Not always constant. A tooth that needs a root canal doesn't have to hurt every hour of every day. If the nerve inside is dying slowly rather than all at once, pain can flare for a day or two, fade for a week, then return. The pattern that matters most is whether the discomfort lingers after hot or cold, spreads toward your jaw or ear, or wakes you at night, not whether it's bothering you right now. Swelling, a bad taste, or pain that lingers more than 30 seconds after cold usually means the nerve is compromised, and it's worth scheduling an exam soon. A quiet day doesn't rule that out. Only cold testing, percussion testing, and an X-ray can confirm what's actually happening inside the tooth.
A Nerve Can Die Slowly, Not All at Once
A tooth's nerve doesn't switch off like a light. It can die gradually, over weeks or months, often after a deep cavity, a crack, or an old filling that has failed underneath. Early on, the nerve tissue is still partly alive. It reacts to temperature and pressure, then settles again as inflammation rises and falls inside the tooth. That's why pain can feel like it comes in waves. You might notice a sharp jolt with cold, then nothing for several days.
It usually isn't random, even though it feels that way. It tracks with inflammation building up inside a closed space with nowhere to drain, then briefly settling. Eventually, in many cases, the nerve tissue dies completely and the pain stops for good, not because the tooth healed, but because the nerve that was signaling pain no longer can.
Fading Pain Doesn't Always Mean Healing
This is the misunderstanding I run into the most. A patient's tooth hurt for a few days, then went quiet, and they take that as a sign the problem resolved on its own. I understand why. For most parts of the body, pain fading usually does mean healing. Teeth are different. Once the nerve inside a tooth is significantly damaged, it doesn't regenerate.
If the ache went away because the nerve died rather than because the infection cleared, the tooth can sit quietly for weeks or months while a low-grade infection builds near the root tip. You may only find out when it flares again, sometimes as a more serious problem than the one you started with.
Three Tests That Tell Me What's Happening Inside the Tooth
When a patient describes pain that comes and goes, I don't rely on how the tooth feels that day. I run a few specific tests to see what's actually happening inside it.
Cold testing means placing a cold stimulus against the tooth and timing how it responds. A healthy nerve reacts briefly and settles within a couple of seconds. A dying nerve may react strongly and linger, or not react at all.
Percussion testing is simpler than it sounds. I gently tap on the tooth and compare how that feels to the teeth next to it. Tenderness to tapping often points to inflammation around the root tip, even on a day the tooth isn't aching on its own.
Then I take an X-ray to look for bone changes near the root tip, a dark shadow where bone has started to break down in response to infection. Here's the part that surprises people: a tooth can already have a dying nerve and still look normal on an X-ray, especially early on. That's why I weigh all three tests together instead of relying on any single one.
What Helps While You Wait for Your Appointment
- Avoid chewing directly on the tooth until it has been evaluated
- Rinse with warm salt water if the area feels tender
- Take an over-the-counter pain reliever as directed on the label
- Keep brushing the tooth gently rather than avoiding it
Call your dentist's office and describe the on-and-off pattern, not just today's symptom
Signs That Mean Call Today, Not Next Week
Most intermittent pain isn't an emergency. A few signs move it into the same-day category: facial or gum swelling near the tooth, a fever, a bad taste that keeps returning (which can mean drainage from an infection), pain that wakes you from sleep, or pain that spreads toward your ear, jaw, or neck. Any of these can mean an infection has moved beyond the tooth itself, and waiting can let it spread further before treatment starts.
Root Canal or Extraction: How the Decision Gets Made
If testing confirms the nerve is dying, the real decision isn't whether to treat it. It's whether the tooth is worth saving. That comes down to how much healthy structure remains, whether a crack extends below the gumline, and whether the surrounding bone still supports the tooth well.
Most patients who can save the natural tooth choose to, since it tends to feel and function closest to what they had before. But a root canal isn't automatically the right call for every tooth, which is why the exam findings, not just the diagnosis, guide the recommendation.
Questions Worth Asking at That Appointment
- Is the nerve confirmed dead, or still borderline based on today's tests
- What did the X-ray show at the root tip specifically
- What happens if I wait and monitor instead of treating now
- How much of the natural tooth structure remains
- What would a crown or restoration cost after the root canal itself
A dentist who has actually run cold testing, percussion testing, and an X-ray should be able to answer each of these clearly. If the answer is vague, ask what specifically was found.
Questions I Get Asked in the Chair
Can a dying nerve heal on its own?
No. Once nerve tissue inside a tooth is significantly damaged, it can't repair itself the way skin or gum tissue can.
Why did my X-ray look normal if something is wrong?
Bone changes near the root tip can take time to show up on an X-ray. Early on, the tooth can look normal even while the nerve inside is failing.
Does percussion testing hurt?
It's a gentle tap, not a hard knock. Most patients feel mild tenderness at most, and it helps show whether inflammation has reached the bone around the root.
What happens if I just wait and see?
