title: Adapted preparation technique for screw-type implants: explorative in vitro pilot study in a porcine bone model.
abstract: OBJECTIVE
  The aim of this study was to quantify the effect of adapted preparation on the insertion torque of self-tapping implants in cancellous bone. In adapted preparation, bone condensation - and thus, insertion torque - is controlled by changing the diameter of the drilling.
  
  
  METHODS
  After preparation of cancellous porcine vertebral bone with drills of 2.85, 3, 3.15 or 3.35 mm final diameters, Brånemark sytem Mk III implants (3.75 x 11.5 mm) were inserted in 141 sites. During implantation, the insertion torque was recorded. Prior to implant insertion, bone mineralization (bone mineral density (BMD)) was measured with dental quantative computed tomography. The BMD values measured at the implant position were correlated with insertion torque for varying bone condensation.
  
  
  RESULTS
  Based on the average torque recorded during implant insertion into the pre-drilled canals with a diameter of 3 mm, torque increased by approximately 17% on reducing the diameter of the drill by 5% (to 2.85 mm). On increasing the diameter of the osteotomy to 3.15 mm (5%) or 3.35 mm (12%), torque values decreased by approximately 21% and 50%, respectively.
  
  
  CONCLUSIONS
  The results demonstrate a correlation between primary stability (average insertion torque) and the diameter of the implant bed on using a screw-shaped implant. Thus, using an individualized bone mineralization-dependent drilling technique, optimized torque values could be achieved in all tested bone qualities with BMDs ranging from 330 to 500 mg/cm(3). The results indicate that using a bone-dependent drilling technique, higher torque values can also be achieved in poor bone using an individualized drilling resulting in higher bone condensation. As immediate function is dependent on primary stability (high insertion torque), this indicates that primary stability can be increased using a modified drilling technique in lesser mineralized bone.
authors.affiliation: Center for Biomedical Engineering and Physics, Medical University of Vienna, Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Beer
authors.forename: André
authors.initials: A
authors.lastname: Gahleitner
authors.forename: Anders
authors.initials: A
authors.lastname: Holm
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Birkfellner
authors.forename: Peter
authors.initials: P
authors.lastname: Homolka
mesh_terms: D000818:Animals; D015519:Bone Density / Q000502:physiology; D003758:Dental Implantation, Endosseous / Q000295:instrumentation / Q000379:methods*; D015921:Dental Implants; D017267:Dental Prosthesis Design; D007091:Image Processing, Computer-Assisted; D008159:Lumbar Vertebrae / Q000601:surgery; D023421:Models, Animal; D010027:Osteotomy / Q000295:instrumentation / Q000379:methods; D010865:Pilot Projects; D013552:Swine; D013904:Thoracic Vertebrae / Q000601:surgery; D014057:Tomography, X-Ray Computed; D019415:Torque
chemical_list: D015921:Dental Implants