Sagittal and vertical effects of transverse sagittal maxillary expander (TSME) in three different malocclusion groups

Introduction: This retrospective study aimed to evaluate, by cephalometry, the skeletal and dental effects of the transverse-sagittal maxillary expander (TSME], a device created by modification of Hyrax expander and used to correct transverse and sagittal maxillary deficiencies in growing patients with Class, II, and Ill malocclusions. Materials and Methods: A total of 45 growing patients (26 females and 19 males; mean age: 8.4 years) in mixed or permanent dentition, all with bilateral crossbite, were analyzed and divided into three groups of 15 according to malocclusion type. Patients with previous orthodontic treatment or congenital/dental anomalies were excluded. Each patient was treated with the TSME, a fixed appliance derived from the Hyrax expander, equipped with one transverse and two sagittal screws. The treatment protocol included an initial phase of transverse expansion (¼ turn for trasverse screw twice a day until the desired width was achieved) followed by sagittal expansion (4% turn for sagittal screw every 15 days for 6-8 months), and 4 months of passive retention. Lateral cephalometric radiographs were taken at T0 and T1, and cephalometric measurements were statistically analyzed using paired t-tests (p< 0.05). Results: In Class | patients, a slight increase in SNA and SNB was recorded (+0.1° and +0.6°), along with a postero-inferior rotation of the palatal plane. Forward movement of the dentoalveolar process and labial tipping of incisors were detected. In Class II patients, SNB increased (+1.7°) and ANB decreased significantly (-1.36°), showing improved sagittal relationships due to mandibular advancement. In Class III patients, SNA increased and SNB decreased [+0.87° and -1.50°), with a significant rise in ANB (+2.37°), and improvement in sagittal discrepancy, with maxillary advancement and clockwise mandibular rotation. In all groups, a significant increase in SNP-A, |*SN, and I° FH was observed, indicating forward movement of the maxillary dentoalveolar process and proclination of the incisors, while anterior and posterior vertical dimensions {N-Me, S5-Go) did not show significant changes. Conclusions: Based on these findings, it can be concluded that the TSME produces favorable skeletal and dental modifications in all three skeletal classes, in both the transverse and sagittal planes, improving intermaxillary relationships. The appliance represents a valid option for early treatment of malocclusions associated with maxillary hypoplasia, achieving positive sagittal effects without significant adverse impact on vertical dimensions.