[Influence of different dentin depths on microtensile bond strength of two dentin adhesive systems]

To determine the microtensile bond strength of two adhesives systems to either superficial or deep dentin.

The crowns extracted human premolars were transversally sectioned next to the occlusal DEJ to expose flat dentin surfaces. The surfaces were bonded with: (1)two-step, total-etch adhesive Prime&Bond NT (PB),(2)wo-step, self-etching adhesive FL-Bond (FB), according to manufacturers' directions. Composite build-ups were constructed incrementally. After storage for 24 hours in water at 37 degrees, the teeth were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks with a cross-sectional area of 0.81mm(2) with a slow-speed diamond saw. The remaining dentin thickness (RDT) was measured to assess the superficial dentin group (RDT> or =3mm) and the deep dentin group (RDT< or =2mm). Microtensile bond strength measurements were evaluated. Fractured specimens were examined with a stereomicroscope at 60 magnification to determine the mode of failure. SPSS11.5 software package was used for analysis of the bond strengths.

The results showed the bond strength of Prime&Bond NT were significantly higher either to superficial or deep dentin(P<0.05). Different dentin depths had no effect on the microtensile bond strengths of dentin bonding agent (P>0.05). No cohesive failure was observed in either superficial or deep dentin. Most of the failure was adhesive failure.

From this study, it can be concluded that different dentin depths can not influence the microtensile bond strengths of Prime&Bond NT and FL-Bond adhesive systems.