Nano-hydroxyapatite paste versus suspension: reading the label correctly.

A hydroxyapatite percentage on a toothpaste can mean the mineral by weight in the finished paste, or the water-based paste of mineral the maker stirred in, and on most tubes it means nothing at all, because no rule obliges a cosmetic label to carry a concentration. What the rules do oblige is the bracket: under the cosmetics regulation as it applies in Great Britain, an ingredient present as a nanomaterial must be listed with "nano" in brackets after its name, so the bracket is a legal declaration and not a marketing word¹. Of the 17 hydroxyapatite toothpastes read for this site's UK scan in September 2026, four state a figure anywhere on the page and six carry that bracket; S3 Sensitivity Science™ is in both groups, giving 10% nano-hydroxyapatite and 5% biomimetic hydroxyapatite as inclusion levels of the ingredients as supplied.

What was checked6 peer-reviewed studies, the cosmetics regulation as it applies in Great Britain, and product information as published by each brand

What does a hydroxyapatite percentage on a toothpaste actually refer to?

To one of three things, and the label almost never says which. Nano-hydroxyapatite is made in water and sold to formulators in water, as a paste or a suspension, so a maker who buys a hundred grams of the raw material is not buying a hundred grams of mineral. The two words on the supplier's drum describe one material at two thicknesses, and neither of them tells you a concentration; that job belongs to the figure printed next to them, if there is one. One brand prints the whole sum on its own page, which makes it the clearest teaching example on the shelf. Fygg says its nano-hydroxyapatite raw material is itself 15.5% hydroxyapatite, that it adds twenty parts of that material in a hundred, and that the result is "3.1% per tube". Twenty parts of a material that is 15.5% mineral leaves a little over three parts of mineral, so both figures are true and they describe one tube.

Set that beside Truthpaste, which states "Hydroxyapatite content: 5% / 50,000 ppm". Five per cent by weight is fifty thousand parts per million, so the two halves of that figure agree with each other, which is what a content figure looks like when it is meant as one. So one tube says twenty and one says five, and the tube that says five holds the larger amount of mineral. Nothing on the front of either pack tells you that.

What does S3's 10% actually mean?

It means ten parts of supplied nano-hydroxyapatite in a hundred, not ten parts of mineral. S3 states 10% nano-hydroxyapatite and 5% biomimetic hydroxyapatite as inclusion levels of the ingredients as supplied, and says the active hydroxyapatite content is lower than either figure. The two are different materials doing different jobs, and their sizes are the reason: the nano form is under 100 nm, rod-shaped and crystalline; the biomimetic form is around two microns and less crystalline. One is small enough to enter a dentine tubule, the other is not, and the page on particle size takes that argument apart.

There is a plain consequence for anyone comparing tubes, and it does not flatter us. A shopper who reads ten per cent on one pack and twenty on another is usually not comparing the same quantity, and the direction of the error is not fixed: the higher figure can be the smaller amount of mineral, or the larger, depending on what each brand counted. Where that ten per cent came from in the first place — a supplier's standard strength, two influential trials, and a safety ceiling that has since moved — is the subject of the page on why ten per cent keeps appearing.

What do the labels on the UK shelf say?

Mostly nothing about quantity, and rather more than you would expect about form. The table below is every product in this site's UK category scan whose recorded ingredient list contains hydroxyapatite in any form, with the entry copied exactly as it appears on the label. 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 counts, and the arithmetic behind them. Filtering the category-review file for rows whose status is `recorded` and whose recorded ingredient list contains the string "hydroxyapatite" returns 17 products out of the 49 in the scan. Six of the 17 carry the bracketed "(nano)" form in that list — Hismile, S3, SURI, Nura, Apagard and Boka — and Davids makes seven that name the nano form somewhere in the entry, in its own wording. Four of the 17 declare a hydroxyapatite concentration anywhere on the page that was read: Nura, RiseWell, S3 and Truthpaste. The eighteenth row, Fygg, is printed below the others and counted in none of the three, because the brand publishes no full ingredient list and the row is marked pending for that reason. The whole scan, including every sensitivity toothpaste in it with no hydroxyapatite at all, is in the category review of UK sensitivity toothpastes by ingredient.

Four labels out of 17 give a figure. For the other thirteen there is no way for a shopper — or for this page — to say how much hydroxyapatite is in the tube, and some of them cost more per tube than the ones that do. That is a statement about labelling practice in a category and not about any brand's honesty: nothing requires a hydroxyapatite level on a cosmetic label, and a brand that prints none is complying with the same rule as a brand that prints one.

