Shear Bond Strength of Auto-mixing Self-adhesive Resin Cements to Zirconia

Objectives: This study evaluated the shear bond strengths of four auto-mixing self-adhesive resin cements {Maxcem Elite (Kerr), SpeedCEM (Ivoclar Vivadent), RelyX Unicem 2 Automix (3M ESPE), and GAM-200 (GC)} between dual-cured resin composite for core build-up (UniFil Core EM, GC) and partially-stabilized zirconia ceramic (GC). Methods: Zirconia disk specimens were sanded with grit #600 Silicon-carbide paper (SiC), treated with phosphoric acid gel (PAG, Kuraray) for 5 s, rinsed, and then air-dried (Control) Other specimens were treated with PAG after air-abrading with 50 µm alumina particles (AB). Composite disk specimens were sanded with #600SiC and then treated with PAG. Zirconia and composite disks were bonded together with each self-adhesive resin cement, and then photo-polymerized with a visible-light-curing unit for 40 s. Specimens were stored in water at 37ºC for 24 hrs and/or performed thermal cycling of 10,000 times before shear bond strength testing. Means and SDs (in parenthesis) of shear bond strength (MPa) are listed in Table. Data were analyzed by three-way ANOVA and identical letters were not significantly different by Tukey-Compromise test (p>0.05, n=7). Results: The bond strengths of four self-adhesive resin cements between resin composite and alumina-blasting zirconia were higher than those of control groups before thermal cycling. After thermal cycling, two of four resin cements to alumina-blasting zirconia showed insignificantly decrease of bond strength. Conclusions: These results suggest that bond durability is different between brands and alumina-blasting is necessary for durable bonding of zirconia to resin composite for core build-up with self-adhesive resin cement.