Sensitivity that lingers after the trigger has gone: what pulpal pain means.

Sensitivity that lingers after the cold or hot drink has gone is usually pulpal pain: it comes from the pulp, the soft core of nerve and blood vessels inside the tooth, rather than from exposed dentine on the surface. It needs a dentist to find out whether the pulp can recover and what will keep the tooth, and the Oral Health Foundation says as much, describing a dull, lingering ache as a possible sign that the nerve inside is irritated, damaged or dying, and telling anyone with one to see a dentist for further checks¹. S3 Sensitivity Science™ was formulated for the two things wrong in dentine sensitivity, a nerve that fires too readily and dentine tubules that are open to the mouth; an inflamed pulp is a different problem, inside the tooth. No toothpaste is a treatment for that tissue or has been tested as one, and what follows is what has been measured instead.

What was checked19 peer-reviewed studies and reviews, the NHS and the Oral Health Foundation

Why does a lingering ache point to the pulp rather than the surface?

Because the pain of sensitive dentine belongs to its trigger, and a pain that carries on without one is usually coming from somewhere else. Dentine is the layer beneath the enamel and the gum line, threaded with microscopic fluid-filled channels called tubules. When their outer ends are open to the mouth, a cold drink or a breath of air shifts the fluid inside them and the nerve endings at the inner end respond. Pain of that kind is short and sharp, arrives with the stimulus, and is called sensitivity only once the other things that can go wrong with a tooth have been ruled out; a 2019 clinical review written for UK primary dental care explains why that ruling-out matters, since the symptoms people report can have several different causes⁸. Pain that goes on after the stimulus has stopped does not fit that description.

The pulp is the living tissue at the centre of the tooth, and pulpitis simply means that it is inflamed. Decay that has crept close to it, a crack or an injury can all reach it, routes that both the NHS and the Oral Health Foundation list⁹¹⁰. Dental work can do it too: the same review notes that a new filling changes the layers of a tooth quickly, and that the pulp can answer with inflammation and a tooth that reacts more to temperature⁸.

The difference in timing has been put on a stopwatch. In a clinical study of 60 adults, clinicians held a cold stimulus to each diagnosed tooth and counted how long the response lasted: in teeth judged able to recover it faded after roughly four or five seconds, in teeth judged beyond recovery it ran to six seconds or longer, and the longer responses went with more of an inflammatory enzyme in the dentine¹¹. Those seconds belong to a dried, isolated tooth and a timed clinical stimulus, which is nothing like a mouthful of tea. A PubMed search run for this page in September 2026, read alongside an earlier search for this group of pages, looked for a duration a person could time at home with a drink and turned up nothing usable, so the page does not offer one. The page on teeth sensitive to hot and cold at the same time sets the timings beside the patterns of cracks and decay.

One delayed pattern is different again. A dull ache that begins a quarter of an hour after coming indoors from the cold, with no pain from drinks at all, has been described in three patients in a hypothesis paper, and the page on sensitive teeth in winter covers it¹².

What do "reversible" and "irreversible" pulpitis mean, and how firm are those labels?

They are working labels for a prediction. Reversible pulpitis is the name for a pulp that is inflamed but expected to settle once whatever is irritating it has been dealt with. Irreversible pulpitis is the name for a pulp that is not expected to settle, and the customary way of relieving it has been to remove the inflamed pulp and clean out the root canal, or to take the tooth out⁷. Symptomatic means it hurts: a 2025 review defined symptomatic irreversible pulpitis by pain that comes on by itself, pain that lingers after heat or cold, or pain felt somewhere other than the tooth responsible⁵. Pulp necrosis means the pulp has died.

In the chair, the line is drawn from the history and a handful of tests. One clinical study of cracked teeth, for example, counted a pulp as reversibly inflamed when there had been no pain out of the blue, the response to cold did not linger, and nothing showed at the root tip¹³.

How often does the label match the tissue? The answer most often quoted comes from a clinical study in one general dental practice in Italy, where 95 teeth that had been given a clinical pulp diagnosis were later extracted for unrelated reasons over five years and examined under the microscope². In that clinical study, a label of healthy or reversibly inflamed pulp matched the tissue in 57 of 59 teeth, and a label of irreversible pulpitis matched in 27 of 32 teeth; bacteria advancing into the pulp were a common finding in the irreversibly inflamed teeth and were absent from the rest².