Where each row was read matters too. Boka, Davids and Fygg were read on their own American sites with dollar prices, and no UK retailer listing was found for them in this scan; ApaCare was read on the brand's European shop in euros; RiseWell's own site quotes sterling but did not appear on a UK retailer's shelf in the scan. Prices are as shown on the day, and the rows printed here were checked again against their saved pages on the tenth of September 2026: every hydroxyapatite entry matched, and the pages re-fetched today were unchanged apart from a review counter on the SURI listing.

† Two prices could not be re-checked. Truthpaste's saved page renders its price after the page loads, so the capture holds none, and the Spotlight figure was recorded from a Boots listing that is not among the saved files for that row — the brand's own page saved the same day offers a three-tube bundle at £23.85 instead. Both figures are printed as recorded on the ninth of September, neither was re-read, and that is the sort of thing a table ought to say rather than smooth over.

The shelf as a whole, arranged by active ingredient instead of by brand, is walked through on the Boots and Superdrug shelf page.

Why does "(nano)" appear in some ingredient lists and not others?

Because it is a legal declaration attached to a physical fact, not a claim a brand chooses to make. Article 19 of the cosmetics regulation as it applies in Great Britain says that "all ingredients present in the form of nanomaterials shall be clearly indicated in the list of ingredients" and that "the names of such ingredients shall be followed by the word 'nano' in brackets"¹. The same regulation defines a nanomaterial as an insoluble or biopersistent, intentionally manufactured material with one or more external dimensions, or an internal structure, on the scale from 1 to 100 nm². So the bracket is a statement about particle size, made under a rule, and a tube whose front says nano-hydroxyapatite while its ingredient list says plain "Hydroxyapatite" is showing you two things that do not obviously match. This page reports what each label shows and what the rule requires, and stops there.

The same article carries a second rule that a careful reader can use. Ingredients are listed in descending order of weight at the time they are added to the product, and anything under one per cent may be listed in any order after the rest¹. Two useful things follow. Position in the list ranks the ingredient as it went in, the supplied paste and its water included, not the mineral inside it. And once an ingredient sits in the tail of the list, its order says nothing at all, so a hydroxyapatite entry near the end of a long list cannot be read as a quantity.

Micro is the other word on the shelf, and it is not the same declaration. Biorepair writes "Zinc Hydroxyapatite (microRepair)", RiseWell gives its figure of ten per cent for micro-hydroxyapatite, and Nura lists both forms, "Hydroxyapatite (Nano)" and "Hydroxyapatite (Biomimetic Micro)", in one ingredient list. A micro particle is above the nanomaterial threshold, so no bracket is required and none appears. Neither word is a quality grade. Shape is part of the specification too, which is why the Davids entry, "Nano Hydroxyapatite (rod shaped)", carries more information than it looks: a laboratory characterisation of a commercially available oral-care nano-hydroxyapatite, published by a group including scientists employed by the company that manufactures it, found rod-like particles with the chemical and phase composition expected of hydroxyapatite⁷.

Does a higher percentage mean a better toothpaste?

No trial has shown that it does, and the tested range is five to fifteen per cent with nothing in it that separates one figure from another. In vitro, on 160 bovine enamel blocks over 14 days of pH cycling, an industry-funded laboratory comparison put eight marketed products on one bench, and the results did not line up in the order of the declared percentages: a product declaring five per cent and one declaring fifteen sat level with the one declaring twenty, and the two fluoride pastes were indistinguishable from all of them⁵. Those eight products differ in particle type, base, abrasive and fluoride as well as in percentage, so this is not a dose comparison and nobody should read it as one. The evidence on concentration is weighed properly on the page on what percentage a toothpaste needs, and this page will not re-argue it.

What else is in the tube?

More silica than hydroxyapatite, in most cases, and it is worth knowing before the percentage on the front takes over. When an independent group extracted and examined the particulate fraction of marketed hydroxyapatite oral-care products in vitro in 2025, every toothpaste contained amorphous particles whose elemental analysis identified silicon and oxygen, with calcium and phosphorus present only in small amounts on the particles of the hydroxyapatite pastes⁴. That was an erosion and abrasion study, so it says nothing about sensitivity and nothing about any named product, and the erosion half of it is dealt with on the remineralisation page. The finding that belongs here is narrower, and it applies to the whole category, S3 included: counted as particles rather than as declared percentages, a hydroxyapatite toothpaste is mostly abrasive⁴.

