Influence of silane coupling agent and aging on the repair bond strength of dental composites

The objective of this work was to evaluate the effect of different protocols on the shear bond strength (SBS) of repairs made to aged composite resin substrates. Eighty cylindrical composite resin specimens (IPS Empress Direct, Ivoclar-Vivadent) were prepared, and divided into two main groups: in group 1 a silane agent was applied, while in group 2, the silane agent was not applied. Each group was then subdivided into four groups according to the adhesive system used: control, without any adhesive, Single Bond Universal, Tetric Bond Universal, and Clearfil SE Bond. As a reference group, the cohesive strength of the composite resin was determined. After applying the adhesive protocol, the treated surfaces were restored with composite resin cylinders. The specimens were stored in distilled water for 24 h or 6 months at 37 degrees C and subjected to a SBS test. The data were evaluated using a three-way ANOVA test followed by a Tukey test (alpha = 0.05). The previous application of silane did not significantly affect the SBS (p = 0.162), on the contrary, the type of adhesive protocol and aging impacted significantly (p < 0.001). The SBS was significantly higher when Clearfil SE Bond was used (p < 0.001), with the values achieved by this group being similar to those of the reference group (p >= 0.996). The use of a silane coupling agent before the application of an adhesive does not significantly affect the process of adhesion to an aged resin. The application of a solvent-free adhesive system was able to restore the cohesive strength values of the material.