title: Numerical simulation of in vivo intraosseous torsional failure of a hollow-screw oral implant.
abstract: BACKGROUND
  Owing to the complexity and magnitude of functional forces transferred to the bone-implant interface, the mechanical strength of the interface is of great importance. The purpose of this study was to determine the intraosseous torsional shear strength of an osseointegrated oral implant using 3-D finite element (FE) stress analysis implemented by in vivo failure torque data of an implant.
  
  
  METHODS
  A Ø 3.5 mm x 12 mm ITI hollow screw dental implant in a patient was subjected to torque failure test using a custom-made strain-gauged manual torque wrench connected to a data acquisition system. The 3-D FE model of the implant and peri-implant circumstances was constructed. The in vivo strain data was converted to torque units (N x cm) to involve in loading definition of FE analysis. Upon processing of the FE analysis, the shear stress of peri-implant bone was evaluated to assume torsional shear stress strength of the bone-implant interface.
  
  
  RESULTS
  The in vivo torque failure test yielded 5952 microstrains at custom-made manual torque wrench level and conversion of the strain data resulted in 750 N.cm. FE revealed that highest shear stress value in the trabecular bone, 121 MPa, was located at the first intimate contact with implant. Trabecular bone in contact with external surface of hollow implant body participated shear stress distribution, but not the bone resting inside of the hollow.
  
  
  CONCLUSIONS
  The torsional strength of hollow-screw implants is basically provided by the marginal bone and the hollow part has negligible effect on interfacial shear strength.
authors.affiliation: CosmORAL Oral and Dental Health Polyclinics, Cinnah 7/5 Kavaklidere, Ankara, Turkey. mccehreli@yahoo.com
authors.forename: Murat
authors.initials: M
authors.lastname: Cehreli
authors.forename: Murat
authors.initials: M
authors.lastname: Akkocaoglu
authors.forename: Kivanc
authors.initials: K
authors.lastname: Akca
mesh_terms: D001863:Bone Screws; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods*; D020342:Finite Element Analysis; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D003765:Models, Dental; D011475:Prosthesis Failure
chemical_list: D015921:Dental Implants