Hydroxyapatite

General
Category	Phosphate mineral
Formula	Ca5(PO4)3(OH)
IMA symbol
Strunz classification
Dana classification
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Crystal class
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Unit cell

Hydroxyapatite (HA) is a naturally occurring mineral form of calcium apatite with the formula Ca₅(PO₄)₃(OH). It is the main inorganic component of bone and tooth enamel, making it a critical material in biomedical applications.

Structure and Properties

Hydroxyapatite is a member of the apatite group, characterized by its hexagonal crystal structure. It is a calcium phosphate mineral with a high degree of crystallinity, which contributes to its hardness and stability. The chemical structure of hydroxyapatite is similar to that of the mineral component of bones and teeth, which is why it is often used in medical applications.

Applications in Medicine

Hydroxyapatite is widely used in the field of orthopedics and dentistry due to its biocompatibility and osteoconductivity. It serves as a scaffold for bone growth and is used in:

• Bone grafts: HA is used as a bone substitute material in bone grafting procedures. It supports the growth of new bone by providing a framework that mimics the mineral phase of bone.
• Dental applications: In dentistry, hydroxyapatite is used in toothpaste formulations to help remineralize enamel and reduce sensitivity. It is also used in dental implants and coatings to improve osseointegration.
• Coatings for implants: HA coatings are applied to metal implants to enhance their integration with bone tissue. This is particularly important in joint replacement surgeries.

Research and Development

Ongoing research is focused on improving the properties of hydroxyapatite for various applications. This includes the development of nano-sized hydroxyapatite particles, which have shown promise in enhancing the mechanical properties and bioactivity of composite materials.

Also see

• Bone grafting
• Dental implant
• Biomaterials
• Calcium phosphate

Gallery

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  Hydroxyapatite crystals
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  Hydroxyapatite crystal structure
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  Nanoscale coating of calcium hydroxyapatite