Bond Strength of Silane-Containing Universal Bonding Agents to Lithium Disilicate

The purpose of this study was to evaluate the microshear bond strength to lithium disilicate of four silane-containing universal adhesives (SUAs): Scotchbond Universal Adhesive (3M), Scotchbond Universal Adhesive Plus (3M), Clearfil Universal Bond Quick (Kuraray), and Universal Bond II (Tokuyama), with or without the use of a separate silane primer.

Lithium disilicate blocks (IPS e.max CAD, Ivoclar) were sectioned to create 4 equal partitions. Blocks were then crystallized and mounted in polyvinyl chloride (PVC) pipes. The blocks were steam cleaned, subjected to 5% hydrofluoric acid etch, rinsed, and prepared with or without silane application. Resin cement was applied to prepared blocks within standardized silicone tubing matrices and light-cured forming four resin cement specimens per block and twelve specimens per group (n=12). The dual-cure resin cement with and without the use of silane served as a positive and negative control, respectively. The tubing was removed and then the specimens were subjected to 500 thermocycles. The specimens were loaded perpendicularly in a universal testing machine with a shear force until bonding failure. The mean microshear bond strength was calculated per group and analyzed with ANOVA and Tukey's post hoc tests (alpha=0.05). Following testing, each specimen was examined to determine failure mode.

Except for Universal Bond II, an application of silane resulted in a significant increase in bond strength (p<0.05) when using the SUAs. Without the use of a silane, Universal Bond II had significantly greater bond strength (p<0.0001) than all other SUAs. All the SUAs without the use of silane resulted in lower bond strength (except UB) compared to the typical clinical practice of the use of silane alone. Greater mixed and cohesive failures were observed with groups that used silane.

Silane-containing universal bonding agents are being marketed in lieu of silane application on the intaglio surface of lithium disilicate prior to cementation. The results from this study indicate that using SUAs (except Universal Bond II) in this manner may decrease bond strength of the interface between lithium disilicate and resin cement. Key words:Universal bonding agent, silane, lithium disilicate, bond strength.