Root Canal Treatment

Written by the Dental Fear Central Web Team and reviewed by Dr Ikhlas El Karim, a specialist in Restorative Dentistry
Last updated on January 17, 2021

What is root canal treatment?

Root canal treatment (RCT) is a dental procedure in which the inflamed and infected nerve of the tooth is removed. The inside of the tooth is then cleaned and sealed to prevent further infection and save the tooth.



Is root canal treatment painful?

Root canals have a fearsome reputation for being painful and scary. But is this reputation justified?

The short answer is “no”. It may be hard to believe, but the actual root canal treatment really is not that much different from a filling. It takes longer, it’s more boring and there will be less drilling, but many other steps. As long as you’re adequately numbed, the treatment is totally painless.

Some people (and I now agree despite having initially been sceptical) have reported that it is a more relaxing experience than a conventional filling, despite taking longer. The difference is, I think, the long periods of quiet concentrated work.

Our DFC volunteer Brit has written about what RCT is like from a patient’s perspective. You can read her story further below.

Occasionally, there may be a flare-up after the procedure. But over-the-counter painkillers can deal with that.


When is root canal treatment needed?

RCT is needed when the centre of the tooth (also known as pulp or nerve) is infected by bacteria. It can save teeth which would otherwise need to be removed.

The most common cause of the infection is tooth decay, where decay-causing bacteria enter the pulp and cause infection and inflammation. Bacteria can also enter the dental pulp following an injury or if a filling is leaky.

This drawing shows how the pulp can become infected and inflamed:

Drawing of a tooth which needs root canal treatment. If the pulp of the tooth becomes infected, an abscess can form at the the root tip and cause swelling and pain.

The infection can cause a painful abscess, which usually forms at the tip of the root.


What is an abscess, and what causes it?

Here’s a great explanation from our forum, courtesy of Gordon Laurie, BDS:

“Sometimes, due to trauma or decay, the ‘nerve’ inside the tooth dies off. Any passing bacteria find this a source of nourishment and proceed to munch on the dead nerve and have lots of babies. Your body can’t do anything about this infection because along with the nerve dying, the blood supply to the tooth dies off too, so the body can’t send in antibacterial cells (white blood cells) to attack the bugs.

Eventually, the bugs start to spill out of the tooth and into the tiny space between the tooth and the jawbone. This starts an abscess: the body reacts to the invasion by pouring in defensive cells. These kill most of the bugs in the area, but still can’t get to the source of the problem, which is in the tooth.

If the bugs are hard to kill, the battle rages on for a while and because the area is very tiny, the pressure becomes high and it becomes extremely painful. This is called an acute abscess.

Anyway, to sort this mess out, the dentist has two choices:

  • extract the tooth and remove the bugs that way, or
  • do a root treatment.

In a root treatment, the inside of the tooth is cleaned and sterilised and then a plug is put in to bung up the space inside the tooth and stop more bugs getting in.”


How is root canal treatment done?

This drawing shows a root canal treatment in simplified terms. Note that the front tooth pictured here only has one canal, but back teeth (molars) have 3 or more canals.

Step-by-step illustration of a root canal treatment. First, the pulp is removed with dental files and the empty canal shaped. Then, the canal is filled with gutta percha, and the crown part of the tooth is filled with a dental filling.

The dentist will need to take an x-ray before, during and after the treatment is completed.

  1. The dentist makes an access cavity, using a dental handpiece (drill), to allow access to the canal.
  2. The pulp is removed with dental files, and the empty canal(s) are shaped.
  3. The canals are filled with a pink rubbery material called gutta-percha. The crown part of the tooth is filled with a regular, tooth-coloured dental filling.

Usually, you do root canal treatment over two visits. However, some endodontists do it in one visit.

Teeth that have had root canal treatment are more brittle. Back teeth usually need a restoration around the tooth (a crown, a three-quarter crown or an onlay) after successful root canal treatment so the tooth will not break. The last thing you want is to pay for root canal treatment and then have the tooth fracture!

Initially, the tooth will be restored with a filling. You then wait until the tooth has completely settled before placing the crown or other extra-coronal restoration.


What does root canal treatment feel like?