A second clinical study, open access and from a university clinic in Romania, asked a narrower question and got a less tidy answer. Every tooth in it had already been labelled irreversible, and the clinicians also judged whether the inflammation was acute or long-standing. Across 51 pulps removed during treatment in that clinical study, the judgement matched the microscope in 35 and missed in 16, most often because a pulp called acute in the chair looked chronically inflamed on the slide³. The authors describe the correlation as weak and ask for the classification of pulp disease to be simplified³. The two studies are testing different lines, the first between recoverable and not, the second inside the irreversible label, so their percentages should not be set against each other²³.

Both describe teeth that were already out of the mouth or already being treated, from one practice and one clinic, not a random sample of aching teeth. The direction is still clear enough to state plainly. Even the labels a dentist uses do not always match what the tissue shows, so this page does not tell you which stage your tooth is at.

The table sets the working labels side by side. It is a map for the conversation at the surgery, not a way to label your own tooth, and no toothpaste has a row in it because none belongs there.

Are the labels changing?

Yes, slowly, and it is a live argument rather than a settled change. In 2017 eight endodontists from the Netherlands, Ireland and the UK proposed, in an editorial in the International Endodontic Journal, a new system for grading pulpitis tied to the treatment each grade needs¹⁸. Their system sorts pulpitis into four grades, initial, mild, moderate and severe, so that a dentist can match a grade to a treatment that keeps as much of the pulp alive as possible¹⁹.

The first test of the grading, an exploratory clinical study published in 2026, found it consistent between examiners but hard to confirm under the microscope: two examiners grading 140 patients agreed almost perfectly, but the grade given in the chair agreed only poorly to fairly with a pathologist's reading of 52 extracted teeth, and the authors conclude that its validity against the tissue appears limited¹⁹. A 2026 narrative review by some of the same proposers goes further, arguing that pulp disease should be described as a continuum rather than split into reversible and irreversible, while accepting that no reliable chairside test of how inflamed a pulp is exists yet⁴. The European Society of Endodontology's first fully evidence-graded clinical practice guideline, published in 2023 and built from 14 commissioned systematic reviews and a structured consensus, covers diagnosis and the management of deep decay in teeth with and without spontaneous pain, and names preventing tooth loss as its aim²⁰. This page could not read the guideline's individual recommendations, because its full text would not load when the page was written, so it does not quote them.

Two things follow for a reader. The words in your dental notes may differ from the words on this page, and a change of words is not a change in your tooth. And the case for new words is being made mainly by one group of European endodontists, two of whom also led or co-wrote the guideline, which is worth knowing without being a reason to doubt them.

What will a dentist do, and can the nerve be kept alive?

A dentist may start with the story: when the pain began, what sets it off, how long it lasts, whether it comes on by itself or wakes you, and whether biting hurts. Tests on the suspect tooth and its neighbours may follow, often a cold stimulus, sometimes heat or a small electric current, a gentle tap, and an X-ray. The neighbours matter because an inflamed pulp can make the healthy teeth around it overreact: in a clinical study of 64 patients with symptomatic irreversible pulpitis, the adjacent tooth and the matching tooth in the opposite jaw responded more strongly to cold until the inflamed tooth had been treated¹⁶. No single test settles it. Pooled across 28 studies in a meta-analysis, the cold test's adjusted accuracy was 0.84 and the heat test's 0.72¹⁷. The page on what a dentist checks for sensitive teeth walks through the visit.

If the pulp is inflamed, the options run from keeping all of it to removing the tooth. In pulp capping, the dentist clears the decay and covers the pulp, or the thin dentine left over it, with a protective material. In a partial pulpotomy, a small part of the inflamed pulp is removed where it was exposed; in a full pulpotomy, the pulp in the crown of the tooth is removed and the pulp in the roots is left alive. Root canal treatment removes all of the pulp, cleans the canals and fills them. Extraction takes the tooth out.

The NHS describes root canal treatment as removing an infection from inside the tooth, done under local anaesthetic over two or more appointments that may each last one to two hours, with a crown sometimes needed afterwards if the tooth was badly infected⁹. It also says that an infected tooth left without that treatment may have to come out⁹. Once root canal treatment is done, the tooth no longer has a living nerve, and the Oral Health Foundation notes that it can become more brittle and more likely to break, which is why a crown is sometimes recommended¹⁰.

