Objective: This study aimed to evaluate the effects of two bone-borne maxillary expansion appliances on cranial and circum-maxillary sutures using cone-beam computed tomography (CBCT), before and after maxillary transverse expansion treatments.
Methods: A total of 81 patients (females=58, males=23) were treated with either a C-expander (CEXP group, N=44) or an ATOZ expander (ATOZ group, N=37). CBCT images were taken before (T0) and after (T1) maxillary expansion, and the widths of 10 circummaxillary sutures were measured in sagittal, coronal, and axial planes. The Wilcoxon rank-sum test was used to compare the changes in suture width between the CEXP and ATOZ groups, with statistical significance defined as a P-value >0.05.
Results: In both the ATOZ and CEXP groups, the widths of the frontonasal, frontomaxillary, pterygomaxillary, nasomaxillary, internasal, intermaxillary, and midpalatal sutures significantly increased after maxillary expansion (P<0.05). In the CEXP group, the frontozygomatic, zygomaticomaxillary, and temporozygomatic suture widths decreased (P<0.05), while in the ATOZ group, the frontozygomatic suture width increased slightly (P<0.05). Significant differences between the two groups were observed in the width change of the frontozygomatic, zygomaticomaxillary, temporozygomatic, pterygomaxillary, internasal, intermaxillary, and midpalatal sutures (P<0.05).
Conclusions: Both C- and the ATOZ expanders caused the widening of the bone sutures in the nasalzygomatic- maxillary area. The C-expander decreased suture width in the circumscribed zygomatic area, whereas the ATOZ expander increased the width of the frontozygomatic suture with no effect on other bone sutures.

Keywords: CT, Expansion, C-expander, ATOZ expander