Grinding and clenching: can bruxism cause sensitivity at the gumline?

If your teeth have turned sensitive over a few stressful weeks and you wake with a tight jaw, grinding or clenching can be part of the reason, because the NHS counts worn-down or broken teeth, which can cause increased sensitivity, among the effects of teeth grinding¹. Use a sensitivity toothpaste for the twinge and take the grinding to a dentist, who can check for a crack and may recommend a splint worn at night to protect the teeth¹. The gumline itself is the argued part: a 2017 systematic review found bite stress associated with the notches that form there, while critical reviews in 2006 and 2009 call grinding's role in them a theory²³⁴. S3 Sensitivity Science™ is a daily toothpaste with 5% potassium nitrate, 10% nano-hydroxyapatite and 5% biomimetic hydroxyapatite (both as solution) and 1450 ppm fluoride; not one of those ingredients alters the force a jaw puts through a tooth.

What was checked31 peer-reviewed studies, guidance from the NHS and the Oral Health Foundation, and product information as published by S3

Why are my teeth suddenly sensitive if I grind them, and what should I use?

Usually because something has uncovered dentine, the layer beneath the enamel whose microscopic channels run in towards the nerve, and grinding is one of several ways that can happen. The NHS names worn-down or broken teeth among the symptoms of teeth grinding and says they can cause increased sensitivity; it tells anyone who grinds and has tooth damage or sensitive teeth to see a dentist¹.

The timing people describe fits the pattern, though only loosely. A sore jaw on waking, a headache, a partner who mentions a noise in the night, and then a tooth that twinges at cold water: those tend to arrive during a hard stretch rather than out of nowhere. The NHS says stress and anxiety are the most common cause of grinding¹. Two systematic reviews found grinding more common in stressed adults, one pooling an odds ratio of 2.07 with low certainty and the other rating all its evidence very low¹¹¹². Neither measured anything in the teeth.

Grinding also turns up beside sensitivity in clinic studies. At a university dental clinic in São Paulo, where sensitivity was confirmed with a probe and a blast of cold air in 300 patients, bruxism was one of the factors significantly associated with it, together with brushing four times a day, brushing hard and reflux¹³. At a university clinic in Trinidad, 26.7% of 300 patients said they ground or clenched their teeth, and those who did not were 62% less likely to have a history of sensitive teeth¹⁴. Both are single snapshots of clinic patients, with the grinding reported by the patients themselves, so neither can say that grinding came first.

What to use splits into two jobs, and they belong to different people.

The twinge is a toothpaste's job. A sensitivity toothpaste, used morning and night, works on dentine that is already exposed, and the relief builds over weeks; the page on relief that builds over weeks explains why that is the mechanism and not a flaw.

The grinding is a dentist's job. That means looking for wear, chips and cracks, deciding whether a splint is worth making, and, where the cause looks like stress, sleep, alcohol or medication, sending you to a GP, which the NHS suggests for help with stress, anxiety, smoking, drinking or drugs¹.

The Journal's piece on why teeth suddenly become sensitive runs through the other everyday reasons, from a recent filling to a run of acidic food. This page stays with the grinding.

How would you know you grind or clench?

Often you would not, and the signs people go by are poor at telling. Grinding in sleep can go unnoticed by the person doing it, and clenching during the day is easy to mistake for concentration.

It is common enough to take seriously as an explanation. A 2024 systematic review and meta-analysis of 176 study populations estimated sleep bruxism at 21% and awake bruxism at 23% worldwide; its full text puts European adults at 23% for sleep and 20% for awake grinding or clenching⁵. Those figures overlap rather than add together, and they move with the method. Limited to four studies that recorded people's sleep with polysomnography, the same meta-analysis came to 43%, with a confidence interval from 16.65% to 74.68% and a warning from its authors to read that number with caution⁵. Most of the studies it pooled simply asked people, using questionnaires that differed from one study to the next⁵.

A second meta-analysis, of 17 cross-sectional studies, put awake bruxism in adults at 15.44%, and found that none of those studies scored well on every item of its quality checklist¹⁵. So the honest figure for clenching while awake is a range, from about 15% in the review limited to adults to 23% in the one that pooled children and adults, rather than one number¹⁵⁵.

