title: The diameter of anodic TiO2 nanotubes affects bone formation and correlates with the bone morphogenetic protein-2 expression in vivo.
abstract: BACKGROUND
  Recently, it has been demonstrated that the nanoscale environment is a critical factor for cellular behaviour. It has been shown that the diameter of TiO2 nanotube layers controls the cellular behaviour of cells involved in the bone-forming process in vitro. Therefore, the aim of the present study was to investigate the effects of the diameter of TiO2 nanotubes on peri-implant bone formation and the expression of bone matrix proteins in vivo.
  
  
  METHODS
  Ninety experimental implants with a nanotube diameter ranging from 15 up to 100 nm were placed in the frontal skulls of six domestic pigs, whereas untreated implants served as controls. The bone-implant contact (BIC) as well as the expression of bone morphogenetic protein (BMP)-2, collagen type-I and osteocalcin were histomorphometrically and immunohistochemically analysed after 30 days.
  
  
  RESULTS
  Evaluating the BIC, a significant higher value, could be found for the 50, 70 and 100 nm groups compared with the controls, whereas a correlation with the BMP-2 expression was present. The BMP-2 expression within the 50, 70 and 100 nm groups was statistically different compared with the control group. Significant difference was found for the osteocalcin expression in the 70 nm group. No statistical difference was found evaluating collagen type-I. SEM evaluation of the specimen surfaces revealed that the nanotube coatings do resist shearing forces evoked by implant insertion.
  
  
  CONCLUSIONS
  The nanotube diameter can be designed to support cellular functions of osteoblasts and osteoclasts in vivo, including differentiation and protein expression and therefore offer a powerful tool for the controlled formation of peri-implant bone around medical implant devices.
authors: Department of Oral and Maxillofacial Surgery, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany. c.wilmowsky@web.de
authors: Cornelius
authors: C
authors: von Wilmowsky
authors: Sebastian
authors: S
authors: Bauer
authors: Stefanie
authors: S
authors: Roedl
authors: Friedrich Wilhelm
authors: FW
authors: Neukam
authors: Patrik
authors: P
authors: Schmuki
authors: Karl Andreas
authors: KA
authors: Schlegel
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism*; D002448:Cell Adhesion; D024042:Collagen Type I / Q000378:metabolism; D005260:Female; D007124:Immunoenzyme Techniques; D020007:Implants, Experimental; D008855:Microscopy, Electron, Scanning; D043942:Nanotubes; D010006:Osteoblasts / Q000502:physiology; D015675:Osteocalcin / Q000378:metabolism; D010012:Osteogenesis / Q000502:physiology*; D012886:Skull / Q000601:surgery; D018709:Statistics, Nonparametric; D013552:Swine; D014025:Titanium
chemical_list: D055396:Bone Morphogenetic Protein 2; D024042:Collagen Type I; D015675:Osteocalcin; C009495:titanium dioxide; D014025:Titanium