Potassium nitrate not working: why nerve calming alone can leave the tubules open.

A potassium nitrate toothpaste that is not working usually has one of four explanations: the pain is not dentine sensitivity, the paste has not yet had the weeks it needs, your trigger is one where potassium's pooled evidence is thin, or the tubule that carries the cold inwards is still open. Only the last of those is changed by a different tube, and if the pain throbs, lingers after the cold has gone or wakes you at night, it is not a toothpaste question at all. S3 Sensitivity Science™ keeps the same 5% potassium nitrate for the nerve and gives the tubule to two forms of hydroxyapatite, nano-sized for inside it and biomimetic for the surface, so it is a potassium paste with an occluder added rather than an alternative to potassium.

What was checked24 peer-reviewed studies, product information as published by each brand, and guidance from the NHS and the Oral Health Foundation

Is it sensitivity, or is the nerve inside the tooth inflamed?

Nobody can tell from how it feels, and that includes a dentist listening to your description. A 2012 systematic review of 18 diagnostic studies found the evidence insufficient to say what toothache, or an abnormal reaction to heat or cold, reveals about the condition of the pulp, and not one of those studies reached high quality¹. A 2013 overview of how dentine hypersensitivity is diagnosed makes the same point about sensitivity itself: people describe their history and symptoms so differently that the description does not allow a reliable diagnosis, and the condition is confirmed only by exclusion, once pulpitis, a cracked tooth, decay, a leaking filling and the other causes on its list have been examined for and ruled out⁸. A validated pain questionnaire that patients complete themselves goes no further: it scores dentine sensitivity in one group with the early, recoverable stage of an inflamed pulp⁹.

That matters here, because the potassium nitrate trials further down enrolled people as cases of dentine hypersensitivity. The 1997 consensus guidelines for those trials ask for the pain to be provoked on purpose, by probe, by cold and by a jet of air, against negative and benchmark control pastes¹⁰, and a 2026 scoping review of 72 papers found that few studies apply every part of the accepted definition, least of all the part that excludes other causes of tooth pain¹¹. Nobody has tried a potassium nitrate toothpaste on toothache: a PubMed search run for this page on the tenth of September 2026, for potassium nitrate toothpaste with pulpitis, toothache or pulpal pain, returned no records.

Cold does not settle it either. In a practice-based clinical study of 2,858 back teeth with a visible crack, pain to cold was the commonest symptom, present in 37% of them, and more common than pain on biting¹². The study began with teeth already known to be cracked, so it cannot be read in reverse; what it does show is that hurting to cold is no evidence against a crack¹².

If what you call nerve pain throbs, lingers after the cold has gone, wakes you, or starts when you bite, stop troubleshooting the toothpaste. The NHS wants a dentist to see toothache that lasts more than two days, toothache that painkillers do not shift, and toothache that comes with a high temperature, pain on biting, red gums, a bad taste or a swollen cheek or jaw, and it sends people to A&E when swelling reaches the eye or neck or makes it hard to breathe, swallow or speak¹³. Sensodyne's own UK FAQ tells people whose pain or sensitivity persists to visit a dentist because it may indicate a different problem, and names a cracked tooth and decay among the causes of tooth pain other than sensitivity. The page on the pain pattern that tells sensitivity from something else takes those patterns one at a time, and the Journal's piece on why teeth suddenly become sensitive covers the everyday causes.

Have you given potassium nitrate the weeks it needs?

Not if you are judging it inside a fortnight. When a 2019 systematic review of 74 randomised trials arranged treatments by how soon their effect became statistically significant, potassium nitrate sat only in the long-term band, absent from both the up-to-seven-days band and the up-to-one-month band².

Early readings from one large trial give that curve its shape. In a double-blind randomised trial of 120 adults, funded by Procter & Gamble and set up to test a potassium nitrate paste, a stannous fluoride paste made by the funder and an oxalate paste against a plain fluoride control, potassium nitrate was already ahead of the control on the cold-air score at day three, and its lead grew to 20.4% at week two, 34.6% at week four and 44.3% at week eight¹⁴. On the dental probe it had not separated from the control at day three and had by week two, and the gain was still growing at the last reading taken while people were brushing with it.

Brushing for longer did not hurry it in the one trial that tried. In a 12-week examiner-blind randomised trial of 141 adults whose funding is not stated in its record, people brushing twice a day with a 5% potassium nitrate gel-to-foam paste for 45 seconds improved from baseline as much as people brushing for two minutes, on air, on touch and on their own pain ratings, and there was no untreated group to size the change against¹⁵.