The abrasive and the fluoride salt vary as much as the active does. A systematic review of 138 randomised trials of desensitising toothpaste, which counted formulations rather than pooling their results, catalogued 368 of them and recorded silica-based abrasives in 84 and calcium-based abrasives in 64; sodium monofluorophosphate appeared in 105 and sodium fluoride in 82⁶. Four of the 17 hydroxyapatite tubes on this shelf carry a fluoride salt at all — Spotlight, Georganics, ApaCare and S3 — and no fluoride appears in the ingredient list read for any of the other thirteen. S3 is one of those four, and the salt it uses is sodium monofluorophosphate at 1450 ppm, full adult strength.

Then there is the base. Two of the 17 list no Aqua at all. RiseWell is recorded as anhydrous; Truthpaste is built on aloe leaf juice, which carries water without the ingredient list naming it as Aqua, so the row records none. That matters, because a base without water changes which actives a formula can carry, and a water-based hydroxyapatite paste behaves differently in one.

Can anyone check a declared percentage?

Not from outside the factory, and not easily from inside it either. A laboratory paper published in 2026 by chemists employed at a toothpaste manufacturer's research centre opens by calling reliable methods for quantifying nano-hydroxyapatite in a finished formulation limited, and then builds one: the mineral is not weighed directly but inferred from calcium and phosphorus measured by plasma spectroscopy and converted stoichiometrically to a hydroxyapatite-equivalent figure³. Nothing about that is available to a shopper in a chemist's shop. It also means a declared figure is a statement from the maker, taken in good faith, and not something a third party routinely audits — which is a reason to prefer a label that says what it is counting over one that simply prints a bigger number.

What should you check on a tube before you buy it?

Five things, in the order they appear on the pack.

• Turn the tube over and find the ingredient list, not the claim on the front. The list is the part governed by a rule.
• Look for a bracket after "Hydroxyapatite". "(nano)" is a declared nanomaterial; "(microRepair)" or "micro" is the larger form; nothing in brackets means the brand has not declared a nano form in that entry.
• Look for a concentration anywhere on the pack or the product page, and expect not to find one. Thirteen of the 17 tubes in this scan give none.
• If there is a figure, ask what it counts. A brand that says "content", or gives the same figure in two different units, is counting mineral. A brand that says how much of a named raw material it added is counting the material.
• Check whether fluoride is still in there, and at what strength, because most hydroxyapatite toothpastes have taken it out. The page on toothpastes that keep both sets out what a formula holding fluoride and hydroxyapatite together is for.

Two habits are worth adding. A tube that declares nothing has broken no rule; it is simply unreadable, and a shopper is entitled to prefer the readable one. And a percentage is not a particle size: in vitro, a dentifrice carrying 80 nm hydroxyapatite plugged more dentine tubules on extracted-tooth discs than one carrying 300 nm of the same mineral, and no percentage on any of these labels tells you which size is in the tube⁸. The Sensitivity Journal's guide to choosing a toothpaste when your teeth are sensitive is the version of this decision that starts from the symptom instead of the label.

Frequently asked questions

Does S3 contain 10% hydroxyapatite, or 10% of the ingredient as supplied?

Not as mineral. The 10% is the inclusion level of the nano-hydroxyapatite as it was supplied, which is a water-based paste, and the same is true of the 5% biomimetic figure; the active hydroxyapatite content in the finished tube is lower than either. That is the honest answer to the question as it is usually asked, and it is the reason the two figures are stated on the inclusion basis rather than as a single headline number.

Is 10% hydroxyapatite better than 5%?

Nobody has shown that it is. The concentrations tested in people run from five to fifteen per cent, and no trial inside that range has established that one figure does more than another; the studies are set out on the page on what percentage a toothpaste needs. Until two tubes state what their percentages count, the numbers on them are not on the same scale anyway.

What is the difference between nano- and micro-hydroxyapatite on a label?

Size, and whether the labelling rule applies. A nanomaterial is defined as having a dimension or internal structure on the scale from 1 to 100 nm, and an ingredient present in that form must be followed by "(nano)" in the ingredient list²¹. Micro particles are larger, so no bracket is required and none appears; "microRepair" and "micro-hydroxyapatite" are the brands' own names for that larger form. Neither word grades quality, and one tube can carry both forms.

Why do some brands not say how much hydroxyapatite is in the tube?

Because no rule asks them to. Cosmetic labelling requires the ingredients in descending order of weight as added, and the nano declaration where it applies, but not a concentration for an active¹. Thirteen of the 17 hydroxyapatite tubes in this scan give no figure, and that is a gap in what a buyer can know rather than evidence of anything about the products.

Does "(nano)" on an ingredient list mean the product is unsafe?

No. The bracket is a size declaration, and its presence tells you the brand has identified a nanomaterial and labelled it as the rule requires. What the ingredient is assessed for, and at what levels, is a separate question dealt with on the page on daily use and safety.