Potassium nitrate versus potassium chloride: two potassium salts, two shelves, and no trial that compared them.

Potassium nitrate and potassium chloride are two salts of the same metal, and the potassium is thought to be the working part of both: a review of the potassium literature found that toothpastes built on nitrate, on chloride and on citrate all reported significant reductions in sensitivity¹. No published head-to-head comparison of two potassium salts exists, so nothing on the shelf makes one of them the strong version and the other the substitute. What separates them is what travels with them: in the September 2026 review of UK sensitivity toothpastes, every recorded product whose ingredient list names potassium chloride is a fluoride-free hydroxyapatite paste, and every product naming potassium nitrate carries fluoride. S3 Sensitivity Science™ carries both salts, potassium nitrate at a declared 5% and potassium chloride. If your question is what happens when a potassium salt and hydroxyapatite share a tube, and not which salt it is, that argument sits on the page about potassium nitrate and hydroxyapatite together.

What was checked20 peer-reviewed studies and one journal commentary, the Oral Health Foundation, the NHS, product information as published by each brand

Is the potassium the working part, or the salt it arrives in?

The working model is that potassium ions raise the potassium concentration around the nerve endings inside the dentine and make them slower to fire, and it is a model rather than a demonstration: the review that gathered the potassium trials says plainly that the mechanism has never been confirmed in an intact human tooth¹. The page on how potassium nitrate is thought to calm a sensitive tooth takes that apart properly.

What matters here is the second half of the model. If the potassium ion is the part that acts, the anion it arrives with — nitrate, chloride or citrate — is a passenger, and the review's own evidence is consistent with that: toothpastes built on all three reported reductions, which is difficult to explain if the anion were doing the work¹. That is an argument from a pattern across separate papers, not from an experiment, and the review is narrative rather than pooled, so it can settle nothing.

The anion is not inert inside the tube, though. Potassium chloride is the chloride salt of potassium and not the sodium chloride of the table, and the three salts differ in solubility, in taste and in what else a formula can be built around them. Nobody has published a clinical comparison that varies only the anion and measures what reaches the nerve, so how much difference that makes to a person is unmeasured, in either direction.

What has potassium chloride actually been tested at, and with what result?

Twice, in two very different decades.

In 1994 a three-cell double-blind randomised trial, whose funding is not stated in the record, gave 62 adults a potassium chloride dentifrice, a potassium chloride and sodium monofluorophosphate dentifrice, or a placebo, for eight weeks; both potassium chloride pastes reduced tactile and cold-air sensitivity significantly more than the placebo, reaching significance within four weeks and holding it on every measure at the end³. No percentages or means appear in the abstract, so what it gives is a direction and not a size. The abstract also names the fluoride-containing arm — Sensodyne F, described there as then marketed in the United Kingdom and Germany, again in a trial whose funding is not stated³. At that point, the sensitivity toothpaste most people in this country could name was a potassium chloride product.

In 2017 an examiner-blind randomised trial gave 133 adults either an experimental 3.75% w/w potassium chloride dentifrice or a standard fluoride dentifrice, twice daily for eight weeks, and it was funded by the manufacturer, every author an employee of it⁴. Both pastes improved from baseline at every visit on every measure. In that industry-funded trial the potassium chloride paste scored lower on the examiner-rated air-blast scale at two, four and eight weeks, the fluoride reference took more probe pressure at eight weeks, and the patients' own hundred-millimetre rating separated the groups at no point⁴. The endpoints disagree, and the paper says so.

The work was noticed outside the sponsor. A critical summary in a general dental journal appraised it the following year and hedged its own title, saying that a potassium chloride dentifrice may be more effective than a standard fluoride dentifrice⁵. That summary is a commentary. It carries no participants and no data of its own, and it appraises someone else's work rather than adding to it.

Two trials, one of them thirty years old and one of them run by the company that made the paste, is not much of an evidence base. It is, however, more than most consumer pages about potassium chloride admit exists.

Has anyone put the two salts against each other?

No. Four PubMed searches run for this page in September 2026 came back with nothing:

The planner's own search on the same day, restricted to chloride and citrate dentifrices in dentine hypersensitivity, returned eleven records and no salt-against-salt comparison either. The raw responses are kept with this page's research files.

The closest published work is a pair of eight-week comparisons published in 2001. The second of them, run by a manufacturer-affiliated team, gave 105 adults either a new dentifrice containing potassium nitrate, stannous fluoride and sodium fluoride or a marketed potassium chloride, triclosan and sodium fluoride paste, and at four and eight weeks the new dentifrice group tolerated 40.5 g and 43.7 g of probe pressure against 27.8 g and 33.2 g, with air-blast scores of 1.10 and 0.67 against 1.90 and 1.57, all at p<0.001⁶.

