Surface Treatments and Bond Strength of Resin Cements to Glass-Ceramic

Objectives: To investigate the effect of surface treatment protocols on the shear bond strength of lithium disilicate (LD) glass-ceramic restorations (IPS e.max Press, Ivoclar Vivadent) to two resin cements.
Methods: Two-hundred ten blocks (4X4X3mm) of LD glass-ceramic were embedded in autopolymerizing acrylic resin cylinders keeping the ceramic surface exposed for bonding. Ceramic specimens were randomly allocated into fourteen groups (n=15), of which six received Variolink Esthetic DC cement (VE) and eight received RelyX Ultimate cement (RU), following the surface treatments: G1)Positive control- Hydrofluoric Acid + Silane (HF+Sil); G2)Negative control- saliva (S); G3)Saliva + Ivoclean (S+IC); G4) Saliva + Phosphoric Acid (S+P); G5)Saliva + Monobond Etch & Prime (S+EP); G6)Monobond Etch & Prime (EP). For RU, two additional treatments were used: G7)Saliva + Monobond Etch & Prime + Scotchbond™ Universal (S+EP+SB); G8)Monobond Etch & Prime + Scotchbond™ Universal (EP+SB). Following treatment, a cylinder of resin cement (2.3mm diameter) was built on the glass-ceramic surface, photocured (20s), stored in distilled water (37°C, 24h) and submitted to the shear bond strength test. Bond strength data (MPa) were subjected to two-way ANOVA and Tukey (a=0.01).
Results: Cement and surface treatment had a significant effect on the bond strength between glass-ceramic and resin cement (P<0.001) (Table 1). For both cements, EP presented significantly higher shear bond values as compared to the gold standard, HF+Sil. Moreover, EP presented the highest bond strength when compared to other cleaning agents, IC and P, following saliva contamination. The use of SB adhesive did not impact the effectiveness of EP for RU, hence simplifying the number of procedural steps.
Conclusions: Single-step EP significantly improved the bond strength of resin cements to LD glass-ceramic with and without saliva contamination. EP effectively replaced HF+Sil with the benefits of presenting higher bond strength, and a safer and simpler procedure to be employed in clinics.