title: [Improvement of osseointegration of titanium dental implant surfaces modified with strontium-substituted hydroxyapatite].
abstract: OBJECTIVE
  To explore the osteogenic activity of a micro-arc oxidation (MAO)-treated strontium (Sr)-substituted hydroxyapatite (Sr-HA) coating developed to enhance the osseointegration of titanium dental implants, and to investigate the strengthening mechanisms of bone bonding of crystalline hydroxyapatite (HA) with incorporation of strontium in vivo.
  
  
  METHODS
  The morphology and phase component of the oxidized film of Sr-HA and HA coated implants were examined by SEM and X-ray diffraction (XRD). Then, twenty-four implants were inserted into the metaphysis of rabbits tibias and femurs using polyfluorochrome sequential labeling. Four and 12 weeks following the surgery, the morphology and chemical composition of the bone-implant interfaces were evaluated by histological examination and energy-dispersive X-ray.
  
  
  RESULTS
  The XRD patterns showed that diffraction peaks of HA shift to lower 2θ values with Sr-addition, which resulted in decreases in lattice energy and then crystallinity. Sr-HA coating presented a microporous structure in the SEM observation. Meanwhile, Sr-HA coating exhibited osteogenic activity at the early stage of bone healing period and new bone mineral apposition ratio [(4.75 ± 0.46) microm/d] was significantly higher than that of the control group [(3.21 ± 0.44) microm/d]. An apatite layer was observed at the interface of bone-Sr-HA coating in light microscopy observation and energy-dispersive X-ray analysis. Then the apatite layer was precipitated and formed new bone which became mature bone and bonded tightly to the Sr-HA.
  
  
  CONCLUSIONS
  Strontium-substituted hydroxyapatite coating shows high biological activity, which can accelerate the formation of apatite layer, hence the osteogenic ability.
authors.affiliation: Department of Prosthodontics, College of Stomatology, The Fourth Military Medical University, Xi'an 710032, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yan
authors.forename: Yu-mei
authors.initials: YM
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Han
authors.forename: Yan-tao
authors.initials: YT
authors.lastname: Zhao
authors.forename: Ji-feng
authors.initials: JF
authors.lastname: Sun
authors.forename: Hao
authors.initials: H
authors.lastname: Yan
mesh_terms: D000818:Animals; D001031:Apatites / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry; D001840:Dental Bonding; D015921:Dental Implants; D006882:Hydroxyapatites / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D016348:Osseointegration; D011817:Rabbits; D011897:Random Allocation; D013324:Strontium / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium; D014961:X-Ray Diffraction
chemical_list: D001031:Apatites; D020099:Coated Materials, Biocompatible; D015921:Dental Implants; D006882:Hydroxyapatites; C076185:strontium hydroxyapatite; D014025:Titanium; D013324:Strontium