title: Peri-implant bone adaptations to overloading in rat tibiae: experimental investigations and numerical predictions.
abstract: OBJECTIVE
  (i) To assess the effects of mechanical overloading on implant integration in rat tibiae, and (ii) to numerically predict peri-implant bone adaptation.
  
  
  METHODS
  Transcutaneous titanium implants were simultaneously placed into both tibiae of rats (n = 40). After 2 weeks of integration, the implants of the right tibiae were stimulated daily for 4 weeks with loads up to 5N (corresponding to peak equivalent strains of 3300 ± 500 με). The effects of stimulation were assessed by ex vivo mechanical tests and quantification of bone mineral density (BMD) in selected regions of interests (ROIs). Specimen-specific finite element models were generated and processed through an iterative algorithm to mimic bone adaptation.
  
  
  RESULTS
  Bilateral implantation provoked an unstable integration that worsened when mild (2-4N) external loads were applied. In contrast, a stimulation at 5N tended to "counterbalance" the harmful effects of daily activity and, if applied to well-integrated specimens, significantly augmented the implants' resistance to failure (force: +73% P < 0.01, displacement: +50% P < 0.01 and energy: +153% P < 0.01). Specimen-specific numerical predictions were in close agreement with the experimental findings. Both local and overall BMD variations, as well as the implants' lateral stability, were predicted with small errors (0.14 gHA/cm3and 0.64%, respectively).
  
  
  CONCLUSIONS
  The rats' daily activity detrimentally affects implant integration. Conversely, external stimulations of large magnitudes counterbalance this effect and definitively improve integration. These changes can be predicted using the proposed numerical approach.
authors: Laboratory of applied mechanics and reliability analysis, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors: Marco
authors: M
authors: Piccinini
authors: Laboratory of applied mechanics and reliability analysis, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors: Joel
authors: http://orcid.org/0000-0003-3656-9146
authors: J
authors: Cugnoni
authors: Laboratory of applied mechanics and reliability analysis, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
authors: John
authors: J
authors: Botsis
authors: Division of bone diseases, Department of internal medicine specialities, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland.
authors: Patrick
authors: P
authors: Ammann
authors: Division of fixed prosthodontics and biomaterials, University Clinics of Dental Medicine, University of Geneva, Geneva, Switzerland. Anselm.Wiskott@unige.ch.
authors: Anselm
authors: A
authors: Wiskott
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D003758:Dental Implantation, Endosseous / Q000379:methods*; D015921:Dental Implants; D005260:Female; D020342:Finite Element Analysis; D020007:Implants, Experimental; D016348:Osseointegration / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery*; D014025:Titanium; D014057:Tomography, X-Ray Computed
chemical_list: D015921:Dental Implants; D014025:Titanium
keywords: adaptation algorithm; bone augmentation; finite element; implant integration; in vivo stimulation; specimen-specific