Abstract
Objectives: The purpose of this study was to compare the effect of plasma irradiation and other surface preparation methods on the microtensile bond strength of repaired resin composites. Materials and Methods: Twenty molds of a universal nanohybrid composite were prepared, aged and subjected to thermocycling. The specimens were divided into 5 groups for surface preparations including, C (Control): application of GC G-Premio Bond (GP) only; SB: sandblasting with alumina and GP; SI: application of phosphoric acid etching, silane, and unfilled resin; RB: roughening by diamond bur, phosphoric acid etching and GP; PL: application of argon and atmosphere plasma and then GP. The specimens were repaired with the new resin composite, cut to 1mm(2) beam, and then subjected to thermocycling. The microtensile bond strengths were measured using a universal testing machine. The failure modes were assessed with a stereomicroscope. Data were analyzed using two-way ANOVA and Tukey's test. The level of significance was α=0.05. Results: The highest mean bond strength was found for the application of universal bonding GC GP in controls (26.62MPa) and the lowest average bond strength belonged to the SI groups (9.06MPa). The difference in the mean bond strength between the SI group and other groups was significant (P<0.05). The failure mode of specimens in all groups was predominantly adhesive. Conclusion: The application of GP as an intermediate universal adhesive established a proper bond between the old and new resin composite. In addition, the plasma application and other surface preparation methods did not significantly improve the bond strength.