## 3 Results
### Distribution of Cervical Curvature by Vertical Facial Pattern  
In the hypodivergent group, the ratio of straight curvature was the highest (65.5%), followed by lordotic (17.2%), kyphotic (13.8%), and sigmoid (3.4%) curvatures. In the normovergent group, lordotic curvature showed the highest ratio (32.4%), straight and kyphotic curvatures showed the same ratio (29.4%), and sigmoid curvature showed the lowest ratio (8.8%). In the hyperdivergent group, the ratio of straight curvature was highest (55.2%), followed by kyphotic curvature (31.0%). The ratios of the lordotic and sigmoid curvatures were similar (6.9%) (Table 3).  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Hypodivergent** & **Nomovergent** & **Hyperdivergent** & **\(p\)-Value** \\  & **(_n = 29_)** & **(_n = 34_)** & **(_n = 29_)** & **\(p\)-Value** \\ \hline \multicolumn{4}{c}{Craniocervical posture} \\ \multicolumn{4}{c}{Sagittal vertical axis (mm)} & 14.4 \(\pm\) 4.5 \({}^{\text{a}}\) & 17.3 \(\pm\) 4.8 \({}^{\text{a,b}}\) & 20.0 \(\pm\) 5.5 \({}^{\text{b}}\) & 0.000 *** \\ \multicolumn{4}{c}{Cervical inclination angle (\({}^{\circ}\))} & 85.3 \(\pm\) 4.2 \({}^{\text{a}}\) & 84.5 \(\pm\) 2.9 \({}^{\text{a}}\) & 79.7 \(\pm\) 3.9 \({}^{\text{b}}\) & 0.000 *** \\ \multicolumn{4}{c}{Cervical curvature} \\ \multicolumn{4}{c}{Cbb angle (\({}^{\circ}\))} & \(-\)0.8 \(\pm\) 9.8 & \(-\)3.9 \(\pm\) 12.0 & \(-\)6.4 \(\pm\) 8.0 & 0.123 \\ \multicolumn{4}{c}{Harrison posterior tangent} \\ \multicolumn{4}{c}{angle (\({}^{\circ}\))} & 2.1 \(\pm\) 8.8 & 1.7 \(\pm\) 11.6 & \(-\)2.7 \(\pm\) 9.1 & 0.134 \\ \hline \hline \end{tabular} Values are presented as mean \(\pm\) one standard deviation. Analysis of variance was performed to compare the variables among three facial patterns. A post hoc test was conducted with the Bonferroni method. \({}^{\text{a,b}}\) Different superscript letters indicate statistical difference among three groups. The same letter means there is no difference between groups (***\(p<\) 0.001).  
\end{table}
Table 2: Comparisons of craniocortical posture and cervical curvature measurements according to vertical facial patterns.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Curvature** & \multicolumn{4}{c}{**Cervical Curvature Classification**} \\ \multicolumn{2}{c}{**Measurement**} & **Lordotic** & **Straight** & **Kyphotic** & **Sigmoid** \\ \hline [PERSON] method & 17 (18.5\%) & 47 (51.1\%) & 22 (23.9\%) & 6 (6.5\%) \\ [PERSON] method & 15 (16.3\%) & 44 (47.8\%) & 27 (29.3\%) & 6 (6.5\%) \\ [PERSON] posterior tangent method & 16 (17.4\%) & 47 (51.1\%) & 23 (25.0\%) & 6 (6.5\%) \\ Final curvature & 18 (19.6\%) & 45 (48.9\%) & 23 (25.0\%) & 6 (6.5\%) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Classification of cervical curvature.  
Significant differences were found in the distribution of cervical curvature types between the groups (\(p\) = 0.035). Even though the post hoc test did not reveal any significant pairwise difference (\(p\) > 0.05), based on the difference between the expected and observed frequencies, it can be inferred that there was a higher incidence of lordotic curves and a lower incidence of straight curves in the normovergent group. In contrast, the hypodivergent group showed a higher incidence of straight curves (Table 4).  
After categorizing the cervical curvatures into normal (lordotic) and abnormal (straight, kyphotic, and sigmoid) curves, the normovergent group showed the highest percentage of lordotic curvature (32.4%), followed by the hypodivergent (17.2%) and hyperdivergent (6.9%) groups. There was a difference in distribution between the normovergent and hyperdivergent groups. A higher incidence of lordotic curvature and a lower incidence of non-lordotic curvature were observed in the normovergent group (Table 5).