Effect of different desensitizing adhesive systems on the shear bond strength of composite resin to dentin surface

Objective The aim of this study was to evaluate the effect of different desensitizing agents, oxalate desensitizer and I-Bond, on the shear bond strength of composite resin to dentin surface. Materials and methods Occlusal surfaces of 80 sound human molars extracted were trimmed to expose a flat dentin surface. Each prepared sample was inserted in a metallic mold, which was designed with a Teflon mold having a hole (4 mm diameter ×3 mm height) for filling the restorative material. The samples were divided into four groups (20 each): group I (the control group), in which Adper Single Bond 2 and composite were applied; group II, in which oxalate desensitizer (D/Sense Crystal) was applied followed by Adper Single Bond 2 and composite; group III, in which oxalate desensitizer was applied, followed by re-etching and application of Adper Single Bond 2 and composite; and group IV, in which I-Bond and composite were used. All samples were thermocycled for 500 cycles (5–55°C). The samples in each group were subdivided into two subgroups (10 each) (A and B) according to storage time (24 h or 6 months, respectively). Shear bond strength of eight samples from each subgroup was measured. Debonded surfaces were examined under a stereomicroscope at magnification ×40 to determine the mode of failure. The remaining two samples were prepared to be examined under scanning electron microscope to reveal the resin penetration. Results Group I (the control group) recorded the highest shear bond strength values (11.838 ± 3.141 and 6.842 ± 3.912, respectively) in the two subgroups, followed by group IV (6.695 ± 3.164 and 6.217 ± 3.276, respectively) and group III (7.707 ± 3.845 and 3.681 ± 1.743, respectively), whereas the lowest values were found in group II (6.347 ± 3.208 and 3.240 ± 1.804, respectively). The incidence of adhesive mode of failure was higher in all tested groups, followed by mixed mode. Scanning electron microscope results confirmed the obtained statistical analysis of collected data. Clinical significance Both desensitizing agents and storage time had a negative significant effect on the shear bond strength of composite restoration to dentin surface.