Color Stability And Adhesive Properties Of CAD/CAM Zirconia Post And Core After Staining

ObjectiveThe personalized aesthetic restoration of teeth has become the mainstream trend nowadays.With the clinical application of CAD/CAM zirconia post and core,the natural tooth color is reproduced by simulating the natural dentin color and staining the CAD/CAM zirconia post and core before the IPS e.max Press cast porcelain restoration,but whether there is any effect on color stability,microleakage and bonding performance after staining has not been reported.MethodsDisc-shaped zirconia post and core were prepared by CAD/CAM technique and divided into control group(n=32)and stained group(n=32)with a total of 64 samples.(1)Twelve randomly selected specimens per group were bonded to10.00 mm diameter IPS e.max Press cast porcelain after accelerated aging by UV light(1,7 and 13 d),hot and cold cycles(5°C to 55°C,5000 and 10,000 r)and artificial saliva immersion(30,60 and 90 d),ten randomly selected samples from each group were measured by Crystaleye spectrophotometer for L*,a*,b*values and calculated color difference values(ΔE)in 1/3 of the specimens before and after aging,and the remaining four samples were observed by swept surface electron microscopy for the surface morphology of the bonding interface between the CAD/CAM zirconia post and core and IPS e.max Press cast porcelain.(2)Each group of 10 randomly selected specimens with a diameter of 6.00 mm IPS e.max Press cast porcelain bonded by aging,using a universal electronic test machine to test the adhesive properties of the samples and statistical fracture mode.(3)The degree of microleakage in the two groups was not statistically different(P > 0.05).Results1.After artificially accelerated aging,the L* values of the two groups of samples gradually decreased and were statistically different(P < 0.05),and the a* and b* values gradually increased and were not statistically different(P >0.05).The ΔE value gradually increased,and after 90 days of artificial saliva immersion,the color difference of the two groups reached a maximum value of2.20 ± 0.22 in the control group and 2.76 ± 0.37 in the stained group,with a ΔE< 3.3 and a clinically acceptable color change.It was observed by scanning electron microscopy that the bonding interface of the stained group showed a few cracks,and the bonding interface of the control group was tightly bound and the cracks basically disappeared.2.The shear bond strength was: control group(6.99 ± 0.47)MPa and stained group(5.52 ± 0.26)MPa,with no statistical difference between the two groups(P > 0.05).The fracture patterns were: mixed fracture predominated in the control group,and bonded fracture and mixed fracture each accounted for half of the fracture in the stained group.3.The degree of microleakage in the two groups was not statistically different(P > 0.05).Conclusions1.In experiments to study color stability,CAD/CAM zirconia post and core can effectively simulate natural dentin color after staining,and after artificially accelerated aging,the color stability is better and the color change is clinically acceptable.2.In the experiments to study the change in bonding properties,staining had no significant effect on the bonding properties of CAD/CAM zirconia post and core.3.No significant effect of staining on microleakage of CAD/CAM zirconia post and core was investigated in the microleakage experiments.