Abstract
Apatite-based compounds, particularly hydroxyapatite (HA) and fluorapatite (FAp), are fundamental to the composition of dental and skeletal hard tissues and have become integral to preventive, restorative, and regenerative dentistry. Their close chemical similarity to natural enamel and bone, combined with excellent biocompatibility, bioactivity, and low solubility, underpins their diverse clinical applications. This review synthesizes current evidence on the use of stoichiometric and ion-substituted apatites, with a focus on nano-hydroxyapatite (nHA), in caries prevention, enamel remineralization, dentin hypersensitivity reduction, acid erosion protection, restorative materials, endodontic therapies, periodontal regeneration, and implant surface modification. Key findings indicate that nHA exhibits comparable or superior remineralization potential to fluoride in early enamel lesions, effectively occludes dentinal tubules, and enhances the bioactivity of restorative cements and adhesives. Ion substitutions (e.g., fluoride, zinc, strontium, magnesium, silicon) have been shown to improve mechanical performance, osteoconductivity, and antimicrobial properties. Despite these advantages, challenges persist in large-scale production of high-purity nanoparticles, ensuring long-term clinical durability in the oral environment, and standardizing material characterization. Safety profiles remain favorable, but further longitudinal studies are required to confirm the efficacy and biocompatibility of emerging apatite-based formulations. Future directions include the development of multifunctional, “smart” biomaterials integrating apatites with responsive ion release and targeted biofilm resistance, aimed at improving restoration longevity, implant integration, and preservation of natural dentition.