Repair of aged bulk‐fill composite with posterior composite: Effect of different surface treatments

Objective In the present study, the ability of posterior resin composite to repair aged bulk‐fill resin composite and vice versa were assessed by shear bond strength testing. Materials and Methods Resin composite substrates were aged and surfaces were abraded with abrasive papers, then bulk‐fill substrates were repaired with posterior resin composite and vice versa using different surface treatments (no surface treatment [control]; etching with 37% phosphoric acid [H3PO4] for 20 seconds; etching with 10% hydrofluoric acid [HF] for 20 seconds; etching with 37% H3PO4 for 20 seconds + adhesive application; etching with 10% HF for 20 seconds + adhesive application; adhesive application only). Shear bond strengths (SBS) were then measured and surface roughness values (Ra) were determined. Cohesive strengths of nonaged resin composites were measured and used as reference groups. Resin composite surfaces after acid etching were evaluated by SEM. Data were analyzed using ANOVA and Fisher's LSD tests (P