Hydroxyapatits

Hydroxyapatite is a calcium phosphate mineral with the chemical formula Ca10(PO4)6(OH)2. It is the principal inorganic component of bone and teeth, where it occurs as a nanocrystalline, carbonated phase embedded in a collagen-rich organic matrix. In nature, the mineral is often non-stoichiometric and can accommodate substitutions such as carbonate, fluoride, and chloride, which influence its stability and solubility.

Biological hydroxyapatite resembles a highly organized apatitic lattice that contributes to the stiffness and mineral storage of bone. Carbonate-containing apatite is more common in vivo and differs from the ideal, synthetic hydroxyapatite used in many applications. The material is biocompatible and has a strong affinity for bone, contributing to its osteoconductive properties.

Synthesis of hydroxyapatite can be achieved through several methods, including wet chemical precipitation, hydrothermal synthesis, and sol-gel processes. Synthetic hydroxyapatite can be produced with controlled particle size, porosity, and crystallinity to tailor biological responses and mechanical characteristics.

Applications of hydroxyapatite include use as a bone graft substitute, a coating for metal implants to improve osseointegration, and scaffolds in bone tissue engineering. It is also employed in dentistry for remineralization and as a component in drug delivery systems. While biocompatible and bioactive, hydroxyapatite ceramics are relatively brittle, and resorption rates can vary with crystallinity and substitutions, influencing their long-term behavior in the body.