Repair of direct restorative materials with a self-adhesive composite hybrid: Effects of substrate, surface pretreatment, and aging

Objectives To evaluate the effects of restorative substrate, pre-repair substrate aging, airborne-particle abrasion, adhesive application, and post-repair aging on the shear bond strength (SBS) of repairs performed with a self-adhesive composite hybrid. Methods The substrates were a conventional glass-ionomer cement (ChemFil Rock), a nanohybrid resin composite (Ceram.x Spectra ST), and a composite hybrid (Surefil one), which also served as the repair material in all groups. A 3 × 2 × 2 × 2 × 2 factorial design comprised 48 groups (n = 9; total n = 432). Substrates were thermocycled or unaged, standardized by P320 grinding, and optionally subjected to airborne-particle abrasion with 50-μm Al 2 O 3 and/or adhesive application. Completed repairs were thermocycled or left unaged. SBS was analyzed using a categorical fixed-effects model with HC3-robust inference and planned Welch comparisons with Holm adjustment. Pre-test failures (PTFs) were included as 0 MPa. Results Sixty-eight PTFs occurred (15.7%): 51 with the glass-ionomer cement, 17 with the composite hybrid, and none with the conventional composite. Significant main effects were found for all five experimental factors (p < 0.001). Under dual aging, the complete pretreatment protocol yielded the highest mean SBS for every substrate: 2.75 MPa for the glass-ionomer cement, 11.65 MPa for the conventional composite, and 12.60 MPa for the composite hybrid. Significance Surefil one showed potential for repairing the tested aged resin-containing substrates when the tested external adhesive was applied, whereas bonding to ChemFil Rock remained weak after aging. The substrate-dependent response highlights the importance of material composition in repair-protocol selection.