Bone mineral density

Abstract

Objective: To verify whether bone mineral density (BMD) of cortical bone, trabecular bone, and total bone influence the primary stability of orthodontic miniscrews and to verify whether there is a correlation between the measurement of BMD by cone-beam computed tomography (CBCT) and central dual-energy x-ray absorptiometry (DEXA).

Materials and methods: Twenty bovine bone sections were extracted from the pubic and iliac bones from regions with cortical thicknesses of approximately 1 mm. The BMD of the total bone block was evaluated using two methods: CBCT and DEXA. The BMD of cortical, trabecular, and total bone in the region of interest (ROI) were also evaluated by CBCT. After scanning the bone blocks, 20 self-drilling miniscrews (INP®) 1.4 mm in diameter and 6 mm long were inserted into them. The peak implant insertion torque (IT) was registered. After this, the pull-out test (PS) was performed and the maximum force registered. The Pearson correlation test was applied to verify the correlations between variables.

Results: The BMD of the total bone block verified by CBCT and DEXA showed a positive and strong correlation (r = 0.866, P = .000). The BMD of the ROI for cortical bone influenced the IT (r = 0.518, P = .40) and the PS of miniscrews (r = 0.713, P = .001, Table 2). However, the total bone BMD (verified by CBCT and DEXA) and trabecular bone BMD presented weak and not statistically significant correlations with primary stability.

Conclusions: There was a positive correlation between total bone block BMD measured by DEXA and CBCT. The cortical BMD influenced the IT and PS.

Figure 1

Region of interest (ROI) delimitation in the sagittal section. (a) Smaller rectangle on the left indicates the cortical ROI. Larger rectangle on the right indicates the trabecular ROI; (b) total bone ROI.