Lingering sensitivity, pain when biting or a swollen gum can sometimes indicate inflammation or infection inside a tooth. These symptoms do not automatically mean that you need root canal treatment, but they do warrant a dental assessment—particularly when they are severe, persistent or getting worse.

This guide explains why root canal treatment may be considered, how a dentist reaches the diagnosis, what happens during treatment and what recovery commonly involves. It provides general information only; an examination and, when appropriate, dental X-rays are needed to determine the cause of tooth pain.

What is root canal treatment?

The visible part of a tooth is protected by enamel and dentine. At its centre is the dental pulp, which contains nerves, blood vessels and connective tissue. Deep decay, a crack, trauma or repeated dental procedures can inflame or infect this tissue.

Root canal treatment—also called endodontic treatment—removes inflamed or infected pulp from inside the tooth. The canals are then cleaned, disinfected, shaped, filled and sealed. The purpose is to manage disease inside the tooth and, where the tooth is suitable, preserve it rather than remove it.

For an overview of treatment options, current Teeth Q fees and available subsidies, visit our root canal treatment service page.

Possible signs that a tooth needs assessment

Dental pain has several possible causes, and not every painful tooth requires root canal treatment. Arrange an assessment if you notice:

• lingering sensitivity after a hot or cold stimulus has been removed;
• spontaneous, throbbing or worsening tooth pain;
• pain when biting or chewing;
• a chipped, cracked or heavily restored tooth that becomes painful;
• swelling or tenderness around a tooth;
• a small pimple or gum boil close to the affected tooth;
• a tooth becoming darker after an injury; or
• pain or swelling associated with deep decay or a previous filling or crown.

Symptoms can occasionally become less noticeable if the pulp loses vitality, but that does not necessarily mean the underlying problem has resolved. A tooth may also require assessment after trauma even when there is no obvious crack.

How does a dentist decide whether a root canal is needed?

A diagnosis is based on more than the intensity of pain. Your dentist will ask when the symptoms began, what triggers them, whether there has been trauma or previous treatment, and whether you have swelling or other medical symptoms.

The assessment may include:

• examining the tooth, gums and nearby tissues;
• checking for decay, cracks, loose restorations and bite-related tenderness;
• comparing the tooth with neighbouring teeth using temperature or other pulp tests;
• tapping or applying gentle pressure to assess tenderness; and
• taking a dental X-ray when clinically indicated.

The dentist must also consider whether the tooth can be predictably restored. A severely fractured tooth or one with insufficient remaining structure may have a different prognosis even if root canal treatment is technically possible.

What happens during root canal treatment?

The exact sequence depends on the tooth and clinical findings, but treatment commonly involves the following stages:

1. Local anaesthetic: the tooth and surrounding tissues are numbed.
2. Isolation: a dental dam is normally placed around the tooth to keep the working area clean and dry.
3. Access: a small opening is made so the dentist can reach the pulp chamber and root canals.
4. Cleaning and shaping: inflamed or infected tissue is removed. The canals are carefully shaped and disinfected.
5. Filling and sealing: the prepared canals are filled and sealed to reduce the risk of reinfection.
6. Restoration: the opening is restored. A separate appointment may be needed for the definitive filling, onlay or crown.

A temporary filling may be used between appointments. It is important to return as advised so treatment and the final restoration can be completed.

Is root canal treatment painful?

Root canal treatment is normally carried out under local anaesthetic. Many patients attend because the tooth is already painful; treatment is intended to address the inflamed or infected tissue causing the problem.

You may feel pressure or movement during the appointment. The tooth and surrounding area can also feel tender for several days afterwards, particularly if there was inflammation before treatment. Contact the clinic if discomfort is severe, is getting worse rather than better, or is accompanied by swelling or other concerning symptoms.

How many appointments will I need?

Some cases can be treated in one appointment, while others require two or more visits. The number and length of appointments can be affected by the tooth involved, the number and shape of its canals, the presence of infection, whether the tooth has been treated before and whether symptoms settle as expected.

