Long-term assessment of skeletal and dental asymmetry after conventional and mini-implant-assisted rapid palatal expansion.

Introduction: This study aimed to evaluate the short-term and long-term skeletal and dental asymmetry with miniscrew-assisted rapid palatal expansion (MARPE), rapid palatal expansion (RPE), and control group using cone-beam computed tomography (CBCT) analysis.

Methods: A total of 180 CBCT scans were analyzed for 60 patients divided into 3 groups: MARPE (mean age 13.7 ± 1.74 years), RPE (mean age 13.9 ± 1.14 years), and control (mean age 13.3 ± 1.49 years). CBCT scans were recorded at 3 points: pretreatment (T1), postexpansion (T2), and posttreatment (T3). The anterior nasal spine, posterior nasal spine, zygomaticomaxillary point, anterior nasal cavity width, posterior nasal cavity width (PNCW), external maxillary width, palatal width, and molar inclination were measured on the left and right sides in all CBCT scans. In addition, maxillary molar width (MMW) and maxillary canine width were also evaluated on the left and right sides. Statistical analysis was performed, and the parameters were tested within the groups from T1 to T2 and T1 to T3 using a paired t test. The mean changes were then compared among the 3 groups by a mixed analysis of variance test.

Results: The RPE group showed significantly greater MMW on the left and right sides at T2 (P <0.05). MARPE and RPE led to a significant increase in the anterior nasal spine (right and left), zygomaticomaxillary point (right and left), anterior nasal cavity width (right and left), PNCW (right and left), external maxillary width (right and left), palatal width (right and left), MMW (right and left), maxillary canine width (right and left), and posterior nasal spine (left) at T2 compared with control (P <0.05). RPE led to a significant increase in the molar inclination (right and left) compared with MARPE and controls at T2. In the long term, the PNCW (right and left) was greater in MARPE compared with RPE and controls (P <0.05).

Conclusions: Within-group comparisons showed that there was no significant asymmetry in the MARPE and control group in the short and long term. The asymmetry for the RPE group was isolated to the MMW in the short term but not observed in the long term, and the magnitude of the asymmetry was clinically not significant.