Some patients choose to monitor for a short period. But if the nerve is truly dying, waiting doesn't stop that process. It usually means treating a more advanced problem later instead of a smaller one now.
Will the pain come back if I skip treatment?
I can't predict that for any specific patient. But when a nerve is dying and left untreated, symptoms often do return, sometimes more severe than before.
The Short Answer, Restated
Intermittent pain isn't proof that a tooth is fine. It's often the opposite: a nerve dying gradually instead of all at once. Cold testing, percussion testing, and an X-ray, read together, are what actually tell us whether a root canal is needed, not how the tooth happens to feel on the day you're examined. If your pain has faded but the tooth has ever ached with hot or cold, or you've noticed any swelling, it's worth having it checked rather than waiting for it to hurt constantly.
A nerve doesn't have to hurt constantly to be dying. It just has to be damaged.
Related reading
This connects to a couple of other things patients often ask about: how a dentist decides between a root canal and extraction and tooth pain that suddenly stops on its own. For more, see the pieces on deciding whether severe tooth pain is a true emergency and pain specifically on releasing a bite. For the broader topic list, see the full dental topics index.
What an X-ray Can and Cannot Tell Us
An X-ray can show visible decay, bone loss around the tip of the root if an infection has been present long enough to change the bone, and the general size and shape of the nerve chamber. What it often cannot show is early or reversible nerve inflammation, since the bone around the root can still look completely normal in the early stages even while the nerve inside is already dying. A normal-looking X-ray does not rule out a tooth that needs a root canal -- it only means the infection, if there is one, has not yet reached the point of visibly changing the bone.
What Changes the Treatment Decision
The clearest deciding factor is how the tooth responds to a pulp vitality test (cold or electric testing) compared to a healthy tooth nearby, not just how the pain feels day to day. Other findings that shift the decision include tenderness when the tooth is tapped, any swelling or drainage near the root, and whether an X-ray shows early bone changes at the root tip.
When the cold test result isn't clearly one way or the other, here's what I'm looking at. On a healthy tooth, the cold feeling goes away within about 10 to 15 seconds. On a tooth that may need a root canal, the cold feeling can linger longer than that, start after a delay, or not register at all. A few things can throw the test off. A porcelain crown can block the cold from reaching the tooth. A narrowed nerve pathway (a change called calcification) can dull the response. And some teeth have more than one nerve branch, so part of the tooth can test healthy while another part doesn't.
When the result is genuinely unclear, I usually wait a week or two and retest, or refer the patient to a root canal specialist (an endodontist). If someone can't wait that long, extraction is sometimes offered as an option.
Why Tooth Pain Can Come and Go
Pain flares, then fades, then returns
This pattern can be one clue the nerve is dying slowly
Your dentist may check three things
- Cold test: how the tooth responds, and for how long, compared with a healthy tooth nearby
- Percussion test: a gentle tap to check for tenderness near the root
- X-ray: looking for bone changes near the root tip
A few things can make the test hard to read
- A porcelain crown can block the cold from reaching the tooth
- A narrowed nerve pathway (calcification) can dull the response
- Some teeth have more than one nerve branch, so part of the tooth can test healthy while another part doesn't
When the result is genuinely unclear
Dr. Chung's takeaway: a cold test that isn't clearly normal or abnormal isn't a dead end. A crown, calcification, or a multi-rooted tooth can all make the result hard to read, so his usual next step is a short retest or a referral to an endodontist, not an immediate decision either way.
When Tooth Pain Comes and Goes
- Pain that comes and goes doesn't rule out a nerve that's slowly dying
- A quiet tooth isn't necessarily a healed tooth
- Three tests help clarify what's happening: a cold test, a tap test, and an X-ray
- Crowns, calcification, and multi-rooted teeth can all make the cold test hard to read
- Call the same day for swelling, fever, or pain that keeps getting worse
What Happens If You Wait
A dying nerve does not need to keep hurting constantly to keep dying, and the infection it can lead to does not need constant pain to keep spreading in the bone. The real risk of waiting through intermittent pain is that the infection can progress from something treatable with a root canal to something that eventually requires extraction, or in less common cases spread beyond the tooth itself. Intermittent pain is not the same as low risk.
Questions to Ask Your Dentist
- Did the pulp vitality test come back clearly normal, clearly abnormal, or ambiguous
- Does the X-ray show any early changes at the root tip
- If we wait and monitor, what specific change would mean it is time to treat
- How soon would a delay meaningfully change the treatment needed
When to Call Today, Not Wait for a Routine Appointment
Call the same day if the intermittent pain is joined by swelling in the gum or face, a bad taste from the area, tenderness when you tap the tooth, or if pain-free stretches start getting shorter instead of longer. Those are signs the situation is actively progressing, not just continuing to come and go.
The Bottom Line
Pain that comes and goes can still mean a nerve that needs a root canal -- the pattern of the pain is not a reliable way to rule that out on its own. A pulp vitality test and an exam are what actually answer the question, not how the pain has felt so far.
Intermittent does not mean minor. Let the exam findings, not the pain pattern, decide.