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OBJECTIVE@#To construct a model for a controlled memory (CM) nickel-titanium (NiTi) file and another M-wire NiTi file with the same geometry by using finite element analysis. To evaluate the flexibility of a CM NiTi file by using three dimensional finite element method and to compare its mechanical responses with that M-wire NiTi.@*METHODS@#Based on the reverse engineering, the 21 mm long, 25#/08 taper Hyflex NT NiTi file and Hyflex CM NiTi file were fixed by the cantilever bending model at a distance of 9.5 mm from the tip of the file. The mechanical tester's indenter was loaded/unloaded at a distance of 3 mm from the tip of the file. The maximum displacement was 3 mm, the load displacement curve was obtained. Subsequently, by using a micro-CT to scan (layer spacing of 8 μm) NiTi files, and ABAQUS (6.10) was introduced to construct a geometric model. Hyflex NT was considered as a shapememory alloy constitutive model, Hyflex CM was considered as a power-hardening plastic constitutive model, respectively. Comparing the load-displacement curve of cantilever bending in the three-dimensional finite element model with the load-displacement curve in the experiment.@*RESULTS@#Two tetrahedral element models were constructed, the total number of nodes was 99 353 and the total number of cells was 63 744. When the loading displacement was 1 mm, the stress distribution of the cross section at 6.1 mm from the tip of the file was observed. The upper and lower surfaces were subjected to the maximum bending stress and entered the phase transformation yield stage. The finite element simulation could clearly show the deformation of the file. Various information such as deformation characteristics and stress distribution in the process were well fitted to the actual experimental curve.@*CONCLUSION@#The constitutive behavior of the material has a significant effect on the mechanical behavior of NiTi file. The finite element model established for the NiTi file of the CM wire can accurately capture the characteristics of various deformation processes of the NiTi root canal file, and it has a good fit with the actual experimental curve. The finite element model can be used for study on bending properties of CM wire.
Subject(s)
Dental Alloys , Equipment Design , Finite Element Analysis , Materials Testing , Nickel , Root Canal Preparation , Stress, Mechanical , TitaniumABSTRACT
BACKGROUND:Prognosis in tooth restoration is affected by different repair methods due to the different biomechanical effects.OBJECTIVE:To analyze three kinds of repair methods and four kinds of repair materials by using three-dimensional finite element analysis.METHODS:Tomographic images of isolated human maxillary first premolars were obtained by Micro CT scanning with a thickness of 0.019 mm.The Mimics output point cloud was used to generate the surface in Geomagic studio and the tooth model was generated respectively.The model was introduced into ABAQUS 6.13 software for Boolean operation,to simulate Inlay,Onlay of the medullary cavity retention type,and Core & Crown repair model.After the grid was divided into four ways of mechanical loading,six-point vertical loading or two-point loading at an angle of 0°,45°,90° with the long tooth shaft was done.The loading force was 75 N at each point.Four repair materials,cobalt-chrome,pure titanium,zirconia,IPS e.MAX,were used in this study.RESULTS AND CONCLUSION:(1) Under the four loading conditions of the same material,the maximum principal stress in the remaining dentin after Inlay restoration was the highest,followed by the Onlay repair and Core&Crown group.(2) Under the four loading conditions via the same approach,the maximum principal stress of the cobalt-chrome alloy in the enamel was the largest,and that of the IPS e.MAX porcelain was the smallest after repair.(3) The stress distribution of the parts was uniform after tooth restoration with the Core & Crown and the Onlay.To conclude,from the stress distribution,the Core&Crown and the Onlay are two ideal methods.Moreover,from the aspects of stress distribution and dentin preservation,Onlay is a more rational and safer way for large-area tooth defects.
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Objective To explore the effect of sequential rehabilitation nursing on upper limb function after complete replacement of forearm. Methods A total of 33 patients from September, 2010 to December, 2013 with successful forearm replacement were selected as the control group, and 32 same patients from January, 2014 to January, 2016 were selected as treatment group. The control group received rou-tine care, while the treatment group received sequential rehabilitation nursing. Postoperative visit was paid to two groups. Their upper limb function was compared with total active motion measurement, strength measurement, sensory assessment and hand function assessment. Re-sults All the indexes were better in the treatment group than in the control group (P<0.05). Conclusion Sequential rehabilitation nursing can effectively improve the upper limb function after complete replacement of forearm.
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Objective To explore the effect of sequential rehabilitation nursing on upper limb function after complete replacement of forearm. Methods A total of 33 patients from September, 2010 to December, 2013 with successful forearm replacement were selected as the control group, and 32 same patients from January, 2014 to January, 2016 were selected as treatment group. The control group received rou-tine care, while the treatment group received sequential rehabilitation nursing. Postoperative visit was paid to two groups. Their upper limb function was compared with total active motion measurement, strength measurement, sensory assessment and hand function assessment. Re-sults All the indexes were better in the treatment group than in the control group (P<0.05). Conclusion Sequential rehabilitation nursing can effectively improve the upper limb function after complete replacement of forearm.