Influence of silanes on the shear bond strength of resin cements to zirconia

Objective: To test the shear bond strength of self-adhesive and conventional resin cements to zirconia after the application of different types of silanes with/without aging. Method and Materials: Three hundred and sixty zirconia specimens were randomized into 10 groups (n = 36). Five groups were assigned to the self-adhesive resin cement RelyX-Unicem (RXU) and five groups to the conventional resin cement Panavia 21 (PAN). The groups were further assigned to the following pretreatments: Monobond-S (M), Alloy Primer (AP), Clearfil (C), Experimental Universal Primer (EUP), or without silane (control group). Twelve specimens of each of the cements were tested after water storage for 24 hours (initial shear bond strength). The remaining 24 samples were aged (1,500 cycles, n = 12; or 13,500 cycles, n = 12). The shear bond strength was measured (Universal Testing Machine; 1 mm/min, Zwick Roell Z010). Data were analyzed with one-way ANOVA followed by post-hoc Scheffé tests. Student's t test was applied to test the differences between the two cements (P .05). Results: The initial bond strength of RXU was increased by the application of the different silanes. The silanes had less influence on the initial bond strength of PAN. Aging reduced the bond strength of RXU significantly in combination with two of the silanes (AP, 0 ± 0 MPa; C, 4.1 ± 0.9 MPa; P .05). Aging led to a significant reduction of the bond strength values of PAN with the primers AP (2.9 ± 0.4 MPa) and EUP (2.5 ± 0.5 MPa; P .05). Conclusion: The present study indicates that the bond strength of the self-adhesive resin cement was positively influenced by the pretreatment of the zirconia surface with different silanes. Aging led to a decrease of the bond strength of both types of cements, irrespective of most of the silanes used. Keywords: aging, pretreatment, resin cements, self-adhesive resin cement, shear bond strength, silane, universal silane, zirconia