Bioapatit

Bioapatit refers to the biological form of the mineral apatite that makes up the mineral phase of vertebrate bone and teeth. It is typically calcium phosphate mineral closely related to hydroxyapatite (Ca10(PO4)6(OH)2), but in living tissues it is often non-stoichiometric and carbonate-substituted, and it forms as nanocrystalline crystals embedded in a collagen matrix.

In terms of composition and structure, bioapatite is generally described as Ca10(PO4)6(OH)2 with substitutions such as carbonate for phosphate or hydroxide, and trace ions like sodium, magnesium, and fluoride. The crystals are small and poorly crystalline compared with purified synthetic hydroxyapatite, and the calcium-to-phosphate ratio can vary around 1.5 to 1.7. These substitutions influence solubility and resorbability.

Biological formation occurs through cellular processes in which osteoblasts lay down a collagen scaffold that becomes mineralized by matrix vesicles and mineral ions. The resulting mineral provides stiffness and hardness to bone and teeth, while ongoing remodeling by osteoclasts and osteoblasts adjusts structure and composition over time. The carbonate content and crystallinity of bioapatite affect its bioactivity and how readily it is remodeled.

Occurrence and variation are seen across mineralized tissues, including cortical and trabecular bone, dentin, and cementum. Enamel is highly mineralized with a distinct composition, but the mineral phase is related to bioapatite. In biomedical contexts, synthetic or processed carbonated apatites are used as bone graft substitutes, coatings for implants, and components in dental and orthopedic materials due to their biocompatibility and osteoconductivity.