10% nano-hydroxyapatite: why that concentration keeps appearing in the research.

Ten per cent is not a dose that anybody established. It is the point where three separate things met: the strength at which the best-documented raw material is sold, the concentration two influential trials happened to test, and, from March 2023 to June 2025, the highest concentration of hydroxyapatite (nano) that a European safety committee had assessed for use in toothpaste⁷⁸. None of the three is a finding about how well a toothpaste works, and no published study establishes an optimal concentration. S3 Sensitivity Science™ states 10% nano-hydroxyapatite and 5% biomimetic hydroxyapatite as inclusion levels of the ingredients as supplied, with the mineral content lower.

What was checked13 peer-reviewed studies, two published opinions of the EU Scientific Committee on Consumer Safety on the concentration of hydroxyapatite (nano) in oral products, and product information as published by each brand

Why does ten per cent appear on so many hydroxyapatite toothpastes?

Because three unrelated forces push towards the same figure, and none of them is a measurement of how well the paste works.

The first is supply. Hydroxyapatite for oral care is not shipped as a dry powder that a formulator weighs out; the best-characterised material arrives as a thick white aqueous paste, and the percentage a formulation sheet records is usually the percentage of that paste⁷. The second is habit. A small number of studies used ten per cent, later papers cited them, and brands wrote the figure onto packs because it was the figure in the literature. The third is regulatory, and it is the part almost nobody writes about: for a little over two years, ten per cent was the maximum concentration of hydroxyapatite (nano) that the European Commission's scientific committee had actually looked at and called safe in a toothpaste⁷.

Put those together and the number stops being mysterious. It also stops being a recommendation.

What concentrations have the studies actually used?

Five, ten, fifteen and, in one laboratory gel, twenty and thirty. The table below gathers every place the figure ten comes from, with what each source can and cannot settle.

Read the last column downwards and the shape of the evidence is plain. Every entry is either a trial that used ten per cent for its own reasons, a specification, or a safety assessment. Not one is a study that set out to find the right concentration and found ten.

Has anyone put one strength against another?

Yes, a handful of times, and the answer has almost always been no difference. In an in-situ study in 30 adults wearing appliances for 28 days a phase, five per cent and ten per cent produced no significant difference in percent mineral gain². In 80 participants, ten per cent and fifteen per cent were statistically indistinguishable on tubule occlusion, precipitate area and dye penetration at both seven and 14 days³. In vitro, 2.5% and five per cent behaved the same on 24 extracted teeth⁵, and 20% and 30% behaved the same in a gel on 100 enamel specimens⁶. In the one randomised trial that ran two concentrations, sponsored by the manufacturer of the pastes, ten and fifteen separated at a single comparison out of eight, on the cold stimulus at week six¹.

That is the whole of it, and the sibling page on what percentage a toothpaste needs sets out each comparison in full. What matters here is the negative result behind the number: ten per cent is famous without ever having won a contest.

Does ten per cent mean the mineral, or the paste it came in?

Usually the paste, and the difference is large enough to change what a reader thinks they are buying.

The dossier the European committee worked from describes the manufacturing route in one line: wet chemical precipitation near room temperature, producing a dilute slurry that is then concentrated to a 15.5% paste⁷. The same file records the manufacturer's guidance that the material is generally used at 3–15% in an oral care product, and that at its practical maximum of 90% the finished product would contain 13.95 per cent of the nanomaterial⁷. Those are two statements of one fact: nine parts of the supplied paste in every ten carry just under fourteen parts of mineral in a hundred, because the paste is 15.5% mineral before anybody adds it to anything⁷.

One brand publishes exactly that sum for its own tube. Fygg's page states a nano-hydroxyapatite raw material that is itself 15.5% hydroxyapatite, an addition of 20% of it, and 3.1% per tube as the result. Twenty per cent of 15.5% is 3.1%, and a laboratory paper that put eight marketed hydroxyapatite toothpastes on one bench in 2025, in work funded by a commercial sponsor, lists the same product as 20% of the raw material¹¹. Two documents, two apparently different figures, one formula: the brand is counting mineral and the paper is counting material. Both were read for this page on the tenth of September 2026, and neither is wrong.

Anyone hoping to settle this by measurement will find that harder than it sounds. An analytical paper published in 2026 by chemists who are employees of a toothpaste manufacturer's research centre opens by describing reliable methods for quantifying nano-hydroxyapatite in a finished formulation as limited, and goes on to build one, working indirectly through calcium and phosphorus by plasma spectroscopy rather than weighing the mineral itself¹⁰. And when an independent group did extract and examine the particulate fraction of four marketed hydroxyapatite toothpastes, the particles it found were composed of silicon and oxygen, with calcium and phosphorus present in what the authors call small amounts⁹. That laboratory work tested erosion rather than sensitivity, so it settles nothing about relief, and it is worth knowing anyway: what a hydroxyapatite pack declares and what an assay finds are not the same question. The page on reading a hydroxyapatite label correctly takes the label apart line by line.

