A cracked tooth or a sensitive tooth? What the pain pattern can and cannot tell you.

If one tooth has suddenly started to twinge, it may be ordinary sensitivity from exposed dentine or it may be cracked, and the pain cannot tell you which, because the commonest complaint from a cracked tooth that hurts is pain to cold¹. What to use first is a dental examination, not a toothpaste: a sensitivity paste belongs to sensitivity spread across several teeth, or to a single tooth a dentist has already looked at. S3 Sensitivity Science™ combines potassium nitrate for the nerve with two forms of hydroxyapatite and full adult-strength fluoride in one daily toothpaste, and none of those ingredients closes a crack.

What was checked26 peer-reviewed studies, the Oral Health Foundation and the NHS

Is my suddenly sensitive tooth cracked, and what should I use?

It might be, and no description of the pain will settle it, so the first thing to use is an appointment. The Oral Health Foundation's advice on sensitive teeth names two situations that fit a single twinging tooth exactly, a tooth affected on its own and pain that began suddenly, and lists a cracked tooth among the explanations for either⁵. The NHS puts a cracked or damaged tooth on its list of causes of toothache, alongside decay, a broken filling and grinding⁶.

Most people arrive at this question with four beliefs, and each is weaker than it sounds. The first is that a cracked tooth hurts when you bite; in the largest set of measurements, cold was the commoner complaint by more than two to one¹. The second is that an X-ray would show the crack, and often it does not⁷. The third is that a tooth which calms down on a sensitivity toothpaste cannot have been cracked, when cracked teeth quieten by themselves as well⁸. The fourth is that a crack means losing the tooth, and for teeth that are found and treated the reverse is true⁴.

Every study of how cracked teeth feel works in one direction. It begins with teeth a dentist has already identified as cracked and records what they do, which is how the numbers on this page were gathered¹². None runs the other way, starting from teeth that feel sensitive and counting how many turn out to be cracked. A PubMed search run for this page in September 2026, pairing cracked teeth with prevalence, cold or sensitivity and patients, returned two records, and neither did it. So this page cannot give you odds: no study has worked out how often a tooth that feels sensitive turns out to be cracked.

That is why the practical answer does not depend on the odds. If one tooth has suddenly become sensitive, a sensitivity toothpaste is the wrong first purchase and a dental examination is the right one. Keep brushing the whole mouth with a fluoride toothpaste as usual, chew on the other side for now, and book⁶. The Journal's piece on why teeth suddenly become sensitive covers the reasons that apply across the whole mouth; this page is about the one tooth.

How does a cracked tooth usually feel?

Most often like a twinge to cold, less often like a jab on chewing, and very often like nothing. In a practice-based observational study in which 209 dentists across the United States enrolled 2,858 back teeth with a visible crack, fewer than half, 45%, had any symptom; 37% hurt to cold, 16% hurt on biting and 11% hurt without a trigger¹. Among the teeth that did hurt, about two thirds had one kind of pain only, and in 78% of those the one kind was cold¹. The authors' own conclusion is the line most symptom checkers leave out: biting pain is treated as the most reliable sign of a crack, and it is not the commonest one¹.

A second, independent sample gives a similar picture from a different angle. When a dental school in Nevada searched eight years of its clinical notes, 893 adult patients had a cracked tooth recorded, and symptoms were written down for 41% of them; where they were, the notes most often said simply "pain", then sensitivity to temperature, then pain on biting or chewing⁹. A chart holds only what a clinician chose to write, so the true share with symptoms may be higher, but temperature still comes before biting.

A hospital sample turns the order round. Among 561 patients diagnosed with cracked teeth at one hospital between 2021 and 2024, in a retrospective cohort study, discomfort on biting was the main symptom, in 72.73%¹⁰. That is a difference in who was counted rather than a contradiction to average away. People who go to a hospital with a cracked tooth have usually gone because chewing hurts, whereas the practice network enrolled visible cracks whether or not they hurt, deliberately taking in more painful teeth than a random sample would contain¹¹. Among the 435 teeth that network dentists went on to treat, a cold test had provoked pain in 53% and a bite test in 37% before treatment¹². Which symptom looks typical depends on which teeth you start from, and a single tooth at home has no sample to belong to.

