The Influence Of Different Resin Luting Cements On The Resultant Color Of IPS E.max CAD Porcelain Crown

Objective:The IPS e.max CAD system is a new type of lithium silicate glass ceramic launched by Ivoclar Company on the basis of the IPS EmpressⅡin 2005.The IPS e.max system still preserves a better translucent nature though strength has been substantially improved.In this study,we investigated the effects of three different resin luting cements on the final color of IPS e.max CAD ceramic crown,in order to guide clinicians to choose the resin luting cement which can best present the optimum aesthetic effect of the restorations.Content and Methods;1.Specimens Preparation1.1 Using CEREC AC CAD/CAM system to make IPS e.max CAD LT A2 casting porcelain pieces into 48 circular ceramic pieces(with diameter of 10mm,thickness of1.5mm).Then put the ceramic pieces into a porcelain furnace and fire 20 minutes to promote crystallization.After that all the specimens were flattened with sandpapers,cleaned by ultrasonic devices and dried to be used.The thickness of the specimens were controlled by an electronic external micrometer and error was controlled within±0.02mm.Substantly,the specimens were randomly divided into 6 groups,and each group containing 8 specimens:group 1 was the control group without adhesive;group2 was bonded with U200;group 3 with Kerr NX3 Clear;group 4 with Kerr NX3White;group 5 with Superbond Clear and group 6 with Superbond Radiopaque.1.2 Except for group 1(control),the other five groups strictly obeyed the instructions of the three kinds of resin luting cements which were sufficiently painted on the surface of the specimens.Afer the full curing of resin cements of the 5experimental groups,the specimens’adhesive surface was polished by sandpapers until the thickness of the specimens was 1.7 controlled by an electronic external micrometer,and the thickness of resin luting cement was 0.2mm.The specimens were then cleaned by distlled water,dried and spared.2.Measurement of the color and statistic analysis:The color of all specimens were measured by the 3NH NR110 colorimeter and subsequently converted to CIE L~*a~*b~*values.Each specimen was measured for three times and the average value was obtained.The value difference(ΔL~*)and color difference(ΔE)between the control group and experimental groups were measured,respectively.The results were statistically analyzed by SPSS 17.0.Results:1.The value difference(ΔL~*)of test pieces in the sixth group(superbond Radioplaque)was relatively large,while the value difference of resin luting elements in the other four groups was relatively small.2.The color differenceΔE between the experimental groups and control group were all greater than 1.5NBS,which was clinically discernible to the naked eyes.The color difference(ΔE)between the sixth group(superbond Radioplaque)and the control group,the fourth group and the control group were greater than 2NBS.The color difference(ΔE)caused by different resin luting elements of the second group(U200),the third group(Kerr NX3 Clear)and the fifth group(Superbond Clear)was small,with the smallestΔE between the second group(U200)and the control group.3.With variance analysis we concluded that result of the color differenceΔE between the experimental groups and control group was statistically significance(P<0.05).ConclusionThe three frequently clinical used resin luting cements can cause effect discernible to the naked eyes on the color of the IPS e.max CAD all ceramic crown.The Superbond Radioplaque caused the biggest color difference(ΔE),while U200 caused the smallest one,which provided reference to the clinical anterior esthetic prosthodontics.