Microtensile bond strength of prehybridized dentin: storage time and surface treatment effects

This study evaluated the effect of surface treatments of the prepolymerized adhesive layer in the immediate dentin sealing technique (IDS) on the microtensile bond strength of two-step etch-and-rinse adhesive systems.

The occlusal dentin surfaces of 60 human third molars were exposed and Adper Single Bond 2 (SB) or Prime & Bond NT (PB) adhesive systems were applied (control groups). Immediately afterwards, the temporary cement RelyXTemp NE was applied on the bonded dentin surface, and the teeth were stored in artificial saliva for 48 h or 4 months. After the storage time, the temporary cement layer was removed and the following surface treatments were applied: aluminum oxide (AO), 37% phosphoric acid (PA), or AO+PA. Next, a second adhesive layer was applied for each adhesive system, and a composite resin block restoration (Z250) was built. The specimens were cut and submitted to microtensile strength (microTBS) testing. The adhesive layer thickness (ALT) was evaluated in other specimens from all groups by SEM. The fracture pattern was evaluated in all sticks tested by SEM. microTBS and ALT values were analyzed with two-way ANOVA and Tukey's test (alpha = 0.05).

The highest microTBS, similar to the control, was obtained with aluminum oxide and phosphoric acid (AO+PA) for both adhesives systems. The use of aluminum oxide alone (AO) or associated with phosphoric acid (AO+PA) showed values close to those of the control groups in relation to the ALT. The failure pattern was the same for control groups and AO +PA groups.

Dentin prehybridization can improve the adhesive bond strength if the bonded surface is treated with airborne aluminum oxide particle abrasion associated with 37% phosphoric acid, followed by application of a second adhesive layer.