Document Type: Original Article

Authors

1 Associate Professor, Department of Orthodontics, School of Dentistry, Mashhad University of Medical Sciences

2 Assistant Professor, Department of Orthodontics, School of Dentistry, Mashhad University of Medical Sciences

Abstract

Statements of Problem: Natural head position (NHP) provides the key for meaningful cephalometric analyses because an extracranial reference line is used instead of intracranial reference lines, known to be subject to considerable biological variation in their inclination. In many instances lateral cephalograms are taken or have been taken with conventional technique.Purpose: The aim of this study was to compare the accuracy of some conventional analyses in diagnosis of antero-posterior jaw relationship.Materials and Methods: This study was based on tracing of 60 lateral cephalograms that were taken with NHP technique. In the sample, there were 22 boys and 38 girls aged between 10 to 13 years old. Twenty of the x-ray films were normal occlusion. Others were class II and III, 20 of each. All cephalograms were taken in the Department of Radiology of Mashhad University Dental School. At first lateral cephalograms were analyzed with NHP method as gold standard and according to the results, patients were classified by angle classification coincided with skeletal categories. Then lateral cephalograms were analyzed with Downs, “Wits”, Sassouni and Steiner methods. Finally, by using SPSS software, the validity criteria including sensitivity, specificity, positive predictive value, negative predictive value as well as their accuracy were compared to each other.Results: This study showed that Downs and “Wits” analyses were the most accurate methods in diagnosis of class I cases. Furthermore, the sensitivity of downs analyses for class I patients was the highest. But the most accurate analyses in diagnosis of class II jaw relationship were downs and Steiner methods and for class III jaw relationship was downs analyses.Conclusion: If analyses for evaluation of sagittal relationships of the patients are needed, downs analyses is suggested because this method had the most correlation with NHP analyses. Key words: Lateral Cephalogram, Contemporary Cephalometric Analyses, Natural Head Position