Nano-Hydroxyapatite (nHA): Safety, Controversy & Oral Health
- Alex Kelly
- Oct 2, 2025
- 6 min read
Updated: Dec 18, 2025
Nano-hydroxyapatite (nHA) is a form of hydroxyapatite, the naturally occurring mineral that makes up the majority of our tooth enamel, broken down into ultra-fine particles. Because of its smaller particle size, nHA can penetrate more deeply into the enamel surface, making it especially effective for addressing tooth sensitivity and repairing early enamel erosion. However, despite its promising benefits in oral care, nHA has been the subject of some controversy, particularly concerning its safety and whether it can cross the blood-brain barrier.
Is nHA toxic?
Concerns about the safety of nano-hydroxyapatite (nHA) toothpaste often stem from early toxicological studies in animals, many of which involved intraperitoneal injections (an exposure route that does not reflect how humans use toothpaste).
A 2016 report by the European Commission’s Scientific Committee on Consumer Safety noted that extremely high doses of nHA caused serious effects such as cardiac and respiratory arrest in rats, along with tissue-specific impacts like lung proliferation, liver oxidative damage, kidney disruption, blood cell interference, and DNA damage. However, these outcomes occurred under unrealistic experimental conditions involving high systemic doses, not topical application.
For example, in this study, nano-hydroxyapatite (nHA) was administered to rats via oral gavage - a method involving delivering the nHA directly into the stomach using a tube. In this study, the nHA was delivered via intravenous injection, and this study was delivered through an injectable paste.
The Blood-Brain Barrier Debate
One common concern still raised is whether nano-hydroxyapatite from toothpaste can cross the blood-brain barrier. This fear is largely based on misinterpretations of research. Some studies in medical literature do involve engineered nanoparticles designed to target the brain for drug delivery, particularly in the treatment of central nervous system diseases. However, those particles are specifically engineered to cross the blood-brain barrier and are delivered through routes like injection or nasal sprays—not brushed onto teeth.
Can nHA Reach the Brain from Toothpaste?
For a substance in an oral care product to penetrate the blood brain barrier we have to ask: how is it going to get there? To enter the brain from a toothpaste, a substance would first need to enter systemic circulation, either through the gut or oral mucosa. Gut absorption is unlikely because nano-hydroxyapatite dissolves in the highly acidic environment of the stomach, which has a pH of 1.5–3.5. nHA begins dissolving at a pH of 4, meaning it would likely break down before ever reaching the bloodstream. And as mentioned earlier, studies show it does not penetrate the oral epithelium either.
Research on Topical Use in Oral Care
When it comes to oral care specifically, available research paints a very different picture. A key study evaluating toothpaste containing 10% nano-hydroxyapatite applied the substance directly to oral mucosa and found no penetration through the oral epithelium. This means the nHA remained on the surface and did not enter the bloodstream or systemic circulation. Furthermore, applying 10% nHA (50 nm particle size) to both keratinized and non-keratinized oral tissues for 24 hours found no evidence of tissue penetration, supporting the conclusion that systemic absorption through the mouth is highly unlikely.
When looking at research it's important to understand the full context behind the findings before trying to compare to oral care products: Is the particle shape known? Do they give the concentration? What was the method of delivery? How was the nHA prepared/for what purpose? What is specifically engineered to cross the BBB?
Particle Shape Matters
There are four main shapes of hydroxyapatite crystals: rod, sphere, amorphous, and needle. Research to date has only evaluated the rod-shaped and amorphous particles for safety in oral care products. The needle-shaped particles have not yet been studied in this context.
Concentration Matters
In 2023, the European Union released an official opinion confirming that nano-hydroxyapatite is safe for use in toothpaste at concentrations up to 10%, provided the particles are rod-shaped and not surface-coated or chemically modified. This highlights the importance of checking product labels (or reaching out to companies) for both concentration and particle shape to ensure you're using a well-tested form of nHA.
Pretty much all the commercial nHA toothpaste on the market is going to be 10% or below. While there isn’t usually a strict “ban” against higher concentrations, exceeding 10% could trigger regulatory scrutiny or require additional safety testing and approvals before a product can be marketed.
Additionally, there is some debate as to what the most effective concentration is. Research indicates that toothpaste formulations containing nHA at concentrations lower than 10% may be less effective in remineralizing enamel and reducing tooth sensitivity (1,2, 3, 4). However, there is also research indicating that lower concentrations may be just as effective as well (1, 2), especially if the source of the nHA is NanoXIM (as low as 3%) (1, 2, 3).
