Application of a novel form of structural classification of the pterygopalatine suture for predicting midpalatal suture expansion by miniscrew-assisted rapid palatal expansion in adults: A cohort study.

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), and MPS expansion at the anterior and posterior nasal spines (hemi-AME and hemi-PME) were determined. To analyze the plausibility of PPS as a mediating variable, regressions were performed to confirm the correlation between PPS and both MPS expansion and IDP. The optimal cut-off point of the IDP for predicting PPS (OC) was obtained when Youden's index reached a maximum. Finally, the correlation between the OC-based PPS classification and the MPS expansion was analyzed using linear regression.

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 was 1.90 mm (area under the curve = 0.901). The OC-based PPS classification showed significant correlations with both hemi-AME and hemi-PME (b = -0.59 and -0.87, respectively; P <0.05).

Conclusions: PPS separation promotes skeletal expansion. The greater the IDP, the lower the probability of PPS separation. OC-based PPS classification is an effective predictor of MPS expansion in miniscrew-assisted rapid palatal expansion-treated adults.