| ObjectiveIn this study we intends to establish the 3-D models of miniscrew and alveolar bone with various parameters, and analyze the influence of the parameters changes (diameter, length, thread, thickness of cortex) and different angle of loading on the stress distribution on the miniscrew/bone interface by using of 3D-finite element analysis.Materials and MethodsIn Pro/E 2.0 software, the base model of miniscrew and alveolar bone were constructed, (length:7mm, thread pitch:0.5mm, thread profile: equilateral triangle (0.2mm), head length:2mm, neck length:1.5mm, thickness of cortex:1.5mm, cancellous bone:15mm). We changed the parameters such as the length (3mm,5mm,7mm,9mm,11mm,13mm), the diameter(1.0mm,1.2mm,1.4mm,1.6mm,1.8mm,2.0mm), and the thread profile, thread pitch (0.3mm,0.4mm,0.5mm,0.6mm,0.7mm,0.8mm), thickness of cortex (0.5mm,1.0mm, 1.5mm,2.5mm,3.5mm), angle of loading (90°,120°,150°) to construct different models. All the models were analyzed in the software ANSYS10.0, the static loading was applied to the head of miniscrew to simulate the orthodontic force, and the von Mises stress within the bone and the displacement of miniscrew were calculated for each model with finite element program.Results 1.The 3D models of miniscrew and surrounding jaw bone with different parameters were constructed. The average number of miniscrew nodes are 33833,the average number of miniscrew units are 24704.2. In the research, the maximal stress values are all in the 1mm area of the neck of miniscrew.3. The stress values are different among the minicrews with different diameter range from 1.0mm to 2.0mm, and the miniscrew with 2.0mm diameter had mini-stress distribution.4. The changes of the length did not show much influence on the stress distribution. But the miniscrew with 3.0mm length showed larger stress.5. The three loading angle showed different stress distribution and value. The 90 degree had the maximal stress value and the peak value of 150 degree is minimal.6. The stress values are different among the different cortex thickness range from 1.0mm to 2.0mm, and the miniscrew had mini-stress distribution when the thickness of cortex was 3.5mm and max-stress with 0.5mm.7. The stress values are different among the different force magnitude, and the miniscrew had mini-stress distribution with 1.ON loading and max-stress with 3.ON loading.8. The changes of the thread pitch and profile did not show much influence on the stress distribution with 90 degree loading angle. And with 120,150 degree loading angle, the minicsrew with 0.4mm thread pitch had the minimal stress value and the peak value of 0.8mm thread pitch was minimal. The miniscrew with equilateral triangle thread profile show smaller stress value than others.Conclusion:1. Among 1.0-2.0mm, the stress increased with the diameter of miniscrew, increase the diameter properly will be advantageous to stress distribution.2. And changes of length did not influence the distribution of stress much. But the stress value will increase when the length is too small. 3. The stress is linearly proportional to force magnitude and descend when the loading angle increase (90～150°), adopt larger angle may be advantageous.4. The stress descends when the cortex thickness increase, the placement site with thick cortex is advantageous.5. When the axial load increase (the loading angle increase), stresses in alveolar bone are easier affected by thread pitch and thread profile. Proper pitch will be advantageous to stress distribution and the equilateral triangle thread profile is a better choice for miniscrew design.
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