CBCT Volumetric Changes in Combined Nasal Cavity and Paranasal Sinuses Following RAMPA-ROA Therapy: A Retrospective Cohort Study with Reference to Longitudinal Growth Data

Background: The interrelationship between craniofacial morphology and respiratory function is a central focus of orthodontic and dentofacial orthopedic research. This study aimed to evaluate the volumetric changes in the sinonasal complex (combined nasal cavity and paranasal sinuses) following Right Angle Maxillary Protraction Appliance (RAMPA) therapy using cone-beam computed tomography (CBCT) and to compare these outcomes with established longitudinal growth benchmarks. Methods: A retrospective cohort analysis was conducted on 60 pediatric patients (24 males, 36 females; mean age: 86.60 ± 24.22 months) with radiologically clear paranasal sinuses at baseline (T1). Participants underwent RAMPA therapy for an average of 8.38 months. Volumetric quantification of the entire sinonasal complex—including the nasal cavity and all four paranasal sinuses (maxillary, ethmoid, sphenoid, and frontal)—was performed to ensure methodological alignment with existing normative growth data. Results: Total sinonasal volume increased significantly from 27,741.63 ± 10,675.85 mm3 at T1 to 32,248.00 ± 10,084.07 mm3 at T2 (p < 0.001), representing a mean gain of 4506.37 mm3 (16.24%). Notably, the annualized growth velocity under RAMPA therapy (6453 mm3/year) exceeded the physiological increment of age-matched normative data (~5418 mm3/year) by approximately 1.2 times. Despite a constricted baseline at T1 compared to normative values, the treatment group demonstrated a rapid “catch-up” growth trajectory. Conclusions: RAMPA therapy induces rapid and significant volumetric expansion of the sinonasal complex in pediatric patients, demonstrating a potent “acceleration effect” that surpasses natural physiological maturation. These findings suggest that orthopedic midfacial remodeling can effectively restructure the upper respiratory environment, bridging the gap between pathological constriction and normative developmental benchmarks in patients with maxillary hypoplasia.