More complex anatomy, retreatment, a difficult diagnosis or a suspected crack may prompt referral to an endodontist—a dentist with specialist training in diagnosing dental pain and treating diseases of the dental pulp and root canal system.

Recovery and aftercare

Follow the individual instructions provided by your dentist. General precautions may include:

• avoid eating until the numbness has worn off so that you do not accidentally bite your cheek, lip or tongue;
• avoid hard or heavy chewing on the treated tooth, especially while a temporary filling is present;
• continue brushing and cleaning between the teeth, taking care around the treated area;
• attend every scheduled appointment for completion and restoration of the tooth; and
• if using non-prescription pain relief, follow the product label and check with a pharmacist or doctor if you have allergies, medical conditions, take other medicines, are pregnant or are unsure what is appropriate.

Do not place aspirin, pain-relief tablets or chemicals directly against the tooth or gum. Do not take leftover antibiotics. Antibiotics do not replace treatment of the source and are prescribed only when the clinician finds a specific indication.

When should I contact the dentist after treatment?

Contact the treating clinic promptly if you develop:

• severe pain or pressure that persists or worsens;
• visible swelling inside or outside the mouth;
• a rash, hives, itching or another possible medication reaction;
• a bite that feels noticeably uneven;
• a temporary filling or crown that becomes loose or comes out; or
• the return of symptoms that had previously settled.

Root canal treatment or extraction?

Root canal treatment aims to preserve a natural tooth. Extraction removes the tooth and may lead to a separate discussion about whether and how the space should be replaced. Neither option is automatically suitable for every case.

The decision depends on the diagnosis, the extent and location of any crack, remaining tooth structure, gum and bone support, restorability, medical considerations, expected prognosis and your preferences. Your dentist can explain the reasonable options and their limitations after assessing the tooth.

Will I always need a crown afterwards?

Not every root-treated tooth receives the same restoration. Back teeth and teeth with substantial loss of structure may benefit from cuspal coverage such as an onlay or crown. A front tooth with more remaining sound structure may be restored differently. The recommendation should be based on the individual tooth, bite and risk of fracture.

Can a root-treated tooth need treatment again?

A tooth can occasionally remain painful or develop new disease months or years after treatment. Possible management may include reassessment, non-surgical retreatment, root-end surgery or extraction, depending on the cause and whether the tooth remains suitable for treatment.

If surgery at the end of a root is being considered, read our guide to apicoectomy and root-end surgery.

Frequently asked questions

Can antibiotics cure an infected tooth?

Antibiotics alone generally do not remove infected or inflamed tissue from inside a tooth. Dental treatment is usually needed to address the source. Antibiotics may be considered when there are particular clinical indications, including concern about systemic or spreading infection.

If the pain stops, is the tooth healed?

Not necessarily. Pain can fluctuate, and symptoms may reduce if the pulp loses vitality. Arrange an assessment when pain has been severe, keeps returning or is associated with swelling, trauma, a crack or pain when biting.

How long can a root-treated tooth last?

Many appropriately treated and restored teeth continue functioning for a long time, but no treatment can guarantee a particular lifespan. Long-term outlook depends on the original condition, treatment quality, final restoration, oral hygiene, bite forces, gum support and regular dental care.

When might I be referred to an endodontist?

Referral may be considered for complex canal anatomy, retreatment, difficult-to-locate pain, dental trauma, suspected cracks, root-end surgery or when specialist equipment and training may assist with diagnosis or treatment.

Concerned about a painful tooth?

Choose your preferred Teeth Q clinic and describe your symptoms when booking. The team can guide you towards an appropriate dental assessment.

---

Sources and further reading

• NHS: Root canal treatment
• American Association of Endodontists: What is a root canal?
• American Association of Endodontists: Post-treatment care

General information only. This article does not replace an individual examination, diagnosis or treatment plan. Information reviewed against the sources listed above on 30 July 2026.