title: Characterization of retrieved orthodontic miniscrew implants.
abstract: BACKGROUND
  The purposes of this study were to characterize the morphologic, structural, and compositional alterations and to assess any hardness changes in used orthodontic miniscrew implants.
  
  
  METHODS
  Eleven miniscrew implants (Aarhus Anchorage System, Medicon eG, Tuttlingen, Germany) placed in 5 patients were retrieved after successful service of 3.5 to 17.5 months; none showed signs of mobility or failure. These implants, and brand-, type-, and size-matched specimens as controls, were subjected to multi-technique characterization.
  
  
  RESULTS
  Optical microscopy indicated loss of gloss with variable discoloration. Scanning electron microscopy and x-ray microanalysis showed morphologic alteration of the miniscrew implant surfaces with integuments formed on the surface. The materials precipitated on the surfaces were sodium, potassium, chlorine, iron, calcium, and phosphorus from the contact of the implant with biologic fluids such as blood and exudates, forming sodium chloride, potassium chloride, and calcium-phosphorus precipitates. The composition of the implant was similar to that of a titanium alloy. X-ray microtomography analysis showed no bulk structure alterations. Vickers microhardness testing showed no increased bulk or surface hardness of the retrieved specimens compared with the controls, excluding the possibility of strain-hardening phenomena as a result of self-tapping and self-drilling placement and related loading conditions.
  
  
  CONCLUSIONS
  Used titanium-alloy miniscrew implants have morphologic and surface structural alterations including adsorption of an integument that is calcified as a result of contact of the implants with biologic fluids. Randomly organized osseointegration islets on these smooth titanium-alloy miniscrew surfaces might be enhanced by the extended period of retention in alveolar bone in spite of the smooth surface and immediate loading pattern of these implants.
authors.affiliation: Department of Orthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece. teliades@ath.forthnet.gr
authors.forename: Theodore
authors.initials: T
authors.lastname: Eliades
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
authors.forename: Moschos A
authors.initials: MA
authors.lastname: Papadopoulos
authors.forename: George
authors.initials: G
authors.lastname: Eliades
mesh_terms: D000497:Alloys; D001863:Bone Screws; D002118:Calcium / Q000032:analysis; D002713:Chlorine / Q000032:analysis; D003116:Color; D054893:Cone-Beam Computed Tomography; D003722:Dental Alloys / Q000737:chemistry; D017886:Durapatite / Q000032:analysis; D004577:Electron Probe Microanalysis; D006244:Hardness; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007501:Iron / Q000032:analysis; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D010758:Phosphorus / Q000032:analysis; D011188:Potassium / Q000032:analysis; D011189:Potassium Chloride / Q000032:analysis; D012964:Sodium / Q000032:analysis; D012965:Sodium Chloride / Q000032:analysis; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D055114:X-Ray Microtomography
chemical_list: D000497:Alloys; D003722:Dental Alloys; C031462:titanium alloy (TiAl6V4); D010758:Phosphorus; D012965:Sodium Chloride; D002713:Chlorine; D011189:Potassium Chloride; D017886:Durapatite; D012964:Sodium; D014025:Titanium; D007501:Iron; D011188:Potassium; D002118:Calcium