الفهرس 
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Abstract
The aim of the study was to evaluate the effects of orthopedic force magnitudes (200 and 250 gm), miniscrew lengths (9, 11 and 13mm), diameters (1.5 and 2mm) and insertion angles (45o and 90o) on the stability of the miniscrew using three dimensional FEA.
The three dimensional model consisted of the following components: Screw, cortical and spongy bone. The screw solid modeling were created on Autodesk Inventor Version (8)* based on manufacturer dimensions (MONDEAL LOMAS standard system). The cortical and spongy bone were modeled in the finite element package , The bone geometry was simplified and simulated as a parallelogram representing cortical bone (20 mm length x 20 mm width x 2 mm height), the spongy bone (20 mm length x 20 mm width x 13 mm height). Finally these components were assembled in ANSYS† environment and complete osseointegration was assumed.
The resultant deformations and stresses of the applied loading were collected from the output of ANSYS program, and they were presented in Figures/Tables according to maximum values of total deformation (Usum) in mm, Von Mises stress (Svon) and compressive stress (S3) in Mpa. at each specified element in the specified volume through a twenty four runs.
*Autodesk Inc., San Rafael, CA, USA
† ANSYS Inc., Canonsburg, PA, USA
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Summary
The generalized steps to perform a finite element analysis can be summarized as follows:
A. Construction of geometrical model (buildup of solid volumes).
B. Selection of Element type to suit the case Study.
C. Definition of the material properties.
D. Mesh generation (nodes and elements generation).
E. Application of load, and boundary conditions.
F. Obtaining the data of resultant stresses.
The results were tabulated and bar charts were gathered to present the outputs of the finished runs.
The results showed that the vertically inserted screws had less deformation and stress values than obliquely inserted screws. The increase in miniscrew length and diameter decreased the deformations and stresses within the miniscrew and cortical bone. The spongy bone showed higher deformations and stresses values.