Melatonin-doped polymeric nanoparticles induce high crystalline apatite formation in root dentin Toledano Osorio, Manuel Sánchez Aguilera, Fátima Muñoz Soto, Esther Osorio Ruiz, María Estrella Toledano Pérez, Manuel Escames Rosa, Germaine Medina Castillo, Antonio Luis Osorio, María T. López López, Modesto Torcuato Vallecillo Rivas, Marta Osorio Ruiz, Raquel Apatite Dentin Hardness Melatonin Polymeric nanoparticles Remineralization Transmission electron microscopy X-ray diffraction This work was funded by the Ministry of Economy and Competitiveness and European Regional Development Fund( MINECO/AEI/FEDER/UE) Project number PID2020-114694RBI00. Funding for open access charge: University of Granada / CBUA. Objective. To investigate the effect of novel polymeric nanoparticles (NPs) doped with melatonin (ML) on nano-hardness, crystallinity and ultrastructure of the formed hydroxyapatite after endodontic treatment. Methods. Undoped-NPs and ML-doped NPs (ML-NPs) were tested at radicular dentin, after 24 h and 6 m. A control group without NPs was included. Radicular cervical and apical dentin surfaces were studied by nano-hardness measurements, X-ray diffraction and transmission electron microscopy. Mean and standard deviation were analyzed by ANOVA and StudentNewman-Keuls multiple comparisons (p < 0.05). Results. Cervical dentin treated with undoped NPs maintained its nano-hardness values after 6 m of storage being [24 h: 0.29 (0.01); 6 m: 0.30 (0.02) GPa], but it decreased at apical dentin [24 h: 0.36 (0.01); 6 m: 0.28 (0.02) GPa]. When ML-NPs were used, nano-hardness was similar over time [24h: 0.31 (0.02); 6 m: 0.28 (0.03) GPa], at apical dentin. Root dentin treated with ML-NPs produced, in general, high crystallinity of new minerals and thicker crystals than those produced in the rest of the groups. After 6 m, crystals became organized in randomly oriented polyhedral, square polygonal block-like apatite or drop-like apatite polycrystalline lattices when ML-NPs were used. Undoped NPs generated poor crystallinity, with preferred orientation of small crystallite and increased microstrain. Significance. New polycrystalline formations encountered in dentin treated with ML-NPs may produce structural dentin stability and high mechanical performance at the root. The decrease of mechanical properties over time in dentin treated without NPs indicates scarce remineralization potential, dentin demineralization and further potential degradation. The amorphous stage may provide high hydroxyapatite solubility and remineralizing activity. 2021-12-03T12:44:38Z 2021-12-03T12:44:38Z 2021-11 journal article Toledano-Osorio, M., Aguilera, F. S., Muñoz-Soto, E., Osorio, E., Toledano, M., Escames, G., ... & Osorio, R. (2021). Melatonin-doped polymeric nanoparticles induce high crystalline apatite formation in root dentin. Dental Materials. [https://doi.org/10.1016/j.dental.2021.09.001] http://hdl.handle.net/10481/71889 10.1016/j.dental.2021.09.001 eng http://creativecommons.org/licenses/by-nc-nd/3.0/es/ open access Atribución-NoComercial-SinDerivadas 3.0 España Elsevier