Effects of different surface treatments and adhesive self-etch functional monomers on the repair of bulk fill composites: A randomised controlled study

Objective: To evaluate the effect of different adhesive protocols on the microtensile bond strength (?TBS) and integrity of the repaired bulk fill composite interface. Methods: Two hundred and seventy composite blocks made of bulk fill composites of different viscosity were randomly assigned to 18 surface conditioning groups (n = 15/group). The universal adhesive systems used were HeliobondTM, Tokuyama bond force IITM and Scotchbond UniversalTM. A nanohybrid resin composite was applied as the repair material. Negative and positive control groups were included. Stick shape specimens of each group were subjected to ?TBS testing. Representative samples from all test groups were subjected to microscopic, profilometric and SEM examination to determine their mode of failure. The data were analysed statistically using two-way ANOVA test, Tukey?s test and the independent t-test (? = 0.05). Results: The mean ?TBS of all test groups ranged between 28.5 and 46.8 MPa and varied with the type of adhesive system employed. Significantly highest ?TBS values were obtained when Tokuyama bond force IITM and Scotchbond UniversalTM adhesives were used (p 0.01) which were comparable to the coherent strength of the bulk fill resin composite in the positive control groups (p 0.05). The viscosity of the bulk fill composite did not significantly influence repair bond strength. The microscopy and SEM examination of the failed interfaces revealed a mixture of adhesive and cohesive failures. Conclusions: Under the tested conditions, significantly greater ?TBS of repaired bulk fill composite was achieved when the substrate surface was treated with adhesive systems containing a functional monomer. Clinical significance: Eff ;ecting a repair of a bulk fill resin composite restoration with the application of a functional monomer containing adhesive system, such as Tokuyama Bond Force IITM or Scotchbond UniversalTM, would seem to enhance the interfacial bond strength and integrity of the repaired resin composite interface.