Thread shape, cortical bone thickness, and magnitude and distribution of stress caused by the loading of orthodontic miniscrews: finite element analysis

• Published in: Scientific reports Vol. 12; no. 1; pp. 12367 - 11
• Main Authors: Sakamaki, Takuma, Watanabe, Keiichiro, Iwasa, Akihiko, Deguchi, Toru, Horiuchi, Shinya, Tanaka, Eiji
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20.07.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 692/700/3032/3065; 692/700/3032/3145; Bones; Cortical bone; Finite element analysis; Finite element method; Humanities and Social Sciences; Mathematical models; Mechanical loading; Mechanical properties; multidisciplinary; Orthodontics; Orthopedics; Safety; Science; Science (multidisciplinary); Stress concentration; Titanium alloys; Transplants & implants
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-022-16662-w

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.