number of visits depends on the severity of the infection, the number of canals inside the tooth and the degree of difficulty in treating the tooth.

When the dentist or endodontist is satisfied that all the pulp has been removed and the tooth is free from infection, the canals will be filled. A rubber-like material is used to fill the canals and a filling is placed to seal the opening to the tooth.

Some people can experience pain or discomfort in between visits while having root canal treatment. Mild pain relief may be needed, such as paracetamol or ibuprofen, until the tooth settles down.

Root canal treatment.Root canal treatment procedure. 

Final restoration of the tooth

Once the root canal treatment is complete, a temporary filling may be needed while the bone around the tooth heals. This can take some time and several follow-up visits may be needed to check the progress of the tooth. X-rays are usually taken periodically to monitor the bone healing.

A root canal-treated tooth usually has an increased risk of fracture. For this reason, your dentist may recommend that a crown or a 'full-coverage restoration' is placed over the tooth soon after treatment to help hold it together and lessen the risk of fracture.

In some cases, your dentist may place a metal band around the tooth to hold it together while it undergoes root canal treatment, and while waiting for the bone to heal after treatment, before placing a crown on the tooth.

Making a crown for the tooth usually involves two appointments. At the first appointment, the tooth is prepared for the crown by shaving back a small amount around the tooth and taking an impression to send to the dental laboratory. A temporary crown is made for the tooth while the laboratory makes the permanent crown. At the second visit, the temporary crown is removed and the permanent crown fitted.

A crown is typically made of either porcelain or gold and is considered the most effective way to restore a root canal-treated tooth that has been heavily broken down. A crown will restore the normal shape, colour and function of the tooth. It will also help seal the tooth from any leakage.

In some cases, instead of a crown, a 'full-coverage restoration' may be suggested to help hold the tooth together and restore function. This is usually a cheaper option and requires only one visit. The restoration is made from amalgam (silver filling), or tooth-coloured resin-composite material. While not as strong as a crown, it can still serve you well for several years.

Abscess

A swollen area of tissue containing a build-up of pus.

Antibiotic

Chemical substances that kill or suppress the growth of bacteria.

Crown

Also commonly called a cap. This is an artificial shell of porcelain, or metal, or both that is made in a laboratory designed to fit over all or part of the surface of a tooth. It restores the tooth’s form, function and desired colour and is permanently cemented to the underlying prepared tooth.

Infections

Entry into the body of microorganisms that can reproduce and cause disease.

Inflammation

A body’s protective immune response to injury or infection. The accumulation of fluid, cells and proteins at the site of an infection or physical injury, resulting in swelling, heat, redness, pain and loss of function.

Local anaesthetic

A type of medication that, when administered to an area, creates a localised loss of sensation by blocking nerve activity.

X-rays

A scan that uses ionising radiation beams to create an image of the body’s internal structures.

Potential complications

Root canal treatment, as with all other medical and dental procedures, is not without its risks. There are a number of complications that may occur during and after treatment. Some teeth are at greater risk than others. Your dentist or endodontist will be able to advise you of the risks that may apply to your particular situation.

A root canal-treated tooth can fail due to:

Reinfection

The aim of root canal treatment is to clear away any infection inside the tooth. Occasionally this infection persists and an abscess forms in the bone around the tooth, or the tooth becomes reinfected. A leaking filling on top of a root canal-treated tooth can cause bacteria to leak into the roots and cause a reinfection. It is important to have your tooth restored properly with a new filling or a crown after a root canal treatment to minimise the risk of reinfection.

It is possible to redo the root canal treatment in a reinfected tooth, although the rate of success decreases with each new treatment. Your dentist or endodontist will be able to advise you if there was an obvious reason for the failure of the treatment and whether there is a good chance of success with another treatment.

Cracked tooth

A root canal-treated tooth may not be as strong as a normal tooth, particularly if it has been heavily filled in the past. The tooth can be more prone to breaking and cracking as a result. A small chip off the tooth can usually be restored; however, if the tooth cracks vertically beneath the gum line, it cannot be fixed. Extraction is then the only solution. It is important to have a root canal-treated tooth properly restored with either a crown or a full-coverage restoration that will hold the tooth together and help prevent breakages.

