Objectives: To determine the microshear bond strengths of five 'all-in-one' adhesives and two 2-step self-etching primer adhesives to dentin with different tubule orientations and to compare bond strengths between the adhesives.
Material and methods: Human adult molar teeth were sectioned to obtain dentin pieces with tubule orientations perpendicular or parallel/oblique to the bonded surface. Two 2-step self-etching primer adhesives (Clearfil SE Bond (CSE), Optibond Solo Plus SE Bond (Op. SE)) and five all-in-one adhesives (Clearfil S(3) Bond (S(3)), Optibond All-in-One Bond (Op. AIO), G-Bond, Go!, and Xeno IV) were applied to dentin in accordance with the manufacturers' instructions. Resin composite cylinders were bonded to superficial and deep dentin using microtubes (0.75 mm internal diameter and 1.5 mm high). Bonded specimens were stored in water at 37 degrees C for 24 h, then stressed in shear at a cross-head speed of 1 mm/min until bond failure. Maximum load at failure (N) was recorded and converted to MPa. Statistical analyses were carried out using independent samples t-test and one-way ANOVA with Tukey's HSD test.
Results: Though bond strengths varied slightly, four all-in-one adhesives (Op. AIO, G-Bond, Go!, and Xeno IV) showed no significant differences in microshear bond strengths regardless of dentin depth (superficial or deep) or dentin tubule orientation (perpendicular or parallel/oblique). CSE, Op. SE, and S(3) showed significantly lower bond strengths to deep dentin with a tubule orientation perpendicular to the surface.
Conclusion: Most of the all-in-one adhesive systems used in this study appear to bond equally well to dentin independently of tubule orientation and depth. One two-step self-etching primer adhesive bonded significantly better than the all-in-one adhesives.