Fatigue performance of distinct CAD/CAM dental ceramics

This study investigated the effect of surface roughness (polished vs. CAD/CAM milling roughness simulation) on the fatigue behavior of five dental ceramics for manufacturing CAD/CAM monolithic restorations. Specimens of five dental ceramics (FC- feldspathic; PICN- polymer-infiltrated ceramic-network; ZLS- zirconia-reinforced lithium silicate glass-ceramic; LD-lithium disilicate glass-ceramic; YZ-yttria-stabilized tetragonal zirconia polycrystal), to be tested under fatigue (12 × 12 × 1.2 mm³), were assigned into two groups according to surface treatment: polished 'p' (#2500-grit SiC papers) and CAD/CAM milling roughness simulation 'gr' (grinding with #60-grit SiC paper). The fatigue test was performed through the stepwise method (40N-660N; step of 20N; 10,000 cycles/step; 20 Hz frequency). Roughness, topographic and fractographic analyses were performed. The fatigue data were analyzed by Kaplan-Meier and Mantel-Cox (Log rank), and Pearson correlation was used to correlate roughness vs. fatigue data. CAD/CAM milling roughness simulation led to significantly (p < 0.05) greater roughness (Ra and Rz), promoting a more irregular topography with scratches and grooves, and led to a lower fatigue performance for all the tested ceramics. Fractographic analysis depicted the origin of failure at the higher stress concentration side, the side subjected to tensile tension during the fatigue test. The CAD/CAM milling roughness simulation significantly decreased the fatigue performance of the evaluated ceramic materials.