Abstract
Aim: To evaluate the effect of bleaching on the shear bond strength of two different adhesive systems and nanohybrid composite resin to enamel.
Materials & Method: Forty enamel specimens were prepared from human premolar teeth and divided into four groups on the basis of the type of adhesive protocol (total-etch or self-etch adhesive systems) used. Twenty of the specimens were bleached with 40% hydrogen peroxide and divided into two groups for further adhesive procedures. The remaining specimens that were not bleached were considered to be the control group and were restored using the two different adhesive systems. After completion of the adhesive procedures, nanohybrid composite resin cylinders (2 mm x 3 mm) were bonded to the enamel surfaces. All specimens were then subjected to a shear bond strength test on a universal machine, and the fracture patterns were assessed using a stereomicroscope.
Results: The mean shear bond strength was significantly lower in the groups that underwent bleaching compared with the control groups that were not subjected to bleaching (alpha = 0.05). Moreover, greater shear bond strength was observed when using self-etch adhesives compared with total-etch adhesives.
Conclusion: The shear bond strength between composite resin and enamel decreased upon bleaching. Moreover, it was significantly better when self-etch adhesive systems were used.