Purpose: This in-vitro study evaluated the effect of universal adhesives and sandblasting with 50 μm and 110 μm aluminum oxide particles (Al2O3) on the shear bond strength (SBS) between composite and zirconia in repair applications across different aging intervals.
Materials and Methods: 1296 zirconia specimens (Katana Zirconia HT) were randomized into three main groups: (A) sandblasting with 50 μm Al2O3, (B) sandblasting with 110 μm Al2O3, and (C) control. Each group was further divided into six subgroups: OPB (Optibond Universal), PBA (Prime&Bond Active), IBU (iBond Universal), CUBQ (Clearfil Universal Bond Quick), MBP (Monobond Plus), and SBUP (Scotchbond Universal Plus). Composite (Clearfil Majesty ES-2 Universal) was applied, and SBS (MPa) measured at baseline (24-h storage) at 30 and 90 days, and after 7 days + 5000 thermocycles (5–55°C). Failure modes were assessed at 40 × magnification. Analysis used a generalized linear model (GLM) with Bonferroni adjustment (α 0.05).
Results: Sandblasting significantly increased SBS compared to controls, with Group B showing the highest durability after thermocycling, with values decreasing over aging periods. In Groups A and B IBU (21.43 ± 2.7 MPa; 25.60 ± 5.78 MPa), SBUP (19.26 ± 3.2 MPa; 23.62 ± 4.4 MPa), and CUBQ (19.92 ± 2.8 MPa; 22.75 ± 4.34 MPa) achieved the highest SBS, with adhesive failures being predominant and cohesive failures mainly in high-SBS subgroups.
Conclusion: Pretreatment with Al2O3 significantly enhances composite-zirconia bond strength, with larger grit sizes more effective. MDP-containing adhesives are recommended for reliable zirconia repairs.