Root canal treatment is carried out by your dentist over two or more appointments.

Preparation

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.

Anaesthetic

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 your treatment is not painful.

Removing the pulp

Your dentist will first place a sheet of rubber (a rubber dam) around the tooth to ensure the tooth is dry during treatment. This also protects you from swallowing or breathing in any chemicals the dentist uses.

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 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 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 (see below) on the tooth to protect it.

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.

Crowns

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
• powdered 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.

What are dental fillings and crowns are made of?

Fillings and crowns can be made of several different materials.Ask your dentist what material they recommend, as some will be more suitable than others.

Fillings

Fillings are used to repair a cavity in your tooth caused by decay. The most common type of filling is dental amalgam, made from a mixture of mercury and different metals. Dental amalgam fillings are often used on your back teeth as they are hard-wearing.

Your dentist will offer you the type of filling most appropriate for your clinical (medical) needs. This may include a tooth-coloured (white) filling. For example, if you need a filling for one of your front teeth, your dentist may suggest a tooth-coloured filling, but the use of tooth coloured fillings on back teeth is considered purely cosmetic.

Fillings can be made of:

---amalgam (silver-coloured): a mixture of metals including mercury, silver, tin and copper

---composite (tooth-coloured): powdered glass and ceramic added to a resin base, they’re not as hard-wearing as amalgam fillings 

---glass ionomer (tooth-coloured): powdered glass, which reacts chemically with your tooth and bonds to it, but it is weak so is only used on baby (first) teeth or around the sides of teeth

Crowns

A crown is a type of cap that completely covers a real tooth. Crowns can be made of:

---alloys (mix of metals) containing not less than a third of fine gold, platinum or palladium

---alloys containing stainless steel, cobalt chromium or nickel chromium

---porcelain

---porcelain bonded to precious metals

---alloys bonded to wrought platinum coping

Prefabricated crowns (crowns made ahead of time) are made from plastic and metals. These are used temporarily until a permanent crown can be fitted.  

Results

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 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 to remove the root tip (known as an apicectomy) may be carried out to treat the infection.