October 27, 2026
A failed root canal is a tooth that has had root canal treatment but still has an infection, or has become infected again. According to the NHS, root canal treatment removes an infection from inside the tooth, and the tooth is then cleaned and filled to prevent it getting infected again. When that does not hold, you may notice pain, swelling or a bad taste. Sometimes you notice nothing at all and an X ray is what shows the problem.
A tooth in this position can often be treated again, or treated with a small operation at the root tip, and in some cases it has to be taken out. Which route suits you depends on what is wrong with the tooth, and that needs an examination and X rays. Below we cover the signs to watch for, what X rays are used for, and the options your dentist may talk through.
Root canal treatment is carried out when the soft tissue inside a tooth, the pulp, is infected. The NHS says the dentist removes the infected pulp, cleans and shapes the inside of the tooth, then fills and seals it. A crown may be needed afterwards if the tooth was badly infected.
You can read about the steps and appointments in our post on how long a root canal takes.
There is rarely one single cause. Several can be involved, and a dentist usually has to work out which applies to your tooth.
Leeds Teaching Hospitals NHS Trust lists persistent infection as one cause, and re infection from a leaky filling, a leaky crown or new decay as another. If bacteria can get back into the tooth, the cleaning done at the first appointment can be undone.
The British Endodontic Society says problems can occur if the tooth develops decay or the restoration on the tooth fails. It also says a tooth that develops a crack can be a cause of failure and may result in the loss of the tooth.
If your dentist recommends a crown after a root canal, you can read about dental crowns and what they involve.
No single sign proves a root canal has failed, and only a dentist can tell you what is going on. These are the things worth taking seriously.
The NHS lists the symptoms of a dental abscess, which is a collection of pus that can form when a tooth is infected. They include:
Some discomfort after root canal treatment is expected. According to the NHS, the area around the tooth may feel swollen and sore but should get better in a couple of weeks. It also advises paracetamol or ibuprofen if you are in pain.
You can read more about urgent care for a dental abscess.
An X ray cannot tell the whole story, but it is one of the main tools your dentist uses. An X ray is used for the following:
The British Endodontic Society says treatment can fail for a number of reasons and that, in these cases, it may be possible to carry out the treatment again. The options below are the ones the NHS trusts and the Society describe. Which one is advised depends on your tooth.
The British Endodontic Society describes endodontic retreatment as carrying out the root canal treatment again. Leeds Teaching Hospitals NHS Trust says retreatment usually involves removing the previous root filling material.
Leeds Teaching Hospitals NHS Trust lists root tip removal surgery, called apicectomy, as an option. The British Endodontic Society describes endodontic surgery as lifting the gum after a small incision to allow access to the root tip, and says it allows the existing restoration to be kept.
Our complex root canal service is explained in our failed root canal treatment, and you can compare our standard root canal costs before you decide. You can read about tooth extraction and how we look after you, including sedation if you are nervous.
Antibiotics are not the same as treating the source of the problem. Leeds Teaching Hospitals NHS Trust mentions that a flare up after treatment may need antibiotics, and the NHS says that after drainage of an abscess you may be given painkillers or antibiotics.
Our post on when an abscess needs more than antibiotics covers this in more detail.
If you are thinking about an implant instead, our single dental implants page explains how one tooth is replaced.
The cost depends on which option your dentist recommends and how complex your tooth is. The British Endodontic Society says the cost of retreatment is usually dependent on how complex the procedure might be.
Where treatment is eligible, we offer 0% finance over 12 months, subject to status. We are a credit broker, not a lender, and you can read about dental finance before you decide.
See a dentist if a root canal treated tooth hurts, feels different, or has swelling around it, or if you have been told a tooth needs another look on an X ray. Our emergency appointment is £99, and same day appointments are available.
The NHS lists intense toothache, sensitivity to hot or cold, swelling in the face or jaw, a bad taste, difficulty opening the mouth and a high temperature as symptoms of a dental abscess. Some teeth cause no symptoms at all, so a dentist may only find a problem on an X ray. See a dentist if you notice any of these in a root canal treated tooth.
According to the NHS, the area around the tooth may feel swollen and sore but should get better in a couple of weeks. Leicester's Hospitals say pain and swelling is unusual but can happen, and advise contacting your dentist if you have severe pain or swelling. Pain that does not settle should be looked at.
Often the first option is to repeat the treatment. The British Endodontic Society says it may be possible to carry out the treatment again, which is called endodontic retreatment, and that retreated teeth can function for many years if the reasons for the first failure can be overcome. Your dentist can tell you whether that applies to your tooth.
Retreatment goes back into the tooth through the crown or filling and removes the old root filling material. An apicectomy is a small operation to reach the root tip through the gum. The British Endodontic Society describes endodontic surgery as lifting the gum after a small incision to allow access to the root tip.
An X ray is one of the tools your dentist uses. Leeds Teaching Hospitals NHS Trust says treated teeth are monitored with periodic X rays to check healing. Your dentist also looks at your symptoms and examines the tooth before saying what is going on.
