Non-Nano vs Nano Hydroxyapatite Toothpaste: Why the Particle Size Actually Matters

Hydroxyapatite toothpaste is becoming a more popular alternatives to fluoride, and for good reason. It's the same mineral that makes up the bulk of your tooth enamel, and there's solid research showing it can remineralise teeth and reduce sensitivity. But there's a detail that most people miss when they switch: not all hydroxyapatite is the same. The particle size matters quite a lot, and the difference between nano and non-nano (micro) hydroxyapatite has real implications for safety.

What Is Hydroxyapatite and How Does It Work?

Hydroxyapatite (HA) is a calcium phosphate mineral and the primary structural component of tooth enamel and dentine. Around 97% of enamel by weight is hydroxyapatite. When you brush with a toothpaste containing it, the particles fill in microscopic surface defects, integrate into partially demineralised enamel, and help restore the mineral structure that acid erosion and bacteria wear away over time.

A 2019 review published in the British Dental Journal found hydroxyapatite toothpaste to be comparable to low-concentration fluoride toothpaste for preventing cavities in children, and a number of clinical trials in adults have confirmed its remineralising effects.

A 2023 systematic review and meta-analysis confirmed that hydroxyapatite is effective as an anti-caries active ingredient even in the absence of fluoride.

What people may also not be aware of is that it has been used routinely in Japanese oral care for decades, and we're only just catching on now.

The question isn't really whether hydroxyapatite works. It does. The question is whether the version you're using is safe.

Nano vs Non-Nano: What's the Difference?

Nano hydroxyapatite has particles smaller than 100 nanometres. Non-nano (also called micro or microcrystalline) hydroxyapatite has particles larger than 100 nanometres, typically in the range of a few micrometres. That size difference sounds technical, but it has meaningful consequences once the material is inside your mouth and potentially your body.

The remineralisation mechanism works for both sizes. Both can adhere to tooth surfaces, plug microcracks in enamel, and deliver calcium and phosphate to areas of demineralisation. So from a pure tooth care standpoint, non-nano does the job just as well.

Where they differ is in what happens if the particles are absorbed through the oral mucosa, swallowed, or inhaled as a fine mist from brushing.

The Health Concerns Around Nano Hydroxyapatite

Nanoparticles can behave differently from larger particles of the same material. Because they're so small, there's been a lot of concern raised about whether nano-sized particles might cross biological barriers, like the oral lining or cell membranes, that larger particles can't. This is exactly the question regulators have spent years investigating for nano hydroxyapatite (nano-HA).

The most thorough assessments come from the European Commission's Scientific Committee on Consumer Safety (SCCS), which has reviewed nano-HA in oral care several times:

• In 2016, the SCCS found there wasn't enough data to confirm safety, and specifically advised that needle-shaped particles should not be used in cosmetics.

• In its 2021 opinion, the committee reviewed rod-shaped nano-HA but still could not conclude it was safe, because the available data wasn't sufficient to rule out concerns about genotoxicity (potential effects on DNA).

• After industry submitted further data, the SCCS's March 2023 opinion concluded nano-HA is safe in toothpaste up to 10% and mouthwash up to 0.465%, but only for rod-shaped, uncoated particles, not needle-shaped or surface-modified ones. The EU subsequently wrote these limits into cosmetics law.

• A 2025 opinion (Submission IV) raised the toothpaste limit to 29.5%, again only for specific rod-shaped, uncoated particles, concluding that uptake through the oral lining is negligible and that any swallowed particles dissolve in stomach acid into calcium and phosphate.

So where does that leave us? The current regulatory position is that nano-HA is considered safe for oral care, but with conditions: only rod-shaped, uncoated nano-HA has been cleared as 'safe'. Needle-shaped particles have not, and the SCCS continues to advise against them. Not all nano-HA is equal, and the form used in a given product matters.

It's also worth mentioning there is still limited evidence. Much of the safety testing has been in vitro (cell-based) and over short timeframes, rather than long-term studies of daily use in real people, particularly young children, who swallow more toothpaste than adults. The science doesn't point to nano-HA being harmful, but long-term, real-world data is still sparse.

If you're using a nano-HA product, it's reasonable to look for one made with rod-shaped, uncoated particles at sensible concentrations, and to be a little more careful with young children who swallow toothpaste.

