A report on Hydroxyapatite and Fluorapatite

Hydroxyapatite crystals on matrix
Hydroxyapatite
Fluorapatite grains in carbonate groundmass. Photomicrographs of thin section from Siilinjärvi apatite ore.
Needle-like hydroxyapatite crystals on stainless steel. Scanning electron microscope picture from University of Tartu.
Fluorapatite. São Geraldo do Baixio, Doce valley, Minas Gerais, Brazil.
Nanoscale coating of Ca-HAp, image taken with scanning probe microscope
A 3D visualization of half of a hydroxyapatite unit cell, from x-ray crystallography

The OH− ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite.

- Hydroxyapatite

Along with hydroxylapatite, it can be a component of tooth enamel, but for industrial use both minerals are mined in the form of phosphate rock, whose usual mineral composition is primarily fluorapatite but often with significant amounts of the other.

- Fluorapatite
Hydroxyapatite crystals on matrix

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Overall

Labeled molar

Tooth enamel

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One of the four major tissues that make up the tooth in humans and many other animals, including some species of fish.

One of the four major tissues that make up the tooth in humans and many other animals, including some species of fish.

Labeled molar
Parts of a tooth, including the enamel (cross section).
Histologic slide showing a developing tooth. The mouth would be in the area of space at the top of the picture.
Histologic slide showing enamel formation
The effects of bruxism on an anterior tooth, revealing the dentin and pulp which are normally hidden by enamel
Common dentistry trays filled with fluoride foam
An X-ray showing enamel and dentin replaced by an amalgam restoration
Irreversible enamel defects caused by an untreated celiac disease. They may be the only clue to its diagnosis, even in absence of gastrointestinal symptoms, but are often confused with fluorosis, tetracycline discoloration, or other causes. The National Institutes of Health include a dental exam in the diagnostic protocol of celiac disease.
Teeth of a rottweiler

The primary mineral is hydroxyapatite, which is a crystalline calcium phosphate.

The remineralized tooth surfaces contain fluoridated hydroxyapatite and fluorapatite, which resist acid attack much better than the original tooth did.

Fluoridation does not affect the appearance, taste or smell of drinking water.

Water fluoridation

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Controlled adjustment of fluoride to a public water supply solely to reduce tooth decay.

Controlled adjustment of fluoride to a public water supply solely to reduce tooth decay.

Fluoridation does not affect the appearance, taste or smell of drinking water.
A cavity starts in a tooth's outer enamel and spreads to the dentin and pulp inside.
Fluoride monitor (at left) in a community water tower pumphouse, Minnesota, 1987
Geographical areas associated with groundwater having over 1.5 mg/L of naturally occurring fluoride, which is above recommended levels.
Detail of southern Arizona. Areas in darker blues have groundwater with over 2 mg/L of naturally occurring fluoride.
A mild case of dental fluorosis, visible as white streaks on the subject's upper right central incisor.
Demineralization and remineralization of dental enamel in the presence of acid and fluoride in saliva and plaque fluid.
Fluoride toothpaste is effective against cavities. It is widely used, but less so among the poor.
Fluoridated iodized salt sold in Germany
1909 photograph by Frederick McKay of G.V. Black (left), Isaac Burton and F.Y. Wilson, studying the Colorado brown stain.
H. Trendley Dean set out in 1931 to study fluoride's harm, but by 1950 had demonstrated the cavity-prevention effects of small amounts.
Percentage of population receiving fluoridated water, including both artificial and natural fluoridation, as of 2012. 
80–100%
60–80%
40–60%
20–40%
1–20%
< 1%
unknown

When enough acid is produced to lower the pH below 5.5, the acid dissolves carbonated hydroxyapatite, the main component of tooth enamel, in a process known as demineralization.

When fluoride ions are present in plaque fluid along with dissolved hydroxyapatite, and the pH is higher than 4.5, a fluorapatite-like remineralized veneer is formed over the remaining surface of the enamel; this veneer is much more acid-resistant than the original hydroxyapatite, and is formed more quickly than ordinary remineralized enamel would be.

