Comparison of geometric changes in basal arch form after maxillary expansion between pure bone-borne and tissue-bone-borne appliance

Attaining good occlusion, a key aspect of successful treatment, relies heavily on coordinating dental arch form. Therefore, achieving a coordinated basal arch form with acceptable tooth inclination becomes imperative. In this retrospective study, our objective was to explore changes in basal arch form and discern variations in expansion patterns during maxillary transverse discrepancy (MTD) correction between two types of bone-borne expanders: the ATOZ expander and the C-expander. The center of resistance (CR) points for the maxillary and mandibular first molars, first premolars, and lateral incisors were determined from cone-beam computed tomography (CBCT) data and CR arch form analysis was performed using 25 ATOZ group and 25 C-expander group. Our findings reveal that both the ATOZ expander and the C-expander effectively expand the maxillary premolar and molar regions. Particularly noteworthy is the superior expansion achieved by the ATOZ expander in the anterior region and CR-width ratio and CR-area ratio which showed more site-specific change in basal arch form after expansion in the ATOZ group. With the utilization of CR-arch form analysis to evaluate MTD throughout the entire arch, the ATOZ expander emerges as a viable option for patients requiring customized basal arch form changes after expansion.