Read the arms rather than the headline. The test paste changes the potassium salt and adds stannous fluoride, which the newest network meta-analysis rates as the desensitising active with the highest-confidence evidence in the whole class². When two things change at once and one of them is the best-evidenced ingredient in the category, the result cannot be pinned on the potassium. That work shows a three-active paste separating from a single-salt paste. It shows nothing about nitrate against chloride.

There is a second reason the older work cannot settle it, and it applies to the potassium chloride papers as much as to anyone else's. In a placebo-controlled double-blind randomised trial in 90 adults over eight weeks, whose funding is not stated in the record, a rinse with the actives taken out of it improved sensitivity by 30% to 40% on its own, and the authors put that figure forward precisely because a formulation with no therapeutic action cannot have had one⁷. "Both arms improved significantly from baseline" is the least informative sentence in this literature.

Where does potassium citrate fit?

Citrate is the third salt, and it has the untidiest record of the three.

One paper does set two potassium salts against each other, and it is the one nobody quotes: an eight-week double-blind randomised trial in 80 adults, whose funding is not stated in the record, put a 5.5% potassium citrate and sodium monofluorophosphate dentifrice against a marketed 3.75% potassium chloride, sodium fluoride and triclosan dentifrice and found no statistically significant difference on tactile or air-blast sensitivity at four weeks or at eight⁸. It carried no placebo arm, and the potassium salt and the fluoride salt were varied together, so nothing can be pinned on either. Citrate against chloride, then, has been looked at once, inconclusively. Nitrate against either has not been looked at.

The cleanest potassium comparison in this whole set is also a citrate one. A double-blind randomised trial in 67 adults gave both arms the same 0.76% sodium monofluorophosphate paste and added 5.53% potassium citrate to one of them, so only the potassium differed; the citrate arm's cold-air pain score fell further by four weeks, 1.12 against 0.32, and the patients' own rating fell further by eight, 1.59 against 0.24⁹. Fifty-seven of the sixty-seven randomised were analysed, which is why this belongs in the record as a single result and not as a headline. A double-blind randomised trial in 56 completers compared a reformulated potassium citrate paste with the original and found both improved with little between them, and no placebo arm to size either against¹⁰.

Then there is the gap in the guidance. The Oral Health Foundation tells people to use toothpastes containing potassium citrate, potassium nitrate or stannous fluoride¹¹. Potassium chloride is not on that list — and the potassium chloride paste tested in 1994 was on sale here at the time. The guidance follows the salts that stayed inside the fluoride category, which is the same pattern the shelf shows.

Why does the shelf split the two salts the way it does?

Here is the whole potassium half of the September 2026 UK category review, based on what each brand states about its own formula.

This page compares ingredients and stated actions only, not clinical performance. Prices and formulations may change; always check the pack. One further tablet product naming potassium citrate sits in the register as pending because its full ingredient list is not published, and it is left out of the table for that reason.

The split is complete, and it runs both ways. Twelve of the eighteen listings name potassium nitrate and every one of them carries fluoride; of those twelve, only S3 also carries hydroxyapatite. Five name potassium chloride, and the four that are not S3 carry no fluoride and every one of them carries hydroxyapatite. Two name citrate, both alongside fluoride, one of them with hydroxyapatite as well. S3 is the single row in the scan whose ingredient list names two potassium salts. Three listings in the whole potassium half state how much potassium salt is in the tube; the rest name the ingredient and stop.

Why the shelf sorts itself this way is not something the labels tell you, and the honest version is an inference from ingredient lists rather than a fact about anyone's reasoning. Five per cent potassium nitrate is the concentration that carries a published toothpaste literature behind it, and it sits comfortably inside a conventional fluoride paste. The hydroxyapatite brands are formulating outside that convention to begin with, and they reach for a different potassium salt. That is what the lists show. Why each company chose what it chose is not published, and this page does not know it.

What does the whole trial record for the three salts look like?

Every toothpaste trial of the three salts held in this project's study library, with the funding as each record states it. Where a cell says the funding is not stated, that is the record's silence and not a clean bill of health.

The syntheses do not settle it either, because most of them do not keep the salts apart. The 2020 network meta-analysis of 125 randomised trials carries a node called simply "potassium"¹⁹. The 2015 meta-analysis pools eight potassium trials into one estimate²⁰. The 2026 network meta-analysis carries "potassium with or without fluoride", resting on one contributing study at low confidence². A 2023 systematic review and meta-analysis of potassium-salt mouthwashes was written at the level of the class rather than the individual compound²¹. The one synthesis that names a salt is the 2006 Cochrane review, which pooled six potassium nitrate toothpaste trials, found significant effects on air-blast and tactile measures at six to eight weeks, found nothing on what patients themselves reported, and concluded that there is no clear evidence to support potassium toothpastes²². The page on why five per cent is the number the trials used sets out the dose argument.