Fluorine 3D molecule

Fluorine

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Chemical element with the symbol F and atomic number 9.

Chemical element with the symbol F and atomic number 9.

Fluorine 3D molecule
Crystal structure of β-fluorine. Spheres indicate molecules that may assume any angle. Other molecules are constrained to planes.
Animation showing the crystal structure of beta-fluorine. Molecules on the faces of the unit cell have rotations constrained to a plane.
Steelmaking illustration from De re metallica
1887 drawing of Moissan's apparatus
An ampoule of uranium hexafluoride
Boiling points of hydrogen halides and chalcogenides, showing the unusually high values for hydrogen fluoride and water
Chlorine trifluoride, whose corrosive potential ignites asbestos, concrete, sand and other fire retardants
These xenon tetrafluoride crystals were photographed in 1962. The compound's synthesis, as with xenon hexafluoroplatinate, surprised many chemists.
Immiscible layers of colored water (top) and much denser perfluoroheptane (bottom) in a beaker; a goldfish and crab cannot penetrate the boundary; quarters rest at the bottom.
Chemical structure of Nafion, a fluoropolymer used in fuel cells and many other applications
Industrial fluorine cells at Preston
current transformers at a Russian railway.
Aluminium extraction depends critically on cryolite
Fluorosurfactant-treated fabrics are often hydrophobic
Topical fluoride treatment in Panama
Fluoxetine capsules
A full-body PET scan with glucose tagged with radioactive fluorine-18. The normal brain and kidneys take up enough glucose to be imaged. A malignant tumor is seen in the upper abdomen. Radioactive fluorine is seen in urine in the bladder.
The gifblaar is one of the few organofluorine-synthesizing organisms
Hydrofluoric acid burns may not be evident for a day, after which calcium treatments are less effective.
NASA projection of stratospheric ozone over North America without the Montreal Protocol
Perfluorooctanesulfonic acid, a key Scotchgard component until 2000
Fluorite: Pink globular mass with crystal facets
Fluorapatite: Long prism-like crystal, without luster, at an angle coming out of aggregate-like rock
Cryolite: A parallelogram-shaped outline with diatomic molecules arranged in two layers

Fluorite, fluorapatite and cryolite are the most industrially significant.

This was first attributed to the conversion of tooth enamel hydroxyapatite into the more durable fluorapatite, but studies on pre-fluoridated teeth refuted this hypothesis, and current theories involve fluoride aiding enamel growth in small caries.

Toothpaste from a tube being applied to a toothbrush

Toothpaste

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Paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth.

Paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth.

Toothpaste from a tube being applied to a toothbrush
Toothpaste is sold in many brands.
Icelandic postage stamp encouraging use of fluoridated toothpaste
A brand of red, blue and white striped toothpaste
The red area represents the material used for stripes, and the rest is the main toothpaste material. The two materials are not in separate compartments; they are sufficiently viscous that they will not mix. Applying pressure to the tube causes the main material to issue out through the pipe. Simultaneously, some of the pressure is forwarded to the stripe-material, which is thereby pressed onto the main material through holes in the pipe.
Promotional poster for the Kolynos toothpaste from the 1940s
Modern toothpaste gel, in a tube

Representative abrasives include particles of aluminum hydroxide (Al(OH)3), calcium carbonate (CaCO3), magnesium carbonate(MgCo3), sodium bicarbonate, various calcium hydrogen phosphates, various silicas and zeolites, and hydroxyapatite (Ca5(PO4)3OH).

The "biomimetic hydroxylapatite" is intended to protect the teeth by creating a new layer of synthetic enamel around the tooth instead of hardening the existing layer with fluoride that chemically changes it into fluorapatite.

Apatite

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Faceted blue apatite, Brazil
Apatite in photomicrographs of a thin section from the Siilinjärvi apatite mine. In cross-polarized light on left, plane-polarized light on right.
An apatite mine in Siilinjärvi, Finland.

Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal.