## 3 Results
### Risk of Bias  
The risk of bias in randomized and non-randomized studies is summarized in Tables 3 and 4, respectively. The only randomized trial included had a low risk of bias [11]. Regarding non-randomized studies, most of the included studies revealed a low risk of bias (6 out of 10). The remaining four have methodological flaws, 2 of them in the domain of bias due to confounding [20; 21], 1 in deviations from intended interventions domain [16], and 1 with a methodologic flaw in the missing data domain [12].  
\begin{table}
\begin{tabular}{c c} \hline
**Author, Year of Publication** & **Coefficients of Correlation** \\ \hline [PERSON] et al., 2016 [13] & Pearson correlation between Dens CBCT derived values and DEXA values: in osteopororotic group: r = 0.34–0.38 [\(p\) value = 0.02–0.036]; Non-osteoporotic group: r = 0.48–0.61 [\(p\) value \(\leq\) 0.003] \\ \hline [PERSON] et al., 2014 [15] & [PERSON]’s correlation coefficients were 0.5 and 0.6 (\(p\) value = 0.037 and 0.009) between RD of bone area of the mandible and T-scores obtained from FN and LV, respectively \\ \hline [PERSON] et al., 2015 [14] & Correlation Coefficients between CBCT-derived RD values of the left part of first cervical verteb and the dens: r = 0.7, 0.6; \(p\) < 0.001 \\ \hline [PERSON] et al., 2016 [10] & Lumbar vertebrae DXA-derived measures and CTMI (r = 0.48, \(p\) \(\leq\) 0.01), CTI(I) (r = 0.40, \(p\) \(\leq\) 0.01), and CTI(S) (r = 0.32, \(p\) \(\leq\) 0.01) \\ \hline [PERSON] et al., 2016 [16] & Correlation factor of r = 0.857 between femoral neck BMD and the ratio of the cortical and total bone areas \\ \hline [PERSON] et al., 2017 [17] & RAFC and total femur (r = 0.889), RAFC and femoral neck (r = 0.924), RAFC and femoral tracchanter (r = 0.821), RAFC and femoral inter-trochanter (r = 0.867), RAFC and femoral ward’s triangle (r = 0.895) \\ \hline [PERSON] et al.,2016 [19] & Spearman correlation factor between BV/TV and lumbar spine, total hip, femoral neck and distal radius, respectively: 0.08, 0.26, 0.17 and 0.32. \\ \hline [PERSON] et al., 2016 [12] & Correlation found between CTI and CTMI with lumbar spine BMD: \(p\) < 0.05, r = 0.340 and \(p\) < 0.001, r = 0.463, respectively \\ \hline [PERSON] et al., 2019 [20] & Pearson correlation between lumbar spine BMD and cortical mandibular bone density and cancellous bone density in case group (diabetic male patients) was r = 0.63, \(p\) < 0.01 and r = 0.607, \(p\) < 0.01, respectively. \\ \hline [PERSON] et al., 2020 [18] & [PERSON]’s correlation between the T-scores of lumbar spine and the CBCT GS values at posterior maxilla: r\({}^{2}\) = 0.849 \\ \hline [PERSON] et al., 2019 [11] & [PERSON]’s correlation between the T-scores of femoral neck and the gray values of cancellous and cortical bone at the site of maxillary tuberosity areas: r = 0.411, \(p\) < 0.001 \\ \hline \end{tabular} RD–Radiographic density; FN—Femoral Neck; LV—Lumbar vertebrae; CTMI—computer tomography mandibular index; CTI(S)—CT index (superior); CTI(I)—CT index (inferior); CTI—Computer tomography mandibular index; CTMI—computer tomography memorial index; BV/TV—bone volume (r/t trabecular volume ratio; RAFC—relative cross-sectional area of forearm cortical; CBCTI(S)—CBCT mandibular index (superior); CBCTI(I)—ADNUM index (inferior); CBCTMI: CBCT mental index; CBCTCM: CBCT mandibular cortical index; GS—Grayscale values.  
\end{table}
Table 2: Coefficients of correlation between BMD values obtained with DEXA and CBCT technologies.