Dentoalveolar, skeletal, pharyngeal airway, cervical posture, hyoid bone position, and soft palate changes with Myobrace and Twin-block: a retrospective study

BACKGROUND: The primary aim of this study was to evaluate the dentoalveolar, skeletal, pharyngeal airway, cervical posture, hyoid bone position, and soft palate effects of the Myobrace and Twin-block appliances. The second was to compare them in terms of ease of use by assessing the factors that may influence patient compliance. METHODS: The study included thirty-six Class II division 1 patients (19 females, 17 males; mean age, 12.14 ± 1.23) who had previously been treated in the Orthodontic Clinic at Sivas Cumhuriyet University Faculty of Dentistry. The patients were divided into two groups: Group 1: Myobrace (n = 18), and Group 2: twin block (n = 18). The effects of the appliances on the skeletal, dentoalveolar, soft tissue, craniocervical, and other anatomic structures were assessed using 46 measurements (22 linear and 24 angular), on pre and post-treatment cephalometric radiographs. AudaxCeph 5.0 software (Ljubljana, Slovenia) was used for the analysis. To analyze the changes after one year of treatment, a paired sample t-test and Wilcoxon signed-rank test were used. Intergroup comparison was performed using the Student t-test and the Mann–Whitney U test. RESULTS: In the Myobrace and Twin-block groups, there was a significant increase in SNB (°) (p = 0.004, p = 0.001), IMPA (°) (p = 0.005, p = 0.001) and a significant drop in U1/SN (°) (p = 0.021, p = 0.005). The lengths of Cd–Gn (mm), Go–Pg (mm), and Cd–Go (mm) increased significantly in the Twin-block group (p = 0.003, p = 0.010, p = 0.001), whereas the Myobrace group did not change. Similarly, there was no significant difference in pharyngeal and soft palate measurements in the Myobrace group but a statistically significant decrease in SP length and angle in the Twin-block group (p = 0.001, p = 0.006). Increases in SN/OPT (°) (p = 0.032, p = 0.001) and SN/CVT (°) (p = 0.012, p = 0.001) were statistically significant in both groups. Myobrace was more difficult to use while sleeping, whereas the twin block caused more nausea. CONCLUSIONS: Both appliances can be used for mandibular advancement. The Twin-block appliance, on the other hand, was more effective and patient-friendly. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12903-023-02773-x.