What does S3's ten per cent refer to, and why that number?

To the ingredient as supplied. Both of S3's hydroxyapatite figures, the 10% nano form and the 5% biomimetic one, are inclusion levels of the ingredient as it arrives, the mineral inside each is lower, and the brand puts both numbers on the record. That basis was picked to sit where the trials sat: 5% potassium nitrate and a nano-hydroxyapatite solution at the strength the literature had used. The nano-hydroxyapatite in S3 is under 100 nm, rod-shaped and crystalline, while the biomimetic form beside it is around two microns and less crystalline, so the two figures describe two different materials doing two different jobs. The nano-hydroxyapatite S3 uses is tested to the EU committee's guidance for nanomaterials, and that committee has published an opinion on hydroxyapatite (nano) in oral products.

What none of that says is that ten is the right number. The direct comparisons found no advantage for it, this site does not claim one, and no source explains why S3 landed on ten rather than five or fifteen beyond the levels the trials used.

Here is how the figures on the UK shelf compare, grouped by what each one counts. 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.

Three of the five publish a percentage without saying anywhere what it is a percentage of, and the two that do say are the two that disagree about what a percentage should mean. Thirteen further hydroxyapatite toothpastes in this site's UK scan publish no figure at all, and the whole scan sits on the category review of UK sensitivity toothpastes by ingredient.

What did the European safety assessment say, and what changed in 2025?

It said ten, then it said 29.5, and the reason for both numbers is the same: a committee answers the question it is asked⁷⁸.

The Scientific Committee on Consumer Safety gives the European Commission independent advice on cosmetic ingredients and the concentrations at which they may be used. Hydroxyapatite is not restricted under the Cosmetics Regulation, so there is no annex entry setting a level; what exists instead is a chain of opinions, and the committee twice declined to conclude, in October 2015 and December 2021, on the ground that genotoxicity could not be ruled out from the data then available⁸. Industry submitted more evidence in February 2022. In the opinion numbered SCCS/1648/22, adopted at the plenary meeting of 21–22 March 2023, the committee wrote that it "considers hydroxyapatite (nano) safe when used at concentrations up to 10% in toothpaste, and up to 0.465% in mouthwash", and it fenced that conclusion carefully⁷. The evaluation applies only to material "composed of rod-shaped particles of which at least 95.8% (in particle number) have an aspect ratio of less than 3, and the remaining 4.2% have an aspect ratio not exceeding 4.9", which is "not coated or surface modified", and the same page states plainly that the opinion "is not applicable to hydroxyapatite (nano) composed of needle-shaped particles"⁷.

That ten per cent was the level the submission asked about. The notification recorded in the opinion lists the intended use as toothpaste at concentrations up to ten per cent, and the committee assessed it and agreed⁷.

Then a different applicant asked a different question. The opinion numbered SCCS/1677/25, adopted on 26 June 2025, concerns a second material, described in the file as a paste-like aqueous suspension with a solid content of 29.5%, intended for toothpaste at concentrations of up to 29.5%⁸. The committee's answer was that hydroxyapatite (nano) is safe "when used at concentrations up to 29.5% in toothpaste, and up to 10% in mouthwash", again for rod-shaped particles only, this time with at least 87% of them by particle number at an aspect ratio of three or less, the rest not exceeding nine, uncoated, and with a maximum particle length given as 122 plus or minus 43 nm⁸. The ceiling did not move because new evidence showed that more hydroxyapatite does more. It moved because a second applicant submitted a more concentrated material and asked whether it was safe⁸.

None of this is an efficacy finding, and it would be an error to read it as one. A ceiling of 29.5% sits far above the highest concentration of nano-hydroxyapatite ever carried into a study on people, which is the 15% of a four-week randomised trial in 105 adults⁴⁸. A ceiling is a limit on harm, not an instruction about benefit.

Does that ceiling apply to a tube bought in Britain?

This page does not claim to know, and that is an honest answer rather than an evasive one.

