title: Computed tomographic characterization of mini-implant placement pattern and maximum anchorage force in human cadavers.
abstract: BACKGROUND
  The purpose of this investigation was to characterize the placement pattern and factors influencing the primary stability of mini-implants in human cadavers. The factors studied were mini-implant length, placement depth, bone density, and bone type.
  
  
  METHODS
  Sixty standard mini-implants (6, 8, and 10 mm; 20 of each size) were placed into the maxillas and mandibles of 5 fresh human cadavers. Computed tomography imaging was used to measure the placement pattern, bone density, and thickness surrounding each device. The mini-implants were subsequently subjected to increasing tensile forces (pull-out force) until failure, and the maximum mechanical anchorage force of each was recorded with a dynamometer. A statistical model was realized by using MATLAB version 7.5.0 with Statistics Toolbox 7 (MathWorks, Natick, Mass) including the maximum anchorage force, mini-implant length, bone type, placement depth, and density surrounding each section of the mini-implant.
  
  
  RESULTS
  Placement depth was strongly dependent on mini-implant length: 15% of the 6-mm implants failed to anchor their parallel sections into cortical bone, but 95% of the 10-mm mini-implant parallel sections penetrated beyond the buccal cortical bone; all 20 tips of the 6-mm mini-implants (100%) reached cancellous bone, whereas 75% of the 10-mm implants penetrated both cortical plates, reaching the lingual cortical bone. Longer mini-implants were associated with greater incidences of sinus and bicortical perforations. The correlation coefficients between the initial maximum mechanical anchorage force and the studied factors were as follows: bone density and placement depth combined (r = 0.65, P <0.001), mini-implant length (r = 0.45, P = 0.004), bone density (r = 0.42, P = 0.007), and placement depth (r = 0.29, P = 0.06).
  
  
  CONCLUSIONS
  During mini-implant length selection, the clinician should consider the important trade-off between anchorage and risk of placement complications or damage to the tissues. Longer mini-implants enable more anchorage; however, they are associated with a higher risk of damage to neighboring structures. Placement depth and bone density at the site of mini-implant placement are the best predictors of primary stability.
authors: Faculty of Dentistry, McGill University, Montreal, Québec, Canada. genevieve.lemieux2@mail.mcgill.ca
authors: Genevieve
authors: G
authors: Lemieux
authors: Adam
authors: A
authors: Hart
authors: Chrissy
authors: C
authors: Cheretakis
authors: Craig
authors: C
authors: Goodmurphy
authors: Stephanie
authors: S
authors: Trexler
authors: Christopher
authors: C
authors: McGary
authors: Jean-Marc
authors: JM
authors: Retrouvey
mesh_terms: D000369:Aged, 80 and over; D000539:Alveolar Process / Q000000981:diagnostic imaging* / Q000601:surgery; D015519:Bone Density; D002102:Cadaver; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D003799:Dental Stress Analysis; D005260:Female; D006801:Humans; D008297:Male; D008904:Miniaturization; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016382:Orthodontic Appliance Design; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013718:Tensile Strength; D014057:Tomography, X-Ray Computed
chemical_list: D015921:Dental Implants