## 4 Discussion  
In 1886, [PERSON] was the first to investigate the anatomy of cervical vertebrae and document Os odontoideum (OO), an anatomic anomaly of the dens of C2 [30]. Recently, the CVM method has gained popularity in orthodontics since the cervical vertebrae are often visible in the lateral cephalometric radiograph, which is part of the standard documentation used in orthodontic diagnosis [31; 32; 33; 34; 35; 36; 37; 38]. The CVM method according to [PERSON] was selected since it is a simple, widely used visual method, which focuses on the 2 nd, 3 rd and 4 th cervical vertebrae [1; 2; 33; 34; 35; 31; 32; 36; 37]. However, the method's reproducibility has been called into question [2; 26; 36; 37; 39; 40; 41; 42]. Some authors concluded that CVM is a reproducible and reliable method [42]; however, others concluded that the lower scores of CVM reproducibility may render this method too variable to be used as a strict clinical guideline [2]. In a recent systematic review, the reproducibility was rather high (98.6%), although another review stresses the need for further research on the reproducibility of this method [43; 24]. The present study addressed the reproducibility issue and avoided common methodological flaws encountered in the literature. The sample was homogenous, selected with strict inclusion and exclusion criteria. The rater team consisted of six raters with different educational backgrounds and clinical experience. The inter- and intra-rater agreement were both high. Raters were in absolute agreement or in only 1-stage-apart disagreement in 85% of the assessments. Additionally, at the re-evaluation the rater agreed with her/his previous assessment at least 3 out of 4 times. These findings point to the reproducibility of the CVM method. Consequently, the reliability of this CVM method appears to be high since cervical staging assessment can be repeated with similar findings, a finding in agreement with previous studies [28; 31; 33; 35; 44]. Absolute agreement among the examiners was lower than 50%, and the reproducibility of CS3, the stage that marks the beginning of pubertal growth, was the lowest among all stages [1]. These findings suggest that this CVM method may be unreliable to predict the pubertal spurt [2; 45]. A range of \(\pm\)1 CS might be quite wide in orthodontics, but could be tolerated in different fields (i.e., forensics). A recent morphometric study concluded that cervical vertebrae shape alone could not predict skeletal maturation better than chronologic age [20]. Growth and bone maturation are complex phenomena, influenced by several environmental and genetic factors [43]. Recently, a Y-shaped trabecular structure of the odontoid process has been identified. This structure appears to be a biomechanical response to the dynamic loading at the CV1-2 level [46]. Moreover, the posterior aspect of the cervical endplate possesses higher stiffness and yield load than the anterior endplate [47]. Different study designs with heterogeneous groups may yield different results [39; 44; 45]. Additionally, a slow and gradual transition between stages is expected and there can be morphological vertebrae variations that do not correspond to any of the six stages described above [48] (Figure 3). Inherent limitations of the CVM method such as subjectivity and experience of raters may further complicate the correct interpretation. The criteria for the identification of the concavity at the lower border of the vertebrae, as well as for the shape assessment, are not strict [28; 41]. Subjectivity is mainly influenced by training, while experience seems to have no to minimum consequence [41]. Recently, special software applications have been developed based on Deep Learning and Artificial Intelligence. These tools apply objective criteria for the assessment of the degree of CVM [49; 50; 51]. Age estimation is of major importance in forensic science [11; 52; 53]. Several methods have been proposed, even a prediction model for saliva samples [54].