title: Quantitative assessment of orthodontic mini-implant displacement: the effect of initial force application.
abstract: OBJECTIVE
  Primary stability and micromovement of orthodontic mini-implants depends on a number of factors and influences clinical success or failure. The purpose of this study was to assess the behavior of orthodontic mini-implants upon initial load application.
  
  
  METHODS
  Orthodontic mini-implants (n = 39) were inserted in the alveolar process of maxillary human cadaver specimens (n = 10). Increasing horizontal forces (up to 2.5 N) were applied, and triggered images were taken in 0.5-N load intervals. Additionally, peri-implant parameters based on micro-CT volume data were recorded. Data were subjected to a two-sided nonparametric Wilcoxon signed rank test, and between-group comparisons were assessed with a Mann-Whitney test (alpha = .05).
  
  
  RESULTS
  Initial load application led to displacement beyond elastic recovery of the surrounding bone after force release (P < .001). Cortical thickness and insertion depth, despite numeric differences, did not reveal any statistical differences, while displacement of mini-implants was significantly affected by contact to neighboring teeth (P < .001).
  
  
  CONCLUSIONS
  Insertion technique and initial load application on orthodontic mini-implants may be regarded as two crucial factors for success, while repeated application of orthodontic force does not seem to increase screw mobility.
authors.affiliation: University Clinic Erlangen, Dental Clinic 3-Department of Orthodontics, Erlangen, Germany. alexandra.holst@uk-erlangen.de
authors.forename: Alexandra Ioana
authors.initials: AI
authors.lastname: Holst
authors.forename: Matthias
authors.initials: M
authors.lastname: Karl
authors.forename: Marek
authors.initials: M
authors.lastname: Karolczak
authors.forename: Matthias
authors.initials: M
authors.lastname: Goellner
authors.forename: Stefan
authors.initials: S
authors.lastname: Holst
mesh_terms: D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D003799:Dental Stress Analysis; D004548:Elasticity; D004868:Equipment Failure; D006801:Humans; D008437:Maxilla / Q000000981:diagnostic imaging / Q000601:surgery; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D010780:Photogrammetry; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques; D019415:Torque; D055114:X-Ray Microtomography
chemical_list: D015921:Dental Implants