The Influence Of Different Proportion Of The Porcelain Stain On The Shade Of The Metal-porcelain Prostheses Of Tetracycline Stained Teeth

Objective: The aim of this study is to blend different proportion of theShofu Vintage Brown stain porcelain to the Shofu Vintage D₂body porcelainby internal staining, in order to simulate varying degrees color of thetetracycline stained teeth, then analysis the shade data through the digital coloranalysis system. All above can provide data and theory evidence for Computercolor selection of tetracycline stained teeth and the choice of the proportion ofthe stain porcelain when make the metal-porcelain prostheses by internalstaining.Method:1Specimens preparation: make36of round wax pattern whose diameteris10mm and the thickness is0.5mm with wax patters of0.5mm. Then plantthe sprue according to the condition to cast the Co-Cr alloy group, embed withphosphate, the wax patterns were eliminated by heat and replaced by Co-Cralloy to form round Co-Cr fundus, using the investment thermal expansiontechnical. Take out the cast when it become cooling after finish, cut off thesprue and polish the specimens smoothly. Surfaces of the specimens thatwould receive the ceramic layer were air abraded with airborne particleabrasion with100-μm aluminum oxide, This was done at an angle of45°for20seconds, and from a distance of approximately2cm under0.5bar pressure.Ultrasonically clean the specimens twice with distilled water,5minutes foreach time, standby after intensive drying. Divide the Co-Cr fundus into sixgroups （A-F） randomly, six for every group. All Shofu Vintage PD₂O opaqueporcelain were fired by using twice-fire technique, sintering in the sameporcelain furnace following the respective manufacturers’ recommendation,then grind the opaque porcelain layer to0.3mm along the same direction after sintering, the error should be controlled within the limits of±0.01mm.Match the Shofu Vintage D₂body porcelain on the specimens of group A, usethe group A to be the control group; Blend the Shofu Vintage Brown stainporcelain and the Shofu Vintage D₂body porcelain according to the massratio as1:13,1:11,1:9,1:7,1:5, and mix the material uniformly with specialequipment. Match the blended porcelain on the specimens of groups B-Fseparately, these five groups are used to be the internal staining group. Sinterthe specimens of the six groups, after that, all specimens were burnished bythe same dental lathe at the same speed, then flattened the surfaces in the samedirection by grinding on240,400,600,800,1000,1200,1500-grit water sandpapers, Thickness of the dentin porcelain （1mm） was standardized in anelectronic caliper, the thickness of the dentin porcelain is1.5mm, the errorshould be controlled within the limits of±0.01mm, ultrasonically clean thespecimens for5minutes, then self-glaze once.2Roughness measuring: Model TR220surface roughness tester was usedto measure the value of surface roughness （Ra） of every specimen. The samplelength was0.25mm, the forward velocity of sensing needle was1mm/s.Eachspecimen was measured three times, averaged.3Measurement of the color of the specimens: measure the surface colorof the specimen through the OLYMPUS Crystaleye, the measure should beconducted with the appropriative cassette matched to the OLYMPUSCrystaleye, the background of the cassette is black, and the OLYMPUSCrystaleye uses spectrascanPR-650spectrophotometer to analyze the color ofthe specimens, D65standard illumination,45^°/0^°optical geometry conditions,illumination of2000lx. Measure and analyse the color of the specimens usingthe OLYMPUS Crystaleye, and the center of the specimens should be themeasure location, three times for every specimen, obtain the mean value. Theresult is signified by the CIE1976-L^*a^*b^*shade system.4Statistic analysis: use the SPSS13.0software to conduct statisticalanalysis with the data of the surface roughness and the color. Results:1Surface roughness value of each groupThe mean of surface roughness of each group was：group A0.171±0.023,group B0.188±0.018,group C0.173±0.024,group D0.179±0.020,group E0.185±0.020,group F0.182±0.021.There was no significantdifference among these groups（P>0.05）.2Color