That is part of why dentistry has been moving towards keeping the pulp alive, and the pooled figures are encouraging. A 2025 systematic review with meta-analyses found that in adult teeth diagnosed with a healthy or reversibly inflamed pulp, capping and pulpotomy techniques each succeeded in 91% to 97% of teeth at 24 months, with no significant difference between them⁵. In teeth diagnosed with symptomatic irreversible pulpitis, the label that has traditionally meant a more invasive approach, partial or full pulpotomy succeeded in 90% in the same review, against 97% in teeth with a healthy or reversible pulp, a gap that fell just short of statistical significance⁵⁶.

Two limits sit beside those numbers. The review pooled adult teeth, including those of young people, and the only five-year figure it gives for full pulpotomy in painful irreversibly inflamed teeth, 78%, comes from a single study⁵. An earlier systematic review of pulpotomy in fully formed teeth with signs of irreversible pulpitis, by authors in Belfast, Dublin and Birmingham, reported clinical success of 97.4% at a year falling to 93.97% at three years, and warned in the same breath that its eight studies were heterogeneous and at high risk of bias, and that properly powered randomised trials are needed before practice should change⁶.

The closest thing to a head-to-head answer is a randomised controlled trial from Jordan. In that randomised trial, 60 molars with decay reaching the pulp and a diagnosis of irreversible pulpitis were given either a full pulpotomy or root canal treatment, and at a year each approach had succeeded in 27 of 29 teeth, with less pain on the first day and fewer people needing painkillers after pulpotomy²¹. A year is not a lifetime and one university centre is not an NHS practice, so none of this promises that your pulp can be kept. What it does show is that a diagnosis of irreversible pulpitis no longer makes root canal treatment the only thing worth discussing, and that asking about the alternatives at the appointment is reasonable.

When a crack is behind the pain, the clock runs differently. In a retrospective clinical study in Singapore of 199 cracked teeth whose pulps were judged recoverable, every tooth was banded and referred for a crown, and within three years 29.1% had moved on to irreversible pulpitis or a dead pulp; teeth that never received a full-coverage crown were far more likely to be among them¹³. The page on one tooth that has suddenly become sensitive describes how a crack tends to show itself.

On the NHS in England, as shown on nhs.uk on the tenth of September 2026, root canal treatment falls in Band 2, which the charges page describes as treatment for an infection or inflammation in the centre of the tooth, at £76.60, and a crown falls in Band 3, at £332.10¹⁵. Those charges may change, some groups are exempt, and the other UK nations run their own systems; the page on free and low-cost NHS dental options explains who pays what.

Is there anything a toothpaste like S3 can do for a lingering ache?

Not for the pulp. A desensitising toothpaste works where ordinary sensitivity starts, at the exposed surface, by quietening the nerve endings at the inner ends of open tubules or by narrowing the tubules themselves, and it does that over weeks of brushing. S3 was formulated for exactly those two surface problems. An inflamed pulp is a different problem in a different place.

This page went looking for evidence that a paste can treat it. The searches were run on PubMed in September 2026. One paired pulpitis with toothpaste, dentifrice, potassium nitrate or desensitising and with treatment or trial, and returned ten records; a second, widened to other potassium salts and to toothache, added nothing new. Neither turned up a single trial of a toothpaste brushed at home as a treatment for an inflamed pulp. The nearest records were a handful of reports from 1983 to 2005 in which potassium nitrate was mixed into a cement that a dentist placed inside the cavity during a filling; that is a dental procedure inside the tooth, the reports are decades old, and they say nothing about a paste.

Even for ordinary sensitivity, the route from a paste to the nerve is argued over. A 1996 review in the journal Pain pointed out that fluid moving outward through the tubules works against potassium moving in, and proposed another explanation for how potassium might still act²². In a laboratory study of 50 extracted molars, potassium nitrate from a toothpaste reached the pulp chamber within 30 minutes in amounts that varied with the formulation, but an extracted tooth has none of the outward fluid flow of a living one²³. Neither paper is a reason to think a potassium paste could treat an inflamed pulp, and this page does not suggest it.

