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Bone Mineral Density Measurement with Dental Quantitative CT Prior to Dental Implant Placement in Cadaver Mandibles: Pilot Study¹

¹ From the Departments of Biomedical Engineering and Physics (P.H., W.B., R.N., H.B.) and Diagnostic Radiology (A.G.), University of Vienna General Hospital, Währinger Gürtel 18-20, A-1090 Vienna, Austria; the Department of Oral Surgery (A.B., A.G.), Dental School of the University of Vienna, Austria; the Department of Anatomy (M.T.), University of Vienna, Austria; and the Department of Maxillofacial Surgery, Evangelisches Krankenhaus, Vienna, Austria (A.B.). Received May 21, 2001; revision requested July 9; final revision received January 2, 2002; accepted February 1. Address correspondence to P.H. (e-mail: peter.homolka@univie.ac.at).

PURPOSE: To correlate torque forces during insertion of screw-type dental implants with bone mineral density (BMD) values determined preoperatively.

MATERIALS AND 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 (R² = 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.

CONCLUSION: Correlation exists between BMD measured with dental quantitative CT and the insertion torque of dental implants.

© RSNA, 2002

Index terms: Bones, mineralization, 243.81 • Computed tomography (CT), three-dimensional, 243.12117 • Experimental study • Jaws, CT, 243.12111, 243.12117, 243.92 • Teeth, 25.456

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