If the nerve has been removed, what is left to hurt?
This is the part nobody explains properly, and it is the key to everything below.
Root canal treatment empties the inside of the tooth: the pulp — nerve and blood vessels — is removed, and the canal system is disinfected and sealed. From that point the tooth itself has no sensation. It cannot feel cold. It cannot ache.
But a tooth is not a stone sitting in a hole. It hangs in its socket on a thin, richly supplied periodontal ligament (Wurzelhaut), which is very much alive: it registers pressure and becomes inflamed like any other tissue. Around it is bone, beyond that the gum, both with their own nerve supply. In the upper jaw, the roots of the back teeth sit directly beneath the maxillary sinus, close enough that a sinus infection can be felt as toothache.
So “my dead tooth hurts” honestly translates as: something in the neighbourhood of this tooth is irritated — which is why the diagnosis depends on the pattern of the pain rather than the tooth’s history.
The first two weeks after treatment
Tenderness on biting is the classic complaint. Instruments and rinsing solutions have been working right at the root tip, and the ligament there becomes briefly inflamed, so the tooth feels slightly raised — as if it meets its opposite number a fraction too early. This normally eases within a few days. A dull background ache for a day or two is also within the usual range, and a tender gum beside the tooth is often just the rubber dam clamp or the injection site.
What is not part of normal healing: pain increasing after the third or fourth day, throbbing that keeps you awake, swelling of the cheek or a temperature. Occasionally a treated tooth flares up as the body reacts to the disturbance — uncomfortable but manageable, and a phone call rather than a wait.
Pain months or years later: start with when it hurts
Once a settled tooth changes, the timing and the trigger point almost directly at the cause. Below are the sentences patients actually use, and what each usually means — working out which one fits is the whole job of the appointment: Root canal treatment (endodontics) – service page (EN).
"It only hurts when I bite on it"
The most common complaint, and often the most easily fixed. A crown or filling sitting a fraction of a millimetre too high takes the force of every clench, and the ligament beneath becomes inflamed from sheer overload. Coloured foil, a few seconds of polishing, and the pressure comes off.
The other candidate is a crack. The giveaway is a sharp jolt when you release the bite rather than when you press down, often on something hard or fibrous. A crack in the crown part can often be dealt with by covering the tooth; one running lengthways down the root usually cannot be repaired.
"It hurts on its own, in waves"
An ache that arrives without any trigger, comes and goes over weeks and sometimes wakes you points towards inflammation at the root tip. Either bacteria survived somewhere in the canal system — a narrow side canal, a canal never located — or they have found their way back in from above, through a leaking crown margin or new decay. Establishing which matters, because it decides whether a second treatment has a realistic chance: When does a root canal need to be redone? (EN).
"The gum above it is sore, or there's a little bump"
A small pimple on the gum over the root, which sometimes discharges and then disappears for weeks, is a sinus tract — the body’s own drainage channel from an inflamed root tip. It is often almost painless, which is exactly why it gets ignored, and it should be examined. Tenderness along the gum margin rather than up at the root usually belongs to the gum itself: Gum inflammation or periodontitis? (EN).
"It hurts when I lean forward, and my cheekbone aches too"
Upper back teeth only. Pain that worsens when you bend down or descend in an aircraft, affects several teeth at once and comes with a blocked nose usually originates in the sinus, not the tooth. Root-treated upper molars get blamed for this regularly and unfairly.
"It hurts, but I can't say which tooth"
Teeth are poor at reporting their own location. Pain from a neighbour, a wisdom tooth or even the jaw joint is routinely felt in the root-treated tooth, simply because that is the one the patient already worries about. Diffuse pain needs an examination rather than a guess — and sometimes the treated tooth turns out to be entirely innocent.
"It has never really stopped since the treatment"
Rarely, pain persists after a technically sound treatment because the nerve pathways serving that area have themselves become sensitised. There is nothing to find on an X-ray, and repeating the treatment does not help — which is why an honest assessment matters before anyone drills again. Uncommon, but real, and it deserves naming rather than dismissal.
| What you feel | What it often means | How quickly to act |
|---|---|---|
| Sore to bite, first days after treatment | Normal healing of the ligament | Wait, call if it worsens |
| Sharp pain on biting, weeks or years later | Crown or filling slightly too high | Ordinary appointment, quickly resolved |
| Jolt when you release a bite | Possible crack | Prompt appointment |
| Ache in waves, no trigger, sometimes at night | Inflammation at the root tip | Appointment within days |
| Bump on the gum over the root | Drainage from a chronic inflammation | Appointment, even without pain |
| Worse leaning forward, several teeth, blocked nose | Sinus rather than tooth | Appointment, often with your GP |
| Swelling, fever, spreading pain | Acute infection | Same day, out of hours the Notdienst |
What about cold and heat?
