Hydroxyapatite crystal matrix (HA or HAp)

Hydroxyapatite crystal matrix is the principal inorganic component of bones and teeth, conferring rigidity and structural strength. Its chemical composition is calcium phosphate, Ca₁₀(PO₄)₆(OH)₂, forming nanoscale plate or needle-like crystals, frequently organized along type I collagen fibers. This matrix provides mechanical support and acts as a calcium and phosphate reservoir. Hydroxyapatite in bone is often defective or carbonated, differing from synthetic, stoichiometric hydroxyapatite. In bone regeneration therapies, synthetic or natural hydroxyapatite is used as a scaffold to promote new bone growth. Pathologically, hydroxyapatite crystals can accumulate in certain diseases, such as calcific tendonitis or tumors. While the hydroxyapatite matrix itself is not a therapeutic target, it is critical in understanding bone physiology, pathology, and therapeutic interventions.

Other names

Hydroxyapatite matrixBone mineralApatitic bone mineralCarbonated hydroxyapatite

Adsorption to crystal surface (bisphosphonates attach to hydroxyapatite, preventing osteoclast-mediated dissolution); Incorporation as scaffold/material in bone regeneration therapies