| ObjectiveThe finite element model of micro-implant anchorage and the mandible with horizontal direction load on the micro-implant is established to analyze the impact of the load on micro-implant bone segment diameter, pitch and thread depth and jaw surface stress distribution. The results are regarded as the references and clinical applications for the development of micro-implant.Contents and methodsBased on the micro-implant anchorage geometric form of Aarhus68.75.87, the micro-implant threaded is set as6mm, the neck smooth height as0.9mm, and the bone diameter of out segment as2mm. The Pro/E software is used to generate micro-implants and jaw simplified model, with the micro-implants’ diameter of10mm and its height of12mm. The upper part of the basement is set as a portion of cortical bone with3mm thick, and the rest is set as cancellous bone. The nail road is established and the model meshes are cellared via importing the Micro-implant mandible model in Hypermesh. Afterwards, the micro-implant-mandible model is imported into ANSYS, applying a horizontal force of200g before the calculations.Resultsl.With the increase of the diameter in the micro-implant bone segment, the peak values of micro-implant-bone interface stress inclines, and the principal stresses are concentrated in the micro-implant neck and tip, the stress is mainly concentrated in the cortical bone. It can be saw from micro-implant z axis stress that the peak stress of micro-implant is concentrated in the pressure side. The relationship between stress and diameter is not linear. The minimum and most uniform stress distribution appears at the case of1.5mm diameter. It can be saw from the stress distribution figure on the mandible surface that the stress distribution area increases with the increase in the diameter of the micro-implant, but in the bone segment diameter of1.5mm case, the trend are not coincide with other cases as there is no obvious stress concentration zone.2. The micro-implant distribution stress trend has nothing to do with its pitch, and micro-implant-bone interface stress distribution is more consistent. The values of stress and displacement of the case of0.5mm pitch are both relatively small, with little fluctuation. The distribution of stress and displacement along the z axis of micro-implant is almost symmetrical, with a bell-shaped stress curve. The trends of displacement between different cases are identical, and the displacement curve are straight. The stress and displacement achieve the minimum value at the same time when the pitch is0.5mm. There is little different on the jaw bone surface stress distribution among various cases, with the smallest stress concentration area in the pitch of0.8mm, followed by the pitch of0.5mm.3. The micro-implant thread depth did no significantly affect on micro-implant stress distribution trend. The relatively small values of stress and displacement appear at the case with a thread depth of0.3mm. Stress and displacement along z axis of micro-implant also has distinctive features. Four sets of models are consistent with their minimum value in the thread depth is the model of0.3mm depth. The surface stress of the jaws is smaller in size and small variation of the four sets of model.Conclusions:1. The stress and displacement of the micro-implant-bone interface is mainly concentrated in the neck and tip, this trend has nothing to do with the micro-implant bone segment diameter, pitch, thread depth.2. The stress distribution on bone segment diameter of1.5mm micro-implant is more reasonable, providing some reference for the selection of clinical micro-implant.3. The changes of pitch affect the distribution of micro-implant stress. When the pitch is0.5mm, the stress on the interface of micro-implant-bone and micro-implant itself is more uniform.4. The thread depth of micro-implant greatly affect its mechanical properties. Short implant with the bone segment length of6mm and the thread depth of0.3mm has good flexural strength. |
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