Toward biomimetic direct restorations: A nanofiber-based interfacial strategy to approximate dentin-enamel junction behavior.

Abstract

The dentin-enamel junction (DEJ) is a biomechanically critical interface that dissipates stresses between brittle enamel and resilient dentin. However, current composite resin (CR)-based restorative protocols do not reproduce this functional behavior. This study evaluated whether the incorporation of electrospun nanofibers incorporated as a compliant interlayer within adhesive strategies can approximate selected biomechanical characteristics of the DEJ. Sound human molars were sectioned to obtain enamel, dentin, and DEJ specimens. Microhardness was measured across dental tissues and CR. Four groups were defined according to the interfacial strategy: Control (natural DEJ), Adhesive (adhesive system only), Flow (adhesive plus flowable CR), and Fiber (adhesive plus electrospun nanofiber layer). The Derjaguin-Müller-Toporov (DMT) modulus was assessed using atomic force microscopy in PeakForce quantitative nanomechanical mapping mode, interfacial morphology was analyzed by scanning electron microscopy, and microtensile bond strength was evaluated. Enamel exhibited higher microhardness than dentin (p < 0.05), whereas CR showed substantially lower values than enamel. The natural DEJ presented the lowest DMT modulus, consistent with its more compliant behavior. Adhesive and Flow groups exhibited higher modulus values, whereas the Fiber group showed values comparable to dentin and closer to the natural DEJ. Microtensile bond strength revealed no significant differences among experimental groups, although the Fiber group showed behavior closer to the Control. Morphological analysis indicated that the fiber-reinforced interface promoted a more continuous and integrated interfacial profile. Within the limitations of this study, the incorporation of electrospun nanofibers resulted in the formation of a compliant interfacial layer with mechanical characteristics approaching those of the DEJ. This proof-of-concept suggests that nanofiber-based interlayers may contribute to improved compliant behavior at the resin-dentin interface, representing a promising biomimetic strategy for direct restorative procedures.