Root Canal Treatment: Saving an Infected Tooth

A tooth needs root canal treatment when its pulp is irreversibly inflamed, infected or has died, and the tooth can be restored.

NHS guidance lists the usual causes as tooth decay, gum disease, a chipped, broken or cracked tooth, or a dental abscess. Without treatment, the tooth may need to be taken out. You can read about signs that a tooth needs restoring in our symptoms section.

NHS guidance says to see a dentist if toothache lasts more than 2 days, does not go away when you take painkillers, comes with a high temperature, pain when you bite, red gums or a bad taste in your mouth, or comes with a swollen cheek or jaw. Go to A&E if you have toothache and the area around your eye or your neck is swollen, or swelling in your mouth or neck is making it difficult to breathe, swallow or speak.

If you think you have a dental abscess, ask for an urgent dentist appointment or get help from NHS 111. NHS dental abscess guidance says to call 999 or go to A&E if you are finding it hard to breathe, speak or swallow, have a swollen or painful eye or suddenly have problems with your eyesight, have a lot of swelling in your mouth, or are finding it hard to open your mouth. Do not drive to A&E: ask someone to drive you, or call 999 and ask for an ambulance.

This page covers planned treatment. Our page on emergency root canal treatment covers the urgent route.

Root canal treatment lets you keep a tooth that would otherwise need to be taken out, by clearing the infection from inside it.

Keeping the tooth means there is no gap to replace. The alternatives Leeds Teaching Hospitals NHS Trust sets out include no treatment, root-tip surgery (apicectomy), and extraction followed by no replacement, a denture, a bridge or an implant. Our comparison page covers deciding whether to save or remove a tooth.

Treatment is not right for every tooth. Research links the outlook to how much sound tooth remains and to cracks (Patel and colleagues, 2024), and the British Endodontic Society notes that extraction may be needed where too much tooth has been lost.

Root canal treatment has high success and survival rates in published research, though results vary with the tooth and the infection.

A 2024 systematic review in the International Endodontic Journal pooled 20 studies of root-filled back teeth and found about 91% still in place at 4 to 7 years and about 87% at 8 to 20 years, though the authors call the evidence limited. Leeds Teaching Hospitals NHS Trust reports about 96% success for its hospital service without inflammation at the root end, and about 85% with it. These are not results for any one practice.

The outlook depends on remaining tooth structure, cracks, gum disease, contact with neighbouring teeth and the quality of the root filling and seal (Patel and colleagues, 2024; British Endodontic Society). Risks listed by Leeds Teaching Hospitals NHS Trust include incomplete healing, blocked canals, an instrument separating in a canal, a perforation, and a higher risk of the tooth fracturing later.

Healing takes time. The British Endodontic Society recommends judging the outcome at least one year after treatment with an examination and X-ray; where healing is uncertain, the tooth is monitored until healing is complete or for at least four years. Our guide to restoring damaged teeth covers prognosis across restorative treatments.

After root canal treatment, the area may feel swollen and sore but should get better in a couple of weeks (NHS).

Numbness can last several hours, and paracetamol or ibuprofen can help if you are in pain (NHS). Leeds Teaching Hospitals NHS Trust reports that about 1 to 5% of people have a flare-up with increasing pain or swelling 3 to 4 days later, which may need antibiotics, so contact your dentist if that happens. If swelling spreads around your eye or neck, or makes it hard to breathe, swallow or speak, go to A&E or call 999 (NHS).

Whether a crown is needed depends on how much sound tooth is left. NHS guidance says a crown may be needed if the tooth was badly infected, and the British Endodontic Society advises that a back tooth missing a side wall usually needs a restoration covering its biting surface, such as a crown or onlay.

Where a crown is needed at Deepcar Dental Care, it is placed soon after treatment where the tooth is at higher risk, or after around 3 months to let the tooth settle, decided case by case. No overseas laboratory work is used. A crown placed at the practice carries 12-month aftercare cover, giving free repair, free replacement or remake and free adjustments. The cover does not apply where damage results from accidental trauma or infection.