A “new vista” in the assessment of antero-posterior jaw relationship

Abstract

Aim The purpose of this investigation was to (1) compare the credibility of four recently introduced cephalometric measurements in assessing the antero-posterior jaw relationship; (2) To assess the correlation between various measurements used for assessment of antero-posterior discrepancy, including Yen linear, Yen angle, W angle and Pi angle. Materials and Methods The sample size for the study consisted of 45 subjects with age group of 15-19 years (mean age 17 ± 2.1) and was subdivided into Skeletal Class I, II and III groups of 15 each based upon the ANB angle derived from the pre treatment lateral cephalogram. Landmarks were located and Yen angle, Yen linear, W angle and Pi angle were assessed for each group. All the lateral cephalograms were traced by a single examiner. Intra examiner reliability was assessed by Intraclass co-efficient correlation (ICC) test. Correlation coefficients were obtained for each of parameters to compare their relationship with other parameters in Class I group. Receiver operating characteristics (ROC) curves were run to examine sensitivity and specificity of all the angles. Results The results showed that ICC for all the groups were ≥0.90 showing good repeatability of the measurements. There was statistically significant correlation between Yen angle and ANB angle, Yen linear and Yen angle for Class I group, between W angle and Yen angle for Class II group, between Yen angle, Yen linear and ANB for Class III group. ROC curves showed that Pi angle had 100% sensitivity and specificity to discriminate a Class II and a Class III group from a Class I and a Class III group from a Class II. Yen linear and W angle showed very low specificity to differentiate a Class II from a Class I group. Interpretation and Conclusion The new parameters considered in the study were found to be equally reliable and are not affected much by local remodeling due to tooth movements or by occlusal or Frankfurt horizontal plane. These parameters measure the antero-posterior discrepancy more consistently and accurately, with Pi angle being the most accurate.