1,10-Phenanthroline enhances dentin bond durability via dual-site binding to collagen and matrix Metalloproteinase-8

This study aimed to evaluate the effect of 1,10-Phenanthroline (Phen) on dentin bond durability and to explore its potential interactions with matrix metalloproteinase-8 (MMP-8) and type I collagen.

Dentin specimens were etched with 35% phosphoric acid and pretreated with deionized water (DW), 2% chlorhexidine (CHX), ethanol (EtOH, Phen solvent), 0.01 mM Phen, 1 mM Phen, and 100 mM Phen. Following the application of a universal adhesive and composite resin, the specimens were divided into non-aged and aged (10,000 thermocycles) subgroups for microshear bond strength (μSBS), failure mode, nanoleakage, and in situ zymography analyses. Molecular docking was performed to assess Phen's binding affinity to MMP-8 and dentin collagen.

Non-aged groups showed comparable μSBS. After aging, the 1 mM and 100 mM Phen groups maintained bond strength, with no significant reduction observed. These groups also showed a tendency for reduced nanoleakage and lower MMP activity at the bonding interface compared to the DW and CHX groups. Moreover, the EtOH group demonstrated results comparable to the DW group, confirming that EtOH does not contribute to the efficacy of the Phen solution and that the observed benefits are attributable solely to Phen. Molecular docking suggested favorable binding energies for Phen with both type I collagen (-4.64 kcal/mol) and MMP-8 (-7.37 kcal/mol), involving hydrogen bonds.

1,10-Phenanthroline significantly improves the durability of the resin-dentin bond. Its superior performance over CHX is attributed to a dual-site mechanism that directly stabilizes collagen and potently inhibits MMP-8, thereby protecting the hybrid layer from degradation.

The results suggest that 1,10-Phenanthroline pretreatment could be a promising strategy to improve the long-term stability of adhesive restorations in clinical dentistry.