Bond Strength of Resin Cements to Zirconia After Surface Treatments

Objectives: This study investigated the shear bond strength (SBS) between resin cements and a partially yttria-stabilized tetragonal zirconia (Y-TZP) after different surface treatments.
Methods: Y-TZP (VIPI BLOCK ZIRCONN; VIPI) discs were cutted (N=150), polished, sintered (5.0x2.0 mm) and treated as follow (n=30): 1-None (as-sintered/control group); 2-Sandblasting with 50-μm aluminum-oxide (Al₂O₃) particles; 3-Universal adhesive (Single Bond Universal; 3M ESPE); 4-Sandblasting with 50-μm Al₂O₃ followed by Single Bond Universal; and 5-Experimental adhesive treatment (sandblasting with glass-modified 100-μm particles + adhesive based on methacrylated polymers). Composite resin (Filtek Z350 XT; 3M ESPE) discs (5.0x2.0 mm) were bonded to the Y-TZP surfaces using a conventional (RelyX Ultimate; 3M ESPE) or a self-adhesive (RelyX U200; 3M ESPE) dual-cured resin cements. Specimens were stored in distilled water at 37 degrees Celsius for 24h and then submitted to SBS tests in an electromechanical testing machine (EMIC DL2000; 2.0kN load cell; tensile force: crosshead speed of 1.0 mm/min). The adhesive area of each specimen was analyzed in a stereomicroscope (30X), and the modes of failure were classified as adhesive, cohesive (composite resin and/or resin cement), or mixed. Also, for each experimental condition, the Y-TZP surface (n=5) was examined by scanning electron microscopy (30 and 500X). SBS data (MPa) were submitted to normality, homogeneity, and two-way ANOVA followed by Dunnett’s C test (α=.05).
Results: As-sintered specimens showed the lowest SBS results (p<.05). The 50-μm Al₂O₃/Universal adhesive treatment produced the highest SBS mean values (p<.05), regardless of the cement used. The experimental treatment presented an intermediate performance. No differences (p>.05) were found between the resin cements evaluated. Failure mode was predominantly adhesive.
Conclusions: The surface treatments were decisive for the adhesive bonding between resin cement/zirconia. The 50-μm Al₂O₃/Universal adhesive treatment produced encouraging results, irrespective of the resin cement.