Evaluation of changes in maxillary shape and position after surgically assisted rapid maxillary expansion

Objective: This study aimed to examine the effects of maxillary morphology and dental arch forms on maxillary expansion during Surgically Assisted Rapid Maxillary Expansion (SARME) at dental, skeletal, and volumetric levels, and to evaluate midline ossification. Materials and Methods: In this study, male and female patients aged 18–35 years who underwent SARME at Bezmialem Vakif University Faculty of Dentistry were retrospectively evaluated. Patients with available Cone Beam Computed Tomography (CBCT) scans preoperatively and at the 6th postoperative month were included. Cases were classified into three groups according to their preoperative dental arch form: square, oval, and V-shaped. Preoperative palatal morphology and inter-incisal distance were determined, postoperative dental and skeletal expansion patterns were examined, and the amount of ossification was calculated volumetrically. All measurements were performed using Planmeca Romexis® Viewer 3D Slicer (version 5.8.1; www.slicer.org, open-access software) and Autodesk Meshmixer (version 3.5; Autodesk Inc., San Rafael, CA, USA) software. The data were analyzed using IBM SPSS Statistics 26.0. The level of significance was accepted as p<0.05 in all tests, and values smaller than 0.005 were considered highly significant. Results: Preoperative palatal depth was lowest in the square arch group (15.66±1.53 mm) and highest in the V-shaped group (19.75±1.72 mm), while the oval group was intermediate (17.36±1.69 mm) (p<0.01). The maxillary inter-incisal distance was measured as 1.26±0.47 mm in the preoperative period and did not show a significant difference between groups (p=0.70). Postoperative premaxillary volume gain was significantly greater in the square arch group (2032±710 mm3) compared to the V-shaped group (1226±802 mm3) (p=0.027), while the difference between the square and oval groups was borderline significant (p=0.062). No statistically significant difference was found among groups in terms of ossification in the premaxilla (p=0.056). Anterior midpalatal suture opening occurred at a similar level regardless of arch form (p=0.92). In contrast, in the posterior region, a tendency for greater opening was observed in the square form, but this was not statistically significant(p=0.097). On coronal sections, a distinct V-shaped opening pattern was observed postoperatively at the nasal base. In all arch groups, buccal tipping of the posterior teeth increased significantly (all p<0.05), but there was no difference among the groups in terms of the amount of tipping. In addition, a significant reduction in alveolar bone height was detected in the central incisors postoperatively (all p<0.05). Correlation analysis revealed that expansion after SARME was symmetrical between the right and left sides. Conclusion: Dental arch form and palatal depth directly affect the skeletal and dental outcomes of SARME. While premaxillary volume gain was greater in the square arch group with a shallower palate, the V-shaped arch group, despite greater palatal depth, showed limited volumetric increase. Anterior midpalatal suture opening was independent of arch form, while posterior opening tended to be greater in the square arch group. The V-shaped expansion observed at the nasal base and the symmetry of expansion between the right and left sides revealed a homogeneous expansion pattern. However, buccal tipping and alveolar bone loss were common findings in all groups. Therefore, considering arch form differences in SARME planning is essential for treatment stability and individualized approaches. Keywords: SARME, dental arch form, expansion pattern, ossification.