title: Loss of anchorage of miniscrews: a 3-dimensional assessment.
abstract: BACKGROUND
  Miniscrews have exponentially empowered the orthodontic anchorage armamentarium. However, the behavior of miniscrews under loading has not yet been fully investigated.
  
  
  METHODS
  Forty miniscrews were used for retraction of the maxillary and mandibular canines into the spaces of extracted first premolars. After a healing period of 2 weeks, a loading force was applied between 150 and 250 g for 6 months. The displacement of the miniscrews, their placement angles, and their implanted percentages into the bone were assessed by using superimposed 3-dimensional volumes of the maxilla and the mandible before and after 6 months of loading of the miniscrews.
  
  
  RESULTS
  Miniscrews were displaced in the direction of orthodontic loading. The displacement was experienced in the movement of the head and tail, and extrusion of the miniscrews. These movements were not correlated with the placement angle or the length of miniscrews in the bone.
  
  
  CONCLUSIONS
  Movement of miniscrews is to be expected during orthodontic loading. This phenomenon should be considered when determining their dimensions and placement angles to provide the maximum range of action for orthodontic mechanics without midtreatment replacement of miniscrews.
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt.
authors.forename: Amr Ragab
authors.initials: AR
authors.lastname: El-Beialy
authors.forename: Amr Mohamed
authors.initials: AM
authors.lastname: Abou-El-Ezz
authors.forename: Khaled Hazem
authors.initials: KH
authors.lastname: Attia
authors.forename: Ahmad Mohamed
authors.initials: AM
authors.lastname: El-Bialy
authors.forename: Yehya Ahmed
authors.initials: YA
authors.lastname: Mostafa
mesh_terms: D001863:Bone Screws; D002508:Cephalometry; D003758:Dental Implantation, Endosseous / Q000295:instrumentation / Q000379:methods; D015921:Dental Implants; D019232:Dental Restoration Failure; D006801:Humans; D021621:Imaging, Three-Dimensional; D008137:Longitudinal Studies; D008310:Malocclusion / Q000628:therapy*; D008334:Mandible; D008437:Maxilla; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016382:Orthodontic Appliance Design; D016348:Osseointegration; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation* / Q000379:methods
chemical_list: D015921:Dental Implants