title: Bone mineral density measurement with dental quantitative CT prior to dental implant placement in cadaver mandibles: pilot study.
abstract: OBJECTIVE
  To correlate torque forces during insertion of screw-type dental implants with bone mineral density (BMD) values determined preoperatively.
  
  
  METHODS
  Dental quantitative computed tomography (CT) was performed with simultaneous imaging of five postmortem mandibles and a calibration standard containing defined concentrations of calcium hydroxyapatite. CT numbers were converted to local BMD values by assuming a linear relationship (BMD = a x HU + b), where a and b are calibration coefficients. The a, b, P, and t values, correlation coefficients, and standard errors were calculated. Dental implants (n = 25) were set, and insertion torques were recorded. BMD was determined at the implantation site and correlated with torque forces recorded during implant insertion. Calibration coefficients derived for specimens were compared with those derived for actual patients.
  
  
  RESULTS
  Calibration coefficients (at 120 kV) for the postmortem specimens were a = 0.760 +/- 0.03 (mean +/- SD) and b = 2.8 +/- 3.7 and for the patients were a = 0.804 +/- 0.06 and b = 5.2 +/- 4.2. Calibrated BMD values at the location of dental implants exhibit a significant correlation (R(2) = 0.83, P <.001) with insertion torques on the basis of a second-order model, which yields torque = (0.0055 x BMD + 0.73)(2) for the implants used and the surgical technique applied.
  
  
  CONCLUSIONS
  Correlation exists between BMD measured with dental quantitative CT and the insertion torque of dental implants.
authors.affiliation: Department of Biomedical Engineering and Physics, University of Vienna General Hospital, Währinger Gürtel 18-20, A-1090 Vienna, Austria. peter.homolka@univie.ac.at
authors.forename: Peter
authors.initials: P
authors.lastname: Homolka
authors.forename: Andreas
authors.initials: A
authors.lastname: Beer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Birkfellner
authors.forename: Robert
authors.initials: R
authors.lastname: Nowotny
authors.forename: André
authors.initials: A
authors.lastname: Gahleitner
authors.forename: Manfred
authors.initials: M
authors.lastname: Tschabitscher
authors.forename: Helmar
authors.initials: H
authors.lastname: Bergmann
mesh_terms: D015519:Bone Density; D002102:Cadaver; D002138:Calibration; D003757:Dental Implantation; D015921:Dental Implants; D017886:Durapatite / Q000032:analysis; D006801:Humans; D008334:Mandible / Q000000981:diagnostic imaging*; D010865:Pilot Projects; D014057:Tomography, X-Ray Computed; D019415:Torque
chemical_list: D015921:Dental Implants; D017886:Durapatite