Hydroxyapatite and nano-hydroxyapatite toothpastes are currently having a bit of a moment, particularly as an alternative to fluoride toothpaste.
Hydroxyapatite is a very familiar term if you’ve studied anything dental-ish. It’s the substance that makes up most of our tooth enamel. Nano-hydroxyapatite is essentially the same thing, but in much tinier particles.
How does hydroxyapatite help teeth?
The idea is that these particles can settle onto the tooth surface and nestle into tiny areas where mineral has been lost.
That sounds quite appealing, obviously. Your enamel has lost some mineral, so you put back something very similar to the mineral your enamel is already made from.
It can also help with sensitive teeth. Most of the time, teeth become sensitive when the inner part of the tooth, called dentine, becomes exposed. Dentine contains thousands of microscopic little channels that lead towards the nerve inside the tooth. Studies do suggest that the right kind of hydroxyapatite particles can help physically block those channels.
But, like most things in toothpaste formulation, it’s not quite as simple as:
Add hydroxyapatite = magical toothpaste that repairs teeth.
This is a very complicated topic, but I will do my best.
First off, what does the research actually say?
There are some clinical studies where hydroxyapatite toothpaste has been tested against fluoride toothpaste.
You’ll sometimes see this described as hydroxyapatite being “non-inferior” to a certain concentration of fluoride. That phrase sounds a bit clunky, but all it really means is that, in that particular study, the hydroxyapatite toothpaste didn’t perform enough worse than the fluoride toothpaste for the researchers to consider the difference important.
It does not mean scientists have proved that every hydroxyapatite toothpaste is exactly as effective as fluoride.
One study looked at people wearing braces, who are particularly prone to developing early areas of demineralisation around the brackets. A toothpaste containing 10% microcrystalline hydroxyapatite was compared with a 1400 ppm fluoride toothpaste and met the study’s non-inferiority test.
There has also been a one-year study in children comparing 10% microcrystalline hydroxyapatite with a 500 ppm fluoride toothpaste, and an 18-month study in adults comparing 10% microcrystalline hydroxyapatite with 1450 ppm fluoride, which is around the strength you’ll find in many standard adult fluoride toothpastes. Again, the hydroxyapatite toothpaste was found to be non-inferior.
One fairly important caveat though: all three of these head-to-head studies used the same Karex formulation family, containing 10% microcrystalline hydroxyapatite, and the research was funded or supported by the manufacturer behind Karex.
That doesn’t automatically mean the results are unreliable. Toothpaste studies are expensive, and manufacturers often fund research into their own products. But I’d still like to see the same sort of results repeated independently, with other hydroxyapatite formulations too.
There is also older research from Japan, where hydroxyapatite toothpaste has been sold since around the 1980s. Japanese studies found lower rates of decay with hydroxyapatite toothpaste compared with toothpaste without hydroxyapatite, and this research helped support its approval there as an anti-caries ingredient decades ago.
So hydroxyapatite definitely isn’t a brand new ingredient with no evidence behind it.
But if the question is whether it should completely replace fluoride, I’d like much, much, much more independent research. Fluoride toothpaste has decades of research and hundreds of clinical trials behind it.
Hydroxyapatite has some genuinely promising results, but those results relate to particular types and concentrations of hydroxyapatite, not simply to the ingredient being present.
Particle size and shape matter
Another thing I’ve found in my research is that hydroxyapatite is a really… difficult ingredient compared with a lot of others.
There are so many different grades, with different particle sizes, shapes and levels of purity. And those differences can affect how the ingredient behaves on the tooth.
So a hydroxyapatite toothpaste maker can’t really point to a study using a completely different type, particle size and concentration of hydroxyapatite and assume those results automatically apply to their toothpaste.
Basically, two toothpastes can both say “hydroxyapatite toothpaste” on the label, while one contains a well-researched form at a meaningful concentration and the other may contain something quite different at a level that does very little.
The cost of hydroxyapatite
There’s another thing that makes me suspicious of some of the very cheap nano-HAp toothpastes: the cost.
I was looking into the best type of nano-HAp for sensitivity and was quoted around US$380 per kilogram. Plus shipping! I didn’t order that particular one, but the sample I ended up choosing was also pretty pricey.
Which does make me wonder: how on earth are some brands selling nano-HAp toothpaste for $6 a tube?
