The Influence Of Dentine Porcelain Thickness On Color Of Nano-ceramic And Traditional Ceramic In Metal-ceramic Restorations

Objective:To analysis the effect of the thickness of dentine porcelain on the color of nano-ceramic in metal-ceramic restoration,to compare the differences in color between nano-ceramic and traditional ceramic in metal-ceramic restoration.The results were expected to provide theoretical basis for clinical application of nano-ceramic.Methods:1 Specimens Preparation:48 disks with 10mm in diameter and 0.35mm in thickness were cast by Wax-lost craft.48 disks were randomly divided into eight groups of six.A3 color of nano-ceramic was applied in A,B,C,D.A3 color of traditional-ceramic was applied in A', B', C',D'.All opaques were fired by using twice-fire technique,making sure the opaque thickness was limited to 0.25±0.01mm.All the specimens were ultrasonically cleaned.Put the disk in a home-made mould,control the thickness of the porcelain by using the mould,coating dentine porcelain,sintering in the same porcelain furnace following the respective manufacturers'recommendations.After being fired,all specimens were burnished by the same dental lathe at the same speed,then flattened the surfaces in the same direction by grinding on 240,400,600,800,1000,1200,1500-grit water sand papers,so that the dentine porcelain thickness of groupA-D were 0.5mm,1.0mm,1.5mm,2.0mm,and also the group of A'-D'.After self-glazing and ultrasonic cleaning by distilled water,all the specimens were prepared.2 Roughness measuring:Model TR220 surface roughness tester was used to measure the value of surface roughness(Ra)of every specimen.The sample length was 0.25mm,the forward velocity of sensing needle was 1mm/s.Each specimen was measured three times,averaged. 3 Measurement of the color of the specimens:Using spectrascanPR-650 spectrophotometer to analyze the color of the specimens.Color measurement carried out in the dark room,chose a black background,D65 standard illumination,45°/0°optical geometry conditions,illumination of 2000lx.The measuring point was in the center of the specimen, each specimen was measured three times,averaged.All values were analyzed by SPSS13.0 statistical analysis software.Results:1 Surface roughness value of each group:The mean value of surface roughness of the nano-ceramic in metal-ceramic specimens was 0.049±0.024um.The mean value of surface roughness of the traditional ceramic in metal-ceramic specimens was 0.063±0.021um.There were statistical differences between the nano-ceramic and the traditional ceramic in metal-ceramic group(P<0.05).2 The color data of metal-ceramic specimens in each group:2.1 Nano-ceramic in mental-ceramic specimens group:L*:group A 65.15±0.65,group B 63.98±0.52,group C 62.94±0.54,group D 62.67±0.44. a*:group A 4.19±0.10,group B 3.88±0.12,group C 3.61±0.10,group D 3.44±0.09. b*:group A 21.84±0.87,group B 21.36±0.06,group C 20.88±0.27,group D 19.94±0.60. C*ab:group A 22.24±0.87,group B 21.71±0.04,group C 21.19±0.28,group D 20.23±0.60.2.2 Traditional ceramic in mental ceramic specimens group:L*:group A' 65.90±0.58,group B' 64.68±0.20,group C' 63.69±0.32,group D' 62.73±0.58.a*:group A' 2.84±0.04,group B' 3.38±0.08,group C' 3.75±0.09,group D' 3.85±0.12. b*:group A' 19.45±0.21,group B' 20.11±0.25,group C' 20.66±0.21,group D' 20.60±0.11. C*ab:group A' 19.66±0.21,group B' 20.40±0.23,group C' 21.00±0.20,group D' 21.00±0.12.2.3 The value of△E of each group2.3.1 the value of△E of the nano-ceramic in metal-ceramic specimens group group A and B 1.30,group B and C 1.14,group C and D 1.00,group A and C 2.47,group A and D 3.20,group B and D 1.982.3.2 the value of△E of the traditional ceramic in metal-ceramic specimens group group A' and B' 1.56,group B' and C' 1.19,group C' and D' 0.96,group A' and C' 2.68,group A' and D' 3.51,group B' and D' 2.05.3 Comparison of the group in the nano-ceramic metal-ceramic specimens group with different porcelain thicknessThe study found that the value of L*,a*and b*of the nano-ceramic metal- ceramic group decreased with the increase of dentin porcelain thickness.The research results showed that there was statistically significant difference in Value L* between group A and groups B-D,group B and groups C-D(P<0.05).There was no significant difference in Value L* between group C and group D(P>0.05).There was statistically significant difference in Value a* between group A and groups B-D,group B and groups C-D,group C and group D(P<0.05).There was statistically significant difference in Value b* between group A and groups C-D,groups B -C and group D(P<0.05).There was no significant difference in Value b* between group A and group B,group B and group C(P>0.05).There was statistically significant difference in Value C*ab between group A and groups C-D,group B and groups C-D, group C and group D(P<0.05). There was no significant difference in Value b* between group A and group B(P>0.05).On the value of△E,△EAD>△EAC>△EAB,△EAD-△EAC<△EAC-△EAB.4 Comparison of the group in the traditional ceramic metal-ceramic specimens group with different porcelain thicknessThe study found that with the increase of dentin porcelain thickness,the value of L* decreased,the value of a*,b*and C*ab increased.There was statistically significant difference in Value L* between group A' and groups B'-D',group B' and groups C'-D', group C' and group D'(P<0.05).There was statistically significant difference in Value a*,b*,C*ab between group A' and groups B'-D',group B'and groups C'-D'(P<0.05).There was no significant difference in Value a*,b*,C*ab between group C' and group D'(P>0.05).On the value of△E,△EA'D'>△EA'C'>△EA'B',△EA'D'-△EA'C'<△EA'C'-△EA'B'. 5 Comparison of the nano-ceramic in metal-ceramic specimen group and the traditional ceramic in metal-ceramic specimens group with the same thickness of dentin porcelain.The comparison result showed that there was statistically significant difference in Value L* between group B and group B',group C and group C'(P<0.05).There was no significant difference in Value L* between group A and group A',group D and group D'(P>0.05).There was statistically significant difference in Value a* between group A and group A',group B and group B',group C and group C',group D and group D'(P<0.05).There was statistically significant difference in Value b*,C*ab between group A and groupA',group B and group B',group D and group D'(P<0.05). There was no significant difference in Value b*,C*ab between group C and group C'(P>0.05).The difference△E value of the nano-ceramic and traditional ceramic:△EA'B'-△EAB>△EA'C'-△EAC> EA'D'-△EAD.Conclusion:1 After self-glazing,nano-ceramic has a higher degree of surface smoothness than traditional ceramic.2 When the dentine porcelain thickness increase,the nano-ceramic in metal-ceramic restoration has a low brightness,the chroma decrease,the hue is towards blue and green,the traditional ceramic in metal-ceramic restoration has a low brightness,the chroma increase,the hue is towards red and yellow.3 The color change of the nano-ceramic and the traditional ceramic in metal ceramic restorations shows a trend of decerase,the nano-ceramic shows a better color stability.