ABSTRACT
Objective The objective of this study is to investigate the effects of the thickness of the adhesives (3M ESPE RelyX ARC) on the internal stress distribution of the IPS Empress II full-ceramic crowns using Finite Element Analysis (FEA). Methods A dummy Empress II ceramic crown restoration of the mandible right first molar was prepared according to standard dental process. Followed by micro-CT scanning, four 3D numerical models with cement thickness 60, 90, 120 and 150μm were established. The models were subjected to four loading conditions and stresses in veneer and core layers were presented. Results Numerical results indicate that when adhesive thickness increases from 60μm to 90μm, the maximum principal stress either in veneer or core decreases. However, when thickness increases to 150μm, stress variation trends differ from adhesives. Conclusion The normal stresses in adhesives remain a low level when the thickness varies from 90μm to 120μm, while the shear stress is less sensitive to the thickness when it exceeds 90μm. There is an optimal thickness which can reduce the tensile stress in the core and veneer. Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.
ABSTRACT
Objective To investigate the effects of the thickness of the adhesives(3 M ESPE RelyX ARC)on the internal stress distribution of the IPS Empress Ⅱ full-ceramic crowns by using Finite Element Analysis(FEA).Method A dummy Empress Ⅱ ceramic crown restoration of the mandible right first molar was prepared according to standard dental process.Followed by micro-CT scanning,four 3D numerical models with cement thickness 60,90,120 and 150 μm were established respectively.The models were subjected to four loading conditions and stresses in veneer and core layers were presented.Result Numerical results indicate that when adhesive thickness increases from 60 μm to 90 μm,the maximum principal stress either in veneer or core decreases.However,when thickness increases to 150 μm,stress variation trends differ from adhesives.Conclusions The normal stresses in adhesives remain a low level when the thickness varies from 90 μm to 120 μm,while the shear stress is less sensitive to the thickness when it exceeds 90 μm.There is an optimal thickness which can reduce the tensile stress in the core and veneer.Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.
ABSTRACT
Objective To investigate the effects of the thickness of the adhesives(3 M ESPE RelyX ARC)on the internal stress distribution of the IPS Empress Ⅱ full-ceramic crowns by using Finite Element Analysis(FEA).Method A dummy Empress Ⅱ ceramic crown restoration of the mandible right first molar was prepared according to standard dental process.Followed by micro-CT scanning,four 3D numerical models with cement thickness 60,90,120 and 150 μm were established respectively.The models were subjected to four loading conditions and stresses in veneer and core layers were presented.Result Numerical results indicate that when adhesive thickness increases from 60 μm to 90 μm,the maximum principal stress either in veneer or core decreases.However,when thickness increases to 150 μm,stress variation trends differ from adhesives.Conclusions The normal stresses in adhesives remain a low level when the thickness varies from 90 μm to 120 μm,while the shear stress is less sensitive to the thickness when it exceeds 90 μm.There is an optimal thickness which can reduce the tensile stress in the core and veneer.Attention should be paid to the shear strength of the adhesives since the shear stress could cause failure in the adhesive layer.
ABSTRACT
<p><b>OBJECTIVE</b>To analyze the stress distribution in all-ceramic crowns when it was subjected to load.</p><p><b>METHODS</b>A 3D numerical model of the all-ceramic crown of the right mandibular first molar was generated from scanned CT images. Finite element analysis (FEA) was used to evaluate the stress distribution in the all-ceramic crown when it was subjected to 5 load conditions.</p><p><b>RESULTS</b>Stress distributions under 5 loading conditions were obtained. Stress concentrations were generally found near the loading areas at the veneer and at the lower surface of the core beneath the loading areas. In the 5 loading conditions, it was found that when the crown was loaded with vertical concentrated load, the tensile stresses around the shoulder areas were uniform, while stress concentration with maximum of 32.25 MPa was found at the shoulder areas in lingual-buccal direction when loads were applied at an angle of 10 degrees with the tooth axis on the buccal side. The masticatory load which was applied at 20 degrees with the tooth axis on the buccal side would cause stress concentration at the shoulder in mesial-distal direction. The maximum value could reach 11.29 MPa.</p><p><b>CONCLUSIONS</b>The occlusal surface of the all-ceramic crown must be trimmed to increase multiple contact zones with the opposite surfaces in antagonist teeth to avoid excessive concentrated stress that may cause crown failure.</p>
Subject(s)
Crowns , Dental Porcelain , Dental Stress Analysis , Methods , Finite Element Analysis , Materials TestingABSTRACT
<p><b>OBJECTIVE</b>The aims of the present study were to assess the characteristics of MSCs which were induced and proliferated in vitro, then to learn the interfaces between them and metal materials.</p><p><b>METHODS</b>Adult dogs were selected as experimental animals, the MSCs (marrow stem cells) were aspirated from the femur, which were induced to the phenotype of OB (osteoblast), then to proliferated in vitro with metal materials. Using biochemical tests, phase contrast microscopy, transmit electromicroscope, scanning electromicroscope to detect MSCs and the image of interface.</p><p><b>RESULTS</b>MSCs had powerful osteogenic phenotype when they were induced in vitro, and they also attached to the metal materials. And there were more cells which attached on tensile stress area than other areas.</p><p><b>CONCLUSION</b>The MSCs induced in vitro could be used as source of osteoblast. The affects of air--abrasion with alumina are not significant, but they have relation to the extent of strain and property of stress.</p>
Subject(s)
Animals , Dogs , Bone Marrow Cells , Cell Differentiation , Cell Proliferation , Cells, Cultured , In Vitro Techniques , Mesenchymal Stem Cells , Metals , OsteoblastsABSTRACT
<p><b>OBJECTIVE</b>To evaluate the usage of moiré interferometre in porcelain-fused-metal interfacial fracture mechanics.</p><p><b>METHODS</b>Raster was produced on the surface of samples with different thickness of porcelain and metal in 5 groups. The stripes of u field and v field under different load were collected. Then the rupture tenacity Jc was calculated and the extensions of flaws were observed.</p><p><b>RESULTS</b>Stress concentration appeared around the flaws under load conditions. The stripe became denser under more load. The rupture tenacity Jc and the direction of flaw extension of each group were different.</p><p><b>CONCLUSION</b>Moiré interferometre can be used in the study of porcelain-fused-metal interfacial fracture mechanics and to prognosticate the direction of flaw extension.</p>