The Effect Of Surrounding Gingival Porcelain On The Different Colors Of Metal Ceramic Prosthesises

Objectives: To investigate the influence of the gingival porcelains on the different colors of metal ceramic prosthesises so as to provide experimental reference to the clinical application of correct color matching and recurring.Methods: 1 Preparation of test piece: Medical finished wax were made to thirty circular metal specimen with 15mm in diameter and 0.7mm in thickness through the casting process.30 test piece were randomly divided into 6 groups,each of which had 5 test piece .A2 opaque was coated on groups A and a ;D2 opaque was coated on groups B and b;VR2 opaque was coated on groups C and c. All opaque porcelain was sintered twice. All the thickness of opaque porcelain was controlled at 0.30±0.02mm. Gingival porcelain and ceramic body follows an order of sintering:experimental groups:group A:A2 ceramic body and dark gingival porcelain;group B:D2 ceramic body and dark pink gingival porcelain;group C:VR2 ceramic body and dark gingival porcelain.Control groups:group a:A2 ceramic body; group b:D2 ceramic body; group c:VR2 ceramic body.The thickness of all ceramic body and gingival porcelains was controlled at 1.1±0.02mm.The sintering numbers of all samples were consistent. All the surfaces of the specimens were polished in the same way,after the glazing by itself and ultrasonic cleaning by distilled water,all the specimens were elected to prepared. 2 Roughness measurement:Three poins of each specimen were elected to measure.The average value of the three poins was roughness value of the specimen . 3 Color measuring of samples: measuring instruments: SpectrascanPR-650 spectrophotometer, which was in the dark room,with a D65 light source,45°/0°geometry, and a 45 degree angle. After half an hour of prehenting,the instrument was calibrated against a standard whiteboard ,and then the measurement began.Control groups regard center point(O) as the test point;experiment groups regard center point(O) and edge point(G) which was 10mm away from center point as the test point. Each test point was measured three times,and then the mean value was took as the result of each point. The results of measurement were recorded as CIE-LAB values. Analysed the datas by SPSS13 statistical analysis software.Results: 1 The roughness (Ra) of each group was among 0.2-0.4, and there were no statistical differences among groups.2 Compared to control group ,the colors of three color series of dentins with surrounding dark pink gingival porcelain were changed:There were a decrease in L* b* C*ab and H0ab and an increase in a*. There were differences statistically apart from b* C*ab and of VR2 groups by t test(P<0.05).3 There was certain relationship between three color series of dentins and dark pink gingival porcelain in L* b* and C*ab apart from a*and H0ab by factorial design ANOVA.In another word ,ΔL*Δb*ΔC*ab there were difference statistically among three color series of dentins (P<0.05).there were difference statistically among three color series of dentins (P<0.05).In numerus , the degrees of diffence for L*(ΔL*):A2 was similar with VR2,which was larger than D2;the degrees of diffence for C*ab (ΔC*ab): A2 was similar with D2,which was larger than VR2.ΔL*was larger obviously than other color values. The color differences(△E CIE) of between experimental groups and control groups were:VR2 groups: 3.63NBS,A2 groups: 3.51 NBS,the smallest wasD2 groups: 2.16NBS.The decrease of L*was the main body in the composition of△E CIE.4 Compared to O which is near to gingival porcelain , the color values of G which is far from gingival porcelain were changed : There were an increase in L*,b*,C*ab and H0ab and a decrease in a*.Conclusion: 1 Under the influence of gingival porcelain,the colors values of different color series of dentins changed to a certain extent.2 Under the influence of gingival porcelain,the degrees of colors diffence were distinct for different color series of dentins: the degrees of diffence of value and chroma are not identical completely;The degrees of decrease of H0ab may be different .3 Under the influence of gingival porcelain, the higher the value was,the more influences were;the more the red compoment was ,the lesse influences the chroma were.The value was much more influenced.ΔL*was the main body in the composition of△E CIE4 From the△E CIE., under the influence of gingival porcelain, the△E CIE.of VR2 was the largest,the△E CIE.of D2 was the smallest.5 The nearer to gingival porcelain it was,the more easily influenced the dentin was.