Fluoridated hydroxyapatite (FHA) (FHA)

Fluoridated hydroxyapatite is a chemically modified form of the primary mineral component of human tooth enamel, hydroxyapatite [National Institute of Dental and Craniofacial Research (NIDCR)]. It is formed when fluoride ions substitute for hydroxyl ions within the hexagonal crystal lattice, resulting in a more stable and acid-resistant structure known as fluorapatite or fluorhydroxyapatite [StatPearls, Fluoride]. This transformation is a central mechanism in preventive dentistry, as fluoridated hydroxyapatite has a lower critical pH of approximately 4.5 compared to pure hydroxyapatite's 5.5 [PubChem, Fluorapatite]. Consequently, teeth become significantly more resistant to demineralization caused by organic acids from cariogenic bacteria [Journal of Dental Research, Featherstone J.D.]. Beyond structural reinforcement, the presence of fluoride in the oral environment promotes the remineralization of early carious lesions by attracting calcium and phosphate ions back into the enamel matrix [NIH, Fluoride in Diet]. Therapeutic interventions using various fluoride salts, such as sodium fluoride or stannous fluoride, aim to facilitate this conversion to protect against dental caries and erosion [StatPearls, Fluoride]. However, excessive systemic exposure during tooth development can lead to dental fluorosis, highlighting the need for controlled application [StatPearls, Fluoride Toxicity].

Other names

FluorapatiteFluorhydroxyapatiteFluoridated enamelFApFluoridated hydroxyapatite

Fluoride ions substitute for hydroxyl groups in the hydroxyapatite crystal lattice, creating a more stable mineral phase with a lower solubility product. This process increases resistance to acid-induced demineralization and promotes the deposition of calcium and phosphate from saliva into the enamel structure.