Structural Heterogeneity and Synergistic Failure of Dentin Bonding Joint

This study establishes the intrinsic structural features of the dentin bonding joint formed on a 3D porous DDM. The redistribution effect inherently produces a structurally and compositionally heterogeneous architecture, a two-layer, three-interface system in which a BisGMA-rich adhesive layer and a BisGMA-deficient hybrid layer coexist, characterized by interlayer modulus mismatch and inevitable defects at the hybrid layer bottom. Finite element modeling reveals that these two attributes act synergistically under loading: modulus gaps guide stress concentration toward the adhesive-hybrid layer interface; this stress then propagates toward the defect-rich bottom of the hybrid layer, where crack initiation and propagation ultimately occur. We therefore propose a dual-factor synergistic failure mechanism that revises the traditional defect-centric paradigm.