Microcrystalline hydroxyapatite can be considerably cheaper, so this doesn’t apply to every type of HAp. But if I saw a very cheap nano-HAp toothpaste, I’d definitely want to know what grade it contains and at what percentage.
Which brings me to the next question.
How much hydroxyapatite is actually in a hydroxyapatite toothpaste?
In cosmetic formulating, there is this thing called a claims ingredient.
You can put a very small amount of an exciting ingredient into a product and then build the whole marketing story around it.
A face cream might talk endlessly about some rare plant extract that actually makes up a fraction of one percent of the formula.
They’re not lying. The ingredient is definitely in there. Whether there is enough of it to do what you think you’re buying it for is a different question.
The same thing can happen with hydroxyapatite. There are toothpastes on the market containing less than 1%.
That doesn’t automatically mean they do nothing. Sometimes ingredients work very well at low levels.
But if most of the research being used to promote an ingredient is based on products containing 5% or 10%, then I’m interested in how much is actually in the toothpaste. And the people buying it should be too.
How can you find out?
Ask the company! Hopefully, they’ll be happy to share.
Google Patents. If it’s a patented product, you may be able to see the approximate formulation.
Google the product name + “SDS”. You might be able to find its Safety Data Sheet.
Hopefully this helps explain why saying “hydroxyapatite toothpaste” isn’t really the same as saying “fluoride toothpaste”.
You need to consider: Nano? Microcrystalline? What size particles? What shape? What percentage?
Because “contains hydroxyapatite” doesn’t really tell you very much on its own. And that matters if you’re relying on it to help strengthen and protect your teeth.
Why I’m most interested in it for sensitivity
The main reason I’ve ordered some nano-hydroxyapatite is that I’m really interested to see what it can do for sensitive teeth.
There is good evidence that hydroxyapatite can help block the tiny exposed channels in dentine that cause sensitivity, and one of the things I’m interested in is whether the smaller particles in the nano form might be particularly useful for this.
Basically: can I add it into our Sensitive Extra Protection toothpaste and make a super-powered sensitive toothpaste?
That’s the bit I’m most interested in finding out.
What about whitening?
I’m interested in this too.
Hydroxyapatite is often described as having a subtle whitening effect when used in toothpaste. Though it works quite differently from hydrogen peroxide, which is the whitening ingredient we currently use in Solid Teeth Whitening.
Instead, the idea is that teeny tiny hydroxyapatite particles can deposit onto and “fill in” tiny rough areas on the enamel surface. This can make the surface smoother and change the way it reflects light.
There is some research suggesting it can improve tooth colour, but I wouldn’t put it in the same category as peroxide whitening.
Still, I’m very curious to see whether I can notice anything when it’s used at a decent percentage.
Would I use hydroxyapatite instead of fluoride?
Despite lots of Facebook comments telling me I should do this, at this stage, no.
I think hydroxyapatite is a genuinely interesting ingredient. There is enough evidence now that I think it would be unfair to dismiss it as a fad or marketing gimmick.
But fluoride is still the gold standard for preventing tooth decay. It works, it’s inexpensive, and we have a huge amount of research telling us what concentration to use it at.
This blog isn’t going to go into the safety of fluoride toothpaste. You can find that here.
If fluoride is excellent at helping prevent decay, and hydroxyapatite turns out to be especially useful for sensitivity and helping replace mineral at the tooth surface, then I’m much more interested in how they can work together.
And actually, I suspect this may be where hydroxyapatite ends up long term. Not replacing fluoride completely, but being used alongside it in more advanced toothpastes.
So, are we making one?
At the moment I’ve got an expensive sample of nano-hydroxyapatite sitting on my desk.
First, I want to see what it’s actually like to formulate with.
I want to see how much I can add before the toothpaste becomes… bad. What happens to the taste, texture and stability? How does it feel on the teeth? And do I actually notice anything with sensitivity or whitening?
If we do eventually add this ingredient into our range, I don’t think it will be as a fluoride-free toothpaste using hydroxyapatite instead.
As mentioned above, I just don’t really see the point. And the thought that I might not be providing people with the best protection I can for their teeth doesn’t sit right with me as a dental professional.
I’m much more interested in whether I can use it alongside ingredients we already know work and make our sensitive toothpaste even better.
