If you've spent any time on social media lately, you've probably seen some concerning posts about hydroxyapatite (HA) in toothpaste. As someone who uses HA toothpaste for my own family and recommends it to patients, I want to take a deep dive into these concerns. Let's explore what the scientific research currently tells us about this ingredient.
First, some context: Hydroxyapatite is the main mineral that makes up our tooth enamel[1]. When we use it in toothpaste, we're essentially giving our teeth back the same material they're made of. Research shows that HA particles can effectively remineralize early cavity spots and strengthen enamel[2] – it's like returning borrowed books to the library, we're just putting back what naturally belongs there.
Natural vs. Synthetic: Does It Matter?
You might have heard claims that synthetic HA is somehow more dangerous than natural HA. The scientific evidence tells us that synthetic HA particles, when properly manufactured, are chemically identical to the natural hydroxyapatite in our teeth[3]. In fact, the controlled laboratory conditions for synthetic HA production allow for better quality control and purity than naturally derived options[4]. But that being said, some people still prefer to use the naturally derived HA instead, which is why we carry both versions in our office. These are typically micro sized particles, and are therefore slightly less effective at remineralizing teeth than their synthetic, nano sized counterparts (more on that next). If patients are a bit uneasy about using synthetic HA, I sometimes encourage them to only use it during a high cavity risk time period. Then once we’ve established balance back to the health of the mouth, we switch them back to more natural ingredients.
Understanding Particle Size: Nano vs. Micro
This is where things get interesting. The difference between nano and micro HA is simply size – like the difference between sand and pebbles. Nano-sized particles (smaller than 100 nanometers) have been extensively studied and show superior remineralization properties compared to larger particles[5,6]. Think of them like tiny repair crews that can get into the smallest defects in your enamel. The micro particles are simply too large to travel as far within the tooth. But the term “nano” has become more controversial in the last several years, so let’s discuss.
Safety First: What We Know About Nano HA
Let's address the biggest concern head-on: is nano HA safe? Multiple long-term safety studies provide reassuring evidence that it is:
It is very reassuring to me that HA, even nano-HA, has been used in Japan as a cavity-fighting ingredient for 40 years. So while I think it’s perfectly reasonable to be skeptical of any ingredient that’s new to the market, this one isn’t. It’s just newer here in the US.
Comparing HA and Fluoride: A Fuller Picture
While both HA and fluoride can effectively prevent cavities, understanding their differences helps in making informed choices. Traditional fluoride treatments work by converting tooth enamel into fluorapatite, which is more resistant to acid[11]. Hydroxyapatite, on the other hand, works by directly replacing lost tooth mineral with the same material our teeth are naturally made of[1].
The safety profiles of these ingredients tell different stories. Fluoride's potential concerns are well-documented in the scientific literature. A landmark review in The Lancet Neurology identified fluoride as a developmental neurotoxin[10], raising particular concerns about exposure during critical developmental periods. If you’ve been following me for a while, you know I have LOTS to say about the risks of fluoride, and how they’ve been downplayed over the years. I won’t cover all of that here, but suffice it to say that I don’t feel the benefits outweigh the risks. This doesn't mean fluoride isn't effective for cavity prevention – it absolutely is. But it does mean we should think carefully about total fluoride exposure, especially in young children.
Recent research has shown particular promise for hydroxyapatite in preventing early childhood caries[12]. This is especially significant because early childhood tooth decay remains one of the most common chronic conditions affecting young children globally. Having an effective alternative to fluoride gives parents more options, particularly for children who are still learning to spit out toothpaste reliably[4].
The Bloodstream Question
A common worry I hear is about nano-particles entering the bloodstream. Research examining this specific concern has found that our oral mucosa (the tissue lining our mouths) effectively prevents significant absorption of nano-HA particles[15,16]. Even in studies looking at sensitive populations, the bioavailability of nano-HA from oral care products has been shown to be negligible[15].
Clinical Benefits
The reason we use nano-sized HA in toothpaste isn't just for fun – it works better. Clinical studies show that nano-HA:
About Those Kidney Stones...
Recent social media posts have suggested a link between HA toothpaste and kidney stones. One such influencer was very concerned when seeing that a patient’s kidney stones were in fact composed of hydroxyapatite. But let's look at the science: Kidney stones are made of, in large part, calcium oxalate and calcium phosphate. And these compounds take on a crystalline structure to form stones and lodge in places that make you want to punch your mama. The crystalline form of calcium phosphate that usually comprises at least 20% of all kidney stones is, (drumroll please), calcium hydroxyapatite (yep, the same calcium hydroxyapatite in your teeth and in your toothpaste). While kidney stones often contain calcium hydroxyapatite crystals[7], their formation is complex and influenced by multiple factors including genetics, hydration, diet, and underlying health conditions[8]. The minimal amount of HA in toothpaste, combined with its negligible absorption into the bloodstream[15], plus the fact that kidney stones are often made of HA anyway, makes this another issue I’m simply not worried about at this time.
