Hydroxyapatite or nano-hydroxyapatite? What does this mean on the ingredient list and does "nano" make a difference?

Hydroxyapatite has become a hit in toothpastes, so it now appears on most "fluoride-free" tubes. However, on some it is listed as "Hydroxyapatite", while on others as "Hydroxyapatite (nano)". Customers ask us if they are the same thing. The short answer: it is the same mineral with a different particle size, and in the European Union, those parentheses are not just for decoration.

The same mineral, different scale

Hydroxyapatite is a calcium phosphate that makes up about 97% of tooth enamel and about 70% of dentin. In toothpaste, it has one job: to provide enamel with its own building blocks so that micro-defects on the surface can be filled and exposed dentinal tubules closed. We write about how this works in our article on hydroxyapatite toothpastes.

The difference between the forms is the particle size. "Nano" refers to particles on the scale of several dozen nanometers, comparable to natural enamel crystals. Micro particles are hundreds of times larger. Intuition suggests that smaller particles penetrate micro-defects and tubules more easily, and most of the clinical studies cited by the industry were conducted using the nano form.

Why parentheses are mandatory in the EU

Cosmetics Regulation 1223/2009 requires that every ingredient in the form of a nanomaterial be marked in the INCI list with the word "(nano)" after its name. A manufacturer using nano-hydroxyapatite must indicate it. The conclusion is simple: if you see just "Hydroxyapatite" on a European label, without parentheses, then according to the manufacturer's declaration, it is a non-nano form.

The second thing worth knowing: nano-hydroxyapatite has undergone a safety assessment in the EU. In its 2023 opinion, the SCCS scientific committee deemed it safe in toothpastes at concentrations of up to 29.5%, provided the particles have a specific shape (rod-shaped, not needle-shaped) and are not coated. This is important because for years there was concern that "nano" in cosmetics was an unknown variable. In the case of hydroxyapatite, that is no longer the case.

What the studies say

The most frequently cited papers on remineralization and hypersensitivity concern nano-hydroxyapatite, usually in concentrations of 10–15%. In an 18-month randomized controlled trial on adults, toothpaste with 10% hydroxyapatite performed no worse than fluoride toothpaste in preventing cavities. Meta-analyses concerning hypersensitivity are also based primarily on the nano form.

There is less evidence for the micro form, which does not mean it is ineffective: in several studies, micro-hydroxyapatite also supported remineralization. To be fair: if you want to buy a toothpaste "based on evidence," buy nano at a concentration stated by the manufacturer. If hydroxyapatite is an added benefit for you alongside other reasons for choosing a product (taste, lack of SLS, brand), the form is less important. More on concentrations in our article how much hydroxyapatite a toothpaste needs.

How to read it in the INCI list

Three things to check on the tube:

• Parentheses. "Hydroxyapatite (nano)" is the nano form; "Hydroxyapatite" alone is non-nano (in the EU).
• Position on the list. Ingredients are in descending order. Hydroxyapatite in the 3rd to 6th position is usually a meaningful concentration; at the end of the list, it is a trace additive.
• Declared percentage. If the manufacturer provides a number (10%, 15%), that is a good sign. If not, do not guess and do not trust stores that guess for them.

How it looks in our selection

We provide what the manufacturers declare, without adding our own interpretation:

• PrevDent nHAp: nano, 15%, plus potassium nitrate for hypersensitivity.
• Ollie Clean Mint and Strong Mint: nano, 10%, short ingredient list.
• BOKA (all variants, including Kids): nano; the manufacturer does not disclose the concentration, so we do not list it.
• Davids Hydroxi: nano, in toothpastes with a very short, plant-based composition; without a declared concentration.
• LEBON and Laro: INCI lists only "Hydroxyapatite", meaning according to the label it is a non-nano form, without a declared concentration. In both cases, hydroxyapatite is one of several ideas for the toothpaste, not the primary one.

You can find the full list with filters in our hydroxyapatite toothpaste collection.

Frequently asked questions

Is nano-hydroxyapatite safe if swallowed?

The SCCS also evaluated safety regarding the swallowing of toothpaste and deemed the nano form safe in pastes up to 29.5%. That is still no reason to swallow the toothpaste: for children, use a pea-sized amount and supervise them.

Does "nano" work faster?

In studies on hypersensitivity, the effect of the nano form is usually visible after 2–4 weeks. For the micro form, the data is more modest, so we do not compare speed; we compare the amount of evidence.

Does hydroxyapatite replace fluoride?

This is a separate topic, with studies on both sides. We wrote a separate article about it; in short: nano-hydroxyapatite is widely studied for remineralization and provides a fluoride-free alternative, while fluoride remains the standard in dental recommendations.

Sources: Regulation (EC) No 1223/2009, Art. 19(1)(g) (labeling of nanomaterials in INCI); SCCS, "Opinion on Hydroxyapatite (nano)", SCCS/1648/22, final version 2023; Paszynska E. et al., Frontiers in Public Health 2023; Limeback H., Enax J., Meyer F., "Biomimetic hydroxyapatite and caries prevention: a systematic review and meta-analysis", Canadian Journal of Dental Hygiene 2021; INCI lists from manufacturers (boka.com, olliesmile.com, davids-usa.com, prevdent.lv, larolondon.com, LEBON distributor).