## 4 Discussion
This suggests that an increase in the mandibular plane angle corresponds to a decrease in cervical curvature; however, when examining the distribution of cervical curvature types, no difference was observed between the hyperdivergent and hypodivergent groups. [PERSON] et al. [8] found no significant differences in cervical curvature relative to vertical facial patterns. Their study was limited in not including kyphotic cervical curvature since kyphosis is not considered a physiological posture of the spine. [PERSON] and [PERSON] [17] observed a very weak negative correlation between the mandibular plane angle and cervical lordosis angle (the angle between odontoid process tangent and a line through the inferoposterior points of C2 and C4, CLA), noting reduced CLA in association with large vertical facial dimensions and increased CLA with a shorter vertical dimension. However, these studies were conducted with adult men; therefore, the results cannot be directly compared with those in our study. This indicates that the cervical curvature type cannot be explained solely by the magnitude of the mandibular plane angle. Examination of the relationship between craniocervical posture and cervical curvature measurements revealed that the Cobb angle had a weak correlation with craniocervical posture, whereas the Harrison posterior tangent angle showed no correlation. There are two possible explanations for this minimal correlation. First, a backward craniocervical posture may affect cervical curvature. Typically, a more lordotic curvature is expected with a more backward head position; however, this study found a prevalence of straight curvatures associated with such a posture. Second, cervical curvature may be influenced by multiple factors, with craniocervical posture being one of many potential influences. Previous studies suggest that factors such as muscle tension, lifestyle patterns, repetitive trauma, and congenital and developmental conditions may play a role [9; 41; 42; 43], rather than craniofacial structure alone. This may explain the weak correlation observed in the present study. Additionally, the influence of environmental and social factors remains unclear, requiring further research on physical, psychosocial, and personal risk factors to better understand their impact on cervical alignment. The mechanism underlying loss of cervical lordosis remains unclear. A recent hypothesis is that weakness of the neck extensor muscles is a risk factor for the development of cervical kyphosis [44]. A previous study has reported on the association between forward head posture and neck muscle imbalance [45]. Therefore, it is reasonable to assume that neck muscle imbalance according to different cervical postures may affect cervical spine curvature. To date, no trial has investigated the differences in neck extensor and flexor muscles according to vertical facial patterns. Only partial neck muscles were investigated, and they reported significant differences in the electromyographic activity of the sternocleidomastoid and trapezius when the vertical dimension varied [46]. Therefore, cervical muscle status according to vertical craniofacial factors should be considered in future studies. Many dental clinicians are not familiar with methods for assessing cervical spine alignment. This study found that the simple Cobb method showed a strong correlation with the highly accurate Harrison method, making it a clinically accessible diagnostic tool. This correlation is likely due to both methods relying on angular measurements, which primarily evaluate overall cervical curvature. However, discrepancies between methods arise because angular measurements alone cannot differentiate segmental reversed curvatures, whereas the Ohara method, using linear assessments, is more sensitive to detecting regional kyphotic changes. Therefore, incorporating linear assessments alongside angular methods may enhance diagnostic accuracy in clinical practice. This study had certain limitations.