Nothing on this page is a reason to buy a toothpaste: in the published evidence, the only thing that treats an inflamed pulp is a dentist's procedure, and what the NHS suggests while you wait is a painkiller, not a paste²⁴. The nerve-calming ingredient in S3 is aimed at the surface half of sensitivity; it is not a treatment for an inflamed pulp, and no trial has tested it as one.

If you already use a sensitivity toothpaste, keep brushing gently as usual, but do not read a quieter week as the pulp settling. A paste acts on the surface twinge, and the ache from inside is what the dentist needs to hear about.

What helps while you wait, and what does not?

A painkiller, the right door and not much else. The NHS says to see a dentist for toothache that lasts more than two days, and sooner when painkillers do not shift it, when it comes with a temperature, pain on biting, red gums or a bad taste, or when a cheek or the jaw swells; it adds that a GP will not be able to give dental treatment²⁴. For the wait itself its advice is ibuprofen or paracetamol, with a pharmacist's help if you are unsure and no aspirin for anyone under 16, soft food, and keeping away from anything sweet, very hot or very cold²⁴. This page gives no doses and no combinations; the guide to what helps tooth nerve pain tonight goes through the evidence on painkillers.

Antibiotics are the remedy many people expect, and the trial evidence gives no sign that they help this pain⁷. The Cochrane review of antibiotics for irreversible pulpitis, updated in 2019, still rests on a single trial of 40 people in which one group took penicillin and the other a placebo, both alongside painkillers; pain ratings ran almost in parallel for seven days, and the two groups took almost the same number of ibuprofen tablets, 9.20 against 9.60⁷. The reviewers rated that evidence as low certainty and concluded that there is not enough of it to say whether antibiotics ease the pain at all⁷.

Swelling, a fever or a foul taste change the picture, because they point to infection, and whether an antibiotic is then needed is for the dentist or doctor who examines you. The page on sensitivity with swelling or a bad taste sets out those signs and where to go, and the page on tooth pain at night covers pain that wakes you. For the short, ordinary twinge this page keeps contrasting with the pulp, the Journal explains why cold hurts your teeth and why teeth can turn sensitive suddenly.

Frequently asked questions

Will S3 calm a tooth that aches after a hot drink?

Not if the ache stays once the drink has gone. S3 is designed for what goes wrong at the surface in dentine sensitivity, the open tubules and the over-ready nerve, whereas an ache that outlasts the heat is coming from the pulp inside the tooth, where no toothpaste has been tested. The page on hot drinks and coffee explains why heat behaves differently from cold, and the page on teeth sensitive to hot and cold at the same time lays out the timing patterns. What helps this tooth is a dental appointment.

Is there a desensitising toothpaste for immediate nerve pain relief?

Not for the pain of an inflamed pulp, on the first evening or later. Desensitising pastes are tested on exposed dentine over weeks of twice-daily brushing, with most trials running for eight weeks under the consensus guidelines for that research¹⁴, and the searches for this page found none tested on pulpitis. For pain now, the NHS points to ibuprofen or paracetamol as a pharmacist advises, and to a dentist if the toothache goes on beyond two days²⁴.

Does lingering pain mean I need a root canal?

Not necessarily, and only a dentist who has examined the tooth can say. Root canal treatment is one option; others keep part of the pulp alive, and in a randomised controlled trial of 60 molars with irreversible pulpitis, full pulpotomy matched root canal treatment at one year, with less pain on the first day²¹. Which option fits depends on the tooth, the cause and what the dentist finds, and the European guideline on these treatments puts preventing tooth loss at its centre²⁰.

Can an irritated nerve recover on its own?

Reversible means the pulp is expected to settle, but usually once its cause has been dealt with, and the cause, whether decay near the pulp, a crack or recent dental work, is normally something a dentist has to treat. Even with treatment under way, a crack can go on irritating the pulp: in the Singapore clinical study of cracked teeth, 29.1% of pulps judged recoverable progressed within three years although every tooth had been banded and referred for a crown¹³. A pain that fades is not proof either way, and a dentist's check is what tells the difference.

Can antibiotics settle an inflamed nerve?

The trial evidence gives no sign that they do⁷. The 2019 Cochrane review found one small trial of 40 people in which penicillin did no better than a placebo for the pain of irreversible pulpitis, and it rated the evidence as low certainty⁷. Swelling, a fever or feeling unwell are a different matter because they point to infection, and then a dentist or doctor decides what is needed.