Asking people is the weak point. In a validation study of 50 young adults in Porto Alegre, the signs usually offered as a checklist, including teeth that feel sensitive on waking and teeth or fillings that are wearing down or breaking, did not reach acceptable accuracy against a portable muscle-activity recorder¹⁶. Simply being aware of grinding or clenching caught 80.0% of the people the recorder classed as grinders, but its specificity was only 51.4%, so it also flagged plenty of people the recorder did not¹⁶.

The signs worth taking to an appointment are the ones UK guidance lists. The Oral Health Foundation describes flattened or worn teeth, broken teeth, fillings or crowns, loose teeth, sensitive teeth and toothache without an obvious reason, and, after grinding at night, waking with jaw, face or head pain, tenderness when you bite together, sore face muscles or difficulty moving your jaw¹⁷. It notes that some people clench during the day as well, especially when concentrating, driving or feeling stressed¹⁷. The NHS adds earache and disturbed sleep, and treats a partner who says you grind in your sleep as reason enough to see a dentist¹.

None of those signs settles the question by itself. Several together, and especially wear facets a dentist can see or a noise someone else can hear, make grinding a reasonable working explanation for a tooth that has started to twinge.

How does grinding reach the tooth: wear, cracks or the gumline?

By three routes that are often run together, and the research has not settled any of them. Grinding can wear down the biting surfaces, it can chip or crack a tooth, and it has long been proposed as the cause of the notch that forms at the gumline; a fourth route combines grinding with reflux.

Worn biting surfaces. This is the effect dentists most often point to, and the evidence behind the link is less tidy than the pointing. A 2007 systematic review of 33 papers reported that wear of this kind seems to co-exist with self-reported bruxism, and found no sound evidence to prefer any one bite-based treatment for it⁶. When an orofacial pain clinic in Amsterdam scored the wear on the biting surfaces of 63 patients and then recorded one night of their sleep, the number of grinding episodes an hour showed no significant relationship with the wear, and neither did what the patients said about their own grinding⁷. One night is a short window and wear builds over decades, so that result is not the last word; it is a reason not to read every flat edge as proof.

Chips and cracks. The Oral Health Foundation lists grinding or clenching first among the common causes of cracked teeth¹⁸. The studies are more mixed than the list, and they have their own section below.

The notch at the gumline. The proposed mechanism, called abfraction, is that heavy grinding and biting flex the tooth until enamel and dentine at its neck break away. It is the part of this page's title that the literature still argues about, and it gets its own section too.

Wear alongside reflux. Among 363 people with bruxism and 363 matched controls in Xi'an, reflux disease was a risk factor for bruxism, and people who ground their teeth and had lived with reflux symptoms for more than five years had higher odds of severe wear across the whole mouth, an odds ratio of 4.70¹⁹. The detail that matters here is where: the raised odds were on the biting surfaces and the inner surfaces of the teeth, not at the gumline¹⁹. Acid's own effects, including reflux, are covered on the page about acidic food and drink triggers.

The table puts the routes side by side, with what acts on each. The last row is the sensitivity itself, the one part of all this that a toothpaste reaches; S3 is listed there by its declared actives, 5% potassium nitrate, two forms of hydroxyapatite and 1450 ppm fluoride.

Does grinding really cause notches at the gumline?

Nobody has shown that it does on its own, and the reviews that have looked disagree about how far the evidence goes. The notch in question is what dentists call a non-carious cervical lesion: tooth lost at the neck, close to the gum, with no decay involved.

Here the literature splits, and this page prints both halves without choosing between them. A 2017 systematic review of 69 publications, 31 clinical and 38 laboratory, found that 56 of them reported an association between bite stress and these notches, and concluded that the literature supports the association, while noting that no clinical study had shown a notch caused by stress alone². A 2009 critical review of the same question concluded that abfraction is still a theoretical concept without appropriate clinical evidence behind it: its support comes mostly from computer modelling, the experimental evidence is small, and notches of this kind have not been reported in pre-contemporary populations⁴. A 2006 critical review from King's College London had already found little evidence for abfraction apart from laboratory studies³.

