Mid-Facial Skeletal and Soft Tissue Changes After Maxillary Skeletal Expander Application: A CBCT Study

Introduction: The increased resistance of midpalatal, zygomaticomaxillary and pterygopalatine sutures overtime, reduces the dentofacial orthopedic effect of conventional expanders. To adress this, mini-screw-assisted rapid palatal expanders have been created. The aim of this study was to investigate the mid-facial soft tissue changes along with rotational movements of zygomaticomaxillary complex after maxillary skeletal expander(MSE) application. Materials and Methods Pre- and post-expansion CBCT images of 17 patients(10 female,7 male) with transversal maxillary deficiency and treated with MSE 2, were enrolled in this retrospective study. Eight skeletal angular measurements were performed in the coronal and axial zygomatic sections. Besides, nineteen linear and 3 angular soft tissue measurements were investigated in the midsagittal plane. All the measuments were performed using OnDemand3D software(CyberMed Inc,Seoul,Korea). Paired-t test was used to compare the pre- and post-expansion outcomes. Results In the coronal zygomatic section, the decrease in frontoethmoidal angle and increases in frontozygomatic and zygomaticomaxillary angles revealed the outward rotation of zygomaticomaxillary comples. The increase in maxillary inclination showed the downward rotation of zygomaticomaxillary complex. The increases in frontozygomatic, frontoalveolar and frontodental angles represented greater skeletal expansion and minimal alveolar bone bending and dental tipping. The soft tissue measurements revelaed significant increase in the upper and lower face heights, alar nasal width, nasal tip protrusion, vertical filtrum height, and nasal width angle and a decrease in the facial profile angle. Conclusion Downward and outward rotation of the zygomaticomaxillary complex around the fulcrum area above the superior aspect of the frontozygomatic suture caused significant soft tissue changes in the paranal and nasal area.