Reuse of lithium disilicate ceramic for CAD / CAM: effect of multiple cycles and surface treatment on the bonding strength durability to resin cement.
shear strength, CAD-CAM, ceramic
Objective: investigate the effect of reusing CAD/CAM blocks of lithium disilicate (LT) ceramics after 1 and 3 cycles, surface treatment (hydrofluoric acid-HF or Monobond Etch & Prime -MEP), and thermocycling (with and without TC), in adhesion to resin cement. Materials and methods: 72 blocks of lithium disilicate (DL) (E.max CAD, Ivoclar Vivadent), will be made in the dimensions of 14x12x2mm. For this, ceramic residual from sintered DL CAD will be heat pressing by the lost wax technique 1 and 2 times, obtaining the 1st and 3rd cycles respectively. Unpressed sintered blocks will be used as a control group (C). All blocks will be included in chemically activated acrylic resin and divided into 18 groups (4 blocks per groups) according to the factors: “Reuse cycles” (C, 1 cycle and 3 cycles) “surface treatment” (HF20s and HF120s and MEP) and “thermocycling” (with and without). After treatment, on each treated block surface, four cylinders (Ø2mm) of dual resin cement (Allcen Dual, FGM) will be made and light cured for 40s (N = 270 / n = 15). Half of the samples from each group will be subjected to thermocycling (10,000 cycles, 5-55 ° C, 30s) and will be subjected to the shear bond strength test (SBS- 100KgF, 1mm / min). Failure, wettability, roughness, SEM, EDS and DRX analyzes will also be performed. The SBS (MPa) data will be analyzed using 3-factor ANOVA, Tukey's test (5%) and Weibull analysis.