| Mechanical stress may be associated with orthodontic miniscrew loosening, contributing to failure. This study evaluated stresses from loads on miniscrews with varying angulation/material type combinations using Finite Element Analysis (FEA). Left posterior maxilla and TOMASRTM miniscrew models were constructed with buccal miniscrew insertion between UL5/6 at 45°, 60°, and 90° angulations. Titanium (Ti), stainless steel (SS) and composite (Comp) materials were used for miniscrews. After retraction load placement models were solved with ANSYS 10.0. Maximum principle (MaxPS), minimum principle (MinPS) and von Mises (vonMS) stresses were evaluated in cortical bone and miniscrew for all angulation/material combinations. Peak ultimate tensile strengths were 1/3 below bone and miniscrew MaxPS. MaxPS in bone was greatest at 45° and least at 60°. Comp miniscrew stress trends don't follow Ti and SS with varied angulation. Varied angulation likely doesn't contribute to miniscrew failure. Stress properties of SS miniscrews compare favorably with Ti miniscrews; however, Comp shows variance which could be clinically and biologically significant. |