data of each group2.1Shade value of each group: the values of L*were: group A72.13±0.09, group B56.77±0.02, group C54.85±0.09, group D54.03±0.07,group E50.67±0.07, group F47.62±0.09; the values of a*were: group A1.29±0.03, group B7.01±0.05, group C7.23±0.04, group D7.37±0.02,group E8.01±0.03, group F8.12±0.03; the values of b*were: group A17.85±0.14, group B25.89±0.07, group C25.72±0.09, group D25.34±0.07, group E25.24±0.14, group F24.76±0.21.2.2â–³E value of each group：△E between group A and group B was18.25,â–³E between group A and group C was19.89,â–³E between group Aand group D was20.50,â–³E between group A and group E was23.67,â–³Ebetween group A and group F was26.37;â–³E between group B and group Bwas1.95,â–³E between group B and group D was2.82,â–³E between group Band group E was6.23,â–³E between group B and group F was9.30;â–³Ebetween group C and group D was0.92,â–³E between group C and group Ewas4.30,â–³E between group C and group F was7.37;â–³E between group Dand group E was3.45,â–³E between group D and group F was6.50;â–³Ebetween group E and group F was3.10.3Comparison of the shade data between different groups3.1Comparison of the groups in the internal staining groups B^F and thecontrol group A：With the addition of stain porcelain，the values of L^*weredecreased，the values of a^*were increased，the values of b*were increased.The ANOVA showed that there was significant difference in the values of L^*between the group B and group A, the group C and group A, the group D andgroup A, the group E and group A, the group F and group A（P<0.05）; there was significant difference in the values of a*between the group B and groupA, the group C and group A, the group D and group A, the group E and groupA, the group F and group A（P<0.05）; there was significant difference in thevalues of b*between the group B and group A, the group C and group A, thegroup D and group A, the group E and group A, the group F and groupA（P<0.05）. There was significant difference in the values ofâ–³E between theinternal staining groups and the control group（P<0.05）,the result showed thatâ–³EAF>â–³EAE>â–³EAD>â–³EAC>â–³EAB.3.2Comparison between each internal staining group B^F: With theproportion of stain porcelain becoming higher， the values of L^*weredecreased，the values of a^*were increased，the values of b*were decreased.The ANOVA showed that there was significant difference in the values of L^*between group B and C、D、E、F, group C and D、E、F, group D and E、F, group E and F（P<0.05）; there was significant difference in the values of a*between group B and C、D、E、F, group C and D、E、F, group D and E、F, group E and F（P<0.05）; there was significant difference in the values of b*between group B and D、E、F, group C and D、E、F, group D and F, group Eand F（P<0.05）; there was no significant difference in the values of b*betweengroup B and C, group D and E（P>0.05）.4The research result of proportion of stain porcelain. When the shaderange of the tetracycline stained teeth is greater than56.77, the proportion ofthe Shofu Vintage Brown stain porcelain and the Shofu Vintage D₂bodyporcelain should be less than1:13; When the shade range of the tetracyclinestained teeth is54.85⁵6.77, the proportion should be1:11¹:13; When theshade range of the tetracycline stained teeth is54.03⁵4.85, the proportionshould be1:9¹:11; When the shade range of the tetracycline stained teeth is50.67⁵4.03, the proportion should be1:7¹:9; When the shade range of thetetracycline stained teeth is47.62⁵0.67, the proportion should be1:5¹:7;When the shade range of the tetracycline stained teeth is less than56.77, theproportion should be greater than1:5. Conclusion:1Compared with the control group, the groups of internal stainingshowed that the lightness decreased, the color of samples trended to yellowand red.2Among the groups of internal staining, along with the proportion ofstain porcelain increased, the lightness of the samples decreased, the trend ofthe color of samples trended to red increased，the trend of the color of samplestrended to yellow decreased.3It can lead to a wide range for the Shofu Vintage Brown stain porcelainto change the lightness of the metal-porcelain prostheses.