The classic description in the clinical literature is narrower than the folklore. A 2002 review of cracked tooth syndrome describes discomfort or pain while chewing something hard that stops when the pressure comes off, from a tooth the patient often cannot identify, sometimes in someone who has had several dental treatments that did not help¹³. Pain at the moment of letting go of a bite is part of clinical teaching too; in the papers read for this page it appears in introductions, as background citing older work, rather than as something anyone measured⁹. The table below labels it that way.

The same blur happens with an inflamed nerve. In a clinical study of 64 patients with one badly inflamed tooth, a cold test also drew an exaggerated response from healthy teeth nearby and from the opposite jaw, and that faded after the problem tooth had root canal treatment¹⁴. Pain is a poor address label, which is one more reason a dentist tests each tooth in turn.

Can the pain pattern tell a crack from sensitivity?

It can raise suspicion, and it cannot clear a tooth. A 2019 clinical review for UK primary dental care, covering both conditions, warns that the complaints people bring can come from more than one cause, so a firm diagnosis of hypersensitivity is hard to reach, and adds that the bite deserves attention because it may feed the symptoms of a cracked tooth¹⁵. A 2020 overview for practitioners goes further: there are no universally accepted guidelines for telling dentine hypersensitivity apart from the conditions that mimic it, and several of them imitate it at different stages as they progress¹⁶. A PubMed search run for this page in September 2026, pairing cracked teeth with dentine hypersensitivity or differential diagnosis, returned twelve records: reviews, a case report, an editorial and papers on other questions, with nothing that measured how accurately symptoms separate the two.

The symptoms also move. In the one-year follow-up of the practice network, which watched 1,850 cracked teeth that were left untreated, 32% of patients reported a change in their pain, and falls outnumbered rises by 23% to 10%⁸. Cold pain changed more than biting and spontaneous pain put together⁸. Over three years, 68% of untreated teeth that hurt to cold at the start were free of it at some visit, and 19% of untreated teeth with no cold pain at the start developed it, half of them losing it again¹⁷. A twinge that comes and goes is what a crack does as well as what sensitivity does.

The overlap cuts both ways. The investigators who followed those teeth suggest that some of the cold pain recorded in cracked teeth may have been ordinary dentine hypersensitivity rather than damage done by the crack¹⁷. A tooth can be cracked and sensitive at once, and a dentist who finds exposed dentine has not thereby shown that there is no crack.

The table lists six patterns a reader might notice, what each leans towards, what a dentist would check, and how good the evidence is for the row. Its last column says what a sensitivity toothpaste can do, S3 included: hydroxyapatite works on open tubules and potassium on the nerve, so for most of these rows there is nothing for it to act on. No row can rule a crack out.

Why might an X-ray and a sensitivity toothpaste both miss it?

Because an X-ray shows a crack only when the crack lines up with the beam, and a sensitivity toothpaste acts on the very symptom a crack most often produces. That alignment problem is the Oral Health Foundation's own explanation for why a standard film so often comes back clear on a cracked tooth, and the one trace a long-standing crack may leave on it is bone loss beside the root⁷. In the practice network's own records, a crack was visible on a radiograph for 5% of the 435 teeth dentists treated¹².

Even advanced fractures are missed. In a retrospective clinical study of 98 teeth whose crack, split or root fracture was confirmed by looking at the tooth after it had been taken out, the fracture line could be seen on 45% of ordinary periapical X-rays and on 65% of cone-beam CT scans, the kind of three-dimensional scan a dentist may suggest²⁰. Those teeth were damaged badly enough to lose, so an early crack in a tooth worth saving is likely to be harder still to catch. A 2021 review makes the same point from the equipment side: an ordinary radiograph settles the question only when the fracture is obvious, and cone-beam CT is too coarse to be relied on for the fine crack of an early cracked tooth²¹. And in a survey of 427 dentists in Greece, the UK and other European countries, using a cone-beam scan was not associated with any change in diagnosis or treatment plan²².

