| PurposeZirconia all-ceramic material has good aesthetic effect, biocompatibility, electrical insulating properties, resistance to corrosion and wear resistance, so it can maintain good status in complex oral environment. For this, it become one of the ideal dental materials, and is widely applied in clinical practice. Zirconia restorations are bonded to the surface of abutment by a bonding resin. And rational selecting of the internal clearance thickness reservations of zirconia ceramic and using the bonding resin is the primary factor which influences the bonding strength between the all-ceramic material and abutment. Aim of the study was to evaluate the accuracy of marginal and internal fit of the zirconia copings manufactured by two different computer-aided design (CAD)/Computer-Aided Manufacturing (CAM) system on the implant abutment and compare the effect of different bonding thickness on shear bond strength (SBS) of three adhesive luting cements to zirconia ceramic. As a reference for clinical to determine the internal clearance thickness reservations of zirconia ceramic restoration and the selection of cements.Materials and Methods1. Using different scanning mode, five Procera(?) zirconia copings and the same number of Lava zirconia copings were fabricated on the same implant abutment, compared with five precious metal copings fabricated by traditional method. Fifteen abutment replica were made with die-stone and the copings were randomly cemented on them, then they were sectioned and invested. The marginal,shoulder,occlusal and axial fit of each sample was measured by a scanning electron microscope (SEM).2. Ninety-six ceramic blocks with the size of7mm×10mm×10mm were fabricated from zirconia ceramic. Ceramic blocks were randomly assigned to six groups (n=8) according to different adhesive luting cements and bonding thickness. All zirconia ceramic blocks were cemented with Glass Ionomer Luting Cement (GroupG), RelyX Unicem (GroupR) and Embrace Wetbond Resin Cement (GroupE) respectively in50μm and100μm bonding thickness groups. After water storage at37℃for24h, the specimens were submitted to a bond strength test at a crosshead speed of2.0mm/min. Values were recorded with a universal testing machine and the surface appearance of different groups were observed by Field emission scanning electron microscope(FE-SEM) after shear test. Bond strength data (MPa) were analyzed statistically using SPSS16.0.Result1. There was no significant difference in marginal and axial fit among the three groups (P>0.05). Significant difference in occlusal fit was found among the three groups (p<0.05), Lava group showed better fit than the others (p<0.05), and Procera(?) group showed better fit than the control (p<0.05).On shoulder, Lava group showed better fit than the others(p<0.05), there was no significant difference between Procera(?) group and precious (P>0.05).2.The shear bond strength of Group G, Group R and Group E were (7.39+0.82,22.24+5.18,30.94+3.30) Mpa in50μm bonding thickness group and (5.14+0.74,14.81+2.15,25.37+4.21) Mpa in100μm group respectively. The statistical analysis showed that the shear bond strength in50μm group were no significant differences between Group G and Group R (p>0.05);but Group E were higher than Group R and Group R (p<0.01); In100μm group, there were significant differences among three groups (p<0.01); The shear bond strength of Group G and Group R in50μm group were higher than100μm group(p<0.01); The shear bond strength of Group E in50μm group were higher than100μm group (p<0.05).Conclusions1. Under the conditions of this study, the two kind of zirconia copings had clinically acceptable marginal and internal fit, internal fit of zirconia coping would be affected by different manufacture techniques.2. Different adhesive luting cements on the shear bond strength of zirconia was different. The shear bond strength of the same kind of cements to zirconia ceramic was reduced while the bonding thickness increase. |
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