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Root canal treatment

Page last reviewed: 13/07/2011

Root canal treatment is a dental procedure to treat infection at the centre of a tooth (the root canal system). Root canal treatment is also called endodontics. The infection is caused by bacteria that live in the mouth and invade the tooth when:

  • tooth decay occurs
  • fillings leak
  • teeth are damaged by trauma, such as a fall 

See the Health A-Z topic on Tooth decay for more information about how decay starts.

Tooth structure

A tooth is made up of two parts:

  • The crown is the part of the tooth that is visible in the mouth.
  • The root extends into the bone of the jaw, anchoring the tooth in position.

These are composed of the following structures:

  • Enamel is the hard outer coating of a tooth.
  • Dentine is a softer material that supports the enamel and forms most of the tooth. 
  • Cementum is a hard material that coats the root surface.
  • Dental pulp is the soft tissue at the centre of the tooth.

The root canal system

The root canal system contains the dental pulp and extends from the crown of the tooth to the end of the root. A single tooth can have more than one root canal.

The pulp is made up of soft tissue that includes nerves and blood vessels. If bacteria infect the pulp, it will begin to die. After this, the bacteria can increase in number. The bacteria and the substances they release will eventually pass out of the end of the root canal through the small hole where the blood vessels and nerves enter.

This process continues as there is nothing to stop more bacteria passing down the root canal, which causes the tissues around the end of the tooth to become red and swollen. This can cause your tooth to become painful and, in extreme circumstances, your face may become swollen (dental abscess).


To treat the infection in the root canal, the bacteria need to be removed. This can be achieved by:

  • removing the tooth (extraction) 
  • attempting to save the tooth by removing the bacteria from the root canal system (root canal treatment)

In root canal treatment, the bacteria are removed from inside the root canal system, the root canal is filled and the tooth is sealed with a filling or crown. In most cases, the inflamed tissue at the end of the tooth will heal naturally.

Root canal treatment should not be painful because local anaesthetic is usually used. The procedure is usually very successful and should be no more unpleasant than having a filling. In about 9 out of 10 cases, a tooth can survive for up to 10 years after root canal treatment.

An abscess is a lump containing pus, which is made by the body during infection.

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and others are good for you.

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Page last reviewed: 13/07/2011

Root canal treatment may be necessary if tooth decay affects the centre of the tooth.

Tooth decay

Your mouth is full of millions of bacteria. When you consume food and drink that is high in carbohydrates (sugary or starchy foods), the bacteria turn the carbohydrates into the energy they need, as well as producing acid.

The acid combines with the bacteria, the saliva in your mouth and small particles of food to produce a sticky film called plaque. Over time, the plaque begins to break down the surface of your tooth. This is known as tooth decay, dental decay or dental caries. See the Health A-Z topic about Tooth decay for more information.

In cases of advanced tooth decay, the bacteria can penetrate through the surface of the tooth and enter the soft tissue at the centre of the tooth, called the pulp. If this happens, the bacteria will start to kill the pulp, which increases the risk of infection developing inside the root canal.

In this situation, the only way to save the tooth and prevent the spread of infection is to use root canal treatment to:

  • remove the pulp
  • clean out the root canal
  • fill the tooth and canal with an artificial filling

An alternative to tooth loss

In the first half of the last century, it was common for people to have all or most of their teeth removed at a young age. However, tooth loss is now avoidable due to a better understanding of:

  • the causes of gum disease (bacteria) and tooth decay (bacteria and sugar)
  • the benefits of brushing your teeth and fluoride, a mineral that is now used in toothpaste

As a result, over the last few decades more and more people have kept their teeth into later life, and many children and young adults have not needed to have fillings.

Nowadays, when problems occur with teeth, people are more likely to want to save their teeth than have them extracted and replaced with false teeth. For most people, leaving gaps around the mouth or replacing missing teeth with false teeth are not socially acceptable.