Great Britain retained the recast cosmetics regulation after leaving the European Union, and its Article 16 now requires that a cosmetic product containing a nanomaterial be notified to the Secretary of State at least six months before it is placed on the market¹⁶. The scientific advice that would sit behind a British limit comes from the Scientific Advisory Group on Chemical Safety in Consumer Products, commissioned by the Office for Product Safety and Standards, which describes itself as having no regulatory status. In August 2023 that office issued a call for data on nanomaterials in cosmetics, naming seven substances whose safety it wanted evidence on, with hydroxyapatite (nano) among them and a submission deadline of 22 December 2023¹⁵.

So the position is a review in progress rather than a published British ceiling. A search of the government's own site for this page, on the tenth of September 2026, returned that call for data as its only result for hydroxyapatite, and no British opinion on the ingredient¹⁵. The European committee's opinions are advice to the European Commission; they are not British rules, and this page will not turn one into the other.

Does more hydroxyapatite make a better toothpaste?

Nobody has shown that it does, and two of the ingredient's meta-analyses could not have shown it even had they wanted to.

The 2019 meta-analysis that pooled six four-week randomised trials reports a benefit for nano-hydroxyapatite on evaporative and tactile stimuli with every concentration thrown into one pot¹³. The 2023 update, a meta-analysis of 44 clinical trials whose authors include scientists employed by Dr Wolff, a maker of hydroxyapatite toothpastes, did the same across a wider set: relief against placebo and against fluoride pastes, with every level pooled¹⁴. Neither review splits its result by strength, and neither could have: the trials underneath them held the concentration still¹². Behind both sits the same thin base: when a scoping review counted the actives in 368 desensitising toothpaste formulations drawn from 138 randomised trials, hydroxyapatite turned up in nine of them¹². Nine formulations, spread over decades and several different minerals, is not a dataset from which a dose emerges.

Two other variables get lost behind the percentage. Particle size is one: in vitro, on brushed dentine discs, a dentifrice carrying 80 nm hydroxyapatite plugged more tubules than one carrying 300 nm of the same mineral¹⁷, and the page on why particle size decides what hydroxyapatite can do follows that argument. What the mineral is mixed with is the other: on the one bench where eight marketed hydroxyapatite toothpastes were compared in vitro, in work funded by a commercial sponsor, the ranking did not follow the declared percentages, and a product declaring five per cent sat level with one declaring twenty¹¹. Whether any of it helps a person is a separate question again, taken up in does nano-hydroxyapatite toothpaste work for sensitive teeth and, for daily use and dose, in can you use it every day. The Sensitivity Journal's guide to choosing a toothpaste when your teeth are sensitive is the practical version of the same decision.

Frequently asked questions

Is ten per cent the recommended amount of hydroxyapatite in a toothpaste?

No, because nobody has issued a recommendation. There is no dental guideline naming a hydroxyapatite concentration, no regulator has set one as a minimum, and the studies that used ten per cent were comparing it with other ingredients rather than with other strengths of itself. The nearest thing to an official number is a safety ceiling, which works in the opposite direction: it says how much is too much, not how much is enough⁷⁸.

Is S3's ten per cent the same as the ten per cent in the studies?

Not necessarily, and it would be unsafe to assume so. The trials describe their pastes by nano-hydroxyapatite content in their own terms, and their abstracts rarely say whether that figure counts the mineral or the material it arrived in²³. S3's figure is stated as an inclusion level of the ingredient as supplied, with the mineral content lower. Two identical-looking percentages can only be lined up when both sources say what they are counting, and most do not.

Why do some toothpastes say 15% or 20%?

Because those numbers describe different things, and sometimes different materials. Fifteen per cent has its own clinical literature: a double-blind trial in 105 adults tested a 15% paste against a fluoride paste and a placebo⁴. Twenty per cent, on the one brand in this site's scan that publishes the whole sum, has meant twenty parts of a raw material rather than twenty parts of mineral. And a higher figure is not evidence of a stronger product: on the one laboratory bench that ranked eight marketed pastes, funded by a commercial sponsor, the order did not track the declared percentages¹¹.

Is there a legal limit on how much nano-hydroxyapatite a toothpaste can contain?

In the European Union the answer is layered. Hydroxyapatite is not listed in an annex of the Cosmetics Regulation with a restriction, so what governs it is the notification duty for nanomaterials plus the committee's published opinions, which advised a ceiling of ten per cent in toothpaste from March 2023 and 29.5% from June 2025, for rod-shaped, uncoated particles only⁷⁸. For Great Britain, this page states what it can source and no more: nanomaterials must be notified to the Secretary of State six months before sale¹⁶, and the Office for Product Safety and Standards has an open call for data on hydroxyapatite (nano) among six other nanomaterials¹⁵. We could find no published British concentration limit, and we are not going to guess at one.