title: External mechanical microstimuli modulate the osseointegration of titanium implants in rat tibiae.
abstract: OBJECTIVE
  To assess the effect of external mechanical microstimuli of controlled magnitude on the microarchitecture of the peri-implant bone beds in rat tibiae.
  
  
  METHODS
  Tibiae of forty rats were fitted with two transcutaneous titanium cylinders. After healing, the implants were loaded to 1 to 3 N, five days/week for four weeks. These force levels translated into intraosseous strains of 700 ± 200 με, 1400 ± 400 με, and 2100 ± 600 με. After sacrifice, the implants' pullout strength was assessed. Second, the bone's microarchitecture was analyzed by microcomputed tomography (μCT) in three discrete regions of interest (ROIs). Third, the effect of loading on bone material properties was determined by nanoindentation.
  
  
  RESULTS
  The trabecular BV/TV significantly increased in an ROI of 0.98 mm away from the test implant in the 1 N versus the 3 N group with an opposite trend for cortical thickness. Pull-out strength significantly increased in the 2 N relatively to the nonstimulated group. Higher values of E-modulus and hardness were observed in the trabecular bone of the 2 N group.
  
  
  CONCLUSIONS
  The in vivo mechanical loading of implants induces load-dependent modifications in bone microarchitecture and bone material properties in rat tibiae. In pull-out strength measurements, implant osseointegration was maximized at 2 N (1400 ± 400 με).
authors.affiliation: Division of Bone Diseases, Department of Internal Medicine and Faculty of Medicine, University Hospital of Geneva, 1211 Geneva, Switzerland.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Zacchetti
authors.affiliation: Laboratory of Biomaterials, School of Dentistry, University of Geneva, 1205 Geneva, Switzerland.
authors.forename: Anselm
authors.initials: A
authors.lastname: Wiskott
authors.affiliation: Laboratory of Applied Mechanics and Reliability Analysis, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Joël
authors.initials: J
authors.lastname: Cugnoni
authors.affiliation: Laboratory of Applied Mechanics and Reliability Analysis, École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
authors.forename: John
authors.initials: J
authors.lastname: Botsis
authors.affiliation: Division of Bone Diseases, Department of Internal Medicine and Faculty of Medicine, University Hospital of Geneva, 1211 Geneva, Switzerland ; Division of Bone Diseases, Department of Rehabilitation and Geriatrics, Av de la Roseraie 64, University Hospital of Geneva, 1211 Geneva, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ammann
mesh_terms: D000818:Animals; D001846:Bone Development; D016348:Osseointegration; D019736:Prostheses and Implants; D051381:Rats; D013314:Stress, Mechanical; D013977:Tibia / Q000254:growth & development* / Q000473:pathology; D014025:Titanium / Q000737:chemistry
chemical_list: D014025:Titanium