CEPHALOMETRIC ASSESSMENT OF TRANSVERSE CHANGES IN FRONTO-ORBITAL AND ZYGOMATIC WIDTH BEFORE AND AFTER RAPID MAXILLARY EXPANSION IN PATIENTS WITH UNILATERAL POSTERIOR CROSSBITE

Abstract

Rapid maxillary expansion (RME) is commonly used for the correction of transverse maxillary deficiency associated with posterior crossbite. Although its primary effect is directed toward the maxilla and the midpalatal suture, expansion forces may also induce measurable changes in the circummaxillary and zygomatic regions. The aim of the present study was to evaluate transverse changes in the zygomatic and frontozygomatic regions following RME in patients with unilateral posterior crossbite using posteroanterior cephalometric measurements. A three-year prospective clinical study included 47 patients with clinically diagnosed unilateral posterior crossbite and incomplete craniofacial growth, all treated with a tooth-borne Hyrax rapid maxillary expander. The sample consisted of 18 males (38.3%) and 29 females (61.7%), with a mean age of 16.59 ± 1.89 years. Digital posteroanterior cephalograms were obtained at the diagnostic stage and immediately before removal of the RME appliance. Zygomatic width was assessed as the linear distance between the bilateral Za landmarks (Za–Za), while the transverse dimension of the frontozygomatic region was evaluated as the distance between the bilateral Zmf landmarks (Zmf–Zmf). Pre- and post-treatment values were compared using a paired-samples t-test, and the relationship between the changes in the two parameters was assessed by Pearson correlation analysis. Mean Za–Za increased from 112.91 ± 12.52 mm before RME to 114.42 ± 12.43 mm after treatment, corresponding to a mean increase of 1.51 mm (p < 0.001). Mean Zmf–Zmf increased from 85.71 ± 10.73 mm to 86.62 ± 10.98 mm, with a mean change of 0.91 mm (p < 0.001). A significant positive correlation was found between the changes in Za–Za and Zmf–Zmf (r = 0.582, p < 0.001). The findings indicate that tooth-borne RME with a Hyrax appliance in patients with unilateral posterior crossbite is associated with statistically significant transverse changes not only in zygomatic width but also in the frontozygomatic region. These results suggest that the effects of conventional RME may extend beyond the immediate maxillary structures and may involve measurable, although limited, adaptation of more lateral and cranially located components of the midfacial complex.