Not necessarily, but occasionally a tooth cannot be saved. The British Endodontic Society says the alternative to endodontic treatment is extraction, and Leeds Teaching Hospitals NHS Trust says extraction may be necessary if there is not enough tooth structure left. Your dentist can explain whether your tooth can be kept.
The NHS says dental abscesses are usually treated by a dentist, who drains the pus, and that you may need root canal treatment if a tooth problem caused the abscess. Antibiotics may be given alongside treatment, but they do not replace treating the tooth itself.
Share it on:
4,8
I could not be more satisfied with my experience at Maida Smiles - A special mention to Dr Gurteurez who is one of the most friendly and professional dentists I have ever met
Adam
I had my first visit and the team was very warm, caring and professional. The online booking platform makes it very easy to arrange your appointment. Doctor Pedro made me feel comfortable despite this being my first appointment since Covid. He is incredibly knowledgeable and offers you the best treatment for your specific condition. I would highly recommend them
Gian Paolo Ziletti
Professional. Friendly. Informative. Maida Smiles offers great dental services including cleanings, oral surgery and realignment. I feel very lucky to have them so close by. I had an appointment just this week that was quick, thorough and safe.
Emily Chmura
Being very nervous about using dentists after a terrible experience when I was younger, I came to Maida Smiles and loved the calm patient demeanour of Pedro. You can clearly see Pedro and the team take pride in what they do and are perfectionists. The whole experience was great and I will never go to another dentist again.
Reena Nathwani
Delighted with the outcome of my treatment by Pedro. Meticulous attention to detail explaining exactly how the procedure would be carried out from first consultation to completion backed up with supporting guidance notes. Clearly an expert in his field and someone who cares passionately about the outcomes for his patients. Highly recommended.
George Jones
I loved my first visit to Maida Smile Dental Clinic. The staff member at reception was very warm, welcoming and professional. My dentist, Priscilla, and her assistant were fantastic. I have quite sensitive teeth near my gums and I can find the probing and investigation quite uncomfortable during a consultation, but this wasn’t the case at all. I didn’t experience discomfort and felt in very safe hands. This also applied to the hygienist work. I didn’t even have to ask Priscilla to avoid using the ultra sound cleaner on the sensitive areas of my teeth. I’m looking forward to going back, and that’s not often you can say that about going to the dentist!
Simone Gibson
Since I first had the luck to be recommended and book an appointment with Dr. Pedro Gutierres over 8 years ago, I have never trusted my dental health nor my family’s to anyone else. It’s very hard to find a dentist who ticks all the boxes and even goes beyond any expectations you may have, from service, sympathy, professionalism, and expertise, etc., 5 stars are not enough to rate him. I was so happy when he opened his own clinic and surrounded himself with the best professionals you can find, I cannot recommend Maida Smiles Dental Clinic enough.
Sofia Gouveia
Maida Smiles Dental Clinic is excellent!! The staff is very friendly, professional and always aiming for the customers best experience! A special thank you to Dr. Pedro Gutierres who is truly amazing. I am absolutely satisfied with the results and highly recommend this great dental clinic!
Ana Cruz
Dr. Pedro Gutierres is the best Implantologist I have come across. His work is amazing and of very high quality! I would highly recommend him and Maida Smiles to all my friends and family. If you want the perfect smile this is the place to go.
Blossom
“Pedro was so patient and professional throughout my treatment for my implants.. I chose to have my treatment with a local anaesthetic rather than any sedation and have a very bad gag reflex when anything touches the back of my throat. His patience throughout the experience was wonderful, completely putting me at ease and he also gave me a technique to help me in the future. I have seen him for my follow up and fully intend to book an annual visit in 2020. which is no small thing as I live 60 miles away.I can thoroughly recommend him for any treatment.”
Denise Gilbert
I was very nervous to pull my ingrown wisdom tooth. Dr Pedro Guiterres made me feel really comfortable and the job was completed very professionally. It didn’t take long at all and I didn’t feel any pain. I would definitely recommend his service at this practice.
Jihan Daoud
From the day I made my first appointment. The team at Maida smile were amazing. They didn’t treat me like a customer but more like family. They have been great in every step in FINALLY GETTING MY DREAM SMILE from the receptionist to my dentist Pedro Laranjeira I can’t thank you enough and of course Pedro Laranjeira beautiful wife…… they are very professional and understand that I had to change my appointment now and then for work commitments and they were very understand. I will defo recommend them 100% not forgetting how chic the office is
Tracy Mensah
I was very nervous about having a dental implant but was immediately put at ease by Dr Pedro Gutierres. The procedure was explained in full and the care both during and after treatment has been of the highest standard. I received advice on how to look after my implant and have had no problems. I highly recommend.
Dawn Briggs
I had 7 implants installed by Dr Pedro Gutierres, including one which required a bone graft. In my 70 years I’ve had some bad experiences with dental treatment so it takes a lot for me to relax but, from my initial consultation, through to the end of the treatment, I had complete trust in Pedro’s expertise: preparations for the treatment and after-care were extremely thorough and fully explained, the treatment itself was surprisingly endurable (considering what was involved) and the implants have made a major difference to my life. If you are considering implants then I would whole-heartedly and sincerely recommend Pedro for this work.