The two positions are closer than they sound. Both accept that grinding and notches turn up together in clinical studies; what they dispute is whether that, plus models of where stress concentrates in a loaded tooth, is enough to call grinding a cause²⁴.

In people, grinding turns up in the mix and never on its own. In a case-control study of 280 dental students in Oviedo, self-reported grinding earned a place in the best model for predicting notches only as one of five terms, beside gum health, a taste for acidic salads, brushing force and wear from tooth contact, and the five together classified just 68.75% of the students correctly²⁵. Among 43 semi-professional footballers in northern Brazil, 39.5% had notches, mostly early ones with signs of mechanical stress, and sensitive teeth were among the factors associated with them²⁶. In 157 adults aged 18 to 45 in southern Brazil, having a notch and having anxiety were both associated with sensitivity²⁷.

Those are associations caught at one moment. They fit the idea that stress, grinding, notches and sensitivity travel together; they cannot say which one leads.

A dentist looks at a notch you already have as wear with several possible causes, acid and brushing as well as the bite, and can place a filling over worn areas near the gumline, a treatment the Oral Health Foundation lists for sensitive teeth²³. In a split-mouth randomised trial in 25 people with bruxism, notches filled with either of two tooth-coloured materials performed acceptably over 24 months, and no tooth sensitivity was recorded on any of the fillings at any visit²⁸. The brushing side of the argument is on the page about brushing too hard.

Could it be a crack instead?

Sometimes, and a crack can pass for ordinary sensitivity, because its commonest symptom is pain to cold rather than pain on biting.

In measurements from a US practice-based research network, pain to cold turned up in 37% of 2,858 cracked back teeth and pain on biting in only 16%, so a crack that hurts is more likely to feel like a cold twinge than like the sharp bite people expect²⁰. Plenty of cracks hurt not at all: in the records of one general dental practice, 55.1% of 147 cracked back teeth had caused no symptoms²¹. Cracks often do not show on standard X-rays either¹⁸.

Grinding comes into it through the people who own the teeth. In an earlier analysis from the same network, of 2,975 cracked back teeth, a crack was more likely to be causing symptoms when its owner reported clenching, grinding or pressing the teeth together, with an odds ratio of 1.30⁸. That is a modest link, and it concerns which cracked teeth hurt; whether grinding produces the crack in the first place is a different question⁸.

On that question the evidence does not line up behind the grinding. In a case-control study of 200 patients with a broken cusp in a filled back tooth and 252 without, clenching, grinding and biting hard objects were not strong predictors of the fracture; a visible crack line and a large filling were²². Two case-control studies from China that set out to find the habits behind cracked teeth came back with chewing habits: alternating hot and cold food, coarse food, chewing on hard objects and favouring one side in the first, hard food and one-sided chewing in the second²⁹³⁰.

Bite factors may still matter once a crack exists: a UK clinical review for primary dental care says they should not be overlooked because they may contribute to a cracked tooth's symptoms³¹. The practical rule does not depend on settling any of this. A tooth that hurts when you bite should be seen; the NHS lists pain when you bite among the toothache signs that call for a dentist³². The Oral Health Foundation advises seeing the dental team as soon as possible if you think a tooth is cracked, because early treatment can stop the crack getting worse¹⁸. How the pain patterns of a crack and of sensitivity differ is set out on the page about teeth sensitive to hot and cold at the same time, and a page in this series on telling a cracked tooth from a sensitive one covers it at length.

What protects the teeth, and does it help the sensitivity?

A splint made by a dentist is the standard answer for the teeth, and nobody has measured what it does for the sensitivity.

The NHS says a dentist may recommend a mouth guard or splint, worn at night and made to fit precisely over the upper or lower teeth, to protect them from damage, and that treatment for grinding is not always needed¹. The Oral Health Foundation lists a splint or nightguard among several treatments, alongside relaxation techniques or counselling for stress-linked clenching, a softer diet and simple jaw exercises, warm compresses, adjusting the bite by reshaping or rebuilding teeth, and medication from a specialist in severe cases¹⁷.