Bridgework (a fixed replacement for missing teeth) is a good replacement option, although it can also result in root canal infections. Dental implants, where a tooth is fixed in your mouth with a metal rod, are the closest thing to replacing natural teeth, but for most people these are not possible due to their cost.

As well as these problems, losing teeth can have a psychological effect. This means that many people ask their dentists to save their teeth rather than take them out. When a tooth develops a root canal infection, the only reliable way to save the tooth is to use root canal treatment.

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and others are good for you.

Dental pulp
The soft tissue at the centre of the tooth.

Plaque is a sticky substance, made up of bacteria, that can build up on your teeth if you do not brush them.

Root canal
The root canal system contains the dental pulp and extends from the crown (the part of the tooth that is visible in the mouth) to the end of the root (which extends into the bone of the jaw, anchoring the tooth in position).

Page last reviewed: 13/07/2011

Root canal treatment is only required when it is clear that the soft tissue at the centre of the tooth, called the pulp, has been damaged by a bacterial infection.

Your dentist can test your teeth and use X-rays to establish whether a bacterial infection has occurred. Dental X-rays use radiation to take images of your teeth to identify any problems. See the Health A-Z topic about X-rays for more information.

Symptoms of a pulp infection

The symptoms of a pulp infection include:

  • pain when eating or drinking hot or cold food and drink
  • pain when biting or chewing (in some cases)
  • the tooth may become loose

As the infection progresses, these symptoms often disappear as the pulp dies. Your tooth then appears to have healed, but in fact the infection is spreading through the root canal system. Eventually further symptoms occur, such as:

  • pain when biting or chewing
  • swelling of the gum near the affected tooth
  • pus oozing from the affected tooth
  • facial swelling
  • the tooth becoming darker in colour

It is important that you see your dentist if you develop toothache.

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.

Dental pulp
The soft tissue at the centre of the tooth.

Root canal
The root canal system contains the dental pulp and extends from the crown (the part of the tooth that is visible in the mouth) to the end of the root (which extends into the bone of the jaw, anchoring the tooth in position).

Is there an alternative to root canal treatment?

If you have an infected tooth, the infected pulp cannot heal by itself. Leaving the infected tooth in your mouth may make it worse. There may also be less chance of the root canal treatment working if the infection within your tooth becomes established.

If you need root canal treatment, the only alternative is to have the tooth removed. However, this is not usually recommended because it is better to keep as many of your natural teeth as possible.

Antibiotics (medication to treat bacterial infections) are not effective in treating root canal infections. This is because the active ingredient in antibiotics can only work by reaching the site of the infection through your blood, and the bacteria that cause the infection are within the root canal system.

Repeated courses of antibiotics may also lead to bacteria adapting and finding ways to survive the effects of an antibiotic. They become antibiotic resistant, which means that the antibiotic no longer works.

Page last reviewed: 13/07/2011

Root canal treatment is carried out by your dentist over two or more appointments. Unless you are entitled to free dental treatment, you will need to pay for root canal treatment.

Find out about the costs before you start treatment.

Your dentist may refer you to a specialist in root canal treatment (endodontist) if the work is particularly complex.


Before you have root canal treatment, your dentist may take a series of X-rays of the affected tooth. This will allow them to build up a clear picture of the root canal and assess the extent of any damage.


Root canal treatment is usually carried out under local anaesthetic (painkilling medication). In some cases, where the tooth has died and is no longer sensitive, it may not be necessary to use a local anaesthetic.

Occasionally, teeth may be difficult to anaesthetise. In this case your dentist can use special local anaesthetic techniques to ensure that your treatment is not painful.

Removing the pulp

Your dentist will open your tooth through the crown, the flat part at the top, to access the soft tissue at the centre of the tooth (pulp). They will then remove any infected pulp that remains. 

If you have a dental abscess (a pus-filled swelling), your dentist will be able to drain it at the same time.

