Influence of bonded enamel margins on dentin bonding stability of one-step self-etching adhesives

To evaluate the dentin bonding durability of two one-step self-etching adhesive systems with and without the presence of surrounding enamel.

Tri-S Bond (Kuraray) and G-Bond (GC), commercially available adhesive systems, were used in this study. The occlusal enamel was removed in order to form a flat, midcoronal dentin surface. The adhesives were applied to both the dentin and the surrounding enamel surfaces according to the manufacturers' instructions. Resin composite crowns (Clearfil AP-X, Kuraray) were incrementally built up with each layer being photocured for 40 s. Half the bonded teeth were sectioned perpendicular to the adhesive interface into 0.7-mm-thick slabs, and then trimmed to an hourglass shape with a 1 mm2 cross-sectional area for microtensile bond strength testing, followed by storage in water for 6 months (direct water exposure group, DE). The other half were left untrimmed and stored in water for 6 months (indirect water exposure group, IE). As control groups, additional bonded teeth were prepared for water storage for 24 h. After the designated periods of water storage, the specimens were subjected to bond strength testing at a crosshead speed of 1.0 mm/min. The microTBS data were statistically analyzed using three-way ANOVA and post-hoc tests (t-test and Tukey's HSD comparison tests) (alpha = 0.05).

Indirect water exposure of the resin/dentin interface did not affect the microTBS of either adhesive after 6 months water storage (p < 0.05). However, direct exposure to water significantly reduced the microTBS of both adhesives to dentin (p < 0.05). In addition, there were no significant differences in muTBS between the two adhesive systems for each experimental storage condition (p > 0.05).

The durability of resin-dentin bonds was found to be dependent on the method in which the bonded specimens were aged in water. Significantly lower bond strengths were observed for specimens that were sectioned into an hourglass shape before aging compared to those that were sectioned after water storage.