title: Direct communication between osteocytes and acid-etched titanium implants with a sub-micron topography.
abstract: The osteocyte network, through the numerous dendritic processes of osteocytes, is responsible for sensing mechanical loading and orchestrates adaptive bone remodelling by communicating with both the osteoclasts and the osteoblasts. The osteocyte network in the vicinity of implant surfaces provides insight into the bone healing process around metallic implants. Here, we investigate whether osteocytes are able to make an intimate contact with topologically modified, but micrometre smooth (Sa< 0.5 µm) implant surfaces, and if sub-micron topography alters the composition of the interfacial tissue. Screw shaped, commercially pure (cp-Ti) titanium implants with (i) machined (Sa= ~0.2 µm), and (ii) two-step acid-etched (HF/HNO3and H2SO4/HCl; Sa= ~0.5 µm) surfaces were inserted in Sprague Dawley rat tibia and followed for 28 days. Both surfaces showed similar bone area, while the bone-implant contact was 73 % higher for the acid-etched surface. By resin cast etching, osteocytes were observed to maintain a direct intimate contact with the acid-etched surface. Although well mineralised, the interfacial tissue showed lower Ca/P and apatite-to-collagen ratios at the acid-etched surface, while mineral crystallinity and the carbonate-to-phosphate ratios were comparable for both implant surfaces. The interfacial tissue composition may therefore vary with changes in implant surface topography, independently of the amount of bone formed. Implant surfaces that influence bone to have higher amounts of organic matrix without affecting the crystallinity or the carbonate content of the mineral phase presumably result in a more resilient interfacial tissue, better able to resist crack development during functional loading than densely mineralised bone.
authors.affiliation: Department of Biomaterials, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden. furqan.ali.shah@biomaterials.gu.se.|BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Göteborg, Sweden. furqan.ali.shah@biomaterials.gu.se.
authors.forename: Furqan A
authors.initials: FA
authors.lastname: Shah
authors.affiliation: Department of Biomaterials, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden.|BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Göteborg, Sweden.|Department of Chemistry, Materials and Surfaces, SP Technical Research Institute of Sweden, Borås, Sweden.
authors.forename: Patrik
authors.initials: P
authors.lastname: Stenlund
authors.affiliation: Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Martinelli
authors.affiliation: Department of Biomaterials, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden.|BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Göteborg, Sweden.
authors.forename: Peter
authors.initials: P
authors.lastname: Thomsen
authors.affiliation: Department of Biomaterials, Sahlgrenska Academy at University of Gothenburg, Göteborg, Sweden.|BIOMATCELL VINN Excellence Centre of Biomaterials and Cell Therapy, Göteborg, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Palmquist
mesh_terms: D000818:Animals; D016723:Bone Remodeling; D001842:Bone and Bones / Q000737:chemistry; D002130:Calcium Phosphates / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D002450:Cell Communication; D008854:Microscopy, Electron; D016348:Osseointegration; D010011:Osteocytes / Q000166:cytology / Q000187:drug effects*; D019736:Prostheses and Implants; D051381:Rats; D017207:Rats, Sprague-Dawley; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D013977:Tibia / Q000187:drug effects / Q000473:pathology; D014025:Titanium / Q000737:chemistry*
chemical_list: D002130:Calcium Phosphates; D002254:Carbonates; C020243:calcium phosphate; D014025:Titanium