Effects of Surface Treatments on Mechanical Behavior of Sintered and Pre-sintered Yttria-Stabilized Zirconia and Reliability of Crowns and Abutments Processed by CAD/CAM

Purpose: This study evaluated the micro shear bond strength of resin cement to an yttria-stabilized zirconia ceramic and the survival probability of zirconia abutments and crowns after different surface treatments through a fatigue test. Materials and Methods: The study was divided into two parts. For part 1, 95 zirconia disks were divided into five groups (n = 19): control, untreated, airborne particle abrasion with Al2O3 particles before sintering, airborne particle abrasion with Al2O3 particles after sintering, silicatization before sintering, and silicatization after sintering. Three samples of each group were used for evaluation of surface roughness by confocal laser scanning microscopy and afterward were prepared for surface microstructural analysis by scanning electron microscopy. Ten samples of each group were subjected to micro shear bond strength testing, and the interfaces of the remaining six were examined by scanning electron microscopy. In part 2, 70 external hex zirconia abutments and copings were made by computer-aided design/computeraided manufacturing (n = 14). Marginal fit of abutment/coping was measured in a confocal laser scanning microscope. Afterward, a fatigue test was carried out with progressive load of 80 up to 320 N (40 N steps), 5 Hz frequency, and 20,000 cycles at each step. Thermal cycling was simultaneously performed (5°C to 55°C). Results: The group treated after sintering with SiO achieved statistically higher micro shear bond strength (P .01). Higher failure loads were associated with a combined failure. The surface changes in the group treated with SiO before sintering suggest silica deposition, and there was a lack of homogeneity, which was more evident on the surface of the groups treated before sintering. The marginal gap was higher for the group treated before sintering with SiO (P .01), and the survival probability of the sets was similar for all tested groups (P = .57). Conclusion: The micro shear bond strength to zirconia was improved after silicatization after sintering, but the survival probability of crown/abutment/implant sets was not affected by different surface treatments. Keywords: marginal gap, surface treatment, thermomechanical fatigue, zirconia