Objective: This laboratory and in-silico study investigated the potential of carbon quantum dots (CQDs) to modulate the crystal orientation and mechanical properties of dentin hydroxyapatite (HAp), with a focus on the structurally critical c-axis.

Methods: Dentin specimens were treated with varying concentrations of functionalized CQDs (0.1 %-0.5 %) and subjected to artificial demineralization. Structural and mechanical changes were assessed using transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), nanoindentation, and density functional theory (DFT) simulations. Collagen organization and mineral crystallinity were evaluated through SAXS and NMR spectroscopy. Data were analyzed with one-way ANOVA and the Tukey Post hoc tests.

Results: CQD-treated groups, particularly at 0.3 % and 0.5 % concentrations, exhibited enhanced HAp crystallinity, improved alignment along the c-axis, and increased collagen fibril organization. Raman and XRD analyses confirmed higher mineral-to-matrix ratios and reduced lattice disorder. Mechanical testing revealed significant increases in hardness and elastic modulus. DFT simulations (p<0.05) supported the hypothesis of CQD-induced lattice stabilization via Ca-site substitution and spin-orbital coupling.

Conclusion: Functionalized CQDs represent a novel strategy for reinforcing dentin by modulating and modifying HAp crystal orientation and collagen architecture through quantum-level interactions.

Keywords: Collagen; Crystals; Cytotoxicity; Dentin; Hydroxyapatite; Raman.