calciumphosphate

Calcium phosphate refers to a family of inorganic compounds containing calcium ions and phosphate groups. They occur in several crystalline forms and solid solutions, with hydroxyapatite and other calcium phosphate minerals dominating biological and geological systems. The term is often used to describe compositions with the general formula Cax(PO4)y, including various hydrated and anhydrous phases.

Natural occurrence and biology: Calcium phosphate minerals are major components of bone and teeth. Hydroxyapatite, Ca5(PO4)3OH, is the principal mineral phase in bone mineral and tooth enamel, providing hardness and a scaffold for mineralization. Carbonate substitutions and substitutions of other ions frequently occur, affecting solubility and structure. In biology, calcium phosphate regulates mineral storage, bone remodeling, and dental remineralization.

Principal phases: Common calcium phosphates include monocalcium phosphate Ca(H2PO4)2; dicalcium phosphate CaHPO4 (anhydrous) or CaHPO4·2H2O (brushite, also called dicalcium phosphate dihydrate); tricalcium phosphate Ca3(PO4)2; octacalcium phosphate Ca8(HPO4)2(PO4)4·5H2O; and hydroxyapatite Ca5(PO4)3OH. Whitlockite (a magnesium-containing beta-Ca3(PO4)2) is another natural phase.

Properties and transformations: Solubility and stability are pH-dependent. Calcium phosphates can transform among phases; for example, brushite and other precursors can transform into hydroxyapatite under physiological conditions, influencing bioceramics and bone repair materials.

Uses: In medicine and dentistry, calcium phosphate materials serve as bone grafts, coatings for implants, and bone cements. In industry, they are used as food additives (calcium phosphate E-numbers) and in fertilizers, coatings, and ceramics.

Safety: Generally recognized as safe for specified uses, though inhalation of fines can irritate the respiratory tract; handling and exposure considerations vary by form and application.