Short answer: it describes the size and the shape of the mineral particles in your toothpaste. Nano means the particles are smaller than 100 nanometres. Rod shaped means they are short and slightly elongated, like the crystals in your own enamel. Both details change how the mineral behaves on your teeth, and whether it fits the form that safety regulators have assessed.

First, what is hydroxyapatite?

About 97% of your enamel is one mineral: hydroxyapatite. A hydroxyapatite toothpaste uses a lab made version of that same mineral, so you are brushing with what your teeth are already made of.

Not all hydroxyapatite is the same, though. Two things set one apart from another: how big the particles are, and what shape they are.

Size: nano versus micro

A nanometre is one millionth of a millimetre. Nano hydroxyapatite (nHA) particles are under 100 nanometres. Micro hydroxyapatite particles are around a thousand times larger, measured in micrometres.

Smaller particles have more surface area and can settle into the tiny gaps on the surface of your enamel. Larger particles tend to sit on top of it. Both are used in toothpaste, but they are not interchangeable, and a label that just says "hydroxyapatite" does not tell you which one you are getting.

The particles in Bastét are around 20 nanometres.

Shape: rods versus needles

Hydroxyapatite can be made in different shapes. The crystals in your enamel are long and slender, packed together in tight bundles. Rod shaped nHA is the closest match.

Shape also matters for safety. In July 2025, the EU Scientific Committee on Consumer Safety concluded that nano hydroxyapatite is safe in toothpaste at up to 29.5%. That conclusion applies to rod shaped particles that are not coated or surface modified. It does not apply to needle shaped particles.

Why "uncoated" matters

Some nano materials are coated to change how they disperse in a formula. The EU safety assessment covers uncoated hydroxyapatite only. An uncoated particle also means nothing sits between the mineral and your tooth.

What to look for on a label

• The word nano. "Hydroxyapatite" alone could be micro.
• A stated percentage. 10% is the level used in most of the research comparing nHA with fluoride.
• Pure nHA, not a suspension. Some formulas add nHA as a premade liquid, so the percentage on the label refers to the liquid, not the mineral.
• Particle shape. Brands that use rod shaped nHA usually say so.

For the full checklist, see our guide to choosing a nano hydroxyapatite toothpaste.

Quick answers

What is rod shaped nano hydroxyapatite?
Hydroxyapatite particles under 100 nanometres, shaped like short rods, which most closely resemble the crystals in your enamel.

Is nano hydroxyapatite safe?
The EU's scientific safety committee concluded in 2025 that rod shaped, uncoated nano hydroxyapatite is safe in toothpaste at up to 29.5%. It also noted that swallowed particles dissolve quickly in stomach acid.

Is nano better than micro hydroxyapatite?
Nano particles are small enough to settle into the surface of your enamel, while micro particles mostly sit on top. Most of the research comparing hydroxyapatite with fluoride used nano particles at 10%.

What is in Bastét

Bastét French Mint Toothpaste uses 10% pure nano hydroxyapatite: rod shaped, around 20 nanometres, uncoated, and dispersed into the paste in our lab in Canada. The percentage is printed on the tube.

Shop French Mint Toothpaste · See every ingredient

Written by Alexandra Baker, co-founder of Bastét.