Document Type : Original Articles

Abstract

Introduction: Measuring the antero-posterior jaw relationship has an important role in the diagnosis and treatment planning in orthodontics. Common linear and angular measurements to evaluate sagittal jaw relationship, including ANB angle and Wits index are not very accurate because various factors influence them. The aim of this study was to evaluate β angle range in 6-17 year-old students with normal occlusal relationships referring to Isfahan Faculty of Dentistry. Materials and Methods: In this descriptive-analytical study, the files in the archives of the Orthodontics Department, Isfahan Faculty of Dentistry, were evaluated and 235 cephalometric radiographs from the files of patients with no orthodontic treatment were selected; the subjects were considered to have normal occlusal relationships based on 13 criteria. The specimens were divided into 5 age groups. After tracing the cephalometric radiographs, ANB angle, Wits index and β angle (the angle produced by the AB line intersecting the line perpendicular from A to line CB) were measured. Thirty-six specimens were excluded from the study during measurements. Data was analyzed by t-test, ANOVA and Pearson’s correlation coefficient using SPSS software (α = 0.05). Results: The results showed a mean of 31.7 ± 3.31º for β angle with a range of 21.5-39º. No significant differences were observed between males and females. This angle had a direct and significant relationship with age (r = 0.435) and an inverse and significant relationship with AB angle and Wits index. Conclusion: It was concluded that β angle is accurate in evaluating antero-posterior jaw relationship and can be used as a valuable index in evaluations.   Key words: ANB angle, β angle, Normal occlusion, Wits index.