## 3 Results
### Comparison between the Bone Mineral Density Parameters among Regions
#### 3.2.2 _Trabecular Number_ (Tb.n)  
Results for the comparison among regions of the Tb.n values were shown in Table 5. The value at the anterior base of the maxilla was the highest among all regions. The value of the maxilla did not show a statistically significant difference from the mandible and the first cervical vertebra, but showed a significant difference from the mandibular condyle. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Description** & **Unit** \\ \hline Tb.th & \begin{tabular}{c} \(\mathrm{Trabecular}\) thickness: Mean thickness of trabeculae \\ \end{tabular} & \begin{tabular}{c} mm \\ \(\mathrm{Trabecular}\) number: Measure of the average number of \\ \(\mathrm{trabeculae}\) per unit length \\ \end{tabular} & \(1/\mathrm{mm}\) \\ Tb.sp & \begin{tabular}{c} \(\mathrm{Trabecular}\) separation: Mean distance between trabeculae \\ \end{tabular} & \
\begin{tabular}{c} mm \\ \(\mathrm{mm}\) \\ \end{tabular} \\ BV/TV &
\begin{tabular}{c} Bone volume fraction: Ratio of the segmented bone volume \\ to the total volume of the region of interest \\ \end{tabular} & \% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Description of trabecular microstructure parameters. Figure 2: Two methods of trabecular bone density measurement: (**a**) Hounsfield unit, (**b**) trabecular bone microstructure parameters from reconstructed three-dimensional (3D) images. There was no statistically significant difference between the mandibular body, the first cervical verteb, and the mandibular cordyle. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Region**} & \multicolumn{3}{c}{**Male**} & \multicolumn{3}{c}{**Female**} & \multicolumn{3}{c}{**Difference**} & \multirow{2}{*}{\(p\)**-Value**} \\ \cline{3-3} \cline{5-9}  & **Median** & **IQR** & **Median** & **IQR** & **Median** & **IQR** & **Median** & **IQR** \\ \hline \multirow{4}{*}{Mx} & Tb.th & 3.92 & 0.90 & 3.71 & 0.59 & \(-\)0.21 & 0.31 & 0.647 \\  & Tb.n & 0.14 & 0.02 & 0.15 & 0.04 & 0.01 & 0.02 & 0.776 \\  & Tb.sp & 3.51 & 0.64 & 3.50 & 0.74 & \(-\)0.01 & 0.10 & 0.825 \\  & BV/TV & 54.36 & 10.58 & 54.20 & 9.80 & \(-\)0.16 & 0.78 & 0.991 \\  & HU & 1482.81 & 269.65 & 1456.87 & 213.89 & \(-\)25.94 & 55.76 & 0.752 \\ \hline \multirow{4}{*}{Mn} & Tb.th & 3.42 & 0.46 & 3.50 & 0.69 & 0.08 & 0.23 & 0.412 \\  & Tb.n & 0.14 & 0.04 & 0.14 & 0.06 & 0.00 & 0.02 & 0.328 \\  & Tb.sp & 3.68 & 0.94 & 3.75 & 0.87 & 0.07 & 0.07 & 0.290 \\  & BV/TV & 51.41 & 9.97 & 47.01 & 12.97 & \(-\)4.40 & 3.00 & 0.602 \\  & HU & 1441.03 & 234.83 & 1346.83 & 304.60 & \(-\)94.20 & 69.77 & 0.097 \\ \hline \multirow{4}{*}{Co} & Tb.th & 3.19 & 0.30 & 3.23 & 0.39 & 0.04 & 0.09 & 0.468 \\  & Tb.n & 0.14 & 0.03 & 0.14 & 0.03 & 0.00 & 0.01 & 0.412 \\  & Tb.sp & 4.38 & 2.26 & 4.31 & 3.53 & \(-\)0.07 & 1.27 & 0.962 \\  & BV/TV & 45.61 & 13.95 & 49.63 & 20.43 & 4.02 & 6.48 & 0.122 \\  & HU & 656.03 & 253.57 & 739.79 & 343.88 & 83.76 & 90.31 & 0.067 \\ \hline \multirow{4}{*}{Cv} & Tb.th & 3.23 & 0.48 & 3.37 & 0.43 & 0.14 & 0.05 & 0.190 \\  & Tb.n & 0.13 & 0.07 & 0.14 & 0.05 & 0.01 & 0.02 & 0.728 \\ \cline{1-1}  & Tb.sp & 4.48 & 3.23 & 4.10 & 1.86 & \(-\)0.38 & 1.37 & 0.776 \\ \cline{1-1}  & BV/TV & 45.92 & 24.52 & 52.51 & 19.55 & 6.59 & 4.97 & 0.507 \\ \cline{1-1}  & HU & 522.27 & 232.53 & 549.13 & 255.92 & 26.86 & 23.39 & 0.764 \\ \hline \hline \end{tabular} IQR: Interquartile range; Tb.th: Trabecular thickness; Tb.n: Trabecular number; Tb.sp: Trabecular separation; BV/TV: Bone volume fraction; HU: Hounsfield unit; Mx: Arterial base of the maxilla; Mn: mandibular body; Co: mandibular cordyle; Cr: First cervical vertebra.  
\end{table} 
Table 4: Bone mineral density measurement in males and females and the differences.