Anti-proteolytic property and bonding durability of mussel adhesive protein-modified dentin adhesive interface

To evaluate the effect of mussel adhesive protein (MAP) on collagenase activity, dentin collagen degradation and microtensile dentin bond strength (μTBS). Three groups were designed: 1. experimental group: treated with MAP; 2. positive control: treated with GM6001 (collagenase-inhibitor); 3. negative control: treated with distilled water (DW). For collagenase activity, Clostridiopeptidase-A was added to each group (n = 5), and collagenase activity was assessed by colorimetric assay. For dentin collagen degradation, thirty dentin slabs were allocated to the three above groups (n = 10). Dentin collagen degradation was evaluated by measuring released hydroxyproline by colorimetric assay after being incubated in Clostridiopeptidase-A for 7 days. For microtensile bond strength, sixty human third molars with flat dentin surfaces were etched by phosphoric acid and then assigned to the three above groups (n = 20). An etch-and-rinse adhesive system was applied to all three groups as stated in standard clinic protocol. The test of μTBS was performed before and after thermocycling and collagenase challenge. The collagenase activities (nmol/min/mg) in the group of MAP was significantly less inactive compared to the group of GM6001 and DW (MAP < GM6000 < DW, p < 0.01). The hydroxyproline concentrations (μg/mL) was significantly less in the group of MAP compared to the group of GM6001 and DW (MAP < GM6000 < DW, p < 0.01). While there was no significant difference in the immediate μTBS (MPa) among three groups (p > 0.06), the value of μTBSs after thermocycling and collagenase challenge was significantly greater in the group of MAP and GM6001 compared to the group of DW (MAP, GM6000 > DW, p < 0.001). MAP inhibits collagenase activity, prevents dentin collagen degradation, and delays the deterioration of the dentin bonding of composite restoration over time.