Αντικείμενο της μελέτης ήταν η εκτίμηση της αξιοπιστίας των κεφαλομετρικών σημείων και μεταβλητών που λαμβάνονται σε ψηφιακές πλάγιες και οπισθοπρόσθιες κεφαλομετρικές ακτινογραφίες με φυσική και σταθερή θέση κεφαλής. Το δείγμα αποτέλεσαν 42 πλάγιες κεφαλομετρικές ακτινογραφίες (21 σε σταθερή και 21 σε φυσική θέση κεφαλής) και 42 οπισθοπρόσθιες κεφαλομετρικές ακτινογραφίες (21 σε σταθερή και 21 σε φυσική θέση κεφαλής) ασθενών της Μεταπτυχιακής Κλινικής του Εργαστηρίου Ορθοδοντικής του Α.Π.Θ., πάνω στις οποίες εντοπίσθηκαν 128 σημεία και έγιναν οι κεφαλομετρικές αναλύσεις για 52 μεταβλητές. Μεταξύ της φυσικής και της σταθερής θέσης της κεφαλής, στις πλάγιες κεφαλομετρικές ακτινογραφίες παρατηρήθηκαν διαφορές σε όλα τα σημεία του άξονα Χ και σε 2 μεταβλητές, ενώ στις οπισθοπρόσθιες κεφαλομετρικές παρατηρήθηκαν διαφορές μόνο σε 2 σημεία και 2 μεταβλητές. Επίσης, στις πλάγιες κεφαλομετρικές ακτινογραφίες που έχουν ληφθεί σε σταθερή θέση κεφαλής παρατηρείται μια κλίση της κεφαλής προς τα εμπρός σε σχέση με τις πλάγιες κεφαλομετρικές με φυσική θέση κεφαλής.
The aim of the present study was to evaluate the reliability of the most common landmarks and variables in digital lateral and postero-anterior cephalometric radiographs, in natural and fixed head position. The intra-observer and the inter-observer evaluation were also assessed. The study took place at the Department of Orthodontics of Aristotle University of Thessaloniki during the period 2011-2014. The material consisted of 2 groups. After paired t-test with effect size 0.65, level of significance P=0.05 and Power=0.8, the size of sample was calculated in 21 patients for Group I and 21 for Group II. Group I consisted of 21 patients with anterior or distal displacement of the mandible. After a typical diagnostic control, patients of this group had a panoramic radiograph and a lateral cephalometric radiograph in fixed and natural head position. The total number of the lateral cephalometric radiographs was 42 (21 in fixed and 21 in natural head position).Group II consisted of 21 patients with bilateral, posterior or functional crossbite, or facial asymmetry. These patients, after a typical diagnostic control, had a panoramic radiograph and a postero-anterior cephalometric radiograph in fixed head and natural head position. The total number of the postero-anterior cephalograms was 42 (21 in fixed and 21 in natural head position). The patients were selected according to the following criteria: All patients were 12-24 years old, had full permanent dentition, had no extractions of teeth, except of wisdom, had no prosthetic or implant restorations, were not under orthodontic therapy, and presented no craniofacial asymmetries, cleft-palate or syndromes. The cephalometric radiographs were of excellent quality. They were performed with the digital x-ray machine “Proline XC with Dimax 3” (Planmeca, Helsinki, Finland). The corresponding images were transferred to a personal computer, where the digitization of landmarks was performed on the screen with the use of specially modified cephlometric software “Viewbox, version 126.96.36.199” (Dhal software, Kifissia, Greece) by the main investigator of current study, who identified 61 landmarks on the lateral and 67 on the postero-anterior cephalometric radiographs and also analyze 34 variables in lateral and 18 in postrero-anterior cephalometric radiographs. To evaluate the method of the error, the main investigator repeated the procedure using half of the total lateral and postero-anterior cephalometric radiographs. Selection was done randomly, 4 weeks after the initial digitization (intra-observer evaluation). In order to evaluate the inter-observer error, 6 postgraduate students of the Department of Orthodontics, who had completed the 1st year of the program, took part in the study as examiners. For the evaluation of reliability of the measurements, the students had to identify landmarks in 8 lateral and 8 posteroanterior cephalometric radiographs. This translates into 4 patients from Group I and 4 patients from Group II. The selection of these radiographs was done also randomly.Initially, the analysis of the data was performed with descriptive statistical analysis. For the evaluation of the distribution of the variables, the Shapiro - Wilk test was used. When the distribution of variables was normal or abnormal, parametric or non-parametric tests were used respectively. These tests were performed to assess any possible statistic differences between the 2 positions of the head, natural and fixed. The results of the present study are: a) Regarding the reliability of the landmarks in lateral cephalograms between fixed and natural head position there is significant difference in X-axis in the distribution (hence in the mean results). There is significant difference in the mean of results between fixed and natural head position in only 2 variables in lateral cephalograms (the Nasolabial angle and the Subnasale to H Plane). In postero-anterior cephalograms there is significant difference in the mean of results between fixed and natural head position in only 2 landmarks (the Zygomatic Arch R (X) and the Condyle Lateral R (X) and 2 variables (the Nasal Width L and the Upper Molar R).b) According to the reliability of the main examiner (intra-observer evaluation): The cephalometric analysis results show reproducibility in the measurements for the same examiner. c) According to the reliability between the 6 examiners (inter-observer evaluation). In lateral cephalograms: Ηomogeneity, in the measurements, was noticed agreement between the 6 examiners in landmarks and variables, in lateral cephalograms. In postero-anterior cephalograms: there are significant differences in the measurements of the 6 examiners in only few landmarks and variables. In conclusion in lateral cephalograms in fixed head position there is an inclination of the head anteriorly compared to those in natural head position. According to postero-anterior cephalograms there are significant differences in the mean results between fixed and natural head position. Finally the significant overlapping of the structures in the postero-anterior cephalograms, makes clear identification of the landmarks difficult for the examiners. Further studies on the postero-anterior cephalograms are needed.