Three-Dimensional Evaluation of Midfacial Changes After Maxillary Skeletal Expander Application: A Retrospective Study.

Objective: This study aimed to investigate the skeletal and dental effects of the maxillary skeletal expander (MSE) using cone beam computed tomography (CBCT) images analyzed in the coronal zygomatic and axial palatal sections (APS). Methods: Pre- and post-expansion CBCT images of 18 subjects (10 females and 8 males) aged 12-16 years with maxillary transverse deficiency who were treated with MSE 2 were included in this retrospective study. In the coronal zygomatic section (CZS), upper interzygomatic distance and lower interzygomatic distances (LID), orbital distance (OD), alveolar distances (AD), and dental distances (DD), as well as nasal cavity width (NCW) and molar basal bone angle, were assessed. In the APS, the separation between the anterior nasal spine (ANS) and posterior nasal spine (PNS) was assessed. All measurements were performed using OnDemand3D software. Pre- and post-expansion treatment changes were compared using paired t-tests, with statistical significance set at p<0.05. Results: In the CZS, a pyramidal skeletal expansion pattern was observed, with the greatest increase in DD (R: 2.83 mm, L: 3.18 mm), followed by AD (R: 1.63 mm, L: 1.97 mm), NCW (R: 1.66 mm, L: 2.28 mm), LID (R: 1.48 mm, L: 1.92 mm), and OD (R: 0.42 mm, L: 0.56 mm). Along with greater skeletal expansion, slightly reduced dental tipping and minimal alveolar bone bending were observed. In the APS, a nearly equal separation was observed at both the ANS (R: 1.79 mm, L: 2.46 mm) and PNS (R: 1.85 mm, L: 2.49 mm), indicating a parallel split of the midpalatal suture. Furthermore, among the 36 pterygopalatine sutures examined, only three showed separation between the medial and lateral pterygoid processes. Conclusion: MSE 2 application provides more favorable skeletal outcomes reduces dentoalveolar side effects, and results in a more parallel midpalatal suture split.