The effect of water storage on micro-shear bond strength of contemporary composite resins using different dentin adhesive systems

Purpose: To evaluate effect of water storage on micro-shear bond strength of adhesives to class I cavity-bottom dentin using two types of composites resin. Materials and methods: Ninety teeth were divided into three groups I,II III (thirty molars each) according to the adhesive used, either total-etch 2-step (Adper Single Bond, 3M ESPE), self-etch 2-step(Clearfil SE Bond, Kuraray), or self-etch 1-step(Futura Bond, Voco) respectively. Each group was subdivided according to type of composite restoration used, either Hybrid (Clearfil APX, Kuraray), and Packable (Filtek P60, 3M ESPE). All teeth were thermocycled for 500 cycles, and subjected to occlusal load cycling for 120.000 cycles corresponding to 6 months clinical use. Bonding effectiveness was assessed by micro-shear bond strength test (mSBS) after 1 day, 3 months, and 6 months water storage. Results: The mean mSBS values (±SD) for Subgroup IA(SB2-APX) were 32.58 ± 1.416, 31.820 ± 2.119, and 30.910 ± 1.393 MPa after 24 h, 3 month, and 6 month respectively; while for Subgroup I B(SB2-P60) were 31.960 ± 1.659, 31.350 ± 1.765, and 30.380 ± 1.773 MPa respectively. Subgroup II A (CSE-APX) recorded 37.28 ± 1.061, 36.77 ± 2.32, 36.21 ± 1.964 MPa, while Subgroup II B(CSE-P60) recorded 37.0 ± 2.115, 36.460 ± 1.727, and 36.080 ± 1.910 MPa after 24 h, 3 month, and 6 month respectively. Subgroup III A (FB-APX) showed 30.550 ± 2.088, 26.890 ± 1.533, and 21.590 ± 1.784 MPa, while subgroup III B (FB-P60) showed 29.790 ± 1.172, 25.960 ± 2.672, and 21.410 ± 2.126 MPa after 24 h, 3 month, and 6 month respectively. Conclusion: Two-step Total-etch and Two-step self etch adhesives showed better tolerance to water storage compared to One-step selfetch adhesive.However, the type of composite restoration had no significant effect on the microshear bond strength of dental adhesives.