Application of a chlorinated catechol monomer to enhance dentin bond durability and impart antibacterial activity

To synthesize a novel chlorinated catechol monomer, N-(2-chloro-4,5-dihydroxyphenethyl) methacrylamide (Cl-DMA), and evaluate its efficacy as a primer in enhancing dentin bond durability and imparting antibacterial properties. Cl-DMA at varying concentrations (0, 1, 3, and 5 wt%) dissolved in 50% DMSO/H₂O were applied as primer agent to dentin surfaces for 60 s. The interaction between Cl-DMA with type I collagen was assessed by ATR-FTIR and molecular docking. The effects of Cl-DMA primers on dentin bond strength and durability were comprehensively evaluated using degree of conversion (DC), micro-tensile bond strength (µTBS) test, fracture pattern observation, nanoleakage evaluation, and in situ zymography analysis. The antibacterial properties of Cl-DMA were assessed through colony forming unit (CFU) counting, CCK-8 assay, crystal violet staining, scanning electron microscopy (SEM) observation, and live/dead bacterial fluorescence staining. The assessment of Cl-DMA-induced cytotoxicity was performed by measuring cell viability with a CCK-8 kit and fluorescence staining. Cl-DMA potentially interacted with type I collagen via hydrogen bond. Pretreatment with Cl-DMA solutions effectively maintained resin-dentin bond strength, preserved stability of the bonded interface, and inhibited endogenous protease activity. Antibacterial effects against Streptococcus mutans biofilm formation and bactericidal capacity improved gradually with increasing Cl-DMA concentration. Cl-DMA was well-tolerated by the cells compared with Bis-GMA, with no observed cytotoxicity at doses up to 50 µg/mL. Pretreating dentin surface with Cl-DMA primer for 60 s can effectively stabilize the bonded interface and exhibit significant antibacterial efficacy.