title: Effects of magnesium-substituted nanohydroxyapatite coating on implant osseointegration.
abstract: OBJECTIVE
  The objective of this study was to compare magnesium-substituted and pure hydroxyapatite coatings on the promotion of osteogenesis in vitro and on the osseointegration in vivo.
  
  
  METHODS
  Electrochemically deposited pure hydroxyapatite (EDHA) or electrochemically deposited magnesium-substituted hydroxyapatite (EDMHA) coatings were formed on the surface of pure titanium disks or implants. MC3T3-E1 preosteoblasts were cultured in the EDHA and EDMHA coated disks, and cell growth, alkaline phosphatase (ALP) activity, and osteocalcin secretion were measured at various time points. For studies on osseointegration, 30 roughened implants coated either with EDHA or EDMHA (n = 15 for each coating) were implanted in the femurs of 15 NZW rabbits. After 2, 4, and 8 weeks, femurs were retrieved and prepared for histomorphometric evaluation (n = 5 for each coating at each time point).
  
  
  RESULTS
  MC3T3-E1 cells cultured on EDMHA coated disks showed increased cell number, ALP, and osteocalcin secretion compared with the EDHA coated disks at all time points (P < 0.05 for all). Histologic observation of the coated implants showed woven bone in direct contact with both implant surfaces after 2 weeks and mature bone after 8 weeks. While there were no differences in the amount of bone between the threads at any time point, the percentage of implant in direct contact with bone (bone implant contact) was slightly higher along the EDMHA coated implants at 2 weeks (P = 0.086), although this difference was no longer seen at 4 and 8 weeks.
  
  
  CONCLUSIONS
  Mg-substituted HA coated surfaces promote osteogenic differentiation of preosteoblasts in vitro and may improve implant osseointegration during the early stages of bone healing compared with pure EDHA coated surfaces.
authors.affiliation: Department of Oral and Maxillofacial Surgery, The Affiliated Stomatology Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
authors.forename: Shi-fang
authors.initials: SF
authors.lastname: Zhao
authors.forename: Qiao-hong
authors.initials: QH
authors.lastname: Jiang
authors.forename: Sean
authors.initials: S
authors.lastname: Peel
authors.forename: Xiao-xiang
authors.initials: XX
authors.lastname: Wang
authors.forename: Fu-ming
authors.initials: FM
authors.lastname: He
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D017886:Durapatite / Q000494:pharmacology*; D004563:Electrochemistry; D005269:Femur / Q000601:surgery; D020007:Implants, Experimental; D008274:Magnesium / Q000737:chemistry* / Q000494:pharmacology*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles; D016348:Osseointegration / Q000187:drug effects*; D015675:Osteocalcin / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects*; D011817:Rabbits; D013499:Surface Properties; D014025:Titanium / Q000494:pharmacology
chemical_list: D020099:Coated Materials, Biocompatible; D015921:Dental Implants; D015675:Osteocalcin; D017886:Durapatite; D014025:Titanium; D000469:Alkaline Phosphatase; D008274:Magnesium