Comparative Study Of Two Kinds Of Zirconia Copings Marginal Adaptation

Objectives By using double-color silicone rubber to copy the internal space of crown,and computer scanning measurement methods, to explore the marginal and internaladaptation of domestic and imported billet zirconia ceramic zirconium oxide ceramiccopings, to evaluate gingival health status of patients wearing CAD/CAM zirconiaall-ceramic crowns of different substrates, to provide theoretical basis for clinical choiceof zirconia all-ceramic crowns.Methods1The research of marginal adaptation①specimen design and production:using software ProE5.0to design and simulate premolar crown preparatory body, thedigital model specifications were high-6mm, occlusal surface diameter5mm, degree ofpolymerization of6°,120°obtuse angle inside shoulder, shoulder width1mm, highbase4mm; entering the model data into the open CAD/CAM system; cuttingtitanium-generation type1; scanning with the digital scanner titanium-generation type toobtain three-dimensional data and the computer would automatically record results of thescanning; according to the results of the scanning, designing zirconia copings. Therequirements of basal crown were thickness0.6mm, the thickness of the neck edge overgap material set30μm, respectively lathe cutting bur grinding zirconia domestic andimported pre-sintered zirconia ceramic blanks, making5of two kinds of zirconia copingsrespectively, then sandblasting, cleaning and setting aside; putting processed zirconiacopings on pure titanium body in place; after checking the adaptation, using the yellowlight-body silicone rubber （DMG）instead of cement bonding to bond the copings;removing solidified zirconia copings; putting mixed blue light-body silicone rubber（Coltène）into a specific tray and then putting the preparatory body into it; taking it outafter solidification of the rubber, and then filling the blue light-body silicone rubber（DMG）into the space occupied by the preparatory body; finally finishing siliconerubber models.②specimen measuring: scanning the profiles with micrometermeasurements scanner, using image analysis software AutoCAD2014to measure thethickness of gap; using SPSS17.0software for T-test experiment of data.2Clinical research: Selecting different CAD/CAM Zirconia all-ceramic crowns,119 cases of each crown, produced from January2012to December2012; reviewing andrecording the crown integrity and health of the gums after use of one year; using SPSS17.0software for chi-square test of experimental data.Results1The average data of crown marginal gap: imported ceramic zirconia copingsblanks were（62.54±4.65）μm, domestic zirconia copings porcelain blanks were （70.22±5.12）μm（P <0.05）.2The average of crown internal clearance: imported ceramiczirconia copings were（111.58±4.22）μm, domestic zirconia ceramic were（117.37±4.39）μm（P＞0.05）.3Gingival health status: among those wearing imported zirconiaall-ceramic crowns porcelain blanks,4patients suffering from gingivitis while there are7patients wearing domestic zirconia ceramic blanks, the prevalence being3.6%and4.6%,respectively. The difference is not statistically significant（P>0.05）.Conclusions1Two edges and internal gaps of zirconia copings were within clinicallyacceptable limits. Compared with domestic zirconia ceramic copings, the imported had abetter marginal adaptation.2Clinically, two zirconia crowns had lower incidence ofgingivitis, and the contrast between the two was not statistically significant. Two zirconiaall-ceramic crowns stimulated the gums little and were suitable materials for clinicalrestoration of full crowns.