Resin cement coating reverts the machining damage on the flexural fatigue strength of lithium disilicate glass‐ceramic

Abstract This study evaluated the effect of resin cement coating with high and low viscosities on the flexural fatigue strength of machined lithium disilicate glass‐ceramic. Discs (IPS e.max CAD; Ivoclar Vivadent) were prepared and divided according to the surface condition (machining [M]—CEREC inLab; and polishing [P]—laboratory procedures), resin cement coating (with or without), and cement viscosity (high [H] and low [L]). The ceramic bonding surface was etched/primed by a one‐step primer application followed by resin cement application (Variolink N base + high or low viscosity catalyst; Ivoclar Vivadent). Biaxial flexural fatigue strength was evaluated on a piston‐on‐three‐ball set by the step‐test method (n = 15) (initial stress: 60 MPa; incremental steps: 20 MPa; 10,000 cycles/step, at 20 Hz). Weibull statistics were used for fatigue data. Contact angle, topographic, and fractographic analysis were also performed. Machining produced statistically lower contact angle than polishing and a significant detrimental effect on the fatigue behavior (σ₀M = 247.2 [246.9–268.3];σ₀P = 337.4 [297.8–382.4]). Machined groups followed by resin cement coating (σ₀MH = 297.9 [276.0–321.5];σ₀Ml = 301.2 [277.1–327.4]) behaved similarly to the polished and coated groups (σ₀PH = 342.0 [308.9–378.5];σ₀PL = 357.3 [324.7–393.1]), irrespective of the cement viscosity. Therefore, cement coating has able to revert the detrimental effects of the machining on the fatigue strength of lithium disilicate glass‐ceramic. High and low viscosity cements behaved similarly in the improvement of CAD–CAM lithium disilicate fatigue strength.