Sakamaki, Takuma Tokushima University
Watanabe, Keiichiro Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Iwasa, Akihiko Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Deguchi, Toru The Ohio State University
Horiuchi, Shinya Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Tanaka, Eiji Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Cortical bone thickness is assumed to be a major factor regulating miniscrew stability. We investigated stress distribution in two miniscrews with different thread shapes (type A and B) and in cortical bone of three different thicknesses using three-dimensional (3D) finite element (FE) models. More specifically, 3D FE models of two different miniscrews were created and placed obliquely or vertically into a cylindrical bone model representing different cortical bone thicknesses. When force was applied to the miniscrew, the stress distribution on the screw surface and in the peri-implant bone was assessed using FE methodology. Miniscrew safety was evaluated using a modified Soderberg safety factor. Screw head displacement increased with a decrease in cortical bone thickness, irrespective of screw type. The smallest minimum principal stresses on the screw surfaces remained constant in type A miniscrews on changes in cortical bone thickness. Minimum principal stresses also appeared on the cortical bone surface. Lower absolute values of minimum principal stresses were seen in type A miniscrews when placed vertically and with upward traction in obliquely placed type B miniscrews. Both miniscrews had acceptable safety factor values. Taken together, orthodontists should select and use the suitable miniscrew for each patient in consideration of bone properties.
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