Cleaning and filling the root canal

After your dentist has removed the pulp, they will clean and enlarge the root canal so it can be easily filled. The root canal is usually very narrow, which makes it difficult to fill.

Your dentist will use a series of small files to enlarge the canals and make them a regular shape so they can be filled. This part of the treatment may take several hours to complete and may need to be carried out over a number of visits.

Your front incisor and canine teeth (biting teeth) usually have a single root containing one root canal. The premolars and back molar teeth (chewing teeth) have two or three roots, each of which contains either one or two root canals. The more roots that a tooth has, the longer the treatment will take to complete.

If the treatment is carried out over several visits, your dentist may put a small amount of medication in the cleaned canal in between visits to kill any remaining bacteria. The tooth will then be sealed using a temporary filling. If the infection has caused generalised or severe symptoms, such as a raised body temperature or a large swelling, you may be given antibiotics to help manage and prevent further infection.

Sealing and fixing the tooth

At your next visit, the temporary filling and medication within the tooth will be removed and the root canal filling will be inserted. This, along with a well-fitting filling, will seal the tooth and prevent re-infection.

Root-filled teeth are more likely to break than healthy unrestored teeth, so your dentist may suggest placing a crown on the tooth to protect it. See the box to the left for more information about crowns.

In some cases, a root-filled tooth may darken, particularly if it has died as a result of an injury, such as a knock to the tooth. There are several ways your dentist can treat discolouration, such as whitening the tooth using chemicals.


Root canal treatment is usually successful at saving the tooth and clearing the infection.

One review of a number of studies found that 90% of root-treated teeth survived for 8 to10 years. The study also found that having a crown fitted to the tooth after root canal treatment was the most important factor for improving tooth survival rates.

If you practise good oral hygiene (see box, right), you should be able to successfully keep the tooth for a long time. The survival of your tooth depends on a number of factors including:

  • how much of the natural tooth remains
  • how well you keep your teeth clean
  • the biting forces on the tooth

However, if an infection does return, the treatment can be repeated. Alternatively, if treatment has already been carried out to a high standard and the infection remains, a small operation known as an apicectomy can be carried out to treat the infection.

An abscess is a lump containing pus, which is made by the body during infection.

Bacteria are tiny, single-celled organisms that live in the body. Some can cause illness and disease and some others are good for you.

Dental pulp
The soft tissue at the centre of the tooth.

Root canal
The root canal system contains the dental pulp and extends from the crown (the part of the tooth that is visible in the mouth) to the end of the root (which extends into the bone of the jaw, anchoring the tooth in position).


A crown is a cap that completely covers a real tooth. A crown might be necessary after root canal treatment to prevent the tooth from fracturing.

Crowns can be made from:

  • metal or porcelain (or both)
  • a ceramic material
  • glass

Your tooth needs to be reduced in size and the crown is then used to replace what is removed. Your crown is made using a mould of your teeth to make sure that it is the right shape and size and that it fits your tooth accurately.

When fitting the crown, cement is used to glue the crown to the trimmed-down tooth. If there is only a small amount of tooth left after the root canal treatment, a post can be cemented in the root canal and used to help keep the crown in place.

Looking after your teeth

Following the advice below will help ensure that your teeth remain clean and healthy.

  • Brush your teeth twice a day, in the morning and in the evening.
  • Spend at least two minutes brushing your teeth each time.
  • Always use fluoride toothpaste.
  • Use a small toothbrush so that you can reach your back teeth, and use no more than a pea-sized amount of toothpaste.
  • Flossing can be a very effective way of reaching the gaps between your teeth.
  • Do not brush too hard because this can damage your gums.

Page last reviewed: 13/07/2011

While you are having root canal treatment, avoid chewing or biting down on hard foods until the treatment has been completed. In some cases, this could be after several visits to the dentist.

