Effects of dentin surface preparations on bonding of self-etching adhesives under simulated pulpal pressure

Delayed light activation of resin composite affects the bond strength of adhesives under dynamic simulated pulpal pressure

OBJECTIVE

To evaluate the effect of a time delay before the light activation of resin composite on the microtensile bond strength (µTBS) of self-etch adhesives under dynamic simulated pulpal pressure.

MATERIALS AND METHODS

One hundred twenty crown segments were prepared from human third molars. Dentin surfaces were prepared with coarse diamond burs and connected to a dynamic pulpal pressure device. The self-etch adhesives used were Clearfil SE Bond (CSE), G2-Bond Universal (G2B), Clearfil Universal Bond Quick (CBQ), and G-Premio Bond (GPB). Each adhesive was divided into 3 subgroups: immediate light activation of resin composite (T₀), delayed light activation for 150 s (T₁), and 300 s (T₂). The µTBS data were obtained after 24-h water storage. Scanning electron microscopy was used to evaluate the nanoleakage at the resin-dentin surface. The µTBS data were analyzed using two-way ANOVA and Duncan's multiple comparisons.

RESULTS

All adhesives demonstrated a significant reduction in µTBS at T₂, except for CBQ where the bond strength was not affected by the delayed light activation times. The two-step self-etch adhesives (CSE and G2B) demonstrated higher bond strength than the one-step adhesives at all conditions. Nanoleakage was observed in all adhesives at T₂; however, nanoleakage was detected only in CBQ and GPB at T₁.

CONCLUSIONS

Delayed light activation of resin composite adversely affected the dentin bond strength of self-etch adhesives. Two-step self-etch adhesives had better bonding performance than one-step self-etch adhesives.

CLINICAL RELEVANCE

After adhesive application, resin composite should be adapted and cured as soon as possible.