There are lots of technical descriptions of root canal treatment on the internet. But what does it actually feel like? Here, one of our forum moderators describes her personal experience.

My root canal experience

Since so many people seem to recoil in horror when they hear some friend or other is having a root canal treatment on their tooth, I thought I’d share my own root canal experiences.

I had cold sensitivity develop in a molar tooth which had previously been filled twice by different dentists, in the 1970s and in the 2000s. X-rays, cold air-spray, the probe and tooth sleuth (a plastic thing you bite down on each cusp individually to see if the tooth is cracked) all proved inconclusive.

So I was sent away but told to return immediately, if/when it got worse. Well, it took a few days, but eventually, I realised the weird pressure build-up sensations and spontaneous twinges in my tooth probably fell into the category of ‘getting worse’.

My dentist agreed that we needed to take action. He explained that the nerve was in the process of dying and the best thing to do would be a root canal treatment to save my tooth.

The first appointment

The first appointment involved

  • opening the tooth up
  • taking out the nerve to stop the toothache
  • cleaning out, finding and disinfecting all the canals, and
  • placing a medicated temporary dressing.

I gave my verbal consent and my dentist numbed me up so slowly and gently I couldn’t even feel it. After a couple of minutes, I felt outstandingly numb – this was reassuring to me. He charmed me into lying back by his comment that there was not going to be any pain involved whatsoever.

After waiting a while longer, he then tested gently with the explorer and asked if anything felt sharp. My answer was no, so all good to go.

The rubber dam

The next step was ‘putting on the rubber dam’ which was new to me. It can be a bit fiddly but you are already numb by this point. A special clamp is anchored with a frame around your tooth, and then a piece of rubber is stretched over the frame which they then adjust, usually so that only the tooth to be treated is visible in the dentist’s work area.

The rubber dam isolates the tooth being treated from saliva. It also meant that I could swallow easily when I needed to. Moreover, there was no danger of accidentally gulping down the treatment debris such as old filling material and the bleach later used to disinfect the canals. And it protected me in the unlikely event of there being any dropped instruments or files.

An unexpected further benefit of the rubber dam was that it made me feel it was not ‘me personally’ being worked on but rather ‘just my tooth.’

You may also use a soft bite block if you find it comfortable and easier on your jaw joint, but it is not compulsory. He offered me a soft bite block but it didn’t fit well, so I shook my head and he immediately removed it and I did just fine without.

At least 20 minutes had now passed.

Opening up the tooth

Next up was probably the most nerve-wracking moment for an RCT virgin! But I already trusted this guy from previous treatment, so I generously gave him the benefit of the doubt, when he informed me that he was now going to open up the tooth (by drilling into it with the handpiece in case you were still wondering!).

Before doing so, he reiterated that it was not supposed to hurt at all, and if I felt anything untoward, I must signal at once by raising my arm. He further reassured me that it was not a problem to top up the anaesthetic at any point.

So then came the noise and some vibration… after a couple of seconds, he stopped to check that I was indeed totally pain-free, I confirmed, and he gently continued. The level of vibration/pressure sensations was similar to that for a regular filling.

Cleaning the canals

For the next 90 minutes, he stayed totally calm and apparently happily absorbed in intricately working on my tooth. Some people may prefer more of a ‘running commentary’. Just ask if you do!

I couldn’t really see very much at all of what was going on unless I made a real effort to watch. This means if you don’t want to see, you can just relax and close your eyes, or, like me, alternate between staring at the ceiling and peeking at the proceedings. However, at one point, I was so relaxed that I found myself beginning to nod off.

Some of the time, it was noisy with the canals being explored using longish L-shaped pointed attachments to the handpiece. But most of the time, it was quiet with the assistant handing various tiny files to the dentist (he kept asking for particular numbers). He then either attached these files to the root canal system handpiece or more often than not used them by hand to carefully navigate the canals.

Occasionally, he asked me to adjust my head position slightly… just like at the hairdresser’s. There was quiet music playing in the background. Some people (and I now agree despite having initially been sceptical) have reported that it is a more relaxing experience than a conventional filling, despite taking longer. The difference is, I think, the long periods of quiet, concentrated work.

