Pain & Sensitivity

What does sensitivity to hot and cold mean?

How long the pain lasts tells you both its cause and how urgent it is

Patients who cannot drink cold water on one side always ask the same question: will this pass, or am I missing something? The answer lies not in how severe the pain is, but in how long it lasts. On this page we explain why sensitivity appears, which kind can wait and which should not.

Short answer

Sensitivity to hot and cold means the dentine tubules are exposed on a surface of the tooth that has lost the protection of its enamel or gum. These tubules are microscopic passages that lead to the nerve; a change in temperature moves the fluid inside them, and you feel this as a sudden twinge. What tells them apart is how long it lasts: sensitivity that ends within seconds once the trigger is gone relates to the outer surface, while pain that lasts for minutes shows irreversible inflammation of the tooth's nerve (irreversible pulpitis) and does not get better on its own.

Where sensitivity comes from: Exposed dentine tubules
What tells them apart: Whether the pain continues once the trigger is gone
Emergency sign: Pain that gets worse with heat and eases with cold
Initial assessment: From your X-ray, within 24 hours

Medically reviewed by Bilge Ilgın, Dentist · ImplantologyLast reviewed 2026-08-31

What happens with sensitivity

Beneath the enamel layer lies the dentine. Dentine is not a solid block; it is a tissue riddled with microscopic fluid-filled tubules, and these tubules lead to the nerve in the middle of the tooth. While the enamel is thick, the outer ends of the tubules are closed. The moment the enamel thins or the root surface is exposed, they open up: a sip of something cold moves the fluid inside them, and the nerve reports this movement as a sudden twinge. That mechanism is all there is to sensitivity.

The first cause that exposes the tubules is receding gums. There is no enamel on the root surface that appears; the layer covering it is very thin and wears away quickly with brushing. That is why the sensitivity is concentrated in a narrow strip just below the gum. Behind the recession lies gum disease, or years of brushing side to side with a hard brush and pressing down.

The second cause is wear, and it comes from three directions. Acid dissolves enamel chemically: fizzy drinks, fruit juices, a lemon habit, stomach acid coming up into the mouth. A hard brush and abrasive toothpaste scrape enamel away mechanically. Clenching at night flattens the chewing surface, wearing through the enamel down into the dentine. The result is the same in all three: the protective layer gets thinner, and the sensitivity spreads over a wide area rather than a single spot.

The third cause is decay. When decay breaks through the enamel and reaches the dentine, it both opens up the tubules and brings bacteria closer to the nerve; the sensitivity is concentrated in one tooth, is also triggered by sweet things and gets worse over time. The edge of a filling leads to the same place: the microscopic gap that forms at the margin over the years lets both temperature and bacteria through. Decay progresses under a filling that looks sound from the outside, and only an X-ray shows it.

The fourth is a cracked tooth, and its description is distinctive. A crack forms when you bite something hard, or under the load of years of clenching; it cannot be seen with the naked eye and does not show up on a standard X-ray. This tooth gives a sharp twinge with cold, and the real clue lies in biting: the pain comes not while you bite, but the moment you let go of what you are biting.

There are temporary causes too: the few weeks after a deep filling, a root surface left exposed after a scale and polish, the days after whitening. In all of them, noticeable sensitivity to cold appears and fades over the weeks. If it gets worse instead of fading, or turns into sensitivity to heat, that shows the cause is no longer temporary.

Which sensitivity can wait, and which cannot

This distinction looks not at how severe the sensitivity is, but at how it behaves. If you recognise yourself in the second list, do not wait; the descriptions there are about the nerve inside the tooth, not its outer surface.

The tooth can be saved

A twinge that ends within seconds once the trigger is goneIf the pain ends the moment the cold water leaves your mouth, the problem is on the outer surface of the tooth and the nerve is healthy. What needs doing is sealing the exposed tubules and removing the cause that opened them.
Sensitivity concentrated where the gum has recededIf the twinge comes from a narrow strip just below the gum and returns when the brush touches it, its source is an exposed root surface. With the right toothpaste, the right brushing technique and a protective varnish, it fades within weeks.
After a new filling, a scale and polish or whiteningIncreased sensitivity to cold in the first few weeks after a procedure is normal. What you need to keep an eye on is the direction: if it is easing a little more each week, things are on track.
Mild, widespread sensitivity in more than one toothIf the sensitivity has spread not to one tooth but to an area or the whole mouth, the cause behind it is not a single area of decay but something widespread: a habit that wears away the enamel, or widespread gum recession. What needs treating here is not a single tooth; it is the habit causing the wear and, if there is recession, the gum disease behind it.

