title: Geometrical design characteristics of orthodontic mini-implants predicting maximum insertion torque.
abstract: OBJECTIVE
  To determine the unique contribution of geometrical design characteristics of orthodontic mini-implants on maximum insertion torque while controlling for the influence of cortical bone thickness.
  
  
  METHODS
  Total number of 100 cylindrical orthodontic mini-implants was used. Geometrical design characteristics of ten specimens of ten types of cylindrical self-drilling orthodontic mini-implants (Ortho Easy®, Aarhus, and Dual Top™) with diameters ranging from 1.4 to 2.0 mm and lengths of 6 and 8 mm were measured. Maximum insertion torque was recorded during manual insertion of mini-implants into bone samples. Cortical bone thickness was measured. Retrieved data were analyzed in a multiple regression model.
  
  
  RESULTS
  Significant predictors for higher maximum insertion torque included larger outer diameter of implant, higher lead angle of thread, and thicker cortical bone, and their unique contribution to maximum insertion torque was 12.3%, 10.7%, and 24.7%, respectively.
  
  
  CONCLUSIONS
  The maximum insertion torque values are best controlled by choosing an implant diameter and lead angle according to the assessed thickness of cortical bone.
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, School of Medicine, University of Rijeka, Rijeka, Croatia.
authors.forename: Višnja
authors.initials: V
authors.lastname: Katić
authors.affiliation: Department of Mechanical Engineering Design, Faculty of Engineering, University of Rijeka, Rijeka, Croatia.
authors.forename: Ervin
authors.initials: E
authors.lastname: Kamenar
authors.affiliation: Department of Mechanical Engineering Design, Faculty of Engineering, University of Rijeka, Rijeka, Croatia.
authors.forename: David
authors.initials: D
authors.lastname: Blažević
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, School of Medicine, University of Rijeka, Rijeka, Croatia.
authors.forename: Stjepan
authors.initials: S
authors.lastname: Spalj
keywords: Implant insertion torque; Mini-implant orthodontic anchorage; Mini-implant stability; Orthodontic mini-implant