The mounting data on the ill effects of fluoride use have led some to avoid it, but these people may not be aware of a promising new alternative that does what even fluoride can’t.
Multiple studies have demonstrated nano preparations of hydroxyapatite can regenerate decayed tooth enamel and help repair dentin within teeth. And it makes sense since hydroxyapatite is the primary mineral making up your tooth enamel, dentin, and cementum.
Dental erosion is caused by the chemical destruction of the hard tissue that constitutes teeth. A prevalent source of dental erosion is consumption of sugary, acidic beverages such as soft drinks or fruit juice.
“The mechanisms involved in the damage of dental hard tissue are the acid attacks on the outer few micrometers of the enamel,” states a 2009 Journal of Nanomaterials study. These attacks demineralize and dissolve the minerals in our teeth, it explains.
Hydroxyapatite is a naturally occurring mineral composed of calcium and phosphate ions and is the primary component of tooth enamel, comprising about 97 percent of it by weight.
One of the main determinants of tooth erosion is the solubility of hydroxyapatite, how readily it is dissolved by substances in the mouth; “all calcium phosphates including [hydroxyapatite] … are soluble in acids, i.e., the enamel surface can be attacked by acids and be partially dissolved,” according to a 2018 review in The Open Dentistry Journal.
Fluoride and hydroxyapatite utilize different mechanisms to oppose enamel degradation.
“Fluoride ions generate a surface modification of the natural enamel apatite crystals increasing their crystallinity degree and relative mechanical and acid resistance,” to halt the chemical erosion of apatite from teeth, notes the Journal of Nanomaterials study.
Fluoride modifies the natural mineral composition and degree of crystallinity of teeth while, “on the other hand, the remineralization produced by carbonate-hydroxyapatite consists in a deposition of a new apatitic mineral into the eroded enamel surface scratches,” it continues.
Nanoparticulate hydroxyapatite acts as a reservoir of the naturally occurring calcium and phosphate minerals of teeth, helping to maintain the availability of a saturating amount of these ions for teeth adsorption.
In a 2014 research review published in the Journal of Odontostomatologic Sciences, researchers explain, “This ability is due to the size of nanoparticles, which considerably increase the surface area to which proteins can bind. Besides, nanohydroxyapatite also acts as filler because it repairs small holes and depressions on enamel surface, a function enhanced by the small size of the particles that compose it.”
The similarities between nanohydroxyapatite and the minerals native to teeth make nanohydroxyapatite highly biologically compatible as well as nontoxic. Multiple studies demonstrate nanohydroxyapatite heals lesions in tooth enamel.
Evidence of Nanohydroxyapatite Improving Tooth Health
Though reversible, dental cavities are unique among diseases as teeth have no available cellular repair mechanism because the outer layer of teeth, the enamel, consists of neither cells nor blood vessels. In that sense, it’s like fingernails.
“Nonetheless, it is now well established that the formation of incipient enamel caries is a reversible process where periods of progression alternates with periods of remineralization. Given an appropriate change in conditions, remineralization may even become the predominant process, leading to apparent repair of the lesion,” relates a 2009 study in the journal Biomedical Materials.
The study goes on to evaluate how readily different nanohydroxyapatite concentrations were able to induce the remineralization of teeth.
Extracted bovine incisors were incubated in an acidic solution for 72 hours to artificially create caries. This was followed by treatment with one, five, 10, or 15 percent weight nanohydroxyapatite solutions whose acidity was dynamically tailored to resemble the oral environment one experiences daily.
The researchers analyzed surface hardness of the teeth before and after each step of the experiment to determine the recovery of the enamel, represented by a recovery of surface hardness of the teeth.
They found all concentrations of nanohydroxyapatite produced significant recovery of surface hardness proportionate to the nanohydroxyapatite content of the treatment, up to 10 percent.
Solutions of 10 and 15 percent treatments produced no difference in enamel remineralization from which the authors concluded, “a suspension of 10 percent nano-hydroxyapatite appeared to be the optimal concentration for remineralization of early enamel caries. Nano-hydroxyapatite of proper concentration could therefore be beneficial in promoting remineralization with regular daily usage.”