Saving it is unlikely to hold

Pain that lasts for minutes after the trigger is goneIf the pain continues after you have swallowed the cold water and takes minutes to die down, the nerve of the tooth has become irreversibly inflamed. This does not get better on its own, and toothpaste will not make it go away. What needs doing is root canal treatment.
Pain that gets worse with heat and eases with coldA tooth that throbs with hot tea and eases when you hold cold water in your mouth shows that the nerve is severely inflamed or has died. This description is the emergency sign with the highest diagnostic value; it needs to be seen within the same week.
Sharp pain when you bite and let goPain in a single tooth that strikes not at the moment of biting but at the moment of release is the classic description of a cracked tooth. As the crack grows, the options narrow: a tooth that could be protected with a crown today goes for extraction once the crack reaches the root.
Pain that comes on by itself and gets worse at nightPain that starts without any trigger and becomes severe when you lie down has long since gone beyond sensitivity. If swelling in the gum or facial swelling has been added, this is an infection and needs treatment the same day.

How we find the cause

Sensitivity is not a diagnosis but a symptom shared by several causes. The sequence below exists to sort out which cause is at work in your case; at the end, you know which tooth it is, why, and how urgent it is.

1
Send us your X-ray
If you have a panoramic X-ray or a CBCT scan, send it through the form; we will write to you within 24 hours about what the picture looks like. If you have pain that comes on by itself or gets worse with heat, do not wait for our reply; see the nearest dentist, because there the price of delay is the nerve of the tooth.
2
We talk through the history of the pain
What triggers it, how many seconds it lasts, whether it is in one tooth or an area, and whether it comes at night directly determine the decision. The patient's own description narrows down the cause considerably before the examination.
3
Clinical examination and vitality test
We apply cold to the suspect tooth, measure how strong the reaction is and how long it lasts, and compare it with the neighbouring teeth. Light tapping on the tooth and a bite test, one point at a time, are added to this. We assess the amount of recession, worn surfaces and the edges of old fillings in the same session.
4
Imaging
An X-ray shows decay under fillings and between teeth, inflammation at the root tip and the bone level. If a crack is suspected, we move on to a cone beam CT (CBCT) scan; fracture lines that do not show up on a standard X-ray are revealed here.
5
We confirm the suspect tooth
Pain often spreads to the neighbouring tooth or the opposite jaw; the tooth the patient points to is not always the one responsible. If uncertainty remains, the teeth are isolated one by one and the test is repeated. We do not skip this step, so that a procedure that cannot be reversed is not started on the wrong tooth.

What is done

These are not alternatives to one another but paths that differ by cause. The sequence starts with the least invasive and, as long as the nerve is healthy, ends there too.

Desensitising toothpaste and varnish at the clinic

The potassium nitrate it contains makes it harder for the nerve to pass on the stimulus, and its fluoride compounds seal the openings of the exposed tubules. The effect builds up: it appears within weeks with regular use. A high-concentration fluoride varnish applied at the clinic does the same job faster. This route is right for exposed root surfaces and wear.

Removing the cause

As long as the habit of acidic drinks and brushing with pressure continues, the tubules you have sealed open up again. If there is clenching at night, a night guard comes into play. This is the step that ends sensitivity for good; the toothpaste only makes it manageable.

Cleaning out the decay and replacing the filling

If the cause is decay, or the edge of an old filling has opened up, the solution is sealing that gap. As decay progresses through the dentine, the sensitivity increases; once it reaches the nerve, the procedure we will be discussing is no longer a filling.

Gum treatment

If gum disease lies behind the recession, sealing the sensitivity only deals with the surface of the problem. If the pockets are not cleaned, the progressing inflammation exposes more of the root and wears away the bone underneath. In some areas an exposed root surface is covered with a gum graft.

