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 mm×2 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 37ºC 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 mm×2 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 ×40 magnification.Results: No statistically significant differences were found among the tested composites repaired with their own substrates. How-ever, 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.