| Objective: This experiment is to use dental computer aided design and computer aided manufacture(CAD/CAM)technology,making three unit posterior fixed bridge of zirconia,zirconium fixed bridge abutment connection influence body with different shoulder width on the strength of fixed bridge,through the experimental data of preparation and repair clinical dental zirconia fixed bridge system to provide reference.Methods:1 Manufacture of base and abutmentThrough the design of the base of the standard mandibular model and abutment teeth,the tooth preparation was carried out according to the principle of Prosthetic Dentistry.The model was selected as the three unit fixed bridge with the right lower first molar missing,the right lower first premolar and the second molar as the abutment teeth.The abutment tooth preparation standards: occlusal surface uniform grinding 1.5mm,axial grinding 1.0mm,axial surface polymerization degree is8 degrees,right shoulder blade shaped or obtuse angle subgingival inside,each part without undercut,no stress concentration zone.According to the experimental design of right mandibular two premolar the shoulder width is1.0mm,the lower right shoulder width of two molars were bladed,0.5mm,1.0mm.2 Metal mold makingThe base and abutment by addition of silicone impression material preparation impression,choose special casting wax with a ratio of 1:1processing base and abutment wax type,conventional embedding,casting,polishing,sandblasting finished metal model.3 Preparation of prosthesisAfter the metal base and abutment generation type addition silicone rubber composite by imitating the periodontal ligament,fixed on the scanner observation platform with plasticine,using 3Shape TRIOS 2 3D digital scanning optical impression model preparation,then import the data into3 shape Dental System software,the system will automatically generate the standard form of restoration.According to the third edition < oral anatomy and physiology > of right of mandibular second premolar,first molar and the second molar shape description,using virtual adjustable knife trimming to the required thickness of 1.5mm occlusal surface thickness,axial wall thickness is1.0mm,nearly rectangular connector cross-sectional area is 16mm2.The connecting occlusal,and gingiva buccal and lingual embrasure of the "U" type,the radius of curvature is 0.90 mm,and the crown at the edge of the metal shoulder are smoothly connected.All ceramic fixed bridge right mandibular two premolar shoulder width is 1.0mm,the lower right two Molar width of shoulder were bladed,0.5mm,1.0mm,and then the data is transmitted to CAM cutting machine.The match porcelain processing 18 zirconia fixed bridge.Grouping: the width of shoulder blade shape,the lower right two molar 0.5mm,6 1.0mm,respectively,A B,C group.4 Experimental study on compressive failureThe fixed bridge made of zirconium with DMG resin cement were glued to the metal type,acupressure in place,in the vertical force of 50 N continuous pressure for 10 minutes,remove excess cement,37 degrees in the distilled water storage after 24 hours standby.The zirconium bond bridge in good order in the universal testing machine for strength test,loading head with constant speed vertical loading 0.5mm/min on the metal occlusal pad silicone rubber cushioning material on the bridge,until the whole zirconium fixed bridge is destroyed,the record number.5 Statistical analysisThe experimental data were statistically analyzed with KolmogorovSmirnov and Shapiro-Wilk test data is in accordance with normal distributionusing SPSS21.0 software(?=0.1).Levene test data of homogeneity test of variance(?=0.1).Both meet the normal distribution and homogeneity of variance test in the experimental data(P>0.1),represented by the standard deviation of experiment the data can be(SX ?).Analysis and comparison of different shoulder width of zirconia fixed bridge anti compression force has or not has difference between the groups with one-way ANOVA.if there were differences between these group using Student-Newman-Keuls(P>0.5)and inter group comparison of each group was considered statistically significant.6 Fracture analysis of zirconium fixed bridge sampleA total of 18 cases of all zirconium fixed bridge samples were analyzed by high speed camera and digital optical microscope.Results:1 The compressive failure strength of all zirconium fixed bridges in each groupgroup A(Blade shoulder):(4457.33 ? 564.06)N;group B(0.5mm shoulder):(6439.65 ? 551.32)N;group C(1.0mm shoulder):(6513.00 ? 609.38)N.2 Statistical analysis of experimental dataAll the experimental data accord with normal distribution and homogeneity of variance,the anti compression destructive experiment data by single factor analysis of variance components of zirconia fixed bridge: anti compression force was statistically significant difference between each groups(P<0.05),Compared with group A and B group,or A group and C group,was statistically significant difference between(P<0.05);while there was no significant difference between B group and C group(P > 0.05).3 Sample observationA total of 18 cases of all zirconium fixed bridge samples were analyzed by high speed camera and digital optical microscope.All experimental samples of fixed bridge zirconia were fracture at the distal connecting body of inner oblique type.A group and B group were fracture over the ouside and inside edge of the retainer,for involving retainertissue surface fracture,crack originated in the retainer on the edge of the stress zone,through the connecting body,then to the loading point extended to fracture;C group showde fracture over the outside edge of retainer,not over the inside edge,not involving the retainer tissue surface,crack originates from the connection end of the gingival stress zone,by connecting the body,and then to the loading point extended to break destroy.Conclusion:1 Zirconia fixed connector at the abutment shoulder width is 0.5mm and the intensity of 1.0mm was significantly better than the shoulder blade shape,There was no significant difference between the width of 0.5mm and the intensity of 1.0mm,the clinical zirconia abutments shoulder preparation in more than 0.5mm,in order to improve its strength.2 The fracture form of zirconia fixed brige connector at the abutment width of 1.0mm was different from blade shoulder and 0.5mm shoulder.The fracture form of all zirconia fixed bridge shoulder width of blade and 0.5mm shoulder were over the ouside and inside edge of the retainer,as involving the retainer tissue surface fracture,the fracture of shoulder width of 1.0mm zirconia fixed bridge over the ouside edge,not over the inside edge,not involving the retainer tissue fracture. |
PDF Full Text Request