At various stages, maybe three times per appointment, he took a digital x-ray to confirm progress.

At frequent intervals, I glimpsed a syringe-like nozzle (no needle) which was used to squirt bleach down the canals. The liquid was then suctioned back out.

This alternating process of exploration/shaping and disinfection was repeated endlessly it seems until suddenly the rubber dam was removed and I was all done!

Part 1 all done!

The time had passed surprisingly quickly, and I felt a bit euphoric knowing that the toothache had finally been banished. My jaw felt a bit stiff (understandably), and the local lasted ages longer before it wore off, which was fine by me. The tooth sported a temporary sedative filling and looked slightly open still.

I went away having been assured that the second appointment would be very similar, with more shaping and a substance called gutta-percha being placed as the final filling material, topped off with composite. He also told me that it would be wise to get the tooth crowned eventually, once we were sure the treatment had been a success.

Between appointments (2 weeks) I had slight soreness occasionally, almost as if the tooth/gum were bruised.

The second appointment

At the second appointment, despite the nerve having already been removed, I was numbed up. It really was painstaking work with no stress for me, except for having to keep my mouth open for so long.

The main difference was that he used the ‘plugger’ a lot more, since this was the stage when he gently pushed the gutta-percha cones down to the bottom of the canals – the goal was to have no gaps.

Towards the end, I could sense some heat coming off something inserted in my tooth – I think this was probably serving to melt the gutta-percha?

The last stage was doing the composite filling. He did this very thinly, in lots of separate layers, and used the usual curing light multiple times. Then he checked my bite on a strip of paper.

He advised me to take Nurofen for the jaw joint as soon as I got home. I did so, but I felt no need to take a second dose.

This root canal treatment was successful and I later had the tooth crowned. Teeth that have had root canal treatment are more brittle and a crown provides extra support and strength to the tooth, especially if it is a back tooth. Depending on how the amount of tooth structure that is left, it may also be possible to opt for an onlay or a three-quarter crown.

My endodontist experience

I subsequently had an old root canal, done in the early 1990s by a general dentist, re-treated at an endodontist. An endodontist is a root canal specialist. He also did a great job – again over 2 long appointments. The only real difference between him and my dentist was the use of an endodontic microscope at the first appointment and a general air of confidence as to likely success. He quoted an 85% success rate which apparently is high for a retreatment.

He told me that the only real downside of treatment was if a file were to break off in the lower portion of a tooth root, it might be hard or impossible to retrieve. However, he quickly followed this up by an assurance that it had been years since he’d had such an incident, so I probably shouldn’t lose any sleep over it.

I was also aware of the endodontist measuring the canals from time to time – he wore a special ring on his finger with a ruler scale on it. My dentist had used an electronic device instead.

Written by Brit (DFC Moderator), 2010


Root Canal FAQs

What is an endodontist?

An endodontist is a dentist who specialises in root canal treatment.

Ask a Dentist – When should I see an endodontist?

We asked dentist Gordon Laurie the following question: When you need root canal treatment, under what circumstances would you personally (if it was your own tooth) see an endodontist? Here’s the answer:

Any tooth behind a premolar, unless it was a retreatment, then any tooth. Bear in mind I can get an endodontist to do it at no charge for me…

Why am I in pain after root canal treatment?

Pain upon biting down and dull pain is common and a recognised side effect of root treatment. It should disappear within 48 hours or so, but it can take some weeks for the tooth to fully settle. Here’s why you can get pain after root canal treatment, even though the nerve is no longer there:

Basically, when you stick instruments up the root canals, a little bit of the infected material will be pushed out of the end of the canal into the wee space between the tooth and the socket. This sets up a small area of local inflammation and can cause pain upon biting down and a dull pain. – Gordon Laurie, BDS

The pain should be manageable with maybe a little bit of an anti-inflammatory drug like ibuprofen or similar. Contrary to what many websites say, it’s not unusual for it to last a couple of weeks.

Why does root canal treatment have such a bad reputation?

Reason 1: “Root canals are painful”

You may have heard people say that root canal treatment is very painful, or you may have had such an experience yourself. Sometimes, a dentist may find it difficult to numb a tooth because of an acute abscess. You can read why, and how to deal with this, here: How to numb a hot tooth.

