Why Nanohydroxyapatite?
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.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.
Fluoride and hydroxyapatite utilize different mechanisms to oppose enamel degradation.
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.
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.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 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 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.
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.
“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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