A New Approach for the Assessment of True Maxillomandibular Sagittal Relationship: A Zeta Angle

Abstract

Introduction: The assessment of sagittal skeletal dysplasia is crucial for accurate diagnosis and treatment planning, thus necessitating a thorough evaluation. A novel cephalometric parameter, known as the Zeta angle, was proposed in this study for the evaluation of the maxillomandibular relationship in the sagittal plane. Materials and methods: This observational study was carried out using 291 pre-treatment lateral cephalograms of participants aged between 15 and 25 years, categorized into skeletal class I, II, and III relationships based on Wits appraisal, ANB angle, and Beta angle. The individuals reported to the Department of Orthodontics from January 2021 to October 2023, Manav Rachna Dental College, Manav Rachna International Institute of Research and Studies, Faridabad. The Zeta angle was constructed using three skeletal reference points as point Pt (pterygoid), point M (center of premaxilla), and point Pm (suprapogonion) and was measured perpendicular to point M on the Pt-Pm line and the M-Pm line to determine the severity and type of maxillomandibular discrepancy in the sagittal plane. Statistical tests were used to obtain the mean values for the Zeta angle. Analysis of variance (ANOVA), followed by the Bonferroni post-hoc test, was used to assess skeletal differences between the groups. Receiver operating characteristic (ROC) curves were used to evaluate the sensitivity and specificity of this angle. Results: The results indicated that a Zeta angle between 57° and 64° had a class I skeletal jaw pattern, a Zeta angle less than 57° indicated a class II skeletal jaw pattern, and a Zeta angle greater than 64° indicated a class III skeletal jaw pattern. ROC curves showed that a Zeta angle less than 57.5° had 80% sensitivity and 82.5% specificity in distinguishing class II from the class I subset. A Zeta angle greater than 64.5° has a sensitivity and specificity of 92.5% in distinguishing class III from the class I subset. Conclusion: The Zeta angle may serve as an additional diagnostic tool for the reliable determination of sagittal jaw relationships due to its establishment based on stable anatomical points, thus remaining unaffected by jaw rotations and orthodontic treatments.