Three-Dimensional Evaluation of Zygomaticomaxillary Complex Displacement and Rotational Centre in Adults Induced by Maxillary Skeletal Expander, Analysed With CBCT and Heuristic Search Algorithm.

OBJECTIVE

To precisely identify the three-dimensional (3D) centre of rotation (CoR) of the zygomaticomaxillary complex (ZMC) in patients undergoing rapid palatal expansion with a maxillary skeletal expander (MSE) using a heuristic search algorithm.

MATERIALS AND

METHODS

In this retrospective study, 17 adult patients (mean age 24.0 ± 6.0 years) with maxillary constriction were treated with MSE. Cone-beam computed tomography (CBCT) scans were acquired before treatment (T0) and after the active expansion phase (T1). A heuristic search algorithm was applied to 3D reconstructed models to iteratively compute the patient-specific CoR by minimising the error between predicted and actual displacements of 10 ZMC landmarks. A 95% 3D confidence ellipsoid analysis was performed to quantify the spatial distribution and variability of CoRs. Landmark displacements were statistically analysed using paired t-test.

RESULTS

Significant lateral, anterior and inferior displacements were observed in all ZMC landmarks following MSE expansion. The algorithm identified the CoR for each side not as a fixed anatomical point but as a confined 3D region with individual variability. After standardisation, the CoR was consistently located biomechanically near the superior orbital fissure, approximately aligned with the orbital longitudinal axis in the coronal plane. The 95% confidence ellipsoid further confirmed the regional distribution and side-related differences in CoR variability.

CONCLUSIONS

During MSE expansion, the ZMC undergoes complex 3D rotational movement around a patient-specific yet spatially consistent biomechanical region near the superior orbital fissure. This updated understanding of midfacial biomechanics may support more personalised and mechanics-guided orthodontic treatment planning.

TRIAL REGISTRATION: ClinicalTrials.gov identifier: MR-33-25-072630.