title: Osteopontin-deficiency disturbs direct osteogenesis in the process of achieving osseointegration following immediate placement of endosseous implants.
abstract: BACKGROUND
  The role of osteopontin (OPN) in the process of achieving osseointegration following implantation remains to be clarified.
  
  
  OBJECTIVE
  This study aimed to analyze the healing patterns of the bone-implant interface after immediate placement of implants in the maxillae of 4-week-old Opn-knockout (KO) and wild-type (WT) mice.
  
  
  METHODS
  After maxillary first molars were extracted, cavities were prepared with a drill and titanium implants blasted with ceramic abrasives containing hydroxyapatite/β-tricalcium phosphate were placed. Following fixation at 3, 5, 7, and 28 days after implantation, the samples were analyzed using immunohistochemistry, in situ hybridization, and an electron probe micro analyzer.
  
  
  RESULTS
  Two types of bone healing were observed in the process of achieving osseointegration: "direct osteogenesis," where bone formation occurs at the implant surface, and "indirect osteogenesis," where it does at the pre-existing damaged bone surface in the WT mice. Direct osteogenesis occurred after the recruitment of tartrate resistant acid phosphatase-positive cells and the deposition of OPN on the implant surface. In contrast, the rate of osseointegration or direct osteogenesis was significantly low, and cell proliferation was disturbed in the Opn-KO mice.
  
  
  CONCLUSIONS
  These results suggest that Opn-deficiency disturbs direct osteogenesis to lead the delayed osseointegration after immediate placement of endosseous implants.
authors.affiliation: General Dentistry and Clinical Education Unit, Niigata University Medical and Dental Hospital, Niigata, Japan.
authors.forename: Sanako
authors.initials: S
authors.lastname: Makishi
authors.affiliation: Division of Anatomy and Cell Biology of the Hard Tissue, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Saito
authors.affiliation: Division of Anatomy and Cell Biology of the Hard Tissue, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Ohshima
mesh_terms: D000818:Animals; D003758:Dental Implantation, Endosseous; D051379:Mice; D018345:Mice, Knockout; D016348:Osseointegration / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D053495:Osteopontin / Q000172:deficiency*
chemical_list: D053495:Osteopontin
keywords: dental implants; maxilla; mice (knockout); osseointegration; osteopontin; titanium; tooth extraction