Proanthocyanidin Acidic Primers Enhance Tissue-Driven Adhesive Restoration

The optimization of adhesive restorative techniques has increasingly focused on tissue biomodulation strategies, such as proanthocyanidin (PAC)-driven approaches, to increase the service life of dental restorations. The present study evaluated the long-term mechanical and sealing properties of dentin-resin interfaces using ligand-based PACs formulated as acidic primers. Four PAC preparations were produced (AA, BB, and AB trimers, as well as an ABA tetramer), and acidic primers were formulated with glycolic acid (GA). Dentin-resin interfaces (n = 8) were prepared using a simplified 2-step prime-and-rinse bonding protocol. Specimens were sectioned and their properties assessed immediately after 24 h of storage in simulated body solution and up to 1 y thereafter. The microtensile bond strength was assessed with a universal testing machine. The viscoelastic properties, storage modulus (E'), and damping capacity (tan δ) of the adhesive layer, hybrid layer, and underlying dentin were determined by a triboindenter in modulus mapping mode. Interfacial micropermeability was evaluated under a fluorescent microscope. Data analysis was based on 2-way analysis of variance followed by post hoc tests (α = 0.05). PAC-GA primer treatment groups exhibited significantly higher microtensile bond strength values than the control at each timepoint (P < 0.05). Treatment with PAC-GA primers with at least 1 A-type linkage exhibited higher E' than those with B type-only primers at the hybrid layer (Theobroma cacao-BB; P < 0.05). After 1 y, the Cinnamomum verum-AA acidic primer group exhibited the highest E' values among acidic primers at underlying dentin (P < 0.05). All PAC-GA primers reduced rhodamine infiltration at the hybrid layer and underlying dentin as compared with control (P < 0.05). Collectively, PAC-GA primers refine adhesive techniques, enhance bond strength, and extend long-term dentin-resin stability. The trimeric C. verum-AA outperformed the other PAC formulations by inducing the highest and/or most stable effects on the viscoelastic properties of the hybrid layer and the underlying dentin.