That, to me, is much more interesting than being another brand putting another fluoride-free toothpaste out into the world that might work as well as fluoride.
Have you thought about using hydroxyapatite toothpaste?
References and further reading
If you’d like to dig into the research yourself, these are some of the main studies and reviews I referred to.
The three Karex-related head-to-head studies
Hydroxyapatite vs 1400 ppm fluoride in people wearing braces Schlagenhauf U, et al. 2019. Impact of a non-fluoridated microcrystalline hydroxyapatite dentifrice on enamel caries progression in highly caries-susceptible orthodontic patients. https://pmc.ncbi.nlm.nih.gov/articles/PMC6590169/
10% microcrystalline hydroxyapatite vs 500 ppm fluoride in children Paszynska E, et al. 2021. Impact of a toothpaste with microcrystalline hydroxyapatite on the occurrence of early childhood caries: a 1-year randomized clinical trial. https://www.nature.com/articles/s41598-021-81112-y
10% hydroxyapatite vs 1450 ppm fluoride in adults over 18 months Paszynska E, et al. 2023. Caries-preventing effect of a hydroxyapatite-toothpaste in adults: an 18-month double-blinded randomized clinical trial. https://pubmed.ncbi.nlm.nih.gov/37533523/
Reviews and other evidence
Systematic review and meta-analysis of hydroxyapatite for preventing tooth decay Pawinska M, Paszynska E, Amaechi BT, Meyer F, Enax J, Limeback H. 2024. Clinical evidence of caries prevention by hydroxyapatite: an updated systematic review and meta-analysis. https://doi.org/10.1016/j.jdent.2024.105429
Nano-hydroxyapatite for sensitive teeth: systematic review and meta-analysis Alencar CM, et al. 2019. Clinical efficacy of nano-hydroxyapatite in dentin hypersensitivity. https://pubmed.ncbi.nlm.nih.gov/30611773/
Hydroxyapatite for dentine sensitivity: broader systematic review Limeback H, Meyer F, Enax J. 2023. Clinical Evidence of Biomimetic Hydroxyapatite in Oral Care Products for Reducing Dentin Hypersensitivity. https://pmc.ncbi.nlm.nih.gov/articles/PMC9844412/
Hydroxyapatite and tooth whitening: systematic review Limeback H, Meyer F, Enax J. 2023. Tooth Whitening with Hydroxyapatite: A Systematic Review. https://pmc.ncbi.nlm.nih.gov/articles/PMC9955010/
Hydroxyapatite Toothpaste: Does It Actually Work?
Hydroxyapatite and nano-hydroxyapatite toothpastes are currently having a bit of a moment, particularly as an alternative to fluoride toothpaste.
Hydroxyapatite is a very familiar term if you’ve studied anything dental-ish. It’s the substance that makes up most of our tooth enamel. Nano-hydroxyapatite is essentially the same thing, but in much tinier particles.
How does hydroxyapatite help teeth?
The idea is that these particles can settle onto the tooth surface and nestle into tiny areas where mineral has been lost.
That sounds quite appealing, obviously. Your enamel has lost some mineral, so you put back something very similar to the mineral your enamel is already made from.
It can also help with sensitive teeth. Most of the time, teeth become sensitive when the inner part of the tooth, called dentine, becomes exposed. Dentine contains thousands of microscopic little channels that lead towards the nerve inside the tooth. Studies do suggest that the right kind of hydroxyapatite particles can help physically block those channels.
But, like most things in toothpaste formulation, it’s not quite as simple as:
Add hydroxyapatite = magical toothpaste that repairs teeth.
This is a very complicated topic, but I will do my best.
First off, what does the research actually say?
There are some clinical studies where hydroxyapatite toothpaste has been tested against fluoride toothpaste.
You’ll sometimes see this described as hydroxyapatite being “non-inferior” to a certain concentration of fluoride. That phrase sounds a bit clunky, but all it really means is that, in that particular study, the hydroxyapatite toothpaste didn’t perform enough worse than the fluoride toothpaste for the researchers to consider the difference important.
It does not mean scientists have proved that every hydroxyapatite toothpaste is exactly as effective as fluoride.
One study looked at people wearing braces, who are particularly prone to developing early areas of demineralisation around the brackets. A toothpaste containing 10% microcrystalline hydroxyapatite was compared with a 1400 ppm fluoride toothpaste and met the study’s non-inferiority test.