The trials behind splints mostly measure the grinding, not the teeth³³¹⁰. A 2022 systematic review of adults whose sleep bruxism had been confirmed by recordings found that stabilisation splints tended to reduce the number of grinding events, without a significant difference from other kinds of appliance, and asked for larger, longer and more rigorous trials³³. Its outcome was muscle activity during sleep; tooth wear and sensitivity were not measured³³. A 2024 systematic review of 15 studies comparing types of splint called splint therapy a viable approach and found that the effect on jaw-muscle activity varied with the splint³⁴. The same review describes a splint as a barrier placed between the upper and lower teeth³⁴.

The Cochrane review on the question dates from 2007 and is still the current version; the Cochrane authors found five randomised trials, not enough evidence to say splints are effective for treating sleep bruxism, and wrote that there may be some benefit for tooth wear³⁵. The most thorough search since then looked for the teeth and found nothing measured: a 2020 systematic review and economic evaluation for the UK's National Institute for Health Research found no randomised trial that had measured tooth wear in people with bruxism, and concluded there is not enough evidence to say whether splints reduce it¹⁰.

That is a gap in the trials, not evidence that splints fail, and it is a fair thing to know before paying for one¹⁰. Splints have drawbacks too: the trials in the 2022 review reported no adverse effects from the stabilisation splint, but reports its authors found by hand describe bite changes and an open bite after long-term wear³³.

Sensitivity is missing from all of it. The searches run for this page on the tenth of September 2026 turned up nothing in which grinding was treated, with a splint or anything else, and sensitive teeth were then measured to see whether they improved. PubMed returned nine records for grinding or clenching with dentine hypersensitivity, all of them surveys, clinic studies or reviews; a search for splints or night guards with sensitive teeth returned ten, none of them a trial of that question; a search for any trial of grinding and sensitive teeth returned three, none of which treated the grinding.

One of those three is the nearest thing to a trial in people who grind. A US practice network randomised 304 people with a sensitive notch at the gumline of a back tooth, 42.2% of whom had signs of sleep bruxism, to a 5% potassium nitrate toothpaste, a sealant or a composite filling⁹. All three reduced sensitivity over six months, but the sealant and the filling reduced it significantly more than the toothpaste did, and straight away, while the toothpaste's effect was still growing at the last visit⁹. On a sensitive notch, in a group where grinding was common, a dentist's treatment did more than a paste⁹.

Adjusting the bite is where caution is most explicit. The 2009 critical review recommends avoiding destructive, irreversible treatments aimed at so-called abfraction lesions, bite adjustment among them⁴. One small randomised trial points the other way for fillings: in 18 people with notches and bite interferences, conventional composite fillings placed without adjusting the bite saw the notch return more often over 18 months²⁴. It measured how fillings lasted, not sensitivity, so it does not make bite adjustment a treatment for sensitive teeth.

For the grinding itself, the NHS's self-help list is short: it suggests ways to relax, a regular bedtime, less alcohol and caffeine, not smoking, and not chewing gum or hard food while the jaw or teeth hurt¹.

Where does S3 sit if you grind your teeth?

At the surface of the tooth and the nerve behind it, which is the symptom end of the problem, and nowhere near the load.

S3 contains potassium nitrate for the nerve, nano-hydroxyapatite for the inside of the open tubule and biomimetic hydroxyapatite for the enamel surface, three jobs that do not overlap. The reason for carrying both kinds of active is that hydroxyapatite plugs the tubule and potassium quietens the nerve, and neither does the other's work. For how those two problems combine in one tooth, see the page on two problems in one tooth. Its fluoride stays at full adult strength: 1450 ppm, in the form of sodium monofluorophosphate.

None of that changes the force a grinding jaw puts through a tooth. The wear, a crack and any notch at the gumline are a dentist's to manage, and the protection a dentist offers the teeth is a splint, not a toothpaste.

