Experimental primers containing synthetic and natural compounds reduce enzymatic activity at the dentin-adhesive interface under cyclic loading

- The use of different experimental primers on dentin-resin restorations is proposed.
- Experimental primers significantly reduced the enzymatic activity at the dentin-resin interface.
- Proanthocyanidins from enriched-grape seed extract, chlorhexidine and doxycycline inactivated rMMPs-2 and 9.
- Increased enzymatic activity took place under simulated cyclic loading.
- Cyclic loading did not have a significant effect on the resin-dentin bond strength.

ObjectiveTo evaluate the effect of experimental primers (chlorhexidine, enriched mixture of proanthocyanidins, and doxycycline) on the adhesive properties and gelatinolytic activity at dentin-resin interfaces of occlusal Class I restorations.MethodsThe inactivation of enzymes by the experimental primers was assessed by fluorescence assay and gelatin zymography. To assess the adhesive properties, occlusal Class I cavities were prepared in sound human molars, etched with phosphoric acid and restored with one of the primers and an etch-and-rinse adhesive system (Adper Single Bond Plus-3M ESPE). After the restorative procedures, specimens were divided into two subgroups (n = 6) consisting of storage in incubation buffer or axial cyclic loading at 50 N and 1,000,000 cycles. Then, the specimens were sectioned and slices were assigned to in situ zymography assay and microtensile bond strength (TBS) test.ResultsFluorescence assay and gelatin zymography revealed that the experimental primers inactivated rMMPs. In situ zymography (2-way ANOVA, Tukey, p < 0.05) showed that cyclic loading increased the gelatinolytic activity at the resin-dentin interface and the experimental primers decreased the gelatinolytic activity at the adhesive interface. The experimental primers had no significant effects on dentin-adhesive bond strengths with or without cyclic loading (2-way ANOVA, p > 0.05).SignificanceThe use of experimental primers impaired the enzymatic activity at the dentin-adhesive interface after cyclic loading and the activity of rMMPs. Cyclic loading did not have a significant effect on the bond strength.