Effect of modified tandem traction bow appliance on airway size

Objective: To investigate the effect of modified tandem traction bow appliances (MTTBA) on pharyngeal airway dimensions in Class III malocclusion treatment. Materials and Method: The material of this study consisted of pre-treatment (T1) and post-treatment (T2) lateral cephalometric radiographs of 20 subjects with skeletal and dental Class III malocclusion (8 females and 12 males; mean chronologic age; 10 years and 1 month) who had been treated with the MTTBA appliance. Elastics that exerted a force of 400-500 g were worn between the upper splint and the traction bow with an angle of 35-40°. The average treatment time was 12 months. Linear and area measurements were done to determine the pharyngeal airway dimensions. Kolmogorov-Smirnov and paired t-tests were used for the statistical analysis, and p<0.05 was considered as statistically significant. Results: Treatment changes indicated significant forward-movement of the maxilla (p<0.001) and significant increases in effective lengths of the maxilla and the mandible (p<0.001). The mandible showed a clockwise rotation because of the increase in mandibular plane angle (p<0.001). A significant increase in the oropharyngeal area (OA; p<0.05), and an insignificant increase in the nasopharyngeal area (NA) was found. Hyoid bone moved anterior and inferior insignificantly. Conclusion: A favorable improvement was observed in the oropharyngeal area by the MTTBA appliance that was used in the treatment of Class III malocclusion