Fillings hide cracks as well. In one general practice's records of 147 cracked back teeth, most cracks could not be seen at all until the old filling had been removed², and the Oral Health Foundation counts large fillings among the things that weaken a tooth enough to crack⁷. A tooth that turns sensitive some time after a filling is covered by the Journal's page on sensitivity after a filling, and a crack under a filling is one of the reasons a dentist will want to see it rather than wait.

The toothpaste half is an inference, and this page labels it as one. The commonest symptom of a cracked tooth, pain to cold, is the symptom S3's actives are designed to reduce, so a paste like S3 could quieten the one signal a crack gives while the crack itself stays where it is¹. Nobody has measured whether that happens. A PubMed search run for this page in September 2026, pairing desensitising products or sensitive toothpaste with masking or delayed diagnosis, returned twenty-one records; the dental ones among them were about blinded examiners, face masks, covered laboratory samples and hiding stains on enamel, and none examined a delay in diagnosing a crack or anything else. No study has tested whether a sensitivity toothpaste delays the diagnosis of a cracked tooth; the concern on this page is drawn from how cracks present.

A quieter tooth tells you little, for a second reason. Untreated cracked teeth quieten by themselves, as the follow-up studies above show, and a desensitising paste's effect takes weeks to build⁸. Relief after a fortnight on a paste fits sensitivity, a crack whose cold pain has faded on its own, or both at once.

What cracks teeth?

Heavy or uneven forces on back teeth, often in teeth already weakened by large fillings, though what has been measured for each is an association and not a cause. The Oral Health Foundation's list of causes runs from grinding or clenching, large fillings and biting on hard things such as ice, fruit stones or bones, to knocks, gum disease weakening the bone around a tooth, and sudden changes of temperature, such as hot food followed by something cold⁷.

Two case-control studies from China tested some of those habits. In the first, 35 patients with cracked teeth were compared with 70 matched controls, and four chewing habits stood out as independent risk factors: alternating hot and cold food (odds ratio 3.30), eating coarse food (2.73), chewing on one side (2.47) and chewing on hard objects (2.09)²³. In the second, 100 patients with painful cracked teeth were matched with controls; eating hard food and chewing on one side came out again, alongside decay, a deep overbite, a Class II bite, worn biting surfaces and steep cusps, and the cracks were commonest in people in their thirties and in the upper first molar²⁴. Both are small, and a case-control design shows which habits travel with cracks, not that the habit did the cracking.

Age shows up in every sample, at different points. The Nevada dental-school records had the most patients with cracked teeth in the 45 to 54 age band⁹, the hospital cohort in people in their forties¹⁰ and the second Chinese case-control study in people in their thirties²⁴; each reflects who attends that clinic as much as who cracks a tooth. One laboratory finding offers part of a mechanism: root dentine that has turned transparent with age has closed tubules and a fracture toughness roughly 20% below that of normal dentine²⁵. How sensitivity itself changes over the decades has its own page in this series.

Grinding is the cause dentists name most readily: 95.2% of the 427 dentists in the European survey linked cracked teeth with bruxism or bite problems, and 92.4% with metal fillings²². Those percentages are beliefs, not measurements. Whether grinding itself cracks teeth is a question for the page on grinding and clenching, which goes through what has actually been measured. The Nevada notes recorded amalgam in 76.6% of the restored cracked teeth and resin composite in 23.4%, with no uncracked teeth to set them against⁹.

What will a dentist do, and what happens if you wait?

Expect questions first, then a close look with light and magnification, a bite test on individual cusps, and sometimes a band around the tooth or a second visit before anyone is sure; a crack found while the nerve is healthy is usually kept. In the survey of 427 dentists, the methods used most for a painful cracked tooth were taking a history and using magnification, each by 79.5%, a clinical examination by 75.9% and a bite-test device by 69.6%²².

The tool matters. In a clinical study of 46 cracked teeth, biting on a dedicated bite-test tool reproduced the pain in 91.3%, while biting on a wet cotton roll reproduced it in 32.6%¹⁸. So a tooth that does not hurt when you bite on a crust at home, or on a cotton roll in the chair, has not passed a test. A 2021 review adds a caution: some researchers advise against loading a suspect cusp at all, because the pressure may extend the crack²¹. Dentists also use a dye that collects in the crack line, a light shone through the tooth, which a crack interrupts, and the operating microscope, and a band or ring cemented round the tooth works as a temporary splint and a test at once: if the pain does not settle with the band on, the diagnosis may be wrong or the nerve may need treatment²¹.

