Flexural fatigue strength of CAD/CAM composite material and dual-cured resin luting cements

Purpose: To evaluate the flexural strength and flexural fatigue strength of a CAD/CAM composite and three resin luting cements. Materials and Methods: Specimens of CAD/CAM composite (2x2x25 mm) were fabricated from a composite block (GN-I) using a low-speed cutting saw. Similar specimens of three dual-cured resin luting cements, Linkmax HV, Panavia Fluoro Cement, and RelyX ARC were polymerized in a laboratory-photo-curing unit (Triad II). Flexural strengths were measured at a cross-head speed of 1 mm/minute in 4-point bending (span = 20 mm; distance between inside loading points = 10 mm). The cyclic fatigue test was performed at 1.0 Hz on a fatigue tester. The staircase method was employed using a 10,000 cyclic load limitation, 5 MPa stress increment, and 20 specimens for each material. The initial test was performed at approximately 50% of the mean flexural strength. Results: The flexural fatigue strength results followed the same relationship as those of the static flexural strength, and all mean values were statistically different between the four materials. The ratio of the fatigue strength to the flexural strength ranged from 0.5-0.7, with the dual-cured resin luting cements being lowest.