Hydroxyapatite crystal of tooth enamel stabilized by fluoride incorporation

The *hydroxyapatite crystal structure of tooth enamel* is a highly organized, hexagonal calcium phosphate mineral that constitutes approximately 96–97% of tooth enamel by weight[5][4]. The integrity and dissolution resistance of enamel are greatly enhanced by the **incorporation of fluoride ions**, which replace hydroxide ions in the hydroxyapatite lattice to form fluorapatite[5][1][3]. This produces a more compact and less soluble crystal, resisting acid demineralization and dental caries[5][1][3][6]. Both fluoride treatments and biomimetic hydroxyapatite agents are used to promote remineralization, repair enamel microdefects, and prevent or treat hypomineralization-related dental diseases[2][4]. Excess fluoride during development can result in abnormal crystal formation and dental fluorosis[6]. Note: The entity described is a physical structure/process (enamel crystal and its stabilization by chemical incorporation), not a receptor or traditional drug target, and should be referenced as "Hydroxyapatite (tooth enamel)" or "Fluorapatite (tooth enamel)" with clarification as to form.

Other names

Hydroxyapatite (enamel)Fluorapatite (enamel)Tooth enamel mineralEnamel crystallite

Fluoride ions substitute for hydroxide ions in hydroxyapatite, forming fluorapatite and thereby decreasing enamel solubility and increasing acid resistance[5][1][3]. Hydroxyapatite particles in toothpaste physically deposit and integrate with enamel, restoring lost mineral and filling microscale defects[2][4].