The shear bond strength of repaired high-viscosity bulk-fill resin composites with different adhesive systems and resin composite types

Abstract

This study compared the effect of different adhesive systems and composite resins on the shear bond strength (SBS) of repaired high-viscosity bulk-fill composites(Tetric EvoCeram Bulk Fill) and investigated failure modes. One hundred twenty cylindrical bulk-fill composite blocks (diameter 5 mm) were fabricated and thermocycled for 5000 cycles (5-55 degrees C). Specimens were roughened by diamond bur and divided into 8 groups (n = 15). Bulk-fill blocks were repaired with the same material or nanohybrid composite resin(Tetric EvoCeram Nanohybrid) (diameter 3 mm) using different adhesive systems:Tetric N-Bond Universal (TSE);37% phosphoric acid etching + Tetric N-Bond Universal (TER); Clearfil SE Bond (CSE); 37% phosphoric acid etching + AdperSingle Bond 2(SB). After repair procedures, all specimens were thermocycled again. The shear bond strengths were measured for all specimens using a universal test machine (crosshead speed of 1 mm/min). Cohesive strengths of bulk-fill composites were measured and described as control group. Debonded surfaces were observed with a stereomicroscope under 10x magnification to determine mode of failure. The SBS data of all groups was statistically analyzed by two-way ANOVA and Bonferroni correction test (p < 0.05). The specimens repaired with bulk-fill composites showed significantly higher SBS values (25.86 +/- 5.74, 27.05 +/- 4.93, 24.49 +/- 6.95MPa) than those with nanohybrid composites (20.41 +/- 3.70, 22.08 +/- 6.37, 18.74 +/- 6.40 MPa) for TER,CSE,SB, respectively (p < 0.05). There were no significant differences in SBS according to the type of adhesive systems for both repair materials (p > 0.05). The predominant mode of failure was a mixed type in the restorative material except for the ones repaired with nanohybrid composites using AdperSingle Bond 2. High-viscosity bulk-fill composites could be successfully repaired with the same materials. SBS of repaired bulk-fill composites reached cohesive strength for all tested groups.