None of these is reliable alone. A 2026 systematic review of 12 diagnostic-accuracy studies found that light-based methods such as transillumination reached roughly 64% to 70% accuracy, picking up most cracks but flagging some that were not there, that standard X-rays and cone-beam CT had limited sensitivity for fine cracks, and that optical coherence tomography did best but is not widely available; its conclusion is that no single method finds every type of crack and that tests should be combined³. A diagnostic-accuracy study on 30 teeth extracted for a suspected crack, part-funded by a student research grant from a toothpaste manufacturer, put numbers on the visual tests against micro-CT: the most accurate, transillumination, was right 65.3% of the time, its false alarms came partly from harmless craze lines, the four examining dentists agreed with one another only fairly, and the experienced pair scored 64.6% against 56.8% for the recent graduates²⁶.

Waiting is neither a disaster nor free. Over three years, 3% of the cracked teeth in the practice network fractured, 12% of untreated teeth showed some progression of the crack, and 98% of all the teeth were still in the mouth, according to the investigators' review of their own registry¹¹. A 2024 systematic review and meta-analysis found that leaving a cracked tooth unrestored and watching it succeeded in 80% of cases at three years; the authors offer that route only when the crack causes no pain, and strongly recommend a full crown once it does⁴.

What treatment achieves depends on the nerve and the restoration. In a prospective cohort study of cracked teeth whose nerve was irritated but judged able to recover, each held first in an orthodontic band and then covered, 81 of the 106 teeth followed for a year kept a healthy pulp, and those that failed had spent longer in the band before their diagnosis was settled²⁷. In the hospital cohort, among 67 patients with early-stage cracks, one-year success was 78.05% with a full crown against 50.00% with a composite filling, and a longer spell of discomfort on biting before treatment was associated with progression to pulpitis¹⁰. That second finding is the practical argument against waiting on a paste, with the limit that a retrospective design cannot show the delay was the cause¹⁰.

A treated tooth usually settles. Among the network patients whose cracked tooth was treated at or soon after enrolment, the share reporting any pain fell from nearly two thirds to just over a quarter by the next yearly visit¹⁷. Where the nerve is already inflamed beyond recovery, root canal treatment comes first, and the page on sensitivity that lingers after the trigger has gone explains how that pain behaves.

Where does S3 sit if you are not sure which it is?

As the everyday toothpaste for the whole mouth while you wait for the appointment, and never as the thing that decides whether you need one. A sensitive tooth has two things wrong at once, a nerve that fires too readily and dentine tubules that are open, and S3 was put together for that pair: potassium calms the nerve, nano-hydroxyapatite works inside the tubule and biomimetic hydroxyapatite on the surface. A crack is a third kind of problem. It is a fault running through the tooth, and nothing in a toothpaste bonds, splints or crowns it.

This is where the page argues against its own product. For a single tooth that has just started, the first purchase is an examination and a tube of anything, S3 included, comes second. S3's actives are aimed at pain to cold, which is the symptom a cracked tooth most often has, so the better S3 does its job on a cracked tooth's twinge, the easier that tooth is to forget¹. That is an inference rather than a finding, and the masking search described above turned up nothing on it.

Two more things the tube cannot tell you. Relief from S3 builds over weeks, because potassium accumulates around the nerve and mineral is laid down brush by brush, and it is judged at two to four weeks; a twinge that eased in a day or two is not evidence about a crack either way. In a double-blind randomised trial of 120 adults, funded by a company that makes one of the pastes it tested, a potassium nitrate toothpaste had not yet separated from a plain fluoride paste on the probe test at day three, and its effect on the cold-air score grew through week eight²⁸. And the trials behind sensitivity actives enrolled people with dentine hypersensitivity: the 2026 network meta-analysis of 93 randomised trials pooled their cold-air and probe scores²⁹. Cracks were not their subject.

