Last checked: October 2026. Written by Clockwork, which makes a nano-hydroxyapatite toothpaste. We have tried to write the page we would want to read if we didn't.
Nano-hydroxyapatite (nHAp) is a lab-made version of the mineral your tooth enamel is made of. In a toothpaste, its tiny particles settle on the enamel surface and help remineralise it. In the EU it is assessed as safe in toothpaste up to 10%, but only if the particles are rod-shaped and uncoated. In clinical trials, hydroxyapatite toothpastes have performed about as well as fluoride toothpastes at preventing new tooth decay. They have not been shown to be better. Those trials tested specific products, not the ingredient in general.
Every day, acids from food, drink and plaque bacteria pull minerals out of the enamel surface (demineralisation). Saliva puts some back (remineralisation). A nano-hydroxyapatite toothpaste adds the same mineral the enamel is made of. In laboratory studies, the particles stick to the enamel surface and fill microscopic gaps. That is the mechanism behind the claim "helps remineralise enamel".
Not all nano-hydroxyapatite is the same material. The EU's Scientific Committee on Consumer Safety (SCCS) reviewed it in 2023 (opinion SCCS/1648/22). Its conclusion only covers particles that meet strict conditions:
| Condition in the SCCS opinion | What it means |
|---|---|
| Rod-shaped particles | At least 95.8% of particles have an aspect ratio (length ÷ width) below 3, and the rest stay below 4.9 |
| Not coated or surface-modified | Plain hydroxyapatite, nothing added to the particle surface |
| Up to 10% in toothpaste | Up to 0.465% in mouthwash |
| Needle-shaped particles | Not covered by the opinion |
| Sprays or anything that could be inhaled | Not covered |
The EU wrote these conditions into law in 2024 (Commission Regulation (EU) 2024/858, which added hydroxyapatite (nano) to Annex III of the Cosmetics Regulation). The opinion is a safety assessment of the ingredient under those conditions. It does not say how well any toothpaste works. Why the source of nano-hydroxyapatite comes before the percentage →
| Study | Who and what | Result | Worth knowing |
|---|---|---|---|
| Paszynska et al., 2023 (Frontiers in Public Health) | 194 adults, 18 months. 10% hydroxyapatite toothpaste (fluoride-free) vs 1,450 ppm fluoride toothpaste | 89.3% vs 87.4% had no increase in decayed, missing or filled tooth surfaces. Hydroxyapatite was "non-inferior": not worse within the margin the trial set | One specific product. Funded by its manufacturer. The paper does not say whether the hydroxyapatite was nano or micro |
| Paszynska et al., 2021 (Scientific Reports) | 207 young children, 1 year. 10% microcrystalline hydroxyapatite vs 500 ppm fluoride toothpaste | New decay in 72.7% vs 74.2%. Non-inferior | Micro, not nano. Compared with a low-fluoride children's paste |
| Pawinska et al., 2024 (Journal of Dentistry), systematic review and meta-analysis | 5 clinical and 8 in-situ trials | Concludes hydroxyapatite is effective against decay in the absence of fluoride | Draws heavily on the same research group's trials; some authors work for a toothpaste maker |
| Limeback et al., 2023 (Biomimetics), systematic review and meta-analysis | Trials of hydroxyapatite for sensitive teeth | Sensitivity fell 39.5% more than with placebo, and 23% more than with fluoride | No significant difference from other desensitising ingredients. Products varied between trials |
The honest summary: the evidence for hydroxyapatite toothpaste is real, growing and mostly from one research network. Every caries trial so far shows "as good as" fluoride, not "better than". None of these trials tested Clockwork. There is no completed clinical trial on our own finished formula yet, and we won't call it clinically proven until there is.
Fluoride is the most-studied ingredient in oral care, and it works. Hydroxyapatite is an alternative with good early evidence. People choose it because they want a fluoride-free paste, because of what a young child swallows, or because they prefer an ingredient that matches what enamel is made of. If you or your child has active decay or a high risk of it, ask your dentist which suits you. This page isn't medical advice.
Many nHAp toothpastes, ours included, also contain xylitol. A 2015 Cochrane review found low-certainty evidence that fluoride toothpaste with 10% xylitol may reduce decay in children's permanent teeth by about 13% compared with fluoride toothpaste alone. There isn't good evidence that xylitol on its own prevents cavities. We use it as a sweetener that mouth bacteria can't ferment into acid, not as a treatment.
"Contains hydroxyapatite" tells you as much as "contains protein" on a protein bar: true, and useless without the amount and the source. Before you buy any nHAp toothpaste, ours included, look for six things: shape, size, maker, the percentage and what it is a percentage of, a registration or safety review, and the full ingredient list.
How to choose an nHAp toothpaste: 6 questions →
What nHAp toothpastes sold in India publish: a specification table →
This is what we publish for Clockwork Daily, so you can hold us to the same questions:
No. Some brands state the percentage of nano-hydroxyapatite itself. Others state the percentage of a named ingredient that contains it. Clockwork Daily is the second kind: 10% nanoXIM·CarePaste, a named ingredient whose specification you can look up. Whichever brand you buy, ask what the number is a percentage of.
It is the same mineral at a smaller particle size, under 100 nm. Some trials used larger "micro" particles. Labels don't always say which.
The children's trial above used a micro-hydroxyapatite paste. Check the age guidance on the pack, and ask your child's dentist if your child has decay or a high risk of it.
Laboratory studies have tested nHAp toothpaste around orthodontic brackets, but clinical evidence is limited. Ask your orthodontist.
Ask for the six things above. A brand that knows its mineral's shape, size, maker and registration can tell you. If a brand won't print it, ask why.