Novel approach to three-dimensional intermaxillary skeletal assessment : Correlation between the ANB angle and the bisector Wits appraisal.

Abstract

Purpose: The present study aimed to compare and correlate the ANB angle with the bisector Wits appraisal for a three-dimensional (3D) assessment of the maxillomandibular sagittal relationship using a cone beam computed tomography (CBCT) dataset.

Methods: After outlier removal, 351 CBCT scans were chosen based on inclusion criteria (high quality, full-cranium field of view [FOV], slice thickness 150-300 μm) and analyzed using 3DSlicer software (Brigham and Women's Hospital, Boston, MA, USA, version 5.2.2). Eight anatomical landmarks were manually annotated, identified on axial views, and confirmed on the rendered volume image. The coordinates of each landmark were exported and the ANB (°) and bisector-Wits (mm) measurements were constructed. Dahlberg's D tested the intraobserver reliability and two-sample Kolmogorov-Smirnov test was executed to assess normality and to select the subsequent tests. Spearman's rank correlation coefficient (ρ) was utilized to correlate the angular (ANB) and linear (bisector-Wits) measurements, whereas the Siegel estimator for nonparametric linear regression was employed to establish norm values by the correlation equation. Significance was set at p < 0.05 with correlation coefficients exceeding ρ > 0.70 deemed clinically relevant.

Results: High (ρ = 0.773) and statistically significant (p < 0.001) correlations between the ANB and bisector-Wits measurements were found. The obtained equation was the following: bisector-Wits = 1.06 × ANB - 6.32. Therefore, the obtained rounded norm range for bisector-Wits for skeletal class I sagittal relationship was determined to be from -6.3 to -2.1 mm (-4.2 ± 2.1 mm). Values less than -6.3 mm correspond to a class III, whereas greater than -2.1 mm correspond to a class II skeletal relationship.

Conclusion: The study revealed a statistically significant correlation between the ANB and bisector-Wits. From a 3D perspective, the bisector-Wits represents a reliable parameter to assess maxilla-mandibular skeletal discrepancies instead of the ANB angle, also adhering to radioprotection principles by limiting the FOV to the maxillary complex only and potentially reducing the radiation exposure in CBCT-based cephalometry.