Three-dimensional skeletal changes after miniscrew-assisted rapid palatal expansion in adults with maxillary transverse deficiency and mandibular deviation: a retrospective CBCT study

BACKGROUND: Miniscrew-assisted rapid palatal expansion has gained increasing use in skeletally mature patients with maxillary transverse deficiency. This study aimed to evaluate three-dimensional skeletal changes after miniscrew-assisted rapid palatal expansion in adults with maxillary transverse deficiency and mandibular deviation, with particular emphasis on bilateral maxillary changes, mandibular adaptation, and the associated changes in mandibular deviation. METHODS: Twenty-one adults (mean age, 21.7 years; 7 males, 14 females) with maxillary transverse deficiency and mandibular deviation who underwent miniscrew-assisted rapid palatal expansion were retrospectively included. Cone-beam computed tomography images obtained before and after expansion were retrospectively collected for analysis. Three-dimensional measurements were performed using Mimics 21.0 software, bilateral maxillary transverse, vertical, and sagittal variables, mandibular linear measurements, and mandibular rotational variables were analyzed. Paired comparisons were performed between sides and time points. Correlation analyses were used to explore associations between skeletal changes and improvement in mandibular deviation. RESULTS: Before treatment, the upper dental width was greater on the deviated side than on the non-deviated side (P < 0.05, q < 0.05). The deviated side also showed smaller vertical distances at the alveolar bone, first molar cusp, and coronoid (P < 0.05, q < 0.05). The mandible was rotated toward the deviated side in both roll and yaw. After treatment, both basal bone width and upper dental width increased on both sides (P < 0.05, q < 0.05). Selected vertical maxillary variables increased, particularly on the deviated side, whereas mandibular roll and yaw were significantly reduced (P < 0.05, q < 0.05). Mandibular deviation decreased by 1.59 ± 0.84 mm (P < 0.05, q < 0.05). Correlation analysis showed that the reduction in mandibular deviation was associated with changes in mandibular roll and yaw (P < 0.05). CONCLUSIONS: In adults with maxillary transverse deficiency and mandibular deviation, miniscrew-assisted rapid palatal expansion resulted in transverse maxillary expansion, showed trends toward reduced interside vertical discrepancies in selected variables, and decreased mandibular deviation. Improvement in mandibular deviation was associated with adaptive mandibular rotational changes.