Effect of grinding and aging on subcritical crack growth of a Y-TZP ceramic

Abstract

This study aimed to investigate slow crack growth (SCG) behavior of a zirconia ceramic after grinding and simulated aging with low-temperature degradation (LTD). Complementary analysis of hardness, surface topography, crystalline phase transformation, and roughness were also measured. Disc-shaped specimens (15 mm Ø × 1.2 mm thick, n = 42) of a full-contour Y-TZP ceramic (Zirlux FC, Amherst) were manufactured according to ISO:6872-2008, and then divided into: Ctrl - as-sintered condition; Ctrl LTD - as-sintered after aging in autoclave (134°C, 2 bar, 20 h); G - ground with coarse diamond bur (grit size 181 μm); G LTD - ground and aged. The SCG parameters were measured by a dynamic biaxial flexural test, which determines the tensile stress versus stress rate under four different rates: 100, 10, 1 and 0.1 MPa/s. LTD led to m-phase content increase, as well as grinding (m-phase content: Ctrl - 0%; G - 12.3%; G LTD - 59.9%; Ctrl LTD - 81%). Surface topography and roughness analyses showed that grinding created an irregular surface (increased roughness) and aging did not promote any relevant surface change. There was no statistical difference on surface hardness among different conditions. The control group presented the lowest strength values in all tested rates. Regarding SCG, ground conditions were less susceptible to SCG, delaying its occurrence. Aging (LTD) caused an increase in SCG susceptibility for the as-sintered condition (i.e. G< G LTD < Ctrl < Ctrl LTD).

Effect of Cement Layer Thickness on the Immediate and Long-Term Bond Strength and Residual Stress between Lithium Disilicate Glass-Ceramic and Human Dentin

“…Water sorption is also responsible for degradation of resin-based cements [22], and a thick marginal cement layer would be more exposed to the oral environment. In this sense, aging simulations in in vitro studies should be performed to elucidate the long-term bond strength achieved by dental materials and dental tissues [20][21][22][23]. Finite element analysis (FEA) is a numerical method that can be applied to elucidate the effect of polymerization shrinkage on stress; however, it was not performed in association with in vitro measurements of immediate and short-term bond strength.…”

“…However, in addition to the residual stress, the exposed cement layer could expand by water sorption during the aging process [ 19 ] and therefore can present failures such as slow crack growth [ 20 , 21 ], which reduces the survival of composites and ceramics [ 14 , 15 , 16 ]. This phenomenon is responsible for the failure of the majority of dental biomaterials that are placed in the oral environment.…”

Influence of fatigue loading on fracture resistance of endodontically treated teeth restored with endocrowns

“…While VE and EM groups showed no statistically significant differences. Regarding KZ group, the reason for this behavior due to its polycrystalline microstructure providing relatively low resistance to crack propagation [48,49]. In addition, the higher yttria content and grain size in its composition shows more inter grain spaces and present high cubic phase that are less firmly bonded.…”