Abstract
BackgroundTo evaluate the influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces.Material and MethodsAll-ceramic systems tested were lithium disilicate and zirconia veneered by layering technique. Sixty specimens (n=20) were subjected to shear bond strength. Ten of them were thermal and mechanical cycled. Fracture analysis was performed with stereomicroscopy and scanning electron microscopy. Energy dispersive X-ray spectroscopy analysis was performed across core/veneer interfaces.ResultsThermal and mechanical cycling did not influence on bond strength. However, there was significant difference among systems (<0.01). CoCr group presented the highest values, followed by lithium disilicate, and zirconia. Failure modes were predominantly adhesive for CoCr, cohesive in core for lithium disilicate, and cohesive in veneer for zirconia. Energy dispersive X-ray showed interaction zone for CoCr and lithium disilicate groups and was inconclusive for zirconia. Fatigue had no influence on bond strength of groups tested.ConclusionsThe results suggest that there is a chemical bond between core and veneer materials for CoCr and lithium disilicate groups. Key words:Ceramics, electron microscopy, fatigue, mechanical stress, shear bond strength.
Highlights
Lithium disilicate, a reinforced glass ceramic, and yttriastabilized tetragonal zirconia polycrystalline (YTZ-P) have been widely used as materials for core of bilayered restorations [1]
Since no influence of the aging protocol used in the present study was found, it can be concluded that the different interfaces tested resisted the mechanical and thermal stresses to which they were subjected and are able to resist fatigue-challenging situations
The control group (CoCr) showed mean shear bond strength of 34.72 MPa, satisfactory value for metal ceramic interface bond strength according to the International Organization of Standardization that proposed a minimum value of 25 MPa for these systems
Summary
A reinforced glass ceramic, and yttriastabilized tetragonal zirconia polycrystalline (YTZ-P) have been widely used as materials for core of bilayered restorations [1]. The estimated stress at failure for delamination (26.8 MPa) is higher than the calculated zirconia veneer bond strength reported in previous studies using bond strength test (15-24 MPa) [6,7], and suggests that the core-veneer interface is a critical factor for the success of layered restorations. Studies have focused on the bond strength of different ceramic core/veneer combinations and suggest that lithium disilicate have higher bond strength to veneering porcelain compared to zirconia [8,9,10,11]. To evaluate the influence of thermal and mechanical fatigue on the shear bond strength of different all-ceramic cores and veneering porcelain interfaces. Conclusions: The results suggest that there is a chemical bond between core and veneer materials for CoCr and lithium disilicate groups
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