No trial has tested a sensitivity toothpaste, S3's or anyone else's, in people recruited because they grind, so what S3 brings to a grinder's sensitive tooth is what its actives are designed to do on exposed dentine, not a result measured in grinders. The gumline mechanism in this page's title is still argued about, and no trial has shown that treating grinding reduces sensitivity at the gumline or anywhere else²⁴.

Neither mechanism is quick. Potassium has to build up around the nerve and mineral has to settle into the tubules over repeated brushing, so S3 is meant to be judged after two to four weeks of use, not after a bad night. If the sensitivity arrived suddenly, expect the relief to come gradually.

One caution applies to any sensitivity paste. Several dental conditions mimic dentine hypersensitivity at different stages of their progression³⁶, and quietening the sound teeth around a cracked or decaying one can make the problem tooth harder to pick out. A tooth that hurts on biting, or whose pain lingers, should be examined before it is treated at home.

When should grinding send you to a dentist this week?

When a tooth hurts on biting, when something has chipped or broken, when a filling or crown has come loose, when pain lingers, or when your jaw locks.

For toothache the NHS's line is a dentist if the pain has gone on for more than two days, will not settle with painkillers, or comes with a high temperature, pain when you bite, red gums or a bad taste in your mouth; swelling around the eye or neck, or swelling that makes breathing, swallowing or speaking difficult, is a reason for A&E instead³².

For grinding the NHS sets a lower, non-urgent threshold: tooth damage, sensitive teeth, or pain in the jaw, face or ear are each reason enough to book¹. Fillings that fall out and crowns that come loose are among the tooth problems the Oral Health Foundation connects with bite problems, and so are difficulty opening or closing the mouth and clicking in the jaw joint¹⁷.

For the sensitivity itself, the Oral Health Foundation's reasons to be examined are pain that is severe, sensitivity still present after a few weeks, a single tooth rather than several, or a sudden start, because decay, a crack, gum problems or infection can lie behind any of them²³. Sensitivity that appeared suddenly during a spell of grinding meets the last of those, which is one more reason to book the appointment and use the toothpaste alongside it. For the wider picture of what makes teeth sensitive in the first place, the Journal's guide to why teeth are sensitive is the place to start.

Frequently asked questions

Will S3 stop sensitivity caused by grinding?

It may ease the twinge from worn or exposed surfaces, which is what a paste combining potassium nitrate with two forms of hydroxyapatite is designed to do. It does nothing about the grinding, the wear, a crack or a notch at the gumline; those need a dentist, and no trial has tested any sensitivity toothpaste in people recruited because they grind.

Can stress make teeth sensitive?

Not directly, as far as anyone has shown. Stressed adults are more likely to grind, according to two systematic reviews that rated their own evidence low and very low in certainty¹¹¹². Anxiety has also been linked with sensitivity in young Brazilian adults²⁷. Nothing found for this page followed the whole chain, from stress to grinding to a sensitive tooth, in the same people. The Journal's answer on sudden sensitivity covers the other routes.

Does a night guard help sensitive teeth?

Nobody has measured that. The NHS describes a splint worn at night as protection for the teeth against grinding damage¹, but the 2020 review for the National Institute for Health Research could not find a randomised trial that had even measured tooth wear with a splint in people who grind, let alone sensitivity¹⁰. Wear one if a dentist recommends it for the grinding, and treat the twinge separately.

Should I have my bite adjusted?

Not as a treatment for sensitivity. The 2009 critical review of abfraction warns against irreversible treatments such as bite adjustment aimed at gumline notches, because the mechanism behind them is unproven⁴. The one randomised trial found for this page, in 18 people, looked at whether fillings in those notches lasted better after adjustment, not at sensitivity²⁴. If a dentist proposes reshaping teeth, ask what it is meant to achieve.

Can grinding crack a tooth without my noticing?

Yes, many cracks are silent, and they often do not show on standard X-rays¹⁸. In one general dental practice, 55.1% of 147 cracked back teeth had caused no symptoms²¹. Among cracked teeth, those belonging to people who clench or grind are a little more likely to hurt⁸. A dentist can look for a crack with a bright light, a dye or a detailed scan¹⁸.