Every published reading from day three to week twelve is laid out on the page on how soon potassium nitrate makes a difference. The working rule is plain. Under four weeks, keep going and write down the date you opened the tube. Between four and eight weeks, the trial curves say the paste may still be building. Past eight weeks with nothing changed, carry on down this page, and use the page on how long to give a new sensitivity toothpaste to judge any replacement fairly.

Which trigger hurts, and what has potassium been shown to help?

Touch, most clearly; a jet of cold air, less surely; a cold drink, least surely of all, because the pooled evidence there is thin and the one network that analysed cold stimuli separately found potassium indistinguishable from plain fluoride³. The reviews disagree about potassium, and laid out stimulus by stimulus the disagreement looks less like noise and more like a pattern.

The table below takes each pooled review in turn for potassium alone, and adds the one large trial with readings from day three. Where a review did not report potassium separately for a stimulus, the cell says so.

Three things come out of that table. The dental probe is where potassium's case is strongest, and the 2020 network's only moderate-certainty grade for potassium is on touch³. The cold-air score gives potassium a low-certainty result in both networks that report it separately³²⁰. And for a cold drink the pooled evidence is thin: the Cochrane review had a single thermal trial, which favoured potassium, and did not pool it¹⁶, the 2026 network built no cold-water analysis²⁰, and the 2020 network's four cold trials left potassium indistinguishable from plain fluoride³. Single trials fill some of the gap. In a four-week double-blind randomised trial of 30 adults, 5% potassium nitrate beat a non-desensitising paste on cold water at four weeks, and lost to a calcium sodium phosphosilicate paste in the same trial²¹.

If a cold drink is what sets your teeth off, potassium nitrate is being asked to do the job it has the thinnest pooled evidence for. The page reading the Cochrane review line by line sets out that review's verdict in full.

Two more results belong beside the table, because they cost the ingredient something. The 2026 network rated stannous fluoride's two-week cold-air result as its only high-confidence finding, and potassium's as low²⁰. In the industry-funded trial of 120 adults, 28% of the potassium nitrate group reached complete relief in at least one test tooth by week eight, and 53% of the stannous fluoride group did; stannous fluoride is an active S3 does not contain¹⁴. On the cold-air score itself, the three actives in that industry-funded trial finished the eight weeks without a significant difference between them¹⁴.

What is in your tube, and would a higher level help?

Almost certainly 5% if the tube prints a level at all, and no UK tube recorded prints a higher one. Twelve products in this site's category review of UK sensitivity toothpastes list potassium nitrate in their published ingredients, read from brand and retailer pages on the ninth of September 2026, and three of them print how much: all three say 5%, and one of the three is a US listing whose UK availability was not established.

This page compares ingredients and stated actions only, not clinical performance, based on what each brand states about its own formula. Prices and formulations may change; always check the pack. The table gives each tube as its brand or retailer lists it, with the row of the category review of UK sensitivity toothpastes by ingredient it comes from, and counts a second active only where the list names a desensitising or occluding ingredient.

Laid side by side, the twelve lists are more alike than their packs suggest: ten pair potassium nitrate with sodium fluoride and two with sodium monofluorophosphate, eleven are water-based, and one, S3's, puts an occluding active beside the potassium. Silica, a copolymer or a zinc salt appears in several of the others; this page treats those as part of the base, not as a second desensitising active.

Would a higher level help? Nobody knows, because no tube offers one and no published toothpaste comparison of that strength against a higher one turned up in the searches behind the page on where the potassium nitrate figure comes from. Every trial in the Cochrane pooling used 5% potassium nitrate against the same paste without it¹⁶. What manufacturers have changed is the paste around the salt. Scientists employed by the maker of one 5% potassium nitrate toothpaste described, in laboratory work, an activated silica they developed to raise the potassium ion activity their paste delivered²², and an earlier in vitro account by manufacturer-affiliated researchers found that the deposit their own potassium nitrate paste left on dentine was made of copolymer and silica²³. So two tubes printing the same figure need not behave alike in a dish, on a manufacturer's own laboratory account, and nobody has measured whether that difference reaches a person²².

Has it worn off?

Not on any evidence published so far. No trial has tested whether people become tolerant to potassium nitrate, and the one trial that stopped it on purpose and kept measuring found most of the benefit still there: in the double-blind trial of 120 adults funded by Procter & Gamble, potassium nitrate's lead over the control on cold air was 44.3% at week eight and 35.8% after three weeks back on a plain paste¹⁴. A second manufacturer-funded double-blind trial, of 127 adults, built a single day off the paste into its schedule and lost nothing measurable over that day, although its placebo group drifted in the same direction⁴.

