A Pilot Biomechanics Analysis By Finite Element Method: Ni-Ti SMA Distractor And Canine Segmental Mandibular Reconstruction In Distraction Osteogenesis

Distraction osteogenesis (DO), which was first used mainly to lengthen long bones, has a history of nearly 100 years. Since Snyder completed the first experimental study of mandibular distraction osteogenesis in 1973, it has been widely used in the correction of craniofacial deformities. Nickel titanium memory alloy distractor (NTMA distractor) was proved to be a effective device in heightening and lengthening canine mandible. The aims of this study are to investigate a new method to construct a three-dimensional finite element model of NTMA distractor and to discuss a method about shaping a dynamic and visualizational color stress cloud chart of finite element model of NTMA distractor for CAD.Partial-cutting method Retaining part of lingual cortical bone seems to be the suitable osteotomy according to the TiNi-SMA distractor. The aims of this study are also try to control the degree of corticotomy in order to find the optimum width of hold and to observe the mechanics environment and the displacement trend of every mandibular part and to speculate on the effect upon TMJ duing distraction osteogenesis by means of the finite element model of canine segmental mandibular reconstruction in Partial-cortical-cutting distraction osteogenesis from the aspect of biomechanics analysis.There are four parts in our study: Part 1: Establishment of three-dimensional finite element model of nickel titanium memory alloy distractor for CADObjective: To investigate a new method to construct a three-dimensional finite element model of nickel titanium memory alloy(NTMA) distractor forCAD.Methods: The three-dimensional geometry model of NTMA distractor which were 60mm in wavelength and 10mm in amplitude with sine wave form was established by the Pro/E software supporting. After the geometry model repaired and the border condition of actual simulated and the initial condition and material property defined according to the nickel titanium alloy, the finite element model of NTMA distractor was established by the Marc software supporting finally.Results.- The finite element model of NTMA distractor which can predict the strength and displacement of every node and element of its own structure in the course of deforming (every period ) was set up, which can be used in CAD.Conclusion: Take the lead in using the NTMA finite element model to carry on CAD at present.This technology will contribute to improving the precision of design of the NTMA device and shortening its design cycle and economizeing its design cost.Part 2: A Method of Dynamic Visualization in the finite element model of nickel titanium memory alloy distractorObjective: To discuss a method about shaping a dynamic and visualizational color stress cloud chart of finite element model of nickel titanium memory alloy(NTMA) distractor.Methods: The three-dimensional geometry model of NTMA distractor was established and its numerical data was correlated to color stress cloud chart with RGB function in VB language under Windows operating system. The former stress cloud chart was covered with current one continuously while the displacement of NTMA distractor happened.Thus a dynamic and visualizational color stress cloud chart of changing finite element model of NTMA was completed.Results: The numerical data of every instantaneous stress cloud chart of static state was divide into 12 part equally every which was correlated to one color. More big the number became, Moer dark the color became. 52 instantaneousstress cloud chart of static state were displayed continuously and . a dynamic and visualizational color stress cloud chart of finite element model of NTMA was completed.Conclusion: The result of finite element model of NTMA can be display dynamically using VB language in the way of continuous picture display, the stress cloud chart in every point of section can be observed while the displacement of NTMA distractor happens, which can offer important reference in order to improve the NTMA distractor.Part 3:Establishment of a finite element model: canine segmental mandibular reconstruction in Partial-cortical-cutting distraction osteogenesisObjective.- To establish a finite element model of canine segmental mandibular reconstruction in Partial-cortical-cutting distraction osteogenesis.Methods: The geometry model was incised with the "cut" tool of the "Magics" software,after it was established by the "Mimics" software via reading the data of "DICOM" format from CT information.The model is composed of the nondistraction mandibular segment the slide segment (Transport disc )^ the foundational segment with ramus of mandible -> the slice between the slide segment and the foundational segment the reconstructed titanium board. These five parts were felted via the "Magics" software. At last the biomechanics analysis were completed with the "MARC" software.Results.- We took the lead to establish a finite element model of canine segmental mandibular reconstruction in Partial-cortical-cutting distraction osteogenesis in the world. The stress and displacement cloud chart in every point of section can be observed while the displacement of the finite element model happens.Conclusion: The biomechanics analysis can be obtained from the finite element model of canine segmental mandibular reconstruction in distraction osteogenesis that remains lingual cortical bone, which could offer important references for clinic to apply to the patients.Part 4: A pilot biomechanics analysis by finite element method: canine segmental mandibular reconstruction in Partial-cortical-cutting distraction osteogenesisObjective: Try to control the degree of corticotomy in order to find the optimum width of hold and to observe the biomechanics environment and the displacement trend of every mandibular part and to speculate on the effect upon TMJ duing distraction osteogenesis by means of the finite element model of canine segmental mandibular reconstruction in Partial-cortical-cutting distraction osteogenesis.Methods: The method of finite element analysis was used to simulate Partial-cortical-cutting the distraction osteogenesis.The Von Mises stress clouds chart that were compared with au of canine mandibular cortical bone were observed in "cut" situation(foe example the slice between the slide segment and the foundational segment) when 2. K 2s 1.7s 1.4s K 0.8s 0.6mm wide of slice was respectively retained during distraction osteogenesis with the force of 12 newton. The principal stress major and Von mises stress cloud chart of some points marked in the mandible were calculated while the "slice" was retained as the least width but no fracture happening.On the basis of above,the same stress cloud chart and displacement were sequentially calculated when the slide segment(Transport disc ) was removed lmm.Results: The Von Mises stress of the slice and the slide segment were both 47.76 Mpa when the slide segment was retained lmm width and it was proximal stress compared with ou (about 49.35MPa) of canine mandibular cortical bone. At this moment at the side of distraction,the Von Mises stress of the fifth cheek tooths anterior edge midpoint of condyle process anterior slope, posterior edge midpoint of condyle process posterior slope were respectively 0.3726 s 0.2408 s 0.1051Mpa and the principal stress major of the first two points were press stress and that of the last one was pull stress. There were no effect of stress at the side of nondistraction.The displacement of every mandibular point at the both side of...