Definition
Nano-hydroxyapatite (nHAp) refers to hydroxyapatite in nanoscale particle form. Chemically, it is the same calcium phosphate mineral as conventional hydroxyapatite; the difference lies in particle size and the resulting physical properties.
Not every hydroxyapatite is nano-hydroxyapatite
This point is frequently confused, with significant consequences for classification.
The term ‘hydroxyapatite’ describes a material. Whether a substance is regulatorily classified as a nanomaterial additionally depends on particle size, morphology, and other physical properties. The base INCI name ‘Hydroxyapatite’ alone does not establish whether the ingredient is present in nano form; nanomaterials must be specifically identified as such in the ingredient list.
Practical consequence: the restrictions described below apply exclusively to Hydroxyapatite (nano) as defined and specified in Annex III of the Cosmetics Regulation. They do not apply to conventional, non-nanoscale hydroxyapatite. Anyone applying these figures to the entire hydroxyapatite family draws the wrong conclusions.
The nano form can be identified by its labeling: nanomaterials must be indicated in the ingredient list with the suffix ‘(nano)’.
Materials science classification
As particle size decreases, the surface-to-volume ratio increases. A material can therefore behave differently than the same material in larger particle form, for example in adsorption onto surfaces or penetration into structures such as dentinal tubules.
The difference between nano and non-nano is therefore not simply a matter of size. Morphology is also relevant: rod-shaped and needle-shaped particles are assessed differently under the regulation. The length-to-width ratio (aspect ratio) is a key criterion here.
Regulatory status
The relevant regulation is Commission Regulation (EU) 2024/858, which amended Annex III of Cosmetics Regulation (EC) No 1223/2009. Hydroxyapatite (nano) is listed there under entry 372. The provisions have applied to placing on the market since 1 February 2025; since 1 November 2025, non-compliant products may no longer be made available on the Union market.
Under these provisions, Hydroxyapatite (nano) is permitted exclusively:
- in toothpaste, up to a maximum concentration of 10%
- in mouthwash, up to a maximum concentration of 0.465%
- in the form of rod-shaped particles, of which at least 95.8% (by particle count) have an aspect ratio below 3, with the remaining 4.2% not exceeding an aspect ratio of 4.9
- in uncoated and non-surface-modified form
Use is not permitted in products where exposure of the end user's lungs through inhalation could occur, such as sprays. In cosmetic categories outside oral care, the substance is not approved.
Notable is the gap between the two limits: the permitted maximum for mouthwash is roughly twenty-one times lower than for toothpaste. Concentration figures are therefore not meaningful without the corresponding product category.
Current regulatory development
The framework described above is the status current at the time of review. The scientific assessment, however, is continuously updated. As of 11 August 2026, the legally applicable limits remain those in Regulation (EU) 2024/858 unless and until the Cosmetics Regulation is formally amended.
In 2025, the Scientific Committee on Consumer Safety (SCCS) adopted a further opinion on Hydroxyapatite (nano), assessing higher concentrations and different particle specifications. For the specifications it evaluated, the SCCS concluded that nano-hydroxyapatite would be safe up to 29.5% in toothpaste and 10% in mouthwash. An SCCS opinion is a scientific assessment; it is not applicable law. Whether and in what form it is incorporated into the Cosmetics Regulation is decided by the European Commission through its own legislative procedure.
The 2025 SCCS opinion may inform a future amendment of the Cosmetics Regulation. Until such an amendment is formally adopted and becomes applicable, the limits established by Regulation (EU) 2024/858 remain in force. KEERN does not speculate on the procedural status of a possible amendment, as no official confirmation from the Commission is available on this point.
Guideline status
The S3 guideline ‘Caries Prevention in Permanent Teeth’ (AWMF 083-021, Version 2.0, 2025) lists nano-hydroxyapatite among the chemical compounds for which no recommendation can be made within the scope of caries prevention.
This does not mean that no scientific data exist or that an effect is ruled out. It means that the evidence available at the time of assessment did not meet the guideline's criteria for a formal recommendation. For fluoride toothpaste, the same guideline gives a strong recommendation (Grade A).
Regulatory approval and guideline recommendation are two different things. A substance can be legally permitted without a clinical usage recommendation existing for it.
Current research
The same methodological limitation applies to nano-hydroxyapatite as to hydroxyapatite in general: clinical data come from studies of specific product formulations. Transferring study results from one formulation to other products is not valid, even if both contain nHAp.
The clinical evidence to date is based on a smaller number of studies and research groups compared with established fluoride strategies. Interpretation of the results should therefore take into account study design, the formulation studied, endpoints, and reproducibility of the data.
A note on the cited literature: not every publication referencing hydroxyapatite specifically isolates nano-hydroxyapatite as its subject. Some of the broader clinical literature on hydroxyapatite covers a mix of nano and non-nano formulations, or does not consistently distinguish between them. Where a source addresses hydroxyapatite in general rather than nano-hydroxyapatite specifically, it is labeled as such below and should not be read as nano-specific proof.
What the data currently doesn't show
- No basis for the claim that nano-hydroxyapatite is equivalent or superior to fluoride
- No transferability of study results from one formulation to any other product
- No recommendation from the German S3 guideline on caries prevention
- Regulatory approval is not proof of efficacy; it means a substance has been assessed as safe under defined conditions
- No basis for treating all hydroxyapatite-containing products as nano-hydroxyapatite products, or for transferring nano-specific regulatory limits to conventional hydroxyapatite
Key points at a glance
- Not every hydroxyapatite is nano-hydroxyapatite: particle size and morphology are decisive, not the INCI name
- Nanomaterials are marked in the ingredient list with ‘(nano)’
- Under current law: max. 10% in toothpaste, max. 0.465% in mouthwash, a roughly twenty-one-fold difference
- Permitted only as rod-shaped, uncoated particles with a defined aspect ratio
- Not permitted where inhalation exposure is possible, or outside oral care
- An SCCS opinion is a scientific assessment, not applicable law
- The S3 guideline AWMF 083-021 currently makes no usage recommendation
- Regulatory approval and clinical recommendation are two different levels
