Pre-expansion downward maxillary base rotation as a biomarker for post-expansion downward maxillary rotation in adults treated with 3D-guided midpalatal piezocorticotomy-assisted MARPE: a pilot case-control study.

INTRODUCTION: Structural predictors of success or failure in adult maxillary expansion remain poorly defined. This retrospective case-control pilot study aimed to evaluate the predictive capacity of pre-treatment craniofacial morphology-specifically the palatal plane inclination (SN-PP)-on final post-treatment maxillary skeletal morphology in adults undergoing 3D-Guided Midpalatal Piezocoticotomy Assisted Miniscrew-assisted rapid palatal expansion (3D-GMP MARPE). METHODS: A total of eighty skeletally mature patients were evaluated, comprising a control group (mean age: 35.7 ± 8.4 years) and a case group (mean age: 33.1 ± 10.1 years) exhibiting sleep-disordered breathing and/or transverse maxillary deficiency underwent three-dimensional (3D) digitally guided midpalatal piezocoticotomy-assisted MARPE. Baseline metrics were derived from cone-beam computed tomography (CBCT) datasets in NemoFab software. Subjects were stratified based on their final absolute post-treatment morphology into cases (SN-PP >=11 degrees, n = 15) or controls (SN-PP < 11degrees, n = 65). Univariable and multivariable logistic regressions calculated crude and adjusted odds ratios (aOR) controlled for biological sex. Classification accuracy was evaluated using Receiver Operating Characteristic (ROC) curve analysis. RESULTS: Baseline demographics, sagittal relationships, and soft-tissue thicknesses were statistically identical between groups (p > .05). Conversely, cases exhibited a significantly steeper baseline SN-PP_b angle than controls (11.5 ± 2.9° vs. 7.3 ± 3.1°, p = .001). Univariable regression revealed a 57% increase in the odds of case status per degree increase in SN-PP_b (OR=1.57; 95% CI: 1.23, 2.00; p < .001). This signal remained robustly significant after adjusting for sex in the multivariable model (aOR=1.51; 95% CI: 1.18, 1.94; p = .001). ROC analysis demonstrated excellent diagnostic discrimination (AUC = 0.841), backed by a post-hoc statistical power of 99.7%. CONCLUSIONS: A steeper pre-treatment palatal plane angle is a powerful, sex-independent predictor of a high-angle post-treatment skeletal relationship. Integrating SN-PP into diagnostic protocols provides high classification accuracy for pre-operative risk stratification regarding final skeletal phenotype.