## 4 Results
The point Basin (X-axis, Y-axis), lateral Orbitas (X-axis), and left Porion (X-axis) scored a \"good\" ICC, while the left lateral Orbita (Y-axis, Z-axis) a \"moderate\" ICC, and the right lateral Orbita (Y-axis, Z-axis) and the Basin (Z-axis) a \"poor\" ICC. Porion and external orbital rims are reportedly less reliable landmarks [39; 40; 41]. Even though bilateral landmarks have been reported to be less reliable than midsagittal landmarks [17], the Basin ICC was also poorly detected without orientation. Using the Acta plane for orientation, all scores improved, except for the left Gonion and right Porion. The Z-axis of the left Gonion and right Porion were affected after reorientation, but their ICC scores were still \"good.\" Difficulties in locating these landmarks are a result of a curved anatomical structure, which makes it more difficult for the examiner to identify these landmarks [28]. Performing the measurements was equally reliable in the groups with or without orientation, probably because the majority of the landmarks used to calculate linear and angular measurements had an excellent ICC, except for Gonion. Even then, differences in the coordinates of the landmarks did not affect the measurements significantly (Table 5). As previously discussed, the anatomy of the landmark has a considerable influence on its identification (e.g., landmarks on curvatures are harder to locate correctly) [28]. In addition, the instrument used to locate these landmarks--multiplanar slices versus 3D reconstructions versus cephalometric radiographs--also influences its identification [42]. Some studies have shown that CBCT multiplanar slices provide high accuracy in determining landmarks [42; 43]. Therefore, in this study, landmarks were located in multiplanar slices. In agreement with this paper's results, other studies showed a more reliable location of landmarks after the virtual orientation of the CBCT images. In these studies, researchers have tried different setups of the FHP [41], alternative planes to the FHP [27], or even the natural head position versus intracranial references. [18]. Still, most of the references used also relied on the Porion [18; 44; 45; 46]. [PERSON] et al. varied the FHP setups in 3D and noticed that not only did different orientations result in differences in reliability but also that setups dependent on the Porion points and Orbitales were mostly affected [43]. Also, in agreement with the present study, [PERSON] et al. suggested that the use of intracranial references might increase reliability in measuring and detecting landmarks in CBCT scans [18]. However, this study relied on the transporionic plane, which is also dependent on the Porion. The study by [PERSON] et al. used the internal acoustic meatus (IAM) instead of the Porion [27]. Even though the reliability and reproducibility of the IAM have been indicated [35], including it or the Porion in a CBCT scan demands a large field of view, and even then, if the physical orientation of the patient's head is tilted, it might result in not including the Porion in the CBCT scan. In contrast with the present findings, other studies showed no significant increase in the reliability of locating landmarks after the orientation of CBCT images [43; 47]. [PERSON] et al. evaluated scans acquired with different head positions and no virtual orientation, and their results showed no significant difference between measurements [48]. This study was, however, performed with a dry skull and showed less concordance with a complex head position. In a similar study with a dry skull and variation of the position of the head, [PERSON] et al. suggested that the head position might significantly influence linear measurements in CBCT scans, especially vertical and horizontal measurements as a result of extension and flexion head movements [22]. Another study in dry skulls showed that different head positions and orientations affected 3D model segmentation, but these differences were not clinically relevant [23].