Last updated 14 October 2026 · By Marisa Battrick, founder and formulator

Hydroxyapatite toothpaste is fast becoming one of the most popular alternatives in modern oral care. Unlike most toothpaste ingredients, hydroxyapatite works by replacing the same mineral your teeth are naturally made from.

If you've started looking at nano hydroxyapatite toothpaste, you'll have come across two terms: nano hydroxyapatite and micro hydroxyapatite. So what's the difference, and which one is better for remineralising teeth?

In this guide we explain nano vs micro hydroxyapatite, how particle size affects remineralisation, whether nano hydroxyapatite is safe, whether micro hydroxyapatite is effective, and why we chose micro hydroxyapatite for Truthpaste.

What Is Hydroxyapatite Toothpaste?

Hydroxyapatite is the main mineral that forms human teeth. Around 97% of tooth enamel and 70% of dentin is made from hydroxyapatite crystals.

When teeth are exposed to acids from bacteria, food or drinks, minerals such as calcium and phosphate dissolve from the enamel surface. This is called demineralisation.

Hydroxyapatite toothpaste helps reverse this by supplying minerals that attach to the enamel surface and replace lost tooth mineral. Studies show hydroxyapatite can help:

• strengthen enamel
• reduce tooth sensitivity
• protect teeth from acid damage
• smooth rough enamel surfaces

Because hydroxyapatite is the same mineral your teeth naturally contain, it works in a biomimetic way, meaning it mimics the natural structure of enamel. (PMID: 34807345)

Nano vs Micro Hydroxyapatite: Understanding Particle Size

The main difference between nano hydroxyapatite and micro hydroxyapatite is particle size. Both are the same mineral, produced at different scales.

Nano hydroxyapatite

Nano hydroxyapatite particles are extremely small, typically between 20 and 80 nanometres. There are 1,000 nanometres in one micrometre (micron).

Micro hydroxyapatite

Micro hydroxyapatite particles are larger and measured in microns rather than nanometres, usually somewhere between 1 and 10 microns. The micro hydroxyapatite we use at Truthpaste is 1.5 microns.

Both nano and micro hydroxyapatite particles can:

• reach microscopic enamel defects
• enter exposed dentinal tubules
• form a mineral layer across the tooth surface

Many people assume micro particles are too large to interact with tooth structures, but that depends entirely on the actual particle size compared with the microscopic structures in teeth.

Can Micro Hydroxyapatite Penetrate Dentinal Tubules?

Yes, if the particles are small enough.

When enamel becomes worn or demineralised, microscopic channels called dentinal tubules can become exposed. These connect to the inner structure of the tooth and are often linked to tooth sensitivity.

Dentinal tubules typically measure around 2 to 3 microns in diameter, with an average of about 2.5 microns. Truthpaste uses micro hydroxyapatite particles of around 1.5 microns.

Because these particles are smaller than exposed dentinal tubules, they can enter these channels and help block them, a key way of reducing tooth sensitivity. This allows micro hydroxyapatite to:

• enter exposed dentinal tubules linked to sensitivity
• deposit calcium and phosphate minerals
• help block the pathways that cause sensitivity
• support enamel remineralisation

With daily brushing, hydroxyapatite gradually builds a protective mineral layer and strengthens weakened areas of enamel.

Is Nano Hydroxyapatite Safe?

Nano hydroxyapatite has been extensively studied and is widely used in oral care, particularly in Japan.

Because nanoparticles are so small, there has been ongoing scientific discussion about how they behave in the body. In Europe, nano hydroxyapatite is regulated as a nanomaterial. The European Scientific Committee on Consumer Safety (SCCS) has assessed it and concluded that only specific forms are safe under defined conditions, while recommending continued monitoring and research.

If you choose a nano hydroxyapatite toothpaste, two things are worth checking:

• The label: nanomaterials must be listed with "(nano)" after the ingredient name, so you can see what you're buying.
• The particle shape: the forms assessed as safe are rod-shaped rather than needle-shaped. Many different forms are sold around the world, and not all conform to EU safety guidelines.

This is why some brands and customers prefer non-nano hydroxyapatite.

Is Nano Hydroxyapatite Toothpaste Better Than Micro?

Not necessarily. Both nano and micro hydroxyapatite have been clinically studied, and both support remineralisation. Much of the early research used nano particles, while more recent clinical trials comparing hydroxyapatite with fluoride for preventing decay have used microcrystalline hydroxyapatite.

What matters most is the particle size compared with the structures in your teeth, the amount of hydroxyapatite in the formula, and what else is in the tube.

Is Micro Hydroxyapatite Effective?

Yes. You'll sometimes read that hydroxyapatite has to be nano to work. It's an understandable assumption, because much of the early research used nano particles, but the clinical evidence doesn't back it up.

