Organic complex based on cryomilled particles and doxycycline-laden electrospun fibers to improve the performance of a universal dental adhesive.
OBJECTIVES The long-term stability of resin-dentin bonds is limited by hydrolytic degradation of the hybrid layer. This study developed and evaluated a bioactive organic complex obtained by electrospinning and cryogenic milling (CP-EF) and investigated its effect when incorporated into a universal dental adhesive. METHODS Doxycycline (DOX)-loaded poly(ε-caprolactone) fibers were initially fabricated by electrospinning and subsequently processed by cryomilling to generate fibrous microparticles (CP-EF), enabling their homogeneous incorporation into the adhesive at 5 wt.% and 10 wt.%. The electrospun fibers and the CP-EF complex were characterized regarding morphology, chemical composition, drug release, and biocompatibility. The modified adhesives were evaluated for degree of conversion, wettability, water sorption, solubility, and surface interaction with dentin (Raman spectroscopy). Live/dead assay was used to evaluate the antibacterial effects against S. mutans biofilm. Zymography assay was used to test the inhibition potential against metalloproteinases (MMP-2 and MMP-9). Bonding performance was assessed by microtensile bond strength (µTBS) and work of fracture (Wf), tested immediately and after accelerated aging in sodium hypochlorite (NaOCl). RESULTS Fiber incorporation did not impair polymerization efficacy or immediate bonding performance. CP-EF-modified adhesives exhibited increased hydrophilicity, ability of releasing DOX, enhanced dentin surface interaction, and antibacterial effects against S. mutans. The CP-EF10% formulation inhibited the expression of both MMPs, whereas the other adhesives did not exhibit any MMP inhibition potential. Raman spectroscopy revealed the presence of DOX within the hybrid layer for CP-EF-treated dentin. After aging, the adhesive containing 10 wt.% CP-EF preserved bond strength and showed significantly higher µTBS and Wf compared with the control and 5 wt.% group. Stress-strain analysis revealed a multi-stage deformation mechanism, indicating a tougher and more damage-tolerant resin-dentin interface. CONCLUSIONS The electrospinning-cryomilling strategy enabled the development of a bioactive fibrous complex capable of reinforcing adhesive interfaces and mitigating hydrolytic degradation via MMP inhibition, supporting its potential for improving the longevity of resin-dentin bonds and capable of bacteria inhibition. CLINICAL SIGNIFICANCE An adequate loading of electrospun fibrous particles can modulate interfacial mechanics and degradation pathways, supporting the potential of this strategy to develop more bioactive, compliant and durable adhesive systems.