This study aims to compare two different methods for maxillary expansion in adult patients with transverse maxillary deficiency. Participants will receive either miniscrew-assisted rapid palatal expansion (MARPE-MICRO-4). We want to compare the surgically assisted rapid palatal expansion (SARPE) and the non surgical/conservative method. Clinical (3D scans of the upper jaws) measurements will be used to evaluate skeletal expansion and stability over time. Approximately 40 adult patients will be included and followed for 12 months. The results of this study may help clinicians choose the most appropriate treatment method for adult maxillary expansion.