The Oral Health Foundation tells people to keep using a sensitive toothpaste to maintain the effect²⁴. The one industry-funded trial that stopped and measured found most of the effect still there three weeks on, and nobody has measured what happens after that¹⁴. What a longer break costs is set out on the page on stopping a potassium nitrate toothpaste, and the page on a missed week works out what a lapse does. If your paste seemed to fade after months of daily use, look first at the other checks on this page.

Is the tubule still open, and what does adding a tubule-blocking ingredient change?

Probably, because the potassium salt was never what closed it, and combining it with a second active in one paste has been tried in four trials, every one of them run or paid for by the maker of the test paste or silent about who paid. In the companion microscope arm of a four-week double-blind randomised trial of 30 adults, 5% potassium nitrate left the dentine tubules unoccluded²¹; where a whole potassium toothpaste has partly closed them in the laboratory, the plug has been traced to the paste's silica and copolymer, as the page on whether potassium nitrate blocks dentine tubules sets out. The general case against a paste that works only on the nerve is made on the page on why that leaves the door open; this section is about what has actually been tried.

The closest test of the question held potassium nitrate steady and added one ingredient. In a double-blind randomised trial of 127 adults, whose authors all worked for or were funded by the manufacturer, Lion Corporation, a paste of 5% potassium nitrate with 2.18% aluminium lactate beat the same potassium nitrate paste on air at four weeks and on air and touch at eight, and both beat a placebo paste from week two⁴. Aluminium lactate is not hydroxyapatite, so this trial settles that the design can be run, not what hydroxyapatite would add.

A Bristol trial changed two things at once. In a 14-day examiner-blind randomised trial, a toothpaste carrying aluminium lactate, potassium nitrate and hydroxylapatite reduced sensitivity more than a control paste with potassium nitrate alone at every reading, and the relative risk reduction in Schiff sensitivity rose from 55% straight after the first brushing to 88.6% at day 14⁵. The abstract gives no number of participants and the record no funding statement, and with two ingredients added nothing in the result can be pinned on the hydroxyapatite⁵.

An older trial kept the potassium and changed the fluoride salt. In an eight-week examiner-blind randomised trial of 101 adults, whose funding is not stated in its record, a paste of 5% potassium nitrate with stannous fluoride reduced touch and air-blast sensitivity more than a paste with the same 5% potassium nitrate and sodium monofluorophosphate, at four weeks and at eight⁶. Sodium monofluorophosphate is the fluoride salt in S3, the one on the losing side of that comparison.

One trial ran it the other way round. In an eight-week double-blind randomised trial of 85 adults, paid for by Sangi, the maker of its test toothpastes, adding 5% potassium nitrate to a 10% nano-hydroxyapatite paste eased pain to ice-cold water more than the same paste without it at weeks two, four and six but not at week eight, and eased pain to air at weeks four, six and eight⁷.

Across the four, something improved at some time point whenever a second active joined potassium nitrate in one paste, in trials run or paid for by the maker of the test paste or silent on who paid⁴⁵⁶⁷. None of them set potassium nitrate with hydroxyapatite against potassium nitrate alone, which is the comparison that would show whether a paste built like S3 adds anything to the tube you already have. The pooled figure most often quoted for that pairing rests on two randomised trials and 140 patients in the 2020 network meta-analysis, which the page on potassium nitrate and hydroxyapatite together unpacks³.

Where does a paste that keeps potassium nitrate and adds hydroxyapatite, like S3, fit?

It changes the tubule job and leaves the nerve job as it was. S3 keeps 5% potassium nitrate, the same level printed on the other two potassium nitrate tubes that print one, and hands the tubule to nano-hydroxyapatite inside it and biomimetic hydroxyapatite on the surface, with 1450 ppm fluoride as sodium monofluorophosphate kept in. Every limit of the potassium evidence on this page applies to the nerve half of S3, because it is the same salt at the same strength. No trial has set that combination against potassium nitrate alone, and nobody can yet say what the added tubule job is worth in a mouth.

The two hydroxyapatites are there to occlude and the potassium to desensitise; one cannot stand in for the other. S3's list also carries potassium chloride as a second potassium source, which describes the ingredient list and nothing more, since no trial has tested whether two potassium salts calm a nerve more than one. For someone meeting the idea for the first time, the Journal sets out the two causes of sensitive teeth in a few hundred words.

