Surface Treatment and Cementation of Lithium Silicate Ceramics Containing ZrO2

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.

For SBS test, 72 ceramic blocks (18×14×2 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" (HFS: 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 (Ø=3 mm and h=2 mm) and light cured for 40 seconds (1000 mW/cm2) (N=288/n=24). All specimens were submitted to thermocycling (10,000 cycles, 5°C and 55°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 oneway analysis of variance (ANOVA), Tukey test (5%), and Weibull analysis. The Ra was analyzed by Kruskal-Wallis and Dunn Test (5%). The other variables were analyzed qualitatively.

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.

HF followed by silanization is the most suitable surface treatment for the cementation of LS and LD glass ceramics.