Shear Bond Strength of Composite Cement to Lithium-Disilicate Glass-coated Zirconia Versus Alumina Air-abraded Zirconia.

Purpose To compare the shear bond strength of composite cement to lithium-disilicate glass-ceramic coated zirconia vs to alumina air-abraded zirconia and to analyze the residual stresses on both of lithium-disilicate glass-ceramic coated zirconia vs alumina air-abraded zirconia specimens. Materials and methods One hundred eighty zirconia disks (diameters 10 mm and 5 mm, 4.5 mm thick) were divided into two groups: lithium-disilicate glass-ceramic coating followed by hydrofluoric acid etching and Monobond N Primer (LiDi) or alumina air-abrasion (AA). For each group, two different sizes of identically pre-treated zirconia specimens were bonded with Multilink Speed Cement. A total of 90 specimens were stored in distilled water at 37°C for 24 h and then assigned to three subgroups (n = 15/test group): 1. short-term test; 2. thermocycling for 5000 cycles; 3. thermocycling for 10,000 cycles. Bond strength was tested in shear mode and results were analyzed using two-way ANOVA, followed by one-way ANOVA and Tukey's HSD (α = 0.05). Failure mode and surfaces were analyzed with optical and scanning electron microscopy. X-ray diffraction was used to analyze t-m phase transformation and residual stresses on mechanically pre-treated LiDi and AA surfaces. Results The LiDi groups recorded higher mean bond strength than AA groups after thermocycling (p 0.05). Most of specimens in AA groups exhibited mixed failure. Alumina air-abraded surfaces exhibited higher residual compressive stresses than did surfaces with a lithium-disilicate glass-ceramic coating. Conclusion Following thermocycling, composite-zirconia bond strength of specimens with a lithium-disilicate glass-ceramic coating was greater than that of alumina air-abraded specimens.