The Maxillomandibular Sagittal Assessment: The ABwise Appraisal and Its Correlation with ANB Angle.

Abstract

The ANB angle, the cephalometric parameter of choice for assessing the anteroposterior relationship between the maxilla and mandible, is subject to several limitations, prompting the investigation of alternative parameters. Objective: This study aimed to investigate the ABwise measurement as an alternative to the ANB angle for evaluating maxillomandibular relationships in orthodontics, particularly addressing the impact of skeletal discrepancies on conventional methods. Methods: A retrospective analysis was performed on a CBCT dataset of patients attending the University of Milan's Department of Orthodontics and Maxillofacial Surgery, selected based on high-quality imaging, a full-cranium field of view, and a slice thickness between 150 and 300 μm. Eight craniofacial landmarks were annotated using the 3D Slicer software to calculate the ANB values and the new ABwise measurement. Statistical analyses included Spearman's correlation (ρ), linear regression, and inter-rater agreement (Cohen's κ score), with data classified into skeletal Classes I, II, and III based on defined thresholds. Results: 354 CBCT were selected and analyzed (mean age: 18.6 years). ABwise showed a strong correlation with the ANB angle (ρ = 0.805) and new normative ranges for ABwise were established: Class I (-1.4 ± 2.3 mm), Class II (>0.9 mm), and Class III (<-3.7 mm). Moderate agreement was observed between the ABwise and ANB classifications (κ = 0.527). ABwise effectively addressed limitations associated with divergence and vertical discrepancies, providing a more reliable assessment of skeletal sagittal relationships. Conclusions: ABwise presents a viable alternative to the ANB angle for three-dimensional cephalometric analysis, offering improved accuracy and alignment with radioprotection principles by reducing the CBCT field of view needed for its measurement. Further research is required in order to validate these findings across diverse populations and clinical scenarios.