title: Hydroxyapatite and calcium phosphate coatings on aluminium oxide orbital implants.
abstract: BACKGROUND
  Hydroxyapatite and calcium phosphate have been used as bone graft substitutes as they facilitate and promote tissue ingrowth. We carried out a study to examine uncoated and coated aluminium oxide (alumina) spherical orbital implants and assess whether the coatings influence fibrovascular ingrowth.
  
  
  METHODS
  The aluminium oxide spheres (three coated with hydroxyapatite, three coated with calcium metaphosphate and three uncoated) were manufactured at the School of Materials Engineering, Yeungnam University, Kyongsan, Kyongbuk, Korea. The implants were examined macroscopically and with scanning electron microscopy and were analysed chemically by means of x-ray powder diffraction and x-ray fluorescence spectrophotometry. Implantation of three hydroxyapatite-coated, three calcium metaphosphate-coated and three uncoated aluminium oxide spheres was done in nine adult male New Zealand albino rabbits. Implant vascularization was evaluated at 4, 8 and 12 weeks by means of histopathological sectioning.
  
  
  RESULTS
  All three types of implant had multiple interconnected pores. The coatings increased the size of the trabeculae from 150 microm to 300 microm. As a result, the pores appeared slightly smaller but still ranged in size from 300 microm to 750 microm, compared to 400 microm to 800 microm in the uncoated implants. The coatings also increased the weight of the implants slightly. The implants were all strong mechanically. They were made up primarily of aluminium oxide. The coated implants contained significant amounts of calcium oxide (a contaminant). There was no clinical difference in the socket response between the three groups. Histopathologically, fibrovascularization occurred uniformly throughout each implant at 4, 8 and 12 weeks after implantation.
  
  
  CONCLUSIONS
  The hydroxyapatite and calcium metaphosphate coatings did not appear to facilitate or inhibit fibrovascular ingrowth at 4, 8 and 12 weeks. Longer-term studies are need to determine whether the coatings play a role in long-term acceptance and retention of the implants.
authors.affiliation: Department of Ophthalmology, University of Ottawa Eye Institute, Ont.
authors.forename: David R
authors.initials: DR
authors.lastname: Jordan
authors.forename: Seymour
authors.initials: S
authors.lastname: Brownstein
authors.forename: Steve
authors.initials: S
authors.lastname: Gilberg
authors.forename: Dustin
authors.initials: D
authors.lastname: Coupal
authors.forename: Sukyoung
authors.initials: S
authors.lastname: Kim
authors.forename: Louise
authors.initials: L
authors.lastname: Mawn
mesh_terms: D000537:Aluminum Oxide; D000818:Animals; D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D017886:Durapatite; D015353:Eye Enucleation; D008297:Male; D008855:Microscopy, Electron, Scanning; D018919:Neovascularization, Physiologic / Q000502:physiology; D009915:Orbit / Q000098:blood supply / Q000601:surgery; D020273:Orbital Implants; D019919:Prosthesis Implantation; D011817:Rabbits; D013052:Spectrometry, X-Ray Emission; D014961:X-Ray Diffraction
chemical_list: D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; D017886:Durapatite; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous; D000537:Aluminum Oxide