Effect of Universal Adhesives on Long-term Bond Strength to Zirconia.

PURPOSE: To evaluate the effect of universal adhesives on the long-term bond strength to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). MATERIALS AND METHODS: Polyethylene tubes filled with composite cement containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) were adhesively luted to 60 fully sintered Y-TZP slabs (7 x 7 x 2 mm) with or without (control) previous application of a 10-MDP-based adhesive (All Bond Universal, Bisco) - ABU; Clearfil Universal Bond Quick, Kuraray Noritake - CUB; Scotchbond Universal Adhesive, 3M Oral Care - SUA) on the zirconia surface. The bonded specimens were stored in water for 24 h, 6 months, or 1 year and subjected to microshear bond strength testing. The data were analyzed by one-way ANOVA and Tukey's test (p < 0.05). The contact angle was measured after adhesive application to evaluate surface wettability. The adhesive-treated specimens were analyzed with x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) for chemical characterization. RESULTS: The application of a 10-MDP-based adhesive significantly improved bond strength of composite cement to zirconia when compared to the control group (no adhesive application) (p < 0.05). One-year water storage significantly decreased bond strength for ABU- and CUB-bonded specimens, but not for SUA-bonded specimens. The analysis by XPS and ToF-SIMS showed peaks of carbon, phosphorus, and silicon in all adhesive-treated specimens. CONCLUSIONS: One-year water storage affected the bond strength of composite cement to zirconia when All Bond Universal or Clearfil Universal Bond Quick were used.

Silica deposition on zirconia via room-temperature atomic layer deposition (RT-ALD): Effect on bond strength to veneering ceramic.

PURPOSE: To develop and to characterize a hybrid interface between yttria-stabilized zirconia (Y-TZP) transformed layer and silica-based nanofilm to enable a better bonding between Y-TZP and a veneering ceramic. MATERIAL AND METHODS: Sixty-six fully-sintered rectangular Y-TZP specimens were distributed into 6 groups, according to the surface treatment applied: C (control): no treatment; Al: 27 µm-alumina particle abrasion; Ht: hydrothermal treatment in autoclave for 15h; Si20: 20 cycles of silica deposition using room-temperature atomic layer deposition (RT-ALD); Si40: 40 cycles of RT-ALD; Ht + Si40: hydrothermal treatment followed by 40 cycles of RT-ALD. RT-ALD was performed by the sequential exposure of specimens to vapor of tetramethoxysilane orthosilicate (TMOS) and ammonium hydroxide (NH4OH). Y-TZP surface wettability and shear bond strength (SBS) between Y-TZP and the veneering ceramic were analyzed for all groups after surface treatments. One-way ANOVA and Tukey's HSD test were used for data analysis (p ≤ 0.05). RESULTS: The highest contact angle was observed for the control group (64.46 ± 6.09 θ), while the lowest values (p < 0.001) were presented after Si20 (29.85 ± 4.23 θ) and Si40 (30.37 ± 5.51 θ) treatments. Hydrothermal treatment (49.3 ± 2.69 θ) and alumina abrasion (45.84 ± 4.12 θ) resulted in intermediate contact angle values. The highest SBS values were observed for Al (16.74 ± 1.68 MPa) and Ht (15.27 ± 2.11 MPa) groups (p < 0.018). Groups Si20 (9.66 ± 1.22 MPa), Si40 (9.33 ± 2.11 MPa), Ht + Si40 (9.37 ± 1.02 MPa) and C (12.54 ± 2.64 MPa) all resulted in similar SBS results (p > 0.998). CONCLUSION: The experimental treatments proposed enhanced surface wettability, but shear bond strength between Y-TZP and veneering ceramic was not improved. Alumina particle-abrasion improved SBS values while a decrease in wettability was observed.