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Diff: Hydroxyapatite

Comparing revision #1 (2023-12-30 04:00:04) with revision #2 (2026-06-22 14:37:00).

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(PO₄)₃(OH). It is the principal component of vertebrate hard tissues such as bones and teeth and is widely used in various medical and dental applications due to its biocompatibility and similarity to the mineral phase of bone.
==Structure and Composition==
Crystal Structure:

Hexagonal Structure: Hydroxyapatite has a hexagonal crystal structure, with calcium ions (Ca²⁺), phosphate ions (PO₄³⁻), and hydroxide ions (OH⁻) arranged in a repeating pattern.

Chemical Composition:

Calcium (Ca): Essential for bone and teeth mineralization, providing hardness and strength.

Phosphorus (P): Contributes to the structural integrity of hydroxyapatite.

Oxygen (O): Forms the backbone of the phosphate groups.

Hydroxide (OH): Part of the hydroxyapatite crystal lattice.
==Natural Occurrence==
Biological Mineralization: Hydroxyapatite is a major component of the mineralized tissues in the human body, including bones and teeth.

Bone Structure: In bones, hydroxyapatite crystals are deposited in a matrix of collagen fibres, providing strength and rigidity.
==Medical and Dental Applications==
Dental Implants:

Biocompatible Coating: Hydroxyapatite coatings on dental implants enhance osseointegration, promoting the fusion of the implant with the surrounding bone tissue.
	'''Hydroxyapatite''' is a calcium phosphate mineral with the formula Ca5(PO4)3(OH), often written as Ca10(PO4)6(OH)2 to show two formula units. It is the main mineral phase of human bone and tooth enamel, where it gives hardness and stiffness to otherwise organic tissues.

Bone Grafts:
	Hydroxyapatite is also called hydroxylapatite or calcium hydroxyphosphate.

Bone Repair: Hydroxyapatite is used in bone grafts and bone fillers to aid in the regeneration of bone tissue, particularly in orthopaedic and dental surgeries.
	== Structure and Chemistry ==
	Hydroxyapatite is made from calcium, phosphate, and hydroxide ions arranged in a crystalline lattice. In biological tissues, the mineral is not perfectly pure. Bone and enamel apatite can contain carbonate, magnesium, sodium, fluoride, and other substitutions that affect crystal size, solubility, and mechanical properties.

Biomaterials:
	In bone, hydroxyapatite crystals are embedded in a collagen-rich matrix. In tooth enamel, apatite crystals are packed far more densely, giving enamel its hardness.

Scaffolds for Tissue Engineering: Hydroxyapatite is utilized as a scaffold material in tissue engineering applications to support the growth and differentiation of cells.
	== Bone and Teeth ==
	More than 99 percent of the body's calcium is found in bones and teeth, mainly as calcium hydroxyapatite. Bone mineral provides compressive strength, while collagen provides toughness and flexibility.

Drug Delivery:
	Enamel is the hardest tissue in the human body and is highly mineralised. Dentine and bone contain more organic matrix and water, which makes them less hard but less brittle.

Carrier for Drug Delivery: Due to its porous structure, hydroxyapatite can be used as a carrier for drug delivery systems, gradually releasing therapeutic agents.
	== Medical and Dental Uses ==
	Synthetic hydroxyapatite is used or studied in:

Orthopaedic Coatings:
	* Bone graft substitutes and bone fillers.
	* Coatings for orthopaedic and dental implants.
	* Tissue engineering scaffolds.
	* Dental remineralisation products.
	* Desensitising and enamel-repair toothpaste formulations.

Coating for Orthopaedic Implants: Hydroxyapatite coatings on orthopaedic implants improve biocompatibility and enhance the integration of the implant with the host bone.
	Its appeal is that it resembles the mineral part of bone and teeth and can be biocompatible. Performance still depends on particle size, porosity, purity, manufacturing method, and the clinical use.

Dentistry:
	== Dental Remineralisation ==
	Nano-hydroxyapatite and related formulations are used in some toothpastes and dental products. Research suggests that hydroxyapatite can support remineralisation of early enamel lesions and may help with sensitivity in some settings.

Toothpaste and Dental Fillings: Hydroxyapatite is used in toothpaste formulations and dental fillings to promote remineralization and strengthen tooth enamel.
==Synthesis==
Biological Mineralization:
	It should not be treated as a replacement for basic dental prevention. Fluoride, sugar frequency, brushing technique, plaque control, saliva, and dental review remain important.

Biomineralization Process: In living organisms, hydroxyapatite is formed through a biologically controlled process, where cells regulate the precipitation of calcium and phosphate ions.
	== Synthesis ==
	Hydroxyapatite can be made by wet chemical precipitation, sol-gel methods, hydrothermal methods, and processing of biological materials. Medical-grade material needs control of composition, contamination, crystal size, and sterilisation.

Laboratory Synthesis:
	== See Also ==
	* [[Osteoporosis]]
	* [[Osteoarthritis]]
	* [[Common_Medical_Terms]]

Chemical Precipitation: Hydroxyapatite can be synthesized in the laboratory through chemical precipitation methods, involving the reaction of calcium and phosphate-containing precursors.
==Challenges and Considerations==
Biodegradability: While biocompatible, the biodegradability of synthetic hydroxyapatite is a subject of research, especially in the context of long-term implant applications.
	== References ==
	* [https://pubchem.ncbi.nlm.nih.gov/compound/57369541 PubChem: Calcium hydroxide phosphate]
	* [https://www.ncbi.nlm.nih.gov/books/NBK56060/ NCBI Bookshelf: Dietary Reference Intakes for calcium and vitamin D]
	* [https://www.ncbi.nlm.nih.gov/books/NBK513314/ NCBI Bookshelf: Hydroxyapatite dental material]
	* [https://pmc.ncbi.nlm.nih.gov/articles/PMC8930857/ BDJ Open: Hydroxyapatite toothpaste and dental caries]
	* [https://pmc.ncbi.nlm.nih.gov/articles/PMC9102186/ Dentistry Journal: Nano-hydroxyapatite and dental remineralisation]
	* [https://www.acs.org/molecule-of-the-week/archive/h/hydroxyapatite.html American Chemical Society: Hydroxyapatite]

Crystal Size and Purity: The properties of hydroxyapatite depend on factors such as crystal size, purity, and the presence of impurities.
==Research and Development==
Regenerative Medicine: Ongoing research explores the use of hydroxyapatite in regenerative medicine for applications such as bone tissue engineering and controlled drug delivery.
	[[Category:Biochemistry]]
	[[Category:Medicine]]