Green synthesis of chitosan- and fluoride-functionalized silver nanoparticles using Camelia sinensis: Characterisation and dental applications

This research aimed to synthesise and characterise chitosan/fluoride functionalised silver nanoparticles (AgNPs) reduced with white tea (Camellia sinensis, WT) and evaluate the effects of WT_AgNPs application on demineralised dentine. The WT_AgNPs were characterised to determine their molecular composition, organic matter content, crystallite size, and degree of aggregation. Forty human molars were randomly assigned to different control groups: sound dentine (SD) and demineralised dentine (DD), and experimental groups: WT_AgNPs, WT_AgNPs_NaF, and WT_AgNPs_CHS. Then, the nanoparticles were applied to the DD control group to evaluate the chemical, crystallographic, and microstructural characteristics of treated-dentine. In addition, a three-point bending test was employed to assess dentine's mechanical response. The WT_AgNPs showed molecular groups related to various organic compounds, potentially acting as reducing and capping agents. All AgNPs presented spherical shapes with crystal sizes of approximately 20 nm. The application of WT_AgNPs indicated a higher degree of mineralisation and crystallites sizes of hydroxyapatite than the DD group. SEM images showed that WT_AgNPs presented different degrees of aggregation and distribution patterns on the surface of the demineralized dentine. The dentine flexural strength was significantly increased in all WT_AgNPs groups compared to control groups. The application of WT_AgNPs demonstrated remineralising and strengthening potential on demineralised dentine.