title: In vivo stability of hydroxyapatite nanoparticles coated on titanium implant surfaces.
abstract: OBJECTIVE
  Nanotechnology has been employed in attempts to enhance bone incorporation of dental implants. Often, nanoparticles are applied to the implant surface as particle coatings. However, the same properties that may increase the functionality may also lead to undiscovered negative effects, such as instability of the nanocoating. The aim of this study was to investigate the stability/instability of the nanoparticles using a radiolabeling technique.
  
  
  METHODS
  Twenty threaded and turned titanium microimplants were inserted in 10 rats. All 20 implants were coated with nanometer-sized hydroxyapatite (HA) particles. In order to trace the HA nanoparticles, the particles for 16 implants were labeled with calcium 45 (45Ca). After 1, 2, 4, and 8 weeks, the implants and surrounding bone were retrieved and analyzed using autoradiography with respect to particle migration from the implant surface. Samples from the brain, liver, thymus, kidney, and blood, as well as wooden shavings from the rats' cages, were also retrieved and analyzed using liquid scintillation counting.
  
  
  RESULTS
  The radioactivity representing the localization of 45Ca decreased over time from the vicinity of the implant. The amounts of 45Ca found in the blood and in the rats' excretions decreased with time and corresponded well to each other. After 8 weeks, the only trace of 45Ca was found in the liver.
  
  
  CONCLUSIONS
  The results indicated that released particles leave the body through the natural cleaning system, and the probability that the nanocoating will assemble in vital organs and thus become a potential biologic risk factor is unlikely.
authors.affiliation: Department of Prosthodontics, Faculty of Odontology, Malmö University, Malmö, Sweden. ann.wennerberg@mah.se
authors.forename: Ann
authors.initials: A
authors.lastname: Wennerberg
authors.forename: Ryo
authors.initials: R
authors.lastname: Jimbo
authors.forename: Stefan
authors.initials: S
authors.lastname: Allard
authors.forename: Gunnar
authors.initials: G
authors.lastname: Skarnemark
authors.forename: Martin
authors.initials: M
authors.lastname: Andersson
mesh_terms: D000818:Animals; D002132:Calcium Radioisotopes / Q000737:chemistry / Q000493:pharmacokinetics*; D020099:Coated Materials, Biocompatible / Q000737:chemistry / Q000493:pharmacokinetics*; D015921:Dental Implants; D004195:Disease Models, Animal; D006882:Hydroxyapatites / Q000737:chemistry / Q000493:pharmacokinetics*; D053758:Nanoparticles; D016348:Osseointegration / Q000502:physiology; D011849:Radioactive Tracers; D051381:Rats; D017207:Rats, Sprague-Dawley; D013499:Surface Properties; D014018:Tissue Distribution
chemical_list: D002132:Calcium Radioisotopes; D020099:Coated Materials, Biocompatible; D015921:Dental Implants; D006882:Hydroxyapatites; D011849:Radioactive Tracers