A Study On The Color Difference Between Nano-ceramic And Traditional Ceramic With Different Thickness Of Dentin Porcelain

Objective:To analysis the effect of the thickness of dentin porcelain on the color of the nano-ceramic and the traditional ceramic.The results were expected to provide effective experi -mental reference to apply the nano-ceramic in clinic.Methods:1 Specimens preparation:Making a mold with a plastic syringe of 5ml to control the thickness of the porcelain.Dentin porcelain of A3 color of Vintage(shofu,Japan) for traditional ceramic and Reflex(Weiland,Germany) for nano -ceramic were studied.For each specimen,porcelain powder was mixed with distilled water to form a slurry in the mold,condensed thoroughly,hydrating,forming percelain-blasts,and fired in the same porcelain furnace following the respective manufacturers'recommendations.After being fired,the speci -mens were examined to see whether they had defects or not, such as air bubble or fissure,and so on.Qualified specimens were burnished by the same dental laboratory lathe at the same speed,then flattened every surfaces along the same direction by grinding on 240,400,600,800,1000 and 1500-grit water sand papers.An electronic sliding caliper was used to control the thickness of the specimens.Finally,forty specimens were finished with 10mm in diameter and divided into the traditional ceramic group(A-D) and the nano-ceramic group(A'-D'),the thickness of group A and A' was 0.5mm;the thickness of group B and B' was 1.0mm;the thickness of group C and C' was 1.5mm;the thickness of group D and D' was 2.0mm.Each group have five specimens.Error was controlled between±0.02mm.All the specimens were ultrasonically cleaned,dried and reserved.2 Measurement of surface roughness:A surface roughness tester was used to measure the value of surface roughness(Ra) of every specimen.Three points were respectively selected on the upper and the inferior surfaces,and the mean of the roughness value of the six points was considered to be the surface roughness value of the specimen.3 Measurement of the color of the specimens.A Spectrascan spectrophotometer(PR-650) was used to analyze the color of the specimens in a dark room,black backgroud,with a D₆₅ light source,the illumination was 20001x,45°/0°geometry,at a 45 degree angle.Before evaluation session,the instrument was calibrated against a white working standard.After half an hour of warm-up,the center point of each specimen were measured six times,three times on the upper surface and three times on the inferior surface.Take the mean value as the result of each specimen.Colormetric data were recorded as CIEL^*a^*b^* values.C^*ab respected chroma,â–³E respected color difference between two specimens.All values were analyzed by SPSS 16.0 to compare the difference between each specimen.Results:1 Surface roughness value of each group:the mean value of surface roughness of the traditional ceramic group was 0.270±0.018μm;the mean value of surface roughness of the nano-ceramic group was 0.175±0.015μm.There were statistical differences between the nano-ceramia group and the traditional ceramic group(P＜0.01).2 The color values of the nano-ceramic group and the traditional ceramic group with different thickness of dentin porcelain:the mean value of L^* were:group A 62.172,group B 68.061,group C 70.112,group D 72.133;group A' 64.918, group B' 72.407,group C' 74.072,group D' 74.871.The mean value of a^* were:group A -0.051,group B 0.934,group C 1.786,group D 2.607;group A' -1.041,group B' -0.201,group C' 0.637,group D' 1.393.The mean value of b^* were:group A 8.578,group B 14.937,group C 18.210,group D 20.636;group A' 8.775,group B' 15.193,group C' 17.436,group D' 18.994. Take the value of a^* and b^* into the formulate C^*ab=[(a^*)²+(b^*)²]^1/2 to gain the mean value of C^*ab:group A 8.578,group B 14.966,group C 18.297,group D 20.800;group A' 8.837,group B' 15.195,group C' 17.448,group D' 19.046. Take the mean value of L^*,a^* and b^* into the formulateâ–³E=[(â–³L^*)²+(â–³a^*)²+(â–³b^*)²]^1/2 to gain the value ofâ–³E: group A and B 8.722,group B and C 3.955,group C and D 3.263,group A and C12.617,group A and D 15.522,group B and D 7.201;group A' and B' 9.898,group B' and C' 2.916, group C' and D' 1.907,group A' and C' 12.776,group A' and D' 14.833,group B' and D' 4.802.3 Comparison of the group in the nano-ceramic group and the traditional ceramic group with different thickness of dentin porcelain.The study found that the value of L^*,a^* and b^* of the nano-ceramic group and the traditional ceramic group all increased with the thickness of dentin porcelain becoming thicker,and the differences between them were all statistical with each other(P＜0.05).When the thickness of dentin porcelain increased,the value ofâ–³E of the nano-ceramic group and the traditional ceramic group appearanced:â–³E_AD＞△E_AC＞△E_AB;â–³E_A'D'＞△E_A'C'＞△E_A'B';â–³E_AD-â–³E_AC＜△E_AC-â–³E_AB;â–³E_A'D'-â–³E_A'C'＜△E_A'C'-â–³E_A'B'.4 Comparison of the group between the nano-ceramic group and the traditional ceramic group with the same thickness of dentin porcelain.The value of L^* and a^* had statistical differences between the nano-ceramic group and the traditional ceramic group with the same thickness of dentin porcelain(P＜0.01).When the thickness of dentin porcelain were 0.5mm and 1.0mm,there was no statistical difference on the value of b^* and C^*ab between the nano-ceramic group and the traditional ceramic group(P＞0.05);When the thickness of dentin porcelain were 1.5mm and 2.0mm,there were statistical differences on the value of b^* and C^*ab between the nano-ceramic group and the traditional ceramic group(P＜0.01).When the thickness of dentin porcelain increased,the difference of the value ofâ–³E between the nano-ceramic group and the traditional ceramic group with the same dentin porcelain thickness appearanced:â–³E_A'B'-â–³E_AB＞△E_A'C'-â–³E_AC＞△E_A'D'-â–³E_AD.Conclusion:1 The thickness of dentin porcelain effected the color of the nano-ceramic and the traditional ceramic.2 The nano-ceramic was more bright than the traditional ceramic and the traditional ceramic was more red than the nano-ceramic when having the same thickness of dentin porcelain.The color differences between the nano-ceramic and the traditional ceramic could be discreminated by eyes.3 The nano-ceramic and the traditional ceramic becomed more bright,red and yellow,and the chroma increased when the thickness of dentin porcelain increased.The color of the nano-ceramic changed smaller than the traditional ceramic. The color differences could be discreminated by eyes.