After your final treatment, your restored tooth should not be painful, although it may feel sensitive for a few days afterwards. Over-the-counter painkillers, such as paracetamol or ibuprofen, can be taken to relieve any discomfort. Always read the packet to make sure that:

  • the medication is suitable for you
  • you are taking the correct dose

Return to your dentist if you continue to experience pain or swelling after using painkillers.


After root canal treatment, clean the tooth in the same way as your other teeth and return to your dentist for check-ups as often as they advise.

Page last reviewed: 13/07/2011

Tooth decay is the most common way for bacteria to infect the root canal system. If you look after your teeth, you can prevent tooth decay developing and root canal treatment will not be necessary.

Bacteria can also enter the root canal under leaking fillings, through small cracks or when teeth break if they receive any trauma, for example after a fall. Therefore, it is important to see your dentist regularly as they can spot potential problems and prevent unnecessary treatment.

Oral hygiene

Maintaining good oral hygiene is one of the most effective ways of preventing the need for root canal treatment. Brush your teeth at least twice a day using fluoride toothpaste. Fluoride is a naturally occurring mineral that can help prevent tooth decay. See the Health A-Z topic about Fluoride for more information.

Flossing is also an important part of oral hygiene. Take a piece of dental floss and gently guide it into the space between your teeth. Move the floss up and down several times before moving on to the next space.

It is recommended that you floss your teeth once a day. You may find flossing tricky at first, and you may experience some bleeding from your gums for the first few days. This should improve with time. Ask you dentist for advice if you need assistance or if the bleeding continues.


Do not consume food and drink that is high in sugar too often. The bacteria in your mouth will break down the sugar into acid, which attacks your teeth and causes tooth decay. Eating sugary foods regularly is more likely to cause tooth decay than eating a large amount of sugar in one sitting.

Food and drinks that are high in sugar include:

  • fizzy drinks
  • chocolate
  • sweets
  • cakes
  • biscuits

Check the label to see how much sugar a product contains . See the Health A-Z topic on Diet for healthier alternatives, such as fruit, vegetables and sugar-free squash.

Chewing sugar-free gum after you have eaten may also help prevent tooth decay. When you chew gum, your mouth produces saliva which neutralises the acid in your mouth before it can damage your teeth.


Smoking can affect the way your mouth heals after root canal treatment. Smoking is also a big risk factor for gum disease, another dental health condition.

Giving up smoking will also help prevent life-threatening conditions such as:

  • heart disease, when your heart's blood supply is blocked or interrupted by a build-up of fatty substances
  • stroke, when the blood supply to the brain is restricted or interrupted
  • lung cancer

Speak to your GP if you want to give up smoking. A number of treatments are available to increase your chances of quitting successfully, and your GP can put you in touch with local support groups and one-to-one counsellors. See the Health A-Z topic about Quitting smoking for more information.

If you decide to stop smoking, your GP will be able to refer you to a local smoking cessation service which will provide you with dedicated help and advice about the best ways for you to give up smoking. You can also call the National Smokers Quitline at 1850201203, or log on to www.quit.ie, or join our facebook page at www.facebook.com/hsequit for further support.

Sugar and food labels

Check the labels on foods to see how much sugar they contain. Sugar comes in many forms, so look out for the following ingredients:

  • glucose
  • sucrose
  • honey
  • dextrose
  • maltose
  • fructose
  • hydrolysed starch or syrup

Ingredients are usually listed in order of the amount used, with the main ingredient listed first. If sugar, or one of the ingredients above, is near the top of the ingredients list, it may mean that the food is high in sugar.

Some products also use the traffic light system as part of their labelling to indicate whether they are high or low in sugar:

  • A red light indicates a high amount of sugar.
  • An amber light indicates a medium amount of sugar.
  • A green light indicates a low amount of sugar.

In general:

  • High in sugar means more than 15g of sugar for every 100g of product. 
  • Low in sugar means less than 5g of sugar for every 100g of product. 

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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