If a dentist examines the tooth and finds exposed dentine and nothing else, S3 is a reasonable daily toothpaste for it, with full adult-strength fluoride at 1450 ppm as sodium monofluorophosphate. The page on relief that builds over weeks explains that timetable, and the page for sensitivity that keeps climbing on a sensitive toothpaste covers what to rule out next.

When should a single sensitive tooth be seen this week?

When it hurts to bite or to let go of a bite, when the ache stays after the cold has gone, when a piece of tooth has broken away or a filling suddenly feels different, or when it has gone on for more than a couple of days. The Oral Health Foundation's page on cracked teeth tells anyone who thinks they have one to see their dental team as soon as possible, with pain when biting or chewing, sensitivity to hot or cold and pain that comes and goes as the signs to watch, because early treatment can stop a crack getting worse⁷.

The NHS threshold for toothache is two days, brought forward when painkillers do not help or when the pain comes with a high temperature, pain on biting, red gums, a bad taste, or a swollen cheek or jaw; swelling around the eye or in the neck, or swelling that makes it hard to breathe, swallow or speak, is a matter for A&E⁶. While you wait, its advice for a sore tooth includes soft foods and not chewing on that side, which for a possible crack is the most useful line on the list⁶.

The other one-tooth explanations each have a page of their own. A filling that is new, high, loose or broken, decay reaching the dentine, and gum pulled back from a single root are set side by side on the page on one tooth suddenly sensitive. A twinge that sweet things set off, or a dark spot, points towards sensitivity or a cavity. An ache that lingers, throbs or wakes you belongs with sensitivity that lingers after the trigger has gone, and whether a sensitivity toothpaste is worth trying on one tooth at all is the subject of the page on sensitivity toothpaste for a single tooth. The page on teeth sensitive to hot and cold at the same time covers what the timing of a pain can show.

Take three things to the appointment: which tooth you think it is and how sure you are, what sets it off and how long the pain lasts, and anything you have bitten on or had done to that tooth lately. Say if you have been using a sensitivity toothpaste and whether the twinge changed, because a quieter tooth is part of the history, not the end of it.

Frequently asked questions

Should I use S3 while I wait to find out whether a tooth is cracked?

Yes, as your ordinary twice-daily toothpaste for the whole mouth, with its fluoride at the full adult strength of 1450 ppm. The part to guard against is the appointment slipping. A cracked tooth's cold twinge can fade by itself⁸, and a paste built for sensitivity may dull it further over the weeks S3 takes to work, so if the tooth has ever hurt to bite on or to let go of, report that even if the cold has gone quiet.

Will a crack show on an X-ray?

Often not. Only if the crack runs in line with the beam, according to the Oral Health Foundation, so standard X-rays often miss it⁷. Even in teeth taken out with a confirmed fracture, the line was visible on 45% of ordinary X-rays and 65% of cone-beam CT scans²⁰. Across 12 diagnostic-accuracy studies, a systematic review found both kinds of image had limited sensitivity for fine cracks³. An X-ray still earns its place, because a crack that has been there a while can show as bone loss around the root⁷, but a clear film does not clear the tooth.

Can a cracked tooth stop hurting on its own?

Yes, and that is part of the difficulty. In practice-network teeth left untreated for a year, pain fell more than twice as often as it rose⁸, and over three years most biting pain disappeared at some visit whether or not the tooth was treated¹⁷. The Oral Health Foundation is clear that a cracked tooth cannot heal itself⁷, so a tooth that has gone quiet still needs to be looked at if it was ever sore to bite on.

Does a cracked tooth always need a crown or a root canal?

No. Some cracks need nothing: the Oral Health Foundation describes craze lines as common, painless and needing no treatment, and lists bonding or smoothing for small cracks⁷. Across the practice network, about a third of visibly cracked teeth were treated over three years, mostly with crowns, and 14% of those needed further treatment¹¹. Root canal treatment comes in when the nerve is involved: in a retrospective cohort study of 199 cracked teeth whose nerve was judged able to recover, 29.1% went on to an inflamed or dead pulp over at least three years of follow-up, more often when no full crown was placed¹⁹. A crack that runs deep into the root can mean the tooth has to come out, the Oral Health Foundation adds⁷.