Midfacial changes in the coronal plane induced by microimplant-supported skeletal expander, studied with cone-beam computed tomography images

Introduction: Our objectives were to evaluate midfacial skeletal changes in the coronal plane and the implications of circummaxillary sutures and to localize the center of rotation for the zygomaticomaxillary complex after therapy with a bone-anchored maxillary expander, using high-resolution cone-beam computed tomography. Methods: Fifteen subjects with a mean age of 17.2 +/- 4.2 years were treated with a bone-anchored maxillary expander. Pretreatment and posttreatment cone-beam computed tomography images were superimposed and examined for comparison. Results: Upper interzygomatic distance increased by 0.5 mm, lower interzygomatic distance increased by 4.6 mm, frontozygomatic angles increased by 2.5 degrees and 2.9 degrees (right and left sides), maxillary inclinations increased by 2.0 degrees and 2.5 degrees (right and left sides), and intermolar distance increased by 8.3 mm (P<0.05). Changes in frontoethmoidal, zygomaticomaxillary, and molar basal bone angles were negligible (P>0.05). Conclusions: A significant lateral displacement of the zygomaticomaxillary complex occurred in late adolescent patients treated with a bone-anchored maxillary expander. The zygomatic bone tended to rotate outward along with the maxilla with a common center of rotation located near the superior aspect of the frontozygomatic suture. Dental tipping of the molars was negligible during treatment.