Evaluation of mandibular changes after rapid maxillary expansion: a CBCT study in youngsters with unilateral posterior crossbite using a surface-to-surface matching technique

Objectives The purpose of this study was to evaluate mandibular asymmetry in youngsters with posterior unilateral crossbite (PUXB), through cone-beam computed tomography and reverse engineering technique, before and after rapid maxillary expansion (RME) treatment. Materials and methods Forty cone-beam computed tomography (CBCT) images were obtained from all patients at two time points, namely T0 acquired before the placement of a Hyrax expander and T1 after appliance removal. The CBCT scans were segmented and volume rendered into a surface there-dimensional (3D) mesh model. Thereafter, mandibular models were digitally registered by using a best-fit algorithm. Surface and volumetric changes, between T0 and T1, were compared by using Student'sttests. Results A slight increase of 0.45 cm(3)of the total mandibular volume was found at T1 when compared with T0 (p< 0.001). The mandibular hemi-volume on the crossbite side (CB) was slightly smaller than the non-crossbite side both at T0 and T1. However, the mean differences of hemi-volume from the CB (crossbite) and non-CB side between T0 and T1 show a decrease of 0.26 cm(3)(p < 0.001). Findings for the surface-to-surface deviation analysis demonstrated a fine percentage of matching at T0 which slightly improved at T1 (p< 0.001). Conclusions Youngsters affected by PUXB showed a very slight and not statistically significant volumetric and morphological asymmetry between CB side and non-CB side at T0. However, the change in mean differences of 0.26 cm cannot be considered clinically relevant.

Automated summary

This study evaluated mandibular asymmetry in youngsters with posterior unilateral crossbite (PUXB) before and after rapid maxillary expansion (RME) treatment using cone-beam computed tomography and reverse engineering technique. The results showed a slight and not clinically relevant volumetric and morphological asymmetry between the crossbite side and non-crossbite side in patients with PUXB.