Abstract
The purpose of this in vitro study was to evaluate the influence of mechanical load cycling (MLC), which simulated mastication, alone or combined with thermal cycling (TC), on the resin shear bond strength (SBS) to zirconia. Two resin cements (Panavia F2.0 and RelyX U200) were bonded (bonding area: 2.38 mm) to air-abraded zirconia (Everest ZS-Ronde). The specimens were subjected to SBS test before and after TC (5000 cycles), MLC (5000 cycles in 37 °C water), TC/MLC, or MLC/TC aging (n = 15). Before SBS test, the mechanical and physical properties of the two resin cements were studied (n = 5). For both resins, unlike TC (p > 0.05), the three MLC-containing aging conditions significantly decreased the SBS values when compared to the non-aged condition (p < 0.05). In the case of MLC-only aging, RelyX U200, with significantly higher hydrophobicity (p = 0.004), showed a significantly higher SBS value than Panavia F2.0 (p = 0.035). The MLC aging-containing groups showed increased occurrence of mixed failure. The application of MLC combined with TC may more closely simulate intraoral conditions.
Highlights
The increasing demand for all-ceramic restorations has led to the development of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) with enhanced mechanical properties such as high flexural strength and high fracture toughness [1,2]
The purpose of this study was to compare the influence of four aging methods (TC or mechanical load cycling (MLC) or their combinations) on the shear bond strength (SBS) of resin bonded to zirconia
The null hypothesis that the aging methods do not differently decrease the SBS of the resin cements to zirconia was partially rejected
Summary
The increasing demand for all-ceramic restorations has led to the development of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) with enhanced mechanical properties such as high flexural strength and high fracture toughness [1,2]. Due to their superior mechanical performance, zirconia-based restorations not requiring high retention may be cemented using non-adhesive luting agents [3]. The initial bonding of the resin-zirconia interface is of importance, the natural aging of the interface needs to be simulated to evaluate long-term adhesion durability and to identify more effective bonding techniques and adhesive materials [7,8]. Long-term water storage at a constant temperature or thermal cycling (TC) are most often used to simulate natural
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