Asymmetry assessment using cone-beam CT: a class I and class II patient comparison

Abstract

Introduction: Asymmetry assessment is an important component of orthodontic diagnosis and treatment planning. Before the advent of three-dimensional imaging, orthodontists relied on two-dimensional headfilms to diagnose asymmetry. Cone beam computed tomography (CBCT) allows for assessment of asymmetry on a dimensionally accurate volumetric image. This study aims to determine if there is a difference in skeletal asymmetry between patients with a skeletal class I ANB angle compared to patients who have a skeletal class II using CBCT images. Methods: CBCT images were examined from 70 consecutive patients who presented for routine orthodontic care and fit inclusion criteria. Asymmetry was analyzed using an asymmetry index developed by Katsumata et al.18 Anatomic landmarks were defined and reference planes were established to determine the variance of the landmarks using a coordinate plane system. 30 randomly selected patients were reanalyzed to assess reliability of the method. Results: Statistical analysis demonstrated no significant relationship between asymmetry and ANB angle for any of the landmarks. Asymmetry index scores were reproducible within a certain range of agreement for each landmark. Conclusions: Based on this study, the differential in jaw proportion common for class II skeletal patterns results in no more skeletal asymmetry than class I skeletal patterns. Altman-Bland agreement plots suggest that some modification may be indicated to the system proposed by Katsumata et al18 to improve asymmetry diagnosis.