Surface Treatment and Cementation of Lithium Silicate Ceramics Containing ZrO2

Objective: To evaluate the effect of different surface treatments on the shear bond strength (SBS) of lithium silicate (LS) and lithium disilicate (LD) ceramics, after thermocycling. Methods and Materials: For SBS test, 72 ceramic blocks (18x14x2 mm) were made (24 blocks from each ceramic material): VITA Suprinity (LSS), Celtra Duo (LSC), and Lithium disilicate (LD). The blocks were polished with sandpaper of increasing grit (#280, #400, #800, and #1200) and embedded in chemically activated acrylic resin. Afterwards, they were randomly divided into 12 groups (6 blocks per group) according to: "Ceramic" (LD, LSC, and LSS) and "Surface treatment" (IIFS: hydrofluoric acid + silane; MEP: Monobond Etch & Prime/Ivoclar). From each treated surface ceramic block, four dual-curing resin cement cylinders (RelyX U200, 3M Oral Care) were prepared using a Tygon tube (0=3 mm and h=2 mm) and light cured for 40 seconds (1000 mW/cm (2)) (N=288/n=24). All specimens were submitted to thermocycling (10,000 cycles, 5 degrees C and 55 degrees C, 30 seconds) and then to SBS test at a crosshead speed of 1 mm/min using a 50-kgf load cell. Forty-five additional blocks were made for roughness and SEM analysis. Failure mode was also performed. The data (MPa) were statistically analyzed by one-way analysis of variance (ANOVA), Tukcy test (5%), and Weibull analysis. The R-a was analyzed by Kruskal-Wallis and Dunn Test (5%). The other variables were analyzed qualitatively. Results: ANOVA revealed that "surface treatment" was significant for all ceramic materials (p<0.05). The LD-HFS (18.66 +/- 3.49), LSC-HFS (16.81 +/- 2.62), and LSS-HFS (16.33 +/- 3.08) groups had significantly higher SBS than the LD-MEP (7.00 +/- 4.2), LSCMEP (14.12 +/- 3.51), and LSS-MEP (13.87 +/- 2.52) groups. Complete adhesive failures at the cement- dentin interface were more frequent. Weibull modulus was superior for the LD-HFS (6.22), LSC-HFS (8.8), and LSS-HFS (7.4) groups. Conclusion: HF followed by silanization is the most suitable surface treatment for the cementation of LS and LD glass ceramics.