A properly treated tooth should not react to cold at all — there is nothing left inside to react. A sharp cold twinge that seems to come from one is therefore a useful clue, and it usually means one of three things: it is not that tooth; it is an exposed root surface beside it, where the gum has receded; or a canal in a multi-rooted tooth was never located and still contains living nerve tissue — the one scenario in which a “dead” tooth really can feel cold.
Heat is the more serious signal. Pain that flares with hot drinks and lingers afterwards points to pressure inside an inflamed space, and belongs at an appointment rather than in a wait-and-see.
What helps while you wait for the appointment
- Chew on the other side. Taking the load off an inflamed ligament does more than anything in the bathroom cabinet.
- Cool the outside of the cheek, not the tooth. Warmth soothes at first but tends to worsen an acute infection.
- An ordinary painkiller in normal doses is reasonable for a night or two; needing one every day means the tooth needs attention, not a bigger box. Never place a tablet against the gum — aspirin held next to a tooth burns the tissue.
- Antibiotics are not a cure here. They can control a spreading infection, but cannot reach bacteria inside a sealed root canal, and a leftover course from a previous illness mostly delays the diagnosis.
- Write down the pattern: when it hurts, what sets it off, how long it lasts. Two sentences of that beat an hour of guessing.
What's normal — and when to contact us
Special situations
If you are an anxious patient. Pain in a tooth that was supposed to be finished with is demoralising, and for someone who found the first treatment hard, the thought of going back is worse than the ache. Tell us when you book: we plan more time rather than less, and offer sedation and laughing gas (Lachgas) where it helps.
If you grind your teeth. Bruxism (Bruxismus) loads a root-treated tooth all night, and it is a frequent reason a quiet tooth becomes sore to bite on without anything else having changed. A night guard (Knirscherschiene) often settles it.
If the tooth was treated abroad. Very common here, and no criticism implied. Bring what you have, including photographs of old X-rays on your phone; knowing what is already inside the tooth shortens the diagnosis.
If you are new to Germany, or your German is limited. This is the topic where language costs people most, because the whole diagnosis rests on describing a sensation. “It hurts when I bite” and “it hurts by itself at night” point to different causes and different urgency — a distinction that is hard to make in a second language under pressure. We treat and explain in English, and our team also works in German, Russian, Turkish, Ukrainian, Arabic, Kurdish and French: English-Speaking Dentist in NRW.
Because the pain is not coming from inside the tooth. The ligament holding it in its socket, the bone at the root tip and the surrounding gum all have their own nerve supply, and any of them can become inflamed. It is also why this pain feels duller and harder to pinpoint than the sharp, cold-triggered pain of a living tooth.
Tenderness when biting usually eases within a few days and is largely gone within one to two weeks. The direction matters more than the calendar: steadily improving is reassuring, steadily worsening is not.
Usually not. Many causes are mechanical and quickly corrected, a high bite being the obvious example, and where inflammation has returned at the root tip a second treatment often keeps the tooth for years. Removal is discussed mainly when the root is split lengthways or too little tooth remains to rebuild: Root canal treatment or extraction? (EN).
Something has usually changed above the root rather than below it: crown margins open, fillings crack, decay starts at an edge you cannot see, and bacteria travel back down into the canal system. What protects these teeth over the years is covered here: How long does a root-treated tooth last? (EN).
Almost certainly. Nothing about a root-treated tooth can be judged from the outside, and comparing a current image with an older one often settles the question.
A root-canal-treated tooth can hurt again, and pain by itself says very little about how serious the situation is. Soreness on biting in the first days is healing. Pain that returns after months of silence is a message from the tissue around the tooth, and it has a manageable explanation far more often than a dramatic one — a crown a hair too high, a grinding habit, a crack, an inflammation at the root tip, sometimes a sinus that has nothing to do with teeth at all. What it never means is wait and see. Note when it hurts, book the appointment, and let an X-ray answer the question.
Zahnarztpraxis Tsypin · Wuppertal. This article was medically reviewed and is provided for information; it does not replace an examination. Updated August 2026.