Why does S3 carry both potassium salts?

Because the formula was built that way, and the register says what the second salt is intended to do: potassium chloride is a second potassium source in S3's formula, reinforcing the nerve-calming action of the potassium nitrate. Its basis is the ingredient list and the product page, and the ingredient list is where it stops. The nitrate is declared at 5%, the concentration the published toothpaste trials used; the chloride level is not declared, and no potassium chloride product in the category review declares one either.

Now the part that costs something. Nobody has compared potassium nitrate with potassium chloride in the same trial, and nobody has tested the two together, which is what S3 contains — so the second salt in S3's list is a formulation choice, not a measured advantage. There is no two-salt paste in the literature to point at, no arm in anyone's work that isolates the second salt, and no figure that says two potassium sources relieve more than one. Saying otherwise would need an experiment that does not exist.

What can be said is narrower and checkable. S3's potassium salts sit in a paste that also carries hydroxyapatite and full adult-strength fluoride, which is the combination the category review recorded in one product, and you can check that against the category review of UK sensitivity toothpastes by ingredient yourself. That is a fact about ingredient lists. It is not a claim about relief.

What should you actually compare when you read two labels?

Three things, and the potassium salt is not one of them.

Fluoride, or no fluoride. This is the real difference between the two shelves. Every fluoride-free hydroxyapatite paste in the table above drops decay protection to gain whatever its brand states it gains; every potassium nitrate paste keeps it. The Journal's article on how sensitive toothpastes work sets out what each active is for.

An occluder, or none. Potassium of any salt acts on the nerve and does not block the tubule, while hydroxyapatite, stannous fluoride, arginine and bioactive glass work on the tubule. The Journal's piece on the two causes of sensitive teeth explains why a tooth usually has both problems at once.

A declared level, or a silent one. A paste that prints its potassium concentration can be checked against the papers; a paste that prints only the ingredient name cannot. That is a bigger difference than nitrate against chloride, and it is the one the shelf mostly refuses to answer.

And a fourth thing that is not on any label. The Oral Health Foundation says a sensitivity toothpaste has to be kept up if its effect is to be maintained, and that pain in a single tooth, pain that arrives out of nowhere, or sensitivity that runs on past a few weeks belongs in a surgery rather than in a shopping decision¹¹. The NHS puts a shorter clock on pain that will not settle: toothache lasting more than two days, or that painkillers do not touch, is a reason to book a dentist rather than change toothpaste²³. No potassium salt is an answer to either of those.

Frequently asked questions

Is potassium chloride as good as potassium nitrate?

Nobody has measured that. No published head-to-head comparison of the two salts exists, and the searches that would have found one come back empty. Each has been put against a placebo or a fluoride paste on its own, decades apart, in different designs and with different sponsors, and comparing across separate papers like that is not evidence of a ranking.

Why do hydroxyapatite toothpastes use potassium chloride?

The published record does not say, and any answer that claims to know is guessing. What the labels show is that in the September 2026 UK category review the potassium chloride products are all fluoride-free hydroxyapatite pastes and the potassium nitrate products all carry fluoride. Five per cent potassium nitrate is the established concentration inside the conventional fluoride category, and brands formulating outside that category are not bound to it — but that is an inference from ingredient lists, not something any brand has published about its reasoning.

Does having two potassium salts make S3 stronger?

No one has measured that either, and this page will not say it does. Potassium chloride is described in S3's register as a second potassium source reinforcing the action of the potassium nitrate, which is a statement about what the formula contains and what it is intended to do. Nobody has put a potassium nitrate and potassium chloride combination against either salt on its own, so there is no figure behind "two is more".

Is potassium chloride just salt?

It is a salt in the chemical sense — the chloride salt of potassium — but it is not the sodium chloride you put on food, and it is not there for flavour. In toothpaste it is a potassium source, and potassium is the ion the whole desensitising model is built on. It has been through randomised trials of its own, one in 1994 whose funding is not stated in the record and one in 2017 funded by the manufacturer³⁴.

Which potassium salt does the Oral Health Foundation name?

Two of the three. Its sensitive teeth guidance tells people to look for potassium citrate, potassium nitrate or stannous fluoride¹¹. Potassium chloride is absent from that list, which is a real gap: the potassium chloride paste tested in 1994 was on sale in this country at the time.