Resin composite adhesion to dentin using different curing lights and adhesive systems applied under electric current

To evaluate the effect of electric current application on the resin composite-tooth bond strength and hybrid layer of three adhesive systems light-cured by two light-curing units (LCUs).

Human molar teeth were distributed into 12 groups (n=6). Three adhesive systems were used: two-step etch-and-rinse (SB2; Adper Single Bond 2, 3M ESPE); two-step self-etch (CSE; Clearfil SE Bond, Kuraray); and one-step self-etch (SBU; Single Bond Universal, 3M ESPE) applied with (50μA) and without (control; conventional application) electric current, and light-cured with different LCUs. Resin composite blocks (Filtek Z350XT, 3M ESPE) were produced and cut into sticks (~1mm²) for microtensile bond strength (μTBS). Fracture patterns were analyzed on stereomicroscope and classified as cohesive-dentin, cohesive-resin, adhesive, or mixed. Specimens were prepared for scanning electron microscope observation. The hybrid layer analysis was carried out using a confocal laser scanning microscopy (n=2). Data were submitted to three-way ANOVA followed by Tukey's post hoc test (α=0.05).

The electric current increased the μTBS for all adhesive systems light-cured with single-emission peak and multiple-emission peak LCUs. Both LCUs presented similar μTBS values. CSE applied under electric current showed the highest μTBS mean values. The adhesive failure pattern was more frequently observed in all groups. The electric current formed long resin tags for all adhesive systems.

The adhesive systems applied under electric current increased the bond strength using single-emission peak and multiple-emission peak LCUs.

Electric current at 50μA applied throughout the dentin is a safe mode and results in better impregnation of the adhesive systems.