My Thoughts
I've gone back and forth on my personal thoughts on this. I have had conversations with Dr. Jennifer Eisenhuth who created Dr. Jen's 10% nHA toothpaste (one of the very few 10%), and she is pretty adament that anything under 10% is unlikely to provide true remineralization. But then there's Dr. Mark Burhenne, who disagrees. He created Fygg which is 3.1%, and I highly admire and respect him. When all the talk about "10% only" came out, he actually second guessed his own product and conducted his own research.
I personally remineralized a spot by using Risewell's Pro toothpaste with contains 5% nHA (and 10% micro), BUT I also did ozone therapy so I can't say with 100% confidence that the toothpaste alone helped or not.
But my initial leaning is for overall oral care and maintenance you'll probably be just fine with 3-5%, but if you're cavity prone or have a more serious spot you're actively trying to remineralize I would maybe consider 10% nHA like Dr. Jen.
*If you are prone to cavities, then there is a deeper root cause that is worth evaluation. I recommend a consult with an airway focused dentist.
Naturally Derived nHA from Eggshells
Most nHA toothpaste is made synthetically, which isn't necessarily a bad or "toxic" thing. But if this is something you'd still like to stay away from, there is naturally derived nano-hydroxyapatite, such as that sourced from eggshells, has shown promising safety data. A 2024 study published in the Arab Gulf Journal of Scientific Research concluded that eggshell nHA exhibited no toxicity toward human osteoblast and fibroblast cells, and even enhanced cell viability, making it a biocompatible option for dental use. Dr. Jen has a great egg-shell nHA derived toothpaste.
What about Micro-Hydroxyapatite (or non-nano)?
This research article reflects a scientific consensus, backed by 37 studies, indicating that micro-HA crystals are largely ineffective. While they may offer limited surface-level remineralization, their significantly larger size compared to natural enamel HA and dentinal tubules reduces their overall effectiveness in promoting deeper remineralization and alleviating sensitivity.
Conclusion: Is nHA Safe in Toothpaste?
In summary, while high-dose animal studies raised theoretical concerns about nano-hydroxyapatite, these scenarios do not reflect real-world exposure via toothpaste. Current research supports the safety of nHA in oral care when used at or below a 10% concentration, particularly when composed of rod-shaped particles. Misinformation often arises from unrelated research on drug delivery nanoparticles and does not apply to topical dental products. Based on the evidence available, nano-hydroxyapatite remains a promising and safe ingredient for remineralization and sensitivity relief when used appropriately.
Damned if You Do, Damned if You Don't
This can certainly feel like the case when it comes to topics where one "expert" says xyz is great, and another says it's terrible. I really encourage you to do your own research, and at the end of the day do what's going to make you feel comfortable. That's going to look different for every family, and that's okay!
If nHA still makes you leery, xylitol is a great alternative with tons of backed research. Most nHA toothpastes include xylitol, but there are many xylitol options without nHA. I would just recommend looking for one that doesn't also contain sorbitol. While very slow, sorbitol can be fermented by oral bacteria - whereas xylitol cannot. Erythritol also cannot be fermented by oral bacteria, so this is a decent option as well. Additionally, make sure you're breathing properly and are maintaining ideal health and you really don't even need toothpaste.
Toothpaste Hasn't Always Been Necessary
Dental disease is a systemic problem. If you're eating right, exercising well, BREATHING PROPERLY, have proper jaw development, and your blood chemistry is ideal because you’re taking in all the right things - then the PH in your mouth is going to be an alkaline environment and your saliva will provide the very minerals your teeth need.
Unfortunately, we don’t live in a perfect world and most people’s systems (especially in the West) stay in a state of cellular inflammation with an oral PH that is conducive for building up anaerobic bacteria, making us more prone to tooth decay.
The early 20th century-records (1,2) document virtually no tooth decay in pre-contact Inuit. And guess what? They didn't have toothpaste! By the 2000’s surveys showed nearly 69% of Inuit preschoolers had cavities by age 5. Why do you think this age? A major shift in diet change.
Weston A. Price compared isolated indigenous diets vs Western processed diets, and found only 0.1% of traditional indigenous diet teeth had cavities, vs 23% in processed-diet groups.
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