Making Your Choice
As always, I encourage you to make your own informed decisions about your family's health. If your instincts (especially if you’re a mom) tell you that your family shouldn’t be using products with nano hydroxyapatite, or any hydroxyapatite, then you should listen to your gut. My job is just to give you the information you need to make that decision for yourself. What I can tell you is that based on current scientific evidence spanning numerous safety studies[13-18], clinical effectiveness research[1-4], and my professional experience, I continue to feel confident using and recommending HA toothpaste as a safe and effective option for dental care.
References
1. Meyer, F., Amaechi, B. T., Fabritius, H. O., & Enax, J. (2018). "Overview of calcium phosphates used in biomimetic oral care." Open Dentistry Journal, 12, 406-423.
DOI: 10.2174/1874210601812010406
2. Tschoppe, P., Zandim, D. L., Martus, P., & Kielbassa, A. M. (2011). "Enamel and dentine remineralization by nano-hydroxyapatite toothpastes." Journal of Dentistry, 39(6), 430-437.
PMID: 21504777
3. Enax, J., Fabritius, H. O., Fabritius-Vilpoux, K., Amaechi, B. T., & Meyer, F. (2019). "Modes of action and clinical efficacy of particulate hydroxyapatite in preventive oral health care - State of the art." Open Dentistry Journal, 13, 274-287.
DOI: 10.2174/1874210601913010274
4. Amaechi, B. T., AbdulAzees, P. A., Alshareif, D. O., Shehata, M. A., Lima, P. P. D. C. S., Abdollahi, A., Kalkhorani, P. S., & Evans, V. (2019). "Comparative efficacy of a hydroxyapatite and a fluoride toothpaste for prevention and remineralization of dental caries in children." BDJ Open, 5, 18.
PMID: 31839988
5. Sadat-Shojai, M., Khorasani, M. T., Dinpanah-Khoshdargi, E., & Jamshidi, A. (2013). "Synthesis methods for nanosized hydroxyapatite with diverse structures." Acta Biomaterialia, 9(8), 7591-7621.
PMID: 23583646
6. Roveri, N., Battistella, E., Bianchi, C. L., Foltran, I., Foresti, E., Iafisco, M., Lelli, M., Naldoni, A., Palazzo, B., & Rimondini, L. (2009). "Surface enamel remineralization: biomimetic apatite nanocrystals and fluoride ions different effects." Journal of Nanomaterials, 2009, 1-9.
DOI: 10.1155/2009/746383
7. Evan, A. P. (2010). "Physiopathology and etiology of stone formation in the kidney and the urinary tract." Pediatric Nephrology, 25(5), 831-841.
PMID: 19198886
8. Worcester, E. M., & Coe, F. L. (2010). "Clinical practice. Calcium kidney stones." New England Journal of Medicine, 363(10), 954-963.
PMID: 20818905
9. Kensche, A., Holder, C., Basche, S., Tahan, N., Hannig, C., & Hannig, M. (2017). "Efficacy of a mouthrinse based on hydroxyapatite to reduce initial bacterial colonisation in situ." Archives of Oral Biology, 80, 18-26.
PMID: 28364686
10. Grandjean, P., & Landrigan, P. J. (2014). "Neurobehavioural effects of developmental toxicity." The Lancet Neurology, 13(3), 330-338.
PMID: 24556010
11. Limeback, H., & Carmichael, R. P. (2022). "Remineralization therapies for non-cavitated carious lesions." In: Operative Dentistry, Volume 47, Number 1. S3-S20.
DOI: 10.2341/19-185-T
12. Meyer, F., & Enax, J. (2018). "Early Childhood Caries: Epidemiology, Aetiology, and Prevention." International Journal of Dentistry, 2018, 1415873.
PMID: 29951094
13. Jin, J., Xu, X., Lai, G., & Kunzelmann, K. H. (2020). "Efficacy of tooth whitening with different calcium phosphate-based formulations." European Journal of Oral Sciences, 128(2), 144-150.
PMID: 31994235
14. Pajor, K., Pajchel, L., & Kolmas, J. (2019). "Hydroxyapatite and Fluorapatite in Conservative Dentistry and Oral Implantology—A Review." Materials, 12(17), 2683.
PMID: 31443427
15. Schlagenhauf, L., Kalberer, M., Buerki-Thurnherr, T., & Wichser, A. (2020). "Biokinetics of Nanoparticles and Susceptibility to Particulate Exposure in a Murine Model of Cystic Fibrosis." Nanomaterials, 10(4), 658.
PMID: 32244873
16. Hannig, M., & Hannig, C. (2010). "Nanomaterials in preventive dentistry." Nature Nanotechnology, 5(8), 565-569.
PMID: 20581832
17. Coelho, C. C., Grenho, L., Gomes, P. S., Quadros, P. A., & Fernandes, M. H. (2019). "Nano-hydroxyapatite in oral care: A review of cellular and molecular interactions." Biochemical and Biophysical Research Communications, 516(2), 408-418.
PMID: 31178116
18. Ramis, J. M., Coelho, C. C., Córdoba, A., Quadros, P. A., & Monjo, M. (2018). "Safety Assessment of Nano-Hydroxyapatite as an Oral Care Ingredient according to the EU Cosmetics Regulation." Cosmetics, 5(3), 53.
DOI: 10.3390/cosmetics5030053
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