Signs and possible causes
| Sign | What needs checking |
|---|---|
| Pain with hot or cold that lingers for more than a few seconds | Pulp inflammation, alongside other causes of sensitivity |
| Throbbing pain that wakes you | Pulp inflammation or other causes of toothache |
| Pain when you bite or press on the tooth | A crack, bite problem or inflammation around the root |
| A pimple or boil on the gum near the tooth | Draining infection |
| Swelling of the gum or face | Abscess; needs prompt treatment |
| Tooth turning grey or darker | Nerve damaged, often after an old knock |
| Deep decay or a large broken filling | Bacteria close to or into the nerve |
| No symptoms, but a dark spot on the X-ray | Possible infection; X-ray findings need clinical interpretation |
Some of these, like brief sensitivity to cold, have simpler causes. That’s why diagnosis matters before treatment.
How we check
- Your history. What triggers the pain, how long it lasts, and whether it wakes you.
- Examination. Looking for decay, cracks, swelling and gum problems.
- Simple tests. Gentle cold, tapping and biting tests compare the tooth with its neighbours.
- X-rays, and a 3D scan for difficult cases, to see the roots and the bone.
You’ll be told whether the nerve can recover with a filling, needs a root canal, or whether the tooth can’t be saved, and the fee for each option.
If it does need a root canal
The treatment itself shouldn’t hurt, as the tooth is fully numbed, and many teeth are finished in one or two visits. Back teeth usually need a crown afterwards to protect them. Dr. Adish Chaudhary provides root canal care; difficult canals and previously treated teeth need assessment of whether specialist care is required. See root canal treatment and the root canal cost guide.
In pain now?
We’re open 10am to 8pm every day and check the earliest available appointment for tooth pain. If you have swelling spreading to your eye or neck, or difficulty swallowing or breathing, call 112 or go to the nearest hospital emergency department. See what to do for severe tooth pain.
Questions patients ask us
Can a tooth need a root canal without pain?
Yes. A nerve that has died can stop hurting, and an infection at the root tip can be painless for a long time. It's often found on a routine X-ray.
Signs you need a root canal after a filling?
Mild cold sensitivity for a few weeks after a deep filling is common. Pain that lingers, throbs, wakes you or gets worse instead of better suggests the nerve is inflamed and should be checked.
Can a crowned tooth need a root canal?
Yes. Decay can start under the edge of a crown, or the nerve can become inflamed years later. Often it can be treated through the crown.
Root canal or filling, how do I know?
A filling treats decay that hasn't reached the nerve. If the nerve is inflamed beyond recovery or infected, a filling alone won't stop the pain, and a root canal is needed. An examination, X-ray and simple tests tell the difference.
What are the signs a root canal needs redoing?
Pain on biting that returns months or years later, a gum boil near the tooth, swelling, or a dark area at the root tip on an X-ray. An endodontist can often re-treat it.
What happens if I ignore it?
The infection can spread into the bone, cause an abscess and swelling, and the tooth may become impossible to save.
Sources
NHS: root canal treatment ↗ADA MouthHealthy: root canals ↗NHS: dental abscess ↗Last updated 24 October 2026.