Root canal treatment

If the pain lasts for minutes after the trigger is gone, or gets worse with heat, the nerve of the tooth has become irreversibly inflamed. Root canal treatment cleans out this nerve and keeps the tooth in the mouth. The longer you wait, the more the inflammation moves down to the root tip; at that point, bone loss is added to the picture.

Extraction and an implant

If the tooth is too badly decayed to be saved or the crack has reached the root, the question is what will replace it. For a single tooth, a single-tooth implant is the right route; for that, carrying on with your own dentist is enough. Our field is situations where sensitivity is the last sign of a mouth neglected for years: many missing teeth or the full mouth.

What happens if it is ignored

We are not writing this to frighten you, but so that you can ask the right question whichever dentist you see. What gets missed with sensitivity is always the same: the symptom is silenced and the cause is left in place.

Sensitivity toothpaste has its limits

Toothpaste seals exposed dentine tubules and makes it harder for the nerve to pass on the stimulus. It does not clean out decay, close a crack, repair a filling whose edge has opened, or bring a dead nerve back. For the right cause it genuinely works; for the wrong cause it turns down the volume on a problem that is progressing.

Pain stopping does not mean healing

When a tooth that has reacted to cold for weeks goes quiet, patients feel relieved. But the reaction also ends when an inflamed nerve dies. The inflammation moves down to the root tip and often progresses without causing any pain; swelling, an abscess and bone loss appear at the end of this silent period, and sometimes they are seen only on an X-ray.

A crack does not close on its own

Keeping watch on a cracked tooth means allowing the crack to progress. As long as it stays within the enamel and dentine, the tooth can be protected with a crown; once the line reaches the root, there is nothing left of it that can be saved. How long this takes cannot be known in advance: a crack can stay where it is for years, or reach the root with a single hard bite. The risk of waiting lies exactly in this unpredictability.

Receded gum does not grow back

An exposed root surface does not cover itself over again, and as long as the cause continues, the recession gets worse. The same surface both causes sensitivity and decays much faster than enamel.

The wrong reflex makes sensitivity worse

Stopping brushing an area because of a sensitive tooth lets plaque build up and speeds up recession and decay. Brushing harder, on the other hand, scrapes away even more enamel. Both are done to reduce sensitivity, and both increase it.

What to expect afterwards

The course below varies with the cause. With sensitivity limited to the outer surface, the process is measured in weeks; when the problem has reached the nerve, treatment starts with a procedure.

The first two weeks
If you have switched to a desensitising toothpaste, its effect builds up during this period; rubbing it onto the sensitive area with a finger and leaving it works better than spreading it with a brush. During the same period, stop using a hard brush and do not brush your teeth straight after acidic drinks; you would be scraping away softened enamel.
Weeks four to eight
With sensitivity coming from the outer surface, there is a noticeable improvement in this period. If nothing has changed, or it has got worse, the cause is not on the outer surface; this is the point at which the diagnosis needs to be revisited.
If root canal treatment has been done
Sensitivity to hot and cold ends after the procedure; the nerve that carried the stimulus is no longer there. Tenderness when biting in the first few days is normal and fades within a few days. Because a tooth that has had root canal treatment is more prone to breaking, back teeth are given a crown.
If the tooth could not be saved
If a single tooth is involved, the gap is closed with a single implant, and you can carry this out with your own dentist. Our field is many missing teeth and the full mouth; there, the process works like this: in the protocol we use, the implants lock mechanically into the hard basal-cortical layer deep in the jaw, and this is where the stability to carry the fixed bridge in the same week is established. A conventional implant is placed in the alveolar bone at the top, which shrinks with tooth loss, and loading is postponed until fusion is complete; that is where the difference comes from. Adding bone and months of waiting do not come into it, and at the end of the three clinical days you leave with your final fixed teeth.

