Silk Fibroin-Amorphous Calcium Phosphate Enhances Dentin Bonding Via Remineralization

This study aimed to investigate the effects of silk fibroin (SF) on amorphous calcium phosphate (ACP)-mediated remineralization to enhance the dentin bonding durability. Human dentin specimens were etched with 35% phosphoric acid and pretreated with deionized water or SF (0.001%–5%). The optimal SF concentration was determined by evaluating micro-shear bond strength (μSBS) and nanoleakage after bonding with cement using universal adhesive (after 0/10,000/30,000 thermocycles), as well as structural characterization (TEM/SEM for self-assembly morphology; ATR-FTIR for β-sheet conformation). Subsequently, universal adhesive containing ACP (0–20 wt%) was evaluated through dispersion (TEM), contact angle, and double bond conversion. Then, the combination of optimized SF-pretreatment and ACP-contained adhesive bonded with cement was validated for bonding interface stability via μSBS, nanoleakage, and enzymatic activity (after thermocycles mentioned above) and remineralization performance via surface microhardness and XRD analysis. Statistical analysis included ANOVA (P<0.05). The 0.1% and 1% SF groups maintained μSBS after 10,000 thermocycles, but a decline was observed after 30,000 thermocycles (P<0.05). SF could self-assembled into fibrous networks interwoven with dentin collagen. Combining SF (0.1% or 1%) with 1% ACP preserved μSBS post-30,000 cycles and increased surface microhardness (P<0.05), accompanied by higher hydroxyapatite content detected by XRD. SF self-assembly on dentin surfaces synergizes with 1% ACP significantly enhanced bonding durability via collagen remineralization. The optimal combinations were 0.1% SF + 1% ACP and 1% SF + 1% ACP.