title: Mini-implant behavior to shear tensile forces in the porcine mandible.
abstract: OBJECTIVE
  To determine the tangential tensile force loading behavior of mini-implants relative to cortical bone thickness in the porcine mandible.
  
  
  METHODS
  Eighteen mini-implants were placed both anteriorly and posteriorly perpendicular to the bone surface in porcine mandibles and subjected to shear tests using a Universal Testing Machine (Instron). Further, cone beam CT was used to measure cortical bone thickness at each mini-implant site.
  
  
  RESULTS
  The shear strength differed significantly between the anterior (mean 89.05 ± 35.9 N) and posterior (mean 179.85 ± 29.01 N) sites. The same was true for the cortical bone thickness (anteriorly, mean 3.59 ± 0.49 mm; posteriorly, mean 4.24 ± 0.5 mm).
  
  
  CONCLUSIONS
  The shear forces required to dislodge mini-implants were much higher than forces typically applied for orthodontic purposes. Therefore, mandibular cortical bone supporting monocortical orthodontic mini-implants would most likely withstand immediate loading with tangential shear forces. In addition, it seems that mini-implants loaded tangentially continue to exhibit adequate anchorage for orthodontic forces even after they are displaced.
authors.affiliation: Orthodontics and Dentofacial Orthopedics, School of Dental Medicine, University of Nevada, Las Vegas, Las Vegas, Nevada, USA. chriswedwardsdds@gmail.com
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Edwards
authors.forename: James K
authors.initials: JK
authors.lastname: Mah
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D054893:Cone-Beam Computed Tomography / Q000379:methods; D003724:Dental Arch / Q000033:anatomy & histology; D015921:Dental Implants; D003799:Dental Stress Analysis / Q000295:instrumentation; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008334:Mandible / Q000033:anatomy & histology*; D008422:Materials Testing; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D033081:Shear Strength; D013314:Stress, Mechanical; D013552:Swine; D013718:Tensile Strength
chemical_list: D015921:Dental Implants