Effect of Sonic Application Mode on the Microtensile Bond Strength of Two Adhesive Systems

Background: This study aimed to compare the effects of application according to manufacturers’ instructions and sonic activation on the microtensile bond strength (µTBS) to dentin of a universal adhesive system and a two-step self-etch adhesive system.Materials and Methods: Forty caries-free human molars were randomly assigned to four experimental groups (n = 10) based on adhesive system and application mode (slight rubbing or sonic activation). A universal adhesive system (Nova Compo B Plus [NC]; Imicryl, Turkey) and a two-step self-etch adhesive system (Clearfil SE Bond [SE]; Kuraray, Japan) were evaluated. Each adhesive was applied either with a slight rubbing motion, as recommended by the manufacturers, or with sonic activation. All teeth were restored with a composite resin compatible with the respective adhesive system. After storage in distilled water at 37°C for 24 hours, specimens were sectioned into stick-shaped samples with a cross-sectional area of approximately 0.9 mm². Microtensile bond strength testing was performed at a crosshead speed of 0.5 mm/min, and failure modes were assessed under a stereomicroscope. Data were analyzed using two-way ANOVA followed by Tukey’s post hoc test (α = 0.05), and failure mode distributions were evaluated using the chi-square test.Results: Adhesive failures were observed in all groups. Sonic application significantly reduced the µTBS of the universal adhesive system compared with conventional rubbing application (P < 0.05). However, sonic activation did not significantly affect the dentin bond strength of the two-step self-etch adhesive system.Conclusion: The effect of sonic application on dentin bond strength appears to be adhesive-system dependent. While sonic activation adversely affected the bonding performance of the simplified universal adhesive system, it had no significant effect on the bond strength of the two-step self-etch adhesive system.