There has also been a one-year study in children comparing 10% microcrystalline hydroxyapatite with a 500 ppm fluoride toothpaste, and an 18-month study in adults comparing 10% microcrystalline hydroxyapatite with 1450 ppm fluoride, which is around the strength you’ll find in many standard adult fluoride toothpastes. Again, the hydroxyapatite toothpaste was found to be non-inferior.
One fairly important caveat though: all three of these head-to-head studies used the same Karex formulation family, containing 10% microcrystalline hydroxyapatite, and the research was funded or supported by the manufacturer behind Karex.
That doesn’t automatically mean the results are unreliable. Toothpaste studies are expensive, and manufacturers often fund research into their own products. But I’d still like to see the same sort of results repeated independently, with other hydroxyapatite formulations too.
There is also older research from Japan, where hydroxyapatite toothpaste has been sold since around the 1980s. Japanese studies found lower rates of decay with hydroxyapatite toothpaste compared with toothpaste without hydroxyapatite, and this research helped support its approval there as an anti-caries ingredient decades ago.
So hydroxyapatite definitely isn’t a brand new ingredient with no evidence behind it.
But if the question is whether it should completely replace fluoride, I’d like much, much, much more independent research. Fluoride toothpaste has decades of research and hundreds of clinical trials behind it.
Hydroxyapatite has some genuinely promising results, but those results relate to particular types and concentrations of hydroxyapatite, not simply to the ingredient being present.
Particle size and shape matter
Another thing I’ve found in my research is that hydroxyapatite is a really… difficult ingredient compared with a lot of others.
There are so many different grades, with different particle sizes, shapes and levels of purity. And those differences can affect how the ingredient behaves on the tooth.
So a hydroxyapatite toothpaste maker can’t really point to a study using a completely different type, particle size and concentration of hydroxyapatite and assume those results automatically apply to their toothpaste.
Basically, two toothpastes can both say “hydroxyapatite toothpaste” on the label, while one contains a well-researched form at a meaningful concentration and the other may contain something quite different at a level that does very little.
The cost of hydroxyapatite
There’s another thing that makes me suspicious of some of the very cheap nano-HAp toothpastes: the cost.
I was looking into the best type of nano-HAp for sensitivity and was quoted around US$380 per kilogram. Plus shipping! I didn’t order that particular one, but the sample I ended up choosing was also pretty pricey.
Which does make me wonder: how on earth are some brands selling nano-HAp toothpaste for $6 a tube?
Microcrystalline hydroxyapatite can be considerably cheaper, so this doesn’t apply to every type of HAp. But if I saw a very cheap nano-HAp toothpaste, I’d definitely want to know what grade it contains and at what percentage.
Which brings me to the next question.
How much hydroxyapatite is actually in a hydroxyapatite toothpaste?
In cosmetic formulating, there is this thing called a claims ingredient.
You can put a very small amount of an exciting ingredient into a product and then build the whole marketing story around it.
A face cream might talk endlessly about some rare plant extract that actually makes up a fraction of one percent of the formula.
They’re not lying. The ingredient is definitely in there. Whether there is enough of it to do what you think you’re buying it for is a different question.
The same thing can happen with hydroxyapatite. There are toothpastes on the market containing less than 1%.
That doesn’t automatically mean they do nothing. Sometimes ingredients work very well at low levels.
But if most of the research being used to promote an ingredient is based on products containing 5% or 10%, then I’m interested in how much is actually in the toothpaste. And the people buying it should be too.
How can you find out?
Hopefully this helps explain why saying “hydroxyapatite toothpaste” isn’t really the same as saying “fluoride toothpaste”.
You need to consider: Nano? Microcrystalline? What size particles? What shape? What percentage?
Because “contains hydroxyapatite” doesn’t really tell you very much on its own. And that matters if you’re relying on it to help strengthen and protect your teeth.
Why I’m most interested in it for sensitivity
The main reason I’ve ordered some nano-hydroxyapatite is that I’m really interested to see what it can do for sensitive teeth.
There is good evidence that hydroxyapatite can help block the tiny exposed channels in dentine that cause sensitivity, and one of the things I’m interested in is whether the smaller particles in the nano form might be particularly useful for this.
