Methods : Twenty-four third molars were used (n=6/group). After removal ofocclusal enamel under water cooling, exposed dentin was etched with 37% phosphoric acid for 15 s followed by 30 s protease inhibitor treatment: Group 1 without inhibitor (control group); Group 2 with E-64 (0.5 mM); Group 3 with galardin (50 µM); and Group 4 with E-64 and galardin. A single-bottle etch-and-rinse adhesive (SingleBond, 3M ESPE) was applied and resin composite (FILTEK Supreme XTE, 3M ESPE) were build-up to a height of 6 mm. The teeth were stored in distilled water for 24 h at 37°C, then sectioned into 0.9x0.9 mm thick beams and stored in artificial saliva at 37°C for 24 h prior to testing. µTBS (n =45/group) was tested using Bisco MicrotensileBond Tester (Bisco, USA), and failure modes were determined. Data were statistically analyzed using ANOVA and Tukey’s post-hoc tests (α= 0.05).
Results: The mean µTBS (MPa) results were as follows: Group 1: 35.85 (±4,4), Group 2: 41.64(±5,3), Group 3: 40.18 (±4.7), Group 4: 41.88 (±7.2). E-64 alone and together with galardin had a significant effect (p<0.05) on immediate bond strength.
Conclusion: Pretreatment of the demineralized dentin with a specific cysteine cathepsin inhibitor (E64) or a specific matrix metalloproteinases inhibitor (galardin) showed better or similar immediate microtensile bond strength compared to control.