Russ Hickman
I couldn’t recommend Maida Smiles enough: the care, attention to detail and the way Dentists and Nurses made sure I felt comfortable and safe throughout the treatments was incredible. Dr Pedro explained the treatments in detail to me and I have never felt under pressure to proceed… but I am very glad I did as I am happy and confident to smile again!
Mariana Pinheiro
Highly recommend this place to anybody looking for a friendly and trustworthy practice with an incredibly friendly and patient staff. Dr Pedro has been one of the best dentists I’ve ever had, he made me feel comfortable and were very knowledgeable in explaining every step of what he was doing and answering all of my questions. Amazing thorough the procedure, excellent communication, superb and professional treatment. I hope they keep it this way for a long time.
Joas Souza
Dr Pedro is a very good, confident and experienced professional. I’ve known him for some years now and always felt well cared for, either for small or bigger treatments.The facilities of the clinic are amazing and all the staff are very friendly. Highly recommended.”
Nelson Cafruni
I went to different clinics before, and nobody could really convince me until Maida Smiles did. The team here makes you comfortable , shows you different options and different budgets , and doesn't try to make you go only for one plan. I felt that the team was knowledgeable and wanted to help me , so that's why I decided to start
Diogo
I was referred to Dr. Pedro who did such a wonderful job with my teeth. The staff was extremely professional, they put you at ease, and it just made the whole experience easier. I've never looked back since
Theresa
"I told him, 'I want beautiful teeth, beautiful but natural, I don't want fake looking teeth.' Now I smile, I talk... it just makes you more confident. If you wear a beautiful nice suit... you have beautiful teeth, then it's like a perfect."
Louca
"I went to my hygienist a little while ago, and she said to me they were the best implants that she'd ever seen and she would never have known that they weren't my real teeth."
Sharon
Dr. Pedro explained the process of Invisalign to me. It sounded easy, it was quite a quick process, and the end result is my teeth moved back, so I'm quite happy.
Soula
I feel like I've not just developed a professional relationship with my dentist and the staff... they become more like friends as well, because of the kind of compassion and sympathy that they give you during treatment.
Alvin
"After a friend recommended the clinic, I was referred to Dr. Pedro, who did such a wonderful job with my teeth. The staff was extremely professional; they put you at ease, and it just made the whole experience easier. They have more than met my expectations. I have to have a few more implants, and I'm not afraid anymore. Now, finally, I can live again."
Lesley
"After not having a great experience with previous dental treatments, I was desperate for someone that I trusted. I broke a tooth, and even before I saw Dr. Pedro, he reassured me that I was going to be fine. He made me feel very comfortable and at ease. It was an amazing experience, from not only Dr. Pedro but also all the staff in the clinic, and I would definitely recommend [them] ".
Mariana
I chose Maida Smiles because of the reviews and a friend who was really happy with the results. The results definitely met my expectations. My expressions are much more smooth than before and it really makes the difference
Carolina
I’m very grateful for the quick and efficient service I received when I needed an emergency appointment. The staff were kind and accommodating, and the dentist provided clear, helpful advice that made a real difference. The whole experience was reassuring. Highly recommend their professionalism and expertise!
Safiya Guled
I am always anxious when having to see the dentist and this was one of my first experiences with Maida Smiles. The dentist, Benedict Harrison was very reassuring and immediately put me at ease. He was quite lucid in his explanations of what had to be done, etcetera, and is making good progress with the ongoing treatment. Also, the rest of the staff were friendly and just plain nice.
John Jacobs
Wow wow Dr Claudia is the best dentist in London, my kid adores her and it is always a pleasant visit. Can’t recommend her enough
Bel Cohn
I am delighted with the results of my replacement veneers.
Dr Benedict Harrison was very good at talking me through the whole process and keeping me informed during the treatment if there were any issues - which there weren’t.
He has a charming demeanour which is an added advantage in a dentist, who I think we all agree are not our favourite people, overall a 5 star experience.
Karen Shepherd
I went to the Maida Smiles Clinic for the first time and had the most wonderful experience! I am dentist phobic but strangely left the place with a big smile on my face (literally!). The receptionist was super kind, Susan was impeccable and very helpful, and I had my appointment with the most amazing dentist Dr Mafalda Vilhena. Couldn’t recommend her enough. She explains the whole procedure and is very rigorous in her work. Congratulations to Dr Pedro Gutierres for creating such an excellent working environment and to all the team. I will be back and bringing my family along and we don’t even live in Maida Vale. Thank you for such an impeccable job on my teeth and for taking my fear of dentists away. Note: they don’t cover NHS, only private bookings or with insurance.
Maria Monteiro
Address: 207-209 Sutherland Ave, London W9 1RU. Get directions.
Paid parking is available using ParkBee on Lanark Road (the road right next to the practice). For public transport users, we are a two-minute walk from Maida Vale tube station.