Nowadays, with modern techniques, root canal treatment is typically painless. What’s more, it will relieve the pain associated with an abscess.

Top Tips:

  • Root canal treatment should be a pain-free procedure with just local anaesthetic. If you can’t get numb for whatever reason, it’s time to rethink all options including sedation.
  • Specialist endodontists know how to use advanced numbing techniques for hard-to-numb teeth. So if your general dentist can’t get you numb, you might want to see an endodontist instead.
  • It is common practice to be numbed for the second appointment, even though the nerve is likely already gone. It makes work on the surrounding tissue much more comfortable. Besides, it gives longer-lasting relief from any discomfort afterwards.
  • It’s easier to prevent pain than to make it go away once it has started. Take ibuprofen before the local anaesthetic has worn off. Paracetamol is a good alternative if you can’t take ibuprofen because of asthma or other contraindications. Ask your dentist or endodontist which painkiller they recommend.

Reason 2: “Root canals never seem to work for me. What’s the point?”

There is no absolute guarantee that root canal treatment will work, but success rates are very high if done properly, in the order of 90% 1.

However, the treatment is technically difficult and some cases, especially the back teeth, may need a specialist endodontist. Front teeth are easier because:

  • they generally only have one canal (back teeth usually have three or more, and some canals can be hard to find)
  • the canal tends to be quite straight, compared to canals in back teeth
  • they’re easier for the dentist to access because they’re at the front and
  • the canals are wider.

Endodontists have special equipment such as a microscope and advanced training in root canal treatment. Especially for more complex root canal treatments and for re-treatments where a root canal has failed, their chances of success are higher, and in some cases much higher, than those of general dentists.

An operating microscope used by endodontists for root canal treatment
A microscope used by endodontists

This is not to say that general dentists cannot competently carry out root canal treatment. Indeed, there are many who do enjoy it and who’ve done additional training in endodontic therapy. But root canal treatment is not everyone’s cup of tea – it’s very intricate and requires time and patience.

So, even with an experienced dentist, you may want to agree up-front that they refer you to an endodontist if there are any unforeseen problems.

Questions you may want to ask your dentist

  • What would you do if it was your own tooth?
  • Would you see a specialist, or is it an easy enough job for a general dentist?
  • What is the likely success rate? How long will it last? – If the odds strike you as unacceptably low, or if the answer is something along the lines of “they last about 5 years max”, you may want to ask for a referral to an endodontist.
  • Will you use a rubber dam? – This is the standard of care, and not using a rubber dam is a red flag.
  • Will you be wearing loupes? – Loupes are magnifying glasses that look like binoculars. They allow dentists to carry out much more precise work.
Loupes should be used for fine dental work such as root canal treatment. They look like little binoculars.
  • Is it possible to get an onlay or a three-quarter crown? – If possible, all back teeth that have been root treated should have a crown, a three-quarter crown or an onlay to protect them. The choice of restoration depends on the amount of tooth structure left and what the x-rays show. The most conservative option is an onlay, but if there’s not enough tooth structure left, a full crown will be needed. Nowadays, the trend is to preserve as much tooth structure as possible.

How do I get to see an endodontist?

If you are an NHS patient (in the UK), you may be able to get a referral to a specialist endodontist at a hospital from your general dentist.

If you choose to go private, you don’t need a referral to see an endodontist – you can pick your own. But if you trust your dentist, it’s best to get their recommendation for a good endodontist. Otherwise, Google is your friend.

Root canal treatment is not cheap, so make sure you can afford it and find out the cost in advance (check their websites).

What can I do if root canal treatment has failed?

Often, it is possible to redo the treatment. If you’re in any doubt and you would like to save your tooth, consult with an endodontist to find out what the chances of success are. Retreatments are best done by endodontists.


You may also like:

Further Reading

Patient Information (British Endodontic Society) – Common questions and answers about root canal treatment.

Animated-Teeth.com: Root Canal Treatment – 8 pages of very detailed information about all aspects of root canal treatment.

Myths about root canals – American Association of Endodontists

Sources of Information

  1. https://britishendodonticsociety.org.uk/patient-public/further-information/[]