| Objective:Select a domestic transparent zirconia as the research object.To investigate the effect of thickness on the curing properties of self-adhesive dual-cure resin cement,and to study the bonding properties of transparent zirconia and self-adhesive dual-cure resin cement with different thickness and light duration,in order to provide a certain reference for the bonding of clinical domestic transparent zirconia restorations.Method:In this experiment,domestic transparent zirconia(TT,Upcera)and commercial selfadhesive dual-cure resin cement Multilink Speed were selected as the research objects.Transparent zirconia ceramic were sintered according to the standard sintering procedure recommended by the manufacturer.The final size of production was 10mm×10mm.Forty nine transparent zirconia tiles of 1 mm,1.5 mm and 2 mm thickness respectively,a total of 147 pieces,were used for the two part experiments.Specific experimental procedures are as follows:Experiment one:One piece of each of the above transparent zirconia ceramic with different thickness was randomly selected.One control group and three experimental groups were divided according to the coverslips and transparent zirconia ceramic plates of 1mm,1.5mm and 2mm.The Multilink Speed were filled in cylindrical silicone molds(inner diameter 4mm,height 1.5mm)to make samples.Then the samples were illuminated for 20s through the coverslips and the selected transparent zirconia ceramics with the thickness of 1mm,1.5mm and 2mm,respectively.Twelve resin cement samples were prepared for each group.The cured samples were randomly divided into two subgroups after being stored in a dark constant temperature water bath at 37℃ for 24 h.One subgroup used Fourier transform infrared spectroscopy to determine the polymerization degree(DC%),and the other subgroup was determined by Vickers-hardness(HV).One-way analysis of variance was used to test the statistical data.The significance level was P=0.05.Experiment two:The remaining 144 transparent zirconia ceramic tiles were sandblasted on one side.After sandblasting,the tiles were divided into three large groups according to their thickness,and each group was randomly divided into three subgroups with a length of 20 s,40 s and 60 s for light curing through the cover transparent zirconia.Sixteen transparent zirconiaresin cement bonding specimens were made for each group.Bonding specimens were randomly divided into two subgroups to be embedded after being stored in a dark constant temperature bath at 37℃ for 24 h.The immediate and thermal cycling aging shear bond strength were tested respectivel,and the fracture mode of adhesive interface was analyzed.The experimental data were statistically tested by two-factor analysis of variance.The significance level was P=0.05.Result:1.The results of polymerization conversion analysis showed that the polymerization conversion of resin cement polymerized under 2 mm thick domestic transparent zirconia ceramics was significantly lower than that of the control group、1 mm and 1.5 mm thickness groups(P<0.05).There was no significant difference among the other groups(P>0.05)(69.7%±4.8%in the control group,68.9%±8.6%in the 1 mm group,67.1%±6.3%in the 1.5 mm group,51.7%±4.7%in the 2 mm group).The results of microhardness analysis show that there were no statistical difference in the microhardness of resin cement with the thickness of 1 mm,1.5 mm,2 mm and control group(P>0.05)(47.9±2.4 MPa in control group,47.0±4.1 MPa in 1 mm group,46.2±4.1 MPa in 1.5 mm group and 44.0±1.7 MPa in 2 mm group).2.The results of immediate bond strength analysis showed that the ceramic thickness factor has a significant impact on the bond strength(P<0.05).Under 20 s light exposure,the bond strength of the 1.5 mm and 2 mm thick groups was significantly lower than that of the 1 mm group(P<0.05)(9.33± 1.23 MPa in the 1 mm 20 s group,6.67 ± 1.22 MPa in the 1.5 mm 20 s group,and 6.32 ±1.83 MPa in the 2 mm 20 s group).The light duration factor has a significant impact on the bond strength(P<0.05).At the thickness of 1.5 mm and 2 mm domestic transparent zirconia ceramic,the bond strength of transparent zirconia-resin cement specimens cured by light for 20 s was significantly lower than that of the extended light 40 s and 60 s groups(P<0.05)(6.67±1.22 MPa in the 1.5 mm 20 s group,8.83 ± 0.81 MPa in the 1.5 mm 40 s group,9.69 ± 0.52 MPa in the 1.5 mm 60 s group,6.32 ±1.83 MPa in the 2 mm 20 s group,9.09±1.07 MPa in the 2 mm 40 s group,and 9.10±1.40 MPa in the 2 mm 60 s group).The results of aging bond strength showed that there were no significant difference between groups with different thicknesses and light duration(P>0.05).Conclusion:1.Increasing the thickness of domestic transparent zirconia can reduce the polymerization conversion rate of self-adhesive dual-cure resin cement,but has no significant effect on the microhardness.2.The increase of thickness will reduce the immediate bond strength of domestic transparent zirconia and self-adhesive dual-cure resin cement,and the extension of light will improve the immediate bond strength.The ceramic thickness and light duration have no significant impact on the aging bond strength of the domestic transparent zirconia and selfadhesive dual-cure resin cement.This suggests a clinical consideration of the effect of ceramic thickness and duration of light on bonding. |
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