AMTN (amelotin) is a secreted calcium-binding phosphoprotein that functions as a critical promoter of hydroxyapatite mineralization during dental enamel formation 1. Expressed predominantly during the maturation stage of amelogenesis, AMTN localizes at the interface between the enamel surface and ameloblasts 1. Mechanistically, AMTN directly promotes hydroxyapatite precipitation through a phosphorylation-dependent mechanism involving the SSEEL motif; this serine phosphorylation is essential for mineralizing function, with the phosphorylated form ((P)S(P)SEEL) being necessary for biomineralization activity 1. AMTN regulates hydroxyapatite crystal nucleation and growth, promoting formation of the compact, mineralized aprismatic enamel surface layer 2. Loss-of-function variants in AMTN are associated with amelogenesis imperfecta 3B, characterized by reduced enamel thickness and mineralization; knockout mice exhibit hypomineralized enamel, while overexpression produces compact but disorganized enamel microstructure 12. Beyond enamel development, AMTN expression is upregulated in inflamed gingiva by proinflammatory cytokines (IL-1β, IL-6, TNF-α) through NF-κB signaling, suggesting a role in periodontal inflammation 345. Clinically, AMTN-functionalized hydroxyapatite nanoparticles show promise for enhancing dentin mineralization and improving dental restoration longevity 67.