Performance of universal adhesives on bonding to leucite-reinforced ceramic

Abstract

Background: This study aimed to investigate the microshear bond strength of universal bonding adhesives to leucite-reinforced glass-ceramic.

Methods: Leucite-reinforced glass-ceramic blocks were polished and etched with 9.5% hydrofluoric acid for 1 min. The specimens were assigned to one of four groups based on their surface conditioning (n = 16): 1) NC: negative control with no further treatment; 2) SBU: Single Bond Universal (3M ESPE); 3) ABU: ALL-BOND Universal (Bisco); and 4) PC: RelyX Ceramic Primer and Adper Scotchbond Multi-Purpose Adhesive (3M ESPE) as a positive control. RelyX Ultimate resin cement (3M ESPE) was placed on the pretreated ceramic and was light cured. Eight specimens from each group were stored in water for 24 h, and the remaining eight specimens were thermocycled 10,000 times prior to microshear bond strength evaluation. The fractured surfaces were examined by stereomicroscopy and scanning electron microscopy (SEM).

Results: After water storage and thermocycling, the microshear bond strength values decreased in the order of PC > SBU and ABU > NC (P < 0.05). Thermocycling significantly reduced the microshear bond strength, regardless of the surface conditioning used (P < 0.05). Cohesive failure in the ceramic and mixed failure in the ceramic and resin cement were observed in the fractured specimens. The percentage of specimens with cohesive failure after 24 h of water storage was: NC (50%), SBU (75%), ABU (75%), and PC (87%). After thermocycling, the percentage of cohesive failure in NC decreased to 25%; however, yet the percentages of the other groups remained the same.

Conclusions: Although the bond strength between resin and hydrofluoric acid-etched glass ceramic was improved when universal adhesives were used, conventional surface conditioning using a separate silane and adhesive is preferable to a simplified procedure that uses only a universal adhesive for cementation of leucite-reinforced glass-ceramic.

Keywords: Leucite-reinforced ceramic; Microshear bond strength; Resin cement; Thermocycling; Universal adhesive.

Figure 1

Experimental design of the study.

Figure 2

Percentage distribution of failure modes after 24 h and 10,000 thermocycles. Abbreviations: NC, negative control; SBU, Single Bond Universal; ABU, ALL-BOND Universal; PC, positive control.

Figure 3

Representative SEM images of the fractured ceramic specimens. (A) Within the cemented area in NC (negative control), (B-D) At the interface between the initial cemented surface (area above the dashed lines) and uncemented surface of the ceramic in SBU (Single Bond Universal), ABU (ALL-BOND Universal), and PC (positive control), respectively. Arrowheads (A-C) indicate the junction between the resin cement (RC) and fractured ceramic (FC). Magnification x200.