Shear Bond Strength of Aged Composite Restorations Repaired with a Universal Injectable Composite

Abstract

Objective: The purpose of this study was to analyze the shear bond strength of a universal injectable composite used in the repair of aged composites. Methods: A total of 100 disk-shaped specimens (8 mmx2 mm) were produced using five different composites (n=20) (Gradia Direct Posterior, Tetric N Ceram BulkFill, Filtek Z250, SonicFill and Filtek BulkFill Posterior). Specimens were polymerized using an LED light curing unit for 20 s and stored at 37 degrees C in distilled water for 3 weeks. Specimens were subdivided into two groups per composite for repair using either the same composite used for the specimen or G-aenial Universal Flo. Following acid-etching and silane application, a universal adhesive (G-Premio BOND) was applied and light-cured. The repair materials were placed on the bonded surfaces of the specimens and polymerized in silicone molds (2 mmx2 mm). After thermocycling to simulate aging, shear bond strength (SBS) was tested using a universal testing machine at a crosshead speed of 1 mm/min. Failure modes were examined using a stereomicroscope at x40 magnification. Results: No statistically significant differences were found among the tested composites repaired with their own substrates. However, the SBS SonicFill and Filtek Bulk Fill Posterior groups had significantly lower bond strengths when repaired with G-aenial Universal Flo in comparison to repairs made with their own substrates (p<0.05). Conclusion: When repaired with their own substrates, reliable bond strengths were obtained for all the composites tested.