This study aimed to evaluate the effect of low and high viscosities of dual-cured
resin cement on the mechanical
fatigue behavior of
yttria tetragonal
zirconia polycrystals (3Y-TZP) and
yttria-stabilized
zirconia (4YSZ) adhesively luted to a dentin analogue (glass fiber-reinforced
epoxy resin). Ceramic discs were randomly divided into four groups (n = 20) based on the following study factors: dual-cured
resin cement viscosities (low and high) and
zirconia microstructure (3Y-TZP and 4YSZ). The discs were treated by air abrasion with
aluminum oxide particles (50 μm), followed by the application of primer, and then luted with high or low viscosity
resin cement to the dentin analogue. Subsequently, the luted sets underwent a step-stress
fatigue test, which involved an initial load of 200 N, step increments of 100 N, 10,000 cycles per step, and a frequency of 20 Hz. Data on
fatigue failure load (FFL) and the number of cycles for failure (CFF) were collected and analyzed using survival tests, including Kaplan-Meier and Mantel-Cox analyses, as well as Weibull analysis. Additionally, topography analysis, fractographic features, bonding interface analysis, and Raman spectroscopy were performed. The results revealed that 3Y-TZP exhibited superior
fatigue behavior compared to 4YSZ, regardless of the viscosity of the
resin cement used for luting. Among all groups, 3Y-Low exhibited the best
fatigue performance, while 4YSZ luted with low or high viscosity
resin cements yielded the lowest
fatigue behavior (FFL). There were no significant differences in Weibull modulus among the groups. After air abrasion, both ceramics showed similar topography. Raman analysis indicated that the surface of 3Y-TZP ceramics prior to sintering had a monoclinic phase, which transitioned predominantly to tetragonal phase peaks after sintering. A similar transition was observed in 4YSZ ceramics. In summary, 3Y-TZP exhibited superior mechanical
fatigue behavior compared to 4YSZ. The influence of
resin cement viscosity on
fatigue behavior was more pronounced in 3Y-TZP, with low-viscosity
resin cement enhancing its performance. However, the mechanical
fatigue behavior of 4YSZ was less affected by the viscosity of the dual-cured
resin cement, showing similar results with both low and high viscosities. In conclusion, 3Y-TZP demonstrated superior mechanical
fatigue behavior compared to 4YSZ. The impact of
resin cement viscosity on
fatigue behavior was more pronounced in 3Y-TZP, with low-viscosity
resin cement enhancing its performance. Conversely, the mechanical
fatigue behavior of 4YSZ was less sensitive to the viscosity of the dual-cured
resin cement, resulting in similar outcomes with both low and high viscosities.