title: Miniscrew design and bone characteristics: an experimental study of primary stability.
abstract: BACKGROUND
  The purpose of this study was to evaluate the correlations between bone characteristics, orthodontic miniscrew designs, and primary stability.
  
  
  METHODS
  Four different miniscrews were placed in pig ribs. The miniscrews were first scanned with a scanning electron microscope to obtain measurable images of their threads. Subsequently, the maximum insertion torque of the screws and the maximum load value in the pullout force tests were measured; furthermore, bone specimen characteristics were analyzed by using cone-beam computed tomography. For each bone sample, the insertion site cortical thickness as well as both cortical and marrow bone density were evaluated. The nonparametric Kendall rank correlation (tau) was used to evaluate the strength of the associations among the characteristics measured. The nonparametric Kruskall-Wallis test was used to evaluate the differences among the groups, and post-hoc comparisons were assessed by using the Nemenyi-Damico-Wolfe-Dunn test.
  
  
  RESULTS
  A significant dependence was found between pitch and maximum insertion torque (tau, -0.49). Positive correlations were also found between pullout force and maximum insertion torque (tau, 0.64), cortical thickness (tau, 0.36), and marrow bone density (tau, 0.35).
  
  
  CONCLUSIONS
  In this in-vitro experimental study, strong correlations were observed among miniscrew geometry, bone characteristics, and primary stability.
authors.affiliation: Department of Orthodontics, School of Dentistry, Genoa University, Genoa, Italy. marco.migliorati@unige.it
authors.forename: Marco
authors.initials: M
authors.lastname: Migliorati
authors.forename: Stefano
authors.initials: S
authors.lastname: Benedicenti
authors.forename: Alessio
authors.initials: A
authors.lastname: Signori
authors.forename: Sara
authors.initials: S
authors.lastname: Drago
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Barberis
authors.forename: Henry
authors.initials: H
authors.lastname: Tournier
authors.forename: Armando
authors.initials: A
authors.lastname: Silvestrini-Biavati
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology; D001853:Bone Marrow / Q000473:pathology; D001863:Bone Screws; D054893:Cone-Beam Computed Tomography / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D012272:Ribs / Q000601:surgery; D013314:Stress, Mechanical; D013499:Surface Properties; D013552:Swine; D019415:Torque