Further decay

Any natural tooth can develop tooth decay if plaque and food are allowed to collect around it. A root canal-treated tooth is no exception. If the tooth starts to decay, it will not cause any pain as the nerve inside the tooth has been removed. A root canal-treated tooth that has decayed may cause a reinfection of the root canal treatment, or may weaken the tooth so much that it needs to be extracted. It is important to clean all your teeth thoroughly to prevent tooth decay and visit a dentist regularly to have your teeth and gums checked and maintained.

Ongoing pain

Some people can experience pain during their root canal treatment and even for some time after treatment is completed. Your dentist or endodontist will be able to recommend pain relief for you. In some cases, minor discomfort or some tenderness in the tooth can linger for some months as the infection clears and the tooth settles. Talk to your dentist if this concerns you.

File fracture

Thin metal files are used to clean the canals in root canal treatment. As these files are very fine and often need to pass through bent or curved canals, they can sometimes break. A broken file can be difficult to remove and you may be referred to a specialist endodontist for this procedure.

If the file cannot be removed, the long-term success of the root canal treatment can be affected. This will depend on whether the canal was infected and whether it had been cleaned before the file was fractured. Your dentist or endodontist will discuss the situation with you in detail.

Discolouration of the tooth

Teeth that have had root canal treatment can often darken with time, becoming grey or yellow. While this colour change may not be of concern in a back tooth, many people are unhappy about a darkened front tooth. Discolouration can be treated by bleaching the tooth either internally or externally, or by having an artificial crown or veneer made to fit over the tooth. 

If a front tooth has large fillings and is fairly weak, then a crown may be advisable to give the tooth some strength and support. If a tooth is only lightly discoloured and otherwise intact, then bleaching may be adequate to improve the colour. Your dentist can discuss which option is best for your tooth.

Abscess

A swollen area of tissue containing a build-up of pus.

Bacteria

Microscopic, single-celled organisms with DNA but no definite nucleus. Bacteria are the cause of many human diseases.

Crown

Also commonly called a cap. This is an artificial shell of porcelain, or metal, or both that is made in a laboratory designed to fit over all or part of the surface of a tooth. It restores the tooth’s form, function and desired colour and is permanently cemented to the underlying prepared tooth.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

Nerve

One or more fibres that transmit signals of sensation and motion between the brain or spinal cord and other parts of the body.

Plaque

A thick, sticky, soft mass that adheres to the surface of the teeth and gums and is the primary cause of tooth decay. It is composed of bacteria, food particles and mucin derived from the saliva. It cannot be rinsed off with the flow of water or saliva.

Tooth decay

The process of destruction of the tooth’s surface due to the accumulation of bacterial plaque, which produces acids that break down the tooth structure. The decay forms dark patches on the teeth, which grow into holes or cavities and can become painful if left untreated.

Veneer

A layer of tooth-coloured material, either porcelain or acrylic, that is directly attached to an original tooth.

Prognosis

Treatment of an infected tooth is not always successful. Generally, root canal treatment has a success rate of around 90-95% [1] - however, this depends on a number of factors such as:

  • The extent of any infection in the tooth and surrounding bone;
  • The individual anatomy of the tooth or the degree of difficulty in accessing the canals inside it;
  • The amount of healthy tooth structure remaining in the tooth, and;
  • The level of experience of the dentist or endodontist treating the tooth.

Infection

Entry into the body of microorganisms that can reproduce and cause disease.

1. Salehrab R. and Rotstein I. (2004) Endodontic treatment outcomes in a large patient population in the USA: an epidemiological study. Journal of Endodontics 30:846-850.

Prevention

The best way to reduce your chances of needing a root canal is to practise good oral hygiene, because for the pulp of the tooth to become infected, the tooth has to somehow be compromised, such as by the formation of cavities.

1. Salehrab R. and Rotstein I. (2004) Endodontic treatment outcomes in a large patient population in the USA: an epidemiological study. Journal of Endodontics 30:846-850.