Stability of expansion effects following Miniscrew-assisted Rapid Palatal expansion: a prospective longitudinal cohort study

Purpose: This study aimed to evaluate the dental and skeletal stability one year after Miniscrew-Assisted Rapid Palatal Expansion (MARPE) by using 3D image data.

Methods: Patients with transverse maxillary deficiency from the age of 16 onwards were enrolled consecutively in this prospective longitudinal cohort study. The MARPE appliance was digitally and individually designed and fabricated. Cone-beam computed tomography (CBCT) scans and intra-oral scans (IOS) were acquired before the start of MARPE treatment (T0), immediately after active expansion (T1) and one-year post-expansion (T2). Nasal floor width (NFW), palatal alveolar width at the first molar (M1) and first premolar (P1) (PAW), nasal cavity width (NCW), intermolar width (IMW) and interpremolar width (IPW) were measured to assess the immediate (ΔT0-T1) and net (ΔT0-T2) skeletal and dentoalveolar expansion and relapse (ΔT1-T2). Potential correlations with age, sex and midpalatal suture maturation (MSM) stage were also investigated.

Results: Thirty-one patients (6 men, 25 women, mean age: 26.2 years) were included. The mean follow-up time (T0-T2) was 12.2 months. The initial NFW increase demonstrated a relapse of 0.6 ± 1.2 mm, or 11.6% of the initial expansion (p < 0.01). Expansion at the alveolar level remained stable during the follow-up. IPW also remained stable during the follow-up (4.2 ± 1.3 mm at T1; 4.4 ± 2.6 mm at T2). IMW exhibited a relapse of 3.8 ± 2.1 mm, or 60.2% of the initial expansion (p < 0.001) during T1-T2. There was no statistically significant correlation between stability and age, sex and MSM stage.

Conclusions: MARPE is an effective therapy for the correction of transverse maxillary discrepancy in late adolescents and adults, achieving a clinically stable skeletal outcome one year after expansion.