Shear bond strength of different composite repair systems to zirconia restoration

Abstract Background Zirconia use in dental restorations is hindered by challenges in achieving a robust bond with composite resin due to its crystalline nature. This study investigates the shear bond strength of repaired zirconia using Scotchbond Universal Adhesive, Dentobond, and Futurabond M+, comparing universal adhesives to a traditional zirconia primer. Objectives To assess shear bond strength before and after thermocycling, comparing Scotchbond to Dentobond and Futurabond M+ on zirconia surfaces. Materials and methods Forty-two zirconia discs underwent standardized surface treatments with different adhesives. Shear testing prethermocycling and postthermocycling was performed using an universal testing machine. Modes of failure were analyzed using digital microscope with magnification ×90. Results Universal adhesive demonstrated significantly higher shear bond strength than zirconia primers, both prethermocycling and postthermocycling. Thermocycling reduced bond strength across groups, with mixed failures predominating. Specifically, Group S exhibited the highest nonaged shear bond strength (9.906 MPa), outperforming Group D (7.71 MPa), and Group F (6.54 MPa). After thermocycling, Group S maintained the highest bond strength (6.49 MPa), followed by Group F (4.424 MPa), while Group D had the lowest value (4.04 MPa). Conclusions Universal adhesives, exhibited superior shear bond strength on zirconia compared to traditional zirconia primers before and after thermocycling. The impact of thermocycling underscores the need for resilient adhesive systems in zirconia repairs. Universal adhesives offer simplicity and efficacy, presenting viable alternatives for zirconia bonding in clinical scenarios.