Effect of Grinding and Multi-Stimuli Aging on the Fatigue Strength of a Y-TZP Ceramic

Abstract

This study aimed to investigate the effect of grinding and multi-stimuli aging on the fatigue strength, surface topography and the phase transformation of Y-TZP ceramic. Discs were manufactured according to ISO-6872:2008 for biaxial flexure testing (diameter: 15 mm; thickness: 1.2 mm) and randomly assigned considering two factors "grinding" and "aging": C-control (as-sintered); CA-control + aging; G-ground; GA-ground + aging. Grinding was carried out with coarse diamond burs under water-cooling. Aging protocols consisted of: autoclave (134°C, 2 bars pressure, 20 hours), followed by storage for 365 days (samples were kept untouched at room temperature), and by mechanical cycling (10 6 cycles by 20 Hz under a load of 50% from the biaxial flexure monotonic tests). Flexural fatigue strengths (20,000 cycles; 6 Hz) were determined under sinusoidal cyclic loading using staircase approach. Additionally, surface topography analysis by FE-SEM and phase transformation analysis by X-ray Diffractometry were performed. Dixon and Mood methodology was used to analyze the fatigue strength data. Grinding promotes alterations of topographical pattern, while aging apparently did not alter it. Grinding triggered t-m phase transformation without impacting the fatigue strength of the Y-TZP ceramic; and aging promoted an intense t-m transformation that resulted in a toughening mechanism leading to higher fatigue strength for as-sintered condition, and a tendency of increase for ground condition (C < CA; G = GA). It concludes that grinding and aging procedures did not affect deleteriously the fatigue strength of the evaluated Y-TZP ceramic, although, it promotes surface topography alterations, except to aging, and t-m phase transformation. Effect of Grinding and Multi-S t i m u l i A g i n g o n t h e F a t i g u e S t r e n g t h o f a Y-T Z P C e r a m i c

Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems

“…All the crowns (Zi and ZLS) survived the cyclic fatigue loading in this study, showing only small traces of wear on the occlusal loading surface, with no evident crack lines or fractures. These results corresponded with the observations made in other reports [ 37 , 41 , 48 , 51 ]. A self-adhesive resin cement was used in the current paper for cementation of crowns on the master dies.…”

“…Mechanical aging of the crown specimens did not induce failure in any of the crowns [ 37 , 48 , 51 ], in terms of cracks or other types of fractures. All crown specimens failed under load-to-fracture testing.…”

“…In each of the crown material groups (n = 16), the specimens were sub-divided into eight samples each. One sub-group underwent mechanical aging (MA) by compressive cyclic loading [ 37 , 48 , 50 , 51 ], and the other sub-group, which served as the control, did not undergo any aging process. The compressive cyclic loading of crowns (with occlusal thickness of 1.5–2 mm and rounded occlusal notch design) was performed using an electro-dynamic universal testing machine (UTM) (Instron ElectroPuls E3000, Instron Corporation, Norwood, MA, USA) in unidirectional movements along the long axis of the crown-abutment complex with a 5.0 mm diameter hardened hemi-spherical steel ball indenter centered at the central fossa of the occlusal surface to have a two-point contact, at a cusp angle of 70° [ 28 ] ( Figure 6 ).…”

“…A customized specimen holder device was used to ensure all specimens were placed in the same position for testing. Cemented crown specimens along with their bases were held in position in the loading device and subjected to 500,000 load cycles of 200 ± 50 N at 10 Hz [ 37 , 46 , 48 , 50 , 51 , 52 , 53 ]. The number of cycles used simulated a 2 year functional loading period in the mouth at an estimated rate of 240,000 cycles/year [ 54 , 55 ].…”

Effect of Different Surface Treatments on Shear Bond Strength of Zirconia Based Ceramic and Veneering Porcelain

“…This procedure is used for obtaining a rougher surface, to increase the bonding area either to the inner surface of the restoration or between the core-veneer surfaces. 17 Al2O3 air-borne particle abrasion was done at 0.4 MPa pressure and a grain size of 50 µm as recommended by Nakamura et al 21 who concluded that 50 µm grain sized and 0.4 MPa pressured Al2O3 air-borne particle abrasion will provide a strong adhesive bond between the zirconia infrastructure and the veneering ceramic. In addition, Liu et al 22 found that 0 .35 MPa pressured and 50 µm grain sized air-borne particle abrasion led to a significant different improvement of shear bond strength.…”