The study design comprised a three-arm, parallel-group randomized controlled trial (RCT) conducted at the Orthodontics clinic of Brussels University Hospital. Patients were randomly allocated into one of three groups:
- Continuous rapid activation protocol: Patients received one activation of 0.17 mm per day until reaching the clinical goal.
- Continuous slow activation protocol: Patients underwent two activations (0.33 mm) per day for the first 7 days, followed by one turn forward every third day (0.17 mm / 3 days).
- Force-controlled polycyclic protocol: Patients underwent two activations (0.33 mm) per day for the first 7 days. Then, the hex nut was turned 6 sides backward, followed by 6 sides forward after 15 minutes. Additionally, the device was activated by 0.17 mm every third day.
Intervention:
All patients underwent maxillary expansion with MARPE. Four orthodontic mini-screws were inserted under local anesthesia using a surgical guide and motor. Surgical incision was not required, and predrilling was performed if necessary. The MARPE remained in place for 12 months after expansion to allow bone remodeling in the midpalatal suture. Fixed straight-wire treatment commenced 2 months after expansion termination. Patients underwent retention check-ups at 6 and 12 months post-expansion, and expansion screws and mini-screws were removed after 12 months or before orthognathic surgery, if applicable.
The specific aims of the study were to evaluate the success rate of nonsurgical maxillary expansion, compare the efficacy of the three activation protocols, assess and compare complications, analyze the correlation between success rate and Midpalatal Suture Maturation Stage (MPS), age, and sex, and measure nasal permeability variation using anterior rhinomanometry.
