| ObjectivesTo compare the bonding strength of yttria-stabilized zirconia framework and the according veneering ceramic by pressed and layered veneering technologies,and to observe the microscopic structure with a scanning electron microscope(SEM) and an energy distribution spectrum(EDS) at the bonding interface.MethodsThe zirconia core material was cutted and fired on into twelve rectangular specimens(10mm×5mm×5mm),and the liner was layered in0.10mm thickness. The specimens were divided into two groups randomly(n=6per group). The veneering ceramics(5mm×5mm×5mm)were either pressed or layered to their corresponding rectangular blocks.One bilayered specimen in every group was prepared for scanning electron microscope(SEM) and energy distribution spectrum(EDS) to investigate the bonding conditions. Other specimens were subjected to shear force in a universal testing machine.All results were expressed as mean±SEM and two-sample t-test for independent samples was used to test significance.Results1.The result of the shear bond strength testThe values of shear bond strength test were (20.97±1.14)MPa for the pressed veneering group and (16.41±1.13)MPa for the layered veneering group.The differences between the shear bond strength values of the two groups were statistically significant(P<0.05).2.The result of scanning electron microscopeBy pressed veneering technologies,the result of SEM showed yttria-stabilized zirconia framework and the corresponding veneering ceramic contacted tightly at the interface,and the line was very straight at the interface.Furthermore the structure of the sintered yttria-stabilized zirconia and the pressed veneering ceramic was both compact and well-distributed.By layered veneering technologies,the result of SEM showed yttria-stabilized zirconia framework and the corresponding veneering ceramic contacted tightly at the interface,but the line was not very straight at the interface.While the structure of the sintered yttria-stabilized zirconia was compact and well-distributed,but that of the sintered veneering ceramic was loose and porous.3.The result of energy distribution spectrumBy pressed veneering technologies.the result of EDS showed the content of zirconium increased in the veneering layer and relatively descended slowly at the interface.Otherwise the content of silicon decreased rapidly at the interface.But the content of aluminum descended slowly at the interface, a small quantity of aluminum was detected in the yttria-stabilized zirconia framework.By layered veneering technologies,the result of EDS showed the content of zirconium descended sharply at the interface.and the zirconium was not detected in the veneering layer.While the content of silicon also descended rapidly at the interface,and only a little silicon was detected in the yttria-stabilized zirconia framework.Instead.the content of aluminum descended slowly at the interface,and the aluminum was detected in the yttria-stabilized zirconia framework.ConclusionsThe pressed veneering technology is better in improving the bonding strength of the yttria-stabilized zirconia framework and the veneering ceramics. |
