Mussel wet adhesion inspired using dopamine methacrylamide as a primer to improve dentin adhesion

This study aimed to evaluate whether a mussel wet adhesion inspired catechol-functionalized primer (dopamine methacrylamide, DMA) can increase microtensile bond strength (μTBS) of dentin–resin adhesion and improve the bonding interface in vitro. DMA was synthesized and characterized by proton nuclear magnetic resonance spectral analysis and high-resolution mass spectrometer analysis. A total of 50 flat dentin slabs of 50 human 3rd molars were prepared and allocated into two groups for DMA application (the DMA and experimental groups) and distilled water (the DW and control groups). The dentin slabs were etched by phosphoric acid and treated with either DMA or distilled water before bonding by using an etch-and-rinse adhesive system as standard clinical protocol (n = 20 in each group). μTBS test was performed before and after thermocycling (×2500 cycles at 5 °C and 55 °C). The morphology and quality of dentin/adhesive interfaces or the fractured interfaces were examined by scanning electron microscopy (SEM). Mean μTBS (MPa) values of the DMA group vs. the DW group were 27.10 ± 11.34 vs. 21.30 ± 6.06 (p < 0.05) before thermocycling and 25.75 ± 8.74 vs. 19.87 ± 6.59 (p < 0.05) after thermocycling. SEM observation of dentin–resin binding interface showed that the DMA group had lesser defects than the DW group. Our study revealed that mussel wet adhesion inspired catechol-functionalized DMA may increase the bonding strength and improve the integrity of the interface of dentin adhesive when used as a dental primer.