Several of the strongest trials of hydroxyapatite toothpaste have used microcrystalline (micro) hydroxyapatite, and compared it directly with fluoride toothpaste:

• Children, 1 year: in a double-blind randomised trial of 207 children, a toothpaste with microcrystalline hydroxyapatite was not inferior to a fluoride toothpaste at preventing early childhood caries (Paszynska et al., 2021, Scientific Reports).
• Orthodontic patients, 6 months: in 147 highly caries-prone patients wearing braces, a fluoride-free microcrystalline hydroxyapatite toothpaste performed no differently from a 1,400 ppm fluoride toothpaste (Schlagenhauf et al., 2019, Journal of Investigative and Clinical Dentistry).
• Adults, 18 months: in a double-blind randomised trial of 189 adults, a fluoride-free hydroxyapatite toothpaste was not inferior to a 1,450 ppm fluoride toothpaste (Paszynska et al., 2023, Frontiers in Public Health).

A 2024 systematic review and meta-analysis of the clinical evidence concluded that hydroxyapatite is effective as an anti-caries ingredient in the absence of fluoride (Pawinska et al., 2024, Journal of Dentistry).

Tooth enamel under polarised light, before (left) and after (right) one brushing with biomimetic hydroxyapatite. The arrow shows the new mineral layer deposited on the surface.

Why micro particles still work on the tooth surface

Under a microscope, a micro hydroxyapatite particle isn't a smooth, solid lump. It's a cluster of tiny crystals, similar in structure to the crystals in natural enamel. That's what allows it to bind to the tooth surface, settle into microscopic defects and build up a mineral layer as you brush.

Electron microscope images of biomimetic hydroxyapatite at the junction between enamel and dentin. The close-up (right) shows the solid mineral bridges it forms with the tooth.

Particle size still matters, though. Too large and the particles can't reach the structures they need to. That's why we use 1.5 micron particles: small enough to enter dentinal tubules of around 2.5 microns, without using nanoparticles.

Why We Use Micro Hydroxyapatite

Micro hydroxyapatite gives the same enamel benefits without using nanoparticles. When particle size is carefully controlled, micro hydroxyapatite still interacts with the microscopic structures in teeth and replaces lost mineral. It helps:

• strengthen enamel
• reduce tooth sensitivity
• smooth rough enamel surfaces
• support remineralisation

For anyone looking for hydroxyapatite toothpaste without nanoparticles, micro hydroxyapatite is an effective alternative.

Truthpaste Hydroxyapatite Toothpaste

Does Hydroxyapatite Toothpaste Rebuild Enamel?

Hydroxyapatite doesn't replace whole layers of enamel, but it rebuilds mineral structure and helps repair and remineralise the enamel surface.

When you brush with hydroxyapatite toothpaste, mineral particles attach to the enamel surface and replace minerals lost during acid attacks. This can:

• restore mineral density
• strengthen weakened enamel
• reduce sensitivity
• improve enamel smoothness

Over time, daily brushing supports the natural remineralisation process that keeps teeth strong.

Hydroxyapatite vs Fluoride Toothpaste

Hydroxyapatite and fluoride toothpaste protect teeth in different ways. Fluoride helps enamel become more resistant to acid attacks. Hydroxyapatite works by supplying minerals that integrate directly into the enamel surface.

Research suggests hydroxyapatite toothpaste can perform similarly to fluoride toothpaste in preventing cavities under certain conditions, which is why it's increasingly used in fluoride-free toothpaste.

Choosing the Best Hydroxyapatite Toothpaste

When choosing a hydroxyapatite toothpaste, look at:

• whether it uses nano or micro hydroxyapatite (check for "(nano)" on the label)
• the particle size of the mineral
• the concentration of hydroxyapatite. It's an expensive ingredient, so some brands only add a small amount
• what else is in the formula, such as SLS or titanium dioxide
• whether the formula supports the oral microbiome

A well-designed formula helps strengthen enamel and supports long-term oral health.

FAQ: Nano and Micro Hydroxyapatite

What is the difference between nano and micro hydroxyapatite?

The main difference is particle size. Nano hydroxyapatite particles are measured in nanometres, while micro hydroxyapatite particles are measured in microns. Both support enamel remineralisation, but some brands prefer micro hydroxyapatite to avoid using nanoparticles.

Does hydroxyapatite have to be nano to work?

No. Clinical trials in children, adults and orthodontic patients have shown microcrystalline hydroxyapatite toothpaste performing as well as fluoride toothpaste at preventing decay. What matters is that the particles are small enough to reach the structures in your teeth, and that there's enough hydroxyapatite in the formula.

Is nano hydroxyapatite banned in Europe?

No, nano hydroxyapatite is not banned, but it is regulated. The European Scientific Committee on Consumer Safety (SCCS) has assessed it and concluded that specific forms may be safe when used under certain conditions.

Is Truthpaste nano hydroxyapatite?

No. Truthpaste uses micro biomimetic hydroxyapatite at 1.5 microns: 5% in our toothpastes and 12% in the Enamel Repair Mask.

Does hydroxyapatite toothpaste really work?

Research shows hydroxyapatite toothpaste can help remineralise enamel, reduce tooth sensitivity and protect teeth from acid damage. Because it's the same mineral that forms tooth enamel, it works in a biomimetic way to support natural remineralisation.

Is hydroxyapatite better than fluoride?

They work differently. Fluoride makes enamel more resistant to acid attacks, while hydroxyapatite replaces minerals lost from enamel. Both can support oral health depending on the formula and your individual needs.