## 3 Results and Discussions
(**a**) Frontal CBCT cross section of the periapical lesion in tooth 23 is 5.2 mm; (**b**) sagittal CBCT cross section of the periapical lesion in tooth 23 is 5.61 mm; (**c**) coronal CBCT cross section of the periapical lesion in tooth 23 is 3.2 mm; (**d**) 3D CBCT cross section of the periapical lesion in tooth 23. The comparative study of the measurements performed on CBCT 3D and OPT at the level of each of the two groups showed that the discrepancy between the two methods, both in terms of depth of lesions and in terms of the extent of horizontal bone loss, was statistically significant. The CBCT 3D investigation always revealed higher values for the investigated parameters than the OPT investigation. As such, CBCT allowed us to assess bone loss in relation to adjacent anatomical structures, which plays an important role in treatment, both periodontal and endodontic, as well as in the insertion of dental implants evaluated by paraxial CBCT cross sections. Coronal, sagittal and axial CBCT cross sections allowed us to evaluate the periapical lesions in a 3D format, which plays an important role in their treatment plan for preserving the teeth with this pathology, or otherwise, their extraction if there is such a recommendation. As previously stated, one of the side effects of radiation therapy is osteoradiionecrosis [37]. Extensive periapical lesions or severe periodontal disease are a favourable factor for the development of this pathology, which is why we performed an OPT and CBCT radiological examination to evaluate the size of the lesions in the 3D version and to select the teeth that could be preserved for conservative therapy and those that needed to be extracted to avoid osteoradionecrosis after radiotherapy. [PERSON] et al. [14] observed that bone level gradually decreased with each decade, and from 50 years and older, the bone loss was even more pronounced, reaching a mean of about 1.8 mm at that age. Moreover, infrabony defects were more pronounced in the maxilla, especially at the molar level [14]. A study examined the differences in bone density before and after endodontic treatment in teeth with periapical lesions, and the authors concluded that the use of CBCT to measure bone density before and after endodontic treatment is recommended for teeth with periapical lesions [38]. Alternatively, in a recent study, [PERSON] et al. [39] revealed that periapical lesions can be detected with similar accuracy on OPT vs. CBCT except those that are less than 4.5 mm in size and those that are located in the upper and lower incisor areas. On the other hand, [PERSON] et al. [40] observed that CBCT had higher accuracy in the detection of periapical lesions compared to periapical and panoramic radiography. As stated in the Introduction, quantifying disease biomarkers is of great importance for early interventions to monitor disease progression or to evaluate treatment responses [41; 42]. Moreover, one should not underestimate the importance of age as a modifier of disease progression and treatment [43]. Besides its role as a potential biomarker for cancer progression and prognosis, Dkk-1 can be also considered an efficacious treatment strategy for preventing cancer metastasis in oral squamous cell carcinoma and also can be a molecular marker for early detection of lymph node metastasis [2; 3]. Regarding the comparative evaluations of the results obtained by the ELISA assay in the control patients compared to those with cancer, there were statistically significant differences. The mean value for Dkk-1 in cancer patients was 1.209 \(\pm\) 0.110 ng/mL, significantly lower than the similar value observed in healthy patients of 1.712 \(\pm\) 0.100 ng/mL (Figure 4). The obtained results could represent the different outcomes of both cancer and periodontal disease, since it is well-known that Dkk-1 is a critical secreted factor that modulates the microenvironment [44]. In terms of cancer, the strong duality of the role of Dkk-1 is remarkable [45].