## 4 Discussion  
The use of CBCT scans daily in dentistry practices has increased in recent years. Dental CBCT have lower radiologic dosages relative to traditional CT scans and comparable precision CBCT scans could be used to detect patients with low BMD without additional scans (e.g., DEXA) and help refer those patients to further follow-up. The studies in this Systematic Review intended to study the possibility of using CBCT images to identify and differentiate patients with low BMD, patients with risk of developing osteoporosis and patients who had already recovered from this illness, from healthy individuals. \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & & & & & & & & & \\ \hline [PERSON] et al., 2014 [15] & X & X & X & X & X & X & X & X & Y \\ \hline [PERSON] et al., 2016 [13] & X & X & X & X & X & X & X & Y \\ \hline [PERSON] et al., 2015 [14] & X & X & X & X & X & X & X & Y \\ \hline [PERSON] et al., 2016 [16] & X & X & X & X & X & X & X & Y \\ \hline [PERSON] et al., 2017 [17] & X & X & X & X & X & X & X & Y \\ \hline [PERSON] et al., 2016 [19] & X & X & X & X & X & X & X & Y \\ \hline [PERSON] et al., 2016 [12] & X & X & X & X & X & X & Y & Y \\ \hline [PERSON] et al., 2019 [20] & X & X & X & X & X & Y & Y & Y \\ \hline [PERSON] et al., 2020 [18] & X & X & X & X & X & Y & Y & Y \\ \hline [PERSON] et al., 2019 [11] & X & X & X & X & X & X & X & Y \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Risk of bias in randomized trials with the analysis of the parameters: randomization process, deviations from the intended, missing outcome data, measurement of outcome, selection of the reported result and overall bias (Y green—Yes). \begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & & & & & & & & \\ \hline [PERSON] et al., 2016 [10] & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Risk of bias in non-randomized trials with the analysis of the parameters: randomization process, deviations from the intended, missing outcome data, measurement of outcome, selection of the reported result and overall bias. (Y green—Yes; N red—No). In this study, we intended to determinate the correlation coefficient between DEXA and CBCT derived values. In 2017 a systematic review was published, investigating the opportunist capability of CBCT to identify patients with low BMD [21]. This systematic review did not identify the correlation coefficient between DEXA and CBCT, and, consequently, did not had quantitative analysis of their results. The authors concluded that the evidence was restricted to endorse the use of CBCT derived images as a mean to diagnostic low BMD [21]. Meanwhile, new publications in recent years justify the elaboration of a new Systematic Review, particularly, with a quantitative analysis that allows the extraction of a correlation coefficient. All included articles in this Systematic Review concluded that CBCT derived images can be used to estimate BMD and refer patients at risk of osteoporosis. However, the methodology of the included papers was different, different indices (qualitative and linear) were used in the included studies as an opportunist diagnostic tools for low BMD. Furthermore, seven of the included papers in this review, resorted to those indices to differentiate patients with low BMD from patients with normal BMD, according to DEXA results [10; 11; 12; 16; 17; 18; 19]. Relatively to the studies who performed their analysis in the jaw bones: [PERSON] et al. [10] study, assessed CT values and radio morphometric index measurements, and concluded that those values can evaluated the changes associated to osteoporosis and referred those patients for further treatment. [PERSON] et al. [11] study calculated mean gray values of CBCT cross-sectional images and concluded that those where lower in post-menopausal osteopororotic and osteogenic females, than in postmenopausal normal BMD females. Furthermore, [PERSON] et al.