## 3 Results  
The sample included digital lateral cephalometric radiographs from 474 Caucasian subjects (mean age 13.38 years, range 6.4-22.4 years, SD 4.01, 95%, CI 13.02-13.75), 217 males (mean age 12.93 years, range 6.9-22.3 years, SD 3.79, 95%, CI 12.42-13.43) and 257 females (mean age 13.8, range 6.4-22.4 years, SD 4.15, 95%, CI 13.26-14.28). Intra-rater and inter-rater agreement were assessed among all the examiners after the calibration procedure. Intra-rater agreement was high, ranging from 0.857 to 0.931, whereas intra-rater absolute agreement ranged from 77% (367 out of 474) to 87.3% (414 out of 474) (Table 1). Intra-rater absolute agreement by stage (CS) was calculated and CS3 was the least reproducible stage. Inter-rater reliability was high (0.90). Inter-rater agreement ranging from absolute agreement to 5 stages disagreement was also assessed. Inter-rater absolute agreement was lower than 50% (Table 1). Figure 1: Examples of the cervical vertebral maturation stages, according to [PERSON] et al. [1]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**Intra-Rater Agreement**} \\ \hline \multirow{2}{*}{Rater} & [PERSON]’s weighted kappa & \multirow{2}{*}{95\% CI} & \multirow{2}{*}{Std. Err.} & Absolute agreement \\  & & & & \(n\) (\%) \\ \hline OR1 & 0.902 & 0.880–0.924 & 0.011 & 398 (83.9) \\ OR2 & 0.931 & 0.913–0.948 & 0.009 & 414 (87.3) \\ OPS & 0.916 & 0.896–0.937 & 0.010 & 408 (86.0) \\ DR & 0.908 & 0.888–0.928 & 0.010 & 397 (83.7) \\ D & 0.857 & 0.829–0.884 & 0.014 & 367 (77.0) \\ MR & 0.888 & 0.864–0.911 & 0.012 & 384 (81.0) \\ \hline \multicolumn{5}{c}{**Intra-Rater Absolute Agreement by Stage**} \\ \hline \multirow{2}{*}{Rater} & CS1 & CS2 & CS3 & CS4 & CS5 & CS6 \\ \hline OR1 & 89\% & 83\% & 75\% & 88\% & 81\% & 84\% \\ OR2 & 98\% & 87\% & 71\% & 79\% & 89\% & 88\% \\ OPS & 89\% & 83\% & 84\% & 87\% & 87\% & 85\% \\ DR & 92\% & 78\% & 73\% & 82\% & 86\% & 75\% \\ D & 81\% & 71\% & 65\% & 75\% & 79\% & 87\% \\ MR & 88\% & 75\% & 65\% & 84\% & 80\% & 83\% \\ \hline \multicolumn{5}{c}{**Inter-Rater Agreement**} \\ \hline \multirow{2}{*}{Intraclass correlation coefficient (95\% CI)} & First assessment 0.919 & Second assessment 0.934 & \multirow{2}{*}{\
\begin{tabular}{} \end{tabular} } \\  & (0.908–0.931) & & (0.925–0.943) \\ \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } \\  & \(n\) & \% & \(n\) & \% \\ \hline Absolute agreement & 203 & 42.82 & 234 & 49.36 \\ \hline One stage apart & 222 & 46.83 & 200 & 42.19 \\ \hline Two stages apart & 31 & 6.54 & 30 & 6.32 \\ \hline Three stages apart & 18 & 3.79 & 10 & 2.10 \\ \hline Four stages apart & 0 & & 0 \\ \hline Five stages apart & 0 & & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Rater agreement. Figure 2: Chronological age among Cervical Vertebral Maturation (CVM) stages (vertical bars denote 0.95 confidence intervals). The age confidence intervals among CS1, CS2, CS3, CS5 and CS6 appeared to overlap in each gender group as well as in the total sample. However, a clear distinction among CS3, CS4 and CS5 was observed in the total sample as well as in each gender group. Females aged \(\leq\)11.21 years and males aged \(\leq\)1.75 years belong to the first three CS. Females older than 15.72 years and males older than 16.17 years belong to CS5 or CS6. The data were analyzed by means of analysis of variance (gender F: 9.15, \(p\): 0.002629, CS F: 159.43, \(p\) < 0.001, gender \"CS F: 0.1, \(p\): 0.992637). LSD (Least Significant Difference) test showed that the differences in mean ages among the 6 CS stages were statistically significant and increased as the CS increased. The only exception was CS2 and CS3 that did not show statistically significant difference, albeit the difference was in the expected direction (Table 3). Linear model regression analysis was based on highly significant relationships (Table 4). The adjusted coefficient of determination (adjusted \(R^{2}\) = 0.61) reveals that the regression line fits the data relatively well; gender and CS, could explain 61% of the age variance in the sample.