Basically: can I add it into our Sensitive Extra Protection toothpaste and make a super-powered sensitive toothpaste?
That’s the bit I’m most interested in finding out.
What about whitening?
I’m interested in this too.
Hydroxyapatite is often described as having a subtle whitening effect when used in toothpaste. Though it works quite differently from hydrogen peroxide, which is the whitening ingredient we currently use in Solid Teeth Whitening.
Instead, the idea is that teeny tiny hydroxyapatite particles can deposit onto and “fill in” tiny rough areas on the enamel surface. This can make the surface smoother and change the way it reflects light.
There is some research suggesting it can improve tooth colour, but I wouldn’t put it in the same category as peroxide whitening.
Still, I’m very curious to see whether I can notice anything when it’s used at a decent percentage.
Would I use hydroxyapatite instead of fluoride?
Despite lots of Facebook comments telling me I should do this, at this stage, no.
I think hydroxyapatite is a genuinely interesting ingredient. There is enough evidence now that I think it would be unfair to dismiss it as a fad or marketing gimmick.
But fluoride is still the gold standard for preventing tooth decay. It works, it’s inexpensive, and we have a huge amount of research telling us what concentration to use it at.
This blog isn’t going to go into the safety of fluoride toothpaste. You can find that here.
If fluoride is excellent at helping prevent decay, and hydroxyapatite turns out to be especially useful for sensitivity and helping replace mineral at the tooth surface, then I’m much more interested in how they can work together.
And actually, I suspect this may be where hydroxyapatite ends up long term. Not replacing fluoride completely, but being used alongside it in more advanced toothpastes.
So, are we making one?
At the moment I’ve got an expensive sample of nano-hydroxyapatite sitting on my desk.
First, I want to see what it’s actually like to formulate with.
I want to see how much I can add before the toothpaste becomes… bad. What happens to the taste, texture and stability? How does it feel on the teeth? And do I actually notice anything with sensitivity or whitening?
If we do eventually add this ingredient into our range, I don’t think it will be as a fluoride-free toothpaste using hydroxyapatite instead.
As mentioned above, I just don’t really see the point. And the thought that I might not be providing people with the best protection I can for their teeth doesn’t sit right with me as a dental professional.
I’m much more interested in whether I can use it alongside ingredients we already know work and make our sensitive toothpaste even better.
That, to me, is much more interesting than being another brand putting another fluoride-free toothpaste out into the world that might work as well as fluoride.
Have you thought about using hydroxyapatite toothpaste?
References and further reading
If you’d like to dig into the research yourself, these are some of the main studies and reviews I referred to.
The three Karex-related head-to-head studies
Schlagenhauf U, et al. 2019. Impact of a non-fluoridated microcrystalline hydroxyapatite dentifrice on enamel caries progression in highly caries-susceptible orthodontic patients.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6590169/
Paszynska E, et al. 2021. Impact of a toothpaste with microcrystalline hydroxyapatite on the occurrence of early childhood caries: a 1-year randomized clinical trial.
https://www.nature.com/articles/s41598-021-81112-y
Paszynska E, et al. 2023. Caries-preventing effect of a hydroxyapatite-toothpaste in adults: an 18-month double-blinded randomized clinical trial.
https://pubmed.ncbi.nlm.nih.gov/37533523/
Reviews and other evidence
Pawinska M, Paszynska E, Amaechi BT, Meyer F, Enax J, Limeback H. 2024. Clinical evidence of caries prevention by hydroxyapatite: an updated systematic review and meta-analysis.
https://doi.org/10.1016/j.jdent.2024.105429
Marinho VCC, Higgins J, Logan S, Sheiham A. 2003. Fluoride toothpastes for preventing dental caries in children and adolescents.
https://www.cochrane.org/evidence/CD002278_fluoride-toothpastes-preventing-dental-caries-children-and-adolescents
Alencar CM, et al. 2019. Clinical efficacy of nano-hydroxyapatite in dentin hypersensitivity.
https://pubmed.ncbi.nlm.nih.gov/30611773/
Limeback H, Meyer F, Enax J. 2023. Clinical Evidence of Biomimetic Hydroxyapatite in Oral Care Products for Reducing Dentin Hypersensitivity.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9844412/
Limeback H, Meyer F, Enax J. 2023. Tooth Whitening with Hydroxyapatite: A Systematic Review.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9955010/