What the added tubule job cannot change is just as specific. If the pain is not sensitivity, S3 is the wrong purchase, like every other tube on this page. If the paste simply has not had its weeks, S3 runs on the same slow clock, judged at two to four weeks, and the potassium trials above were still improving at week eight. If your trigger is a cold drink, hydroxyapatite brings a cold gap of its own, set out on the page for hydroxyapatite users who are still sensitive, and the Journal's article on how sensitive toothpastes work and why yours might not be working gives a shorter version of the two-mechanism argument.

When should you stop troubleshooting and see a dentist?

When a check points away from the toothpaste, and at the latest when sensitivity has outlasted a few weeks of honest use. That is the Oral Health Foundation's line, and it adds three more: pain that is severe, pain confined to one tooth, and pain that arrives suddenly, any of which can mean decay, a crack, gum problems or an infection²⁴. For someone past eight weeks on a potassium paste with nothing changed, the few-weeks line has already been crossed.

A dentist has options no tube does. The Oral Health Foundation lists applying a desensitising treatment to the tooth, recommending a high-fluoride toothpaste, placing a filling over worn areas near the gumline and treating gum disease or other causes, on a page supported by an educational grant from a toothbrush maker²⁴. None of those requires you to have given up on potassium nitrate first, and a tooth that turns out to be cracked is worth finding early.

For pain that behaves like sensitivity, short, sharp and gone when the cold goes, the guide to UK alternatives by active ingredient sets the remaining options side by side, and the page on why sensitivity toothpaste stops working covers the explanations this page has not.

Frequently asked questions

If potassium nitrate has not worked for me, will S3?

Nobody can promise that for one person, and this page will not. Nobody has even described who potassium nitrate leaves sensitive: a PubMed search for this page on the tenth of September 2026, for non-responders, treatment failure or persistent sensitivity with potassium nitrate, returned a single record, an electrophysiology experiment in cats. S3's nerve active is the same 5% potassium nitrate you have been using, so S3 is not a second attempt at the nerve. What it adds is the tubule job, given to nano-hydroxyapatite inside the channel and biomimetic hydroxyapatite on the surface, and no trial has tested that combination against potassium nitrate alone. If you try it, change nothing else in your routine, judge it over weeks rather than days, and use the page on how long to give a new sensitivity toothpaste to keep the test fair.

Is there a stronger potassium nitrate toothpaste?

Not among the UK products recorded: where a potassium nitrate tube prints its level, the figure is 5%, and none prints anything higher. Nobody has published a toothpaste comparison of that strength against a higher one, so a bigger number would have no tested meaning, and the development work a manufacturer has published, in laboratory testing, went into the paste's base instead²². The page on where the potassium nitrate figure comes from goes further.

Would a potassium nitrate mouthwash help where the toothpaste has not?

The two pooled analyses disagree about what a potassium rinse changes. A 2023 systematic review and meta-analysis of nine randomised trials found potassium-salt rinses ahead of control rinses on touch from two weeks and on air from four²⁵. A 2017 systematic review and meta-analysis of seven placebo-controlled trials, mostly of potassium nitrate rinses, found a difference in people's own ratings of everyday pain at eight weeks and none on the touch or air tests²⁶. Both compared a rinse with a rinse, so neither answers whether adding one to a toothpaste that has stopped helping would change anything; the page comparing potassium nitrate mouthwash with toothpaste weighs the two forms.

Can a potassium nitrate toothpaste calm toothache?

Nobody has tried it: a PubMed search run for this page returned no record of a potassium nitrate toothpaste used on pulpitis, toothache or pulpal pain, and the consensus guidelines those toothpaste trials follow are written for dentine hypersensitivity¹⁰. Under the NHS's advice, toothache belongs with a dentist once it has lasted beyond two days, and whenever it brings swelling, a temperature or pain when you bite¹³. Sensodyne's own FAQ names a cracked tooth and decay among the causes of tooth pain that are not sensitivity.

Should I switch to stannous fluoride instead?

It is a reasonable change to consider, and on current evidence its case is better supported than potassium's. The 2026 network meta-analysis of 93 randomised trials gave stannous fluoride the only high-confidence result for two-week cold-air sensitivity and potassium a low-confidence one²⁰. In an industry-funded trial of 120 adults, paid for by the maker of the stannous fluoride paste it tested, stannous fluoride reduced cold-air sensitivity more than potassium nitrate at week two and over the eight weeks taken together¹⁴. By week eight the gap between those two was no longer statistically clear. S3 does not contain stannous fluoride, and the guide to UK alternatives by active ingredient shows which tubes do.