Message us right away if

Pain lasting for minutes after the trigger is gone. This description points to irreversible inflammation of the tooth's nerve. Waiting does not save the tooth; it only increases the scope of treatment.
Heat making the pain worse and cold easing it. The nerve is severely inflamed or has died. In this situation you need to see a dentist within the same week.
Swelling or discharge in the gum, or facial swelling. These are signs of active infection; if a high temperature or difficulty swallowing has been added, go to A&E the same day.

What determines the cost

We do not give a single figure on this page: with sensitivity, the path may end with a tube of toothpaste, or it may extend to root canal treatment, a crown, or extraction and an implant; the difference between them is large. We give you the right figure once we have seen the X-ray and carried out the examination. Send us your X-ray and we will share the scope with you in writing. These are the items that determine the price:

The cause of the sensitivity: Fluoride varnish, replacing a filling, gum treatment and root canal treatment are different procedures, with different timescales and numbers of sessions. A figure given before the cause has been identified is bound to change at the clinic.
How many teeth are affected: Widespread sensitivity caused by wear does not stop at one tooth. A plan built around a single tooth and a plan covering the whole mouth are calculated separately.
What goes on top of the tooth: A crown on a back tooth that has had root canal treatment is a separate item. A crown is also what holds a cracked tooth together; its material and the laboratory work have a direct effect on the total.
The scope if the tooth cannot be saved: The cost is worked out according to how many teeth the extraction and the replacement involve. For patients who decide while the bone is still in place, the bone grafting item never comes into play.

Frequently asked questions

Does desensitising toothpaste really work?

For the right cause, it does. The potassium nitrate it contains makes it harder for the nerve to pass on the stimulus, and its fluoride compounds seal the openings of exposed dentine tubules; the effect appears within weeks with regular use. But it does not treat decay, a crack, a filling whose edge has opened or an inflamed nerve. If there is no change at all after four weeks of use, the cause is not on the outer surface of the tooth.

Why is sensitivity to heat more serious than sensitivity to cold?

Cold is a stimulus that even a healthy nerve reacts to; the pain is brief and passes. Pain that gets worse with heat, and on top of that eases with cold water, shows that the tissue inside the tooth is severely inflamed or has died. In the first case the conversation is about the outer surface of the tooth; in the second, root canal treatment.

The pain lasts a few seconds but is very severe. Is that a bad sign?

Duration, not severity, is what decides it. A twinge that ends the moment the trigger is gone relates to the outer surface of the tooth, however sharp it is, and the nerve is healthy. A dull ache that lasts for minutes, on the other hand, is a much worse picture even though it feels less bothersome. When you describe it to your dentist, tell them the seconds, not the severity.

Will a sensitive tooth get better on its own?

With temporary causes it will: sensitivity after a deep filling, a scale and polish or whitening fades within weeks. Sensitivity caused by decay, a crack or receding gums does not go away, because the cause stays in place. The pain stopping sometimes means not healing but the nerve dying; in that case the pain goes quiet, but the inflammation progresses silently at the root tip, and there is no telling in advance when it will come back.

Should I stop brushing a sensitive tooth?

No, do the exact opposite. Not brushing that area lets plaque build up; it speeds up gum recession and decay on the root surface, which means it makes the sensitivity worse. Clean it with a soft brush, without pressing, using a circular motion. Wait thirty minutes after having something acidic; brushing softened enamel straight away scrapes it off.

Does root canal treatment end sensitivity?

Yes. Root canal treatment cleans out the nerve that carries the stimulus; after the procedure, there is no more sensitivity to hot and cold in that tooth. Tenderness when biting in the first few days is a separate thing and fades within a few days. We put a crown on a back tooth that has had root canal treatment, because a tooth that has been hollowed out is more prone to breaking.

Several of my teeth are sensitive. Is your fixed teeth in three days method right for me?

Most likely not, to be frank. Widespread sensitivity is usually caused by wear, and what needs doing there is not replacing the teeth but stopping the cause that is wearing away the enamel. The protocol we use is for the full mouth or many missing teeth. If we look at your X-ray and think it is not suitable for you, we tell you that in writing too.

Sources

Send your X-ray and we will tell you which option is realistic for your tooth.

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Next step

Send your X-ray and we will talk through the options.

Share your CBCT or panoramic X-ray. We will write back within 24 hours on which option is realistic for your tooth.

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