The Signs That Send People for a Root Canal, and Why None of Them Settle It
Published patient sources list six or seven signs. Every one of them also belongs to conditions that need something else entirely — which is why this chapter will not tell you what you have.
What the published lists say
The American Association of Endodontists lists these as signs that treatment may be needed: "Severe pain while chewing or biting", "Pimples on the gums", "A chipped or cracked tooth", "Lingering sensitivity to hot or cold, even after the sensation has been removed", "Swollen or tender gums", and "Deep decay or darkening of the gums".
The American Dental Association describes the situation rather than a checklist: a severely damaged or decaying tooth, or a serious tooth infection, with pain and swelling, and an abscess that may form inside the tooth or in the bone around the end of the root. It names four ways the pulp gets into that state — "a deep cavity", "repeated dental procedures", "a cracked or fractured tooth" and "injury to the tooth".
That is the whole of what those two sources publish. Everything beyond it, on this site at least, is qualification.
Why a list of signs is not a diagnosis
Take the strongest one. Lingering sensitivity to hot or cold that outlasts the thing that caused it is the sign most often described as characteristic — and it is still not conclusive, because a tooth can be irritated rather than irreversibly inflamed, and the two feel similar from the outside and are treated completely differently.
Now take the weakest. Pain on biting is on the AAE's list, and it is also what a cracked filling does, what a high restoration does, what a cracked root does, and what a tooth with a problem in the ligament around it does. Four different answers, four different treatments, one sensation.
And then the one that catches people out entirely. MedlinePlus, run by the US National Library of Medicine and reviewed on 5 February 2026, lists among the causes of toothache: an abscessed tooth, an earache, injury to the jaw or mouth, a sinus infection, tooth decay, tooth trauma — and heart attack, which it notes "can include jaw pain, neck pain, or toothache". A list of dental signs cannot see any of that.
What actually decides it
An examination and an X-ray, and sometimes a test of whether the pulp is still alive — the Washington endodontic schedule has a line for exactly that, a pulp vitality test at $74.40, which tells you the profession treats "is this nerve alive?" as a measurement rather than a guess.
The ADA is direct about why this cannot happen at home. On its page about do-it-yourself dentistry it says: "Dental exams include diagnostic X-rays to determine the best course of treatment, which cannot be done at home", and "It's vital to seek dental recommendations and treatment directly from a dentist". It describes DIY dental trends in general as "rarely backed by scientific evidence" and as ranging "from ineffective to harmful".
That is why this chapter has no flowchart in it. Building one would mean pretending that a sequence of yes-and-no answers can substitute for looking at the tooth, and it cannot.
Searching for how to stop it yourself
A large share of the traffic for this subject is people looking for a way to deal with a nerve at home rather than in a chair. It is worth saying what is wrong with that plainly rather than pretending nobody searches it.
An inflamed or infected pulp sits inside a sealed chamber in the middle of a hard tooth. Nothing applied to the outside of the tooth reaches it. Painkillers change how you feel about it; they change nothing about what is happening inside. Antibiotics can slow an infection that has spread beyond the tooth, which is why they are sometimes prescribed alongside treatment, and they cannot clean out a chamber that no blood supply reaches. This is not a matter of effort or courage. The chamber is closed.
The one thing that genuinely changes the situation is opening the tooth, and that is not a thing that can be done to yourself. The NHS page on toothache, reviewed on 1 July 2024, adds one practical note worth repeating: "Do not go to your GP as they will not be able to give you dental treatment."
When the question stops being about a root canal
Some of these signs belong in a different category altogether. From the NHS page on dental abscess, reviewed on 18 March 2026: ask for an urgent dentist appointment or get help from NHS 111 if you think you have a dental abscess, with symptoms including a swollen face or jaw, swollen glands in the neck and a high temperature.
And from the same page, the list that means emergency services rather than a dental appointment — 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 sudden problems with your eyesight, have a lot of swelling in your mouth, or are finding it hard to open your mouth. In the United States, 911 or an emergency department.
MedlinePlus sets a lower and simpler bar for seeking care at all: a severe toothache, a toothache lasting longer than a day or two, or "fever, earache, or pain when opening your mouth wide".
What to do with a list you cannot act on
Use it as a reason to book, and as a note to take with you. Which sign, how long, what brings it on, whether it wakes you, whether it has changed. That is genuinely useful information to the person examining you, and it is the part only you have.
The appointment that answers the question is the cheapest thing on all three fee schedules this site reads: a problem-focused exam at $39.52 to $104.00, plus an X-ray of the tooth at $8.00 to $40.00. The rest of the numbers — the treatment, and the crown that follows it — are on our page pricing a root canal from three published schedules.
If the exam comes back saying the decay has not reached the pulp, the question becomes a different one, and it has its own chapter: when a filling is enough and when it is not.
Questions about the signs
How do I know if I need a root canal?
You do not, and neither does any website. The signs published by the endodontists' association and the ADA are real signs, and each of them also belongs to several other conditions with different treatments. What settles it is an examination, an X-ray, and often a test of whether the pulp is still alive — the last of which is a priced line item on one of the schedules we read, which tells you it is a measurement rather than an opinion.
Does a tooth always hurt if it needs a root canal?
No, and that is the most important limitation of any symptom list. A pulp can die quietly, and the tooth then stops producing the pain that would have sent you in. This is one of the reasons routine check-ups and X-rays find things that nobody had noticed.
Is sensitivity to cold always a sign?
It is on the AAE's list, but with a specific qualifier: sensitivity that lingers after the hot or cold thing has gone. Brief sensitivity that stops as soon as the stimulus does is extremely common and belongs to a long list of other causes. The distinction matters and it is still not enough on its own.
My tooth stopped hurting. Am I in the clear?
Not necessarily, and this is the trap. Pain stopping can mean the problem has resolved, and it can mean the pulp has died while the infection carries on underneath without a nerve left to complain. Those two situations feel identical and look completely different on an X-ray.
Can I take painkillers and wait?
You can take them, and the NHS page on toothache suggests paracetamol or ibuprofen while warning against exceeding the recommended dose of any painkiller — the dose is on the packet and a pharmacist is the person to ask. What painkillers do not do is treat the cause; they change your experience of a situation that carries on regardless. The NHS's own threshold for seeing a dentist includes toothache that does not go away when you take painkillers.
Carry on
The prices behind all of this are on what a root canal costs on three fee schedules.
Anaesthetic and Sedation for a Root Canal
Local anaesthetic is the default and is included in the procedure — it has no separate line on any schedule we read. Sedation is a different thing entirely, billed by the quarter hour, and it is worth knowing what that costs before you say yes.
Do You Need a Crown After a Root Canal?
On the schedules that price both, the crown is roughly half of the total bill — and the endodontists' own guidance says it depends mostly on which tooth it is. Back teeth generally get one; front teeth often do not.