Why Micro (Non-Nano) Hydroxyapatite Has a Better Safety Profile

Microcrystalline hydroxyapatite particles are too large to cross biological barriers in the same way nanoparticles can. They sit on the tooth surface, do their remineralisation work, and if swallowed they pass through the gut like any other mineral. The body already manages calcium phosphate minerals at this scale as a normal part of metabolism.

This is why non-nano HA is the more conservative and arguably more sensible choice, especially for daily use and for children. The efficacy data shows it remineralises enamel effectively, and the absorption risk that complicates the nano picture simply doesn't apply at the micro scale.

When you're brushing twice a day every day for years, and if you have children who are brushing since infancy, the cumulative exposure question is real. Choosing non-nano removes that uncertainty without sacrificing any of the dental benefit.

Is Hydroxyapatite Toothpaste Better Than Fluoride?

This depends on what you're optimising for. Fluoride is well-studied and effective at reducing cavity rates. But it carries its own concerns at higher doses, including fluorosis (white spots or mottling on developing teeth) from excess ingestion in young children, and ongoing debate about the effects of systemic fluoride exposure from toothpaste, water, and food combined.

Non-nano hydroxyapatite offers a path to effective enamel remineralisation without those concerns. A 2019 in situ study published in BDJ Open found that a 10% hydroxyapatite toothpaste performed equivalently to a 500ppm fluoride toothpaste for remineralising early caries lesions and preventing demineralisation, and an 18-month clinical trial in adults (2023) found a non-nano hydroxyapatite toothpaste held its own against standard 1450ppm fluoride. For people wanting to avoid fluoride entirely, the evidence for non-nano HA as a substitute is well backed up by research.

Good Non-Nano Hydroxyapatite Toothpaste Options

Finding toothpaste that clearly specifies non-nano or microcrystalline hydroxyapatite takes a bit of work because many products just say "hydroxyapatite" without specifying the particle size. Here are some options worth looking at.

Red Seal Hydroxyapatite Toothpaste

Red Seal is widely available in New Zealand through Woolworths and Chemist Warehouse. Their hydroxyapatite toothpaste uses a micro form and is a reasonable accessible entry point. It's a familiar format, tubes, standard texture, and sits at a price point that's not much more than conventional toothpaste. A practical option if you want something you can grab at the supermarket.

Oh Gigi Organic Tooth Powder

Oh Gigi makes an organic tooth powder with hydroxyapatite that the brand formulates specifically to be safe for use by babies, toddlers, and children as well as adults. Tooth powder format takes a few days to get used to but it has no plastic tube, no glycerin, and a clean ingredient list. For families wanting one product that works across all ages, this is a solid pick. Available direct from ohgigi.co.

Grants Whitening + HA Natural Toothpaste

Grants is a long-standing Australian natural toothpaste brand available through HealthPost and other health retailers in New Zealand. Their whitening toothpaste with hydroxyapatite uses a non-nano form and is free from fluoride, SLS, and artificial flavours. It's a good everyday option with the added benefit of mild whitening action from the HA particle structure.

(*Affiliate link)

Stella Naturals Remineralising Toothpaste

Stella Naturals is a New Zealand made option with a remineralising formula built around hydroxyapatite. If you prefer to buy local and support a NZ-based small brand, this is worth considering. It's available online.

What to Look for on the Label

When you're choosing a hydroxyapatite toothpaste, look for the words "non-nano", "microcrystalline", or "micro hydroxyapatite" on the label or in the product description. If it just says "hydroxyapatite" or "nano-hydroxyapatite", that's not the 'safer' option by the current evidence.

Concentration also matters. Most studies showing efficacy used concentrations of 10% hydroxyapatite. Some products use less, which may be less effective at remineralisation. Check the ingredient listing or the brand's product page for the percentage if it's available.

For children under six who are still likely to swallow some toothpaste, non-nano is particularly important. The SCCS concerns about nano HA were partly driven by the swallowing risk in young children.

Summary

• Hydroxyapatite toothpaste remineralises enamel and is a credible fluoride-free alternative, with clinical evidence to back that up.

• Nano hydroxyapatite is now considered 'safe' by the European Commission's Scientific Committee on Consumer Safety under certain conditions: the particles must be rod-shaped (not needle-shaped), uncoated, and within set size and concentration limits. Forms that fall outside those conditions, such as needle-shaped or coated particles, haven't been cleared as safe.

• Non-nano (micro) hydroxyapatite has the same dental benefits without the associated concerns with nanoparticles.