A similar experiment with a similar outcome was published in 2011 in Scientific Research and Essays, in which extracted teeth were immersed for a meager 5 minutes in beer to reduce their surface hardness. After this exposure, the teeth were exposed to either a 10 percent nanohydroxyapatite solution or drinking water.
A significant increase in surface hardness was induced by the nanohydroxyapatite treatment while a further reduction, though not statistically significant, was observed after drinking water exposure.
The researchers observed, “according to the results of the present study, it can be concluded that [nanohydroxyapatite] solution has the potential to remineralise enamel erosive lesions caused by exposure to soft beer beverage.”
Dentin makes up the bulk of a tooth and is the calcified layer under the enamel and surrounding the pulp which harbors blood vessels and nerves.
Microscopic channels, called dentin tubules, run through the dentin, from the pulp to the enamel, and carry nutrients and fluid throughout the dentin. Enamel erosion can cause exposure of dentin and dentin tubules which can result in dental hypersensitivity which is, “a sensation characterized by distinctive short, sharp pain arising from exposed cervical dentin in response to various external stimuli that are typically thermal, evaporative, tactile, electrical, osmotic, or chemical … when dentin becomes exposed and ‘trigger’ stimuli occur, the fluid in the tubule moves rapidly, resulting in stimulation of the pulp nerves, causing short, sharp pain,” according to a report in the American Journal of Dentistry.
Dentin is comprised of approximately 75 percent hydroxyapatite by weight; thus, dental researchers investigated the ability of nanohydroxyapatite treatments to close the exposed ends of dentin tubules in order to eliminate hypersensitivity.
In the American Journal of Dentistry study, researchers compared toothpastes containing 10 and 15 percent nanohydroxyapatite to a standard fluoride-containing toothpaste, Colgate Regular, in biologically relevant conditions.
After both 14 and 28 toothpaste uses, the percentage of partially or completely occluded (closed) dentin tubules was significantly greater with both 10 and 15 percent nanohydroxyapatite toothpastes than the standard fluoride toothpaste, and the mineral layer deposited by the nanohydroxyapatite toothpastes was significantly thicker than that left by the standard toothpaste.
Importantly, this same study assessed dentin tubule permeability by the ability of a dye to penetrate into the extracted dentin grafts.
It was found that both nanohydroxyapatite toothpastes significantly inhibited dye penetration into the dentin and that the standard fluoride toothpaste did not.
“The result of this study demonstrated that [nanohydroxyapatite]-containing toothpastes showed … effectiveness in occluding dentin tubules as well as depositing precipitate layers over and within dentin tubules, while standard fluoride toothpaste … were not effective in either respect,” the researchers reported.
Researchers reported similar findings in the Journal of Dentistry.
“Different nano-hydroxyapatite toothpastes exert similar capacities to remineralize enamel and dentine subsurface lesions. Furthermore, the fluoride toothpaste displayed the lowest remineralizing effects on both hard tissues [dentin and enamel], along with an increase in lesion depths.”
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- Meyer, F., Amaechi, B. T., Fabritius, H.-O. & Enax, J. Overview of Calcium Phosphates used in Biomimetic Oral Care. Open Dent. J. 12, 406–423 (2018).
- Pepla, E. Nano-hydroxyapatite and its applications in preventive, restorative and regenerative dentistry: a review of literature. Ann. Stomatol. (Roma). 108–114 (2014) doi:10.11138/ads/2014.5.3.108.
- Huang, S. B., Gao, S. S. & Yu, H. Y. Effect of nano-hydroxyapatite concentration on remineralization of initial enamel lesion in vitro. Biomed. Mater. 4, 0–5 (2009).
- Haghgoo, R., Abbasi, F. & Rezvani, M. B. Evaluation of the effect of nanohydroxyapatite on erosive lesions of the enamel of permanent teeth following exposure to soft beer in vitro. Sci. Res. Essays 6, 5933–5936 (2011).
- Amaechi, B. T., Mathews, S. M., Ramalingam, K. & Mensinkai, P. K. Evaluation of Nanohydroxyapatite-Containing Toothpaste for Occluding Dentin Tubules. Am. J. Dent. 28, 33–39 (2015).
- Tschoppe, P., Zandim, D. L., Martus, P. & Kielbassa, A. M. Enamel and dentine remineralization by nano-hydroxyapatite toothpastes. J. Dent. 39, 430–437 (2011).