Hydroxyapatite for remineralizing teeth — has it been proven safe?

There is a surge of new toothpastes and toothpowders on the market that promote the use of Hydroxyapatite (HAP) or Nano-hydroxyapatite (nHAP) as the latest and greatest remineralizer and enamelizer. Some studies have shown promising results for remineralizing teeth and reducing caries using nHAP. But is it natural? And has it been proven safe?

What is Hydroxyapatite? 

Hydroxyapatite (HAP) is a crystalline form of Calcium Phosphate (also known as Calcium Apatite). It is the form made by our bodies, to produce teeth and bones. Teeth are comprised of 97% Hydroxyapatite (HAP) and only about 1.5% proteins (mainly collagen), and 1.5% water.

Is it natural?

Well, that all depends on which form we are talking about. Hydroxyapatite (HAP) is indeed a natural form of Calcium and Phosphorus typically from animal bones or other natural elements. However, Nano-hydroxyapatite (nHAP) is a synthetic nano particle and definitely NOT NATURAL. It is a biomimetric version made in a lab out of synthetic calcium and synthetic phosphorus.

Nano-hydroxyapatite was used by NASA in the 1970s as a medical application for astronauts that had severely demineralized teeth and bones. The patent was later acquired by a Japanese company that starting using it in toothpaste. nHAP protects the teeth with the creation of a new layer of synthetic enamel around the tooth.

Unfortunately many news sources (like CNN), social media and even oral care brand websites talk about the effectiveness and safety of “Hydroxyapatite” but they don’t delineate between natural forms and synthetic nanoparticle forms. This poses a problem for consumers that want to avoid potentially harmful synthetic ingredients.

In addition, many toothpaste brands that use natural Hydroxyapatite in their formulas link to studies that show the effectiveness of synthetic Nano-hydroxyapatite, not the natural forms. So claims of "natural Hydroxyapatite" being "clinically proven" are misleading.

Are natural forms of Hydroxyapatite (HAP) safe? 

The purity, source, extraction method and particle size are important. Natural HAP is extracted from animal bones, fish, shells, some plants and minerals (eg. limestone). Some natural sources of HAP may contain trace minerals and additional macro minerals (which is ideal). The processing (which depends on the source) varies widely and can impact purity (eg heavy metals). In its natural state it has low solubility and is not well absorbed or utilized, but micronized HAP has better absorption in the mouth. For more information on natural hydroxyapatite, this article looks at Syntheses of hydroxyapatite from natural sources and compares sources, mineral ratios, bioavailability, uses and extraction methods. 

EWG rates natural Hydroxyapatite as safe  (listing "phosphate rock" as the source). If you use a toothpaste or toothpowder with natural hydroxyapatite make sure to check the source and extraction methods.

Is synthetic Nano-hydroxyapatite (nHAP) safe?

The science regarding safety is inconclusive and it has not been proven safe. Below are summaries from a handful of studies.

• This meta-study (study of studies) from October 2018, titled Opinion of the Scientific Committee on Consumer Safety (SCCS) - Revision of the Opinion on hydroxyapatite (nano) in cosmetic products stated: 

• A Study in Nature in 2019 attempted to prove its safety again as a rebuttal to SCSS’s 2018 review (above). The studies that this one in Nature suggesting that nHAP is safe have only been in vitro (in test tubes) and only up to a 3 hour period. They have not considered use over time (years), everyday, and how it might affect the entire body.

• The SCCS issued a Final Opinion dated March 31, 2021 with the same conclusions from its 2018 meta study: 

• Earlier this year, based on findings by the SCCS, the European Union announced that it plans to ban several nano-sized materials (including Nano-hydroxyapatite ) for use in cosmetic and oral hygiene applications. The EU’s hesitancy seems warranted for other reasons, too, since some studies suggest that nHAP may cause cellular breakdown in kidney cells and potentially have a negative impact on human blood cells.

• Furthermore, science still does not understand how nano particles in general impact the body. In January of 2021, the NIH released this study: Safe Nanoparticles Are We There Yet? Which states:

“Despite considerable efforts to understand the toxicity and safety of these nanoparticles, many of these questions are not yet fully answered.”

How does Nano-hydroxyapatite compare to natural sources of minerals (containing calcium and phosphorus) that support remineralizing teeth?

According to this study, Remineralization Effect of Eggshell versus Nano-hydroxyapatite on Caries-like Lesions in Permanent Teeth (In Vitro), there appeared to be no difference in remineralization between Eggshells (naturally high in calcium and phosphorous and other nutrients) and nHAP: 

“Eggshell (ES) is a rich source of minerals since it contains calcium, phosphorous, magnesium, strontium, and fluoride. This study sought to compare the efficacy of nano-hydroxyapatite (NHA) and ES for remineralization of enamel caries-like lesions by pH cycling. Microhardness significantly decreased in all samples after demineralization and significantly increased after exposure to therapeutic solutions. Microhardness of the samples was not significantly different among the therapeutic groups after pH cycling.”

In summary, and in our opinion: 

• Use of Nano-hydroxyapatite in oral care products has not been proven safe.
  
  
• nHAP is a synthetic, man made nanoparticle and NOT the same as natural hydroxyapatite. Often both are referred to as "Hydroxyapatite", creating widespread confusion. 
  
  
• Natural hydroxyapatite is OK and can be a good source of Calcium and Phosphorus, but it may not have all of the supporting minerals you need to support remineralization (keep in mind, calcium needs magnesium to work) and it is a highly processed mineral.
  
  
• You don’t need nHAP or HAP for remineralization to occur. There are many 100% natural sources of high quality, highly absorbable (naturally occurring) macro and trace minerals like non-irradiated raw clays, fulvic acid, or even eggshells that provide the necessary minerals to aide in tooth remineralization.
  
  
• If someone was severely demineralized it might make sense to have a medical application of nHAP (just like the astronauts).

We follow the precautionary principle. If any ingredient has the potential for harm, we don’t use it. We use only 100% natural ingredients that are minimally processed from plants and the earth that are good enough to eat and are proven to improve health. 

As we see it, Nature is the answer.

Learn more about our natural, safe and effective Oral Care Products that promote overall health and support remineralization, naturally.