INTRODUCTION: This study proposes a novel structural parameter, the insertion depth of the pyramidal process into the pterygoid notch (IDP), as a measure of pterygopalatine suture (PPS) resistance during palatal expansion and aims to evaluate the correlation between the IDP-based PPS classification and midpalatal suture (MPS) expansion. METHODS: Preexpansion and postexpansion cone-beam computed tomography images of 23 adults treated with miniscrew-assisted rapid palatal expansion were superimposed. After superimposition, the IDP, sagittal position of the expander, bone thickness penetrated by the miniscrews, PPS separation status (PPS RESULTS: Both hemi-AME and hemi-PME increased significantly with PPS separation (regression coefficient [b] = 0.88 and 1.25, respectively
P <
0.01). IDP was negatively correlated with the probability of PPS separation (P <
0.01), and the OC CONCLUSIONS: PPS separation promotes skeletal expansion. The greater the IDP, the lower the probability of PPS separation. OC