The purpose of this study was to evaluate the effect of various application methods of one-step self-etch adhesives to microtensile resin-dentin bond strength.

Thirty-six extracted human molars were used. The teeth were assigned randomly to twelve groups (n = 15), according to the three different adhesive systems (Clearfil Tri-S Bond, Adper Prompt L-Pop, G-Bond) and application methods. The adhesive systems were applied on the dentin as follows: 1) The single coating, 2) The double coating, 3) Manual agitation, 4) Ultrasonic agitation. Following the adhesive application, light-cure composite resin was constructed. The restored teeth were stored in distilled water at room temperature for 24 hours, and prepared 15 specimens per groups. Then microtensile bond strength was measured and the failure mode was examined.

Manual agitation and ultrasonic agitation of adhesive significantly increased the microtensile bond strength than single coating and double coating did. Double coating of adhesive significantly increased the microtensile bond strength than single coating did and there was no significant difference between the manual agitation and ultrasonic agitation group. There was significant difference in microtensile bonding strength among all adhesives and Clearfil Tri-S Bond showed the highest bond strength.

In one-step self-etching adhesives, there was significant difference according to application methods and type of adhesives. No matter of the material, the manual or ultrasonic agitation of the adhesive showed significantly higher microtensile bond strength.

This study examined the effect of 2% chlorhexidine on the µTBS of a direct composite restoration using one-step self-etch adhesives on human dentin.

Twenty-four extracted permanent molars were used. The teeth were assigned randomly to six groups (n = 10), according to the adhesive system and application of chlorhexidine. With or without the application of chlorhexidine, each adhesive system was applied to the dentin surface. After the bonding procedure, light-cure composite resin buildups were produced. The restored teeth were stored in distilled water at room temperature for 24 hours, and then cut and glued to the jig of the microtensile testing machine. A tensile load was applied until the specimen failed. The failure mode was examined using an operating microscope. The data was analyzed statistically using one-way ANOVA, Student's t-test (p < 0.05) and Scheffé's test.

Regardless of the application of chlorhexidine, the Clearfil S³ Bond showed the highest µTBS, followed by G-Bond and Xeno V. Adhesive failure was the main failure mode of the dentin bonding agents tested with some samples showing cohesive failure.

The application of 2% chlorhexidine did not affect the µTBS of the resin composite to the dentin using a one-step self-etch adhesive.