• Look for "non-nano", "micro", or "microcrystalline" on the label. If it doesn't specify, ask the brand directly.

• Good accessible options include Red Seal, Grants HA Whitening, Oh Gigi tooth powder (suitable for all ages including babies), and Stella Naturals.

References

1. Limeback, H., Enax, J. & Meyer, F. (2021). Biomimetic hydroxyapatite and caries prevention: a systematic review and meta-analysis. Canadian Journal of Dental Hygiene, 55(3), 148–159. https://pmc.ncbi.nlm.nih.gov/articles/PMC8641555/

2. Pawinska, M., Paszynska, E., Amaechi, B.T., Meyer, F., Enax, J. & Limeback, H. (2024). Clinical evidence of caries prevention by hydroxyapatite: an updated systematic review and meta-analysis. Journal of Dentistry. https://www.sciencedirect.com/science/article/pii/S0300571224005992

3. Scientific Committee on Consumer Safety (SCCS). (2021). Opinion on Hydroxyapatite (nano), SCCS/1624/20. European Commission. https://health.ec.europa.eu/document/download/0639b45c-fc5f-4075-a46e-7d01d082c5d8_en?filename=sccs_o_246.pdf

4. Scientific Committee on Consumer Safety (SCCS). (2023). Opinion on Hydroxyapatite (nano), SCCS/1648/22. European Commission. https://health.ec.europa.eu/publications/hydroxyapatite-nano-0_en

5. Scientific Committee on Consumer Safety (SCCS). (2025). Scientific Opinion on Hydroxyapatite (nano) – Submission IV. European Commission. https://health.ec.europa.eu/publications/sccs-scientific-opinion-hydroxyapatite-nano-submission-iv_en

6. Amaechi, B.T. et al. (2019). Comparative efficacy of a hydroxyapatite and a fluoride toothpaste for prevention and remineralisation of dental caries in children. BDJ Open, 5, 18. https://pubmed.ncbi.nlm.nih.gov/31839988/

7. Paszynska, E. et al. (2023). Caries-preventing effect of a hydroxyapatite-toothpaste in adults: an 18-month double-blinded randomized clinical trial. Frontiers in Public Health. https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2023.1199728/full

Frequently Asked Questions

Do dentists recommend hydroxyapatite toothpaste?

Many dentists do recommend hydroxyapatite toothpaste, particularly for patients wanting a fluoride-free option. Clinical evidence supports its ability to remineralise early enamel lesions, and some studies have found it comparable to low-concentration fluoride toothpaste for cavity prevention. That said, recommendations vary by dentist and patient situation.

What is the difference between nano and non-nano hydroxyapatite toothpaste?

The difference is particle size. Nano hydroxyapatite has particles smaller than 100 nanometres, which raises concerns about their ability to cross biological barriers in the body. Non-nano (micro) hydroxyapatite has larger particles that stay on the tooth surface to do their remineralising work and pass through the body without the same absorption concerns.

Why not nano hydroxyapatite toothpaste?

Nano hydroxyapatite is now considered safe by the EU's Scientific Committee on Consumer Safety, but only for certain particle shapes, sizes and concentrations. We lean towards non-nano because it avoids those conditions altogether. Nanoparticles can potentially cross barriers in the body that larger particles can't, and long-term data on daily use is still limited. Non-nano hydroxyapatite gives you the same enamel-strengthening benefits without the same concerns.

Is hydroxyapatite toothpaste better than fluoride?

For many people, non-nano hydroxyapatite is a genuinely effective alternative to fluoride. Clinical trials have found 10% hydroxyapatite toothpaste performs comparably to standard fluoride toothpaste for remineralising early caries lesions. It avoids the concerns associated with fluoride ingestion, including fluorosis risk in young children.

Can you reverse cavities with hydroxyapatite toothpaste?

Hydroxyapatite toothpaste can remineralise early stage enamel lesions before they become physical holes. Once a cavity has broken through enamel into dentine, it requires dental treatment. Using a remineralising toothpaste consistently is most effective as a preventive measure or for very early demineralisation.

Is there a non-nano hydroxyapatite toothpaste available in New Zealand?

Yes. Options available in NZ include Red Seal's hydroxyapatite toothpaste (stocked at Woolworths), Grants Whitening + HA Natural Toothpaste (available through HealthPost), Oh Gigi Organic Tooth Powder (online, suitable for all ages including babies), and Stella Naturals Remineralising Toothpaste (NZ made).