Experimental Study On Immediately Loaded Micro-implant

Part I Stability and interface study on immediately loadedmicro-implant1. Study on Stability of Micro-implant Anchorage Objective To study the stability of micro-implant anchorage which were loaded immediately.Methods After loaded with orthodontic force of 200g for 2 months, the movement of micro-implants and the dogs' second premolars anchored by micro-implant were studied.Results All the loaded premolars showed apparent displacement, while the micro-implants kept stabile and most of them moved little. Conclusion The micro-implant can withstand 200g of immediate horizontal loading as an orthodontic anchorage.2. Evaluation of the interface between immediately loaded micro-implant and boneObjective To study the peri-implant bone reaction to the immediatelyloaded micro-implant.Methods Micro-implants were implanted into dogs' mandibular bones, immediately loaded, with polyfluorochrome sequential labeling. Seventy-three days after implantation, the dogs were euthanized and dissected mandibles were prepared. The specimens were evaluated by light microscope, fluorescent microscope, polarized light microscope, microradiography, scanning electron microscope and energy dispersive x-ray spectroscope.Results All results suggested that osseointegrated interfaces were formed between micro-implants and bones. Fluorochrome labels hinted that lamellae bones appeared 6 weeks after implantation, and were formed more extensively another 3 weeks later.Conclusions Micro-implants can be loaded immediately and the interfaces have normal turnovers of osseointegration.Part II Three dimensional FEM analysis of stress distribution around micro-implant loaded with different-directed force1. Establishment of three-dimentional finite element model for micro-implant and boneObjective To establish a three-dimentional finite element model formicro-implant and bone in mandibleMethods In the software ANSYS, APDL was used to establish athree-dimentional model of micro-implant and bone, then elementproperty was defined and the model was meshedResults An appropriate FEM model was established, with totally 5164nodes and 29352 elements.Conclusions The model precisely reflects the contact of micro-implantand bone, while it will not be too complicated for the solution afterloading.2. Three dimensional FEM analysis of stress distribution around micro-implant loaded with different-directedforceObjective To analyze the stress around micro-implant loaded with forces in different directions which may be used in clinical practice. Method Three dimensional finite element analysis software was used to setup micro-implant and bone FEM model. Forces in five directions were applied to the head of micro-implant, that is, referring to the axis of micro-implant and starting from the head of micro-implant, 0 degree, 30degree, 45 degree, 60 degree and 90 degree.Results On all the conditions, the maximum stress of Von Mises werevery small with the neck of implant always being stress focused , and thestress increased with the angle of force.Conclusion The micro-implant can safely loaded with 200g force indifferent directions, especially the one in smaller angle, but combinedwith former animal test, when we intend to localize the product, weshould consider to reform the neck of micro-implant.