## 3 Results  
Two hundred and forty-nine patients met the inclusion criteria of this study; however, twenty-one patients were excluded after reviewing clinical and radiographic records due to. Demographic data of two hundred and twenty-eight are reported in Table 1. The mean age of patients was 30.47 \(\pm\) 0.5 (30-31, \(n\) = 228) years old with 120 (52.6%) male and 108 (49,4%) female patients. While 100 (43.86%) of the extracted molars were from the right side, 128 (56.14%) were from the left side with similar distribution between groups. According to the OPG, 132 (57.89%) patients had a radiolucent area at the apical portion of the third molar in need for extraction (D-group), while 96 (42.11%) patients did not present any relevant sign (C-group). In the entire cohort, the mean distance between the nearest portion of the root/roots to the buccal portion of the lingual cortical bone was \(-\)1.09 \(\pm\) 1.5 mm. While 126 (55.26%) patients had impacted third molars with at least-1 mm of root in the lingual cortical plate, 102 (44.74%) had non-impacted third molars. The impaction of the root of 1 mm resulted more frequently with statistical significance (Odd ratio: 32.8) using Chi-square in the D-group (84.85%) compared to C-group (14.58%) as showed in Figure 2. Stratification of patients was performed according to a differential diagnosis observing both OPG and comparing the presence of the \"Periapical Band-Like Radiolucent Sign\" in the CBCT too:  
* True sign (Y-sign): the pre-operative OPG shows a band-like radiolucent sign corresponding to the apical portion of the root of the inferior third molar with no sign of other reason that could explain this. On CBCT image lingual impaction of the root is observed. * False sign (F-sign): OPG image shows a band-like radiolucent area corresponding to the apical portion of the root of the inferior third molar and determining causes of the radiolucent area visible on OPG and CBCT such as Juxta-Apical Radio-Translucency, peri-apical lesion, immature apex, impaction of the inferior alveolar nerve into the lingual plate, apex impaction into the buccal plate. The most frequent reasons for extraction were pericoronitis with or without resorption on the adjacent lower second molar (75%), caries of the wisdom tooth (13.6%), and caries of the lower second molar (9.2%). As reported in Table 2, the mean distance between the root and cortical bone was not significantly different between male and female patients, left side and right side of mandibula. One-way ANOVA test revealed that there was a highly significant difference in mean distance between D-group (\(-\)1.89 \(\pm\) 1.26 mm) and C-group (0 \(\pm\) 1.6 mm) with \(p\) < 0.001. Analyzing CBCT, within D-group, the dark area was related to pathology in 11 cases (subgroup Yes-pathology), no sign of pathology in 121 cases (subgroup No-pathology). Four cases within No-pathology were false Y-sign because they had juxta \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **C-Group (N = 96)** & **D-Group (N = 132)** & **Total (N = 228)** & **Sig.** \\ \hline Age (mean \(\pm\) SD) & 30.53 \(\pm\) 0.5 & 30.43 \(\pm\) 0.5 & 30.47 \(\pm\) 0.5 & 0.14 \\ \hline Gender (Female/Male) & 52/44 & 56/76 & 108/120 & 0.47 \\ \hline Side (Left/Right) & 47/39 & 81/61 & 128/100 & 0.17 \\ \hline Impaction \(<\)\(-\)1 mm (Yes/Tot.) & 14/96 & 112/132 & 126/208 & **\textless{}0.001 \({}^{*}\)** \\ \hline Radiolucency due to a pathology/non-pathology & / & 11/121 & & \\ \hline Juxta-apical Radiolucency (JAR) & / & 4/132 & & \\ \hline Inferior Alveolar Nerve (IAN) impaction & / & 10/132 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: demographic and clinical characteristics of D-group vs. C-group patients. \(N\) = number, SD = standard deviation, Sig = statistical significance using Chi-square and One-way ANOVA. *= \(p\) value with significance level. apical radiolucency (JAR) and in ten CBCT an Inferior Alveolar Nerve (IAN) impaction was observed.